r-HrSiCA i Sci.LiB. TN 24 C3 M> N0.89 C.2 ■ROLEUM RES% CALIFC WITH SPECtM, REFERENCE TO ^mm iiililili illl CALIFORNIA STATB MI|j FERRY BIJILDlbilG - SAn"' ll«rtl»«!HM«M!uMmiHH!« !i!llll!il!|!U!111!l!: i^AXyi-^ ' ^ CALIFORNIA STATE MINING BUREAU FERRY BUILDING, SAN FRANCISCO FLETCHER HAMILTON State Mineralogist San Francisco] BULLETIN No. 89 [July, 1921 PETROLEUM RESOURCES OE CALIEORNIA With Special Reference to Unproved Areas BY LAWRENCE VANDER LECK CiJ.IFORNIA STATE PRINTING OFFICE SACRAMENTO 13322 TABLE OF CONTENTS. Chapter I. Paaes GENERAL THEORY OF THE ORIGIN AND ACCUMULATION OF OIL IN CALIFORNIA. Organic theory of origin. Organic shales. Migration and accumulation. Theories as to accumulation. Reservoirs. Saturation and recovery. Areas of accumulation. Summary of the conditions necessary for the accumulation of oil in commercial quantities in California. Surface indications of oil 13-22 Chapter II. DESCRIPTION OF THE OIL BEARING FORMATIONS IN CALIFORNIA. General geology and structure of the State. Coast Ranges. Great Central "Valley. Lava beds of the nortliwest region. Sierra Nevada. Southwest Desert Region. Faults. Non-oil bearing formations. Oil bearing formations. Cretaceous Eocene. Oligocene. Miocene. Pliocene. Description of correla- tion table . 23-34 Chapter III. POSSIBILITIES OF OIL IN THE COAST AREA NORTH OF THE BAY OP SAN FRANCSCO, (Includes the counties of Marin, Sonoma, Mendocino, Humboldt, Del Norte and Trinity.) Marin County. Point Reyes peninsula. Bolinas. Sonoma County. Wells on the Ducker Rancli. Mendocino County. General Geology. Point Arena District. Humboldt County. General Geology. District of the Mattole River. Wells drilled. Del Norte and Trinity counties. General Geology — 35-44 Chapter IV. OIL POSSIBILITIES OF NORTHWESTERN CALIFORNIA. (Consists of the counties of Siskiyou, Modoc. Shasta and Lassen.) Descrip- tion of the geological formations and oil possibilities of Siskiyou, Modoc, Shasta and Lassen counties 45-47 Chapter V. AREA OF THE SIERRA NEVADA MOUNTAINS. (Consists of the following counties: Plumas, Sierra, eastern part of Butte County, eastern part of Yuba County, Nevada, eastern part of Placer, El Dorado, Amador, Alpine, Calaveras, Tuolumne, Mariposa, eastern part of Madera, eastern part of Fresno and Tulare counties, and that part of Kern County that lies in the Sierras.) Description of the geology and oil possi- bilities of this region 48 Chapter VI. AREA OF THE SACRAMENTO VALLEY, INCLUDING THE EAST SLOPE OF THE COAST RANGES, AND THE FOOTHILLS OF THE SIERRA NEVADA. (Consists of the counties of Tehama, Glenn, western Butte, Yuba, Sutter, Colusa. Lake, Yolo, Napa. Solano, western Placer and Sacramento.) West side of the Valley and east slope of the Coast ranges. Topography. Geology. Indications of petroleum. Structure. Oil possibilities. Wells drilled. District of the Valley floor. Hooker Hills. Marysville Buttes. Montezuma Hills. Wells drilled. East side of the Valley and foothills of the Sierra Nevada. General geology. Tuscan Springs 49-59 CALIFORNIA STATE MINING BUREAU. Chapter VII. Pages AREA OF THE CO.\ST RANGES FROM SAN FRANCISCO BAY AS FAR SOUTH AS THE PAJARO RIVER. (Includes the counties of Contra Costa, Alameda, San Francisco, San Mateo, Santa Clara and Santa Cruz.) Contra Costa County, Mount Diablo area. Seep- ages and wells drilled. San Pablo Valley. Geology. Wells drilled. Arnold's report. San Francisco County. San Mateo County. General Geology. Seepages and wells drilled near Half Moon Bay, Santa Clara County. General Geology. Moody Gulch, Los Gatos District. Sargent Oil Field. Santa Cruz County. General Geology. Seepages and wells drilled north of Watsonville.. 60-68 Chapter VIII. COAST RANGES FROM THE PA.IARO RIVER AS FAR SOUTH AS THE SANTA M.ARI.V RIVER. (Includes the counties of San Benito, Monterey and San Luis Obispo.) San Benito County, area around HoUister. Tres Pinos. San Benito and Santa Ana valleys. Vallecitos District. Anderson and Pack's report. Southwestern portion of the county. Packs and English's report on the Bellerwater and Peachtree valleys. Wells drilled. Monterey County. Mouth of the Salinas Vall«y. Santa Lucia Mountains. Arroyo Seco District. Seepages. Gavilan Mountains. Salinas Valley from Salinas to Greenfield. San Antonio Hills. Seepages. Fleyto District. English's report. Salinas Valley from Greenfield south to the county line. Bradley anticline. Wells drilled. English's report on San Ardo District. Area east of the Salinas Valley. Parkfleld District. Pack and English's report. Wells drilled. San Luis Obispo County. General geology of northern portion. Arroyo Grande Oil Field. Huasna District. Carrisa Plains and San Juan Creek. Arnold and Johnson's report ., 69-101 Chapter IX. COAST AREA FROM SANTA MARIA TO THE SANTA MONICA MOUN- TAINS. (Includes the counties of Santa Barbara. Ventura, and northwestern Los Angeles.) Santa Barbara County. Topography. Proven fields and adjoining areas. Casmalia Field. Santa Maria Field. Cat Canyon Field. Purisima Hills. Lompoc Field. Santa Ynez and San Rafael mountains. Cuyama Valley. English's report. Coast area. Summerland and Rincon districts. Arnold's report. Ventura County. Northern lialf of the county. Ojai Valley fields. Santa Paula Field. Ventura Field. South Mountain and Oak Ridge. Montebello. Bardsdale, Sespe Canyon. Piru Field. Tony and Eureka canyons. Simi Valley. Topo Canyon. Brea Canyon. Unproven areas in the Simi Valley. Lower end of Simi Valley. Santa Monica Mountains. Conejo Field, northwestern Los Angeles County. General geology. Newhall District 102-130 Chapter X. SOUTHERN LOS ANGELES AND ORANGE COUNTY. Santa Monica Mountains. San Fernando Valley Coastal plane of Los Angeles and Orange counties. Lines of structure. Proven fields. Salt Lake. Los Angeles City. Montebello. Whittier, Brea Canyon and Olinda, Richfield. Coyote Hills. Santa Fe Springs. Newport. Huntington Beach. Signal Hill. Inglewood. Beverly Hills. San Pedro. Redondo District. San Gab- riel Valley. Puente Hills. San Jo.se Hills. Eastern portion of Orange County. Santa .\na Mountains. Laguna Hills and Capistrano District 131-143 CHAPTHai XI. SAN DIEGO .\ND IMPERIAL COITNTIES. San Diego County. General geology of mountain area. Coastal district. Geology and oil possibilities of region north of Del Mar. Wells drilled. Geology and oil po.ssibilities of region south of Del Mar. Wells drilled. Kerr's report. Imperial County. General geology and oil possibilities. Kerr's report. Wells drilled 145-152 PETROLEUM RESOURCES OF CALIFORNIA. 5 Chapter XII. THE DESERT REGION. rag.s (Includes the counties of Riverside, San Bernardino, northeastern Los Angeles, eastern Kern, Inyo and Mono.) General geology and topography of this region. Mono County. Geology and wells drilled at Mono Liike. Eastern Kern County. Mohave Desert. Antelope Valley. North- eastern Los Angeles County. San Bernardino County. Barstow-Kraemer region. Pack's report. District lying west of San Bernardino Mountains. Chino Hills. Riverside County. General geology. Wells drilled. Oil possi- bilities -- '. 153-161 Chapter XIII. REGION OF THE SAN JOAQUIN VALLEY. (Includes the counties of San Joaquin, Stanislaus, Merced, western one- third of Madera, the western two-thirds of Fresno, Kings, the western half of Tulare and Kern.) General geology of the Valley. Structure, buried structures. Region of the proven tields. Midway. Sunset. McKittrick. Bel- ridge. Ix)st Hills. Devils Den. Elk Hills, ("oalinga. Kern River. Unproven areas. Soutli end of the Valley. Foothills of tlie temblor. Kettleman Hills. Kreyenhagen Hills. Region north of Coalinga. Tulare Lake. Buttonwillow. East side of the Valley 163-179 CALIFORNIA STATE MINING BUREAU. FIGURES. Pa«e Frontispiece 8 Fig. 1. Different Types of Structure Common to the Oil Fields 15 Fig. 2. Methods of Accumulation in Various Types of Structures Found in California Fields -- 17 Sec. 1 — East-west section across the Midway District, Kern County, showing accumulation on a monocline, syncline and anticline. Sec. 2 — Shows accumulation on an anticlinal fold in the Santa Maria Field, Santa Barbara County. Sec. 3 — North-south section across Salt Lake Field, Los Angeles County, showing accumulation along a fault zone. Fig. 3. East-west section across the Point Reyes Peninsula, about two miles north of Bolinas, Marin County — 37 Fig. 4. East-west sections across western side of the Sacramento "Valley 53 Fig. 5. Section up Moody Gulch, Santa Clara County 65 Fig. 6. Sec. A-B — East-west section across the San Benito and Tres Finos valleys, through town of Tres Pinos, San Benito County 70 Sec. C-D — North-south 'section across the Vallecitos District, San Benito County. Sec. E-F — East-west section across Lewis Creek and the Peachtree Valley in vicinity of Lonoak, Monterey County. Fig. 7. Sec. A-B — North-south section across Sulphur Mountain and Ojai Valley, in vicinity of Upper Ojai fields, Ventura County 114 Sec. C-D — North-south section across the Simi Valley, Ventura County, in the vicinity of Simi. Fig. 8. North-south section through the Conejo Field, Ventura County 128 P'ig. 9. Sec. A-B — Generalized section across Coastal plain area of Orange County, showing three general lines of structure along which oil has accumulated -- 134 Fig. 10. Sec. A-B — From Laguna to Santa Ana Mountains, across the Laguna Hills and the Capistrano Valley, Orange County 144 Fig. 11. Sec. A-B — East-west section along the north side of Santa Margarita Valley, San Diego County 147 Sec. C-D — East-west section through La Jolla, San Diego County. Fig. 12. Hypothetical sections across San Joaquin Valley 165 Sec. A-B — Shows possible accumulation in region north of Coalinga. Sec. C-D — Shows proven fields and possible accumulation in region of Tulare Lake. PHOTOGRAPHS. Elk Hills Field, Kern County 169 Huntington Beach Field, Orange County 139 Midway Oil Field, Kern County 175 Montebello Field, Los Angeles County — 132 Oak Ridge Anticline, Ventura County 112 Richfield Field, Orange County 137 PLATES IN POCKET. Map of California. Correlation table. Point Arena. Humboldt County. West side of Sacramento Valley. Imperial County. Plate I. Plate II. Plate III. Plate IV. Plate V. Plate VL LETTER OF TRANSMITTAL. To His Excellency, the Honor^^ble William D. Stephens, Governor of the State of Calif arnia. Sir: — I have the honor to herewith transmit Bulletin No. 89 of the State Mining Bureau, relating to the Petroleum Resources of California. The increasing demand for petroleum and its products, and the inability of production to keep pace with requirements, for several years, have resulted in widespread prospecting throughout the world for pos- sible new oil fields. In California, 'wild-cat' wells are being drilled in many localities, some of them in places where even a cursory inspection of the geology would tell of the futility of looking for oil. For this reason, the report herein aims to furnish information as to the unfavor- able as well as to the favorable areas for development of additional petroleum resources in California. Respectfully submitted. Fletcher Hamilton, State Mineralogist. July 21, 1921. N CALIFORNIA STATE MINING BUREAU- FLETCHER HAMILTON- STATE MINEBALOCIST OUTLINE MAP Of SI S K I Y U I M I CALIFORNIA ^ ^^.-^- -zi ""•"§'^7 SHASTA Itrini ! L A S S t H I ^■" Index Map showinof Areas discussed in Various Chapters . AREA CHAPTER fMCNOOClNOj ,! :',5'^i>«»»H _/ I) ®a»i.i. Ii \,-' k rv i Lt N N''BUT1 E "-^.^stetRRA I ^ °oJ,.,i Y H-.*''*?--"' ®-i""-^i..r.?' VSONOMA XVILLC i^^"'" .X"i«=i>.„ 54NJ0igiJl«V /TUOLUMNE S'0_..X .MCScoSJ^X^^ /,;— ,\mar,posa /r)V- - -S '-"^ -^^ * ^ ' - •"■'•- \ 1 m z E 3 Y 4 Ta 5 Yir & vm 1 K 8 X 9 XI 10 xn II xm 82,970 2,122,000 25,610 14.7 49.3 13.4 14.9 Santa Barbara — Ventura - -- 5.7 2.0 4,319,950 105,720,310 • From the Sixth Annual Report of the State Oil and Gas Supervisor. Vol. 6. No. 7. Jan., 1921. Exploration has opened up new fields within these districts, increasing the production of the state twenty-four fold, yet it has failed to add a single noteworthy field outside their boundaries. The principal conclusion to be drawn from this report is similar to that shown b}' the table. An examination of the state indicates that no field of any appreciable size will ])e discovered outside the two present general areas of production. These two districts are the San Joaquin Valley and the Coast from the Santa Maria River south to the Santa Ana River. In the San Joaquin the most promising territory for development lies along the west side of the valley. In the Coast area it consists of that portion of Los Angeles and Orange counties lying between Santa Monica and Newport and south of the San Gabriel Valley. It is also evident that oil in appreciable quantities is confined to porous sedimentary rocks of the Tertiary period, which are associated with bodies of organic shale of marine origin. The greater portion of the yield comes from beds of Miocene and Pliocene age. The Cretaceous, which is the principal sedimentary formation exposed in northern California, .shows numerous seepages. It is believed, how- ever, that it will not produce sufficient oil to be of any great commercial importance. Those fields which were plainly visible to the geologist and prospector have now been opened up to development work. New fields in the future will only be found by detailed study of the geology and topography of the state. statistics for 1920, Total production (barrels) 105,720,310 Total proven acreage (acres) ' 91*319 Total number of wells producing IIII 9*042 Average production, per day, per well (barrels) * 35 PETROLEUM RESOURCES OF CALIFORNIA. 1 o CHAPTER I. General Theory of the Origin and Accumulation of Oil in California. Organic Theory of Origin. The generally accei)ted theory ainoii"; iieologists as to the origin of petroleum in California, is that which assigns to it an organic soifrce. According to this theory petroleum is the result of the slow decomposi- tion and (listiMatidn of animal and vegetal matter at a low temperature, without a sut'ticieiit supply i»f oxygen. The I'csult of this chemical reac- tion is the formation of li(|ui(l liydrocai'bons. known as ix'troleum, or mineral oil. Assuminii that the above theorx- as to origin is cori'eet, it follows that oil in California nnist necessarily have been fornu'd in sedimentary rocks and in particular in those sedimentary rocks which contained organic material in ap|)recial)le quantities. An investigation of the geological format ion.s of the state indicates that such deposits of organic nuiterial are present in renmrkable quan- tities; ranging in the geological column from the Cretaceous to the Pliocene and commonly known as 'organic shales.' Further, it can be definitely stated that all hnown deposits of petroleum in Calif oniia are fouiul //( dose association u'itli these organic slialcs, cither in or above than. Organic Shales. The organic shales were originally marine deposits of fine silt, miiiijled with the remains of diatoms, foraminifera and various other forms of sea life. Diatoms are a low, minute form of plant life or alga^, having a frame- work of silica. Under the microscope they appear as round dots in the shale and vary in size from 0.1 mn. to 1 nuL and apparently form the bulk of the shale. An analysis of various samples of California oil shale shows that they vary from 65 per cent to 85 per cent silica. In view of these facts it has l)een assumed that these diatoms are the chief .source of the California oil. After the diatoms, the ne.xt most al)undant organisms are foramini- fera, an animal organism, with a hard calcareous yhell, generally about 2 mn. in length. In addition the shales contain numerous sponge spicules, fish scales and impiessions of seaweed. The diatom and foraminifera lived at the surface of warm inland seas, such as were present in what is now the great valley and coast regions of California, during the various geological ages from the Cretaceous to the present. These organisms dying, dropped to the bottom of the seas and together with other plant and animal matter formed an ooze or organic mud. Then, due to the low temperature and absence of oxygen in (piantities, a very slow decomposition, or putrifica- tion of the organic parts, took place. It is, however, believed that no great quantity of liquid hydrocarbons were formed at this stage. These are believed to have been formed when, due to earth movements, the 14 CALIFORNIA STATE MINING BUREAU. mud or ooze was uplifted above the surface of the sea and by reason of the heat and pressure due to these movements and possibly aided by the action of saline waters, distillation of the shale took place, which resulted in the formation of petroleum. In general these organic shales are fine grained and compact in texture ; light in weight ; ranging in color from chocolate-brown, purple and maroon to light gray and white. They vary from the pure soft earthy, 'chalky' variety, to hard flinty porcelaneous varieties. Migration and Accumulation. The petroleum thus formed in the organic shales was probably present at first in minute quantities throughout the shale. It is next necessary to account for its concentration and accumulation in pools such as now exist in the California fields. To explain these concentrations in pools it will be necessary to assume that the oil migrated from the shales in which it formed to the porous reservoirs where it is now found, these reservoirs in practically all cases being porous sands either in the shales or directly above them. Whereas the origin of the petroleum from the organic shale may be readily explained, the force that caused the migration and accumulation of the oil is not as yet clearly under- stood. All that is certain is that the oil has migrated and accumulated in pools along certain geological structures, and while no oil in commer- cial quantities has been found except along these structures, no facts that will fit all existing conditions have been found to explain the reason for the accumulation. Before giving a review of some of the theories for accumulation it would be well to describe briefly the typical geological structure wherein the oil in California is found. The contraction of the earth's surface has caused folding in the rocks that form its crust. There are several different kinds of folds. (See Fig. 1, page 15.) When the strata are domed up in an arch the structure is known as an anticline. The trough corresponding to this arch is known as a syncline. When the strata have been tilted in one direction only the structure is known as a monocline. When the apex of an anticline or cyncline ceases to be horizontal it is said to plunge, and similarly when the axis is inclined from the vertical the fold is said to be assymetrical. When forces of compression have caused the strata to break and slip along a definite line, faulting takes place. When a later formation is deposited upon the tilted or eroded surface of an earlier formation, this is called an unconformity. Theories as to Accumulation. (1) Anticlinal Theory. This theory assumes that oil being of a less specific gravity than water rises above the water present in the porous rocks and collects in the highest possible point in an upward fold. The factors necessary for this hypothesis are, (a) saturation of the sand with oil, gas and water; (b) folding; (c) porous beds between impervious beds. Oil accumulating in this manner must overcome the friction of the grains of the porous rocks and the molecular repulsion of oil and water. The forces in favor would be difference in gravity of the oil and water and the inclination or dip of the strata. PETROLEUM RESOURCES OF CALIFORNIA. 15 I UJ O o o H en o o o en ff/Jf ^ > - o ^ s/xy- IxJ —I O \— < o 00 o '_J £ o LU d o a a o O 3 rjl ft d u M fa 16 CAIilFORNTA STATE MINING BUREAU. (2) A second theory is that moving waters were the direct agent for tlie accunndation. That is, that the force that caused the niigration was due either to hydraulic or capillai-y jii-essurc. Neither of the abuve theories, however, is sunieicnl to e\i)lain the enormous gas pressure which is fouiul in California fields and which in nearly all cases is greater Ihaii that wliicli could be developed by any hydrostatic pressure. Xor do they explain why, when the forces that caused the original migration are no longer active, the oil does not move back over the l)ath it once traveled. (3) A theory whicli has recently been advanced ])y ^larcel Daly' called the "diastrophic theory," attributes Ihe migration to lateral , pressure caused by the deformation of the earth crust. The forces of i compression due to earth movements, he believes, have transferred their , effects not only to the solitl matei'ial of the eai-lli's cnisl l)ut to the tli(piids contaiiu'd in the porous beds as well. ■; It is very probable that all of the above theories contain some element iof truth, and the forces that contributed to the migration nuiy possibly 'be a combination of all of these forces. That is, a li(iuid composed in ■parts of oil and water, due both to hydrostatic pressure and compression . from earth movements, was forced to migrate along planes of fracture and unconformities till it was trapped in the highest parts of anticlinal ■ folds. Having once entered the fold a gradual separation of the oil, gas and water took place due to the dilference in specific gravity of these substances. The pressure over and above that whicli is due to hydrostatic forces may be due to a combination of further earth move- ments which compressed the strata in which the oil was trapped, and to chemical reactions between the hydrocarbons and saline waters, which liberated new gases. It is necessary also to further assume that once the oil entered the fold that the various points of entrance gradually became sealed due to the cementation of the porous sand by mineral bearing waters and tar. However, regardless of what may have been the forces that caused accunndation, it can be definitely stated that all oil in commercial quantities in California is found in one oi- the other of the following geological structures : (1) Along the crests of anticlinal folds and domes, such as are typified by the Buena Vista Hills and Elk Hills in the Midway, and the ^loute- bello Hills and Coyote Hills in Southern California. (2) In the upper i)art of i)lunging synclines, which are closely associated with i)roductive anticlines. The Coalinga syucline is a type of this kind of a pool. (3) Along the upper portions of monoclines and ti-uncated anticlines lying along the foothills, which are undei- the influence of anticlinal domes farther out in the valley. This ty])e of accumulation has examples in the West Side field at Coalinga, the west portion of the Midway field, and possibly the Kei'ii River field. (4) Along the zone of fracture and in upward folds influenced by faulting. Portions of the Salt Tiake field near Los Angeles and some portions of the Puente Hills field are examples of this type. (See Fig 2, page 17.) ^ Daly, Marcel. The Diastrophic Theory. Am. Inst. Min. Eng. Bull. 115. PETROLEUM RESOURCES OF CALIFORNIA. 17 I UJ ^ iniifi S II II III X Ml'iiN II nil jiiii.i I III 11 1 1 iii'h ; I ; ///;;■;/■ 1 o1J)"u,/-//| ll'(f:\.l m I ll:i:ri:ll CO .Ml l.i:if|:; . MM,M.| :Jlll:UTI n I ri.i p '■' I 00 'i.iri (II I'll il ru '.(,/, Iini-ii[\ i,Mr/\ 1,1 II I.' iV.VVI I'l iir.i.v II n.M' l^i ri;i ivi:i:i:^ iT.lil l'l:'n lll.l i:i,i:i:i 1:1 l-i;i.'!ii:l:r ti:i':i-m[i, l-'^U ' i; a' I ':m'|'i','/'7, pi I.I. I'll imi' ,':'■/■/■ m '■i:l:l m ■ms^ A^Va _ m //•/ ;■;.■; — ui'rn-i (i^iMi:, 'nnl :i:W!m 'M I A^ ^Xyz-y- vD l'';l;ll!i i*Mi|:l I" mi I ^1 I'i'iii .&s« ilMis ^ c auoj o ^/laj +J o (U 0) :N^; .2 x^ 1 0) 'O -1-t 1 r^ 0) a "^ a '3 g -a a o e3 rt C4-4 ^-' a> (U a -« a • » TS 3 at "Z af ■"^ , 3 ^N a o c 0-- T" ■CO >^ — j: a ^^ o -i< - ^ ?'-'~ i z. = • ^ ►-I ■- ^^ X c P • ■ — ' . ■" a .S a • a o 01 „ Ol 0) 5t CO JZ2 2—13322 18 CALIFORNIA STATE MINING BUREAU. In general those fields along the crests of anticlines or domes have produced the largest wells while those along fault zones the smallest. Fields situated along low-dipping monoclines are the longest lived and show the least rate of decline. It has been assumed that oil travels laterally and vertically — never downward — and tlie locations of all known pools in California appear to bear out this assumption : except in possibly the uppermost sandstone of the fornuition directly below an organic shale bed, no oil has been found in formations stratigraphically below a known bed of organic shale. In certain eases oil has been found in formations which are geologically older than the organic shale which is present in that locality, but in such cases its presence may be readily explained by the fact that faulting has brought the older formation into a strati- graphic position above the organic shale—a reversal of their normal position. The reason for the failure of the oil to migrate downward ha.s been attributed to the facts that the porous sedimentary rocks of the oil field are saturated with water, and the difference in specific gravity of the oil and water has forced the oil upward. Similarly should the porous rocks not contain water, the oil by reason of gravity should migrate downward. Lateral migration has probably taken place along planes of uncon- formities, and porous beds ; and vertical migration, along faults, cracks or fractures and porous beds. Reservoirs. Reservoirs are the series of beds in which the oil collects along various geological structures described in the preceding paragraphs. As previously stated these beds are either in the organic shale formation, or directly above it. When found in the shales, the reservoir beds are either very fine grained sands, or hard, flinty beds of shale which have become fractured and broken, allowing the oil to collect in the voids between the fractured particles of the .silicious shale. These two cases are typified by the fine sands in the so-called 'brown shale' of the Belridge and Lost Hills fields, and in the fractured flinty zone, near the base of the diatomaceous shale in the Santa Maria field. In the majority of cases, however, the oil has collected in the sand- stone beds overlying the organic shale. The lithology of these beds is a very important consideration in the accumulation of the oil. First, the beds must be porous enough to absorb the oil in appreciable quantities. The porosity is not dependent upon the size of the grains, but rather on the shape ; regularity in size ; and arrangement. A fine- grained sand composed of spherical grains all of one size and arranged in a regular manner, will have greater porosity, than a coarse-grained sand in which the grains are irregular and flat, so that they may be fitted tightly together, thus reducing the porosity. The size of the grains afit'ect the character of the oil. In general, fine-grained sands contain the light oil, while coarse sands contain the heavy viscous oil. This difference in the character of the oil is due to the fact that the light oil will move readily through and collect in the fine-grained sand, PETROLEUM RESOURCES OP CALIFORNIA. 19 whereas the thick viseous oils are too tarry to move freely except in coarse sands. The so-called shale oil zone on Twenty -five Hill, west of Taft, and the deep 'shale oil zones' of the Belridge field are examples of this differentiation due to the size of the grains. Second, there must be a difference of porosity in the different beds that make up the reservoir. There must be a porous bed between two impervious beds. Otherwise the oil would not tend to concentrate in certain beds, but would be disseminated throughout the reservoir, in such a lean saturation that extraction in commercial quantities by means of wells would be impossible. The Arroyo Grande field is a good example of lean saturation. In this case, the oil has collected in the Pismo formation, which in this particular locality- contains no impervious shale beds, but is entirely made up of sand. Tlie result is that the oil has disseminated throughout the entire lUOO feet or more of the Pismo formation, in such lean satura- tion, that it is difhcult to obtain wells that are commercial producers, although tliere is enough oil present if concentrated in smaller beds to produce oil in commercial ([uantities. Third, the relationship in geological time between the source and the reservoir has an important bearing upon the accumulation. If there is too great a time interval between the age of the beds in which the oil formed and those which nuike up the reservoir, one can not expect the reservoir to contain oil, although all other conditions may be favorable. The reason for this is obvious. If there was an opportunity for the organic shales to be uplifted and eroded before the deposition of the reservoir formation, the oil content of the organic shale would run out and be lost, before an opportunity was afforded for the collection of the oil in the reservoir. In some cases after the reservoir formation has been deposited and the oil collected therein, there has been an erosive time interval, in which the reservoir and its oil content were eroded away. Subsequently the organic shales were again lowered beneath the surface of the sea and a second reservoir formation was deposited. This in time was uplifted and folded. In this ease there would be little or no oil in the second reser- voir, as the greater part of the oil content of the organic shales had collected in the first reservoir and was lost in the erosive time interval. An example of this is found in the Pleyto district on the west side of the Salinas Valley. Here the ^Monterey shale (Lower Miocene) and the Paso Robles sands (Upper Pliocene) are folded in an anticline, yet there is no appreciable ainount of oil in tlie Paso Robles, although the general conditions for accnnnilation are favorable. It is probable that this failure is due to the great time interval between the ^Monterey shale and the Paso Robles formation. Saturation and Recovery. The capacity of oil sands and the amount of oil recoverable are two important considerations in determiniug the value of a prospective field. It has been estimated by J. 0. Lewis' that the average porosity for California sands is about 25 per cent of their volume, provided they are completely saturated. Using this porosity, Lewis has estimated » Lewis, J. O. Bull. 148. U. S. Bureau of Mines. 20 CALIFORNIA STATE MINING BUREAU, that a sand one foot thick covering a square acre in extent will be capal)le of containing 19-iO barrels of oil, which is probably a very conservative estimate. The amount of oil recovered, however, is a very small percentage of that which is contained in the sand. It is generally agreed that not more than 20 to 30 per cent is extracted by means of wells. It has been assumed by operators that when a well ceases to produce, the oil sands in the vicinity have been exhausted. This is not the case. In all probabilities as much as 70 per cent of the oil is still present in the sand, and the reason for the decline of the well is due to the exhaus- tion of the gas, rather than the oil. The main force which drives the oil from the sand into the well is the expanding energy of the gas dissolved in the oil. It has been shown that California oils will absorb about 15 per cent of their volume in natural gas. This gas is absorbed in the oil in the same manner as soda water is charged with carbon dioxide. When a well is drilled into an oil sand, the i>ressure is suddenly reduced at this point and consequently the liquefied- gas expands and l)eLomes a true gas. This expansion forces the oil from the sands into the well, much in the same manner as w^hen the cork is removed from a l)ottle of soda water and the dissolved carbon dioxide gas forces the liquid out of the moutli of the bottle. The expansion of the liquefied gas from the oil takes place more readily in light oil than in heavy viscous oils. In the preceding paragraphs it was stated that fields along the crest of sealed anticlines produced the largest wells, while wells located on low dipping mono- clines were the longest lived and showed the slowest rate of decline. This can be explained on the assumption that along the crest of anti- clines the oil for the most part is of a comparatively light gravity and the liquefied gas expands readily, forcing in its first rush to freedom large cjuantities of oil into the well, and consequently giving a large initial production. This easy expansion allows a great portion of the gas to escape without doing its full share of moving the oil, which results in a rapid decline in the well and a large percentage of the oil is left in the sands without any force to drive it into the well. On the other hand in low dipping monoclines, such as the Kern River field, the oil is heavy and viscous and the liquefied gas cannot slip out of the oil readily and must, to escape, move the oil with it. This probably explains the slow rate of decline in fields of this character. Areas of Accumulation. In order to have a productive field there must not only be present beds of organic shale, but these beds must be of considerable thickness and must cover a large area in extent. It frequently luippens that wells located on opposite sides of the apex of an anticline differ greatly in their productiveness. In most cases of this kind, an examination of the field will show that on the side of the largest well the organic shales underlie the countr.y over a considerable area, while on the opposite side, where the small producer is found, the shales are present only in a limited area. PETROLEUM RESOURCES OF CALIFORNIA. 21 SUMMARY OF THE CONDITIONS NECESSARY FOR THE ACCU- MULATION OF OIL IN COMMERCIAL QUANTITIES IN CALI- FORNIA. (1) There imist be present in close association with the prospective field, thick beds of orjianic shale to serve as a source for the oil. (2) There nnist be present either in, or above, the organic shale, porous beds, between impervious beds to act as a reservoir for the oil. (3) The reservoir beds must be folded in a favorable structure, so as to cause the oil to accumulate. (4) There must be a large area of aecuiiiulation. (5) There must not be too great an interval in geological time between the organic shales and the formations composing the reservoir. Surface Indications of Oil. The best surface indication tliat a district contains oil is, of course, an actual seepage or iiow of oil somewhere in that area. "While all known productive fields of California do not always contain seepages, notably in the cases of closed or buried fields, nevertheless if the under- lying formations of these fields are followed to wliere they outcrop, in every case actual seepages are found. In the Tertiary foi-mations which contain the asphaltic oil, seepages can be readily found as the evaporation of the lighter constituents leave behind a heavy tarry residuum, which is noticeable long after the seepage has ceased to flow. In the case of the liglit oil of the Cretaceous formation, this evaporates entirely upon coming to the surface and leaves behind no residuum and unless the seepage is actually flowing, it is not likely to be found. In general, seepages occur along faults, cracks, and where the upturned edges of the formations outcrop. 'Gas Blows' and burnt shale areas are also good indications of oil. True 'gas blows' are found along faults, cracks and on the outcrops of formations where petroleum gas has in past times, or is at the present, escaping into the air. In almost every case this gas has by accident caught fire, which has resulted in the burning to a more or less slaggy condition of the formations in that vicinity. The burning has changed the color of the beds to either a vivid red or purple, or a dull white, depending upon wliether or not the beds contained iron compounds! Frequently in wild-cat districts it has been claimed that 'gas blows' are present, and for evidence long narrow ])lack and l)rown colored fragments of sandstone have been presented. It is the opinion of the Avriter that these so-called 'gas blows' are in no way connected with petroleum gas, but merely reju-esent a concentration of iron compounds along cracks ])y means of moving waters, with a resulting discoloration of the formation to black and brown. Notable gas blows are found in the Buena Vista Hills near Taft and in the McKittrick district. 22 CALIFORNIA STATE MINING BUREAU. 'Burnt Shale Areas' are eoniposed of shale or .sandstone which at one time or another contained seepages of oil and which by accident caught fire and burned, leaving the shale or sandstone in a condition that resembles a brick yard, the vivid red and purple colors of the rocks being particularl}^ noticeable in these areas. 'Burnt shale areas' are found in numerous places in the Santa INIaria and McKittrick Districts. Seepages, gas blows, and burnt shale areas do not of themselves mean that the district in which they are found is going to produce oil in commercial qnantities. There must also be present suitable structure, reservoir beds and a sufficiently Avide area of accumulation and origin. PETROLEUM RESOURCES OF CALIFORNIA. 23 CHAPTER II. Description of the Oil-Bearing Formations of California. General Geology and Structure of the State. In discussing the general geology' of California, the state may be divided into five provinces : (1) The Coast Ranges. (2) The Great Central Valley. (3) The Lava Beds of the Northeastern Region. (4) The Sierra Nevada Moun- tains. (5) The Desert Region of the Southeast. (1) THE coast ranges. In the extreme nortliwestern portion of the slate, in the counties of Del Norte, Trinity and Siskiyou, the Coast Ranges are known as the Siskiyou or Klaniatli ^Mountains. These mountains in general rise to an elevation of about 5000 feet and are extremely rugged. The prinoipai rivers in this district are the Klamath and the Trinity rivers. The geological formations consist of slates, schists and limestone, of Paleo- zoic age, together with a younger series of altered sands and shales, probably of Jurassic age. In addition, there are numerous areas of granitic rocks and gneisses, the age of which is uncertain. The Jurassic sediments contain large intrusive masses of serpentine and l)asa]tic rocks. All of these sediments have been sharply folded and their structure is intricate and complex. South of the Klamath Mountains and north of the Bay of San Fran- cisco, the Coast Ranges are composed of a series of long, narrow, parallel ranges and valleys. These ranges have an elevation in general of about 2100 feet, and present to a marked degree a sameness in eleva- tion. AYhen viewed from a liigli point this region appears like a huge dissected plateau. A. C. Lawson' has stated that tliis dissected plateau represents an ancient peneplain, which has been uplifted from a nearly ba.se level condition to its present altitude, this uplift being marked by at least six marine terraces. Tlie principal river valleys consist of the Eel River in the north ; the Russian River in the central portion and the Napa and Sonoma valleys in the south. In the greater portion of this area, the rocks exposed consist of cherts, sandstone, crystalline schists and serpentine of the Franciscan formation (Jurassic?). Along the coast there is a narrow strip of Cretaceous, together with small areas of rocks of Tertiary age. On the great valley side of the moun- tains a great thickness of Cretaceous sediments is exposed together with small isolated patches of rocks of Tertiary age. South of the Bay of San Francisco, the Coast Ranges in general trend nearly parallel to the Coast. The average elevation is from 2000 to 3000 feet, except south of Los Angeles, where the San Gabriel, San Bernardino and San Jacinto Ranges reach altitudes from 10,000 to 11,000 feet. The most prominent topographic feature is the series of rather broad interior valleys which separate the different ranges between San Francisco and Los Angeles. South of Los Angeles, these valleys are conspicuous by their ab.sence and the general trend of the small valleys, 'Lawson, A. C. Univ. of Calif. Bull. Dept. of Geology, Vol. 1, No. 8. The Geo- morphogeny of the Coast of Northern California. 24 CALIFORNIA STATE MINING BUREAU. that are present, is at right angles to the Coast. Beginning at the north these interior valleys consist of the Santa Clara Valley in Santa Clara Comity; the San Benito and Trcs Finos valleys in San Benito Connty ; the Salinas A'alley in ^lonterey County and northern San Luis Obispo County; the Cuyania and Santa Ynez valleys in Santa Barbara County; the Simi Valley and the Valley of the Santa Clara River in Ventura County; the San Gabriel and San Fernando valleys of Los Angeles County; and lastly, the Valley of the Santa Ana River in Orange County. The principal ranges consist of the Santa Cruz ^Mountains, which lie along the boundary between Santa Clara and Santa Cruz counties; the Diablo Range, which forms the ea.stern edge of tlie Coast Ranges from Suisun Bay to Coalinga : tlie Cabilan Range, which lies between San Benito and IMonterey counties; the Santa Lucia Range, which forms a mountainous region along the coast of ]Monterey and San Luis Obispo counties: the Temblor Range, which lies in eastern San Luis Obispo and western Keni counties ; in Santa Barljara are the San Rafael and Santa Ynez ranges, which have a northwest direction ; the Topatopa Mountains in Ventura County and the Santa ]\Ionica Moun- tains in western Los Angeles County, trending almost due east and west. The San Gabriel ^Mountains in Los Angeles County, the San Bernardino Range in San Bernardino Count}', tlie San Jacinto Range in River- side County, and the Peninsula Range, which extends southward through San Diego County into Lower California separate the desert tegion from the Coastal Plane of Southern California. These ranges, both in topography and geolog}'. bear a marked resemblance to the Sierra Nevada and may be regarded as a southward extension of this system. The Santa Ana JMountains in Orange County may be regarded a-s the most southward range of the true Coast Range type. For the most part the Coast Ranges, between San Francisco Bay and the Santa Ana ^Mountains, are composed of unaltered sediments of Cretaceous and Tertiary age. Exceptions to this condition are found in the central portion of the Diablo Range, where large areas of the Franciscan (Jurassic?) are exposed and in the Santa Lucia and Gabilan ranges which consist almost wholly of highly altered sedi- ments of Paleozoic age, together with granite rocks and gneisses. It is in the Tertiary sediments which lie along the eastern and western flank of the middle Coast Ranges, that the principal oil fields of Cali- fornia are found. South of the Santa Ana River, the sedimentary rocks are limited to a narrow strip along the Coastal Plane and a few isolated patches in eastern Riverside County. The San Gabriel, the San Bernardino, the San Jacinto and the Peninsula Range are com- posed of granitic rocks. (2) THE GREAT CENTRAL VALLEY. The Great Central Valley of California com[)rises an area of al)()ut 16,000 square miles and includes the Sacramento Valley in the north and the San Joaquin Valley in the south. The north end of the Sac- ramento Vallev is at Redding, Shasta Countv, where it has an elevation PETROT.EUM RESOURCES OF CATJPORNIA. 25 of 600 feet ami a witltli of about trn miles. Kxtciidiim southward, its width increases to 20 miles at Ked BlutV. 40 miles at Willows, and 45 miles at Snisiin Hay, into wliieli the Saei-amento River disrhari^es. The San -Toaqnin has a width of alxnit 30 miles at its northern extremity near Stoekton. thence it increases in width as it extends southward, till it reaches a maxinnnn of 60 miles near llanford. Kings County. At the base of the Tehacliapi Mountains, in Kern County, where the vallev ends, it has a width of about :^(V miles and an elevation of al)Out 1000 "feet. The valley's surface is almost entirely covered by alluvium, but undoubtedly formations of Cretaceous and Tertiary age are present beneath the surface. The only notable interruption in the surface con- tinuity is formed by the jNlarysville Buttes, a vulcanic mass in the central part of tlie Sacramento Valley. Between Red Blutt' and Suisun Bay, the alluvium of the valley floor rests, on its western edge, against I'ocks of Cretaceous age, exposed in the foothills of the Coast Ranges. South of San Francisco Bay, the valley floor Is terminated on its western side by rocks of Tertiary age, exposed in low-rounded hills that .jut out into the valley's floor. The large producing oil fields of the San Joaquin Valley are found in the.se low hills. On the eastern edcre, or Sierra side, the alluvium of the valley floor rests for the most part against the metamorphic and crystalline rocks of the Sierra Nevada and except for an area of Miocene around Bakersfield and a snudl thickness of Tejon bet\veen the ]\rariposa and the American rivers, sedinumtary rocks of Tertiary age are conspicuous by their absence. In the extreme northeastei-n part of the Sacramento Valley, there is a large area of volcanic tuff and lava exposed. (3) THE LAVA BEDS OF THE NORTHEASTERN REGION. This lava covered region forms an extensive area in the northeastern portion of the state and includes the counties of Modoc, Lassen and the eastern parts of Siskiyou, Shasta and Tehama counties. The central and northern portions of this area form a plateau which is between 4000 and 5000 feet in elevation. In the northeast the Warner Moun- tains reach an altitude of 8000 feet. In the south the Las.sen Peak Range reaches an altitude of more than 10,000 feet, and on the west, :\rount Shasta towers at an altitude of 14.880 feet. Practically all this region is covered with lava, probably of late Ter- tiary age. In a few places there are lake bed deposits of loose sands and clays and fresh water diatomaceous shale. (4) SIERRA NEVADA. The Sierra Nevada is the dominating physical feature of the state. It forms a great single range that extends from the base of the Lassen P>iibali. The i\Ieganos shales are probal)ly the source of the oil found in the Tejon sandstone of the Simi Valley and the Sespe district of Ventura County. The Te.ion consists of a hard C Of^rsp-gr^iiripd liffhf ypHnw and -gray sandstone^ The basal sands in the San Joaquin Valley and Southern California are frequently of a reddish color due to iron oxide. On the east side of tlie Sacramento Valley, the Tejon is known as the lone and consists of about lOUO feet of fine clays and some sandstone. The maxi- mum thickness over the entire state is about 5000 feet. Beds of li^ni_t^ and red and yellow pottery clays are eharaetoristic nf ThT^' Tpj'^'' In, V entura County the Topa-Topa. formation uiay.be considered as behig o f Tejon ag e. The Tejon occurs in the following areas: (1) San Diego County. (2) Santa Ana Mountains. (3) Ventura County. (4) Santa Ynez IMountains. (5) West side of the San Joaquin Valley. (6) East side of the Sacramento Valley. (7) Isalated areas in the northern Coast Ranges. Characteristic fossils are the Venerk ardia plamcosta and Turrit ells In the Simi and Sespe regions of Ventura County, the Teion is thp principal nil-hpflring fm-umtimi niul vip1d« a oTPPnit;h.h1a^1r ml nf abmit 40° Baume gravi ty, whifli has accnmnlfltprl hi fbp Tpjon sands ff ftni the underlying iNIeganos shale s. In the Coalinga field, the Tejon con- tains some oil which has migrated from the ^Foreno shales. In the Kreyenhagen Hills of Kings County, the Tejon sands yield small amounts of green oil. Oligocene. The Oligocene has been definitely recognized in the following areas: (1) .Ventura County where it is known as the Sespe formation. (2) West side of the San Joaquin Valley from the Coalinga district to Livermore Pass, where it is known as the Kreyenhagen shales. (3) Santa Cruz Mountains, where it is known as the San Lorenzo series. The Kreyenhagen shales may be regarded as lower Oligocene and consist of pink and chocolate colored diatomaceous and foraminiferal shales; clay shales; and a little sandstone. They have a maximum thickness of about 1500 feet, and are the original source of the main body 30 CALIFORNIA STATE MINING BUREAU. of petroleum in the Coalinga field, which has undoubtedly migrated from these shales into the overlying Vaqueros sandstone. The characteristic fossils are Leda lincolncnsis and Fusinus lincoln- ensis. The Sespe formation is found in Ventura County and consists of about 3500 feet of white, red and brown sandstone, interbedded with beds of purple and red clays. In the Simi Valley, this formation con- tains several prominent beds of conglomerate. There are no known fossils in this formation and it probably in part represents a conti- nental deposit. In the Sespe and South ^Mountain districts of Ventura County, it is the principal oil-bearing formation, the oil having collected in the Sespe from the underljang Eocene shales. The oil is black and averages about 32° Baume gravity. The Sespe may be regarded as upper Oligocene. The San Lorenzo formation is found in the Santa Cruz IMountains and consists of about 3000 feet of fine-grained sandstone and shale. Characteristic fossils are Cardium lorcnzanum and AcUa dalli. The San Lorenzo formation- is not regarded as an oil-bearing formation. However, at IMoody Gulch in the Santa Cruz ^Mountains it contains a small amount of light-gravity oil, which has migrated along a fault plane from the Monterey shale into the San Lorenzo. Approximately 1.300,000 barrels of oil were produced from beds of Oligocene age during the year 1920, which is about 1.3 per cent of the entire production of the state. Miocene. The Miocene may be regarded as having two main divisions, the lower Miocene which contains the so-called Monterey Series and the upper Miocene, which contains the San Pablo Series in the San Fran- cisco Bay region and the Santa Margarita Series of middle California. The ]\Ionterey Series is a name which has been recently applied by the U. S. Geological Survey to the lower portion of the jNIiocene in Cali- fornia and covers what was formerly recognized as two separate forma- tions, viz: (1) The Monterey shale (called in various reports of the U. S. Geological Survey, Puente shale, Monterey shale, the Modelo formation, Saliuas shale and ^Maricopa shale). (2) The Vaqueros sandstone. Inasmuch as the terms Monterey shale and Vaqueros sandstone have become fixed by long usage among the oil men of California to designate two of the most important oil horizons of the state, it is the opinion of the writer that this terminology should remain in discixssing oil field geology. For the purpose of this report, while the term Monterey Series will be regarded as designating the lower jMiocene, the term ]\Ionterey shale will be continued in use to designate the upper portion of the series, which is mainly shale, and Vaqueros .sandstone will be used for the lower portion.^ 'Note. Prof. B. L. Clark of the University of California hns recently proposed the name of Temblor to designate the upper portion of the Monterey Series and the writer has used this name in the correlation tables (Plate II) as the standard name for the upper portion of the Monterey Series. PETROLEUM RESOURCES OF CALIFORNIA. 31 The lower portion of the ^lonterey Series, which is mainly sandstone consists of liard yollowisli-a and Pccten pecJiliami. The Monterey shale formation is very widespread in the Coast Ranges, occuring as far north as Point Arena, Mendocino County, and as far south as the Orange and San Diego County line. The principal localities are (1) Point Arena and Point Rej^es. Those two localities are the only known occurrences north of the Bay of San Francisco. (2) Berkeley Hills. (3) Santa Cruz Mountains. (4) Vicinity of IMonterey. (5) Salinas Valley, where it ha.s been called tlie Salinas shale. (6) San Luis Obispo and Santa Barbara counties. (7) Ventura County, where it has been called the Modelo formation. (8) Los Angeles County where it has been called the Puente shale. (9) Orange County. (10) Kern County where it has been called the Maricopa shale. *NoTE. — Recent paleontological work has shown that these so-called Vaqueros sandstones probably belong to the upper portion of the Monterey series and can be classified as belonging to the Temblor formation. 32 CALIFORNIA STATE MINING BUREAU. The IMonterey shale is the original source of the oil and underlies the reservoir beds in the following fields: (1) ^Midway-Sunset field. (2) Kern River. (3) Los Angeles and Orange County fields. (4) The Ojai, the Piru, the Santa Paula and Ventura Avenue fields of Ventura County. (5) The Arroyo Grande field. In tlie Santa I\Iaria district the oil has collected directly in the Mon- terey shale, a fractured tiinty zone near the base of the formation acting as the reservoir. The oil is black and of an asphaltic base ranging in gravity from 9° Haume in tlie Casnialia field to •'^6'^ Baume in the Midway. Jt is probal)le tliat ovei- 60 per cent of the 105.000,000 barrels of oil produced in California in 1020 liad its origin in the ^Monterey shale formation. IMost of this, however, has migrated to the overlying forma- tions and the ^lonterey actually yielded only about 6,000,000 barrels or 6 per cent of the entire yield of tlu' state. The Santa Margarita formation (upper Miocene) consists of a hard compact sandy diatomaceous shale and a white granitic sandstone member. In the Salinas Valley area the white sandstone is best developed and the diatomaceous shale is only about -100 feet thick. In the San Joa- quin Valley the diatomaceous shale is well developed and consists of about 2000 feet of hard compact blue shale, somewhat more sandy than the ^Monterey diatomaceous shale. It is found only in the Middle Coast Ranges between the Salinas Valley and the San Joaquin Valley. The characteristic fossils are Pecten cra^sicardo and Ostrea titan. The Santa Margarita is oil-bearing in the following areas. (1) Small seepages near San Ardo in the Salinas Valley. (2) Small seepages in the Park field and Lonoak districts of jMonterey County. (3) Along the west side of the San Joaquin Valley from Sunset to Devil's Den, where it overlies the ^Monterey shale and probably contributes to the oil in the McKittrick beds which form the principal reservoir beds of the west-side fields. In the Belridge and Lost Hills fields oil has col- lected directly in certain sandy beds of the Santa Margarita shale. This oil is rather light, averaging almost 38° Baume and is commonly known as brown shale oil. It is roughly estimated that the Santa Margarita yielded in the San Joaquin Valley almost 2,000,000 barrels in 1920 or almost 2 per cent of the state's production. The San Pablo formation consists of about 1500 feet of a rather coarse, blue-gray sandstone, found principally in the vicinity of San Francisco Bay. Characteristic fossils are Pecten crassicardo and Pec- ten raijmondi. The San Pablo is not known to contain oil, in any appreciable amounts. Pliocene. Formations of Pliocene age are the mo.st prolific s;ouree of oil in the state. This is due to the. fact that they overlie the diatomaceous shale of the ]\Ionterey. The lower portion of the Pliocene may be considered as being represented by the Fernando Series in Southern California, PETROr-EUM RESOURCES OF CALIFORNIA. 33 the McKittrick trmnp in tho San Joa(iuin Valley and middle Coast Kange, and the Merced Serit's in Northern C'alifoi'nia. The upper Pliocene may be called the Saugus in Southern California and the I'aso Robles in Central and Northern California. The Fernando is found south of the Teliachapi mountains and the Santa ^laria Kiver. It consists of soft blue shales and medium coarse gray and white sands. Near the top there are beds of gravel made up of well rounded crystalline pebbles. It has a maximum thickness of al)OUt 8000 feet. It is best known in the following localities: (1) Puente Hills. (2) Vicinity of Los Angeles. (3) Southwestern Ven- tura County. (4) Santa Maria district. In the following fields its beds are the principal sources of oil. (1) Los Angeles and Orange county fields. (2) The Ojai, Pirn, Santa Panla and Ventura Avenue fields of Ventura County. (3) The Sum- merland field. Characteristic fossils of the lower Pliocene are Pcclen owzni and Pecten Jiralcjji. During the year 1920 beds of Fernando age produced 30,500,000 bar- rels of oil or 30.5 per cent of the entire state's production. In the San Joaquin Valley beds equivalent to the Fernando are called McKittrick and consist of loose gray sands and fine blue shales. The maxinuun thickness is about 4000 feet. The J\IcKittriek overlies the Monterey and Santa Margarita shales in the ]\Iidway-Sunset, IMcKit- trick, Elk Hills, Belridge, Lost Hills and Kern River fields and con- tains the principal oil sands of these fields. During the year 1920 these beds produced 43,800.000 barrels of oil or 43.8 per cent of the total state production. The oil is black and averages about 26° Baume. In the ]\Iiddle Coast Ranges, beds equivalent to the McKittrick and Fernando formations have been called Etchegoin and Jacalitos and consist of loose sands, gravels and bine shales. They contain no oil in commercial quantities. In Northern California the lower Pliocene is called the Merced and consists in general of white and gray sandstone, conglomerate and muddy shales. It has a maximum thickness of about 3000 feet. It is best developed on the San Francisco Peninsula and in the Santa Cruz Mountains, where it overlies the ]\Ionterey shale and contains oil in small quantities along the coast side of the mountains between Santa Cruz and Ilalfmoon Bay. In this region it is known as the Pnrisima. In Southern California the uppermost Pliocene may be called the Saugus and consists of soft sands and gravels. It contains no oil in commercial quantities. The division between the Fernando and Sau- gus is not noticeable excei)t on detail work. In central and northern California the loose sands and gravels of the upper Pliocene may be called the Paso Robles. These beds contain no oil in commercial quantities. Characteristic fossils of the upper Pliocene are Pecten hellus and Crepidnla princcps. Plate II shows a correlation of the oil-bearing formations of Cali- fornia from tlie Cretaceous to the Pliocene. This table is not intended -13322 34 CALIFORNIA STATE MINING BUREAU. as a complete correlation table of all the Tertiary formations of the West Coast, but is intended to correlate in a rough manner for practical use those formations wliich liave an influence upon the origin and accu- imilation of petroleum in California.^ Formations from which oil has been produced in commercial quantities for an appreciable length of time have been printed in red. Formations fi'om which oil has l)een obtained in small quantities, but not on a commercial scale, or wliicli contain authentic seepages of oil, have been printed in green. Formations from which there has been no actual production of oil or which contain no authentic seepages of oil have been printed in black. These differentiations are based upon the actual facts known to date. It is not intended that this should condemn those formations which have been printed in black or green, as it is possible that future drill- ing might show that they contain oil in commercial (juantities. 'In preparing this table the writer is indebted to Prof. B. L. Clark of the University of California for assistance and advice. PETROLEUM RESOURCES OP CALIFORNIA. 35 CHAPTER III. Possibilities of Oil in the Coast Area North of the Bay of San Francisco. (Includes tlie counties of Marin, Sonoma. Mendocino, Humboldt, Trinity and Del Norte.) The general geofrrapliy and geology' of this region has been discussed in Chapter II. A.s stated there, the niajdr portion of this area is cov- ered with cry.stalline rocks and therefore affords no possibility of being oil bearing. The oil possibilities are limited to small areas of sedi- mentary rocks in the Sonoma Valley and along the ocean edge from Rolinas Bay to tlie mouth of the Eel River. As tile county ])onndaries have been made to eonfonu more or less to the topogra{)hical and geological districts of this area, it may best be discussed in detail by counties. Marin County. Marin County is a rather rugged mountain area of 529 square miles. Geologically it has been divided into two areas by the San Andreas Fault, which runs in a northwest direction from Bolinas Bay to Tomales Bay. The country lying east of tlie fault, wliich is the upthrow side, is called the Marin i)eninsnla and comprises about three-quarters of the county. The rocks exposed are of the Franciscan formation of Jurassic age and consist of beds of massive gray-green sandstone and radiolarian chert which have been intruded by masses of serjientinc and basalt. Both tbe character and age of these beds preclude their being oil bearing and this district may be dismissed as having no oil possibilities. The country lying west of the San Andreas fault is called the Point Reyes peninsula and as a result of being on the downthrow side of the fault rocks of Miocene and Pliocene age are found exposed in this district. These formations consist of bituminous shale of the Monterey forma- tion and loose marine .sands of the ]\Ierced formation (lower Pliocene.) The ]\Ionterey shales cover about nine-tenths of the peninsula. In the northern portion near Inverness and Tomales Bay they rest directly on the granitic rocks. At Bolinas Point and Diixbiiry Reef the shales are distinctly bituminous and there are small seepages of heavy black oil at both of these localities. Due to the close proximity of the shales to the fault zone, they have been intensely folded and crushed, which obscures the true natur(^ of the structure. However, there are at least two well defined anticlines on the peninsula as well as numerous minor folds. The axis of the most westerly fold may be seen along the beach one-half mile west of the town of Bolinas where it strikes N. 30° W. The axis of the second fold runs along the high ridge about one-balf mile west of Pine Gulch and Oleina Creek. This strikes in a general northwest direction. The total thickness of the Monterey in this area is about 4000 feet. The ]Merced sands occupy a small area in Paradise Valley, just north of the town of Bolinas. The total thickness of these 36 CALIFORNIA STATE MINING BUREAU. sauds is about GOO feet and tlie general dip is about 30° to the east. Ordinaril}- it would be expected that these sands would be petroliferous, as they overlie the bituminous shale ; this is not the case, however, as they show no evidence of any oil content. This lack of oil is probably due to the great unconformity l)etween these beds and the JNIonterey shale. Three wells have been drilled just west of the town of Bolinas on tlie Garzolia Ranch. Two of these were drilled about one-fourth of a mile west of the ranch house at the head of a small gully. These wells were drilled to a depth of about 1800 feet in the ^Monterey. The one nearest the ranch house encountered no oil, the one nearest the ocean had a small showing at 700 and 1200 feet. A third well was drilled on the sea cliff just back of Duxbury Reef. This well went into the ^Monterey for 2800 feet and encountered small showing at 200 and 2400 feet. These wells were drilled about 1905. The possibility of obtaining oil in commercial quantities in this dis- trict is not very good. The upper ]\Iiocene sands which once probably overlayed the IMonterey shale and in which the oil content of the shales probably collected have been removed by erosion. Such oil as remains is in small quantities in fractured zones in the shale and it is doubtful if anything more than a showing would be encountered in any well drilled in this area. Fig. 3 shows a generalized east and west section through a point about two miles north of Bolinas. Sonoma County. Sonoma County comprises an area of 1577 square miles. Three- fourths of this area is covered l)y rocks of Franciscan formation and therefore cannot be considered as having any oil possibilities. One area of sedimentary rocks which might possibly contain oil, con- sists of a narrow strip of the Cretaceous formation which outcrops along the coast from the Russian River north to the Gualala River. This strip of Cretaceous is almost four miles wide and rests on its eastern edge on the Franciscan. These rocks, which are probably of Chico age, consist of massive fine-grained sandstone and pebbly sand- stone interbedded with fine dark-colored muddy shales. The general dip is about 35°-40° to the west. On certain of the wave-cut terraces the Chico is covered by terrace deposits of fine brown sand. There are no known indications of oil in this area, and it cannot be considered as having anj' possibilities as it contains neither favorable structure nor organic shales. A second area of sedimentaries is around the town of Valley Ford, where there are about six square miles of fine sands, clays and con- glomerates, probably of the Merced formation (Lower Pliocene). These beds are lying directly on the eroded surface of the Franciscan. There is nothing to indicate that these beds contain oil and this area can be dismissed as having no possibilities. A third area of sedimentaries in Sonoma Count}' is in the Sonoma Valley. The east and w^est side of the valley is made up mainly of Franciscan formation and Pliocene lava flows. However, in the center of the valley there is a range of hills known as the Sonoma Mountains and which extend from Santa Rosa to San Pablo Bay. In these hills there are outcrops of sedimentary rocks of Tertiary age, which contain seepages of oil. PETROLEUM RESOURCES OF CALIFORNIA. 37 \ ^ \ \ ^ J33a Ad nay no S. A o O C3 1—1 J/) ^ < z .^ ^.M a _J OJ o p^ CO tn O) >» 0) •^^ _J o p-l OJ M -t-* WI CO o OJ to 38 CALIFORNIA STATE MINING BUREAU. At the upper end of these hills, near Santa Rosa, tlie formations consist of fine sands and clays of the INIerced (Lower Pliocene) which are lying on the Sonoma tuff and ]\[arkwest and&site (Lower Pliocene). Beneath these lava Hows there is a small thickness of San Pahlo forma- tion which, in turn, rests upon the Franciscan. There is nothing to indicate that this portion of the hills contains oil. At the south end of the hills, between the towns of Petaluma and Sonoma, the formations consist of medium coarse blue sands and fine sandy shales, pro])ably of the San Pablo formation, which are dipping at an angle of about 35° to the southeast; on their western edge these beds probably rest ui)on tlie Franciscan beneath Petaluma Creek. The contact, however, is obscured by overlying beds of Pliocene tuff and lava. The eastern edge of these San Pablo beds, near the town of Sonoma, is also covered by volcanics, which are dipping at about 20° to the east. On the hills east of the town of Sonoma, the dip changes and the Sonoma tuff and ^larkwest andesite are found dipping at an angle of about 30° to the west. Overlying these lavas is a small thick- ness of INIerced sands and conglomerates. Near the Sonoma-Napa County boundary line, the S:in Pablo beds again appear, this time dipping 30^ to the west, indicating tliat there is a syncline in the valley south of the town of Sonoma. East of the Sonoma-Napa l)oundary, the San Pablo beds rest unconformably upon a massive buff' sandstone, prol)ably of Tejon age, which is dipping at about 70° to the east. Evidence as to petroleum is as follows : On the Ducker ranch, three and one-half miles east of Petaluma and one and one-half miles east of the old adobe fort, in the bottom of a small canyon, there are seepages of a hea\y black asphaltic oil in the blue sands of the San Pablo formation. These beds are apparently dipping at an angle of about 40° to the southeast. About 1909, four wells were drilled on the mesa just above the seepages. The Ramona Oil Company drilled three of the wells and the Petaluma Home Oil Company, one well. These holes have now been a])andoned. AVell No. 1 of the Ramona Oil Company was drilled in blue clay and })rown sand to a depth of 800 feet, where it is claimed that gas was struck, which had a pressure of 217 pounds and a flow of 690,000 cubic feet per 24 hours. The well, however, soon clogged up and the flow ceased. Well No. 2 was drilled to a depth of 910 feet, logging oil sands at 335 to 400 feet. In none of these wells, however, was oil obtained in commercial quantities. The origin of this oil which is found in the San Pablo l)eds is noi clear. There are no known outcrops of ^Tonterey shale in this district. South of San Pablo Pay, however, in Contra Costa County, there is quite an area of bituminous shale of the IMonterey. Tt is po.ssible that this shale is present beneath San Pablo Bay, and the San Pablo sand- stone Avhich is dipping to the southeast may be in contact with these bituminous sludes, beneath the waters of the bay. Tn that case, the oil content of the shales would tend to niove up the dip into the porous sands of the San Pablo formation and appear in seepages along the outcrop of this formation. It is the opinion of the writer that the structural conditions are not favorable for the accumulation of oil in appreciable amounts in this area. PETROLEUM RESOURCES OF CALIFORNIA. 39 Mendocino County. Mendocino County lias an area of 3453 square miles, the major portion of which is rugged and mountainous. The sedimentary rocks are confined to a sti-ip along the ocean edge and small isolated areas in the valley of the Eel Kiver. The remainder of the country is covered with metamorphic rocks of the Franciscan formation and can be listed as unfavorable for oil. The strip along the coast averages about eleven miles in width from east to west and covers the entire sixty miles of ocean frontage of the county in a north and south direction. The northern portion of this strip, from the Humboldt County line, as far south as tlie Garcia River, is composed of rocks of the Chico formation. These beds consist of massive gray sandstones and fine dark-colored shales. In some places tlie.se shales have a .slatey appearance. The forma- tions have been much deformed and crushed and good dips are difficult to obtain. In general the beds lie in a monocline, dipping about 35° to the west. There is no known indication of petroleum in this area of Chico and both structural conditions and the character of tlie rocks are unfavorable for the accumulation of oil. In the vicinity of Point Arena, the Chico is overlayed by bituminous shales and some sandstone of what is probably the INIonterey formation. This area of Monterey covers about 25 square miles. Its northern boundary is marked by Alder Creek, where the shales are lying uncon- formably upon the Chico. The eastern boundary is along the Garcia River, Avhere the Monterey has been faulted against the Chico by the San Andreas fault. The southern boundary is found about 2^ miles south of the town of Point Arena, where there is apparently a fault contact between the Monterey and the underlying Chico sandstones. Plate III is a reconnaissance map of this area, showing structure and areal geology. The Monterey formation is at least 5000 feet thick, the major por- tion of which consists of diatomaceous shale, of both the flinty and chalky varieties. In the upper 20C0 feet there are numerous leuse,s of fine-grained sandstone. In the lower TOGO feet there are two well defined beds of medium coarse-grained sandstone. These beds are about 150 feet thick. The general trend of the formation is N. 45° "W. Three well defined folds are found within this area of Monterey. The most easterly is north of the Garcia River and runs through the town of Manchester. The sandstone beds of the lower portion of the ]\ronterey are exposed along this fold. The second fold is found running through the town of Point Arena. The third and last fold is found close to the beach, running N. 45° W., through the center of Sec. 10, T. 12 N.. R. 17 W., U. D. B. and M. As this fold crosses a portion of the O'Neal Ranch, it will be designated as the O'Neal anticline. In general these folds are rather narrow and steep, the dips ranging from 20° to 60°. Indications of petroleum are as follows : Along the sea cliffs, from the port of Point Arena as far north as the lighthouse, there are numerous seepages of dark asphaltic oil coming from fractured areas in the dia- tornaceous shale. Along the eastern flank of the syncline, correspond- ing to the O'Neal anticline and just southwest of the O'Neal ranch house, there is an outcrop of fine-grained bituminous sand about ten 40 CALIFORNIA STATE MINING BUREAU. feet thick which can be followed in a northwest direction for 3^ miles, finally ending in the sea cliff, just east of the lighthouse. The sand is heavily bituminized and smells strongly of gasoline. It is possible that this deposit might be mined and distilled at a profit. The following wells have been drilled in this disti'ict : The Mendo- cino Coast Oil Companv drilled a well, called the Robbins well, at the northwest corner of Sec. 11, T. 12 N., R. 17 W. A depth of 2240 feet in Monterey shale was reached, and it is claimed that good showings were found. On the Hunter Ranch, near the center of Sec. 11, T. 12 N., R. 12 W., a well was drilled by a Fresno company and called the John D well. It reached a depth of 1700 feet. The Robbins well was drilled in 1905, and the John D. well in 1910. Both wells are located in a syneline and can not be considered as testing out this district. In 1918, Brandenstein and Silverberg drilled a well about 150 feet east and north of where the west line of section eleven runs into the ocean. This well was located on the axis of the O'Neal anticline. A depth of 780 feet was reached and tar sands were logged from 522-715. This hole was not drilled deep enough to be a fair test of this area. The most favorable area for drilling in this district consists of about 400 acres in sections 10 and 11, T. 12 N., R. 17 W., M. D. B. and M. This area is on the axis of the O'Neal anticline. The structure is favorable and there is also the possibility of a drainage area from under the ocean. Seepages indicate that the fold contains some oil ; l)ut whether or not it is in commercial quantities can only be told by drilling. The other areas of sedimentary rocks in Mendocino County are along the Eel River in the vicinity of Round Valley, Laytonville and AVillits. These beds consist of shale and sandstone and are found in small isolated patches on the Franciscan. In general they vary from 100 to 500 feet in thickness and cover areas of not more than four or five square miles. Small seams of coal are found in these beds and the age is probabl}'' Eocene. There is nothing to indicate that they contain oil. Humboldt County. The only area in Humboldt County that is worthy of consideration as a possible oil field, consists of a body of sedimentary rock which lies along the coast from the Mendocino County line to a point about twelve milas north of Eureka. The east boundary is marked in the southeast by the south fork of Eel River and in the northeast by a line about six miles west of Mad River. The remainder of the county is covered by the following formations : (1) An area of Franciscan sandstone, chert and serpentine lies east of the sedimentaries above mentioned and covers an area ot aboui twelve miles in Avidth, running in a northwest direction across the center of the county from the IMendocino County line to a point on the coast near Trinidad. (2) Immediately east of the Franciscan, and parallel to it, is an area of the Knoxville (Cretaceous) formation, occupying an area about four miles in width and stretching in a northwesterly direction from a point where the Van Dusen River crosses the Trinity County line to a point on the coast near Big Lagoon. (3) The north- eastern portion of the county, east of the Knoxville area, consists of limestones, schi.sts and slates of Paleozoic age, together with some granite. PETROLEUM RESOURCES OF CALFPORNIA. 41 None of the three above-mentioned areas contains any evidence of oil or others any inducement for drilling from a geological standpoint. In the sedimentary area along the coast between Eureka and the Mendocino County line, tliere are numerous indications that the forma- tions contain oil, at least in a limited anumnt. This area will, therefore, be discussed somewhat in detail. For the purpose of discussion, it can best be divided into two districts. First — That area lying at the mouth of Eel River and stretching appro.ximately from Ferndale to McKinleyville, which may be con- sidered as the flood plane which the river has cut in the soft Pliocene beds Avhich are found outcro])])ing here. On the north flank of Bear Kiver Ridge and just south of the town of Ferndale the best outcrops are found. Here there is a thickm ss of over 5000 feet of soft muddy- clay shales and fine-grained wliite sandstone, striking approximately a little north of west and dipping on an average of 20° to the northeast. These beds are known as the Wildcat Series and are believed to be of Pliocene age, although it is possible that the lower beds may be of Miocene or even Eocene age. They are resting unconformably upon the underlying massive Cretaceous sandstone. North of the Eel River the same ])eds are found dipping to the southwest and it is evident that, structurally, the valley of the Eel River at its mouth is a synclinal trough, the axis of which runs through the town of Fortuna, striking a little north of Avest. In the vicinity of Eureka, the Wildcat beds are apparently dipping to the west and it is possible that small folds are present in this vicinity. At various times oil and gas have been reported as being present in water wells drilled in this district. The writer, however, found no see])ages or indications of petroleum gas. The possibilities of this district as an oil field depend upon whether there are favorable folds, and the presence of organic shale at a reason- able depth beneath the Wildcat beds. Apparently both of these factors are lacking, although it is possible that a more detailed survey might find evidence of their presence. Second — This district comprises that area lying approximately south and west of the Eel River. Indications of petroleum eonsisi of a series of seepages of light oil running in a line from the town of Briceland to Capetown, a distance of nearly forty-five miles. The territory that can be considered as offering any possibilities consists of the counuT drained by the Bear and Mattole rivers and the district around Briceland. The formations exposed consist of a lowermost member of massive blue-gray sandstone of medium-grained texture, interbedded with dark fine-graineJ slatey shales. Stratagraphically above this is found a body of about 2000 feet of dark, fine-grained greasy carbonaceous shales, in which are found the seepages of oil. Interbedded with the shale are beds of blue-gray sandstone. The last and uppermost member of the series consists of about 500 feet of massive, hard blue sandstone. This series of beds is probably of Chico (Cretaceous) age. They rest uncon- fonnably on their eastern edge along the valley of the Eel River on the eroded surface of the Franciscan. Overlying the Chico, are small areas of soft, fine, white sandstone and fine, blue muddy shales and some pebbly sandstone. These beds are found in the vicinity of Garberville, Briceland, and the mouth of the Bear River and are probably of Ter- tiary age. 42 CALIFORNIA STATE MINING BUREAU. The petroleum found probably originated in the carbonaceous shales of the Chico and has collected in the interbedded sandstone beds. Any production must come from this member of the Chico. The locations of the line of .seepages and the wells drilled are shown on Plate IV. The oil is of a paraffine base, varying from light green to amber in color and from 30° Baume to 50° Baume in gravity. The topography consists of a series of ridges and narrow valleys, having a trend of N. 45° W., the elevation of the ridges being about 2500 feet. Faulting is common and the valley of the Mattole River is probably a structural valley formed by the San Andreas fault. The massive sandstone and the soft shales of the Chico do not contain well defined bedding planes and good dips are rare. No detailed mapping was made of the structure, but in general there are a number of anticlinal and synclinal folds striking in a northwest-southeast direction, the axis of the anticlines being marked by the narrow valleys and the synclines by the ridges. Along all the anticlinal axes erosion has cut down to the lowermost sandstone member of the Chico and in no case was a fold found which contained on its axis the oil bearing shale member of the Chico. Hence any well which would penetrate the oil sands must be located down the flanks of the folds, a location which is not generally considered favorable. Following is a list of the welLs drilled, with the reported results. (Located on Plate IV; map of southwestern Humboldt County.) Year 1865. Three wells were drilled on Oil Creek, marked on Plate IV as 1-2-3. Depth of these wells is unknown; it is reported that gas was found. "Well 1 is in Sec. 35, T. 2 N., R. 3 W. Well 2 is in Sec. 1, T. 1 N., R. 3 W. Well 3 is in Sec. 6, T. 1 K, R. 2 W. Two wells on Bear Creek, marked 4-5. Depth unknown ; encountered gas and a little oil. Well 4 is in Sec. 24, T. 1 N., R. 3 W. Well 5 is in Sec. 20, T. 1 N., R. 2 W. McNutt Gulch well, located in Sec. 30. T 1 S., R. 2 W. Depth 300 feet ; a little oil found ; is still seeping. INIarked 6 on Plate IV. Union well on the north fork of the Mattole, in Sec. 30, T. 1 S., R. 1 W., marked 7. Depth 500 feet ; reported as a fifteen-barrel well. Brown and Knowles well, in See. 25, T. 1 S., R. 2 W., marked 8. Depth 300 feet ; oil reported at 150 feet. The Joel Flat well, known as the Henderson well, in Sec. 15, T. 1 S., R. 2 W.. marked 9. Depth 500 feet ; reported as a ten-barrel well, and 300 barrels of oil are reported as being sold. Year 1891. Well on Buckeye Creek, in Sec. 5, T. 2 S., R. 1 W., marked 10. Depth 800 feet. ' Five-barrel well reported at 500 feet. Tliis well drilled by Far West Company and known as the Burrows well. AVell on Buckeye Creek, known as the Humboldt well, in Sec. 6, T. 2 S.. R. 1 W., marked 11. Depth 1900 feet; little oil. Davis Creek well, in Sec. 13, T. 1 S.. R. 3 W., marked 12. Drilled by Far West Company; depth 800 feet; little oil. petroleum resources of california. 43 Years 1901-1902. Mcintosh well on Zanona Rancli, in See. 29, T. 1 S., R. 2 W., marked 13 Depth 1700 feet. Reported as a fifteen-barrel well. Wild Goose well, in Sec. 15, T. 1 S., R. 2 W., marked U: Depth 1003 feet : oil encountered at 221, 420 and 775 feet ; reported as a fifteen- barrel well. ^ Craig well on the North Fork of the ^Mattole, in Sec. 30, T. 1 b., R. 1 W°. marked 15. Drilled to 800 feet ; strong showing of oil and gas reported. Iloaglin well in the upper :Mattole, in Sec. 1, T. 3 S., R. 1 W., marked 16. Depth 1800 feet ; showing of oil reported. Well at Brieeland, in Sec. 18, T. 4 S., R. 3 E., marked 17. Drilled to 780 feet; has been producing enough gas for 20 years to supply store and hotel. Year 1908. :\rcWherter well on Bear Creek, Sec. 14, T. 1 N., R. 3 W.. marked 18. Depth unknown ; reported showing of oil and gas. Brieeland Oil and Laud Co.. See. 33. T. 4 S., R. 4 E., marked 19. Drilled to 2100 feet ; little oil at 410, and granite encountered from 503 to 2100 feet. Years 1920-1921. Humboldt Oil Company now drilling in Sec. 20, T. 4 S., R. 3 E., marked 20. Northern Counties Oil Company now drilling in Sec. 36, T. 2 S., R. 1 W., marked 21. All townships and ranges refer to Humboldt Meridian. In regard to the reported amount of oil produced at the various wells, as far as the writer was able to ascertain, these figures are not based upon any accurate guage. as none of the wells produced for any length of time and they merely represent a guess on the part of the operator and therefore can not be relied upon to any extent. Possibilities. While a large number of wells have been drilled in this district, the majority without any definite results and a few successful in a small way for a limited length of time, the results can not be taken as a fair test, as methods of drilling and producing have improved and changed since the last of these wells were bored. The geological conditions in general and the structure in particular are not favorable for the accumulation of oil in large quantities. How- ever, the district along the Bear and ]\lattole rivers and the area around Brieeland appear worthy of further examination and testing, but any drilling undertaken should be with the understanding that the best Dossible return will be small.* "A report on the oil po.ssil)ilitif'S of tliis rortion of Humboldt County, by Mr. W. Stalder, can be found in Bulletin 69, California State Mining Bureau, 44 CALIFORNIA STATE MINING BUREAU. Del Norte County. Del Norte County is almost entirely covered with crystalline and metamorphic rocks. The center of the county is occupied by crystal- line limestones, slates and schists of Paleozoic age. Along the coast and also on the eastern border of the county there are outcrops of Franciscan sandstone, chert and serpentine. In the extreme north- west there is an area of granite, all of which are unfavorable for the presence of oil. The only areas of sedimentary roclcs of sufficient area to be mapped lie on the coast about three miles north of Crescent City. Here there is a thickness of about 700 feet of fine-grained, muddy, blue shales, occu- pying an area of about 10 square miles. On all sides the shales are lying on the eroded surface of the Franciscan. Fossil evidences indicate that the beds are of Pliocene age and probably belong to the Wildcat Series. Evidences of oil have been reported from time to time. The writer, however, could find nothing that indicated the presence of petroleum. In the middle of this area on Sec. 24, T. 16 N., R. 2 E., the North Coast Oil and Refining Company is drilling a well. All geological conditions are distinctly unfavorable for the presence of oil in Del Norte County. Trinity County. From a geological standpoint there is nothing to indicate that oil will ever be found in Trinity County. Formations exposed consist of highly metamorphozed sediments of Paleozoic age, some of which have been identified as belonging to the Carboniferous and Devonian periods. Beneath these are found crystalline schists and gneisses which may be pre-Cambrian. Large masses of granite are common. The only area of sedimentary rocks which has not been metamorphosed to a crystal- line condition is a small strip of Knoxville shale in the southwestern portion of the county, a continuation of the Knoxville area in Humboldt County. There is no authentic record of any indication of petroleum in the county. PETROLEUM RESOURCES OP CALIFORNIA. 45 CHAPTER IV. Oil Possibilities in Northeastern California. (Consists of the Counties of Siskiyou. Modoc, Shasta and Lassen.) The western portion of this region includes the di.striet of the Siski- you Mountains and the ea.stern portion, the district of the Lava Beds. Topographically and geologically this territory lends itself to he discussed by counties, Siskiyou County. The main line of the Southern Pacific Railroad from San Francisco to Seattle divides the county into approximately two parts. West of the line of the railroad the county is extremely nigged and mountainous and is known as the region of the Siskiyou Mountains. The formations exposed are highly metamorphosed sediments of Paleozoic and possibly pre-Cambrian age, together with large masses of granite, all unfavorable for containing oil. East of the line of the railroad is a great lava plateau, stretching eastward to the Modoc County line. From the plateau rise various vol- canic peaks to heights of 5000 to 8000 feet and in the south-central por- tion, ]\rount Sha.sta towers at a height of 14,380 feet. This region, with some minor exceptions, which will be noted below, is entirely covered by lava flows, chiefly andesites and basalts. The age of the lava is thought to be Tertiary with some Quaternary flows near IMount Shasta. No oil can be expected from the lava beds. Whether or not they cover Tertiary formations which might contain oil can not be told from sur- face indications. In the upper valley of the Little Shasta River, about six miles southeast of ^Montague, there are some fresh-water springs in the lava beds from which bubbles of gas are coming. These so-called gas springs have caused considerable oil excitement in this region. An examination convinced the writer that the gas is in no way connected with petroleum deposits. LTnmetamorphosed sedimentary areas are found in the following localities: (1) A small area of Chieo (Cretaceous) running from the vicinity of Round Mountain north through Hornbrook to the Oregon line at Hilts. The Chico consists of about 1500 feet of massive sand- stones and thin-bedded dark shales. The beds have a dip of 15° to the east and strike N. 40° AV. They contain no evidence of petroleum. Overlying the Chico on the east is a small area of fine-grained green sandstone and sandy shale containing seams of lignite, in the vicinity of Ager. This formation is proliably of Eocene age. It occupies an area about 18 miles long and 10 miles wide and has a dip of 20° to the east, where it rests against the lava beds. Its exact relationship to the lavas is not clear. No evidences of oil were found in this formation. (2) A second area of sedimentaries is found just east of Dunsmuir, along the valley of the McCloud River. The formations consist of more or less altered shales, sandstone and limestone of Carboniferous, Devonian and Jurassic age. They contain no evidence of petroleum. 46 CALIFORNIA STATE MINING BUREAU. Modoc County. Modoc County, lying in the extreme northeastern portion of the state, consists of a high plateau with an average elevation of nearly 5000 feet, from which detached mountain peaks and volcanic ranges rise to a height of 8OU0 and 9000 feet. Along the northern and eastern border there are large fresh-water lakes. The formations that outcrop consist, with some minor exceptions, of flat-lying lava beds, chiefly andesite and basalts, the age of which is probal)ly Tertiary. There is no sur- face evidence as to what underlies tlie lavas, or what is their total thickness. A few miles south of Fall River Mills, Shasta County, the Pit River has cut its channel down 18(X) feet in these fiat-lying beds, and there is no evidence of any underlying formations. Running from a point on the Pit River, about seven miles west of Canby and as far east as Alturas and as far north as Goose Lake, is a flat-lying bed of fresh water diatomaceous shale, varying from 25 to 50 feet in thickness. The .shale is interbedded between two lava flows and has a small caping of muddy shale. The deposit probably repre- sents a Pleistocene lake bed. The thickness of shale is too small to form any appreciable amount of petroleum and also there is lack of structure. Modoc County offers no inducements for drilling operations. Shasta County. Geologically, Shasta County may be divided into three districts: (1) The eastern half of the county, lying approximately east of the 122° meridian, is topographically similar to IModoc County. It is covered with the same lava flows and is likewise unfavorable for the development of petroleum. (2) The northwestern portion of the county, lying approximately west of 122° meridian and north of Redding, is a rugged, mountainous region. The formations consist of l)eds of limestone, chert, slate, sandstone and conglomerate, all more or less metamorphosed and belonging to the Devonian, Carboniferous, Trias- sic, and Jurassic periods. There are also masses of intrusive granite and serpentine. The count}^ has been much deformed and crushed and the beds are steeply tilted. This area has been mapped in detail and the report published by the U. S. Geological Survey,^ so no further description of the formations will be given here. While formations similar to the Devonian, Carboniferous, and Triassic limestone found outcropping in this area produce oil in other regions of the United States, no evidence of petroleum has been found in this area, nor is their struc- ture favorable for its accumulation. (3) The extreme southwestern portion of the county and the area around the head of the Sacramento Valley are covered by beds of Cretaceous age. Tertiary lava flows and valley alluvium. Beneath these sediments are masses of granite, ser- pentine and metamorphic Paleozoic rocks. As this region has been described in detail in the Redding Folio, U. S. Geological Survey, no further description of the geology will be given here. It suffices to say that the district contains no evidences of petroleum and is unfavorable for its accumulation. At the head of the Sacramento Valley, .just north of Redding, along Buckeye Creek, there are a number of salt and sulphur springs in the •Redding folio 13S. U. S. Geological Survey. PETROLEUM RESOURCES OP CALIFORNIA. 47 Chico beds from which small quantities of gas are emanating. On the strength of these so-called gas springs, four wells were drilled, the deepest being 1000 feet. They were drilled in the Chico and probably penetrated to the lowerniost ])eds of this formation. No oil was encoun- tered and only a small quantity of gas. It is the opinion of the writer that the gas found is not connected with petroleum deposits. Lassen County. Lassen County is similar to Modoc and eastern Shasta in topography and geology. The formations exposed are i)raetically flat-lying beds of lava, chiefly andesite and basalt. There is nothing to indicate their total thickness, or the character of the underlying formations, except on the south boundary of the county where they are lying on the eroded surface of the granites of the Sierra Nevada. South and east of AVest- wood there is a tongiu^-like mass of the Carboniferous formation com- ing in from Plumas County. There are no favorable indications of oil in Lassen County. 48 CALIFORNIA STATE MINING BUREAU. CHAPTER V. Area of the Sierra Nevada Mountains. (Consists of the following Counties: Pliunas, Siena. Eastern Part of Butte County, Eastern Part of Yuba County, Nevada, Eastern Part of Placer. El Dorado, Amador, Alpine, Calaveras, Tuolumne. Mariposa, Eastern Part of Madera, Eastern I'arts of Fresno and Tulare Counties and that I'art of Kern County that lies in the Sierras.) On the north this province may be considered as ending along the north line of Plumas County, where the granite peaks of the Sierra give way to the lava beds of Lassen County. The eastern edge is marked, from Plumas County as far south as ^lono County, by the boundary line of California and Nevada and thence it follows the west line of Mono and Inyo counties, marked by the great Sierra fault line, through eastern Kern to Tejon Pass, where the Sierra proper ends. The western edge, in this report, will be considered as lying just east of the foothills of the Sacramento and San Joaquin valleys. The Sierra Nevada structurally may be considered as a great fault block, which is being slowly tilted, the eastern edge, marked by the great fault scarp, going up and the western edge along the great central valley acting as the hinge. The result of this tilting has given a gentle western slope and a rather abrupt falling away on the east towards the desert of Nevada. The rock exposed can be divided into two series: (1) The Bedrock series consists of granitic rocks, together with bodies of schists and slates, which have been produced by intense metamorphism of ancient sediments and igneous rocks. The main body of altered sediments is known as the Calaveras formation, consisting of slates, quartzites and limestones of Carboniferous age and the Mariposa slates of Jurassic age. (2) The Super.jaeent series, which overlies the Bedrock series, is made up of beds of auriferous gravel of Eocene and ^Miocene age, together with lava flows, chiefly andesite and rhyolite tuff, probably of Miocene age. Along the foothills there are sediments of Cretaceous and Tertiaiy ages. These, however, will be considered as belonging to the Sacramento and San Joaquin Valley areas and will be discussed in chapters relating to those districts. The southern half of the Sierra Nevada, as far north as Madera County, is composed entirely of granitic rocks. The central ana northern por- tions contain tlie altered sediments of the Bedrock series, together with their associated granites and the overlying gravels and lavas of the Superad.jacent series. The total absence of any of the oil-bearing forma- tions and the crystalline and metamorphie character of the rocks exposed, make the area of the Sierra Nevada an impossible one for the origin or accumulation of petroleum. PETROLEUM RESOURCES OF CALIFORNIA. 49 CHAPTER VI. Area of the S.acramento Valley, Ixclldixg the East Slope of the Coast Ranges and the Foothills of the Sierra Nevada. (Consists of the counties of Tehama, Glenn, Western Butte and Yuba, Sutter, Colusa, Lake, Yolo, Napa, Solano, Western Placer, Sacramento.) Tliis area will l)e divided into three districts and each discussed in more or less detail. (1) DISTRICT OF THE WEST SIDE OF THE VALLEY AND EAST SLOPE OF THE COAST RANGES. TOPOGRAPHY. Along the west side the l^at-lying lands of the Valley floor rise first to a mass of rather low rufr)33dD 3H0V0 sniH X3swndi 0) au900!|d nX?^ gun '^'HJnoO VdVN A3T1VA vss3xda3a i) a o O O 1^ X 1) I/) O o a CO 3 y a> in 10 I CO 54 CALIFORNIA STATE MINING BUREAU. able quantities. The two exceptions consist of (1) an anticline in the Chico sandstone running out from the foothills into the flat of the Sacra- mento Valley about three miles southeast of Vacaville. The axis of this fold, which strikes N. 45° W.. mav be followed from Sec. 3, T. 5 N., R. 1 AV., to Sec. 30, T. 5 N., R. 1 E. The dips of the flanlvs vary from 15° to 40°, (2) The Potrero Hills, four miles east of Fairfield, form an elongated dome in the jNIeganos formations. The axis of the dome strikes approximately east and west and may be followed from Sec. 6 to Sec. 11, T. 4 N., R. 1 W. The dips on the flanks vary from 10= to 20° and the plunge at the east and west ends is approximately 35°. Both of these folds, from a structural standpoint, are favorable for the accumula- tion of oil. POSSIBILITIES. Factors favorable for the accumulation and production of oil in this area are as follows: (1) The presence of oil as shown by seepages. (2) The presence of structures more or less favorable for the accumulation of oil in small quantities. (3) In the case of the anticline south of Vacaville and the dome* in the Potrero Hills, the structure is favorable for the accumulation in large quantities. Factors unfavorable are as follows: (1) The character of the forma- tion present (Cretaceous) is distinctly unfavorable for the formation of petroleum in an appreciable amount. (2) Faulting and tilting of the strata have caused a considerable percentage of whatever oil was originally present to run out and be lost. (3) The structure, due to sharp folding and faulting, is not favorable for the accumulation of oil in large quantities, except in the two cases aliove noted. Summing these factors up, it would appear that wells drilled along the axis of the anti- clines and faults (shown on Plate 5) should obtain showing of oil and, possibly, under the most favorable conditions, obtain small quantities of oil. "Whether these small quantities of oil which might be obtained would be of commercial value can only be determined by drilling. Due to the favorable structure and the large area of possible accumulation, the anticline southeast of Vacaville and the dome in the Potrero Hills may be considered as the most favorable locality to test out this district.^ Following is a list of wells, with the reported results. Tehama County. Unnamed well in Sec. 30, T. 23 N., R. 4 W., drilled to a depth of 2020 in the Chico ; showing of gas reported. Colusa County. (1) Unnamed well drilled in the NW3/:4 of Sec. 23, T. 20 N.. R. 5 W., about the year 1902 ; depth 2900 feet : located in a syncline in the Chico; show of gas and oil reported. (2) Williams Oil Company 'Brim Well, ' located in the SEi^- of Sec. 15, T. 15 N., R. 4 W. ; drilled to a depth of 2540 in the Chico; considerable gas reported. (3) AYilliams Oil Company 'Granger VTell.' located in the NEid of Sec. 18, T. 15 N., R. 4 W., on the axis of a faulted anticline; drilled to a depth of 600 feet in the Knoxville shales ; good showing of oil reported from 75 to 600 feet. (4) "Williams Oil Company well, located in the NE>^ of Sec 17, T. 15 N., R. 4 W. ; drUled to a depth of 1400 feet in the Chico: sliowine of oil and gas reported, (o") Williams Oil Company 'Mountain House WeU/ located in" the SE34 of Sec 18, T. 5 N., R. 4 W"., 'These two areas are now being tested by the Honolulu Consolidated Oil Co. PETROLEUM RESOURCES OF CALIFORNIA. 55 on the axis of a faulted anticline ; drilled to a depth of 1300 feet in the Knoxville ; good showing of gas reported at 1042 feet ; well still shows a small flow of gas. These" wells of the "Williams Oil Company were drilled between 1901-1909. (6) At the present time (April, 1921) the Moun- tain House Standard Oil Company is drilling a well in the NE^ of See. 18, T. 15 N.. K. 4 AV. A depth of 715 feet has been reached and a good showing of light oil is reported. (7) Unnamed well in NWi/4 of Sec. 32. T. 15 N.. R. 4 AV. : shallow-, still sliows small amount of gas. (8) Three wells are reported as having been drilled on Sand Creek, in Sees. 7 and S, T. 13 N.. K. 3 AV. ; reported depths were from 1000 to 1500 feet and sliowings of gas and oil were said to have been encountered, one well still showing a small amount of gas. These welLs are located approximately on the axis of an anticline in the uppermo.st Chico. (9) On the west side of Bear Creek, about one mile north of Wilbur Springs, several shallow wells were driUed near the contact of the Knoxville and Franeisean and close to the seeps that occur there. Showings of oil and gas were reported from these wells. (10) In the SWi/4 of Sec. 35, T. 15 N., R. 5 ^\., the Herron OilCompany sank a well to a depth of 1000 feet in the serpentine. At the present time a tunnel is being driven into the serpentine, just south of the Ilerron well, by the Blue Ridge Petroleum Company. Crevices in the serpentine have yielded as much as a barrel of light amber oil. As stated above this can be regarded only as a freak occurrence of petroleum. The oil undoubtedly migrated from the shales which are found outcropping a )out 500 yards east of the tunnel. (11) At the present time the Blue Ridge Petroleum Company is drilling a well in the SWJ^ of Sec 34, T. 13 N., R. 3 W. The well is located approximately on the axis of a sharply folded anticline. Yolo Count v. In the Capay Valley, about two miles west of the town of Capay, the Lincoln-Esparto Oilfields Company is drilling a weU, which is apparently located on the top of a dome in the lone formation. Con- clusive proof of this dome structure is, however, lacking. Solano County. In the NE^^ of Sec. 24. T. 5 N., R. 1 W., the Rochester Oil Company drilled a well, in 1901, to a depth of 1820 feet. Gas was encountered at 1520 and the well produced at the rate of 20,000 cubic feet per day for several years. In 19 J 9 the production was 8,000 cubic feet per day ; since then the production has steadily declined. The well is located on the axis of a well defined anticline in the Chico sandstone. In the SAVH of Sec. 13, T. 5 N., R. 1 W., about one- half mile northwest of the Rochester well and on the axis of the same fold the Honolulu Consolidated is now drilling a well. In the Potrero Hills, about four miles east of Fairtield, the Honolulu Consolidated Company is drilling a second well, which is located in the NE:^ of Sec. 9. T. 4 "X.. K. 1 AV. The well is close to the axis of a dome in the Meganos shale. In addition the following wells were drilled in the Cretaceous near Vallejo without obtaining an indication of petroleum: Tlie ]\lidas Oil Company, in 1914, drilled a well in Sec. 20, T. 3 N., R. 3 W, to a reported depth of 2000 feet. AY. Hauluth. in 1916. drilled a well in Sec. 4, T. 3 N., R. 3 W., to a reported depth of 1400 feet. 56 CALIFORNIA STATE MINING BUREAU. Napa County. In the Berryessa Valley, on the J. AV. Harris Eauoh, about seven miles north of ^lonticello, the Alount Shasta Oil Company drilled a well to a depth of 400 feet in the Knoxville and obtained showings of oil. In Sec. 25, T. 9 N., R. 3 W., the Fearless Oil Company drilled a Avell to a depth of 1475 feet in the Knoxville. obtaining a showing of oil at 270 feet. These wells were drilled in 1904. (2) DISTRICT OF THE VALLEY FLOOR. This district may be considered as embracing the flat-lying territory of the valley floor proper. The geological formations exposed are confined to small ar(!as in the Hooker Hills, Tehama Connty; the INIarysville Buttes, Sntter Connty and the Montezuma Hills in Solano County. These three gr ninpi? of hills are the only notable interruptions in the surface continuity of the flat- lying lands of the valley floor. The remainder of the district is covered by recent alluvium. The Hooker Hills are a small groui) of erosional liills. along the Sacramento River, about. five miles north of Red Bluff. The elevation is about 500 feet. A study of the topography of this region indicates that these hills are not due to any doming up of the strata, but rather they are to be regarded as an erosioual feature of the topograpll3^ They are a part of an old flood plain of the Sacramento River, which recent movements have elevated and the present-day streams have cut down to a new flood-plain, leaving the hills more or less isolated. Remains of this old flood plain may also be seen in the well defined terraces on both sides of the valley. The formations exposed are the Red Bluff and Tuscan Tuff formations. The Red Bluff formation consists of about 75 feet of coarse red conglomerate of Quaternary age. The Tuscan Tnff consists of about 500 feet of andesitic tuft' together with some con- glomerate beds and lava flows. Some of the tuft' is very fine, almost pumice and has frequently been mistaken for diatomaceous shale. While there is no direct evidence, the Tuscan formation is probably underlayed by the Chico sandstone. The so-called gas seepages that have been reported, are nothing more than iron oxide stain in the conglomerate beds of the Red Bluft' formation. Neither the structural conditions, nor the character of the formations are favorable for the accumulation of petroleum in these hills. The Tuscan Oil Company is at the present time drilling a well near Hooker station, in Sec. 25, T. 28 N., R. 4 E. The ]\rarysville Buttes in Sutter County are the most notable topo- graphical feature of the Sacramento Valley. They form a nearly circu- lar group of mountains with a diameter of about ten miles and rise from an elevation of about 100 feet at the valley floor to an elevation of 2000 feet in the central peaks. The buttes have been mapped in detail by the U. S. Geological Survey.^ and Dickerson- has recently described the sedimentary rocks that are found there, so no detailed description of the geology' is given herein. 'Folio 17, Marysville. Folio U. S. Geological Survey. =Dickerson, R. E. Eocene of the Marysville Buttcs-I^niversity of California. Bulle- tin of the Department of Geology. Vol. 7. PETROLEUM RESOUKCES OF CALIFORNIA. 57 The buttes consist of three rings of different formations ; an inner core of volcanic rocks, a middle v'mix of uptvn-ned sedimentaries consistino; of the Chieo and lone formations and fin;dly an outer ring of voleanic nuids and lavas. The sedimentaries of ("hico and lone age are made up mainly of tine sandstones and clay shales, with a thickness of about 1500 feet. Showing of gas has been reported from these sediments from time to time and in 1804 a well was drilled in the lone formations about one mile southeast of South Butte. A depth of twenty feet was reached and a small How of gas was encountered, which can still be observed. There is no reason, however, to believe that this gas is con- nected with petroleum deposits as there is apparently no formation in this region capable of forming oil. It is probable that the tilting up of the sedimentaries against the central core of volcanics has caused the marsh gas (CH4), which is present in varying quantities in practically all sedimentary formations, to collect in a noticcjiblo degree along the upturned edges of the C'hico and lone. There is nothing to indicate that there is sufficient gas to be of com- mercial value. The ^Montezuma Hills cover an area of about ten s(piai'(' miles in southern Solano County, lying along the Sacramento River at a point where it empties into Suisun l^ay. The average elevation is about 100 feet. The formations exposed consist mainly of soft clay shales, with- out distinctive strike or dip. The age is ])robably late Pliocene. Along tlic county road about a mile south of Denverton th(n-e are beds of conglomerate and voleanic ash, striking north and dipping 5° to the east. Just west of Rio Vista there are some sandy clay beds, strikinn' iiorth and dii)ping about 30° to the west. From these meager dips it would appear that the hills occupy a syncline in the middle of the great valley. The chief interest, however, lies in the fact that the diatomaceous shale (AFeganos) which outcrops in the Potrero Hills, probalil\' continues across Hcnvcrton slouuh and is jjresent l)enpath the Montezuma Hills. These shale beds, l)eiiig diatonuu'eous, may for-in oil. From a rough survey, the hills apparently have no structure that would be suitable as a reservoir for any oil that miglit l)e formed. However, they are worthy of being carefully mapped to determine if any favorable structure is present. The greater portion of the valley tloor, which is covered by recent alluvium, ott'ers no inducement for drilling. At the same time this territory can not be cnndemned outriglit. While it may contain no positive evidence of i)etruleum, neither does it contain evidence that oil is not present. The recent silt and alluvium of the valley tloor covers all evidence that might tell the tale. There always exists the possibility in cases like this tliat the fiat-lying lands may be underlayed by i)r()ductive folds.^ In the case of the Sacramento Valley, however, the character of the formations exposed on the edges makes it rather doubtful that any fold in the center of the valley would be pi'oductive. 'This matter of buried anticlines in tlif sreat valley is discussed in detail in Chapter XIII, Area of the Sun .loaquin Valley. » 58 CALIFORNIA STATE MINING BUREAU. (3) DISTRICT OF THE EAST SIDE OF THE VALLEY AND THE FOOTHILLS OF THE SIERRA NEVADA. The greater part of this distriet has been mapped more or less in detail by the United States Geological Survey and the detailed geology can be found in the following folios : Lassen Peak, 15 ; Marysville, 17 ; Smartsville, 18; Sacramento, 5; Placerville, 3; Jackson, 11. The oldest roel« exposed are known as the Bedrock series and con- sist of ancient schist, gneisses and slates, mainly of Carboniferous and Jurassic age, together with associated granitic rocks. These formations constitute the core of the Sierra Nevada and probably underly the greater part of the area under consideration. They are exposed on the surface within this district from a point near Oroville as far south as the American River. Structurally they have been sharply tilted and folded. The next oldest formation consists of beds of medium-coarse gray sandstone and sandy shale of Chico age (Cretaceous). The surface exposures of Chico are not extensive. They are found mainly in the deeper canyons of eastern *Tehama Count3% and northern Butte County, where the streams coming down from the Sierra Nevada have cut down through the flat-lying lavas and exposed small patches of the underlying Cliico. Roughly, these areas of the Chico formation extend from the head of the Sacramento A'alley as far south as Oroville. A small isolated patch has been recognized on the American River near Folsom. The Eocene is represented by the lone formation (Tejon) and con- sists of fine clays and shales, together with beds of impure volcanic tuflf. The lone is found as far north as AVheatland, Yul)a County, where small p^itclies of from 20 to 30 feet are exposed. Near Lincoln, in Placer County, the thickness increases to 100 to 200 feet and in Avestern Sacramento County, south of the American River, it attains its maximum thickness of nearly 1000 feet. In this district it lies upon the Bedrock series with marked unconformity except for a small area, near Folsom, Avhere it is found unconformably upon the Chico. The other Tertiary formations consist of beds of volcanic ash, known as the Tuscan Tuff (^Miocene) which is overlayed by andesitie and basaltic lava flows of Pliocene age. These voleanies cover the major portion of eastern Tehama and northeastern Butte counties. The tulf is found unconformably upon the Chico and has a maximum thickness of about 1000 feet. The lava flows are found more or less conform- ably upon the tuff and vary in thickness from 50 to 200 feet. The general structure of the Cretaceous and Tertiary formations within this district is that of a great monocline, dipping from 5'' to 20° to the west. The only area where these formations have been folded is found at Tuscan Springs, where, in a crater-like area of about 80 acres in extent, the Chico, Tuscan Tuff and lavas have been tilted up into a nearly circular dome. An examination showed that this structure is not due to compressive earth movements, but rather to the efforts of a batholitic mass of lava from the Lassen Peak range of volcanoes trying to force its way up through the overlying formations. PETROLEUM RESOURCES OP CALIFORNIA. 59 111 the vicinity of the hot mineral springs that are found here, shallow wells have encountered small amounts of gas. It is probable that this gas is of volcanic origin and is in no way connected with petroleum deposits. There is no possibility of finding oil in the lavas, Tu.scan Tuff, or Bedrock series. Apparently neither the Cliico nor tlie lone contain l)0(ls that would form oil, or structure favorable for its accumulation. AVliile tlicre have been occasional reports of seepages of gas and petroleum from this district, no authentic evidence of any oil or petro- leum gas has been found. 60 CALIFORN'IA PTATE MINING BUREAU. CHAPTER VII. Area of the Coast Ranges from San Francisco Bay as Far South AS THE PaJARO RiVER. (Includes the counties of Contra Costa. Alameda, San Francisco, San Mateo, Santa Clara and Santa Cruz.) Q'ho oil possibilities of this area will he diseus.sed by counties. Contra Costa County. The southwestern one-third of the county has been mapped in detail by Lawson.^ The Dej>artnients«of Geology and Paleontoloo^y of the University of California have carried on extensive investigations in the northern portions of the county and in the territory around Mount Diablo. Perhaps no other i)art of the Coast Ranges has been so well studied. Therefore no detailed geolouy will be given here. The strata exposed constitute a nearly complete section of the Coast Range formations from the Franciscan to the recent. Structurally these beds have been sharply tilted, folded and faulted into a large number of more or less independent geological areas. This has resulted in preventing any one fdrination from being continuous over a large area, which is an unfavorable condition for the accumulation of petroleum. Those formations within the county which contain beds that might form oil, consist of an area of Chico shales on the north side of -Blount Diablo: a small area of middle Eocene organic shales (Meganos) in the vicinit.v of Blount Diablo and finally an area of Monterey diato- maceous shale in the San Pablo and Rodeo valleys just east of the Berkeley Hills. However, none of these organic^ shale beds are con- tinuous over a sufficiently large area to form any great amount of oil. Indications of petroleum are found along the north side of Mount Diablo, about seven miles due south of Antio/h ; and in the S;ni Pablo Valley, east of the Berkeley Hills. The ]\Iount Diablo indications consist of small intennittent seeps of light green oil, found in the vicinity of Oil Canyon, Long Valley and Deer Valley. Roughly, the territory embraced by the s(^epages and wells that have found small showings consist of Sees. 13, 14, 15 and 23, T. 1 N.. R. 1 E. The formations exposed consist of beds of sand- stone and shale of the Chico, dipping in a monocline of about 65° to the north. Beds of Eocene age. overlie the Chico along the ridge north of Oil Canyon. Prospecting for oil in this distriet was first started in 1864, when several wells were drilled in either Sec. 13 or 14 to a depth of about 300 feet and encountered slight showings of green oil. In 1900 anotlier attempt was made and several more wells were sunk to shallow dei)tlis and ()])tained small showings. The last well Avas drilled by the Atlas Development Companv in 1918 on Oil Creek, in the SE14 of* Sec. 15, T. 1 N., R. 1 E. A depth of 1823 feet was reached and as no showings of oil were encountered the well was abandoned. 'U. S. Geological Survey. San Francisco folio 193. By A. C. Lawson. PETROLEUM RESOURCES OF CALIFORNIA. Gl About 15(H) feet up tlic cjiu^dii and due cHst aloiiir the strike of the formation from the A this well, is an old hole known as the Harding welk This was drilled to a depth of 978 feet and encountered green oil from 950 to 978 feet. It is now used as a water well and shows about 1 (piart of green oil per day. There is no reason to believe that future drilling in this region would show any better results than the former attempts. Indications in the San Pablo Valley consist of seepages of heavy black asphaltic oil found in the vicinity of Lauterwasser Creek and in the lower end of the valley about 2 miles east of the town of San I'ablo. A detailed geological map of this territory can be found in folio 19.T and Arnold gives a brief description of the geology and development in liulletin 'M)i.'- The sti'ucture in the vicinity of Lautci-wasser Creek consists of a I'ather sharply folded anticline pluniring to the southeast and truncated at the northwest end by a fault. The oil has collected in tiie sandy beds of the Orinda formation (Pliocene), having been formed in the underlying diatomaccons shale beds of the [Monterey series, which at this point are about 800 feet thick. Beginning in 1889 and continuing up to 1900, eight wells were drilled on this structure, the depths ranging from 500 to 2700 feet, all encountered showings of oil and gas, but none showed suilfieient quantities to be of commercial value. At the lower end of the San Pablo Valley about three miles east of the town of San Pablo, five wells were drilled to 1900 feet along a syncline in the Orinda for- mation. Slight showings of oil were encountered, but nothing of commercial value was devehsped. The oil has apparently collected in the sands of the Orinda formations from the ]\Ionterey diatomaeeous shale, which outcrops to the east on Sobrante Ridge. Neither the geological conditions nor the results of wells drilled warrant any further attempts at development in this area. Alameda County. The northwestern portion of the county'' and the area around Tesla and Altamont* have been mapped by the United States Geological Survey. The formations exposed within the county consist of Franciscan, Cretaceous and a nearly complete section of the Tertiarv sedimentaries, together witli numerous lava Hows of Pliocene age. The Franciscan is found in the extreme southeast corner of the county and in a long narrow strip along the west side of the Berkeley and San Leandro hills. It also is probably present beneath the alluvium of the flats that border the east side of San Francisco Bay. The Cretaceous, con- sisting of typical Knoxville shales and Chieo sandstones, is found over- lying the Franciscan in a rather broad area near the top of the western slope of the Berkeley and San Leandro hills. Other areas of Creta- ceous arc found in the hills south of Livei-more and in the vicinity of Altamont and Tesla. 'United States Geological Survey folio 193. By A. C. Law.son. =R. Arnold. Miner Ranch Oil Field. Bulletin 304. U. S. Geological Survey, 1907. Pages 339-3 42. ^San Francisco folio 193. By A. C. Lawson. ^Bulletin 603. By Anderson and Pack. 62 CALIFORNIA STATE MINING BUREAU. The Tertiary in the western i)()i-tion of tlie eonnty eonsists of the Monterey series, together with ihe Pliocene seclimentaries and lava Hows. In the eastern portions Ihci-c are outcrops of Eocene, upper Miocene and Pliocene beds. The .Monterey series in the Berkeley and San Ijeandro hills contains diatonnu eons shale but not in sufficient quantities to form any notieeal)le (juantities of petroleum. The only indication of oil in the county is found in the vicinity of Tesla. There are seepages of light-gravity oil in sandy beds of Miocene age. The seeps are best exposed on the Hamilton Ranch in the vieinity of Sec. 15, T. 3 S., R. 3 p]. It is very probable that the oil was formed in the underlying Chieo and migrated into the sandy beds of the ]\Iiocene. The (Miieo in this vicinity is known as the Moreno forma- tions and consist of purplish shah's containing organic, nmterial. It is l)est exposed along the south side of ("ori-al Hollow, between Tesla ami Carnegie. Altogether seven wells have Iwcn drilled in this area, Hve on Sec. 15, T. 3 S., R. 3 E., and two by the Standard Oil Com- pany, near Altamont. The wells on See. 15 reported small showings of light oil, those at AJtamont obtained no indications. In 191-1 C. A. Waring^ wrote a brief description of this area and in 1915 R. Anderson and R. Pack made a detailed survey-,- giving a complete description of the geology, development and possibilities, together with an areal map. Anderson and Pack's conclusions are as follows: "In conclusion, it may be said tiiat the probability of obtaining a large quantity of oil in tlie Tesla district is remote, but that wells producing a little liglit-gravity oil may possibly be obtained in very small areas. Such wells may derive their oil either from sandy beds in the Cretaceous or from the lower beds of the unconformably overlying Tertiary, the latter offering the better chances. The areas whicli offer some Inducements for drilling are a narrow strip along the soutli flank of the anticline which trends east through the hills north of Tesla, where the dip of the oeds steepens abruptly, and an area of low dips at the east end of tliat anticline, where the surface is formed by the slightly dijiping undifferentiated Miocene and San Pablo formations. Outside of these two areas the possibiUty of obtaining oil seems very poor, and tlie writers believe that drilling in other localities will prove a waste of money." San Francisco County. The county of San Francisco is covered entirely by beds of sand- stone and chert, together with intrusive masses of serpentine and basalt, all of the Franciscan formation, and otfering no possibility of producing oil. San Mateo County. The geology of the county has been described and mapped i-n detail by Lawson'' and Branner.* The area north of Halfmoon Bay may be considered as offering no possibilities for oil, the formations consist for the most part of the Franciscan, together with a granite area in tlie vicinity of ^lontara Mountain. The only area of Tertiary sedimentary consists of a narrow strip of Merced (Pliocene), running southeast from a point on the coast near the San Francisco County line to ^Milbrae on the bay side and a small area of ^lartinez (P^ocene) in the San Pablo Valley. 'Bulletin G9. California State Mining Bureau, i;il4. Pages 439—1-10. -U. S. Geological Survey. Bulletin 603. By R. Anderson and R. W. Pack 1915 Pages 186-194. 'U. S. Geological Survey. San Francisco folio 193. By A. C. Lawson. *U. S. Geological Survey. Santa Cruz folio 1G3. By J. C. Branner. PETROLEUM RESOURCES OF CALIFORNIA, 63 « In the area smilli oi' HiiU'monn l'>lained by the fact that the ])asal l)eds of the Monterey siiale have been intruded 1)\- basaltic and diabase dikes. These igneous dikes have undoubtedly ciaised destructive distillation of the oil, with the result that a heavy residtiiuii is found near the intrusion and the lightt'r constituents are found in tin; overlying Purisima beds. 'i'lie pi-incipal seepages are found along Purisima Creek, Tjol)itos Creek and Tunitas ('re(^k ami are in beds of the Purisima formatioiu There are also several seeps on brandies of San (fregorio Creek. On Purisima Creek, fourteen wells have been drilled since 1880. Seven of these are reported to have obtained production varying from ten to thirty barrels. At the present time tliree wells are pi'oducing, yield- ing about one barrel per well per day of 50° oil. These are known as the T. B. Wilkensen wells. Tlie average depth is about 700 feet and they have been drilled entirely in tlie Purisima beds, on a west dipping monocline of about 30°. The same conditions exist on Tunitas Creek, where seven wells have been drilled, all .reporting small showings. A distillation of the oil shows it runs 70 per cent gasoline. The possibilities may be summed uji hy saying that in the area down the dip fi-om the seei)ages mentioned above, small wells of light oil can probably be obtained, whether these would be sufficiently large to be of commercial value can only be told by actual drilling. Any devel- opment work should be guided hy the geological conditions as shown in U. S. G. S. folio 163. Santa Clara County. The topograpliic features of Santa Clara County consist of the Santa Clara Valley running north ami smith through the center of the county, with the Santa Cruz ]\Iouiitains bcn-dering it on the west and the Diablo Kange on the east. The southwestern portion of the county lias l)een majiped by the U. S. Geological Survey.^ The formations of the Diablo Range within this area consist mainly of Franciscan beds. On the western edge of the range, east of San Jose and the ^Mission San Jose, there are outcrops of Cretaceous and Tertiars' which may underly the Santa Clara Valley at this point. The valley proper is covered with recent alluvium. On the western edf'e of the valley, the Santa Clara formation (upper Pliocene) consistin<>- of sands and gravels and clays, is found outcropping. BeneatJi the 'U. S. Geological Suivey. Santa Ciuz folio 163. By J. C. Branner. (54 . CALIFORNIA STATE MINING BUREAU. Saiitii ("lara and forming tin- coiv of tlu' Santa Cni/ .Mountains at this point are Ix-cls of the Franciscan formation. Along the western edge of the county whidi is pi-actically paralkd to the top of the western slope of the" Santa Cruz Range, is a long narrow belt of Tertiary running the entire length of the county. The nortliern portion of this belt is made up of Oligocene, Vaciueros and ^Monterey beds. South of Loma Prieta, it consists mainly of Monterey shale, which continues as far south as the Pajaro River, wliere it turns east, crosses the range and finally dips und( r the Pliocene beds of the Santa Clara Valley at Sargent. Oil indications witliin the (-(lunty ai-c limited to the following areas: (1) Moody (lulch. (2) Los(Jatos. (;i) Sargent. (1) Moody (;ulch is in a westerly branch of i.os Catos Creek about two nules south of Alma. Tlie gulch may be entered from the main county road from Santa Cruz to Los Gatos. Fig. 5 shows the general structure of the region and the formations that outcrop. The oil probably formed in the diatomaceeus shales of the Monterey and then by reason of tlie fault .contact has migrated into the porous sands of the Vaqueros and San Lorenzo formation. Drilling was first started here in 1880 and all together about 85.000 barrels of oil have been shipped from the Gulch. The wells drilled numlier about Ifi, and the average depth is about 1200 feet. The gravity of the oil is -45° Baunie. The reported yield from the old wells varies from ten to forty barrels. Operations cea.sed about 1910, but recently the Trigonia Oil Co. has taken over the property containing the old Logan and Moody wells and is starting up operations again. The conditions that exist in the Gulch probably extend for a mile or so both to the northwest and southeast. It is proljable that with careful management the area around the Gulch could l)e nuuh^ to produce small wells of commercial value. (2) Los Gatos. Following is a report by C. A. AA^aring^ of this region : "The Santa Clara Valley region east of Los tJato.^; is covered with alluvial gravel, sand and soil so that the underlying formations are completely concealed. From wells driiled in the region it is evident lliat this land is underlain Ijy rocks of the Monterey series which carry some oil. "Drilling for oil has been carried on near the reservoir of the San Jose Water Company, on the San Jose road two miles northeast of Los Gatos. Oil indications were first noticed on the ranch of Mr. R. C. McPher.son in an S.5-foot well. "Four wells have been drilled in the locality. At two of these the rigs are still standing but no operations are at present being carried on. In a 1600-foot well back of thv' barn on the property of Mrs. H. H. Main, gas may be seen bubbling tlirough oil which fills the casing. Some oil is said to have been bailed from this well for use as fuel by the owners. A well on the soutli side of San Jose road is said to have been drilled 2530 feet deep, and to have pierced three oil strata." In 1918 the Traders Oil Company drilled two wells, but failed to obtain a commercial production. AVell No. 1 was drilled on the :McGrath Ranch to a depth of 200(1 feet and well Xo. 2 was located on the San Jose road near AValker avenue and reached a depth of 2675 feet. .^ , As stated above, it is i)robable that the region is underlaid by ' Monterey shale containing a little oil, but the presence of Franciscan rock on both sides of the valley restricts the shale to such a small area that production on a commercial scale is doubtful. 'State Mining Bureau. Bulletin 69, 1914, page 470. PETROLEUM RESOURCES OF CALIFORNIA. 65 4^ ^3ajo so;e9 vavio viNvs 031VW NVS //^^ 3 a O -a o o a o 5—13322 G6 CALIFORNIA STATE MINING BUREAU. (3) The Sargeut Ranch fiekl lies approximately in T. 11 S., R. 3 and 4 E., about three miles west of the railroad station of Sargent. The principal development has taken place along La Brea Creek. The formations outcropping are the Franciscan, ^Montere}' sandstone and shale and Pliocene sands and clays. The oil originated in the diato- maeeous shales of the ^Monterey and has collected in sandstone beds of the same formation. The Franciscan is found outcropping on the hills to the north of La Brea Creek and is overlaid by the Monterey formation which lies in the form of a crescent dipping at about 45° to the southeast. Westward the Monterey continues as far as a mile west of the Santa Clara-Santa Cruz County boundary, where it is truncated by the San Andreas fault. In its soutliward extension it is terminated by a fault along the Pajaro River. On the lower portion of La Brea Creek and in the hills just west of Sargent, the ^Monterey dips under the sandstones and shales of the Purisima. These later beds are dipping at an angle of 45° to the south. In the Lomas ]\Iuertas, soutli and east of Sargent, there are beds of sand and clay probably of upper Pliocene age. The axis of a small anticline runs southeast up the canyon -just east of Sargent Station and finally flattens out into an east dip which is the general inclination of the strata in the Lomas Muertas. There have been about twenty wells drilled along La Brea Creek, all ol)tained a showing of oil. Those which have pro- duced on a commercial scale are located about two miles up the creek from the state highway. The average depth is about 1500 feet aud the oil is obtained from sandstone beds on a monocline in the ]\Ionterey. The gravity averages about 18° Baume. At the present time the AVatsonville Oil Company is operating nine wells with a total production of 75 barrels per day, which is apparently the maximum yield of the field. On Pescadero Creek and near Chit- tenden, a number of shallow wells were drilled obtaining small show- ings of heavy oil. Due to the fault contacts on the west and south and the serpentine contact on the north, there is no hope of extending the field in those directions. On the ea.st the oil-bearing sand of the Mon- terey dips so steeply nnder the Pliocene beds, that the chance that they would be within reach of the drill is doubtful. On the axis of the anticline just east of Sargent in the Lomas ^luertas (San Benito County) there is a possibility that these beds may be reached by drill- ing. The Shell Company is at tlie present time drilling a prospect well here. Santa Cruz County. The area lying north and west of the town of Santa Cruz has been mapped in cletail by the U. S. Geological Survey,^ and it is in this portion of the county that the principal indications of petroleum occur. Briefly, the geology is as follows: In the area around Ben Lomond ^fountain, running from Little Basin to the town of Santa Cruz, the formations consist of granitic rocks, together with areas of ancient crystalline schists. In the region to the north of this crystalline area there are outcrops of the San 'U. S. Geological Survey. Santa Cruz folio 163. Bv J. C. Branner. PETROLEUM RESOURCES OF CAIJFORNIA. 67 Lorenzo ft)niiatioiis, tlio \'a° Baiime) specific gr.ivity, and tliat about 5 barrels a day of tliis oil was pumped out witli a liand pump for several days in succession. Several wells were drilled in tliis vicinity to sliallow deptlis many years ago, but llie amount of oil obtained was sm;ill and tlie wells were abandoned altliough a man was kept tliere to look after tlie property. "Below the horizon of the seeps the purple shale is impregnated with oil tlirough a thickness of many luindred feet. The shale is aliout 1000 feet thick and is oily practically throughout. It contains a number of large Ic-nses of fine-grained gray and yellowish sandstone much like that typical of the concretionar.v members beli)w and above, and these lenses mi.glit be expected to form local reservoii's for the oil at depths. The shale, as usual in rock of this type is crushed and distributed, but the general structure is that of a monocline dipping about 4.5° S. The concretionary sandstone of the Martinez (?) immediately overlies tlie shale, and signs of its being slightly impregnated witli oil at the very base were noted locally. "The conclitions liere are very much the same as in the area of the siliceous shale in the Kreyenhagen and Vaqueros formations on the south side of the valley, already described. It is probable that a small production which might assume economic importanc-e at some future time, in view of the good quality of the oil, would result from drilling operations in the shale of the Mon no formation here, but the prospect does not seem alluring under present conditions. It is not unlikely that oil might be found locally in sandstone lenses entirel.v sealed within the sliale "There is also the possibilit.v of wells obtaining oil from the lower part of the sandstone that overlies the shale, and if serious drilling (jperations were to be commenced the logical jjlace to start would seem to be at a point south of the outcrop of the Moreno, where the base of the sandstone and top of the shale would bo reached at a depth ot at least several hundred feet It is believed, however, that the steep dip, the unifoi-m monoclinal structure, and the dissemination of the oil througli so great a thickness of beds precludi' the hope that the Moreno and the Martinez ( '.' ) formations will be found commerciallv productive in the near future The area to which these conclusions apply lies in the NJ Sec. 19, the S' Sec. 18, T, 16 S., R, 11 E., the N'E.t Sec. 24, and the SJ Sec. 13, T. 16 S., R. 10 E. Farther east tlie purple shale of the Moreno formation is reduced to a thin zone, and in that direction the outcrop of the shale itself does not afford promising territory for the production of even a small amount of oil What possibility there may be in tliis area farther east for oil gathering from below into the concretionary sandstone overlying the shale can not be forecast, but it is unlikely that any important quantity gathers there. In a westerly direction the area above outlined extends to Griswold Canyon, the western limit of the region studied. The same steep monocline of the Cretaceous and later beds continues westward from Griswold Canyon along the north side of the valley of Pimental Creek. "As the structure of the Vafpieros formation is very similar to those .iust described, and as there is no good surface sign of petroleum in it or in the Krey(>nhagen shale, the chances for oil in this upper zone .ippear even slighter than those for oil in the lower zone, along the western half of the north (lank of the syncline. At one point about a mile east of Griswold Canyon an oily appearance was oljserved in the Vaqueros formation and a faint petroleum odor obtained This was just enough to indicate tiiat the slighll.v petroliferous character of this formation persists this far west. One well — that of the Sussex Oil Co. — was drilled in this region between 1910 and 1912 It is situated near the center of Sec. 30, T. 16 S., R. 11 E. It started in the steeply dipping clay and gravel beds of tlie Jacalitos and Etchegoin formations and is reported to have been drilled a little deeper than ISOO feet and to have obtained signs of oil and gas before operations were stopped At this depth it had probably readied the middle portion of the Vaqueros, but it could not have gone as far as the base of that formation, which should have been reached in order to make an adequate test. "It should be noted, as having a possible bearing on the question under discussion, that an intrusion of basalt occurs at one place on the north side of the Vallecitos. It penetrates the formations at least as far up as the summit of the Vaqueros sand- stone and shale. The liasalt outcrops about two miles north of the divide between the two arms of the Vallecitos, as a small intrusion p;irallel to the bedding near the contact of the Vaqueros with the overlying Jacalitos and Etchegoin formations. It is the onl.v known evidence of igneous ;ictivity later than Jurassic or eaily Cretaceous in a wide stretch of county south of Panoche Creek and east of Griswold Canyon. Owing to its local nature it is very doubtful if it has seriously affected the oil-bearing character of the beds, except in its immediate vicinity. "East Half of North Flank of the Vallecitos. "The problem to be considered in the area along tlie eastern portion of the north Hank and around the east end of the fold differs from that presented by the more westerly area, owing to the lower dip in the Tertiary beds and the presence of signs of oil in them The Moreno and the formation immediately overlying do not assume much importance here, owing to the lack of seeps, as well as to the continuation of the unfavorable structure of the area farther west. Very likely 74 CALIFORNIA STATE MINING BUREAU. these beds contain a little oil rlisseminated tlirough them, but unlrss some as yet unsuspected evidence should bo brought to light, it seems foolish to spend money- drilling to or into the Moreno formation here. "Structural conditions, although not highly favorable, suggest that oil may have collected in the Vaqueros. in the northea-stern part of the Vallecitos. This formation, moreover, shows undoubted indications of oil. The area has certain points of resemblance to the Westside field, which make it worthy of careful consideration. Tlie Vaqueros formation here is the same formation as that containing the main oil sands of the Coalinga district and consists of similar porous sands. It overlies imconformably the siliceous Kreyenhagen shale, the supposed original source of the oil. just as it does at Coalinga. It lies in a gently dipping monocline on the flank of a synclino, as in the Westside field. It shows at least in one place at the surface signs of petroleum only a little less pronounced than those in the Coalinga field, and it is overlain here, as there, by relatively impervious clay and shale. The main dilTercnce from the Westside field is not one of local attitude or character of the beds but involves a consideration of the broader structural relations, which are perhaps of greater importance than the similarities above mentioned and will be discussed in the final paragraph of this section (p. 177), where conclusions regarding the possibility of this area and of the Vallecitos as a whole will be expressed. "The outcron of oily sand above referred to occurs on Silver Creek in the basal beds of the Miocene, where they rest on the truncated edges of the slightly more steeply dipping Kreyenhagen shale. The locality is on the northeast edge of the Vallecito.<5. in the western part of the SWJ Sec. .5, T. 17 S., R. 12 E.. just east of the New Bedford well. The same beds show slight evidences of being oily .at other points along the outcrops to the northwest, but not sufficiently so to prove the existence of a considerable petroleum reservoir. "Tlie Vaqueros contains beds of hard sandstone that may easily be traced along their outcrops, because tlicy form the first high ridge parallel with the Vallecitos on its nortli side. The formation is 700 or SOO feet thick and consists of a lower zone about 100 feet thick of variable sandy, gr.avelly, and shaly beds, an overlying zone about SO feet thick of siliceous diatomaceous shale, and an iipper portion over .500 feet thick composed chiefly of sandy strata with some interbcdded shale and containing two prominent beds of hard sandstone in its centr.al p.art. each about 100 feet thick. ("See the tabulated section on p. 86.) The lower sandy zone has the thickness and lithologic qualities that would make it an excellent reservoir were oil present in large quantity. Furthermore the overlying flinty shale ought to serve as an imnervious cap to prevent the oil from rising into higher beds. The escape of the oil along the bedding planes would he hindered by the lowness of the dip and by the tendency of the oil to seal itself in by the deposition of solid residue near the surface. The monoclin.al dip of the "\'aqueros formation within .about a mile west of Silver Creek is slightly variable, but on the average it is only from 3° to 8° toward the southwest. Locally there is a tendency toward flattening, affording small wrinkles that might be a factor in helping to hold oil. The dip of the monocline is sufficiently low to make the basal portion of the Miocene beds accessible within a reasonable depth, even as far out as the axis of the Vallecitos syncline. "About 2 mi'es west of Silver Creek there is an abrupt steenening of dips in the Miocene formations along the edge of the valley to 20°, 30° and finally 4.5° or more. For sever.al miles beyond the beds preserve a low dip on the very summit of the ridge, but they fold over abruptly into the steep dips on the south side. The steepness of these dips, combined with the lack of evidence of any appreciable quantity of oil in the beds, would seem to leave little basis for expecting them to be commercially productive west of the very small area of low dips at the east end of the north flank, already described. "Around V^e east end of The Vallecitos the Tertiary b?ds are brought to the surface from h°neath the valley by the rising end of the syncline and occupy crescent- shaped belts that curve aroimd the end of the valley. The dip of the beds is everywhere toward the valley and varies between 5° and 30°. The structure is not of tiie most favorable type for the .iccnmulation of oil, and yet it is such that a certain amount of oil would be expected to accumvilate if .any existed in the beds. The shale of the Vaqueros lies unconformably upon the Kreyenhagen shale, as in the Coalinga f^eld. and if oil were present in the shale, it shovild rise and collect in the sandy strata overlying its truncated edges, making itself apparent at the outcrop. No seeps or other surface signs of oil were discovered east of San Carlos and Silver Creeks, but this does not prove that they do not exist, for the beds are locallv masked by terr.ace deposits. "The following wells have been drilled in the area under discussion : The New Bedford Oil Co.'s well, in the NE. i SE. J sec. 6. T. 17 S., R. 12 E. : the Vallecitos Development Co.'s well, in the NE. } sec. 12. T. 17 S.. R. 11 E. : and the Range Ifi Oil Co.'s well, in the SE. J. sec. 3, T. 17 S., R. 11 E. The New Bedford well is situated just west of Silver Creek, near the outcrop of the oil sand above mentioned. It starts in the basal portion of the Vaqueros .and passes through the oil sand that outcrops on Silver Creek at a depth of only about 100 feet, but obviously it is too near the outcrop of the oil sand of the Vaqueros to obtain .any production from it. Prac- tically the whole depth drilled, which is now reported as more than 3000 feet, has been below the oil zone of the Vaqueros, the zone in which oil shoiild be sought for in this district. At about IfiOO feet this well passed through a 6-foot bed of coal in white sand, evidently coal-bearing white sandstone of the Tejon. Oil is said to have been struck at a depth of about 1700 feet, but it has not been possible to s\ib- stantiate the report. At a depth of 3000 feet, the well should be in the midst of the Martinez (?) formation, which is here very thick. It would probably require a depth of at least 1000 feet more to reach the possibly oil-bearing beds at the top of the Moreno formation. PETROLEUM RESOURCES OF CALIFORNIA. 75 "The well of the Vallceitos Development Co. was started in 1910 on the terrace a mile north of John Ashiirst's place. It started in the lower beds of the Jacalitos and Etchegoin formations, where tlie s.vnclinal flank has a low dip, and was excellently placed to test the possibilities of the zone at the base of the Vaqueros. Definite infor- mation regardinK the results obtained are not available, but tlie well is reported to have gone to a depth of over 2,000 feet, or entirely through the Vaqueros, and to have found some oil at tlie base of this formation. The tools brought up from the bottom were said to be covered with oil. F'rom the fact that the well was practi- c*ill.v abandoned in 1911 the writers infer that it did not prove a success. "The Range 16 Oil Company's well is situated over two miles farther northwest and starts in the midst of the .Jacalitos and Etchegoin formations, on a part of the synclinal (lank wliere the dip is steeper than farther east. It was drilled in 1 010-11 to a depth of 2.300 feet, without obtaining oil in any important quantity. At tliis depth the well must have neai'ly if not riuite readied the base of the Miocene series. ''Conclusions Regarding the Vallecitos District. "Consideiing only the evidence obtainalile from a surface stud.v, the area described in the paragraphs just preceding — -that is, the east end of the north flank and the curving east end of the syncline — seems a faii'ly promising place to search for oil and tlie most promising portion of the Vallecitos district. The amount of oil that comes to the surface at various points in The Vallecito.s, and the resemblance of the stiaicture in the east end of the valley to that of the Westside field, make it not unreasonable to suppose that oil may have collected here in fairly good quantity. This conclusion was expressed in the preliminary report on the Cantua-Panoche region.' That report was prepared before any wells had been started to test the sands in the Vaqueros formation at tlie east end of The Vallecitos, and it suggested a small area at that end of the valley as offering a reasonal)lo location for the drill- ing of a test well. Such a test has subsequently been made by the well of the Vallecitos Development Co. before mentioru'd. and, altliough it has not been possi'ole to ascertain defmitel.v the results obtained in this well, numerous indications point to its having l)een a failure. The writers believe it likely that below the surface the Vaqueros formation does not contain as mucii oil as one might be led to believe by a comparison of tlie surface evidences of oil in this region with similar evidences in regions that have been fomid highly productive. As stated in the preliminary report, the drill alone can determine with certainty whether oil exists in paying fiuantities in the beds which at the surface show traces of oil. Tlie opinion at present held liy the writers is based on the apparently unfavoralile evidence afforded on this point b'y the well previously referred to, and on a more general consideration of the condi- tions governing oil accumulation along the western border of the San Joaquin Valley or from any other outside territory tliat might be trilmtary to its oil and water supply points to tlie prolialulity that no very important peti'oleum accumulations are to be looked for in this valley. The writers would not recommend the expenditure of any mone.v in further attemnts to olitain paying quantities of petrohHim anywhere in the Vallecitos district, until the value of oil has increased or the expense of operating decreased to such a point that risks could be taken for the sake of obtaining occa- sional very small producing wells. "Crest and Flanks of the Ciervo Anticline. "The Ciervo anticline is an oblique offshoot of the main structure of the Diablo Range, similar in type to the Coalinga anticline. It is probable that in the past history of the region, in late Tertiary or early Quaternary time the summit of the anticline was covered throughout areas many square miles in extent by the Tertiary formations and that oil accumulated in large quantities along it. During the course of time, how- ever, the oil-bearing formations, together with their stores of oil, liave been worn awav from the ma.ior portion of the antiiline, leaving the underlying unproductive sandstone of the Panoche formation (Upper Cretaceous) exposed in a wide belt on either side of the axis. Tlie only place where beds as young as the lower oil-bearing zone of this region remain over the axis of the fold is at its east end, where it plunges steeply and merg( s with the monocline of tlie foothills. At this place it is covered by shale of the Moreno formation, the overlying concretionary sandstone and clay shale of the Martinez (?) formation, and the succeeding Tejon formation. The area embracing this end of the anticline is the one which will be discussed here. "The structure of this area is similar to that of the plunging end of the Coalinga anticline, which has proved so productive, and the chance for the presence of oil here deserves careful consideration. The most important differences between this area and that on the nose of the Coalinga anticline are as follows: The Ciervo anticline is not so extensive a fold as that at Coalinga. It stops short without reaching the San Joaquin Valley and plunges abruptly without affecting strongly the Tertiary beds of the foothills, whereas the Coalinga fold continues on for many miles into the valley with a perfect cover of Tertiary formations. On the Ciervo fold only one of the shale formations of organic origin (the Moreno, Upper Cretaceous) is present and the evidences of oil in this formation are not pronounced ; on the Coalinga anticline the two oil-bearing shale formations are present, and both give at their outcrops unmistakable evidence of their petroliferous character. Moreover, on the Ciervo fold the Moreno formation outcrops ,iust at the point where the fold plunges steeply to its termination, instead of continuing along the axis at a relatively low and constant dip beneath tlie later formations. These differences are all unfavorable to the Ciervo area when its possibilities of yielding oil are compared witli those oi the Coalinga fold. They lead to the conclusion that the Ciervo area, if productive at 'Anderson, Robert. U. S. Geol. Survey, Bulletin 431. Pp. 76-77. 1910. 76 CALIFORNIA STATE MINING BUREAU. all, will be very much less so than thf Coalinga anticline. Owing to the limitation as regards possible oil-bearing formations on this fold, the proper comparison to be made is witli tlie Oil City field and with the sands in the Martinez (?) and Tejon formations in tlie Coalinga district. The result of this comparison is likewise unfav- orable to the Ciervo field, and yet there is enough similarity to suggest the possible existence of a commercial quantity of oil here. "Tlie purple shale of the Moreno formation is exposed in an area of several s(iuare miles near the axis of the Ciervo anticline in Sees. 14, 1.5, 21 and 23, T. 16 S., R. 12 E., and passes beneath later beds along the summit of the fold in the SWJ Sec. 24, the NWJ Sec. 25 and the NJ Sec. 26 of the same township. The area near the summit of the fold in which the shale of the Moreno would be within reach of a drill or at a depth of not more than 3000 feet below the surface is approximately- outlined by a red line on the geologic map (PI. 1). Several doubtful factors, such as abrupt variation in thickness of the different formations and uncei'tainty as to the attitude of tlie beds, make the drawing of such a line difficult, and it is shown merely for the purpose of giving a rough indication of the more important part of the area here under discussion. "If any appreciable ciuanlity of oil is present in the Moreno formation the condi- tions of structure in this area make it probable that productive wells could be obtained by drilling down to included lenses of sand, or to the sandstone beds that overlie the shale. "Mention has previously been made (in the section dealing with oil indications in the several formations) of the oily sands discovered at certain places in the Moreno formation near the axis of the Ciervo anticline. In addition the shale gives the appearance of having been thoroughly impregnated witli petroleum. It is characterized by the blackish-brown discoloration and strong sulpliurous odor that seem to result from the presence of oil in shale of this type in many places. The oil sands easily escape notice owing to the weathered nature of tl;e exposures, but tiie appearance of fresh specimen^ of the rock leads' to the belief that a lar.ge part of tlie formation has previously been and may still be soaked with oil and tliat a considerable amount of free oil might be found in the beds at greater depth, away from tlie surface zone of weathering and evaporation. The light oil found in the purple shale at Oil City and at the Union wells, north of the west end of The Vallecitos. wliich appears to be f haractei istic of this horizon, is of a type that would not be expected to leave at the surface as marked evidences of its presence as the asphalt oil in the Miocene formations of the Coalinga district and other parts of California. "If the formation contains as large an amount of oil as is believed, the question remains whether the oil is too widely disseminated through many hundred feet of beds to be obtainable in commercial quantity, or whether some of it has accumulated in reservoirs that may be profitably tapped. There can be no doubt tliat a large amount has been lost by dissemination thi'ough the beds and esc^ipe at the surface, as is attested by the prevalence of the oil discoloration throughout tlie formation. But it is an important fact that thick lenticular beds of porous, fine-grained sand wliicli ought to be good reservoirs are included in the shale, and it is higlily probable that much oil has been absorbed by these lenses and retained in them. The lenses are not confined to any particular part of the shale but occur in its upper as well as its lower portion and would be found somewhere witliin the shale in any section tliat might be made of it. Some of the lenses attain a thickness o"' 100 feet or more. The body of oil-bearing beds of which the purplish shale is the chief eonstituent is likewise overlain by sandy strata in whjeli, it might be exoected, oil would accumulate. Wells drilled through the later becls at a considerable distance from the outcron of the purp'e shale would probably reach the shale and its included sands at a depth at which the petroleum contents would be sealed in and preserved intact. A good situation for a test well is about 2 miles northwest of Ciervo Mountain.' "The dip of the beds in the Ciervo Mountain region is low and the structure is undulating, and it is not impossible that some of the minor folds might aid in the concentration and confinement of a local body of oil. In this connection it is worthy of note that a number of small faults in the Tertiary formations in this region have not brought to light any oil through seepage ; but in the opinion of the writers this fact does not carry great weight as against the favorable conditions mentioned. The conclusion is that the area on and ad.iacent to the Ciervo anticline offers possibilities that should be tested. It is believed that a well drilled near the summit of the anticline, as sugested. would liave a chance of obtaining a light oil In paying quantity, but the risk of failure would be great and the likcliliood would be of a small production, if any, being obtained. This much, at least, may be said — that the conditions are mucli more favorable than those in many places where 'wild-caf wells are being drilled in C;ilifornia outside of the developed fields. The Extreme Southwestern Portion of the County. This area consists of the territory south of the town of San Benito and includes the upj^er portions of the San Benito Valh^y and the areas around Toro Creek. Bitterwater Creek and Lewis Creek. 'Since the publication of the above report the Standard Oil Company drilled a well in Sec. 25, T. 16 S.. R. 12 E., about 3 miles northwest of Ciervo Mountain and about a mile east of the San Benito County line in Fresno County. A depth of SS69 feet was reached and no indications of oil were encountered. PETROLEUM RESOURCES OF CALIFORNIA. 77 The (liuniiiant structiifal fcaTurc of this rcKioii is the Sail Andreas fault, whieh runs south alonu' San J^enito Creek as far as the town of San Benito where it crosses a h)\v divide into the Rabbit Valley and from tliere it runs down Ritterwater Creek to its junr-tion witli Lewis Creek and then eontinues soutliward up Lewis Creek. ICast of the San Andreas fault the formations exposed are sands, gravels and clays of the P^tehegoin and Jacalitos formations, which rest on the east ai^niinst the Franciscan. In the fault zone of tlie San Andreas fault, which averages about one mile in width, the faulting- has exposed beds of Franciscan and Cretaceous age, together with masses of granite and ancient crystalline metamorphics. West of the San Andreas fault the foi-matioiis consist of beds of sand and gravels of the Paso Kobles forn)ation with a thickness of about 2U0 feet. Below the Paso Robles is about 3000 feet of the Santa Margarita formation consisting of beds of medium coarse white sand and abont 1000 feet of sandy diatomaceous shale. This shale is found near the bottom of the formation and is the source of the oil found in this area. Along its northwestern edge in the vicinity of the Pinnacles, the Santa Margarita rests against the eroded surface of the crystalline rocks of the Gavilan Range. An area of granite probably belonging to tlie batholithic mass of the Gavilan Range, outcrops along San Lorenzo Creek just west of Lonoak and the Santa ^largarita sands rest unconformably against its edges. Indications of i)etroleum are found in seeimges along the San Andreas fault zone in Lewis Creek and at the contact of the Santa ]\largarita with the granite in the vicinity of Lonoak and San Lorenzo Oeek. Apparently on account of unfavorable structure, the oil has tended to collect along faults and at the contacts with the igneous rocks. Tlu' region is apparently unfavorable for the accumulation of petro- leum in commercial quantities. This statement is based on the follow- ing facts: (1) The structure is unfavorable (See Sec. EF, Fig. 6). (2) The source of the petroleum is the diatomaceous shale of the Santa iMargarita, which is too limited in thickness and extent to form much oil. (3) Twenty wells have been drilled in the area and none showed sufficient production to be of commercial value (list of wells is given below.) The greater portion of the district has been mapped and examined for oil possibilities, both by the State iMining Bureau^ and the U. S. Geologi- cal Survey.- The report by the State covers the southwestern part, while that of the Geological Sui'V(\v practically covers the entire area in detail. Both reports contain a list of the wells drilled, together with areal maps. Following is a portion of the Geological Survey's report, dealing with the area under discussion, and also including that part of ]\lonterey Countv east of King Citv and alonu' the Peachtree and Lewis Creek 'California State Mining Bureau. Bull. 69, 1914. Petroleum lndu.strv of California. By R. P. McLaughlin and C. A. Waring. Pp. 418-428, plate IV in folio. ^United States Geological Survey. Bull 581-D, 1914. Geology and Oil Prospects of the W'altham, Priest, Bitterwater and Peachtree valleys. By R. W. Pack and W. H. English. 78 CALIFORNIA STATE MINING BUREAU. vallej-s, Sec. EF, Fig. 6 is adapted from this report and shows the gen- eral structure: "Bitterwater and Peachtree Valley and Foothills to the West. Geology. "West of the San Andreas fault zone the beds mapped as upper Miocene rest directly upon the eroded surface of the granite. In llie area shown on tlie map these beds have a maximum thielcness of about 3300 feet and comprise two formations, of which the lower, made up of sand, clay, gravel, and diatomaceous shale and filled with marine fossils, is believed to be the equivalent of the Santa Margarita forma- tion, and the upper, composed of material that was probably laid down in lakes or subaerially, is the equivalent of the Tulare formation. West of Peachtree Valley the upper of the two formations is relatively unimportant, appearing only in isolated areas along the crests of the ridges as a cap less than 200 feet thick. The bods that are comprised in the formation that is considered the equivalent of the Santa Margarita are variable in character, ranging from coarse conglomerate to fine diatomaceous shale, but for the most part are fine grained. Near Lonoak and in Bitterwater Valley the lower 1000:+^ feet is composed of diatomaceous shale, which forms prominent white outcrops that are especially noticeable about 2 miles north- west of Lonoak postofflce. Sliale of this type forms the lower part of the Tertiary along the west side of Bitterwater Valley, in the north end of Mustang Ridge, in small areas near the east corner of the Peachtree ranch, and in much of the Topo rancli northwest of the area mapped. In many other parts of the region, however, sandy or even gravelly beds, such as those exposed near the asphalt quarry west of Lonoak, rest upon the granite. Practically no diatomaceous shale appears resting upon the granite near its exposures in small areas 4 miles southwest of Lonoak. The variability in the lithology of the lower part of the Tertiary is well shown along the north side of San Lorenzo Creek west of the granite that is exposed at the edge of the area mapped. Possible explanations of the variability in the thickness of the diatomaceous shale appear to be (1) that the Tertiary beds wtM-e laid down upon a very uneven surface of granite and that in parts of the region the lower beds were not deposited; (2> that the sliale actually grades laterally into coarser materials; (3) that the diatomaceous shale is older than the clay and shale and is separated from them by an unconformity. The most probable explanation seems to be that the variability in the thickness of the shale is due both to lateial variation in character and to the uneven surface upon which it rests. Sandy beds intercalated witli the diatomaceous sliale contain fossils apparently of precisely the same type as those in the overlying sandy beds, and it seems improbable that any considerable time intervened between the deposition of the two divisions. Tlie presence or absence of tlie diatomaceous shale is of considerable importance, for the seeps of oil appear only in those areas where it has considerable thickness. "The Tertiary strata that cover the granite have not been deformed to any very marked degree west of the San Andreas fault zone. West of Peachtree Valley nearly to the edge of the area mapped this cover may be thought of as a sheet, very slightly wrinkled along irregular lines and in general dipping slightly toward the northeast. P^arther west the dip changes ; along the edge of Salinas Valley it is in general toward the west, cai-rying the beds beneath the valley. Between Peachtree Valley and the San Andreas fault zone is a shallow syncline, which the writers have termed the Peachtree syncline. This fold starts near the center of the Peaclitree ranch and continues northwest through the Topo ranch, beyond the area mapped. The east flank of this syncline is terminated by the San Andreas fault zone, along which the beds of diatomaceous shale in the lower part of the later Miocene formations are to tilted that they are nearly vertical. North of Lonoak the southwest flank of the syncline merges with the area of low irregular dips along the foothills east of the Salinas Valley, but along the Peachtree Valley it is apparently terminated by a fault. It is in this synclinal basin that most of the drilling for oil has been done. Along the San Andreas fault a zone varying from three-quarters to 1 mile in width is traversed by innumerable faults and the rocks are greatly shattered. In this zone rocks of the Franciscan and later formations are intermingled in irregxilar masses, and along the west side steeply tilted beds of diatomaceous shale occur. Through this zone of fracture oil contained in the rocks has found an easy passage to the surface. Several wells have been drilled along it, but none of them have found any considerable reservoir of oil. "Surface Indications of Petroleum. "In several places in Bitterwater and Peachtree valleys oil impregnates the surficial sandy beds that lie in the San Andreas fault zone oi- that rest upon the granite. The largest of these outcrops occurs at the Mylar asphalt quarry, in Sees. 14 and 15, T. 19 S., R. 9 E., about 2 miles west of Lonoak. The basal 2.") to 50 feet of the later Miocene here is a coarse, arkosic sand or grit that was evidently derived from the granite upon which it rests. The outcrops of this sand for a distance of about one-half mile are impregnated with tarry oil or asphalt, the amount contained varying from place to place. Where the outcrops are weathered and unbroken the sand is light brown and friable, but in the newer faces of the quarry tlie sand is plastic from the amount of tar it contains, and in one place thick oil slowly oozes out along its contact with the underlying granite. The oil sand or asphalt is quarried from time to time and used in repairing the roads about King City. Most of the sand is of medium coarse grain, and the material is used directly upon the roads without the addition of more sand. PETROLEUM RESOURCES OF CALIFORNIA. 79 "Oil-saturated sands outcrop at two i.laoes near the southeast corner of the Peachtree ranch, in what corresponds to tlie SEJ Sec. 22 and the SWi Sec. 25 T. 20 S., RUE \t the first-named locality a massive sand.stone that stands almost vertical occurs on 'the west side of an area of much contorted diatomaccous shale, ihe relationship of the sandstone and shale is not entirely clear, as the rocks are con- siderably faulted, but the sandstone is believed to be stratigraplueally above most or possibly all of the shale. The sandstone is impregnated with heavy od, which slowly seeps out in the bottom of one of the steep arroyos. About 1.^ miles southeast of this seep a sandstone 50 to 60 feet thick, bedded with the diatomaceous shale that occurs near the base of the Tertiary, is impregnated with oil. This bed appears to be a sandv lens in the upper part of the diatomaceous shale. It lies at the western edge "of the San Andreas fault zone, is much fractured, and is truncated on the east by a fault that brings it into contact with the clay in the iulare "Where the San Andreas fault crosses Alvarez Creek, in Sec. 32, T. IS S., R- 10 E., an outcrop of much fractured coarse arkosic sandstone in the Tulare formation is stained by petroleum and wells less than 100 feet deep sunk here have yielded a little light-gravity oil. . , . c. oa n- i- ci t> e v "About 13 miles due north of King City, approximately in Sec. 29, 1 U ^ , K. !> b.,. at the Matthews asphalt quarry, a bituminous sandstone outt'rop lies, like that at the Mylar quarry near Lonoak, between outcrops of granite and of diatomaceous shale. This sandstone mav underlie the diatomaccous shale, as was suggested by Eldriage, but as the oil sand is limited to the small gulch tributary to Chalone Creek and contains besides granitic material an appreciable number of diatomaceous shale fragments, the writers suggest tliat it is jjrobably a stream terrace deposit impreg- nated with and cemented by thick tarry oil that seeped out of the lower part ot the diatomaceous shale. The beds of sand and gravel impregnated with oil are or very uneven grain and on the whole arc much coarser than tliose at the Mylar quarry. "Wells Drilled for Oil. "The following wells have been diilled loi dil in and near Bittervvator and Peachtree valleys ; Nonpareil No. 1, Sec. 32, T. 18 S., R. 10 E. Nonpareil No. 2, Sec. 32, T. 18 S., R. 10 E. Nonpareil No. 3, Sec. 32, T. IS S., R. 10 E. Lonoak No. 1, Sec. 7, T. 19 S.. R. 10 E. Lonoak No. 2, Sec. 31, T. 18 S., R. 10 E. Alvarez No. 1, Sec. 33, T. KS S., R. 10 E. I>e Franc No. 1 (Standard Oil Co.). Topo ranch, in wliat corresponds to Sec. 33, T. 17 S., R. 9 E. Tompkins No. 1 (Standard Oil Co.), Sec. 19, T. li) S., R. 10 E. Tompkins No. 2 (Standard Oil Co.), Sec. 19, T. 19 S., R. 10 E. Landrum No. 1 (Standard Oil Co.), Sec. 28, T. 19 S., R. 10 E. Doheny well. Sec. 14 or 15, T. 19 S., R. 9 E. <, o . Miller No. 1 (Union Oil Co.), Peachtree ranch, in what corresponds to Sec. ii, T. 20 S., R. 10 E. Salinas No. 1, Sec. 9. T. 19 S., R. 10 E. "The Nonpareil wells were drilled about 13 years ago near the seep where the San Andreas fault crosses Alvarez Creek. Previous to the drilling of the main wells, two wells were drilled by hand, the deeper of which is said to have obtained light-gravity oil at 60 to 70 feet. At the time of the writers' visit it had caved below the 55-foot depth and was dry of oil, although containing considerable gas. Of the three larger wells. No. 1 is said to have reached a deplli of 1038 feet without obtaining more than a trace of oil. Well No. 2 was drilled 653 feet and obtained oil between 400 and 520 feet. Oil now stands in the hole, but the well has never produced. Well No. 3 reached a depth of 1300 feet, having been drilled through 'a great mixture of rocks,' but obtained no oil. "Lonoak well No. 1 was sunk about 2700 feet and is .said to have reached granite at that depth without having encountered a trace of oil. Well No. 2 reached a depth of 3009 feet, getting a little tarry oil at 600, 800, and 1800 feet. A few barrels of oil is said to have been pumped. "The Salinas well is .said to have been drilled to 450 feet and at that deptn to have found a little very heavy oil like that in Lonoak well No. 2. "The Dohenv well, near the southwest corner of Sec. 14, T. 19 S., R. 9 E.. starts about 750 feet south of the outcrop of the oil sand at the Mylar asphalt quarry- It is said to have reached the granite at 900 feet without having found oil. The lack of success of this well is striking and shows the local character of the oil sand that is quarried as asphalt. "The Alvarez well was started a few hundred feet south of the oil Nonpareil wells and drilled to a depth of 900 feet but obtained no oil. "The Le Franc well of the Standard Oil Co., at the head of Bitterwater Valley, within a few hundred feet of the San Andreas fault line, was drilled to a depth of more than 2000 feet. It is said to have penetrated considerable oil sand but produced no oil. The fractured condition of the beds here prohibits an estimate of the strati- graohic position of the oil sands penetrated. "The two Tompkins wells and the Landrum well of the same company were drilled in Peachtree Valley and are said to have reached a 'hard gray sand' without finding more than a trace of oil. It may be that the 'gray sand' is an arkosic sand derived from the granite and is similar to that at the asphalt quarry west of Lonoak, but the writers believe that it is more probably granite. 80 CALIFORNIA STATE MINING BUREAU. "The Miller well of the Union Oil Co., near the west edge of the Peac-htroe ranch along the road from Peaclitree \'alley to Salinas Valley was drilled to a depth between 2500 and liGOO feet, but no oil was found. "Economic Possibilities. "Along the San Andreas fault the beds are broken and all the formations are so intermingled in small irregular masses as to form a strueture exceptionally unfavor- able for the accumulation and retention of petroleum. It is true tliat oil contained >n tlie solid rocks in tlie immediate vicinity would probably work its way into tiie crushed zone, but it is difficult to believe that it would be held there in quantity and would not work its way to the surface. Thus, although seeps of oil occur along this zone, and although wells such as Lonoak well No. 2 and the Salinas well have obtained small quantities of oil, the presence of oil beneath the surface in suttic.ient amount to make drilling prcjHtable seems very unlikelv. Also, the experience in other California fields shows that oil contained in rocks so badly fractured as these IS of variable character and that much of it is of heavv gravitv. Thus the oil found in the Lonoak and Salinas wells is probably typical of the oil that does occur, despite tlie fact that small quantities of light-gravitv oil have been found in shallow wells on Alvarez Creek. "Of the 3000 feet or more of Miocene beds which are infolded in the Penchtree s>-ncline near Lonoak tlie lower 1000 feet or so Is largely diatomaeeous shale. This shale is continuous soulliward but seems to become more sandy in that direction. That the beds as.sociattd with the shale contain some oil is shown bv the outcropping oil sands in the southeast corner of the Peachtree ranch and by the results obtained in the wells near tlu- mouth of Lewis Creek. However, the writers believe it doubtful that oil has accumulated here in any considerable amount. Tlie syncline is struc- turally isolated, being bounded sharply on tlie east by the San Andreas fault zone and on the southwest by .the granite and probablv by a fault extending along Peachtree Valley. Thus it seems improbable that oil could have collected in this basin from the rocks underlying any very extensive area. Any oil which might have been formed in the beds beneath Salinas V'alley would probably not travel eastward beyond the area west of Peachtree Valley, in which the Tertiary beds are wrinkled irregularly. Moreover, except in a small area near the mouth of Lewis Creek, wliere the beds are slightly domed, the general synclinal structure is not favorable for the collection of petroleum. Kven tlie doming cited is really so slight and lies so close to the badly fractured San Andreas fault zone that it is improbable that oil has collectetl in it. The wells which have been drilled here have pretty thoroughly tested the area, and it is believed that further drilling, even along the small fold mentioned above, will fail to disclose any extensive accumulations of oil. "The low foothills between the Peachtree and Salinas valleys present many of the features exhibited liy the large productive tields in California, and in this area alone, of all the region studied, does there appear to be a possibility of obtaining oil. The factors supporting the theory that oil may have accumulated here in considerable amounts may be listed as follows: (1) Some oil is undoubtedly present, as is shown by the outcropping oil sand at the asphalt (luarry near Lonoak and at the south end of the Peachtree ranch; {-) Diatomaeeous shale, which is regarded as the ultimate source of the oil in this part of the state, is bedded with, overlain by, and underlain by porous sandstone, wliich, although mostly of rather fine grain, would serve as an excellent reser\-oir for oil; (3) The sandy beds .are somewJiat lenticular and are intercalated with clay or shale, thus probably furnishing lociil reservoirs of porous material more or less completely inclosed in impervious wells; (4) The beds are tilted slightly and irregularly, locally forming small, low structural domes; (5) To the west is the broad synclinal Salinas Valley, under which lies part at least of the thick mass of diatomaeeous shale that outcrops along the Santa Lucia Range on the west side of the valley. Thus there is an area of considerable size from which oil might have risen to collect in the slightly folded rocks. "Although the broader features of the stratigraphy and structure appear to favor the hypothesis that oil has accumulated in the foothills west of Peachtree Valley, two important questions remain to be answered, and to neither of them does the answer seem favorable, so far as may be judged from the areal geology. Tliey are (1) whether the oil. though undoubtedly present, was formed in tiuantities in any way comparable with those found hi the southern end of the San Joaquin Valley ; and (2) whether, if any considerable (luantity of oil was formed beneath the valley, it would have collected in the beds in the foothills on the east side in reservoirs of sufficient size to be commercially valuable. "It seems probable that the first question must receive a negative answer. Seeps of oil and dry oil sands occur not only in the region described but also to the south- east, in the Parkfield region, and at intervals for several miles on the west side of the valley. In other words, the outcrop of the Tertiary rocks on botli sides of the basin show evidence of petroleum, and it is reasonable to suppose that the beds in the center of the basin, now covered by alluvium, also contain or at one time contained it. The basin occupied by sedimentary rocks here is, however, of much smaller area than that at the southern end of the San Joaquin Valley; the diatomaeeous shale in it is far thinner than that in the Temblor Range and along the east side of the Salinas Valley, is somewhat irregularly developed, owing, in part, to Its having been laid down upon a very irregular surface of granite and probably also in part to the fact that it is replaced in some areas by sandy beds. This irregularity is well shown along the San Lorenzo (^reek. Near Lonoak the lower 1000 feet or so of the later Miocene is fairly pure diatomaeeous shale, but less than 2 miles downstream sand and sandy clay, in lithologic character precisely like the PETROLEUM RESOURCES OF CALIFORNIA. 81 beds overlying the diatomaLeous shale near Lonoak, rest directly upon the granite. Also, near the small granite exposures some 4 miles soutliwest of Ix)noak the sedimentary beds are entirely sand and sandy clay. Tlui.'?, if the diatomaceous shale is regarded as the ultimate source of the oil it is unreasonable to suppose that so great nuantities of oil were formed here as were formed in tlie southern end of thc^ San Joaquin Valley. "Tlie oil seeps in the region studied are very closely associated with tlie diatomaceous shale, and practically none is known in an area in which the shale has not considerable development. It is not unreasonabla to suppose that beneath the alluvial filling in Salinas Valley the diatomaceous shale has as irregular a development as it has where e.^posed in the area studied. If such is the case, unless there is some special cause for its further migration, any oil which may have originated in tlie sliale would probably not move farther than the sandy beds interstratified with or immediately adjacent to the shale. Thus the tendency would be for the formation of a number of small local concentrations. '•So lar as the effect of the structure upon a possible accumulation of oil is concerned, the most notable feature in tlie foothills between Peachtree and Salinas valleys is the lack of any well-defined fold at all comparable with those which, soutli of Coalinga, border tlie San Joaquin Valley on the west and along which lie the productive oil tields. Instead of being strongly folded the Tertiary beds along the east side of Salinas Valley are but sliglitly tilled, in mueli of the area less tlian :i°. The importance of this difference in structure can hardly be overestimated in considering the possibility oi oil having accumulated in considerable quantity. "Along the edge of Salinas Valley the dip is in general southwest, but near the border of the area mapped it is northeast. The cliange does not take place along a line, but rather along an ill-dehned belt several miles in width, or it perhaps may b^st be described as being marked by a number of short irregular domes of which three appear in the area mapi)ed. One occurs near tlie asphalt quarry west of Lonoak, where the later Miocene beds dip 2° to 7° away from the granite. The second occurs west of the Peachtree ranch, "vyhere a line trending northwest-southeast thiough Sees. IG and 22, T. 20 S., R. 10' K., separates the beds that dip about 2^" SW. from those that dip approximately as much northeast. The third occurs just northwest of tlie isolated outcroii of gianite some 4 miles southwest of Lonuak. These uplifts are so gentle that their axes cannot well be designated by a definite line, but their position is indicated by tlie dips given on the map. "In San Joaquin Valley the sandy beds along the anticlines have served as reservoirs for oil tliat is believed to have once been contained in beds tliat extended over large areas. Much of the oil probably originated beneath San Joaquin Valley, worked its way up the rise, and aL-cumulated in the upper part of the folds. On the east side of Salinas Valley, however, no such folds dominate the structure and there appears to be no reason why oil that may occur disseminated through the rocks over a wide area sliould accumulate in considerable amounts in a single area. On the contrary, oil which may have originated beneath the valley would probably tend to remain in the upper parts of the numerous low, faint domes or wrinkles. Moreover, the diatomaceous shale is much thinner along Salinas Valley than It is along the w^estern border of San Joaquin Valley; hence it is even more necessary in Salinas than in San Joaquin Valley that a structural feature which favors the accumulation of oil should have tributary to it a large area from wliich oil may be drained. "In conclusion it may be said that the irregular structure, the irregular distribution of the diatomaceous shale, and the lenticular character of the sanuy beds all seem to indicate not that oil has accumulated in any considerable quantity in few lociilitie.s but rather that it has accumulated in small amounts at a number of places in the upper parts of low folds or domes. It is not at all unlikely that wells drilled along the axes of the low anticlinal folds that lie between Salinas River and Peachtree Valley will find oil. It is to be expected, however, that the area that may prove productive is very irregular in outline, and that the amount of oil in the producing wells will be small. Thus for many years to come the cost of prospecting this region ■with the drill will probably be much greater than the value of the oil that may be obtained. "So far no well has adequately tested the area west of the Peachtree Valley. The well most advantageously placed is the Miller well of the Union Oil Co., which was drilled near the southwest side of the Peachtree ranch, about a mile east of the line of change in dip, in Sees. 22 and 16. Although the test would have been more satisfactory had the well been located farther west, still the failure to obtain oil in it goes far to prove that any oil sands which may occur here are of small extent. Also, the outcrops of granite some 4 miles southwest of Lonoak are signittcant, for although there is here a slight fold or dome comparable with that near Lonoak, yet the beds, unlike the Tertiary sands at Lonoak, show not the slightest trace of oil. "OUTLYING DISTRICTS. "The -following brief notes regarding the geology and possible occurrence of oil in the Topo ranch, which lies beyond the boundary of the area shown on the map, in the upper part of the valley of San Benito River, are based on hurried visits made during the course of the work. "Topo Ranch. "The Peachti'^e syncline continues as a broad, shallow fold norlihwestward beyond the area shown on the map, passing through the Toi)0 ranch. On the east the syncline is terminated bv the San Andreas fault zone and on the west by the granite which here appears at the surface in the Gabilan Range. Along the west side of G— 13 32 '2 82 CALIFORNIA STATE MINING BUREAU. tlie syiiclinc tlie lower part of the Tirtiary section consists of chalky white (liatomaceous sliale having a maxinnmi thickness of not more than 1000 feet. Upon the shale rest a few hundred feet of sandy beds, which constitute botli tlie Santa Mai-sarita and the Tidare formations. The beds for Tialf a mile on either side of the axis of this syncline dip at angles of less than .5° and on tlie west Hank of the ff)ld at angles of less tlian 10° as far as the granite hills. The Matthews asphalt ciuarry (see p. 147) is on the west flank of this syncline at the contact between the granite and granite and overlying Tertiary beds. "Five wells have been drilled by the Standard Oil Co., in this syncline on or south of the Topo ranch. Some of them were drilled tlirougli th" Tertiary beds to the underlying granite, but none found more than a trace of oil (jr gas. Their names and location are given below : Dunne No. 1, Topo ranch, west of Dunne ranch liouse. Dunne No. 2, Topo ranch. Blown No. 1, Sec. 15, T. 17 S., R. S E. Stone No. 1. Sec. 27, T. 17 S., R. 8 E. Leonard No. 1, Sec. 28, T. 17 S., R. S E. "The Leonard well, drilled about one-third of a mile east of the Matthews asphalt f|uarry, started in tlie diatomaceous sliale and strucic lieavy oil and tar not far above the granite. "This synclinal basin in and north of the Topo ranch presents few features which would make it appear probable that oil lias collected in it in considerable quantity. It is isolated, being bounded sharply on the northeast by the San Andreas fault zone and on the west by the granite of the Gabilan Range, and is tluis almost cut off from the Tertiary rocks in Salinas Valley. These conditions make it difficult to believe that the syncline has acted as a catchment basin for oil drawn from great stretches of rocks in the svirrounding territory. Moreover, the synclinal sti'ucture is not especially favorable to concentration of oil, as any oil that did exist in tliis rock would be forced up the Vise and would appear at the surface, as it has at the Matthews asphalt ciuarry. Finally, the wells that have already been drilled have pretty thoroughly tested the area. "San Benito River Valley. "East of San Benito River, near the southwest corner of T. 17 S., R. 10 E., later Miocene beds, approximately the eciuiva'ent of the Etchegoin formation of the Coalinga region, dip rather regularly 20°-30''SW. About a mile northeast of the area mapped these Vaeds are broken by a fault which is approximately parallel to the San Andreas fault. A short distance nortlieast of tliis fault Cretaceous Eocene (?), and F'ranclsean (Jurassic?) locks appear. Tlie upper part of the Miocene beds is mainly massive arkosic sandstone filled with marine fossils. Beneath these beds are alternating beds of reddish and greenish clay and gravel, much like the beds that appear along the axis of the Vallecitos syncline, about 10 miles away on the opposite side of the Diablo Range, and presumably of upper Miocene age. "There seems to be no reasonable chance of obtaining oil in this part of the San Benito River Valley. So far as known no seeps of petroleum occur here, although the rocks are broken and are in places much shattered by faults, so that oil certainly would liave had abundant opportunity to reach the surface if it ever liad been present. Also, so far as known, no masses of sedimentary rocks that contain any considerable amounts of organic material, such as diatomaceous or carbonaceous shale, occur in this region. Finally, the structure is not especially favorable to the accumulation of oil. "It has been said that the value of this region as oil-producing territorv is shown by the fact that it lies midway between Bitterwater Valley and The Vallecitos, in both of which seeps of oil occur. This can hardly be considered a valid argument, as the .area is separated from the Bitterwater region by the San Andreas fault .and from The Vallecitos by a great mass of Cretaceous and Franciscan (Jurassic?) rocks, which lie stratigraphically below the oil-bearing rocks. "The McMurtry-Hoeppner well, near the west line of Sec. 32, T. 17 S., R. 10 E.. is on James Creek, a tributary of San Benito River from the northeast. The well starts in the fossiliferous late Miocene beds and, when visited in November, 1913, had been drilled to a depth of 14 62 feet, and had apparently reached the clay and gravel that form the lower part of the upper Miocene. No trace of oil had been obtained." Monterey County. Monterey County, lying in the central coast region of the state, bor- ders the l^acific for a distance of about 85 miles and stretches back into the Coast Ranges witli an average width of about 45 miles. The principal topographic features consist of the Santa Lut-ia Range which borders the coast from IMonterey Bay south into San Luis Obispo County, reaching elevations of from 3000 to 6000 feet ; the Salinas Valley, which drains the central portion of the county for its entire length; the Cavilan Range which boi'dcrs the Salinas Valley on the PETROLEUM RRSOURCES OP CALIFORNIA. 83 east, from the Pa.jaro Kivcr to a point near Kinj; City. South of Kiug City the ea.st siiK' of tlie Salinas VaHcy is t-oniposed of low rolling' hills, which gradually rise to the Temblor Kange, along the eastern border of the county. The county will ])e divided into the following areas and the oil possi- bilities of each discussed: (1) ^louth of the Salinas Valley and the district bordering on the Bay of IMonterey. (2) Area of the Santa Lucia ^Mountains. (3) Area of the CJavilan Mountains. (4) Salinas Valley from Salinas to Greenfield. (5) San Antonio Hills. (6) Salinas Val- ley from Greenfield south to the county line. (7) Area east of the Salinas Valley from King City south to the county line. Mouth of the SaHnas Valley and District Bordering on the Bay of Monterey. This region may be considered as a coastal plain, consisting of low rolling hills and marsh land and it is continuous with a similar area in the vicinity of Watsonville, Santa Cruz County (Chapter VII). The surface fornuitions consist of soft, incoherent sands and clays, of a yellow-brown color, probably of Quaternary age. There is no definite evidence as to what underlies these beds, but it is probable that the Vaqueros sandstone and diatomaceous shale of the ]\Ionterey are present beneath a portion of the area. Evidence as to this may be found in examining the edges of the district and noting what formations appar- ently dip under it. On the south edge in the vicinity of Del Monte and Seaside the ^Monterey shale which forms the foothills of the Santa Lucia Range is dipping to the northeast and apparently disappears beneath the Quaternary sands just southeast of Seaside. From this point east to Salinas, the Quaternary is resting against sands and shales of the ^Monterey Series. Along the east edge from a point due east of Salinas to a point about three miles southeast of Dumbarton, the Quaternary rests directly on the crystalline rocks of the Gavilan Range. This contact may be seen near the Lagunita School, along the State Highway, from Salinas to San Juan. From the vicinity of Dumbarton north to Aromas on the Pajaro River, the Quaternary is resting against a massive medium to fine-grained yellow sandstone, which weathers into large, bold outcrops. The dip is a])out 45° to the southwest and thickness about 5000 feet. Four miles due east of Dumbarton the bottom of the formation may be seen resting on the granite. The age is not definitely known, but from the lithology and its relationship to the granite, it can probably be correlated with the Vaqueros sandstone of the Santa Lucia Range. AVhile the area contains no evidence of petroleum, it has certain possi- bilities, similar to those of the area around Watsonville. These pos- sibilities are that the sands and diatomaceous shales of the Monterey Series may underlie the area and be folded into favorable structure hidden beneath the Quaternary sand. The area is therefore worthy of being mapped in detail to discover if such conditions actually exist. Area of the Santa Lucia Mountains. This district occupies that portion of the county lying south of Mon- terey and west of the Salinas River. The San Antonio Hills, a detached range of the Santa Lucia Mountains lying between the San Antonio River and the Salinas Valley, will be discussed separately. The major portion of this area is covered by crystalline and metamorphic rocks. 84 CALIFORNIA STATE MINING BUREAU. ni These may be divided iuto two series. The older, kiiuwii as the Santa Lucia Series of Paleozioc age, and tlie yomiger series Ijelonging to the Franciscan formation (Jurassic). The Santa Lucia Series is found in the north, nortlieastern and western portions of the ai"ea and consists of massive limestones, marbles, schists, granites and gneisses. The Fran- ciscan is found overlying the Santa Lucia in isolated patches along the coast and in a rather broad area south and west of the Nacimiento River. It consists of beds of altered sandstone slates and intrusive serpentine. Tiie area occupied by these two series may be considered as impossible for oil. The areas occupied by sedimentary rocks and which could possibly contain oil will be noted below. The first of these areas lies along the valley of the Carmel River and Tularcitos Creek and the low foothills between ^Monterey and Salinas. The formations exposed consist mainly of diatomaceous shales of the IMonterey Series. These shales vary from the soft chalky form to the rather hard brittle variety. From the junction of the Carmel River with Tularcitos Creek, _ southeast to Jamesburg, the shales occupy a narrow trough about ten miles Avide, between the main range of the Santa Lucia ^Mountains on the southwest and the Soledad HilLs on the northeast. On both edges of the trough the shales rest on the eroded surface of the Santa Lucia Series. From Jamesburg southeast the Monterey area thins to about two miles in width and crosses a low' divide in the vicinity of Sees. 35 and 36, T. 18 S.. R. 4 E., joining a body of sedi- mentary rocks along the Arroyo Seco on the east slope of the range. Along the Carmel Valley proper, west from its junction with Tular- citos Creek, the base of the Monterey is resting on the Santa Lucia Series along the south side of the valley. The general structure is that of a monocline, dipping about 20° to the northeast. On the west this mono- cline rests against crystalline rocks along Carmel Bay and the granite areas west of the town of ^Monterey. On the east it is prevented from dipping into the Salinas Valley by the granite of the Soledad Hills. On the north it dips under the Quaternary of the mouth of the Salinas Valley, along the edge of the foothills that run from Monterey to Salinas. This contact is described in the previous article on the ''Mouth of the Salinas Valley." It is possible that in the vicinity of Toro Creek the Moutere}" may be overlaid by sands and shales of the upper Miocene and Pliocene which in turn dip under the Quaternary sands of the valley. Along the north and south sides of Carmelo Bay are small patr-hes of coarse sands and conglomerate, probably of Eocene age. In ^lalpaso Creek about two miles south of the bay, similar beds containing coal occur. The total thickness of this Eocene is about 500 feet. Save for an occasional speck of bitumen in the shale there is no indication of petroleum in this area. This, together with the lack of favorable structure and reservoir formations, make the district rather improbable for the accumulation of oil. The second area of sedimentary rocks occurs on the east slope of the Santa Lucia Range, opposite the Salinas Valley, between Greenfield and King Citv. This body of sediments is best exposed alone the Arroyo Seco, Reliz Creek and Vaquero Creek. It continues west from the edge of the Salinas Valley about twelve miles and the bottom is exposed, resting on the crvstalline rocks about three miles east of Tassajara Hot PETROLEUM RESOURCES OF CALIFORNIA. 85 Springs. A small l)ody of it continues nortlnvost and crosses the divide, joininia: the ^Monterey area southeast of Jamesburplies in general to those areas in IMonterey and San Luis Obispo counties where the ^Monterey shale and the Paso Robles formation are exposed. The following wells have been drilled, or are drilling, in the Bradley anticline : A well in Sec. 4, T. 25 S., R. 12 E., is said to have been drilled to 1340 feet, getting small amounts of gas but no oil. This well was apparently located in the axis of the Bradley anticline. Just south of the town of Bradley and located on the axis of the fold, the Bradley- San Miguel Oil Company has a well down about 2000 feet. Showings of oil and ga§ have been reported. In Sec. 32, T. 24 S., R. 12 E., the Shell Company of California has a well down 4200 feet. This well is located approximately on the axis of the fold and apparently went through the Pliocene beds at 1600 feet, logging ]Monterey shale from tbat point to its present depth. Several showings of oil have l)een reported in the ^Monterey, but nothing of com- mercial value has been found to date. In the area west of San Ardo along the fault contact between the IMon- terey and Santa Margarita, there are several seepages of oil. Following is a portion of English's^ report on this territory: '•Area West of San Ardo. "Geology. — Tlu/ San Antonio Hills, along the west side of Salinas River, consist entirely of the Salinas sliale, except for a belt of the sandstone and shale of tlie Santa Margarita formation about a lialf mile wide close to the edge of tlie valley. The Santa Margaiita beds in this lielt overlie the Salinas shale with marked imconformity. Tliey dip 40° to 60' NE., in marked contrast to tlie gently dipping beds of the same age on the east side of the river. There must be a syncline or a faulted syncline some- wliere beneatli tlie valley alluvium and terrace formation, but there is no surfai-e evidence to indicate wliere tlie syncline sliown on Plate XXVII really lies beneatli the Quaternary cover. The Santa Margarita is here markedly unconformable on the Salinas shale. "Evidence of oil. — In Garrissere Gulch, west of San Ardo, tar sands in the Santa Margarita extend through a thickness of several hundred feet ; farther south, in Sec. 19, T. TJ, S., R. 10 E., the lower beds of the Santa Margarita are richly impreg- nated with oil and tar; and other oil sands are exposed close to the base of the sandstone as far south as the southern limit of this belt of Santa Margarita in Sec. Z'.i. "P>-onomic possibilities. — Surface evidence indicates that the oil migrated from the underl>ing shale into the Santa Margarita, and that it is confined to the west side of the syncline which lies somewhere out in the valley. The abundance of oil sands at the surface suggests that oil might be obtained by wells that would reach the lower part of the Santa Margarita at a considerable depth. The best place for a test is opposite the best outcropping oil sands, which occur between the north line of Sec. 13, T. 22 S., R. 9 E., and the south line of Sec. 19, T. 22 S., R. 10 E. The well should be far enough cast of the outcrop to reach the base of the Santa Margarita at a depth between 1000 and 1500 feet. "Wells drilled for oil. — The wells drilled in this area are described below in order from north to south. They were all drilled some time ago, and the information obtained about them is fragmentary. "The Newell well, east of Sec. 12, T. 22 S., R. 9 E., is said to have reached a depth of 1310 feet. It probably entered the oil sands at about 600 feet and continued in them to the bottom. It furnishes a fair but incomplete test of this area, as it should have been drilled to the underlying shale, which is here probably several hundred feet deeper. "The Capl. Barrett well, near the north line of Sec. 19, T. 22 S., R. 10 E.. is said to have reached a depth of SOO to 1000 feet. It is located too close to the basal contact to test the Santa Margarita. "The Tomboy well, about 1800 feet southeast of the Barrett well, is said to have reached about the same depth. It probably entered the Salinas shale at from 500 to 600 feet and proves that at that depth the overlying Santa Margarita does not contain oil. 'U. S. Geological Survey. Hull. i;9l-H. By W. A. English. PETKOLELM RESOURCES OF CALIFORNIA. 91 "The Doluny well, in the southwest corner of Sec. 20, T. 22 S., R. 10 E., is practically on the basal contact of the Santa Marsarita. Its denth was not learned. "The well of the Norman Oil Co.. in the northeastern part of Sec. 4, T. 23 S.. R. l(t E., starts down in the Salinas shale on the north Hank of a well-marked anticline. Its deptli and history were not learned." Area East of the Salinas Valley from King City South to the County Line. This district may be considered as enibracintr the territory that lies between the Kings t'ounty line and the headwaters of the streams that drain into the Salinas Valley, with a Icnfrth north and south from Lonoak to the Chalome Ranch. It is characterized l)y a number of narrow north and south valleys, chief of which are Lewis Creek, Peachtree Valley and Priest Valley in the northern portion and Chalome Creek and the Park- field area in the southern pnrtinu. The district has been mapped in detail both by the Gcolo.uical Survey' and the State .Alinin^i; Bureau-. The general geology of the region may be summed up as follows : Along the ridge that divides this area from the Salinas Valley the formations consist of white sandstone and diatomaceous shale of the Santa ]Mar- garita. overlaid in i)laces by the sands and gravels of the Pliocene. The general dip is about 10° to the west. The Santa ^Margarita is apparently resting on the eroded surface of the granite. Along the ea.st side of the Peachtree Valley there is a syncline in the upper ^Miocene formations. Running along headwaters of Big Sandy Creek and Vineyard Canyon and thence southeast into the Chalome Ilills is the axis of an anticline, partly in the Santa ^largarita and partly in the Pliocene. The San Andreas fault, which is the dominant feature of this area, runs south down Lewis Creek and then across a divide into Charley Valley and thence across another divide into Chalome Creek and con- tinues south down the latter, passing just east of Parkfield. The fault zone averages about three miles in widtli and the formations expo.sed along the rift consist of the basement conii)lcx, the Franciscan, the Chico, the Vaqueros and the Santa ^Margarita. All the beds have been sharply tilted and crushed and the area occupied by any one forma- tion is relatively small. In the area east of the fault the upper ^Miocene formations are fountl lying on the Chico aiul the Franciscan. Indications of oil are_found along the Peachtree Valley and in the vicinity of the San Andreas fault, particularly in the Parkfield area. The oil apparently originated in the diatomaceous shales of the Santa ]\Iargarita and has collected at the contact of this formation with the underlying granites, or where the shales have been brought in contact, by faulting, with the Pliocene sands. Sec. E-F, Fig. 6, shows the general structure in the northern portion of this region. The unfavorable structure and the lack of any great amount of diato- maceous .shale, make the region unfavorable for the accumulation of petroleum in any large quantities. 'U. S. Geological Survey. Bull. 5S1-D. Geology and Oil Prospects in the Waltham, Priest, Bitterwater and Peachtree Valleys, 1914. By R. W. Pack and W. A. English. U. S. Geological Survey. Bull. 691-H. Geology and Oil Prospects of the Salinas Valley- Parkfield Area, 1918. By W. A. English. -California State Mining Bureau. Bull. 69. Petroleum Industry of California, 1914. 92 CALIFORNIA STATE MINING BUREAU. In the article on San Benito County, page 78, a portion of Pack and English's^ report on the Peachtree area is given. Below is a portion of the same report dealing with the Parkfield area : "Parkfield District. "The Parkfield district (Fig. 35, PI. XXVIII) li(s In .in elevated part of the Diablo Ran^e about 2S miles from Coalinsa, in San Joaquin Valley, and 22 miles from San Miguel, in the Salinas Valley, the two nearest railroad points. Despite the DOor transDortation facilities the presence of numerou.s oil seepages hero has led to the drilling of a number of wildcat wells, thougli without any distinctly , favorable results. Nevertheless, there are many people who still believe that the district will ultimately prove productive. "Stratigraphy and structure. — Thou.gh most of the formations common to the Coast Range crop out within this area, the onl.v one present in which oil is likely to have originated is tlie Santa Margarita (.?) form.aiion, which is exposed on the -southwest flank of the syncline east of Parkfield. Oil is, therefore, to be looked for only in beds adjacent to this formation and particularly those overlying it. in areas of favorable structure. The beds throughout tlic Parkfield district dip steeply, and the structure is complicated. Toward the north, where the Parkfield syncline approaches the San Andreas fault, beds of widely different ages have been brought close together by the extensive faulting. East of Parkfield, the syncline is less faulted but presents a remarkable disparity in the succession of formations out- cropping on tlie two sides of the axis. It may be seen from Plate XX\'11I that the Vaqueros formation and th-.^ Santa M.argarita (?) formation, which are well developed on tlie soutliwest side of the .fold, are aVjsent on the northeast side, along the flank of Table Mountain. The absence of tliese beds is accounted for partly by faulting along the Tertiarj'-Cretaceous contact but is due, also, to an unconformable overlap by the upper Miocene formations upon the older formations. Some time before the deposition of the upper Miocene sediments the Table Mountain area was uplifted and the Vaqueros and Santa Margarita (?) formations were entirely eroded away. At the same time the beds which now crop out on the southwest flank of the fold were not eroded to any great extent. The Santa Margarita (?) formation is believed to underlie the upper Miocene to a point considerably east of the synclinal axis, as the shale crops out on tlie northeast flank of the fold only a short distance southeast of the area shown on Plate XXVIII. "Indications of oil. — Numerous seeps occur in this district and are important as giving direct evidence that oil is present. The seeps are on both flanks of the Parkfield syncline, some near the Table Mountain group of wells and others north- west of Parkfield, close to and within the San Andreas fault zone. "On the slope of Table Mountain from the east boundary of the upper Miocene sandstone down to the lower group of wells there are numerous seeps of tarry oil in each of the small gulches, and small pools of nearly solid tar have collected below the seeps. Down the canyon from the Table Mountain wells, in the eastern part of Sec. 13, are accumulations of tar, indicating a former seep. "The Parkfield syncline is truncated northwest of Parkfield by the San Andreas fault, and the diatomaceous shale comes close to the fault. In this zone oil seeps are numerous and occur in all the formations, even in the granitic rocks. Tiie following are the principal ones seen : "Near the center of the north line of the SEJ Sec. 9, T. 23 S., R. 14 E.. a small pit has been dug in sandstone immediately overlying the diatomaceous shale, and a small quantity of oil has collected in the pit. "An almo.^t continuous line of small seeps occur_in the Paso Robles and the Vaqueros formations in the bed of the small creek which drains eastward across the center of the NWJ Sec. 5, T. 23 S., R. 14 E. "Seeps of heavy oil occur every few feet in a fault block of crushed granite where it is crossed bv the bed of a small gulch that trends eastward and joins Little Cholame Creek about 1000 feet northeast of the center of Sec. 31, T. 22 S., R. 14 E. Seeps of oil in granite are of course very unusual, though in the present case no unusual explanation is necessary to account for the facts. The granite is a fault block which was crushed and jointed by movements along the San Andreas fault zone. Thus the normally impervious granite became sufficiently porous for oil to enter it from adjacent bodies of shale, in exactly the same way that the oil which now seeps from the Paso Robles and Vaqueros entered those formations. "Economic possibilities. — The Parkfield syncline is the only fold in this area in which any great amount of the Santa Margarita (?) formation is present and in which it is overlain by a sufficient covering to retain any oil originally derived from the shale. About 2500 feet of upper Miocene beds are included in the syncline, and oil might be expected to occur at their base on one or both flanks of the fold. This syncline could not safely be condemned as barren of oil by reason of the surface evidence, though the flanks of an isolated syncline of this type are not the most favorable structure imaginable. "The Tricounty well and the Table Mountain group of wells have given actual proof that only small quantities of oil are present, and as these wells penetrate the beds most likely to contain oil if it were present at all, further drilling upon this syncline would appear inadvisable. 'U. S. Geological Survey. Bull. ."iSl-D. Geology and Oil Prospects of the Waltham, Priest, Bitterwater and Peachtree Valleys, 1914. By R. W. Pack and VV. A. English. PETROLEUM RESOURCES OF CALIFORNIA. 93 "Unfavorable results were also obtained by test wells in the Vallecitos,' an area norlliwest of Coalinga, in which the structure is essentially similar to that of tin- I'arkfioKl svncline. Tlie tests of those two areas go far toward jiroving: tluit isolated synflines oi" the oil-btariug series, surrounded by older rocks, will not prove productive , in ralifornia. There are three factors which may account for the lack of oil. First, there may be an insutlicient amount of shale present to have originally furnished any large quantity of oil. Second, the oil originally present could not be greatly concentrated at certain points, as migration could take place only along the coniparativtly short distance between the axis of the synclinc and the outcrops of the oil sands on the Hanks of the fold. In contrast are the productive San Joaquin Valley fields, where the oil in the productive folds may have, come from" areas far out in the valley syncline and also have migrated up the rise in anticlines. The third factor is the probable loss of oil at the outcrop of the oil sands. In an isolated syncline there is nothing to prevent the oil migrating up the dip and escaping at the outcrop. "Wells drilled for oil. — In the following descriptions of wells the numbers corre- spond to those on the geologic map of the Parkfield area (PI. XXVIII)." (See end of article for locations.) : "At the localities numbered 1 and 2 remnants of rig timbers, etc., probably represent old holes drilled by Captain Barrett and associates before year 1900. The locations are unfavorable. "Well No. 3, the Oakshade well, owned by the Monterey Oil Co., is said to have been drilled to a depth of 1910 feet and to have encountered some oil and ga.s. This well is situated in the zone of complicated structure along the San Andreas fault. Such wells generally produce showings of oil but not enough to make them successful. "Well No. 4 ind'icates the location of the Middle Ridge Oil Company's derrick. No drill ing has been done here and there is little chance of obtaining oil at this locality. "Well No. 5, the Tricounty well, is said to have reached a depth of 4160 feet and found showings of oil at several depths. The well starts in upper Miocene sandstone and reaches the underlying Santa Margarita (?) formation near the bottom. Although there was some water trouble, which might account partly for the failure to obtain much oil, this well furnishes a pretty fair test of the west flank of the Parkfield syncline. "Well No. 6, tlie Parkfield Syndicate well, was drilled with a portable rig to a depth of 500 feet and got a small amount of gas. It was drilled entirely in the Vaqu- ros sandstone. "Well No. 7, the Miller or Raymond well, was the first of the Table Mountain group of wells, as drilling is said to have been started in 188S. The drill is said to have reached a depth between 640 and 80 feet without passing through any oil or tar sands. Sulphur water is'now llowing from the casing. Of the wells of the Table Mountain Oil Co., Nos. 8 and 9 are 270 and 600 feet deep respectively. They arfe said to be in oil or tar sand for most of this depth. Wells Nos. 10, 11 and 12 are sliallow, ranging from 100 to 200 feet in depth ; they are now abandoned, and when the writer visited them water and a small quantity of oil stood within 25 to 50 feet of the top of the casing in each well. The Table Mountain wells are said to have nroduced a few barrels of oil per day at the lime of their completion. The oil doubtless originated in the Santa Margarita (?) formation and migrated up along the fault which lies east of these wells, saturating the sands for a few bundled feet out from the fault. The base of the uiiper Miocene sandstone also probably contains some oil which has migrated directly up from the underlying shale, in addition to that which came up along the fatdt plane. "Well No. 13, sometimes called the Livermore well, was drilled by the Future Success Oil Co., ,ln 1913-14. It reached a depth of 1810 feet, mostly in Cretaceous shai^; but also apparently passing through intrusive sheets of serpentine and possibly reaching Franci.scan rocks near the bottom. This well is separated from those on the west by a fault, and the light-gravity oil. showings of which are said to have been encountered, originated in the Cretaceous shale. Wells drilled in the dark Cretaceous shale generally get showings of a light-gravity oil but only a very small quantity. "Well No. 14, the Dominion well, was drilled in 1912 nnd is .said to be between 150 and 300 feet deep. It is located in an area of .serpentine slide, near the contact between the serpentine and the Cretaceous rocks. The bailer dump (consisting of the drill cuttings) appears to be made up entirely of serpentine, but some Cretaceous shale may have been encountered. The location is unfavorable." AYell No. 1 is located about the center of Sec. 32, T. 22 S., R. 14 E. Well No. 2 is located in the SE. -} of Sec. 5, T. 23 S., R. 14 E. AVell No. 3 is located near the north quarter-corner of Sec. 8, T. 23 'Veil No. 4 is located in the NE. ] of See. 18, T. 23 S., R. 14 E, Well No. 5 is located in the SE. ^ of Sec. 15, T. 23 S., R. 14 K ^Anderson. Robert, and Pack. R. W. Geology and Oil Resources of the Weirt - Border of the San .loanuin Vallev. North of Coalinga, Cal. U. S. Geol. Survey^ Bull 603. Pp. 167-177, 1915. 94 CALIFORNIA PTATE MINING BUREAU. Well No. 6 is located in the NE. ] of See. 26, T. 23 S., R..14 E. Wells Nos. 7, 8, 9, 10, 11 and 12 are loeated in the SE. i of Sec. 13, T. 23 S., R. 14 E. Well No. 13 is loeated in the SE. ] of See. 18, T. 23 S., R. 15 E.. Well No. 14 is loeated in the NE. ] of See. 19, T. 23 S., R. 15 E. San Luis Obispo County. That portion of the connty lying north of San Lnis Obispo and west of the Salinas Valley is a nigged mountainoas area of the Santa Lucia Range. The rocks along the western portion are mainly sandstones, cherts and serpentine of the Franciscan. On the eastern slope which drain.s into the Salinas Valley, beds of sandstone and shale of C'retaceons age are exposed together with overlying beds of sandstone and shale of tlie ^Monterey Series There is no evidence of petroleum in this district. In the Salinas Valley proper, between the ^Monterey Connty line and Templeton, the formations ex[)osed are l)eds of sand and gravel of the Paso Rol)les formation, with an aiea of granite to the northwest of the town of Paso Robles. The Paso Rol)les beds are practically flat lying with the exception of an area northeast of San Miguel, where the south- ea.st end of the Bradley anticline is found. The only oil possibilities lie along the axis of this fold (see page 89 for description). However, in view of the fact that the Shell Company's well in See. 32, T. 24 S., R. 12 E., ]Monterey County, located on the axis of the fold, has reached a depth of 4200 feet, with only a small showing, makes the outlook for production unfavorable. The Salinas Valley from Templeton to Cuesta Pa.ss becomes very nar- row, the formations exposed consist of small thicknesses of highly- crushed diatomaceous shale and sandstone of the ^Monterey Series, overlaid by small patches of tine white sandstone and diatomaceous shale of the Santa jNIargarita. On the west these formations rest against the Cretaceous and Franciscan and in the east against a granite area. The district is unfavorable for the accumulation of oil. That portion of the county lying east of the Salinas Valley and north of a line running due east through Atascadero is mainly an area of low, rolling hills drained by Estrella and San Juan creeks. The formations exposed consist mainly of Hat-lying beds of sand, gravel and clay of Pliocene age. In the extreme northeast corner near Chalome, there is a small area of Cretaceous and ^Monterey. In the Red Hills, which lie southeast of Shandon, English^ has reported that pre-Franciscan rocks are present, and McLaughlin and Waring- have reported the presence of jMonterey shale and Vaqueros sandstone. Southeast of Creston in T. 28 S., R. 14 E., ])eds of the Santa ^Margarita formation, together with sand- stone and shales beds of the Monterey Series are reported as overlying the granites of the east slope of the Santa Lucia Range. From these outcrops it is apparent that the ^Monterey Series is probably present beneath the Pliocene, over a large portion of this area, and therefore this region fulfills two of the conditions for the accumulation of oil : that is, there are porous beds (Pliocene) overlying beds of diatomaceous shale (^Monterey). However, other conditions are unfavorable and it is not likely that oil in commercial quantities will be found here. This state- 'Geolosv and Oil Prospects of tlie Sulinas VaUey-Parkfield Area. By W. A. Engli.sli. 1918, p. 246. ■■HZ'alifornia Stato Mining Bureau. Bull. G:i. By R. P. McLaughlin and C. A. Waring. Map folio Plate IV, 1914. PETROI-ErM RESOURCES OF CALIFORNIA. 95 inent is based on the fact that favorable .slnict iiic is entirely lacking and the basal beds of the Pliocene show no seepages, iioi- does the Monterey shale show any evidence of petroleum. In additiiui. tlic same facts hold true here as elsewhere in the Salinas Valley area; that is, the Pliocene beds do not contain any appreciable amount of oil and the Monterey contains only very small (|uantities. As stated before, this is due to the uplifting and erosion of the ^Monterey with a loss of the oil content before the dei)()sition of the Pliocene beds. A nuip of this area will be found in the folio accompanying Bulletin 69 of the State iMining Bureau. The area between Atascadero on the north and the Santa jNIaria Valley on the south and between K. 13 E. and 1ho (Mtast has been mapped in detail by Fairbanks^ From San Luis Obispo in a northwest direction this area is covered with metamorphie rocks ol' tlie Fi'aneisean, and the Santa Lucia Range east of Santa Mai'garita is composed of granite. The only possible oil districts consist of two parellel areas of .Monterey shale. One in the main Santa Lucia Range, running southeast from Cuesta Pass down Lopez Canyon, and the second located in the San Luis Range wdiich borders the coast south of San Luis Obispo. Both these areas are synclinal in structure and the axis of the anticline which once separated them ran down the San Luis Valley and has been eroded down to the underlying crystalline rocks. The shale in the area around Lopez Can- yon is highly tilted, the limbs of the syncline having an average dip of about 50°. Seepages of oil have l)een reported and there is no doubt but what there is sufficient diatomaceous shale present to have formed considerable oil. This, however, probably collected in the beds that formed the axis of the anticline along the San Luis Valley and wliich have been removed by erosion. The lack of any reservoir beds overlying the shale and the unfavorable structure, condemns this area as a possible producer of an appreciable amount of oil. The area of IMonterey shale in the San Luis Range runs from Point Buchon, just soutli of Morro J^ay, in a southea.st direction to the Arroyo Grande Valley The structure is a syncline with the axis striking south 30° east. The northeast limb rests on the crystalline rock of the Fran- ciscan along the San Luis Valley and the southwest limb rests on similar rocks along the coast line. From Point Huchun, southeast to San Luis Obispo Creek, the IMonterey is not overlaid by any younger formation, and there is no noticeable evidence of petroleum. From San Luis Obispo Creek, southeast to the Arroyo Grande Valley, the Monterey is overlaid along the middle of the syncline by the Pismo formation. It is in this area that prominent indications of oil occur and the Arroyo Grande oil field is located. ARROYO GRANDE OIL FIELD. The principal devel()i)ment is along Pismo ("I'eek, al^out three miles north of Pismo. In December, 1920, seventeen wells were pumping in the field, operated mainly by the Associated Oil Company. The average production per well is about nine bai'i'cls per day and the total lu'oduction from the field from July 1, 1!)20. to December ;J1, 1920, averaged about 170 barrels per day of 14° Baume gravity oil. 'United States Geological Survey. San Luis folio lOL By H. W. Fairbank.s, 1904. 96 CALIFORNIA STATE MINING BUREAU. The major portion of the wells are located on the north flank of the svn(^line, the axis of which passes just south of California Oil Company Well No. 3, striking S. 30° E. The oil has originated in the IMontcrey shale auii lias eolleeted in the overlying sands of the Pismo formation. The dips on both tianks of the syncline in the Pismo sandstone average about 20° ; the dips in the underlying ^Monterey are about 60°. The Pismo formation named by Fairbanks^ consists in this area mainly of coarse loose sands with lentic- ular beds of shale. It may be correlated with the Santa ^largarita for- mation (upper Miocene). The logs of wells drilled along the axis of the syncline sliow it to be about 2000 feet thick. The lack of any contin- uous shale bodies which would confine the oil to certain sands, has resulted in tlie oil being disseminated tiircughout the entire 2000 feet of sand in a lean saturation. This, together with the fact that the structure con- sists of an unsealed syncline, aeeoiuits for the .small production. It is not likely that the production or the limits of tlie field will ever he greatly increased over their present status. There, however, is present another possibility which may prove profit- able in time. That is tlie mining and distillation of the bituminous sands of the Pismo, which are to lean to give profitable welh but whicli might in time be Avorth distilling. These sands outcrop along the north limb of the syncline just south of Edna and have at various times been mined for asphaltum. A recent test shows that they yield about twenty- five gallons of 20° Baume gravity oil per ton. In addition to San Luis folio 101,^ reports on this area have been made by Eldridge- and the Mining Bureau.^ The country lying south of Arroyo Grande to the Santa Barbara County line consists mainly of low rolling hills, with the Xipomo Valley in the eastern portion. The rocks exposed con.sist of loose sands and gravels of the Paso Eobles formation, together with recent terrace deposits. Neither of these formations has a thickness of more than a few hundred feet and the underlying Franciscan serpentine outcrops frecpiently over the area. The region oflfers no possibility of having oil. The hills that form the northeast edge of the Nipomo Valley and which are known as the Nipomo Hills consist of rhyolite tuff and diatomaceous shale of the ^lonterey Series. These hills will be discussed in the article on theHuasna District. HUASNA DISTRICT.* This area lies to the south and east of Arroyo Grande and consists of the territory around Tar Spring Creek. Arroyo Grande Creek. Iluasna Valley, Alamo Creek and Suey Creek. The Nipomo quadrangle of the United States Geological Survey covers the major portion of the area. The formations exposed consist mainly of the Monterey Series. The two areas of ^Monterey shale described in the preceding paragraphs and which form the two svnclinal structures along Lopez Canyon ami 'United States Geological Survey. San Luis folio 101. By H. W^ Fairbanl f";™=\\-"„f^'-°T9'^°"^lf S'^ E a Dortion of the Carrizo pla n region, north of the southern pait of i. -9 ^., k. i» l-. ^°ItTs not bought probable that deposits of economic importance will ^'f enco n- tered in this reg On as the structural conditions are more or less unfavorable o\y ng to The numeroul fan ts that affect the formations adjacent to the phxin. No other ndiVUion^of petro eum were found on the southwestern flanks of Temblor Range no thoran east-west line through the mouth of San Diego Canyon. Numerou.s ind - ca ions of petroleum are found in the Vaqueros and overlying formations southoast of sTn D ego Camion, along the flanks of the Temblor Range, and it appears h.glily provable thTt commercial deposits of petroleum occur at "^f 'Y P'^-^^^f.^^^^^ft, '^^f ^^^'n' clines in this region. The anticline ^yhich begins about half a "^'^^ ^oj,'*^' j^^^and Diego Joe's— that is, at the southeast corner of Sec. 8. T. 30 S R. t" „ tp'^ed nasses southeastward along the flanks of the range (see map, II. 1) bas been tested aftwo different localities over a mile apart, at the Smith wells near the corner of sL^ ■.•> •>3 96 and 27. T. 30 S.. R. 20 E., and a mile northwest of that point. "ThV'vac'lueroralso yields oil near the surface at the Erume wells in the ^''outhern mrt of Sec ''^ T 31 S R. 21 E. The peculiar pinkish color indicative of petroleum fs also foi>nd"at practically all the outcrops of the Vaqueros in the anticlines along ^'''•'m-7ring in'mind Ihese favorable indications, it appears probable that wells .sunk thrnugh tlie overlving M<.ntercy .shale and tapping tlic Vaqueros sand.stone at adv. n- t '-eoHs localities will vield petroleum. As the petroleum produced by the shallow oles so far sunk is particularly good, ranging as high a.s 28' Bav.me. >t f ems pro 1- able that oil wherever obtained from the Vaqueros will be excel en t. As tic co idi- Uonshei^> mentioned as favorable continue practically uninterrupti-d along the range as7a southeast as the region back of Sunset, it seems likely ^ha pn.spec ing in f-ivorable localities in the Carrizo Plain District should secure positive i.-bull.s. oVing o the complex folding and accompanying faulting which ^^^^^^^J;^'^^!^^}^!^- even to a greater extent than the northeastern flank of the range, detailed examina- tions of any particular area should be made before predictions arc attempted. On the accompanying map (PI. 1) the principal lines of structure are indicated It is thought by the writers that the anticlines with low-dipping flanks offer the best inducements for exploitation." The area of the Ciiyama Valley is described in Chapter IX in the article on Santa Barbara County. 102 CALIFORNIA STATE MINING BUREAU. CHAPTER IX. Coast Area from the Santa Maria Rivlr to the Santa Monica Mountains. (Includes the counties of Santa Barbara, Ventura and Northwestern Los Angeles.) Santa Barbara County. The principal topograpliic features of Santa Barbara County consist of the San Rafael and Santa Ynez ranges. These two ranges, starting from a common point on the east line of the county, spread out fan-like to the west, the Santa Ynez group running due east and west along the coast line and the San Rafael group running northwest and forming the northern boundary of the county. This fan-like arrangement has resulted in an area of about twenty-four miles in width between the two ranges in the western portion of the county and which is occupied by a series of low hills and river valleys. Beginning on the north'flank of the Santa Ynez and going north to the San Rafael Range, these hills and valleys are as follows : the Santa Ynez Valley; the Purisima Hills; tlie Los Alamos and San Antonio valleys; the Solomon and Casmalia hills and the Santa Maria Valley. In the high ranges of the San Rafael and Santa Ynez mountains, the rocks are principally of Cretaceous and Eocene age, highly folded and crushed and with little or no oil possibilities. In the broad depression in the western portion of the county between these ranges, there have been deposited, great tliicknesses of gently-folded ^Miocene and Pliocene rocks in Avhicli large deposits of petroleum have formed and accumu- lated. This entire area has been thoroughly mapped and the oil resources reported on by Arnold and Anderson.^ In this report therefore only a brief description of the fields will be given, together with the possibilities of their extension to outlying areas. Proven Fields and Adjoining Areas. Beginning at the west end of the county, the first proven field is the Casmalia Hills, just east of Schumann Canyon and Casmalia Station. The structure consists of the broad plunging Schumann antir-line, wliich has its beginning on the coast between Point Sal and ]\Iussel Rock and runs thence southeast along the ridge of the Casmalia Hills, crossing Schumann Canyon about one-half mile south of Schumann Station and continuing southwest down the canyon. Avhere the principal wells are now located, and finally plunging out of sight at a point on the state highway, about one mile south of Divide Station. The formations exposed consist of ^Monterey shale along the axis of the .'Hitv'^ipf, and on the north flank that slopes to the Santa ]\Iaria Valley the i\Ionterey is overlaid by Fernando sands and clays. On the south flank near Casmalia station the INIonterey is overlaid by recent terrace deposits 'U. S. Geological Siirviy. Bull. .322. Gtolosy ami Oil Resources of the Santa Maria Oil Distrift. 1907. By Ralph Arnold and Robert Anderson. PETROLEUM RESOURCES OP CALIFORNIA. 103 The dips on the flanks of the folds vary from 8° to 40° in the area east of Schumann Canyon and in the territory to the west they run from 20° to 80°. The phinge to the southeast averages about 5°. Tlie oil originated from the diatomaceous shale of the ^Monterey and has collected in the hard, flinty, fractured areas of the shale. The field has no true oil sands. An examination of the IMonterey shows that only the lower half is present, the upper portion liaving been removed by erosion. The large deposit of tar and the burnt shale areas in the hills west of Schumann Canyon probably represent the basal oil measures of the Monterey formation. On the axis of tlie fold south of Waldorf, the Vaqueros sandstone is exposed. East of Schumann Canyon the plunge of the anticline has covered the oil measures with a thickness of about 1600 feet of Monterey shale, which acts as a capping' for the oil. The proven areas consist of approximately 1940 acres, which lie between Casmalia and Schumann Stations and east of the Southern Pacific Railroad. In December, 1920, the total daily production from the field was 4517 barrels of oil. The average number of wells producing during this period Mas 87 with an average daily production per well of 52 barrels of oil and 150 of water. This large water production is due to the failure to exclude bottom water and to the fact that the lower oil measures contain both oil and water. The gravity of the oil varies from 9° to 17° Baume in the western portion of the field, but increases in gravity to the soutlieast ; wells on tlie Escolle lease of the Union show oil as high as 25° Baume. Detailed reports on the underground struc- ture and the water conditions may be found in the annual reports of the State Oil and Gas Supervisor.^ Drilling has shown that the productive area on the north flank of the anticline is about 1000 feet in width and on the south flank about 3000 feet in width. Efforts to extend the field along the axis of the fold in the hills west of Schumann Canyon and the railroad have resulted in failures, this being due to the fact that the oil measures of the Monterey are exposed on the surface in this area and contain no impervious cap- ping. The most westerly test wells were drilled by the Standard Oil Company, on the steeply dipping north flank of the Schumann anticline southwest of "Waldorf Station. The wells failed to show am^ oil or to penetrate the basal bituminous beds of the Monterey, which outcrops to the south. Outcrops of bituminous sands, probably of Vaqueros age, are exposed on the axis of the fold south of the above mentioned Standard wells and the Vaqueros may possibly contain oil in this area. Wells to test these sands out should be located on the axis of the fold and not on the steep dipping north flank, as selected by the Standard. It is possible that in time the mining and distillation of the bituminous shales of this area will be found profitable. To the east of Schumann Canyon it is probable that the field may be extended beyond the present southeast limits of the proven area. Recent drilling .shows that this extension will probably continue for at least a 'Second Annual Report of the State Oil and Gas Supervisor, pp. 204-207. Third Annual Report of the Stat? Oil and Gas Supervisor, pp. .361-369, 372-384. Fifth Annual Report of the State Oil and Gas Supervisor. Summarv of Operations California Oil Fields, April, 1920. Report on the Casmalia Field. By H. W. Bell Pp. 10-4 0. 104 CALIFORNIA STATE MINING BUREAU. mile along the axis of the fold southeast of Well No. 13, Escolle Union Oil Company. The Santa IMaria field proper, known as the "old field," lies to the east of the Casmalia field in a group of low hills known as the Solomon Hills. The structure consists of a series of small, sharply-folded anticlines lying to the south and west of ]\Iount Solomon. The greater part of the surface of the field is covered by a small thickness of sands and clays of the Fernando formation, whicli bear no relation to the accumulation of the oil and serve only to obscure the real structure. Beneath the Fernando is found the Monterey formation, the upper portion of which outcrops in Pine Canyon and on the Newlove lease of the Union Oil Company. At both of these localities, the ^Monterey is bituminous and numerous seepages and burnt shale areas are in evidence. The upper portion of the IMonterey contains what is known as the '1st zone,' which is productive to the extent of about ten barrel wells in certain portions of the field. The oil runs in gravity from 16° to 20°. Beneath the 1st oil zone, the Monterey is composed of a thickness of about 1600 feet of blue shale, which serves as an impervious capping for the 2nd oil zone, which lies at the base of the INIonterey. The oil of the 2nd zone has collected in the fractured flinty shale that makes up this portion of the Monterey. The gravity varies from 20° to 38°. This zone was formerly the chief source of production in the field. The 3rd zone, now the chief source of production, is probably in the uppermost Vaqueros, at its contact with the Monterey. The oil measures in this zone are true sands. Underground contour maps indicate that this contact between the IMouterey and the oil sand of the Vaqueros may be a fault contact, particularly in the vicinity of the Newlove lease of the Union Oil Company. Fig. 2, Section 2, shows the general structure of the field. Detailed reports covering the underground structure and water con- ditions can be found in the various annual reports of the State Oil and Gas Supervisor.^ The total proven area in March, 1921, was 4620 acres. The total daily production in December, 1920, was 8006 barrels of oil. The aver- age number of wells producing during this month was 232, with an average daily production per well of 34.5 barrels of oil and 29.5 barrels of water. The limits of the field have been defined by past drilling and there will probably be no appreciable extension of these limits. There, however, remain extensive areas, particularly in the western portion of the field, that have not been drilled up to date. The Cat Canyon field lies along the canyon of that name, north and east of the Santa Maria field. The formations exposed on the surface consist of terrace deposits and Fernando sancLs and clays. The total thickness of the terrace deposits is about fifty feet and the Fernando outcrops from 600 to 800 feet. The Monterey shale is present beneath the Fernando and it is both the source and reservoir for the oil, whicli averages about 15° in gravity. The structure, according to Arnold and Anderson,^ consists of two parallel anticlines, about two miles apart, with a northwest-southeast 'Firstt Annual Report of the State Oil and Gas Supervisor, pp. 19S-203, 205-211. Second Annual Report of the State Oil and Gas Supervisor, pp. 202-204. Third Annual Report of the State Oil nnd Gas Supervisor, pp. 370-371. =U. S. Geological Survev. Bull. 322. Geology and Oil Resources of the Santa Maria Oil District. By R, Arnold and R. Anderson, 1907. PETROLEUM RESOURCES OF CALIFORNIA. 105 trend. The most .soiitlicrly fold, known as llie Gate Ridge anticline, according to surface dips runs along the top of the ridge on the south side of Canada del Gato. Drilling, however, has shown that the actual productive fold in the underlying iMonterey lies about one mile north of where Arnold and Anderson located the axis, from dips in the Fer- nando. The axis, as determined by drilling, apparently runs through Palmer Union No. 1 in Sec. 26, T. 9 N.. R. 33 W., S. B. M., and thence southeast, passins: near the location of the Associated Oil Company's well. Recruit No. 1, oh Sec. 31, T. 9 N., R. 32 W., and from there con- tinuing southeast to the head of Howard Canyon. The principal area of production lies at the northwest end of this fold in Sec. 26. The Bell wells of tlio Pan-American Company, located on the Bell Ranch and on the axis of the fold, a.s shown by Arnold and Anderson, have failed to produce any appreciable amount of oil and the majority of them have been abandoned. The second anticline runs along the ridge mark- ing the north side of Caiiada del Gato and its location on the surface in the Fernando beds is slightly north of its location in the underl3'ing Monterey. The principal area of production on this fold centers around Sec. 30, T. 9 N.. R. 32 W., S. B. M. The oil measures in the Cat Canyon field are true sands and probably represent sandstone beds in the middle ]\lonterey. The wells vary in depth from 24G0 to 3100, according to their position on the fold. The total area of proven land in March, 1921, was approximately 1850 acres. The total daily production in December, 1920. was 2333 barrels of oil. The average numl)er of producing wells during this period was 40, with a daily average production per well of 56.3 barrels of oil and 8 of water. It is probable that the limits of the proven areas may be extended to the southeast along the axes of both folds. Detailed reports on the underground structure may be found in the annual reports of the State Oil and Gas Supervisor.^ The Purisima Hills field lies to the south of the proven area above described. That portion of the field which may be considered as proven occupies the western end of the Purisima Hills, in the vicinity of the Lompoc grade, and the area has been frequently called the Lompoc field. The dominant structure of this region is a broad anticline running west from Red Rock IMountain to the Lompoc Grade, where it disap- pears under the terrace deposits of Burton ]\lesa. At the west end, near the Hill wells of the Union Oil Company, the south flank of the fold is faulted. This fault appears to have influenced the accumulation of the oil, as the wells in the vicinity of the fault zone have been the best producers. The formations consist of the Fernando and the Monterey, the latter being both the source and reservoir for the oil. The total proven area in March, 1921, was 1193 acres. The total daily production in December, 1920, was 1367 barrels of oil. The average number of wells producing during this period was 27, with an average daily production per well of 50 barrels of oil and 70 of water. Surface geologs^ indicates that the field may possibly be extended. That portion of the Purisima Hills between the Lompoc field and Red Rock ^lountain. a distance of approximately ten miles, may be considered as possible oil territory. The most favorable localities would be along "First Annual Report Slate Oil and Gas Supervisor, pp. 203-204. SeconcJ Annual Report of the State Oil and Gas Supervisor, pp. 210-219. 106 CALIFORNIA STATE MINING BUREAU. the axis of the anticline above mentioned and along an eastward continu- ation of tlie fault zone noted. There are large deposits of asphaltum in the Monterey near Red Rock IMcuntain, indicating that the INIonterey carries petroleum in the eastern end of the Hills. The possibility of finding production in commercial quantities depends on the presence of the thick blue shale zone, which acts as a capping for the 2nd and 3rd oil zones of the Santa Maria field. If this blue shale is present in tlie rurisima Tlills, overlying the fractured flinty ])ituminous shale zone as exposed in the vicinity of Red Rock Mountain, then the possibility of a large area in the eastern portion being productive is good. Five wells are now being drilled to test out this area. Harris No. 1 and Careaga No. 87 of the Western Union Company are located on the axis of the anticline about one mile east of the proven area. Pinal Dome No. 1 is located on the eastern extension of the fault zone and has apparently the best chance. At the eastward end of the Hills, the Gen- eral Petroleum Corporation is drilling a well in Drum Canyon on the axis of the fold and about two miles farther east, near Red Rock ]\Ioun- tain, the Standard Oil Company is drilling a well. The territory west of the Lompoc field is known as Burton IMesa. The surface formation is mainly terrace deposits, with some underlying INIonterey exposed in the canyons. On account of the overlying terrace deposits the true structure of the region is obscure. Wherever the IMon- terey is exposed it apparently is folded into a number of small anticlines. At the western end of the Mesa, along the coast line, hard flinty Monterey shale with numerous seepages is exposed. The area might be considered as worthy of further investigation. Outlying Areas. The general area of the Santa Ynez Mountains west of the town of Santa Barbara offers no inducement for drilling. The core of the range is composed mainly of Eocene and Oligocene sandstones and Vaqueros sandstone. Along the edge of the Santa Ynez Valley there are small areas of highly-folded Monterey shale, and along the coast there is a very small thickness of Monterey shale exposed along the sea cliffs, overlying the Vaqueros sandstone and dipping about 40° to the south. The Mon- terey here is slightly bituminous in places. The general structure of the range is that of a great monocline, which dips from the high central ridge at an angle of about 45° to the south. The San Rafael Range is composed mainly of Cretaceous and Eocene sediments, all highly folded and containing no evidence of petroleum. On the south flank, north of the Santa INIaria Valley, there is a large area of highly-folded Monterey shale, probably representing the lower portion of this formation. In the southeastern portion of this area, l)etween Foxen Canyon and Sisquoc River, the JMonterey is overlaid by thin patches of Fernando, at the contact of which there are large deposits of asphaltum as well as in the shale itself. The asphaltum deposits are located along Asphaltum Creek and Zaca Creek and on Labrea Creek, north of the Sisquoc River. The territory is not favorable for well drilling, but offers a possibility of mining and distilling the bituminous deposits. In the hills due north from Los Olivos, the Fernando is exposed in a broad anticline, which has been tested by the Standard Oil PETROLEUM RESOURCES OF CALIFORNIA. 107 Company, in two wells. No oil was encountered and the drilling demon- strated what is evident from a study of the territory to the north, that is, the Monterey is missing on this fold, the wells penetrating Franciscan serpentine after going through llie Fernando. In prospecting for oil in tiie Santa ^laria district the following facts must be borne in mind: (1) All production is in the lower portion of the ^Monterey and in one instance in the uppermost Vaqucros. (2) Com- mercial production is oidy found when tlie lower flinty productive zone of the IMonterey is capped by the impervious blue shale l3ody. (3) The Fernando is not productive, nor do folds in the Fernando reflect the structure in the underlying Monterey. Area of the Cuyama Valley. Tlie Cuyama Valh-y lies along the nortii flank of the San Kafael Mountains, which locally are sometimes known as the Cuyama IMountains. Along its western portion the valley forms the dividing line between Santa Barbara and San Luis O])isi)o counties. The extreme eastern portion lies in Ventura County. The geology and oil resources of the major ])ortion of the valley luive been reported on by the United States Geological Survey^ and the conclusion of English's report is as follows: "Conditions in Cuyama Valley. "As thf association of sandy beds witli tlie shale which was the original source of the oil is one of the most inipoi'tant conditions in productive fields, the discussion of the Cu\ama N'alley area will he based on the areal distribution and character of such shale. The shales present in the Cuyama Valley are the thick mass of pre- Monterey shale, tlie shale in the Vaqueros formation, the Maricopa shale, and the locally well-developed Whiterock Bluff shale member of the Santa Margarita for- mation. "There appears to be little possibility of obtaining oil from beds associated with the dark clay shale of the pre-Monterey rocks, which crops out over considerable areas in the rugged mountains on the south side and in the western part of the Cuyama Valley. Lithologically similar shale of Cretaceous age on the west side cf the Sacramento Valley contains oil seeps, and in the Santa Clara River valley some of the oil probably originated in the Topatopa (Eocene) shale, which is of much the same type and possibly of tlie same age as the shale of the pre-Monterey in this area. However, in the area examined no seeps or other evidence of the presence of oil were found or were reported in this shale, or in overlying beds, so that it seems unlikely that any appreciable amount of oil derived from it is present either in the interbedded sandstones or in porous overlying formations. Much the same reasoning may be applied to the dark clay shale and interbedded sandstone of the Vaqueros formation, which constitutes the main mass of the Calienle Range. "Of the other formations, the pearl-giay shale in the vicinity of Montgomery Potrero, the pinkish Maricopa shale on the flanks of the Caliente Riinge, and the "chalky" Whiterock Bluff shale member of the Santa Margarita are the only beds that are of a lithologic type in which it seems likely that oil may have originated, and only those general areas in which one of thesa' shales crops out or is believed to be pre.sent lielow the surface are thouglit to be likely to produce oil. "The gi'ay diatomaceous shale which is mapped as a part of the Pato red member of the A'aqueros and which underlies the prominent white sandstone of the Vaqueros at Montgomery Potrero has a very irregular distribution, being absent along the Monterey and pre-Monterey contact west of Branch Canyon and on the south side of the tilted block of pre-Monterey rocks at the head of Castro Canyon. It probably underlies the western part of the prominent anticline north of Salisbury Potrero, but its slight thickness and meager content of diatomaceous material make it insignificant in comparison with the great mass of diatomaceous shale in productive fields. No seeps arc known to occur in this shale or in associated porous rocks. The chance of obtaining commercial fiuantiti'es of oil from beds overlying this shale in the area mapped is therefore probably slight. "The Maricopa shale, in the uprier part of the Monterey group of the Calienle Range, has a maximum thickness of about 2000 feet, and although less diatomaceous than the typical "Monterey shale," it may have been the source of considerable quan- tities of petroleum. Two or three oil seeps have been reported in this shale. 'U. S. Geological Survey. Bull. 621-M. Geology and Oil Prospects of the Cuvama Valley. By W. A. English, 1916. 108 CALIFORNIA STATE MINING BUREAU. "The white diatomaceous shale in the Whiteroek Bluff shale member is locally over 10 00 feet thick and may have been the source of considerable quantities of oil. It is significant that the seep south of Whiteroek Bluff occurs at a point where this shale is thickest as well as most diatomaceous. Areas of favorable structure under- lain by eitlier this or the Maricopa shale would deserve very careful consideration as being possibly productive. Unfortunately no such areas of favoi-able structure were found. "The structure in tlie Caliente Range is unfavoraljle for the collection of oil from eitlier of these formations, as they are overlain by porous beds only on the Hanks of the anticline, where the beds stand nearly on edge. The Whiteroek Bluff" shale member of the Santa Margarita west of the fault that trends northwest from the mouth of Morales Canyon is thin but very diatomaceous. However, the broad syncline in which it lies is not a favorable structure for the accumulation of oil. "Between Whiteroek Bluff and the outcrop of the Santa Margarita formation, west of Salisbury Canyon, and northward to Cuyama River is an area in which a determination of either the structure or the distribution of the formations that may have been a source of oil is uncertain because of the presence over most of the surface of the Cuyama formation and terrace gravels. As the underlying structure is unknown this area cannot be classed as definitely barren of oil. although there is no positive evidence to i-ecommend it as an area favorable for oil accumulation. The small area of pre-Monterey rocks overlain by the Morales member of the Santa Margarita south of Whiteroek Bluff is important as showing that the diatomaceous shale does not extend directly south from Whiteroek Bluff to the edge of the valley. In the absence of more definite evidence it may be assumed that the diatomaceous shale is absent south of a line drawn from the small area mentioned to the point where Aliso Canyon enters the main body of pre-Monterey rocks. Northeast of that line the Cuyama River, and the Whiteroek Bluff shale between Salisbury and Aliso canyons is less diatomaceous than at Whiteroek Bluff. If one may judge of the amount of oil formed in the slxxle by its thickness and the amount of diatom skeletons pi-esent in it, then only a comparatively small quantity of oil should be e.vpected to occur in this area. Any oil which may have originated in these shales might have collected either in interbedded sandstones or at the base of the Cuyama formation, having seeped up from the eroded edge of the underlying shale. A well of compara- tively shallow depth located on any one of a number of low local anticlines in tiie Cuyama formation would test the sands at the base of that formation, as the Cuyama formation in this area is probably not over 200 or 300 feet thick. This thickness of beds would probably not give sufficient covering to retain any large quantity of oil, and the very marked unconformity between the Santa Margarita and Cuyama formations suggests that a large part of the oil might have escaped from the lower beds before the overlying beds were deposited, so that on the whole the prospect of obtaining more than small quantities of oil, if any, in this area is not promising. "Oil Seeps. "The largest seep reported, and the only one seen by the writer, occurs in the bed of the Cuyama River south of Whiteroek Bluff. The river has cut down about twenty feet through Quaternary stream deposits and is fiowing on bedrock, here diatomaceous shale of the Whiteroek Bluff member of the Santa Margarita. During an earlier epoch the river cut down to the same level and formed a much wider valley in which the stream gravel and sand that form the vertical banks of the present stream were deposited. It was during this earlier epoch in which the river flowed upon bedrock that most of the oil now seen at this locality seeped up from the underlying shale of the Santa Margarita. While tlie river was flowing on bedrock and while it was depositing three or four feet of sand a number of pools of oil were formed here, some not less than 100 yards across. The oil in these pools saturated the surface sand, which was later covered by sediment and preserved and which is now traceable along the vertical river banks as thin strata of oil sand interbedded with white sand and clay. At one place, which may have been the original seep, an asphalt-like oil has escaped from the underlying shale very recently. The shale near this seep has irregular dips and the oil may have come up along or close to a fault. "At least three seeps of oil are reported in areas of Maricopa shale of the Mon- terey group in the Caliente Range, but at the time of the writer's visit, they could not be located and had probablv ceased to How. A reported seep in a small canyon in the NW. \ Sec. 15. T. 11 N., R. 2S W.. could not be found. There is said to be a snuill hrea deposit on a ridge in the SE. \ Sec. 14, T. 11 N., R. 28 W. A seep reported in the creek bed near the forks of Taylor Canyon, in the SE. J Sec. 24, T. 32 S., R. 19 E., has also apparently ceased to exist. "Wells Drilled for Oil. "The Webfoot well, in a nairow gulch on the north side of Ballinger Canyon, in the SE. 5 Sec. 2, T. 9 N., R. 2 4 W., was started about 1905, and drilling continued intermittently for a number of years. It is said to have reached a depth of ISOO feet without encountering any oil. This well starts in nearly vertical beds of brown sandy shale of the Monterey group. "The Grand Prize Oil Company, composed of Bakersfield and local people, drilled a well in Sec. G, T. 11 N.. R. 28 W., at about the same lime as the Webfoot well was drilled. This well is said to have reached a depth of 600 or 700 feet without obtaining PETROT>EUM RESOURCES OF CALIFORNIA. 100 any oil. It starts in tho "chalky" white shale of tlie Whiterock Bluff shale member of the Santa Margarita ami probably reaches the underlying pre-Monterey rock. It is located on the south Hank of a broad syncline." It is apparent from the above report that the possil)ility of any appre- ciable production of oil in the Cuyania Valley is slight. Coast Area of Santa Barbara County. The only other area in the county, outside of the Santa ]\Iaria District, that contains any oil pos.sil)ilities is tho narrow coastal strip, from Goleta to tlie Ventura County line. The territory contains one small proven district, namely the Summerland field, located about eight miles east of Santa Barbara. There are possiblities, however, that other similar fields may be developed in this area. The coastal strip, with an average width of almost five miles, lies between the rugged, steep Santa Ynez Range and the Pacific Ocean. The Santa Ynez Range at this point is composed of highly-tilted rocks of Eocene and Oligoeene age, corresponding to the Topatopa and Sespe formations of Ventura County. The organic shales of the Topatopa have been the source of some oil which has collected in beds along the contact with the Sespe. In the area under discussion, this condition exists in the foothill area of the Santa Ynez, east of Summerland, in Tore, Oil and Santa ^Monica canyons Along the coastal strip, the oil is found in the Fernando sandstone, having accumulated there from the underlying Monterey. This is the condition that exists in the Summerland field, the .structure of which is a steep monocline in the underlying ^Monterey with small minor folds in the overlying Fernando. The field is located along the water's edge and the majority of the wells are drilled from wharves extending out into the sea. The depths range from 100 to 600 feet and the gravity from 14° to 16° Baume. In December, 1920, the total number of wells producing was 120. The average production per day per well was 1.4 barrels of oil and 14.2 barrels of water. The total daily production from the entire field was 168 barrels of oil. The most favorable location for new fields in the coastal area would be where the Fernando is folded in anticlines, overlying the IMonterey. Two such areas are apparently present; one lying in the hills between Santa Barl)ara and Goleta and the second between Santa Barbara and IM'ontecito. In the first area a well was drilled some years ago on the Hope Ranch by the Associated Oil Company, called the Recruit well. A depth of 2800 feet was reached and considerable gas was encountered. The foothills of the Santa Ynez ^lountains, northeast of Sununerland. in the vicinity of Toro and Santa ^lonica, offer a possibility of small production of Eocene oil. At Rincon there are some shallow wells which have obtained slight showings. The region between Santa Barbara and Carpinteria, includ- ing the Summerland field, has been reported in detail by the United States Geological Survey.^. 'U. S. Geological Survey. Bull 321. Geology and Oil of the Summerland District. By R. Arnold, 1907. no CALIFORNIA STATE MINrSTG BURKAU. Fnllo\viii,2r is a portion of the report refjardiug the old wells in the outlying areas aud future possibilities of these areas: "Wells Near Loon Point. "Several prospect wells have been put clown in the Fernando formation near Loon Foint, about a mile east of the Summerland field, but none were successful, although oil sands with traces of oil were penetrated in most of them It is the opinion of the writer that the paucity of petroleum is due to the position of tlie Fernando beds, which are believed to overlie here the nonbituminous Vaqueros rather than the petroliferous Monterey as they do farther north in the Summerland field. The position of the Loon Point wells relative to tlie anticline is apparently advantageous and the only reason that can be assigned for their nonproductiveness is that stated above. "Wells Near Carplnteria and Rincon Creek. "Several wells, at least one attaining a depth of over 3000 feet, have been sunk on the lowlands in the region near Carplnteria and the mouth of Rincon Creek, five to eight miles east of Summerland. Traces of oil were found in all of them, but none so far have been highly successful. In all the wells the strata penetrated beneath the superficial Pleistocene deposits have been the Monterey (middle Miocene) bituminous shale, which lies in steeply dipping positions throughout this coastal belt. "The most important and deepest well is tliat of the Columbia Oil and Asphalt Com- pany, located on tlie north side of the railroad one-half mile east of the asphalt mine ai Carplnteria. It is put down in line with the axis of a sharp auticline which extends into the ocean about a mile east of the mouth of Carplnteria Creek, near the edge of the area shown on tlie map. No definite information concerning the well was obtainable at the time of tlie writer's visit (October. 1906). but the following notes were gleaned from various sources : The weil penetrates shale throughout the greater part of its depth, is about 3000 feet deep, and encounters artesian water with a head of 12 feet at 100 to 150 feet, asphaltum at 1200 to 1400 feet, and oil in sandy layers in the lower 100 feet. The oil in the sump is black and heavy, although it is said by the operators that oil of 37° gravity was struck near the bottom. The oil is accompanied by a strong gas pressure. Gas was also encountered with the asphaltum between 1200 and 1400 feet, forcing the asphaltum up in tlie hole for a distance of ISO feet when first struck. Only a small amount of oil was on the sump, indicating that the production, of the well is probably not large. "Several years ago a well was sunk in the shale at the edge of the bluff about one- fourth mile east of the asphalt mine. Heavy oil was struck, but it was too vi-scous for pumping, and the well was abandoned. The casing of this hole still protrudes from the ground, and a heavy oil, accompanied by considerable gas, is slowly escaping from it. It is said that a second well was simk a short distance farther northeast, but that no oil of consequence was encountered in it. As the first well is near the northern limit of a highly disturbed zone, it seems very likely that the reason no oil was encountered in the second well was because it penetrated beds which were so little fractured that the oil had no channels of migration through them. "In 1894 a 4 by 6 foot well was dug to a depth of 3.^4 feet by P. C. Higgins, on the seashore one-half mile west of the asphalt mine. Purplisli bituminous shale, with casts of the fossil Pecten peckhami Gabb, was the only formation penetrated, and no oil was encountered. "A 400-foot well was drilled by J. Heath on the Hill ranch just north of the mouth of Rincon Creek, oil being struck in small quantities from 1.50 feet downward. "Watts« gives tlie following reference to prospect wells of the Arctic Oil Company, east of Carplnteria : "'Well No. 1. sevpn miles south of Rincon Creek. 1825 feet deep: formation, red sandstone; no oii. ^yell No. 2, 50 feet distant from Well No. 1, 2100 feet deep; forma- tion, red sandstone; no oil. Well No. 3, on Southern Pacific Railroad, IJ miles east of Carplnteria; conglomerate and sandy shale to 700 feet; shale and sandstone to 1200 feet : liquid asplialtum ; well abandoned.' "The conglomerate here mentioned is probably the Pleistocene gravel and sand, which overlies the Monterey shale to a depth of over a hundred feet in the region northeast of Carplnteria. "At the time of the writer's visit to Carplnteria (October, 1906), it was reported that a well was being sunk at Shepards, two miles northeast of the mouth of Rincon Creek, but no data concerning its depth or the formation penetrated were obtainable. "Wells in the Mountains Northeast of Summerland. "Several wells have at different times been put down in the Topatopa formation (Eocene) in the mountains east and northeast of Summerland. The wells have'all been located near oil springs or seepages, and have without exception yielded traces and some of them commercial quantities of oil. Light yields and lack of proper trans- portation and market facilities have discouraged development, and at the present time none of the wels ar^ being operated. .Among the wells are tho.«e of the .^anta Barbara Oil Company in Oil Canyon, the Occidental Mining and Petroleum Company in Toro Canyon, the Santa Monica Oil Company in Santa Monica Canyon, and the Pinal Oil Company at tlie moutli of Arroyo Parida. These will be briefly described. "Two wells were drilled by the Santa Barbara Oil Companj' iri Oil Canyon about 33 miles northeast of Summerland. The rocks here exposed are the overturned upper Topatopa shale, which dips steeply at angles ranging from 60° N. to vertical ; oil springs occur in them in the immediate neighborhood of the wells. The wells start down in >Bull. California State Mining Bureau. No. 19, 1900, p. 104. PETROLEUM RESOURCES OF CALIFORNIA. Ill the shale, but may penetrate to the stratigraphically higher, but actually lower upper sandstone bolt. The wells are between ;"iOO and 600 feet deep, and yielded small quan- tities of oil and much gas. "Seven wells and one tunnel havo been sunk by the Occidental Mining and Petroleum Company in Toro Canyon, about SJ miles nortlieast of Sumnierland and three-fourths of a mile west of those of the Santa Barliara Oil Company just described. The for- mation at the Occidental wells is tlie same as tliat in Oil Cannon, and tbc wells doubtless derive their oil from the same zone. The wells range in depth from 200 to 1100 feet. Four of tliem were classed as productive and tlirec dry. altliougli tlie latter contained traces of oil. No. 1 is said to have produced a total of .")000 barrels and No. 5 was rated as a five-barrel well ; thf average for tlie productive wells was about two to three barrels a dav each. In August. 1895. only one well was pumping, and the oil from this was largelv' mixed with water. The oil is black and of 17° Baume gravitv when it first comes" from th-3 wells, but on standing for a little while drops to 14°. The tunnel is 'i^^ feet long and inns in a N. 1*1° K. direction into tlie mountains. It penetrates sandstone composed of quartz, feldspar and green and reddish minerals, interbedded witli the grcenisli slialc. It yielded little oil Init much water, and tlie latter is now being used in Summerland. An analysis of tliis water is given on page 24. "The well of the Santa Monica Oil Company is located two miles nortli of Tarpinteria, near the mouth of Santa ^lonica Canyon. It starts down in the lowest Sespe sand- stone, which here dips 60° S., 10° W.. and penetrates the alternating .sandstone and shale of the uppermost Topatopa. A yield of fight barrels a day of IS" amber-colored oil accompanied bv strong gas pressure was encountered at 400 feet. At TOO feet a strong flow of sulphur water 'drowned out' the oil and the well is nosv abandoned. "Tlie I'inal Oil Company is nutting down a well at the mouth of Arroyo Parida Canyon, about 3.^ miles east of Summerland. It penetrates the lowest Sespe sand- stone and the uppermost Tojiatopa alternating sandstone and shales, which here dip 60° S. It is thought that the well will reach the oil in sands under a certain shell at a depth of something more than 1000 feet. "General Conclusion. "The conditions of structure do not appear to favor the probability of striking remunerative deposits of oil by deep drilling. It is true that oil would probalily be encountered in wells 2000 or more feet in depth put down almost anywhere over the territory underlain by the Monterey shale, but the steep dips and close texture of the shale apparently preclude the accumulation of such great deposits of oil as are found in fields where the roi-ks are less steeply inclined and more porous. "Region Near Carpinteria. "The last paragraph is as applicable to the region about Carpinteria and to the east as far as the contorted condition of the shale extends as it is to that territory about Summeiland which is underlain by the Monterey. More or less oil is inclosed in the shale and in local interbedded sandstones, but it does not appear likely that heavy producers will ever be encountered in a region of such distortion and fracturing as is prevalent in tlie Monterey shale all along this part of the coast, although in certain facies of the shale fracturing .seems to be essential to the migration of the oil within or through it. "Region West of Monteclto. "It is thought that wells sunk deep enough to penetrate the basal beds of the Fer- nando formation in the region of the Montecito anticline, which extends indefinitely west-northward from the coast one mile west of Montecito Landing, will strike deposits of oil of about the same quality as the best of that encountered at Simimerland. "Region of the Topatopa Formation (Eocene) Northeast of Summerland. "In the light of the development which has already taken place in Toro, Oil, Santa Monica and Arroyo Parida canyons, it seems almost certain that light producers (averaging from two to six or eight barrels a day of 14° to 18° oil), lOOO feet or less in depth, could be put down at many place.s along the contact between the upper Topa- topa shale and sandstone zones or the contact between the Topatopa and Sespe forma- tions in the region northeast of Summerland. The oil-bearing strata in both of these belts are apparently confined to the upper part of the Topatopa, and to obtain productive wells is simply a question of locating places whore the structure appears most advantageous for the accumulation of the petroleum. The region near the Arroyo Parida fault, toward the east end of the area covered bv the map, appears promising, although the wells here, especially on the north side of the fault, would have to go much deeper to strike the oil zone than they do at the tested localities." In Bulletin 63, .California State ^Mininer Bureau, "Petroleum in Southern ("alifornia." l)y Paul AV. Prutznum, liJl:}, pages ;«9-415, a complete list of all wildeat wells in the county and their results up to 1913 is given. McLaughlin and AVaring^, in their bulletin, give a somewhat briefer account of Santa Barbara County. 'California State Mining lUiroau. Bull 69. Petroleum Industry of California, 1914. By R. P. Mcl.^ughlin and C. A. Waring. 112 • CALIFORNIA STATE MINING BUREAU. Ventura County. The topographic features of Ventura County consist of a high, rugged mountainous area in the northern half of the county, a series of river valleys draining the south central portion, and finally another moun- tainous area, along the coast in the southeast quarter. The mountain area of the northern half of the county may be consid- ered as the meeting place of the Santa Ynez and San Rafael ranges with the Tehachapi IMountains. The elevations of the different peaks vary from 3000 to 8800 feet. The Cu3'ama River drains the northwestern part, and Sespe and Piru creeks drain the southern portion. Pine Mountain is the name given to the ranges just south of the Cuyama River and the ranges just south of Sespe and Piru creeks are known as the Topatopa Mountains. The river valleys of the south central portion are three in number and contain the proven oil fields of the county. The most northerly is known as Ojai Valley, which has an east and west trend, but drains into the Pacific through the north and south trending Ventura River, Sulphur Mountain, a 25p0-foot range, separates the Ojai from the valley of the Santa Clara River, the second and largest of the group. South Mountain and Oak Ridge, with elevations as high as 3000 feet, form the southern boundary of the Santa Clara and separate it from the Simi Valley, the third and most southerly of the group. The Santa Monica IMountains, reaching elevations of 3000 feet, lie to the south of the Simi Valley and foi m a mountainous area along the coast in the southeast quarter of the county. The Santa Clara and the Simi join west of South Mountain, forming a large fertile plain, which continues as far northwest as the Ventura River. GEOLOGY AND OIL POSSIBILITIES OF THE COUNTY. Northern Half of the County. The mountain area of the northern half of the county offers little or no inducement for drilling. The northeastern corner in the vicinity of Mount Pinos, Frazer INIountain, San Rafael Point and IMcDonald Point is occupied by a mass of granitic rock, with occasional patches of lime- stone. Between INIount Pinos and Frazer jMountain. in the vicinity of the Lockwood Valley_, there is a small area of Tertiary, and seepages have been reported from this area. In the region north of the Cuyama Valley and south of the Kern County line and east of the Santa Barbara County line, the rocks exposed are sediments of iMiocene age. A portion of this area has been mapped by the United States Geological Survey^ and no evidence of oil was found. In the region south of the Cuyama River, west of Ozena and north of the headwaters of the Sespe Creek, Fairbanks- has reported that the rocks exposed are of Chico age. The southern portions of the mountain areas are composed of Avhat Eldridge and ArnokP called the Topatopa formation (Eocene) and 'U. S. Geological Survey. Bull. 621-M. Geology and Oil Resources of the Cuyama Valley. By W. A. Englisli, 1916. ^Twelfth Annual Report of the State Mineralogist. Geology of Northern Ventura County. By H. W. Fairbanlis. Pp. 493-526, 1894. nr. S. Geological Survey. Bull. 309. The Santa Clara Valley, Puente Hills and Los Angeles Oil Districts. By G. H. Eldridge and Ralph Arnold. PETROLEUM RESOURCES OF CALIFORNIA. 113 8—13322 OAK KIDGE ANTICLINE, VENTURA C'UUNTY (LOOKING WEST Fli I IM THE SANTA I'AIU.A OIL (.'O.'S ritOI'EUTY ; STItATA EXl'OSKH AltE THE RED AND WHITE SANDSTONE BEDS OF TUB SESPE FORMATION; AXIS OF THE FOLD IS AT THE LEFT OF THE riCTUREl. PETROLEUM RESOURCES OF CALIFORNIA. 113 wliich may in'opcily bo divided into .Martinez, Megano.s and Tejon. In the extreme southern portions of this area the Topatopa and the over- lying Sespe (Oligoeene) are oil bearing, and tliis region will be discussed ill conneetion with the pi'oven fields of the Ojai and lower Sespe xaUeys. The statement made at the beginning of this article, that the mountainous area of the northern half of the county offers little induce- ment for drilling, is based on the highly-tilted and crushed condition of tlie formations and the total lack of any authentic indications of petro- leum. I'lider the most favoral)U' conditions the most that could be expected from a mountainous region like this would be extremely small wells. Central Portions of the County — Area of the Proven Fields. This region has been mapped ])oth by the United States Geological Survey^ and the State Alining Bureau,- and the reader is referred to these reports for detailed descriptions of these areas, as only a general description of the fields with possibilities of extension will be given here. OJAI VALLEY FIELDS. The formations consist of a broad mass of Monterey shale exposed along Sulphur Mountain and in the hills north of the upper Ojai Valley. Between these two areas of Monterey there is a narrow strip of Sespe red beds (Oligoeene). The contact of these beds with the Monterey on either side is that of an overthrust fault (see Fig. 7, Sec. AB). The oil which has been formed in the diatomaceous shales of the Monterey has migrated and collected in the overlying sandstone beds of the Sespe in the vicinity of the fault zones. The principal area of development is on the property of the Pan-American Petroleum Company in the upper Ojai Valley. The wells are located in an area between the two faults and penetrate probal)ly to the Sespe beds that are in contact with the Monterey. The wells are small and the oil is of heavy gravity. The outlook for any further increase in production is doubtful. The most favorable region for extending the limits of the field is eastward towards Sisar Canyon, along the axis of the faults. An attempt has been made to secure production on the axis of an anticline in the Sespe beds about one to one-half miles south of Nordhoff. The wells known as the Pirie w^ells obtained slight showing but were commercial failures. The Sisar Creek field lies about two miles east of the upper Ojai field above described, and is considered as a part of the Ojai Valley fields. The field lies about one-eighth of a mile north of the east-west trending portion of Sisar Creek and between Santa Paula Canyon and the north- south trending portion of Sisar Creek. The structure and geology are as follows: The two overthrust faults which are the dominant structures 'I'. .S. Geological Survey. Bull. 309. Santa Clara Valley-Puente Hills and Los Angeles Oil Districts. By G. H. Kklridge and R. Arnold, 1907. V. S. Geological Survey. Bull. 691-M. Structure and Oil Resources of the Simi Valley. By W. S. W. Kew, 1919. -California State Mining Bureau. Bull. 63. Petroleum in Southern California. By P. W. Prutzman, 1913. Pp. 21-155. California State Mining Bureau. Bull. 69. Petroleum Industry of California. By R. F. McLaughlin and C. A. Waring, 1914. Pp. 381-402, PI. Ill, map folio. 8—13322 112 ■ CALIFORNIA STATE MINING BUREAU. — • — »"g»' j«" l oj. — j-mj». uvv. — J.11C oiri-iiia V lara vaiiev, i'uente Hills and IjOS Angeles Oil Districts. By G. H. Eldridge and Ralph Arnold. PETROLEUM RESOURCES OF CALIFORNIA. 113 whii'li may properly bo divided into ^fartinez, ]\Iegano.s and Tejon. In 1 he extreme soutliern portions of this area the Topatopa and the over- lying Sespe (Oligocene) are oil Ijearing, and this region will he discnssed in connection with the proven fields of the O.jai and lower Sespe valleys. The statement made at the beginning of tliis article, that the mountainons area of the northern half of the county offers little induce- ment for drilling, is based on the liighly-tilted and crushed condition of the formations and the total lack of any authentic indications of petro- leum. Tnder the most favorable conditions the most that could be expected from a mountainous region like this would be extremely small wells. Central Portions of the County — Area of the Proven Fields. This region has been nuipped both by the United States Geological Survey^ and the State ]\lining liureau.' and the reader is referred to these reports for detailed descriptions of these areas, as only a general description of the fields with possibilities of extension will be given here. OJAI VALLEY FIELDS. The formations consist of a broad mass of Monterey shale exposed along Sulphur JNIountain and in the hills north of the upper Ojai Valley. Between these two areas of Monterey there is a narrow strip of Sespe red beds (Oligocene). The contact of these beds with the Monterey on either side is that of an overthrust fault (see Fig. 7, Sec. AB). The oil which has been formed in the diatomaceous shales of the Monterey has migrated and collected in the overlying sandstone beds of the Sespe in the vicinity of the fault zones. The principal area of development is on the property of the Pan-American Petroleum Company in the upper Ojai Valley. The wells are located in an area between the two faults and penetrate probably to the Sespe beds that are in contact with the IMonterey. The wells are small and the oil is of heav}' gravity. The outlook for any further increase in production is doubtful. The most favorable region for extending the limits of the field is eastward towards Sisar Canyon, along the axis of the faults. An attempt has been made to secure production on the axis of an anticline in the Sespe beds about one to one-half miles south of Nordhoff. The wells known as the Pirie wells obtained slight showing but were commercial failures. The Sisar Creek field lies about two miles east of the upper Ojai field above described, and is considered as a part of the Ojai Valley fields. The field lies about one-eighth of a mile north of the east-west trending portion of Sisar Creek and between Santa Paula Canyon and the north- south trending portion of Sisar Creek. The structure and geology are as follows : The two overthrust faults which are the dominant structures 'I'. S. Geological Survey. Bull. 309. Santa Clara Valley^uente Hills and Los Angeles Oil Districts. By G. H. Eldridge and R. Arnold, 1907. U. S. Geological Survey. Bull. 691-M. Structure and Oil Resources of the Simi Valley. By W. S. W. Kew, 1919. -California State Mining Bureau. Bull. G.3. Petroleum in Southern California. By P. W. Prutzman, 1913. Pp. 21-155. California State Mining Bureau. Bull. 69. Petroleum Industry of California. By R. F. McLaughlin and C. A. W^aring, 1914. Pp. 381-402, PI. Ill, map folio. 8—13322 114 CALIFORNIA STATE MINING BUREAU. O^ PETROLEUM RESOURCES OF CALIFORNIA. 115 of the upper Ojai X'alli'V iiieryi' al>(»ut oiic-rourth ol" a mill- iioi'tli aiul oast of tlie point wluTe Sisar Creek turns from a south direetion and flows oast. From tliis point oast the stiuoture consists of a single over- thrust fault, in whicli the oldei- Ses[)e and T(ipat()i)a beds on thi' noi'th side of the fault have been thrust over tlu' .Monterey beds of Sulphur ^lountain region. The oil has migrated from the diatomaceoiis shale of the ^lonterey and eolleeted in the sandstone beds of the Sespe along the contact. The majority of wells are located north of the fault line and start down in the Sespe. penetrating the oil sands along the fault contact. The wells are small and there is little possibility of any considerable increase in production. However, the eastward limits of the field towards Santa I'aula Canyon can probably bo extended with profit. In .March. 1!)21. the total proven art'a in tlie Ojai Valley field.s was 2J)7 acres. In December, 1!)20, the total daily production was 192 barrels of oil. The average numl)or of wells ]>i"oducing at this time was 42 and the daily average proiluction per well was 4.-1 barrels of oil and 3.9 barrels of water. SANTA PAULA FIELD. This name is applied to a number of isolated areas of production lying along the south side of the Sulphur ^Mountain and Santa Paula Ridge. Those areas on the south side of Sulphui- ^Mountain and west of Santa Paula are found at the heads of Aliso, Wheeler and Adams canyons and those on the south side of Santa Paula Ridge and east of Santa Paula are foimd at the head of Onlauf and Timber canyons. Tlio structure that luis caused the accunuilation of the oil is a great overthrust fault, which starts at the extreme western end of Sidphur ^Mountain on the V^^ntura River and runs oast along the south flank of the mountain, crossing Santa Paula Canyon about one mile south of Sulphur .Mountain Spi-ing aiul thence continuing to the ea.st along the steep south flank of Santa Paula Ridge to Timber Canyon. At this poinl it merges with the fault from the Sisar Canyon field and the two continue as a single fault, running northeast around the l)as(^ of ]Mount San Cayetano to Sespe Creek. The fault zone is clearly visible, being marked by a steep escarpment, along Sulphur ^Mountain and Santa Paula Ridge and it abruptly terminates the headwaters of the various canyons above mentioned. The formation lying to the south of the fault, and which has been overthrust by the older formations to the north, consists of Fernando sands, clays and gravels. The formations to the north of the fault consist of the broad area of ^lonterey slude, occupyinu' the Sulphui- ^Mountain region. Owiiig to the convergence of the two faults at Timber Canyon, this Monterey area gradually thins and becomes wedge shaped towards the east and finally disappears entirely at Timber Canyon. From Timber Canyon east, the formation luirth of the fault is the Topatopa sandstcme and shale. The magnitude of the faulting has thrust this formation over the Fernando, and the jMonterey is entirely lacking on the surface but is undoubtedlv present beneath the Fernando, The south end of Sec. AB, Fig. 7 shows the structure on the south side of Sulphur Mountain. The oil has formed in the Monterey and has 116 CALIFORNIA STATE MINING BUREAU. collected in the Fernando sands along the fault contact. The oil runs in gravity from 24*^ to 28° Baume in the Sulphur area and averages about 32° gravity in the Timber Canyon area. The total proven area of the Santa Paula field in March, 1921, was approximately 170 acres. The total daily average production in December, 1920, was 139 barrels of oil. The average number of welLs producing during this period was 65, with a daily average production per well of 2.2 barrels of oil and 0.7 of water. The wells start down in the area of the fault zone and penetrate to the plane of contact, the average de|)th being about lOOU feet. The width of the field north and south of the fault is limited to a distance of about one-fourth of a mile, and there can be no appreciable extension in this direction. In an east and west direction, along the axis of the fault, tliere is much room for development and there is apparently no reason why there should not be a continuous line of small wells joining up the now isolated groups. There has been no development along the fault east of Timber Canyon and this area affords a possibility of small well development. The possibility of commercial returns depends upon whether the overthrust faulting has not buried the oil sands at too great a depth. VENTURA FIELD. This field lies along the Ventura River and consists of two proven areas. The most southerly area is about two and one-half miles north- east of the town of Ventura and is commonly known as the Ventura Avenue field. The .structure consists of a simple anticlinal fold, known as the Ventura anticline, trending approximately east-we.st, and crossing the Ventura River at right angles. This fold continues westward from the river for a distance of about eight miles, finally striking out to sea about one-fourth of a mile northwest of Sea Cliff Station. Eastward from the river it extends a distance of about six miles, chdng out on Aliso Creek. The proven area consists of about 300 acres on the axis of the fold at the point where it crosses the Ventura River. The formations exposed on the anticline consist of Fernando sands, clays, .shales and gravels. This formation acts as the reservoir for the oil, which wa.s probably formed in the underlying IMonterey. To date, two oil zones have been recognized — an upper or light oil zone, extending from 1900 to 3000 feet and yielding oil of from 48° to 56° Baume gravity ; the second, or heavy oil zone, is found below 3000 feet and yields oil of from 30° to 38° Baume gravity. The light oil zone at one time gave promise of being capable of producing wells as high as 150 barrels per day. but careless drilling by some of the pioneer companies has resulted in this zone being flooded by water, so that the present production is extremely small. The second zone has not to date been thoroughly explored, but it is apparent that it is capable of yielding from 200- to 300-barrel wells and possibly more in deeper sand yet to be encountered. The limits of the field have not been defined and it is probable that they can be extended for some dis- tance westward from the Taylor wells of the Shell Com]niny, along the axis of the fold, and a similar extension may be made to the east beyond the Lloyd wells of the Associated Oil Company. A detailed report on PETROLEUM RESOURCES OF CALIFORNIA. 117 the iindergroiinil condition may be found in the fifth annual report of the State Oil and Gas Supervisor.^ The second proven area on the Ventura River consists of a small sec- tion on the ea-st side in the vicinity of Fresno Canyon and oast of La Crosse Station, covering about fifty acres. It may be considered as a continuation of the small proven areas along the south side of Sulphur ^Mountain, which were described under the article on the Santa Paula field. The geolopy and method of accumulations are similar. The yield of the wells is small and the commercial value of the district is somewhat doubtful. There is no doubt but what the area could be extended eastward along the fault zone as far as the producing wells in the Aliso Canyon, a distance of six miles. Outside of the two areas al)ove mentioned, there is apparently no other district along the Ventura River that offers any inducement for drilling. In the district lying west fnmi tlie Ventura Kiver to the Santa Bar- bara County line, there is only one possible area of development, and that has been described under the article on the Ventura Avenue field, namely an extension of this field along the axis of the fold, westward from the Taylor wells of th- Shell Company. It is most probable, how- ever, that this extension can not be carried much more than a mile west of the river. The extreme westward end of the Venture Avenue anti- cline has been tested in two wells ])y the General Petroleum Corpora- tion and f(.und unproductive. These wells were known as the Hobson wells. Hol)son No. 1 was located on Padre Juan Canyon and Ilobson No. 2 on ^ladranio Canyon. The general geology of the remainder of the district is as follows: The Fernando, which outcrops along the axis of the Ventura Avenue anticline, continues northward for about one and one-half miles to a point just south of Red ^lountain, where it is abruptly faulted against the IMonterey. This Monterey consists of a narrow area of shale, overlying the Sespe beds of Red ^Mountain. It continues westward, coming out on the coast between Punta Gorda and Rincon Point, at which place it is slightly bituminized. From Red iNIountain northward, the principal formation exposed is the Sespe, consisting mainly of red and white sandstone beds. At the base of the Santa Ynez Range, north of the Santa Ana Valley, it rests against the Topatopa. This area of Sespe contains neither favorable structure or any indication of oil. District Along the North Flank of South Mountain and Oak Ridge. This area includes two proven areas, the South [Mountain field and the Bardsdale-^lonteliello district. The structure may be considered. in a broad sense, as that of a great anticlinal fold running east and west along the north flank of the mountain, from Santa Paula to Wiley Can- yon. The axis of the fold, however, plunges and emerges at several different points, with the result that the actual structure consists of a series of isolated domes, an idealcondition for the accumulation of oil. Beginning at the west, these domes are four in number: One in the 'California StatP Mining. Fifth annual report of the State Oil and Gas Supervisor. Summary of Operation.s. February, 1920. Report on the Ventura Oil Field. By Lawrence Vander Leek, 118 CALIFORNIA STATE MINING BUREAU. vicinity ol" Moi'ji'an and AVillard Canyon, forming tiio South ^luuntaiu field; the seeond at the mouth of Grimes Canyon, forming the Bardsdale area ; th(> third in tlu^ vicinity of Guiberson Canyon, forming the ]\Ioute- bello area; and finally, the fourth in the vicinity of AVilcy Canyon, this last area being unproven to date. The oldest formation in the district is composed of medium coarse sandstone, conglomerate shales and clays of vivid red, purple and white coloi's. These beds are of Sespe age and are exposed in the highest points of the several domes. From an economic standpoint it is the most important formation, as it contains the connnercial oil sand of the district. Overlying the Sespe red beds is found the ^Monterey series, consisting of Va. The Petroleum ]\lidway, in the northwest corner of Sec. 5, drilled a well and encoun- tered a fair showing of oil between 2500 aiul ;3000 feet. The well, how- ever, was abandoned on account of mechanical difficulties. The Oak Ridge Oil Company has a well about one-fourth of a mile south of the Petroleum Midway location, and has to date only encountered gas. The Amalgamated Oil Company is also testing the area out with a well in the northeast corner of Sec. 6. The Bardsdale and IVIontebello areas are regarded as one field and the district is commonly known as the Bardsdale field. The total daily average production in December, 1020, was 1340 barrels of oil. The avei'age number of wells producing was 134. with a daily average production per well of 10 barrels of oil and 1.1 of water. The gravity of the oil averages about 25° Baume. About two miles east of the Montebello area occurs the last and most easterly dome in the Sespe. along the north flank of Oak Ridge. This dome is located on Sec. 1, T. 3 N., R. 19 W., and may be called the Wiley Canyon dome. This area remains unproven today. Two wells have been drilled here and abandoned, but the records and results are lacking. The sur- face evidence indicates conditions similai- to the Monteliello area, and it may be considered worthy of testing. 120 CALIFORNIA STATE MINING BUREAU. SESPE CANYON AREA. This district includes the territory drained by the Big and Little Sespe and their branches. Some of the ilrst development work in Yen- tnra County took place in this area. Of late years, however, on account of the small yield, development work has lagged. At the present time the producing areas are confined to the E. -J of Sec. 1, T. 4 N., R. 20 W., at the junction of the Big and Little Sespe Creeks; and to an area on the Little Sespe in Sec. 6, T. 4 N., R. 19 W., and finally on the head- waters of Tar Creek, in Sec. 33, T. 5 N., R. 19 W. The geology and structure are more or less complicated. The forma- tions exposed consist mainly of the Vaqueros, the Sespe and the Topa- topa beds. The structure consists of a number of sharply-folded, plunging anti- clines and s>nclines, in some cases overturned. The oil apparently has been formed in the shales of the Topatopa formation and has migrated and collected in the sandstones at the base of the overlying Sespe. The gravity of the oil varies considerably. AVells on the Big Sespe showed heavy black oil of about 13° Baume. The Tar Creek wells i)roduce medium gravity oil of about 26' Baume. The Kentuck wells also average about 26° Baume. The wells on the Little Sespe run about 20° Baume. The average depth of the wells is about 900 feet. There is no water trouble. The total proven area in ^Nlarch, 1921, was 440 acres, this figure being based on the actual present production. It is probable, however, that if the old abandoned properties which could easily be made productive were considered, the proven area would be doubled. The total daily production from the field in December. 1920, averaged about 100 barrels of oil. The total number of wells producing was 21, with an average daily production per well of 4.5 barrels of oil and 0.8 of water. There is still considerable room in the field for small well-development. The most favorable locations are along the axis of the anticline in the vicinitv of the Los Angeles Oil Company wells, on Little Sespe Creek ; on Sees. 21, 28, 32 and 33, T. 5 N., R. 'l9 W., all located about the headwaters of Tar Creek ; on See. 1, T. 4 N., R. 20 W., in the vicinity of the plunging overturned syncline from which the Kentuck wells are producing, and in the northern portion of the same sections along the axis of an anticline running through the Big Sespe Oil Company's wells. The area along Big Sespe Creek is not so encour- aging, on account of the heavy oil ]U'oduced. On Coldwater Creek, just above Devil's Gate, there is a well-defined anticline which is probably capable of yielding heavy oil. Many of the old abandoned properties are also capable of being repaired and put on a producing basis. PIRU FIELD.. This name is given to a group of proven areas lying north and soutli of the Santa Clara River in the vicinity of the towns of Piru and Camulos. The proven areas north of the Santa Clara are located between Hopper Canyon and Piru Creek. South of the Santa Clara they are located along Torrey, Eureka and Topo canyons. The unproven area between Hopper Canyon and Sespe Creek and between Piru Creek and the Los Angeles County line will also be considered here. PETROT-EUM RESOURCES OF CALIFORNIA. 121 The general structure of these areas consists of sharply-folded anti- clines and synclines. The oil-bearing formation is the ]\Ionterey (Modelo), the production coming from sandstone beds (probably Vaqueros) interbedded in the organic shale. From Piru Creek east to the Los Angeles County line, the principal formation exposed is the Fernando, which, however, appears to be barren of any appreciable amount of oil. Following is a portion of ^McLaughlin and Waring 's report on this region : "East of the Sespe and Fourfork creeks the geologic formations are folded along nortliwest-southoast axes which, witli a few exceptions, turn to an east-west direction east of Hopper Canvon. The Vaqueros and Monterey are the important oil formations In this region. Most of the drilling has been done in the canyons where they cut across likciv anticlines. "Probably the most favorable drilling territory in this vicinity is along the north flank of the Nigger Canyon anticline and along the Hopper Canyon anticline. There are exposures of oil sand in the Vaqueros formation on the west face of Oat Mountain, and also in the Monterey formation from tlie mouth of Pole Canyon to Fairview Canyon. "The principal oil zones are tliose of the Monterey (lower Modelo) formation, con- sisting of shallow sand interbedded in the Monterey shale, and those of the Vaqueros sandstone Interbedded in the Vaqueros shale. The oil zones of the Monterey range to 1000 feet below the surface, while those of the Vaqueros range usually from 1500 to 2000 feet. "The maximum initial production per day for some of the older wells of the Sunset, Modelo and Harris Oil Companv was 7.5 barrels. Wells as a rule drop off rapidly for the first few months and then maintain a more steady production for many years at rates of from n to 25 barrels. The oil varies from 14° Baume in the shallower Sunset and Harris wells to over 30° Baume in some of the Modelo wells. The deepest Harris well obtained the lightest oil and the largest production of the group. In the long run wells over 2500 feet deep are said to be no more profitable than shallower ones. "A few wells have been drilled as far east as San Martinez Chiquito Canyon and Castaic Valley. These wells started in the Fernando formation and drilled to depths ranging from 500 to 2500 feet. Traces of oil and asphalt are reported from some of these wells. Probably if oil in paying quantities is struck in this region it will be deep because of the eastward plunging of the geologic structural axes." Following is a portion of Eldridge and Arnold's report on the Torrey, Eureka and Tapo canyons group of wells : "The productive territory of the Torrey anticline, forming what is known as the Torrey field, embraces an area of about one square mile, the length being twice tlie breadth and lying with the strike of the rocks, which gradually bend from N. 65° W., the direction prevailing on tlie side of the flexure, to northwest, north-northwest, and north as the strata round its end. The axis of the anticline passes close to the northern edge of the field, the wells, with a few exceptions, having been drilled in the strata of gentler dip, 30° to 40°. south of the axis. In all there are between 50 and 60 wells, aligned in seven or eight concentric arcs, in accordance with tlie curves assumed by the outcropping strata. Tlie wells nearer the axis penetrate the red and gray banded argillaceous sandstone that has been correlated with a portion of the Sespe formation, while those more distant are perhaps entirely confined to the sandstone and shale of the Vaqueros. "It is said to be usually impossible in this field to identify horizons in one well with those in another, even though the two locations are adj.acent. Tlie oil sands also vary in thickness from a few feet to 150, and even the thicker beds, it is reported, cannot be identified from well to well. It is, however, the opinion of the writer that consider- able order might be worked out with the aid of carefully prepared cross sections. "Tlie oil has a gravity of 30° to 35° Baume and resembles that. derived from the same formation north of the Santa Clara, especially that from the region of Fourfork and Tar creeks. The depth of the wells varies from GOO to 2000 feet, the deeper wells being those farther away from the axis of the fold. North of the Torrey anticline the productive territory is apparently confined to the east end of the field where the distance from the syncline immediately north and from the fracture possibly accompanying it is greatest. "Concerning the extent of the Torrey field beyond the present developed area, it may be said with some degree of assurance that to the west and north it is likely to be limited by structural conditions' to nearly the existing lines. In the other directions no prediction can be made. "Eureka Wells. "The wells of Eureka Canyon are located in its lower reaches, most of them being grouped at the sharp turn half a mile above its mouth. The geology of tlie immediate region is somewhat doubtful, but if the structure is that of a highly compressed com- pound fold, as suggested on page S2. the locus of the wells is not far from its anticlinal axis ; moreover, the developed territory is in the vicinity of a prominent ?urve in the stratification planes, the axis having been pushed somewhat northward between Eureka 122 CALIFORNIA STATE MINING BUREAU. and Torrey canyons. The wells penetrate the Vaqueros sandstone, conglomerate and shale, but whether any of the beds are duplicated it is impossible to determine. Suoh duplication may have taken place, but it has had practically no effect on the productive- ness of the territory. The wells are located a little over a mile north-northeast of the Torrey group, the geology of the two fields being Quite distinct. "Twenty-one wells were in operation or drilling at tlie time of the writer's visit. They vary in deptli from 600 to 1200 f(>et. and the strata passed through according to the logs, "embrace sand, arenaceous shale, dark, adobe-like clay, and the usual 'hard shells' of the drillers. The cliaracter of the beds varies every 50 to 125 feet in depth, but sandstone predominates. Oil .sand, so-called, appears to be encountered at depths of 540 to 620 feet. Water is found botli in the upper parts of the wells and beneath the lowermost oil sand recorded. Well No. 20, of the group at the turn of the canyon, is the only one in which pebbles are reported. Thesie are, perhaps, a local development of one of the more prominent sandstones that lie near either the summit or the base of the Vaqueros beds. Usually but a single oil sand shows in a well, and tt is the opinion of the superintendent that tlie producing horizon is the some tliroughout the field. "The gravity of the oil averages, it is said, 24° Baum§, but in some instances rises to 2 6°. This difference, as compared witli the Torrey oil, is inexplicable, for both are believed to be derived from the same formation. Their horizons, however, may be different, and in the Eureka field the sediments appear to be coarser, while the strata are far more fractured, if tlie interpretation of the geolog>- here given is correct. The latter feature would tend to permit the easier escape of the lighter hydrocarbons, leaving behind the heavier oils, which now constitute the product. "The yield has been from 1 to 4 barrels per day. The field has. however, never been one of large production, but from the records the wells appear to have maintained their suppl.v witli remarkable uniformity. "No evidence of the red and gray banded series of probable Eocene age has been found in any of the holes in this field. "Wells have Vjeen drilled in* the main fork of Tapo Canyon and also in each branch of a westerlv tributary. Those at present producing lie along the east fork of this tributary. They are four in number, although from their designation. Nos. 12 to 15 inclusive, it is to be inferred that several otliers have been in existence in earlier days. Indeed, one or two of these old wells still contain a slight amount of oil. The producing wells are sunk in northward-dipping sand.«tone and shale a mile north of the axis of the Tapo anticline. They yield at present from 5 to 4 barrels of oil per day. The gravity is 20° to 24° Baume, the 20° oil being produced by the well highest up in the canyon and lowest as to the strata penetrated. These wells are about 200 feet apart and range in depth from 4 60 to 1200 feet. The oil sand is encountered at 235, 465. 940 and 865 feet, from the well farthest up the creek to that lowest down, respectively. The wells lowest on the dip are the greatest producers. The dip of the measures is from 50° to 60°. and it is impossible to say that a single bed produces oil for the entire field, althougli this is suggested by the increasing depths of the wells in the direction of the dip. More or less water is pumped with the oil. and it is the opinion of the superintendent that the two are mined and come from the same bed. The amount of water, liowever. is sliglit. the proportion being given as 1 of water to 40 of oil. Inas- much as water-bearing sands overlie the oil sands it may be tliat a leak occurs which would account for its presence with the oil. Water was also found beneath the oil sand in the well farthest up the gulch and has been encountered in some of the wells now abandoned. "The whole of the lower half of the Vaqueros strata exposed in Tapo Canyon shows a greater or less impregnation with petroleum. No unusual amount appears to have been assembled in proximity to the axis of the main anticline, and it may be tliat the productive territory is a particularly rich portion of the series of beds which, from some cause or otlier, has held its oil better than the great mass of the beds in the region. From the surface no reason can be seen for the enrichment of one portion of the formation over another portion, and except for strong seepages in proximity to the wells one locality might as readily have been chosen for development as another. "The logs of the Tapo wells sliow a succession of blue clay, brown shale, gray sand- stone, fine to coarse, and in one instance a trace of conglomerate. The thicknesses of these several materials, wliich are constantly repeated, vary from 5 to 200 or more feet, the average being, perhaps, between 20 and 75 feet." In ]\rareh. 1921, the total proven area was 865 acres. The total daily average production in December, 1920, was 336 barrels of oil. The average number of wells producing was 75. with a daily average pro- duction per well of -4.5 barrels of oil and 5.2 of water. The area is not encouraging except for a small well-development. SIMI VALLEY FIELD. The Siini field lies along the north side of the Simi Valley between Santa Susana and Simi. The chief area of production is around the month of Tapo Canyon. From there on west to Brea Canvoii there are a few scattering wells. PETROLEl'M RESOURCES OF CALIFORNIA. 123 Tlic iiiaiii stnu-tiu-e consists of the Sinii antielino. This fold starts about one-half mile east of the mouth of Tapo Canyon and runs due west to a point just west of the canyon, where the strike of the axis ehangfes to a soutlnvest direction, so that it crosses Hrea Canyon at its mouth. The dips on the tlanks vary from 15° to 30° and there is a plunfie to the axis of ai>proximately 3° to the southwest. East of Tapo Can>on the formation exposed on the axis of the fold is of Tejon age. West of the canyon the jdun^e of the folds has caused the Sespe to overlie the Tejon. TAPO CANYON WELLS. In the vicinity of the Tapo Canyon wells (principally of the Pan- American I'etroleum Company) the oil has ajiparently been formed in the carbonaceous shales of the ^Meg-anos (Koeenc) and has eolleeted maiidy in the overlyinji sands of the Tejon and to a lesser extent in the Sesjjc formation. TIk^ oil is of a lisiht-ijreen color and averages in gravity about 38^ Baunie; some wells, however, produce as high as 42° gravity oil. Along the axis of tlie fold the first oil is encountered at about 300 feet and productive sands are logged down to 1600 feet; wells down the dip are, of course, deeper. The sands are extremely lenticular and no correlation is possible from well to well. The field is api^irently limited in a north and south direction to an area of 3000 feet about the axis of the fold. Along the axis, in a westward direction, there is every indication that the field may be extended for a considerable distance. Eastward from Tapo Canyon to the head of the valley, the possibilities may be summed up as follows: There is a chance for small-well production of three to four barrels per day in the areas between Tapo Canyon and the first large canyon to the east (a nnle distant from the proven area). The structure consists of the eastward end of the Simi anticline, and in Sees. 2!) and 30, T. 3 N., R. 17 W., some oil has accumulated along a fault in the Tejon. At the licjid of the vallex'. in the low hills north of the state highway, the structiii-e consists of a monocline dipping about 25° to the west. The formations beginning at Ihe bottom consist of the Chico, IMartinez, ]\[eganos and Tejon. It is possil)le that wells sunk in the Tejon might yield 3 to 4 barrels per day. In the general area north of the Tapo field, including the southern slope of Oak Ridge and the Santa Susana ^Mountains, the prospects of any development are unfavorable. Area in the Vicinity of Brea Canyon. Westward from Tapo Canyon there are three small groups of wells. The first consists of the Simi wells of the Pan-Anu'rican Petroleum. These are located near the west cpiarter corner of Sec. 34, T. 3 N., R. 18 AV., and consist of five wells, only one of which is producing. The wells start down in the Sespe about three-quarters of a mile north of the axis of the Simi anticline and eiu'ouiiter oil sands from 1600 to 2100 feet. The oil is black and of about 20° Baume in gravity. The yield is apparently going to average al)out 20 barrels per well. The axis of the fold has not yet been tested in this vicinity. The second and third groups are located in Brea and Los Alamos canyons, and consist of the Tninn Oil Company, Cafiada del La Brea wells and the r 124 CALIFORNIA STATE MINING BUREAU. Pan-Amei-iean Scarab -wells. The Union wells are in Brea Canyon, about one mile north of the axis of the Siini antieline, and the Scarab wells are in Los Alamos Canyon abont 1| miles north of the axis of the anticline. Jnst sonth of the Union wells tliere is a prominent line of oil sands and seepages which may be followed to the west of Brea Canyon for about a mile and a half. Both groups of wells are appar- ently drawing their oil from these outcrops, the dip being about 25° to the north. The beds exposed are red, purple and white sands and clays of the Sespe formation. Tlie oil encountered is black and of about 18° Baume in gravity, the yield, per well, being about 15 barrels per day. At the mouth of Brea Canyon, a mile south of the Union wells, are three abandoned dry holes all located approximately on the axis of the Simi anticline. They consist of the Dabnc}- & Roberts well, in the SEJ of See. 5. T. 2 N., R. 18 W., which was^ drilled to a depth of 2680 feet : the ]\Iilev-Bulev well of the State Consolidated Oil Company, in the SWj of Sec. 4, whieh reached a depth of 1160 feet, and the Hidalgo, in the NE] of Sec. 6, with a depth of 1925 feet. No paying oil sand was encountered in any of these wells, although light showings of oil and gas were reported. The Dabney & Roberts well demon- strates that the Sespe is about 400 feet thick on the axis of the anticline and that the Tejon is apparently not productive along this portion of the fold. This situation, where wells along the axis of the fold fail to produce, while wells located a mile down the flank show production, is a peculiar one for California fields. The only explanation that the writer can offer is as follows: The heavy black oil produced by the Union and Scarab wells from the Sespe beds is not of Eocene origin, but has accumulated in the upper Sespe sands from the ^Monterey shale which overlies the Sespe unconformably a short distance north of the Scarab wells. Apparently the oil did not enter the lower 400 feet of the Sespe which covers the axis of the. fold. In this connection account must also be taken of an igneous dike which outcrops parallel to the axis of the fold about one-half mile nortli of the mouth of the canyon. This intrusion may have prevented the oil from accumulating in sands along the axis. The reason for the Tejon being apparently unpro- ductive may be due to the fact that the quantity of oil capable of being formed by the jMeganos shales was limited and has collected up the plunge of the axis in the vicinity of Tapo Canyon, leaving the remainder of the fold apparently barren. It must be noted, however, that there is some reason to believe that the wells drilled at the mouth of the canyon did not give fair tests to the siiowing reported. The failure of these wells has had the effect of retarding exploration work on the west end of the Simi anticline. Unproven Areas in the Simi Valley. The south side of the valley, from Simi to Santa Susana Pass, con- sists of a monocline in Avhich the Cretaceous, ^lartinez, Meganos and Tejon formations are exposed. The dip is about 25° to the north. The structure may be considered as the south flank of the Simi syncline. The Tejon beds, which are productive on the north side of the valley, PETROLEUM RESOURCES OF CALIFORNIA. 125 show no evidciiec of pi'lrolciiiii lifrc One \\v\l has been driUcd in this distrid. that of the Calabasas Oil Oonipany in the NEj of Sec. 13, T. 2 X.. 1\. 18 W. The well starts down in the Te.ion and a depth of 1900 feet was readied witlioiit ohtainino^ any showing of oil, altliongh gas was reported. See. ("1). Fig. 7, shows the general structure of the valley between Moore Park and Santa Susana. The north side of the valley west of Moore Park and Happy Canyon is known as the Las Pusas district. The structure consists of a great syncline between South ^Mountain and the west end of the Simi anti- cline. The formation exposed on the surface is the Fernando. Along the south flank of South ]\Iountain it is underlayed by ^Monterey shale which is bituminous and contains burnt shale areas. Within the gen- eral synclinal structure thei'e are at least two, and possibly more, minor anticlinal folds. The most prominent of these is found about 3 miles north of Somis, crossing Sulphur and Long canyons at approximately right angles. Tliis fold is now being tested by the Standard Oil Com- pany- on the Doidon tract. AVell No. 1 was drilled to depth approxi- matel}' 2700 feet and abandoned on account of mechanical diiTiculties; no showings were encountered. Well No. 1-A is now drilling. In addition the following wells have been drilled and abandoned in this area without obtaining anv showings: Tlu^ Honda Oil Company's well in tlie SE] of Sec. 29, T. 3 N., R. 20 W., was located on the north flank of the great syncline, and at a depth of 1650 feet went out of the Fernando into the underlying IMonterey, continuing in that forma- tion to a depth of 1875 feet. This well demonstrated that the Fernando on the south flank of South oMountain is not productive. The Cali- fornia Profit Sharing Oil Compan^y drilled a well about one mile north of ^Foore Park and a hundred yards east of the Grimes Canyon road. A depth of 2410 feet was reached in the Fernando. The possibilities that the Las Posas district will produee are not very favorable. That is due chiefly to the fact that the structure is synclinal. The snudl minor anticlines noted above, one of which is being tested by the Standard Oil Company, are apparently only surface flexures in the upper Fernando, or Saugus, and do not influence the accumula- tion of petroleum. West End of the Simi Anticline. At the mouth of Brea Canyon the Simi anticline crosses the valley to the south side and contiiuies westward along tlu' top of the range of liilLs between iloore Park and Somis. In the Tierra Kejada district, south of Moore Park, the formation exposed on the axis is Sespe, with a thin covering of a basaltic lava flow which is characteristic of the base of the ^Monterey in Simi Valley and the South ^Fountain areas. Further west, in the hills near Somis, the formations consist of sands, clays and gravel of the Fernando. The low range of hills west of Somis is probably a contin ual ion of TITe fold, though^ gQO^^ jjps -to prove this are r are. J. B. Dabney drilled a well here, on the Perkins property, about ;:jThiles west of Somis and a mile soutli of the highway ; AP~oi l was encountered^ From the log' it is evident that the follo\ving format.ionsf arp present: Fernando to about 1700 feet; Monterey sliale 126 CALIFORNIA STATE MINING BUREAU. and Vaqueros sands tone from ;ibont 1700 f(M't to 2885 feet. At that point lava was encTi unU'i-cd and the well aT)ai"uloned . TTie lava~proT)- ahly represents the tlow at the base of the Monterey series. Thg., well may be considered as showing t hat the Fernando and Monterey are not prodnetive along the lower end of the Siini antirTTnl^'. " AtTlie siinie time the well was not drilled deep enough to test the" Sespe and Tejon which are probably present beneath the lava eneonntered at 2885 feet. The general possibilities of the Simi anticline, west of Brea Canyon may be snnnned np as follows: The sti'iid iii'c is fjuofiiltlo. but wells at Bi'ca ("an\on have demoiisti-ated that tlic Srspc and IxJmi arc no t p roductive in that particular rcj^ion. aiul the Dabnej- \veILat the extreme western end shows likewise tha t the Fer nando and Monte- rey are bari'en.^It is, howevei". worthy of being tcstc(i i)y a well located on the axis in the area south of Mooi'c Pai'k with a view to obtaining production from the Tejon. The scci)agis at the foot of Conejo grade indicate that the Tejon is oil hearing somcwiifrc at the lower end of the Simi Vallev. District Around Oxnard, El Rio and Camarillo. The area is fiat and covered with recent soil. There are no surface indications of petroleum. It, however, possesses the possibilities com- mon to flat areas adjoining productive fields, that it possibly may contain buried anticlinal folds of which there is no evidence on the surface. If such folds are present they Avonld, in all probability, be a continuation of the Sonth ^fountain fold in a western direction towards El Rio, and a similar exten.sion of the Simi anticline towards Camarillo. As stated before, the see i^agC-Of iig]jl-gr.e£iL.oil_aJ:_t_he fpoi of. the Cp^PJQ .gJ^"«^.de, indicates^ that. tjie_ Eocene, is_oil-iieaidngj.li lliis portion of thecountVj. District of the Santa Monica Mountains Lying in Ventura County. This district comprises the mountain region in the southeast quarter of the county, lying south of the Simi Valley. In the vicinity of Santa Susana Pass and Chatsworth Peak, the formation is Chico-Cretaceous, which runs west in a continuous botly as far as the vicinity of Simi Piak. Along the lower Hank of the Simi Hills this body of Cretaceous is overlayed by the Martinez, ]Meganos and Tejon. The general dip of these formations is about 25° to the north, and this monocline represents the north tiank of the axis of an anticline which was once I)resent just south of Simi Peak. The axis has been faulted, however, so that only the iiorth Hank and plunging nose of the fold are left. The strike of the fault is approximately east and west, and it may l)e seen in the region about one-half mile south of Simi Peak. The plunge of the faulted fold causes the strike of the Eocene formations along the north tlank to ( hange from east-west to north-south, so that west of Simi Peak they 'nose around' over the Cretaceous, and they, in turn, give place to th(> Vacpieros and ^Monterey in the region just northeast of Newbury Park. The fault apparently ends about a mile PETROLEUM RESOURCES OF CALIFORNIA. 127 west of Simi Peak, so tluit the Monterey Series is still domed and the axis of the fold m:\y \h- reeowiiized near the Cone.jo Oil Syndieate well located ahoiit 12 miles northeast of Xewhiiry Park. The formations exposed south of the Simi Peak fault consist of Vaqueros sandstone and Monterey shale. These continue westward to the vicinity of Newbury Park and the Conejo Valley, and east to the San Fernando Valley in the vicinity of Calaliasas. Two wells are being drilled in this general vicinity and should detei-mine the possibility of this region as they are favoral)ly located on the plunging nose of the faulted anticline. Well No. 1 of the Conejo Oil Syndicate, is located about two miles northea.st of Newbury Park and starts down in ^lonterey shale, which is dipping about 45' to the west. Well No. 1. "Hrhe,'"' of the ("onejo Oil Syndicate, is located about 4 miles noi'theast of Xewbury Park, and starts down in the Vacpieros close to tlie Tejon contact. The'structure is fairly favorable and the region is underlaid ])y the Tejon and ^NFeganos which are oil- bearing on the north side of the Simi Valley. However, there is a total lack of seeps along the outcrops of these beds, such as are common in the region north of Simi Valley. It would seem that if the region is oil-bearing there would be some indication of oil at the outcrops. In the hills just south of the state highway and Newbury Park, the formation is lava, probably belonging to the Vaqueros. From these hills south to the coast the formations consist of highly-tilted areas of Cretaceous and Eocene age. together with some areas of ]\Iiocene lava. The region may l)e considered as unfavorable on account of the sharply- tilted rocks and total lack of any surface indications. At the foot of the Conejo grade, about 3 miles east of Camarillo, there are seeps and a group of shallow producing wells. This is known as the Conejo field. The oil has apparently collected in the recent valley alluvium of a little basin, lying between two areas of Vaqueros lava flows. The oil is light-green in color and of about 16° Beaume gravity. It is apparently of Eocene origin. It has no gasolene content and is practically a ])ure lubricant, indicating that it has migrated a considerable distance and has been filtered. The wells are drilled in the alluvium to depths between 200 and 300 feet, and production has been obtained here for the last twenty years. In 1919 there were 20 wells i)roducing with a total daily yield of 17 barrels of oil and a hundred or more of water. In the latter part of 1920 drilling was started again after a ten-year period of idleness, and the new wells have come in with an initial production of from 30 to 100 ])arrels of oil, followed l)y a rapid decline. The origin and method of accumulation of the oil is obscure ; it is the opinion of the writer that it was formed in the Eocene shales and has migrated along a fault plane up through the lava and into the alluvial basin, as shown in Fig. 8, lying in the basin in a manner similar to water in a lake. The chief interest it has is in demonstrating that there is Eocene oil at the lower end of the county, with a possible accumulation in the Tejon at the west end of the Simi anticline. 128 CALIFORNIA STATE MINING BUREAU. SeaLevel" lOOOft N f 10 o J i ^ «/5 X ><7V . S ^ XT'''/- loooft, — SeaXev'el lOOOft. S C J mmm^^^^^^^'^^^^^^^'V^^^^^ ^iH^^^^^;;r5:^£s^^^^ ^^^^^S^^^^^^^^^^^^'>^^^Pw^ • Fi(,. Ni)i-ili-s(inrli set-lion throuiih the Couejo Field, Veutura County. NORTHWESTERN LOS ANGELES COUNTY. This area comprises, roughly, the territory lying north of San Fernando Pass and west of the Antelope Valley. The northern portion consists of the Sierra Liebre ^Mountains, over which the ridge route of the state highway passes. The central portion consists of a valley area, made up of Soledad Pass. Xewhall Creek and the Santa Clara River Valley, all of which drain westward to the ocean through Ventura County. The southwest corner consists of the Santa Susana ^Mountains, and contains the proven iields of the district. The eastern portion of the Sierra Liebre Range is composed of granite and ancient crystalline schists. The western Cjuarter lying between Castae Creek and the Ventura County line, is composed of sedimentary deposits. These beds have a thickness of well over 10.000 feet. The lower portion consists mainly of shales, Avith thin beds of sandstone. The upper portion consists mainly of yellow-brown medium coarse sandstone, with some minor beds of shale and conglomerate. They are first exposed along the Ridge Route, about six miles north of Castae Station, and the general dip is about 30" to the north, with occasionally a southward dip. The beds continue as far north along the Ricige Route as the Liebre maintenance of way station, at Mhich point they are sharply faulted against the granites by the San Andreas fault. So far as known, they contain no evidence of petroleum. Their age is uncertain, however, they are ai)parently continuous with the Eocene beds of Ventura Count}^ and resemble them to a marked degree in lithology and may, therefore, be assumed to belong to the Topatopa Series. On the southern flank of the Sierra Liebre Range, which forms the northern boundary of the Santa Clara River and Soledad Canyon, in the region north of Saugus, the Eocene beds above referred to are over- lain unconformably by the Fernando. These Fernando beds consist PETROLEUM RESOURCES OF CALIFORNIA. 1-0 of travels white and yellow saiulstotie and yellow elay-shales. They ^/ 1 nn (Se oil-bearnig. A --^^;^-: .« /^^^ abandoned wells drilled here have reported ^i^^^-^^f^^ut faded to ol)tain anv commercial production. In view of this the area may be pousidered as one of doubtful possibilities. ^ -r. ^ » Allowing is a list of the abandoned wells, taken from Prutzman s Report ■} "Wells in Townships 4-17. north ••East Piru Oil Company-This oompany was drilling i^ of Leckler Canyon, noar Uie center of Sec. 6. .J^e results or in s ^^ ^j "Aetna Oil Company-This company has two wels on ^he h . -^^^^^oned because Sec. 8. drilled about 1901. Well No 1 was S45 feet deep ana ^^a ^^,^^g^_ ^ little ?^ t^h^i'ru^tt.^^flKs^'^arrfoirorrt^l'^^vrfboi^^ and was abandoned as a dry hole. "Wells In Townships 5-17 and 5-16. •■Cstalc on Company-TMS well was drined on tl,| j)"* Ijif,"' ^.^S^'SS-^^'!; zarfoio'v-irs: sj/i^^s-r^'o'^Lif-.S' „,'^;; sr.. « e.. .»».. t„is hoie "^°,^„3^Slf°^:;;inS■-rn7»f 'f.;.{9ipa",v/„Hi,ea a j^^^^^^^^ SEl'c']S.="SL"L;rae™S^°o.V'l\ir.'--a°"^^^ "»" "-■'- "•<"" "•» ""•'•N?ew'Sa...lc Oil Company-Thj, company has ';«",,;;f™;rS, r°eU"rteYto b"'',™™ l^oo'^^^e. in°i fSli;!|/w,?lT'a« s.|nf as ? «;,^^S^^^^^^ The Rose well appears to have been almost ex ctly «' .^'^^^t 'f^e suVface, at least, has Castaic well is some distance out on the south limb, which at inc buixdc , a sharp dip." Following is a list of the wells now drilling in this region, none of which have obtained any commercial showing, at the date oi tnis '' Wa\ker-Pearson & McGregor, well No. 1, Sec 32 T. 4 N., R- 15 W., Communitv Oil Producers' Company, wells No. 1 and 2 Sec. 2^, i . 4 rj., R 16 W., Loma Verde Petroleum Company, well No. 1, Sec ^. i- *^-' R 17 W., Fernando Oil Company, well No. 1, Sec. 10^ 1. 4 ^•' ^- J-_' ^•' Tick Canyon Oil Syndicate, well No. 1, Sec. 35 T. 5 N R_ 15 W^, Occidental Petroleum Company, well No. 1, Sec. 35, T 5 N., R. 16 W. The eastern portion of Soledad Canyon is composed of granite and crvstalline schist, together with smaller areas of gravels, sand tutt beds and lava tlows. This portion of the canyon is unsuitable tor ^'^ThrreSn south of Saugus, known as the Santa Susana Mountains, contains the proven fields of this portion of Los Angeles County. These are generally known as the Newhall fields, and were the scene .California State Mining Bureau. Bull. 63. Petroleum in Southern California. By Paul W. Prutzman, 1913. 9—13322 130 CALIFORNIA STATE MINING BUREAU. of some of the first development work in California. The proven areas t-onsist of a numher of isolated i^roups loeated at the heads of Pieo, Towsley, Wiley and Riee canyons. ' These wells are located along the axis of a sharp northwest-southeast fold, known as the Pico anti- cline. The wells ai)parently start down in the Fernando and draw' their oil from sandstone beds in the Monterey Series. These groups of wells lie west of Newhall. In Pico Canyon, on the property of the Standard Oil Company, is loeated the first producing well obtained in California. This well was drilled in 1870 and is still producing at the rate of 3 barrels per day of 38" gravity oil. At tlie head of San Fernando Pass, and in the hills southeast of Xewhall, are located the Elsmere Canyon wells. The formation here consists of Fernando, which is lying unconformably upon tKe granite. The oil is found in the basal sands of the Fernando and is of a heavy gravity, ranging from 14° to 19° Baume. This is in marked contrast to the Pico Canyon wells Avhich run over 30^ Baume in gravity. The structure consists of several sharp anticlines. In Placerita Canyon some oil has been found in an area of cry.stalline schist, having migrated there from the Fernando. This is a freak occurrence and was referred to in Chapter II. The general depth of wells in the Xewhall area ranges from 1000 to 2000 feet. The oil has prol)ably had its origin in the shales of the ^Monterey Series, and has collected in the Vaqueros sandstone and overlying Fernando beds. The total proven area in ^Farch, 1921, was 205 acres. The total daily average production, in December, 1920, was 308 Ijarrels of oil. The average number of wells producing was 77, with an average daily production, per well, of 4.0 barrels of oil and 1.2 of water. The limits of the proven areas are practically set and it is doubtful if the pi'oduction can he increased any in the future. PETROLEUM RE^^OURCES OF CALIFORNIA. I'^l CHAPTKR X. Southern Los Angelks and Orange County. This area iudiules all of Orancr,- County, and that portion of Los An-.les (\,nntv Ivin- soutli of the San F.rnanao Pass and the San Gabriel .Mountains. This is the cliief produem- area of Southern California, and the seeond in the state. Li this report no detailed descriptions will be given of the proven areas, and the reader is referred to tlie bulletins of the (ieolo-ieal Survey^ and the State .Aiming Bureau,- for this information. POSSIBILITIES OF THE VARIOUS DISTRICTS. Santa Monica Mountains. The Santa :\ronica :\rountains lie in the extreme southwestern por- tion of Los Alleles (\)untv, and continue west into Ventura County. Thev offer no indiuement for drilling operations. The general geology is as follows: Beginning at a point on the Los Angeles River north ot Elysian Park and running westward is a body of crystalline rocks, chietlv granite gniesses and schists, which form the core of the range. Alon."' the north Hank, and bordering the south side of the San Fernando Vallcv. the crvstalline rocks are overlay. 'd by the Monterey Series, consisting of white Vaciueros sandstone and diatomaceous Mon- terey shale. The structure is that of a monocline, dipping about -iU to the north This bodv of sediments is continuous from Cahuenga Pass to Calal)asas, where it joints the :\Ionterey Series along the Conejo Grade. On the south Hank of the range from Elysian Park to Sherman the crvstalline core is overlayed at the edge of the foothills l)y the Mon- terev Series and the Fernando. These l)eds dip to the south and torm the Los Angeles Citv and Salt Lake fields which lie out in the flat area about two miles south of the mountains. In tlie hills back ot the Soldiers' Home at Sawtelle, the formations exposed are beds ot sand- stone and shale, probably belonging to the lower portion ot the Monterey Series (locallv known as the Puente). These beds are m turn imderlaved bv the Chico (Cretaceous), which occupies a wedge- shaped area, that gradually widens towards Topango (^anyon. Along the Topango Canvon road the Chico consists of massive sandstone and coarse coiiolomerate, with minor beds of shale. These beds are highly- tilted and"have a general dip to the north. Ah.ng the beach from Santa Monica Canvon to Topango Canyon the lower Puente CMonterey) is overlaid bv bituminous shale probably l)elonging to the upper Puente (.Monterey). The shale is exposed along the sea cliff and the total thickness is iiot over a few hundred feet. n\ S. Geological Survey. Bull. .309. Santa Clara Valley Puente Hills and Los Ansele.s Oil Di.slritt. Bv G. H. Eldridse and Ralph Arnold, 190 <. ^California State Mining Bureau. Bull 63. Pf '•ol^,'? '" J""^'^^^" r^ p^Tc^iauSi^- P W Prutzman, 1913. Bull. 69. Petroleum Industry of California By R. P. Mti^augli lin and C A. Waring. 1914. First, Second and Third Annual Repots ot the btae Oil and Gas Supervisor. Summary of Operations, California O.l Fields. Report on the Montebello Field. By Irving V. Augur. May, 1920. 132 CALIFORNIA STATE MINING BUREAU. The o-onlopfv of the Santa IMoniea Mountains is ehiefly interesting because of the outcrops of IMonterey shale along its borders. The out- crops on the northern flank indicate that the San Fernando Valley is underlaid by the INFonterey, and those on the .southern border and along the coast indicate similar conditions in the region between Los Angeles and Santa IMonica. San Fernando Valley District. The San Fernando Valley consists of a flat, oblong area, completely surrounded by mountains except for the narrow pass at the southeast corner between the Verdugo and Santa ^Fonica mountains, through which the drainage flows by means of the Los Angeles River. The fiat valley area is covered with soil and recent valley deposits which give no hint as to the underlying formation. The one exception to this consists of an area of crystalline rocks and Vaqueros sandstone which outcrops in the small group of isolated hills just east of Pacoima. The geology of the foothills suri'ounding the valley is as follows: Along the southern edge from Cahuenga Pass to Calabasas, the forma- tions consist of Vaqueros sandstone and ^NFonterey shale, dipping in a monocline to the north. From Cahuenga Pass, east to "West Glendale, there is some ^Monterey, but the main formations consist of granite and schist. At the southwestern head of the valley, in the vicinity of Calabasas and south of Chatsworth, the beds exposed are Vaqueros sandstone and ^NFonterey shale. At Chatsworth, and in the vicinity of Santa Susana Pass, massive Chico sandstone outcrops. In the hills iiorth of Chats- worth and west of San Fernando, Monterey shale and Fernando sands, clays and gravels are exposed. This region contains the most favorable structures in the valley for the accumulation of oil. One of these anti- clines starts in the hills between Limekiln and Aliso canyons and runs out into the valley in a southeast direction, terminating in the low group of hills two miles south of the San Fernando Mission. The second fold runs east and west in the hills that surround the San Fernando reservoir. The axis of the anticline passes approximately along the face of the dam at the southern end of the reservoir and continues east towards San Fernando for about a mile, and west as far as Aliso Canyon. These two folds are now being tested by the 'Mission Wells' of the Standard Oil Company, and while depths of 4000 feet and over have been reached, no encouraging results have been obtained. The final results obtained by these wells should prove or disprove the oil possibilities of the valley. The San Fernando Oil and Gas ('ompany is drilling a well about a mile north of the reservoir dam, a location too far north of the axis of the fold to be an adequate test of the region. The northwest head of the valley, in the vicinity of San Fernando Pass, may be considered as a continuation of the Elsmere Canyon structure (discussed in Chapter IX). It is possible that in the vicinity of Grapevine Can3^on, on a continuation of the Elsmere Canyon fold, small Avells of heavy oil and doubtful commercial value may be obtained. The Active Oil Company is drilling a well at the mouth of Grapevine Canyon. In the hills northeast of San Fernando, between Pacoima Wash and the Little Tujunga, the formation consists of j\Ionterey shale and Montebello Iield, Los Angeles County (Looking nty (Looking West Along the Axis of the Fold). PETROLEUM RESOURCES OF CALIFORNIA, 133 Fernando sands and frravels. The Monterey is exposed in a narrow strip running east and west at the edge of tlie hills. Between Lopez Canyon and Pacoinia Wash there are several seepages and the shale is bitnminized. Overlying the shale are the Fernando beds. The dip of both formations' is about 45' to the north. Two wells have been drilled at the edge of the hills and just east of Lopez Canyon. The Crafton well was drilled some years ago and encountered small quan- tities of heavy oil. The San Fernando Oil Company well is at present testing the region and lias to date encountered only small showings of heavy tar. At the month of the Tujunga Valley there are outcrops of Vaqueros sandstone, ]\Ionterey shale and Fernando, which lie on the ci-ystalline rocks of the A'erdugo ^Mountains to the south, and the main San Gabriel Range to the north. In the region consisting of the Verdugo ^Mountains, La Canada, La Crescenta, Verdugo Canyon, the San Rafael Hills and P^agle Rock Valley, the possibilities of obtaining oil are extremely slight. The greater portion of the region is covered witli crystalline rock and only small patches of sedimentary rocks are present. Any drilling here would be a waste of money. The Coastal Plane Area of Los Angeles and Orange Counties. Roughly, this region may be defined as lying between Santa Monica and Newport and south of the Santa Monica Mountains and the San Gabriel Valley. Within it are located the chief proven fields of southern California and it also offers the most favorable opportunities for future development. The proven fields lie roughly along three parallel lines of structure which have a general northwest-southeast trend. These lines of struc- ture consist of a series of donx^s, anticlines and faults along which the oil has accunudated. These arc not in any sense absolutely continuous, but are apparently arranged along these three general parallel lines. The first and most northerly of these begins at the Salt Lake field, near Hollywood, and runs east to the Los Angeles City field and thence southeast through the ^Montebello, Whittier Hills, Brea Canyon and Olinda fields. The second line of structure lies about three miles south and parallel to the first and is separated from it by a narrow syncline. Beginning at the southeast this general structure starts in the Richfield district and runs northwest to the Coyote Hills field and thence to the Santa Fe Spring area, beyond which it has not, to date, been identified. The third and last line is apparently the longest in extent, and is separated from the second by a broad, flat area of about twelve miles in width which is apparently a syncline but which might contain buried folds. Beginning at the southeast, this general line of structure starts in the semi-proven area at Newport and runs thence northwest to the Huntington Beach field and thence to the Signal Hill dome. At this point the strike changes more to the north and the general line of uplift continues through Dominguez, Athens on the Hill, Inglewood, Culver City (Ivy) and finally ends in the proven area around the Wolfskin lease of the West Coast Oil Company about one mile southwest of Beverly. Sec. A. B., Fig. 9, shows the general relationship of these three lines of structure. r.u CALIFORNIA .STATE MINING BUREAU. S||iH ^-^^n^ sili.H ^\^<0 Uidiqeuy I pisij z o I- UJ { CO a a to o bo o o O o a O 01 a o o X g — 3 ;i o PETROLEUM RESOURCES OF CALIFORNIA. 135 Following is a brief clescription of tlie fields that lie along the first and most northerly line of strueture : Salt Lake Field. The Salt Lake field lies at the western ond and (-(miprises the proven area sonth of Sherman and Hollywood. The oil is fonnd in sandstone beds of the Puentf formations and vai-ies from 11- to 18' Banme in gravity. As there are no surface outcrops, the exact structure is some- what obscure. It is probable, however, that the accumulation is due to a major anticline which runs east to west just south of Colegrove and Sherman. Tliis sti-ucture. however, has ))een faulted on both Hanks and contains minor folds witliin it. Sec. 3, Fig. 3, shows a portion of the south faulted tiauk. The limits of the field are practically set. There is, however, a chance to encounter deeper sands, as shown by recent work on property of the Salt Lake Oil Company. The total proven area in .March, 1921, was 904 acres. The total average daily production in December, 1920, was 2240 barrels of oil. The average number of i)roducing wells was 250, with a daily average production, ])er well, of 9 barrels of oil and 10 of water. Los Angeles City Field. The Los Angeles City fields lie in the region between West Lake Park and Elysian Park. Drilling was first started hci-e in 1(S92 by E. L. Doheny, and the area was the scene of extensive drilling oj)erations up to about 1907. Since then, however, there has been practically no development work. This is due mainly to the exhaustion of the oil sands, and the restriction placed upon the drilling of new wells within the city limits. At the present time about 400 of the old Avells are still pumping, and the total daily production averages about 1000 barrels. The structui-c consists of a series of snudl folds and faults in the Puente formation. The majority of the wells start down in the Fernando, but draw their production from the sandstone beds of the Puente. The oil varies from 11° to 18 Baume in gravity. The field has at all times been characterized by shallow wells and small produc- tion, and it is pi'obable that the next few years will see the abandon- ment of the remaining producing wells. The Montebello Field. The next field that lies along this line of structure is the ^Montebello field which is located in the La Merced llilis about six miles east of Los Angeles. The structure consists of a well developed dome in the Fernando formation, and the oil is found in the basal sands of this formation, and ])ossibly in the up[)ermost sands of the Puente. The limits of the field have practically been defined by drilling, and no extension is looked for. There is. however, still considerable room within the proven limits to drill up. This field has been one of the most prolific in Southern (California, but it can l)e considered as having passed the day of fiush production. The total proven area in ]\Iarch, 1921, was 819 acres. The total daily average production in December, 1920, was 30,000 barrels of oil. The total number of wells producing was 133, with a daily average yield, per well, of 240 barrels of oil 136 CALIFORNIA STATE MINING BUREAU. and 19 of water. For a detailed description of the field, the reader is referred to a report by Angur.^ In the region lying between Montebello, East Los Angeles and South Pasadena there is a series of low rolling hills in which there are folds in the Pnente formation. In the little gully .iust southeast of the County Hospital, there are several seepages in what is apparently the basal sands of the Pnente. From tliis it would appear that this region has some possibilities. However, two wells drilled in See. 25, T. 1 S., R. 13 W., failed to obtain production. These wells were the 'Hunting- ton wells' of the Amalgamated Oil Company, and were located on the axis of a small fold just east of East Lake Park. The depths reached in lioth wells were approximately 3700 feet. It is probable that the failure to obtain oil is due to a lack of reservoir formations above the Puente. This genera] region, however, may be considered as worthy of further examination before being condemned. Whittier, Brea Canyon, and Olinda Fields. Across the San Gabriel River from the IMontebello field lie the Puente Hills, and along the southern edge of these hills are located a series of proven areas. These consist of the Whittier, Brea Canyon and Olinda fields. The method of accunuilation and origin of the oil is practically the same in all of these fields, the diatomaceous shale of the Puente (^Monterey) l)eing the original source of the oil which has gathered, either in sandstone beds of this formation, or in the basal sands of the Fernando. The structures along which the oil has accunuilated consist of a series of small folds in the Fernando and a number of faults along the contact of the Fernando and the Puente. All of these fields ha-'e passed the flush day of their production and their limits are practically set. In ]\Iareh, 1921, the total proven acreage in this region was 550 acres in the Whittier field and 2073 in the Brea Canyon-Olinda district. In December, 1920, the total daily average production in the Whittier field was 2768 barrels of oil. The average number of wells producing was 173, with a daily average yield j)er well of 16 barrels of oil and 21 of water. During the same period the total daily average production in the Brea Canyon-Olinda district was 17.756 barrels of oil. The average number of producing wells was 372, Avith an average daily yield per well of 47 barrel;^ of oil and 10 of water. Richfield District. Fields along the second line of structure are as follows : At the eastern end along the Santa Ana River, is found the Richfield district. There are two, and possibly three, separate structures in this area. These consist of a very sharp, short anticline along the west bank of the Santa Ana River, on which are located the wells of the Fullerton Oil Company and the Kraemer No. 1 lease wells of the Standard Oil Com- pany. The extreme, sharp pitch of the flank, and the westward plunge of the anticline, limits the productive area to a narrow strip along the highest point of tlic fold. The axis is apparently not productive 'California State Mining Bureau. Summar>- of Operations California Oil Fields. Vol. 5, No. 11. May, 1920. Report on tlie Montebello Field. By Irving V. Augur. ETROLEUM RESOURCES OF CALIFORNIA. 137 11 No. 1 of the Standard Oil Company. Drilling to at tlio eastward portion of the strnoture is the most is a low group of hills which indicates there is a productive structure underground. Outside of these hills there is no surface evidence of Biohfleld Field, On chfield Field, Orange County. 136 CALIFORNIA STATE MINING BUREAU. and 19 of water. For a detailed deseription of the field, the reader is referred to a report by Aiigiir.^ In the region lying between Montebello, East T^ns Ano-ai-^ — j -^ •■• Pasadena n.^v/^ ^^ - - *^ in th Conni basal has s( R. 13 ton W' axis in hot failnrt Puenti of furl Whittle Acre Piiente a series and 01 is prae of the has ga1 basal Sc aecunni number All of 1 their li acreage in the B average average per well the total was ITj was 372, and 10 Richfield I Fields eastern e There ar These con Santa An Company pany. Tl of the an the highef^ 'Ciiliforni: \vL 5, No. 1 - - p- •• rMigur. PETROLEUM RESOURCES OF CALIFORNIA. 137 much beyond well No. 1 of the Standard Oil Company. Drilling to date indicates that tlie eastward portion of the structure is the most favorable. The second structure consists of the broad anticline on which the main field is located. There is no surface evidence as to where the axis of this fold is located, but a study of the well logs indicates that it runs west- ward from Amalgamated Oil Coinj^any well No. 1 to Union Oil Company 'Towell No. 2, and thence through Petroleum ]\Iidway wells No. 7 and No. 6 and thence through the T^nion Oil Company's wells 'Coyle' No. 1 and No. 3, and 'Chapman' No. 1 and No. 12. From a point near 'Coyle' No. 1 there is a westward plunge to the axis. Wells along the axis vary- in depth from 2900 to 3100 feet, and in some cases as much as 1000 feet of oil sands are open to production. The oil is apparently found in sandstone beds of the Pnente formation. Definite evidence as to this is, however, still lacking. This portion of the field is still in its flush production, and the limits of the proven areas are not yet determined. It is po.ssible that future drilling will ext(^nd the field considerably. About one-half mile southeast of this main productive area is a group of wells located around the Richfield Consolidated property. Produc- tion has been encountered here at about 2800 feet, and this productive sand apparently cannot be correlated witli the sands of the region to the north. AVhether there is a buried fold located here, or whether the sand encountered belongs to a zone that was passed up in the main field, cannot be told from the meager data that is at present available. In INFarch. 1921, the total proven area in the Richfield district was 800 acres. The total daily average production in December, 1920, was 15,360 barrels of oil. The average number of wells producing was 60, with an average daily yield, per well, of 256 barrels of oil and 13 of water. Coyote Hills Field. Lying about 2 miles northeast of Richfield is the Coyote Hills field. This consists of a series of anticlinal domes, apparently three in number. The first of these domes is in the vicinity of the Graham & Loftus lease of the Union Oil Company; the second is located in the vicinity of the 'Ilualde' lease of the Amalgamated Oil Company; and the third consists of the famous dome structure on which the 'Murphy' and 'Emery' leases of the Standard Oil Company are located. This last structure has been one of the most prolific areas in Southern California. The limits of the Coyote Hills field have been practically fixed, and the day of flush production is over. In ^March, 1921, the total proven area was 1885 acres. The total daily average production in December, 1920, was 24,309 barrels of oil. The average number of wells producing was 219, with a daily average yield, per well, of 111 barrels of oil and 25 of water. Santa Fe Springs District. Westward from the 'Emery' lea.se of the Standard Oil Company, the dome structure plunges and is buried for a distance of about 4 miles, emerging again in the Santa Fe Springs area. At this point there is a low group of hills which indicates there is a productive structure underground. Outside of these hills there is no surface evidence of 138 CALIFORNIA STATE MINING BUREAU. the iinderiiToiiiid structure. At the date of this re])ort only one pro- ducing well has been obtained in the Santa Fe Springs field — the ']\reyer' well of the T'nion Oil Company. This well lias been pro- ducing for two years light-gravity oil at approximately a hundred- barrel rate from below a depth of 4000 feet. There is no evidence available as to what the structure consists of. It is probable, however, that it is an antit-linal fitld, with a northwest-southeast trend, antl probably passes just north of Santa Fe Springs. The extent and productiveness of this field can only be determined by actual drilling. Newport District. The fields along the third and most southerly structure are as follows: At the extreme southwestern end is found the semi-proven area of the Newport district. To date no wells of conniiercial value have been obtained here, and it is doubtful whether any better results will be obtained in the future. The structure consists in general of a mono- cline dipping to the northwest. The formations exposed consist of diatomaceous shale and sandstone of the Monterey Series, which rest on sandstone beds prohablx- of Koccne age in the San .loa(piin Hills, and are, in turn, overlaycd b\- IMiocenc beds in the area west of Newport Bay. The .Monterey shale is ap])arently the source of the oil which has collected in sandstone beds of this formation. There are several outcrops of tar sand along the road on the east side of Newport Bay. Approximately 10 wells have bi^cn drilled in this area, nearly all of which have eneou.ntered heavy tar, but have been unable to produce on a commercial scale. This is probably due to the unfavorable mono- cline structure. However, in one portion of the field there is a rather poorly developed anticline, this being due to a slight doming of the Monterey shale beds. The axis of this fold runs approximately east and west, and lies half-way between the Liberty Petroleum Company's well No. 1 and the Interstate Oil Company's well 'Irvine' No. 1. If any further development work is undertaken, a location on the axis of this structure would l)e the most favorable position for a well to test out the district. Huntington Beach Field. Seven miles northwest of Newport lies the newly discovered ITunt- ingt(m Beach fi(>ld. This field centers around the town of Huntington Beach, and a group of low hills just northeast of the town, known as Las Bolsas. The only surface evidence of an oil field consists of these low hills, which serve as a topographic expression of the underground structure and gas found in shallow wells on the property of the Bolsa Chica (iun Club. The limits and structui'e of this field can only be determined by drilling. From such data as is available to date it is probable that the structure consists of an anticlinal dome, with a north- west-southeast trend. Drilling has been almost entirely confined to the northeast fiank of this supposed anticline, so that tlie location of the axis is still undetermined. However, it is probable that it runs in a northwest-southeast direction a few hundred yards west of 'Bolsa Chica' well No. 1 and 'Huntington' No. 2-A of the Standard Oil Company. From the vicinity of Huntington 2-A it curves towards the PETROLEUM RESOURCES OF CALIFORNIA. 139 HUNTINGTON BEACH FIELD, OltANGE COUNTY (LOOKING SOUTHEAST ALONG THE AXIS OF THE FOLD FROM THE BOLSA CHICA LEASE OF THE STANDARD OIL COMPANY). 13322 PETROLEUM RESOURCES OF CALIFORNIA. 139 WiK'h in a southeast direction, so that it T>aS'Ses throuirh well No. 1 of the ninitiniiton rentrnl Oil ('ninpaiiy and well Xo. 1 of tlie TTurst Oil (,'onipany, and slightly east ol" well .Xo. ] of tlie Pantaj?es Oil Company. From this point sontlieast its location is not known. Northwest of Bolsa Cliiea No. 1 the strnctnre a|)i)arently plnny:es sharply to the northwest. 'Toi'i-aiice' No. 1 of the S>1andai"d Oil romj^any. located approximately 2 miles n-^'i'thwest of 'Bolsa (.'hica" No. 1, and appar- ently alont; the continnation of the line of struetnre, has been drilled to a depth of -K)(>0 feet witlionl aii.\ indications of petroleum.' Drillinii' alonir Jhe northeast flank of the sii|)pos('(l fold indic;ites that ]>rodnction may l)e obtained as far as a distance of three-fourths of a mile east of the axis as located above, but not at a distance of a iiiilc Kou^hly, then, the area in which productioji may be expected (based on the data available to date) consists of a sti'ip lyiuir approximately tliree-fourths of a mile on either side of a line di-awn between 'Bolsa Chiea' No. 1 and Pantajjes Oil Company well .\o. 1. The formations encountered on wel's drilled close to the axis are as follows: From to 500 feet, soft, loose sands and gravels, pr(»l)td)Iy belonging to the San Pedro formation ( Ouaternarx) ; fi'om .")()() to 700 feet, conglomerate and boulders are found — this marks the top of the Fernando. Then fol- lows about KiOO feet of shales and sands of the Fernando, in which there are several tar sands. At about 2250 feet the first ])roductive oil sands are encountered. Wells drilled down the dip encounter the fir.st oil at depths from 2(500 to .'UOO feet. To date the oil sands have been penetrated to depths varying fi-oin 300 to 600 feet. Wells drilled on the northeastern Hank have all claimed to have encountered the same productive sand, namely, the so-called 'Bolsa sand.' Whether this is so remains to lie proved. However, the general uniformity of dip obtained by correlating the first productive sand encountered in these wells would lead to the belief that the same sands have been encountered in these various wells. In the vicinity of the Huntington Central and I'antages wells, which are located approximately on the axis, it is probable that an upper productive sand has been found which does not exist -^own the dip. date of this report twelve wells are ])roducing and the total t.c.uv iu-oduction is 800(3 barrels, or a dailv vield of G()G barrels per welf. Signal Hill District. As stated above, the anticlinal sli-uctui-e of the Huntington Beach Held plunges sharply to the noil Invest, beyond 'Bolsa (Jhica' well Xo. 1. The general line of uplift, however, nuiy be followed to the northwest, it being marked by the low hills just east of Seal Beach, known as Landing Hill, and by other low rolling hills on the north -•ide of .Alaniitos Bay. From this point the structure apparently begins to emerge again till at Signal Hill, northeast of Long Beach, a well defined dome is apparent on the surface. The center of the dome is marked by the circular hill known as Los Cerritos, or Signal Hill. The formations exposed are gravels, sands and clays of the upper 'Since the date of this report a fair glrowing of oil has been encountered in this well below 4000 feet. 138 CALIFORNIA STATE MINING BUREAU. PETROLEUM RESOURCES OF CALIFORNIA. 139 l)eacli in a southeast diroction, so that it ])asses through well No. 1 of the llinitin. date of this rei)ort twelve wells are producing and the total ...iii\ jiu-oduction is 8000 barrels, or a daily yield of 6(36 barrels per well". Signal Hill District. As stated above, the anticlinal structure of the Huntington Beach Held plunges sharply to the northwest, beyond 'Bolsa Chiea' well Xo. 1. The general line of uplift, however, may be followed to the northwest, it being mai-ked by the low hills just east of Seal Beach, known as Landing Hill, and by other low rolling hills on the north side of .Alamitos Bay. PVom this point the structure apparently begins to emerge again till at Signal Hill, northeast of Long Beach, a well defined dome is apparent on the surface. The center of the dome is marked by the circular hill known as Los Cerritos, or Signal Hill. The formations exposed are gravels, sands and clays of the upper 'Since the date of this report a fair showing of oil has been encountered in this well below 4000 feet. 140 CALIFORNIA STATE MINING BUREAU. Fernando. The dip on the flanks vary from 10° to 25°, while the phinge to the nortliwest and soutlieast is about 15°. The general geological conditions here are extremely favorable for a highly pro- ductive field. At the date of this report three wells are drilling here. The Shell Company's well cemented off water at 2745 feet, and on drilling out the cement encountered fair showing of oil. On a>;count of the sharp dips the productive area will probably be limited to a circle of about a half mile in diameter arouml the center of the hill. Region from Signal Hill North to the Inglewood Hills. • NorthAvest from Signal Hill the structure again plunges sharply to the northwest, and the Fernando beds are overlaid by Quaternary sands. The general line of uplift, however, may be followed from Signal Hill northwest to Dominguez Hill, thence to Rosecrans, and thence through Athens on the Hill, and from there it continues north- west, passing about a mile east of Inglewood and running along the highest ridge of the Inglewood Hills. Along this entire distance it is marked by low rolling .hills, and the position of the axis may be barely determined by low dips of 2° and 3°. In the Inglewood Hills, however, the position of the axis is well marked and dips of 5° to 10° may be obtained. The fonnations exposed are loose sands and clays of Quaternary age. This region has been tested by approximately nine wells: The Union Oil Company, the Standard Oil Company, and the Highland Development Compam^ each drilling a well at Dominguez. At Rosecrans, the Eddystone Oil Corporation drilled the two ]\IacKey wells. At Athens on the Hill, the Union Oil Company drilled the 'Anderson well,' and in the Inglewood Hills the Standard Oil Company drilled two wells, and the Bartolo Oil Company drilled one well. These were all deep holes, those of the Standard Oil Com- pany being over 5000 feet, and in none of them were any favorable indications found. It is probable that the plunge of the structure has buried the possible oil sands which should occur at the base of the Fernando formation beneath an excessive thickness of upper Fernando and Quaternary sands and clays, so that they are beyond the reach of the drill in this area. Region from the Inglewood Hills to Beverly. From the Inglewood Hills the general line of uplift continues north- west, passing just east of Culver City. From this point on the struc- ture gradually emerges so that at a point about a mile west of Beverly the oil sands are again near enough the surface to be within reach of the drill. Tliis area is known as the Beverly Hills field. The wells are grouped about the axis of the anticline which has a northwest- southeast trend, and run approximately along the west line of the Amalgamated Oil Company's 'Rodeo' lease. The total proven area of this field is 110 acres. The total average daily production in Decem- ber, 1920, was 450 barrels of oil. The average number of wells produc- ing was 15, with an average daily .yield, per well, of 30 barrels of oil and 25 of water. PETROLEUM RESOURCES OF CALIFORNIA. 141 Region of the San Pedro Hills. Tills n'i>;ion consists of tlio lulls that lie west and northwest of San Pedro. The formations exposed here consist of diatomaeeous shale and sandstone beds of the Puente formation (Monterey Series). Along the eastern and northern edijes the Puente is ovtM-laid by a small area of loose sands and gravels belonging to the San Pedro formation (Quaternary). The structure consists of a main anticlinal fold, with a northwest-southeast trend, the axis of which runs just east of the high center ridge of the hills and finally plunges to the south out to the sea at Point Fermiu. Along this axis are several seeps of heavy tar, and at Point Fermiu, where the plunge of the fold has caused the lower Puente shale to be overlayed by the upper sandstone beds, seep- ages of heavy oil are found at the contact. Shallow wells drilled here have encountered small showings of tar. On both sides of the main anticline there are several minor folds. One of these strikes out into the valley in a northeast direction, halfway between San Pedro and Redondo. Two wells have been drilled on this fold, located on the Weston Ranch. One, the Harbor Crude Oil Company's w'ell, was drilled to al)out 1200 feet and encountered small showings. The second well, drilled by the Traders Oil Company, reached a depth of nearly 4000 feet. To a depth of 1800 feet, loose sands and gravels of the San Pedro formations were encountered, and small showings of heav}' tar were found. Below 1800 feet the well has been drilled in 'brown shale' (Puente diatomaeeous shale) and occasional small showings of oil have been noted. These . two wells were favorably located, and their failure to obtain anything more than a showing would indicate that this region is not favoral)le for the accumulation of any apprecial)le amounts of petroleum. This is probably due to the lack of reservoir beds above the Puente shale. Region Lying Between San Pedro and Santa Monica. This territory consists of flat lowlands with some low sand hills along the coast from Playa del Rey to Redondo. There are no surface indications which give any hint as to the underlying formations or structure. This region, however, in common Avith the other flat areas of the coastal plain, has the possibility of containing buried productive anticlines. It has been thought that the low sand hills may possibly be a topographic expression of such a structure, and at the date of this report approximately 7 wells are drilling in the region east of El Seguudo to test this theory out. Two of these wells, the Milwaukee Fountain Trust Company's well No. 1 and the Standard Oil Company's well No. 1 on Sec. 8, T. 3 S., R. 14 W., encountered considerable gas at about 1600 feet. There is no evidence to date to show whether or not this gas is connected with any petroleum deposit. No showings of oil have been found. The only manner in which the possibilities of this area can be told is by actual drilling. This entire region is worthy of being examined carefully for evidences of buried structure. In the preceding paragraph all the areas in the coastal plain district in which there is the slightest indication of oil, or favorable structure, have been described. There yet remains to classify the areas in this 142 CALIFORNIA STATE MINING BUREAU. district in which there is no direct o:eoh)gical evidence available to indi- cate -whether or not they contain possible productive fields. These areas consist of the flat regions lying between the three general lines of structure above described. In general, they consist of the territory- south and west from Los Angeles to Long Beach and Santa ^Monica, and southeast from Los Angeles to Anaheim and Santa Ana. The oil possibilities of these areas may ])e summed up by stating that they may contain buried anticlinal folds which may be productive. There is no direct evidence as to where, or whether, these folds actually exist but these areas are worthy of being carefully examined for such a possil)ility and have consequently been colored in blue on Plate I. San Gabriel Valley. This region may be considered as the territory lying north of the La ]\Ierced and Puente hills and south of the San Gabriel ^Mountains. The Puente sandstone and shale, and the Fernando sands and shales, which outcrop along the north flank of the Puente and La Merced hills, dip to the north and probably underlay the greater portion of the San Gabriel Valley, resting on the granite rocks of the San Gabriel Range, along the northern edge of the valley. The Fernando is principally confined to the northern slopes of the Puente and La ]\Ierced hills, and is found only in patches in the valley proper. In the San Jose Hills, which lie between Puente and Pomona, the diato- maceous shale of the Puente formations is domed up in an anticline, and along the nortliern edge the Puente is overlaid by a small area of Fernando. At the western end. just west of Pomona, outcrops of crystalline rocks are found, and similar outcroi)s are found in the north end of the Puente Hills, just south of Pomona. On the axis of the anticline, in the San Jose Hills, two wells have been drilled, one l)y the Santa Fe, and one by the Shell Company, both wells l)eing drilled to a depth of over 3000 feet in the Puente and failing to find any favorable indications. Along the eastern slope of the Puente Hills in the vicinity of Chino it is possible that small showings of oil will be encountered by wells drilled here (see Chapter XII, San Bernardino County, for a further description of this region), and similar results can probably be obtained by wells drilled along the north flank of the Puente Hills north of the Whittier. Brea Canyon and Olinda fields, l)ut it is extremely doulitful whether commercially productive wells ever will be encountered in the San Gabriel Valley, or along the northern and eastern flanks of the Puente Hills. This is due to the unfavorable structure and the lack of reservoir beds above the Puente shale. Eastern Portion of Orange County. This region will be considered in this report as that portion of the county lying east of the Santa Ana River and Newport Bay. The oil possi])ilities may be summed up by stating that tlie region is not a favorable one for the accuuudation of peti-oleum. The geology of the region is as follows: The main portion of the Santa Ana ^Mountains is composed of ancient cry.stalline rocks, mostly slates of Jurassic age; along the western and southern flanks, rocks of Chico age are exposed, PETROLEUM RESOURCES OF CALIFORNIA. 143 which, in turn, arc overlaid liy small patches of Kocciic. This condi- tion exists in the vicinity of the Oranjrc County Tai'k, where two wells are drillin;^, iu heds of Eocene age. Along the east hank of the Santa Ana Kiver, from Olive to Corona, the MontiM-ey Series and the Fernando formation, are exposed. These are foUled in an anticline which runs j)arallel to the river fi'om 'Horseshoe Bend' to Olive. This fold has heen tested by approx- imately nine wells, and oidy small showings of oil have been encoun- tered, so that it may be considered as unproductive. In the Lagnna Hills the formations exposed are mainly coar.se sand- stone of Eocene age. These are overlaid along the edges of the hills by beds of sandstone and shale of tlic Monterey Series. There are several minor anticlines in these hills, one of which is located at the edge of the hills south of Irvine and west of the Laguna road. The II. K. and T. Company has drilled a well on this fold to a depth of nearly 3000 feet without any encouraging results. In the flat area running from Tustin to El Toro the diatomaceous shale of the Montei-ey is present, occupying a synclinal trough between the Santa Ana ^lountains and the Laguna Hills. This condition con- tinues .southeast through the Capistrano district to the San Uiego County line. Section AB, Fig. 10, shows this general structure, and the formations exposed. Following is a l)rief description of these formations: The Cretaceous consists of al)out ^oOO feet of conglomerate sandstone and shale. The Eocene consists of the following beds : At the base about 1000 feet of shale characterized by dark red aiul |^uri)le clay beds, comi)rised of fine fragments derived from sei'pentine rocks, and similar to the 'Red Beds' of the Coalinga lield. Above this is found about 2000 feet of coarse white sandstone, and finally at the toj) of these is another sei'ies of shales about 1000 feet in tliiclvness. The base of the Miocene is characterized by an extremely coarse con- glomerate, made up of fragments of schist, and of a thickness of over 200 feet. Above this conglomerate is found about oOO feet of Vaqueros sandstone and IKK) feet of JMonterey shale, which occupy the trough of this .syncline. Just north of Capistrano there is a minor fold in the ^Monterey on which the Cnion Oil Comi)any has drilled a well to a depth of 4000 feet without any indications of petroleuuL The .statement made at the beginning of this section that the region is not favorable for the accumulation of oil is based on the following facts: The greater portion of this area is covei't'd l)y rocks that are older than the oil-bearing formations of Southern California, and which show no oil nor contain any beds that are capable of forming oil. The Monterey, which contains oil in other regions in Southern Cali- fornia, is found in this region only in a small thickness, and in an unfavorable structure, without reservoir beds for the oil to collect in. Lastly, to the best of the writer's knowledge, there are no surface indications of petroleum, such as seepages or gas blows, in the region lying east of Tustin. 144 CALIFORNIA STATE MINING BUREAU. •^ -S+W eUV •ei^KiSZ cry: uoAucD nag J^.\\:|;)\ .o> uoXuco osonqejx XailPA ouej+Sjdeo >)e3J0 09!iv ?-' eunbc"! 01 o d a a JS 'V a J3 C a "5 a J3 c3 a 3 be 03 O a o a a ^- o : it PETROLEUM RESOURCES OF CALIFORNIA. 145 CHAPTER XL Sax Diego and Imperial Counties. San Diego County. Topogi-apliically and ijeolofrii-'ally, San Diego may be divided into two areas, one a mountain higliland area covering approximately eleven- thirteenths of the county and the other a narrow belt of about fifteen miles ill widtli along the coast, cliaracterized b}' broad, flat-topped sea terraces. Tiie highland area is a i)art of a great fault block, which is character- ized by a steep descent to the Imperial County side and a gradual slope on the west to the terraces of the coastal plain. The formations of the highland region consist, for the most part, of granitic rocks, together witii smaller areas of lavas and ancient crystalline schists and lime- stones. As none of these are capable of containing oil, no further discus- sion will be given of the highland area.^ The coastal strip is made up of sedimentary rocks, ranging in age from the Chico (upper Cretaceous) to the recent beach terraces. This area may best be discussed by dividing it into two parts, consisting of the region north of Del ^lar and the region between Del Mar and the Mexican boundary. In the region north of Del j\Iar, the sedimentaries are lying against the crystalline rocks, in a gentle monocline dipping about 10° to the west. The following formations are exposed : Eocene, lower Miocene and recent terrace deposits. The Eocene is best exposed along Santa IMargarita Creek, between Ysidora and the Home Ranch. It consists of about 2500 feet of medium coarse white sandstone and above the sand is about 2000 feet of fine, tan-colored, muddy shales. North of Santa ^Margarita Creek the base of the Eocene is charac^terized by red and purple clay beds, known as the Red Beds and referred to in the description of the Eocene in the vicinity of Capistrano (Orange County). On account of the strike of the beds, which is approximately north and south, the upper shales disappear and run out to sea just south of Oceanside and from this point on south only the lower white sandstone beds are exposed, at times covered along the terraces by recent deposits. The entire Eocene Series is continuous north i-nto Orange County and connected with for- mations of the same character and age, described in the vicinity of Capis- trano. In the region at the head of San Mateo Creek, it is possible that the Eocene is underlaid by shales and conglomerates of Chico age, which in turn rest on the granite. The lower Miocene consists first of about 500 feet of coarse conglomerate made up of flat fragments of crystalline schist, prol)ably derived from rocks of the Franciscan formation. This conglomerate is a continuation of the conglomerate beds referred to in the descriptions of the eastern portion of Orange County. It is most prominent in the vicinity of San Onofre jNIountain, and disappears in its southward extension ])y striking out to sea at Oceanside. 'Certain areas of Tertiary sedimentary rocks found along the eastern border of the county, near Carrizo Creek and San Felipe Creek, will be discussed in connection with Imperial County. 10—13322 146 CALIFORNIA STATE MINING BUREAU. The Vaqueros sandstone and senii-diatoniaceous shale of the Monterey whicli overlies the conglomerate farther north in Orange County do not outcrop in San Diego County, but they are probably present beneath the sea terraces from the county line as far south as Santa ^largarita Creek. In Fig. 11, Sec. AB shows the general structure and character of the formations north of Santa Margarita Creek. Between Oceanside and Del Mar, the only sedimentary formation present is the white sandstone member of the Eocene, dipping at a low angle to the west. There is no evidence of petroleum anywhere in the area between the Orange County line and Del ^lar. The following wells have been drilled here : Clark Oil Company well east of La Costa, NW. J of Sec. 26, T. 12 S., E. 4 W., depth 2665, now 1)eing redrilled by the La Costa Oil Company. Pacific-Laguna Company well east of La Costa, SW. ] of Sec. 26, T. 12 S., R. 4 ^Y., depth 1400 feet. Both wells failed to show oil. At the present time the Oceanside Oil and Gas Company is drilling a well in the Eocene shales about a mile and a half nortlieast of the town of Oceanside, and has reached a depth of about 1600 feet. The La Costa Oil Company has taken over the old Clark well, which was abandoned some years ago, and redrilled to a depth of 2700 feet. Showings of oil and gas have been reported. In the area between Del iNIar and the IMexican boundary the general structure partakes of the nature of a very flat syncline, the axis of which parallels the coast about five miles inland. Beds of the following ages are found outcropping: Cretaceous, Eocene and Pliocene. The Cretaceous is represented by the Chico and consists of beds of medium grained sandstone, blue-gray in color and interbedded by thin layers of dark colored shales. It outcrops on the surface only at the southern end of Point Loma and in the sea cliff at La JoUa. It pro])ably underlies the entire area. The total thickness is not known, but well logs indicate that it is over 3000 feet. The Eocene is probably represented by beds of IMeganos age, and consists of clay shales and white sandstone, with a total thicknes.s of about 1000 feet. The outcrops are limited to Point Loma, the sea cliffs from La JoUa to Del ^lar, the vicinity of Soledad Mountain and at low levels in Soledad and Rose canyons. The Pliocene, known locally as the San Diego formation, overlies almost the entire area. It consists of beds of sandstone conglomerate and clay shales, with a total thickness of about 500 feet. In Fig. 11, Sec. CD shows the probable structure in the vicinity of La JoUa and San Diego. The following wells have been drilled in this area :^ La Tengo Oil Companv. Well one mile north of Tia Juana, in SW. i Sec. 31, T. 18 S., R. 1 W., depth 3290 feet, reported oil and gas ; drilled in 1911. Tia Juana Valley Oil Company. Well about two and one-half miles south of Nestor and a few hundred vard.s north of the ^Mexican border, See. 9, T. 19 S., R. 2 W., known as the Scott well. Depth 1474 feet ; drilled in 1910. The Community Oil Company has recently made an attempt to clean this Avell out. ^See Fourteenth Report of the State Mineralogist, pp. 70S-712. PETROLEUM RESOURCES OP CAIJPORNIA. 147 ^ 3>(V1 HONVa 3W0H avoa NaOH 3dV:3 , i-^Vl Al \J NONVO osnYl \!^\ \^\\ ^ ^s; S3b01iSVl ,fc l^ NONVO W^ ^ r^ AHdBnW \> M dWVO I 1 1 1 1 1 1 1 NONVO 3S0d avaanos i vnorvn . si o ^ 148 CALIFORNIA STATE MINING BUREAU. Otay Oil Coiiipaiiy. Si)iitlieast of Otay, NE. ] of Sw. 30, T. IS S., R. 1 W. Dc'i)tli 2185 fcH't; clrillcil in IDIO. Reported showing of oil and gas. Bal])oa Oil Comi)any. Well in tlie :\lission Valley. Piiehlo Lot 1105. Depth 5t)75 feet; drilled 1911. San Elijo Oil Company. Two wells just west of Sorrento Station; Pueblo Lot 27. Depths 1599 feet and 1303 feet. The Pnterbaugh well at ^loreno. about one and one-half miles north of Mission Valley. Depth 1200 feet. The Chula Vista well, drilled near the town of Chula Vista, reached a depth of 1812 feet. At the present time the followino; wells are drillinp-: Linda Vista Petroleum, See. 23, T. 15 S., R. 3 W. Community Oil Company has started the following wells: "Well No. 1 (old Scott well), Sec. 9, T. 19 S., R. 2 W. The company is endeavoring to clean this well out. Well No. 2, Sec. 4, T. 19 S., R. 2 W. AVell No. 3, T. 17 S., R. 2 AV., Lot 17. AVell No. 5, one mile east of Moreno, T 15 S., R. 3 W. The Tecalote Dome Oil Company. T. 16 S., R. 3 W., Pueblo Lot 1272. Depth, 2650 feet. Mission Valley Company, Sec. 24, T. 16 S., R. 3 W., Pueblo Lot 1108. While most of the wells which have been drilled or are drilling at the present time report showings of oil or gas, the significant fact is that no actual production of oil ha.s ever been obtained. The possibilities of obtaining oil in this area are not very favorable. There is apparently a total lack of any actual evidence of petroleum, such as seepages or gas blows. The formations exposed show neither favorable structure nor contain sufficient organic material to form anv noticeable quantities of petroleum. TTnless evidence is found to disprove these facts, further drilling in this area is a waste of money. Following is a portion of a report on the oil possibilities of San Diego County, from a press bulletin of the United States Geological Survey, ]\Iareh, 1920, based on an examination made by Mr. W. S. W. Kew : "The region was recently examined by William S. W. Kew. of the United States Geological Survey, Department of the Interior, who is of opinion that San Ui(>go County is not a favorable place in which to drill test wells for oil. Tlie reasons for this opinion can be summarized as follows: (1) The principal formations that furnish oil elsewhere in California are not found in San Diego County. (2) The Upper Cretaceous strata, which probably constitute a large part of the sedimentary beds at San Diego, are not commercially productive in other parts of California, and there is nothing to indicate that they will be productive in the southern part of tlie state. (3) The Eocene strata, though of the same age as the oil-bearing strata in other parts of California, do not appear to contain oil liere. As far as known, no structural features that are favorable to the aucumulation of oil, such as anticlines, have been discovered in San Diego County. As the strata dip very gently and at many places lie nearly flat, careful geologic work would be necessary to locate these structural features. If drilling is continued near San Diego, the structure should be carefully studied in order to determine the most advantageous places for sinking wells to test the oil sands that are reported to have been penetrated in previous tests.." Imperial County. Imperial County occupies the desert region in the extreme southea.stern portion of the state. Its length east and west is approximately 100 miles and its width north and south is about 55 miles. About one-half the county is a great flat plain, know'ii as the Imperial Valley, the major portion of which is below sea level. This great, flat valley represents the old sea bed of the mo.st northerly extension of the Gulf of California, PETROLEUM RESOURCES OF CALIFORNIA. 149 and has been separatod from tho pi-esent gulf by a barrun- of sediiiionts built up by the (\)b)rado Kiver. The waters of the gulf in this isolated l)ortioii gradually evaporated, leaving the l)asiu of Saltou Sink. In 1904, the Colorado River broke through its western l)ank and partly retilled Salton Sea. A little water is still running into it by way of the New River. At the ])resent time the total area oeeupied by the sea Is about -70 s<|uare miles, of whieh 280 square miles lie within the county, oceupying the northeast corner. The surface of the water is about 250 feet below sea level and the depth is about 37 feet. On two sides the Imperial Valley is surrounded by mountain ranges. On the west the highland area of western San Diego County (Peninsula Range) rises abruptly from the valley tloor along a line marked approxi- matelv bv the boundarv between the two counties. Superstition ^Nloun- tain is a detached range lying out in the valley northwest of the town of Imperial. On the east, forming the northeastern one-half of the county, are sev- eral mountain ranges, chief of which are the Chocolate ^Mountains. This portion of the county may be considered as having no oil possibilities. The fornuitions which are exposed consist mainly of ancient nietaniorphic rocks, probably of pre-Caml3rian age. In various localities these meta- morphics are covered by lava tiows of a much younger period. Along the west slope of the Chocolate ^Mountains are outcrops of vivid colored sands, clays and gravels, i)robably of Pliocene age. The character of the formations and the total lack of any evidence of petroleum make this region unfavorable. That portion of the county which is underlaid mainly by Tertiary sedimentary rocks, and C(uitains the only areas worth investigating, lies west of the main line of the Southern Pacific Railroad, and consists of approximately a little more than one-half the county (Plate No. VI shows this area). AVith the exception of a strip about ten miles wide along tliQ. western border, and the areas around Superstition Mountain and Yuba Buttes, this district is covered entirely by recent deposits of fine silt and sand. The geology of it will therefore have to be determined by studying the formations exposed in the localities mentioned above. The strip along the western border, which contains the exposures of tlie underlying formatioiLS, is formed by spurs of the Peninsula Range jutting out into the valley. The principal spurs are Coyote IMountain and Fish Creek IMountain. North of San Felipe Creek there is a series of low, rolling hills, which nuiy be considered as the southeastward extension of the Santa Rosa ^lountain, and which contain excellent exposures cf the sedimentary formations. Superstition Mountain, l.ying mainly in Townships 18 and 14 S. and Range 11 E., has a core of crystalline rocks and the Tertiary sedimentaries are exposed in the low, rolling hills to the northeast. Yuha Buttes consists of a few low mounds in Sees. 28 and 33, T. 16 S., R. 11 E., which are formed by an uplift in sedimentary strata. The oldest rocks in this district consist mainly of marbles and schists, into which have been intruded masses of granitic rocks and pegmatite dikes. The age of this complex crystalline series is not deHnitcly known, but Fairbanks^ believes it to be of Carboniferous age. It is a part of 'Eleventh Annual Report of the State Mineralogist, 11. W. Fairbanks, p. 90, 1893. 150 CALIFORNIA STATE MINING BUREAU. the crystalline series that form the highland area of San Diego County, and is coninionly referred to as the basement complex. AVithin this area it is found outcropping along the north slope of Fish Creek Moan- tain, along the central core of Coj^ote and Superstition mountains, and finally in the group of mountains between Coyote Wells and the Mexican border. The next oldest formation is a highly colored Andesitic lava flow, approximately 200 feet in thickness. It lies unconformable upon the eroded surface of the basal complex and is best exposed running east and west along the central ridge of Fish Creek Mountain and in small patches on the eastern slope of Coyote IMountain. The age i>s probably middle Tertiary. Ljdng with marked unconformity upon the lava and basement com- plex is a series of sedimentary rocks, first described by Kew^ and called by him the Carrizo formation. The basal beds of this formation consist of medium-coarse gray sandstone, together with beds of coarse conglom- erate. The sandstone is characterized by numerous fossils and coral reefs. Above this sandstone member are found beds of fine sandy shales, silts and clay shales. The fine clay shales are usually of a chocolate color and bear at first sight a resemblance to certain varieties of diato- maceous shale. However, an examination under the microscope shows no diatoms and the beds apparently are lacking in any appreciable amount of organic matter. The upper shale beds are characterized by fossil reefs made up of the remains of oysters and pectens. The age of the Carrizo formation is probably upper Miocene to lower Pliocene, and the thickness between 3000 and 4000 feet. The formation is exposed in the following places: at Yuha Buttes, at Coyote Mountain, along the south slope of Fish Creek Mountain, in the low hills north and east of Superstition Mountain, in the low hills north of San Felipe Creek, and continuing north to the Riverside l)oundary. This latter area also continues westward into San Diego County as far as Clark Lake. Considerable movement has taken place in the valley, and the Carrizo beds have been sharply folded into numerous structures. The principal areas are as follows: Yuha Buttes is a domed anticline. A plunging anticline apparently strikes out of the east slope of Coyote ]\Iountain. There are numerous folds to the east and north of Superstition Moun- tain. Carrizo Creek marks the axis of a syncline running east and west. In the area north of San Felipe Creek, the major fold runs southeast along the south line of T. 11 S., Es. 9 and 10 E., and at least two minor folds diverge from this structure and strike to the northeast. Seepages of oil and the presence of asphaltum have been frequently reported as being found in the Imperial Valley, and the majority of wells now drilling in the valley have reported showings of oil and gas. However, none of these reputed seepages or showings of oil have ever been verified by any representatives of the State IMining Bureau. The possilnlities of finding oil in the valley may be summed up as follows : while the structure of the Carrizo beds is extremely favorable for its accumulation, there is apparently no formation present that ^Univer.sity of California. Riill. 5, Vol. S. 191 1. Tertiary Echinoids of the Carrizo Creek Region in the Colorado Desert. By W. S. W. Kew. PETROLEUM RESOURCES OF CALIFORNIA. 151 could form potroloum. From tho above description of the rocks exposed, it is evident that tlie only beds that could possibly contain oil are those of the Carrizo formation and it is equally evident that this formation does not contain sufficient organic matter to form any noticeable amount of petroleum. It should also be noted that the Carrizo beds are sharply folded and tilted, and if any oil were present it would show as seepages along the outcrops. The only possibility of finding oil lies in the bare chance that somewhere in the valley there are beds of organic shale, the outcrops of which are hidden by the overlapping of the Carrizo beds against the crystalline rocks. If such beds existed, and there is no direct evidence that they do, oil would tend to collect in the anticlinal structure of the Carrizo formation. The wells now drilling, a list of which is given below, are nearly all favorably located and should conclusively prove or disprove the presence of oil in the county. Recent reports have been made on the county by Mr. W. S. "W. Kew^ and I\Ir. Irving Augur.- Following is a portion of Kew 's report : "The Carrizo Creek beds have been foMed into numerous arches (anticlines) and troughs (synclines). One of the larger anticlines that seems favorable to the accumu- lation of oil lies north of San Felipe Creek. Others are on the north, east and south sides of Superstition Mountain, the core of which is granite. The southeastern exten- sion of this mountain is an finticline, which extends from the granite in the southeast corner of T. 14 S.. R. 11 E., across the southwest corner of T. 14 S., R. 12 E., into T. 1.5 S.. R. 12 E. The beds along the anticline in this area dip rather steeply away from its axis, which plunges gently to the southeast. Anticlines also occur north and northeast of the eranite center of Superstition Mountain. "The strata in the hills between San Felipe Creek and the Salton Sea have beeen considerably folded, though southeast of Seventeen Palms there appears to be only one major anticline or dome upon wliich subsidiary folds are superposed. This main anticline trends southeastward across the soxitheastern part of T. 11 S.. R. 9 E., and the southwestern cart of T. 11 S., R. 10 E.. and extends into T. 12 S., R. 10 B. The highest point on this anticline— tlie apex from which it plunges to the northwest and southeast — is near the line between Sees. 2.5 and 36. T. 11 S., R. 9 E., and the angle of plunge is about 10° to 20°, becoming less steep with increase of distance from the apex. The beds dip from the axis of the anticline at an average general rate of 15° to 30°. but tliose that form the subsidiary folds attain at some places a dip as high as 55°. "In general, the top of the anticline is fairly flat, though it is broken into minor folds. The well of the Imperial Valley Oil and Development Association is on the east side of the higliest point or apex and the Diamond Bar well is on the west side; both wells are only a short distance noi-tli of the axis of the anticline. This anticline is probably one of the most promising in Imperial Valley, and the test wells are properly located to prove tlie presence or absence of oil there. ".Seepages and oil sands in Imperial Valley have frequently been reported, but none of these reports have been authenticated, and samples of so-called oil sands have always proved to be sands blackened by manganese oxide, but it is reliably reported that asnhalt occurs on the southeast edge of a dry lake west of Signal Mountain. aViout 3 miles south of the Mexican border. Several wells drilled for oil in the valley have not yielded favorable results. In 1902 two wells were sunk at Yuha Buttes, in Sec. 32, T. 16 S., R. ir E., on a domelike uplift in the Carrizo Creek beds. One of these wells was sunk 1300 feet without getting any indication of oil except a little gas. The Harper well, also known as the Me.squite drill hole, in the northeast corner of Sec. 34, T. 12 S., R. 10 E., is reported to have gone 700 feet and to have struck a little gas. It now yields water. The Hanna well, on the north side of Fish Creek Mountain, is said to be SOO feet deep. The Hudson well, in the southwestern part of T. 14 S.. R. 11 E., is about 500 feet deep. The result of what is known as the Barrett drill hole, sunk near the mouth of Carrizo Canyon, is not known. "The geology structure in Imperial Valley is exceptionally favorable to the accumu- lation of oil, and if any of the beds of the Carrizo Creek formation contain oil it should be found in some of the anticlines that are now being tested. These beds show no surface indications of oil, but in some of the wells they have yielded a little gas. As these beds crop out in great thickness, and thev are faulted at many places, they sho uld show seepages, or oil-impregnated sands, if they contain oil. The JU. S. Geological Survey. Press Bull., June, 1920. Oil Prospects of the Imperial ^ alley. By Mr. W. S. W. Kcw. •.n.iT^"^^''"'''^ State Mining Bureau. Summary of Oil Field Operations for April, 1920. Resume of all Well Operations in the Imperial Valley. By Irving Augur. 152 CALIFORNIA STATE MINING BUREAU. absence of such seepages is the strongest evidence against the presence of oil in the Imperial Valley, but it is not conclusive. In Mr. Kew's opinion, Imperial Valley should be tested for oil. but the tests should be made only by persons or companies who can afford to invest large sums of money with poor chances of success." Following is a list of the welLs now drilling (see Plate VI) : In Sec. 9, T. 16 S., R. 10 E., the San Diego and Imperial Valley Oil Company has a well down to a depth of al)oiit 1100 feet. The hole known as the 'James well' is loeated on the south side of a plunging anticline in the Carrizo formation. In Sec. 6, T. 16 S., R. 11 E., the Southwestern Pipe Line and Petroleum Company has a well down to a depth of about 700 feet. This well is located in the flat lands of the valley and apparently no structure is present. In the area just north of the well the writer noted several out- crops of coarse sandstone dipping about 40° to the east. This exposure, however, was too meager to determine whetlier any structure was actually present. The log of the well indicates that the beds penetrated belong to the upper portion of the Carrizo formation. In Sec. 11, T. 16 S.. R. 14 E., near Holtville, the 104 Oil and Drilling Companv has a well dritliiig. In Sec. 32, T. 11 S.. R. 10 E., the Imperial Valley Oil and Development Company has a well known as the Brawley well, which is located on a dome in the Carrizo formation. A depth of 2570 feet has been reached. In Sec. 25, T. 11 S., R. 9 E., L. Lechtenberger is drilling a well known as the Diamond Bar well, which is located on a dome in the Carrizo for- mation. A depth of 3083 feet has been reached. PETROLEUM RESOURCES OF CALIFORNIA. 153 chapt?:r XII. The Desert Region. (Includes the counties of Riverside, S;in lU^rnardino, Nortlieastern Los Angeles, Eastern Kern and Itno and INlono.) This region, for the purpose of this r('i)ort. will be regarded as lying east of the Sierra Nevada, Tehaeliapi ^lountains, Sierra Liebre Range, San Gabriel Range, and east of and including the San Bernardino Mountain.s and Peninsula Range. This groui) of mountnins, running approximately north and south, with a slight we.stward l)end in the Ante- lope Valley region of Los Angeles County, effectually shuts oft' the desert area from the southern coastal i)lain and the central valley of California. As the area will be discussed by counties, the fertile western portions of Riv(>rside and San Hernardino counties, lying west of the mountain and properly lielonging to the coastal area, are discussed partly here and partly in Chapter X. Imperial County, which is a jiortion of this area, has, on acconnt of slightly dift'erent geological formations and recent attempts at develop- ment, i)een included in a separate chapter (XI) with San Diego County. Wliile this region is commonly know-n as the dese-rt area, it is far from being a land of broad desert plains, as possi])ly one-half of the territory is occupied by higli mount;) in chains, which rise with striking abruptness from the desert floor. In Mono and Inyo counties these mountain chains form a series of paraHel ranges, with a north and south trend. The central region is occupied by what is known as the IMojave Desert, the western part of which is known as the Antelope Valley. The south- eastern portion is known as the Colorado Desert and the southwestern (piarter is occupied by the San Bernardino and Peninsula ranges. The general geology and oil possibilities of this region may be sununed up as follows (exclucling the small portion of Riverside and San Bernar- dino counties wdiich lies west of the mountains ;ind belongs to the coastal area) : The greater part of the tint desert floor is covered by recent sand deposits. Along the lower foothills of tlie mountain ranges, particularly in the western and northern portions, there are small areas of Tertiary sedimentary rocks, interbedded with lava flows. These sediments, for the most part, represent either lake or land deposits. The higher i-anges of the southern region are composed of crystalline rocks, either granites or pre-Cambrian metamorphics. The high ranges of the northern region are also crystalline in character, being either composed of granites or highly metnmorphosed sediments of Paleozoic and Mesozoic age. With two exceptions which will be noted below, there are no know'n deposits of sedimentary rocks which may correspond to the oil-bearing formations of California. It is evident from a study of this region that it had a totally different geological history from the oil fields. The various Tertiary seas in which the oil-bearing formations were deposited appar- ently ciid not cover any appreciable portion of this area. The two 154 CALIFORNIA STATE MINING BUREi^U. exceptions mentioned above consist of beds of Eocene age, and the only thing they liave in common with tlie oil-field formations is that they were laid down in the same sea and consequently are of the same age as certain Eocene beds which are oil bearing in other portions of the state. One area of Eocene is fonnd along the western border of the ]\Iojave Desert, near Rock ("reek. Los Ang.'les County, and consists, according to Dicker.son,^ of about 5000 feet of coarse sandstone and shale, belonging to the Martinez formation. This area probably represents the eastward line of the ^Martinez Sea. The second area of Eocene is fonnd in the Elsinore Valley and consists of small thicknesses of highh^ colored shales and sands of Tejon age. Neither of these deposits show the slightest indication of petroleum. The rocks that are present, consisting mainly of granites, highly metamorphosed Paleozoic and Mesozoic sediments, Tertiary sediments of land or lake origin, together with lava flows, are all unsuitable for the formation of any appreciable amount of petroleum. To the best of the writer's knowledge there are no known authentic seepages of oil in this area. Two rather doubtful cases may be cited, however. On an island in'lMono Lake there is a hot mineral spring from which it is reported that oil seeps, and the writer has been furnished with a bottle of the oil. The formation in the vicinity of the lake and on the island is composed in part of fresh- water diatomaceous shale, about 100 feet in thickness. This shale has been intruded by an igneous dike and it is conceivable that this intrusion ma}' have caused destructive distilla- tion of the fresh-water shale, with the result that an insignificant amount of oil was formed. The second case consists of a sample which was brought to the Bureau by a prospector from 'somewhere near the Inyo-^Iono county line.' This sample turned out to be a piece of Gil- sonite, or mineral tar. Deposits of this tar have been reported as occurring in Nevada. Innumerable seepages and indications of oil have been reported from this area and a certain well in the ^lojave Desert has been reporting oil for the last eighteen years, but it may be noted here that in no case have these reports been verified. From the above brief description of the geology it is evident that the possibility of obtaining oil in the desei't region is extremely small. Following is a brief description of the particular geology and at- tempts at development in each county : Mono County. J\Iono County lies at the extreme northern end of this area. The for- mations exposed are mainl}' granitic rocks and lava flows. In the moun- tains west of IMono Lake and in the southeastern portion of the county, reddish gray limestones and beds of sandy shale of Cambrian age have been reported. In the vie-inity of Coleville, Bridgeport and on the east side of Mono Lake, there are fresh-water sedimentary deposits, probably representing old lake beds. At IMono Lake they contain a bed of fresh- water diatomaceous .shale, from which seepages of oil have been reported, a possible explanation of which has been given in the preceding para- graphs. Following is a portion of IMcLaughlin and Waring 's report on this area :- 'University of California. BuH. Dtpartnicnt of Geology, Vol. 8, No. 14. The Mar- tinez, Eocene and Assoiiatetl Formations at Rock Creek. By R. E. Dickerson, 1914. =California State Mining Bureau. Bull. 69. Fetroleum Industry of California. By R. F. McLaughlin and C. A. "Waring, 1914. PETKOLEUM RESOURCES OF CALIFORNIA. 155 "Mono County "Attempts have lippn made to develop oil near Mono Lake and a brief statement, based upon examinations by the autlior, of the very scant possibilities, may be useful. Surrounding tlie lake are sedimentary deposits containing marl, clay and diatoms, volcanic ash and gravel. Israel C. Russell reports' a measured thickness of 200 feet, and states that tlie total must be very much greater. This deposit was laid down during Quaternary time when the lake was much larger tlian at present. There are no other unaltered sediments known. The lake deposits rest upon granite, meta- morphics and glacial drift and are intruded or overflowed by recent basic igneous rocks. "The only reported indications of oil is a spring near the eastern shore of Paoha Island. Russell mentions this spring and the fact that it had an odor of petroleum. However, he gives the temperature of the water and its analysis, but makes no further mention of the presence of oil. Several experienced oil men have stated that they collected oil on the surface of the water. "During 1908 there were two wells drilled. One, near Dechambau's Ranch on the northern shore of the lake, is about 900 feet deep, and hot water flows over the casing. The other well, near the southwestern shore of Paoha Island, was drilled to 2010 feet, all in blue shale except between 1700 and 1800 feet, where pink sand gave a strong flow of hot water which rose over the casing. "There is no reason to suppose that other drilling would be successful." A detailed geological descrii)tion of the county can be found in the Eighth Annual Report of the ITnited States Geological Survey, Part I, pp^. 2()l-394, by Israel C. Russell. Inyo County. The format ion.s of Inyo County may l)e divided roughly into three classes. The first consists of beds of highly altered sediments, mainly liiiK^stones and slates, vaiying in age from the Cambrian to the Triassic. They are found in the mountain ranges east of the Owens River Valley. The .second consists of great ma.sses of granite, which have been intruded into the altered sediments. The third consists of Tertiary lava flows, lying unconformably upon the first two. AH have been highly crushed and folded. The only area of unaltered sediments is a small thickn&ss of Tertiary beds along the west fiaiik of the Funeral ]\Iouiitains, near Furnace Creek. These beds, with a maximum thickne.s.s of about 500 feet, consist of tuffaceons .sandstone, conglnmerates and clays. H;ill- has correlated them with the Siebert lake liods of ^Miocene age. No evidence of petroleum has ])een reported from this fonnatiun. A detailed geological map and report of the county has been made by AVaring and Iluguenin."- Eastern Kern County. This includes the desert region of Kern County, which lies east of the Tehachapi jMountains and forms the northwestern portion of the Mo.jave Desert and the Antelope Valley. The formations exposed con.sist mainly of much altered schi.st, gneisses, marbles and slates, probably of Paleozoic age, together with smaller areas of granite. Overlying these ancient rocks is a series of beds of Tertiary age, to which the general name of the Rosamond Series has been applied by Iler.shey.* These beds are found at wide intervals over practically all the Mojave Desert region. They consist of beds of sandstone derived from granitic 'U. S. Geol. Survey. Eighth Annual Report. Part T, pp. 261-394. =U. S. Geological Survey. Bull. 308. Geologic Reconnaissance in Southwestern Nevada and Eastern California. Ry Sidney H. Ball, 1907. 'California State Mining Bureau. Geological Map of Inyo County. By C. A. Waring. 1917. Mines and Mineral Resources of Inyo County, 1915-1916. By C. A. Waring and E. Iluguenin. Also in Report XV, pp. 29-134. ^Hershey, O. H. Some Tertiary Formations of Southern California. Am. Geologist. Vol. 29, pp. 365-370, 1903. 156 CALIFORNIA .-STATE MINING BUREAU. debris, together with beds of rhyolitic tuff, eoarse breccias of lava and granite and some iniuhly clay shales. Their niaxiimiiu thickness is about 3000 feet and the age is upper ^lioeeiie. They contain no evidence of petroleum. Within the area under discussion they are found, just north of Kosamond Station, and in the El Paso Range, near Rieardo post otfice. It is also possible tliat they ontero]) in the hills north of Neenach, in the Antelope \'allev. In See. 27, T. 9 N., R. 17 W., S. B. B. and :M., about six miles northwest of the ridge route of the state highway, there is a well being drilled by Robert AVatcborn. A depth of 4100 feet has been reached, at which point a large tlow of hot mineral water was encountered. The well is located just south of an area of crystalline rocks and the material around the rig consists of granitic debris. It is possible that the well was drilled for a portion of the way in the Rosamond Series. Northeastern Los Angeles County. This comprises that portion of Los Angel(\s County lying north of and inchuling the north Hank of the Sierra Liebre and San Gabriel ranges. The level portion of this area is known as the Antelope Valley and is covered by recent desert deposits. Along the eastern line of the county there are outcrops of crystalline rocks. The north flank of the San Gabriel and Sierra Liebre ranges are composed mainly of granite, with smaller areas of metamorphic rocks. At various places along the southern edge of the Antelope Vallej' there are small patches of unaltered Tertiary deposits. These consist of coarse sandstone conglomerates and clays, partly old lake beds and partly landlaid deposits. The age is mainly IMiocene. The only marine deposit recognized consists of the area of ]\Iartinez Eocene, reported by Uickerson at Rock Creek and referred to at the beginning of the chapter. It is possible that beneath tlie recent desert sands there are present beds of the Rosamond Series. Nowhere in the district is there any evidence of petroleum. San Bernardino County. Practicalh' nine-tenths of the county lies north of the San Bernardino ]\rountains and forms the greater portion of what is known as the Mojave Desert region. The flat desert spaces of this region are covered with recent desert deposits. The mountain ranges are composed of crystalline and highly altered metamorphic rocks. These consist of granitic rocks, areas of metamorphosed sediments of pre-Cambrian and Paleozoic age, together with lava flows, mainly of Tertiary age. There are also in various basins, beds of coarse sand, conglomerates and clays, representing lake and landlaid deposits of Tertiary and Quaternary age. In the region around Barstow and Daggett, extensive areas of the Rosamond Series (upper Pliocene) have been recognized. The Rosamond beds are here composed of lava flows, fine-grained tuff, volcanic ash, beds of green clay, conglomerate, impure limestone, and coarse sand- stone, none of which are ca{)able of forming any amount of petroleum. Nevei'tlu'U'ss, a superficial I'cscmblance of certain of the clay beds to some of the oil field formations has caused periodic "oil booms' in this region for the last eighteen years. Seepages and oil showing in wells PETROLEUM RESOURCES OF CALIFORNIA. 157 (Irilk'd here liave been reported but never veritieil. Tlie area has been examined by the rnited States Geobt'Jrii-al Survey^ for oil and has been condemned. Following is Pack's eonelusion of the region: "CONCLUSIONS AS TO THE PRESENCE OF PETROLEUM. "The writer believes that the northern part of the Mojave Desert between Barstow and the town of Mojave offers practically no promise of becoming a productive oil field, and that further drillinK will prove but a waste of money. The principal reasons for believing that this land will not prove productive are (1) the lack of strata from which it would seem reasonable to believe that oil might have been formed, especially the lack of thick masses of organic material (diatomaceous and foraminiferal shale), such as those which occur in or near all the oil fields in the southern half of California, and in which the oil is believed to have originated; (2) the lack of structural features favorable for the correction of petroleum, even if it existed, disseminated tlirough the strata. "Tile pre-Tertiary rocks can not reasonably be regarded as a source of petroleum. Only a small portion of these rocks are of sedimentary origin, and they are so metamorpliosed that ev<>n had oil once existed in them it is hardly conceivable that they should still contain it. The granitic rocks in the complex are, if possible, an even less likely source of petroleum, as their texture is so dense that they would offer practically no reservoir in which oil might collect if it existed in the near-by rocks. Oil has been found in rocks lithologically similar to some of the pre-Tertiary rocks of the Mojave Desert at only a single locality in California. This occurrence, at Placerita Canyon, about 20 miles north of Los Angeles, has been described by Eldridge=. The oil, at this place, occurs in fractui-ed schists which rest upon the granite of the San Gabriel Mountains. The most logical explanation for the presence of the oil here is that it has migrated from early Tertiary organic shales which may have at one time rested upon the metamorphic rocks, and which may now occur in the vicinity beneath the unconformably overlying late Tertiary beds. In the Santa Clara River Valley, a few miles west of Placerita Canyon, the early Tertiary strata and the beds in contact with them are filled wMth oil. As organic materials similar to those in the Santa Clara Valley are unknown in the Barstow-Kramer region, it can not be expected that a similar accumulation of oil will be found in the metamorphic rocks in this region. "The lecent coarse gravel, sand and clay which form the filling in the topographic basins and which, in places, extend as a veneer over the lower hills, are equally as unlikely a source of petroleum as the pre-Tertiary complex. They are composed almost or quite complete of fragments derived from the older rocks in this or in adjacent resions. and it is not reasonable to believe that these masses of rock fragments would be more likely to produce petroleum than the same rocks in place. The Tertiary volcanic rocks are likewise not to be considered as a source of petroleum for much the same reasons as apply to the granitic rocks in the pre-Tertiary complex. "It remains then but to consider the Tertiary sedimentary rocks. The coarse- gi-ained Tertiary beds are formed of fragments of various types of granitic, volcanic, and metamorphic rocks and are evidently no more probable a source of petroleum than pre the recent beds of sand and gravel. On the other hand, to casual observa- tion, the fine-grained Tertiary rocks of the Barstow-Kramer region appear to be similar to the Tertiary rocks in many of the oil fields of this state, and it is not so very surprising that in this region they have been regarded as a possible source of oil. A careful examination of them shows, however, th.at they are really very different from the Tertiary shales in the productive oil fields, and in place of being composed very largely of the remains of organisms they are formed almost wholly either of fine volcanic ash or of detrital material derived from rocks of v.arious types. They thus resemble the coarse-grained beds in the same region, differing from those beds mainly in the size of the particles they contain, and are not to be compared with the masses of organic material in the large productive oil fields of California. The only indications of organic matter seen in these beds were small particles of carbonized terrestrial vegetation scattered through some of the clayey and finer sandy beds, but the total amount of organic matter is entirely too small to be considered as a possible source of more than the merest traces of oil. "It is, of course, possible that in the broad, level desert areas, rocks of diffe'-ent types from any exposed in the hills may lie buried beneath the desert gravel. It is also possible that .=uch rocks, if they occur, are like those in the Tertiarv formations in the San Joaquin Valley on the opposite side of the Tehachapi Mountains. There is, however, nothing in the geology of this region, or, so far as known. In that of the desert as a whole, to support such a hypothesis. "No surface indication of petroUum was seen anywhere in the region. It is commonly rumored that a seep occurs in the Tertiary rocks northwest of Black Mountain, but a careful search failed to reveal it nor did persistent questioning discover anyone who could describe its location. The structure of the Tertiary rocks ^U. S. Geol. Survey. Bull. 541. Reconnaissance of the Barstow-Kramer Region By R. W. Pack. 1914. ■ " =Eldridge, G. H., and Arnold. Ralnii. The Santa Clara Valley, Puente Hills and Los Angeles Oil Districts, Southern California. U. S. Geol. Survey. Bull. 309. Pp. 100- 101, 1907. 158 CALIFORNIA STATE MINING BUREAU. is complex. In many places they are tilted to high angles and iiitiieatoly faulted, and if oil oceiiis in them it is surprising that it does not, at some place, show at the surface. "Even if oil was oiigiiially disti-ibiited in minute quantities through the rocks, the structure is not such tliat it would have tended to collect or trat) the oil. Irregular and faulted folds occur in at least three places northwest of Barstow — the Barstow syncline in T. 11 N., R. 2 W.. a small anticline just noith of the Glroux well in T. 32 S., R. 44 B.. and an irregular fold or folds in T. 31 S., R. 44 B. It is generally reported that a well-marked anticline passes through the hills north of Barstow. Indeed, it is believed by some that such a fold extends along the north side of the desert from Tehachapi Pass nearly to Barstow. This idea is erroneous, for the only fi>lds here are small, discontinuous and much faulted. Faults, not folds, dominate the structure. Thus the structure is much more favorable for the escape of any oil that might possibly have been found here than it is for its concentration in appreciable quantities." Four wells have l)een drilled here. The Kramer Consolidated Oil Company's well in the NW] of See. 11, T. 10 N., R. 5 W., is located ahoiit three miles north of ITawes Station, on the Santa Fe Railroad. This well has })een drilling for the last 18 years, and a depth of 3000 feet has been reached. The Chicago Oil Company's well in the SW^ of Sec. 35, T. 11 N., R. 1 W., is located on the west side of the Calico IMountains, and a depth of over 2000 feet is reported. The Giroux well in the SEj of Sec. 17, T. 32 S., R. 4 E., is located a mile w^est of Black Canyon. A depth of 440 feet is reported. The Mojave Oil Company's well in the SEj of Sec. 14, T. 11 N., R. 12 W., is located about 2|- miles southeast of Mojave. A depth of 1100 feet is reported. In Cajon Pass, and in the region north and west of the Paso, there is an area of highly-tilted deposits consisting of fangloraerates, coarse conglomeratic sandstone, clays and shales. Dickerson^ believes these to be of upper IMiocene age, and to represent lake and land-laid deposits. The San Bernardino IMountains consist mainly of granitic rocks, together with smaller areas of highly altered cry.stalline sediments of Paleozoic age. District Lying West of the San Bernardino Mountains. This district comprises the fertile valley land lying in the vicinity of Redlands, San Bernardino and Chino. On the north and northeast it is bounded by crystalline rocks of the San Gabriel and San Ber- nardino ranges; on the east and southeast it extends into Riverside County for a few miles, where it is terminated by crystalline rocks of the Peninsula Range. At the extreme southwest corner lie the Chino Hills, compDscd of sedimentary rocks of Tertiary age. The greater portion of this area is covered by recent soil and valley alluvium, but it is probable that the crystalline rocks which bound it on three sides are present at no great depth beneath this surface soil. There are two areas of unaltered sedimentary rocks within this district. One lies south of Redlands, and is composed of light-colored clays and shale, together with beds of gravel. These beds are continuous with similar beds in the vicinity of Beaumont and San Gorgonio Pass, and will be discussed more fully under the article on Riverside County. It can be noted here, however, that they contain no indication of petroleum. The second area of sedimentary rocks lies in the Chino Plills. This is the ^University of California. Department of Geology. Bull. 14, Vol. S. The Martinez, Bocene and Associated Formations at Rock Creek on the Western Border of the Mojave Desert. By Roy E. Dickerson, 1914. PETROLEUM RESOURCES OF CALIFORNIA. 159 only portion of San B<'rnardino County, or of the entire region under (liscnssion in this ehiiplcr. tliat offers the slightest possibility of con- taining oil. These liills, \vhi» h lie to the south and west of Chino, are the northeast portion of the Puente Hills of Los Angeles County, but are known locally as the Chino Hills. The formations exposed consist mainly of sandstone and diatomacoous shale belonging to the lower portion of tlie ^lonteri^y Series, which is known in this locality as the Puente formation. At the extreme south end of this area, along the Santa Ana River, the lower Puente is overlaid by a small area of Fernando. The diatomaceous shale of the Puente is the source of the oil in the proven fields of Los Angeles and Orange counties, and within the area under discussion it contains indications of oil. These consist of numerous outcrops of oil sand and bituminous shale. The general structure consists of a monocline dipping to the northeast in which there are minor anticlinal folds. The region can not be considered as favorable for the accumulation of oil in commercial quantities. This is due to the lack of reservoir beds overlying the Puente, and to the general unfavorable structure. There have been a number of wells drilled in this region, the majority of which encountered small showings of heavy tar in the sandstone beds of the Puente, but failed to produce on a commercial scale. There is no reason to believe that wells drilled here in the future would have any better results. Following is a list of the abandoned wells: The Chino Land and Water Company's wells were located on See. 32, T. 2 S., R. 8 W., and encountered heavy oil between 900 and 1000 feet. The Chino Valley Beet Sugar Company's wells were located on Sec. 30, T. 2 S., R. 8 AV., and encountered heavy tar between 450 and 465 feet. At the present time the following wells are drilling in this area: The International Petroleum Company's well is located on Sec, 17, T. 2 S., R. 8 AV. ; The Pomona Petroleum Companv's well is located in Sec. 28, T. 2 S., R. 8 W.; The Chino-Corona United Companv's well is in See. 1, T. 3 S., R. 8 W. The Mahala Oil and Gas Company's well is in Sec. 13, T. 3 S., R. 8 W. All of these wells have reported showings of heavy oil. Riverside County. The eastern half of the county, lying east of the Salton Sink area, is a mountainous and desert region, commonly known as the Colorado Desert. The chief mountain ranges are the San Bernardino Range and the Hathaway and Chuckawalla mountains. The level desert area.s are covered by recent sand, while the mountain ranges are composed of crystalline rock, chietly granites and ancient metamorphic sediments. On the west slope of tlie Hathawa.y ^Mountains, bordering the Salton Sea, Pliocene beds of red and white clay and gravel are reported. They apparently contain no evidence of petroleum and are probably not of marine origin. Along San Gorgonio Pass, from Whitewater to Redlands, there are outcrops of gritty clay shales and gravels, probably of Pliocene age. 160 CALIFORNIA 8TATE MINING BUREAU. The total areal extent of these l)e(ls is al)out 36 miles in length from east to Avest, and about 12 niih's in width from north to south. Small patches of the same formation are found in tlie hills east of liemet and alonof the north side of Temeeula Cici-k in tlic vieinity of ^lurrietta and Temeeula. In all of these localities tliey lie on tlie eroded surface of the uiulerlyins' crystalline rocks. These beds can not be ccusid( red as oil bearing. This statement is based on the following facts: They contain absolutely no indication of oil, such as seeps, or gas blows ; they contain no diatomaceous shale, or other organic material that is capable of forming oil; their total areal extent and thickness is such that even if they did contain organic material, the amount of oil capable of being formed would be negligible. Lastly, it is doubtful that they are of marine origin, it being probable that they I'cpi-esent laud-laid desert dei)osits. Nevertheless, the follow- ing wells are being drilled in this region: Riverside County Oil Com- pany well No. 1 in Sec. 12, T. 2 S., R. 1 W. ; Painted Hills Oil Syndi- cate well No. 1, Sec. 25, T. 2 S., R. 3 E. ; Beaumont Crude Oil Company well No 1 in Sec. 15, T. 3'S., R. 1 W. ; ^Moreno Oil Company well No. 1, Sec. 15, T. 3 S., R. 2 W. ; Neuvo Oil Company well No 1, Sec. 26, T. 3 S., R. 7 W. That portion of the county lying south from San Gorgonio Pass to the San Diego and Orange county lines, is a mountainous region of the Peninsula Range. It contains two rather flat areas, one known as the San Jacinto Basin, and the other as the Temeeula Basin. The moun- tains in the northern portion are known as the San Jacinto JNIountains, while those south of Temeeula Creek are known as the Santa Ana JMountains. The major portion of this region is covered with crystal- line rocks, consisting of granites, lava flows and ancient slates and schists, probably of Triassic age. None of these rocks, of course, are capable of containing oil. Around Hemet, Temeeula and Murritta are the deposits of shales and gravels of Pliocene age referred to in the preceding paragraphs. Along Temeeula Wash, between Elsinore and Corona, there are approximately five small patches of rocks of Eocene age, which are lying on the eroded surface of the underlying crystalline rocks. These consist of red, yellow and white clays, con- taining beds of lignite and probably belonging to the Tejon formation. They seldom cover a square mile in extent, and the maximum thickness is about 600 feet. They show no evidence of petroleum. A well drilled for oil in 1915, located about a mile east of Lucerne, encountered the following formations: to 250', gravel and conglomerate, probal)ly Pliocene; 250' to 927', clays and shales, probably of Tejon age; at 927' crystalline rocks were encountered. In the valley area between Corona and Riverside, forming the extreme southwestern end of the county, the surface is covered mainly with recent valley alluvium. But it is probable that this is underlaid at no great depth by crystalline rocks, especially that portion of the area lying east of the Santa Ana River. In .several places the granite actually outcroi)s in low rounded buttes. Along both banks of the Santa Ana River, in the vicinity of Rincon and where the river crosses PETROLEUM RESOURCES OP CALIFORNIA. 161 the boundary line into Orange County, there are outcrops of Monterey shale (Puente) and Fernando sandstone. These formations are con- tinuations of similar beds in the Chino Hills region and described in the article on San Bernardino County. The total ai'cal extent tliat these bed.s cover in Riverside County is not over four square miles. While they belong to the oil-bearing series, there is no evidence that they would produce any appreciable amount of oil in this region. It is barely possible that tliey iiiiiiht contain some dry tar sands. Two wells are being drilled in this general region, the N. B. Tannehill well in Sec. 35, T. 2 S., R. 7 AV., and the Corona Oil Company's well in Sec. 2, T. 3 S., R. 7 W. These wells are located about four miles north of Corona and about three miles from the granite buttes. 11—13322 162 CALIFORNIA STATE MINING BUREAU. CHAPTER XIII. Region of the San Joaquin Valley. (Includes the following- counties: San Joaquin, Stanislaus, Merced, the western one-thii'd of Madera, the western two-thirds of Fresno, Kings, the western half of Tulare and Kern.) The region of the San Joaquin Valley contains the chief producing fields of California. These are found along the west side of the valley from Coalinga to Sunset, and on the east side in the region immediately about Bakersfield. In addition to containing the chief proven areas of the state, the valley may be regarded as offering the best opportunities for future development. These inchide not only the development and extension in the already proven areas, but also include the possibility of discover- ing new fields buried beneath the surface soil of the valley floor. GENERAL GEOLOGY OF THE VALLEY. The principal formations which are exposed consist of approximately 20,000 feet of nnaltered sediments of Tertiary age, ranging from the Eocene to the late Pliocene. These ai'e overlaid by small thicknesses of recent Quaternary deposits. On the east and south sides of the valley these sediments rest against the crystalline rocks of the Sierra Nevada, Tehachapi, and San Emigdio mountains. On the west they rest on the eroded surface of the older Cretaceous and Franciscan rocks of the Coast ranges. It is very probable that during the greater portion of the Tertiary period the valley was a great inland sea, the eastern and sonthern edges being marked approximately by what is now the Sierra Nevada, Tehachapi, and San Emigdio mountains, while the present Coast ranges were a series of islands. Twice during this period were great thicknesses of organic sediments deposited and these beds may be considered as the ultimate source of the greater portion of the oil now being produced in the valley. The oldest of these formations is of Oligocene age and is known as the Kreyenhagen shale. It consists of approximately 1500 feet of pink diatomaceons and foraminiferal shale. The area occupied by this formation may be considered as lying along the western side of the valley from approximately the vicinity of Tulare Lake north to the vicinity of the northwestern boundary of Stanislaus County. This shale is the source of the greater portion of the oil produced in the Coalinga field. The second deposit of organic shale of the Tertiary period is of Miocene age and consists of nearly 5000 feet of diatomaceons shale belonging to the Monterey and Santa IMargarita series. The area occupied by it may be regarded as covering the entire southern end of the valley south of Tulare Lake. This ]Mioeene shale is the source of the oil in the Sunset, IMidway, Elk Hills, INIcKittrick, Belridge, Lost Hills and Kern River fields. From the above it is evident that the productive areas of the San Joaquin will be in the districts occupied by these two deposits of organic shale. PETROLEUM RESOURCES OF CAIJFORXIA. 163 In addition, diu-ing the Cretaceous period, there was an older body of organic shaU; deposited belon^inp: to the Chico f(»niiation and known as the ^Moreno shale. Tliis consists of about 2tlOO i'eet of diatoniaceous and foraminiferal shale and occupies an area along the foothills of the Coast ranges from Coal in ga north to Livermore Pass. It is the source of the small amount of light-green Cretaceous oil produced in the old Oil City field at Coalinga. It is important only in the Coalinga district and even then it fails to i)n)(1u(e an aii})r('eial)le percentage of the output. The reservoir formations in which the Tertiary oil has collected consist mainly of porous sandstone l)eds which overlie the two shale deposits. In the case of the Kreycuhagen shale the so-called Vaciueros sandstone at Coalinga acts as the reservoir from which the oil is produced. The oil from the ^Monterey and Santa ^largarita shales has collected mainly in the porous sandstone beds of the ]\IcKittrick group. Some of the oil. however, is found in sandy beds within the organic shale deposits, this being the case at the Lost Hills and Bclridge fields in the deep, light gravity oil zone. STRUCTURE. The general structure of the San Joaquin Valley is that of a great syncline, lying between the Sierra Nevada favdt block in the east and the anticlinorium of the Coast ranges on the west. Within this great syncline, however, there are series of anticlinal folds which are marked on the surface in most cases by low rolling hills. These are found mainly along the western side of the valley and for the most part project obliquely out into the valley from the main body of the Coast ranges. In some cases, however, these structures lie out in the valley floor and run parallel to the Coast ranges, such as the folds of the Lost Hills and Elk Hills fields. In some cases, also, there is no evidence of these structures on the surface as is exemplified by the buried anticline of the Bclridge field. It is on these folds that the oil has been trapped and collected and the proven fields are located. All of these structures that are at all evident have, with one exception, been drilled upon and found pro- ductive. It is, therefore, necessary if new fields are to be found, that other structures which are not at present known, be discovered. Such structures in all probability exist, buried beneath the floor of the valley with the greater portion of the surface evidence of their existence removed by erosion. This possibility will be discussed in the following paragraphs under "Buried Structures." The one exception referred to above consists of the great Kettlemen Hills anticline. This fold, to date, remains to be proved as containing oil in commercial quantities. BURIED STRUCTURES. As stated above, the chief hope of finding new fields in the San Joaquin Valley lies in the possibility of locating structures which are buried beneath the surface soil of the valley. One such fold was dis- covered when the Belridge field was found productive. At the present 164 CALIFORNIA STATE MINING BUREAU. an area around Button willow, which apparently shows some evidence of containing a buried anticline, is being tested and with encouraging results to date, such as c|uantities of gas and small showings of oil. As stated above, there is little or no evidence of these buried structures on the surface, in the form of outcrops of rocks or low hills, such as mark the already proven areas. The chief surface evidence that might be present would be slight elevati(»ns and ridges that rise above the dead level of the valley floor. Also some evidence might be furnished by water wells and prospect holes. It is evident that these folds will be found only by a close study of the topography and logs of water wells within the region in which they are likely to occur. The general area in which the writer believes these structures are likely to be found in the San Joacjuin Valley is in the districts referred to above as being underbid by the organic shale beds of the Kreyenhagen, Monterey and Santa Margarita formations, namely an area along the west side of the valley, running from the vicinity of the northwestern boundary of Stanislaus County southward to Tulare Lake, and a second area comprising the entire floor of the valley lying south of Tulare Lake. In the first area the oil would ])e formed from the Kreyenhagen sliale and collect in the Vacpieros sandstone. In the second area the oil would form in the Miocene shales and collect in the McKittrick beds. Fig 12 shows two hypothetical sections across the valley. Section AB in the region north of Coalinga and Section CD in the area south of Tulare Lake. These two sections show the possible source and reservoir beds in each district, as well as two kinds of possible accumulation — a possible anticlinal fold, shown in the left half of the sections, and in the right half a possible monoclinal structure along the old shore line of the sea in which the diatomaceous shales were deposited, and where the oil might accumulate by reason of a possible overlap of the reservoir bed on the upturned edges of the shale. These two areas have been shown on Plate I, colored in blue, as pos- sible oil land. This does not mean that oil fields are going to be found over this entire region, or for that matter, that any will be found. It simply indicates that within this region there is a fairly good chance that buried productive structures may be found. REGION OF THE PROVEN FIELDS. The proven fields of the San Joaquin may be divided into three general groups. One, those fields lying along the west side of the valley from Sunset to Lost Hills and commonly known as the "West Side Fields"; second, the Coalinga field; and third, the Kern River field, commonly known as the "East Side Field." THE WEST SIDE FIELDS. These begin at Sunset and stretch north in an almost unbroken line of derricks to Lost Hills, a distance of nearly fifty miles. In these fields the oil has had its source in the diatomaceous shale of the IMonterey and Santa Margarita formations, and has accumulated mainly in the over- lying sandstone beds of the IMcKittrick group. Exceptions to this are found in the Lost Hills and Belridge fields and in the Twenty-five Hill PETROLEUM RESOURCES OF CALIFORNIA. 165 ©4^ cpiPAam cjjaig <5i PP.'J I'.O ^IS'.'S'sod Pl»y 1!0 aiqissod a busy +seo;) •"54^ eppABimejjaig piay |!0 3iq!«sod P13y 110 si'^'.'ssod , PP!i l!0 ua-^o-id i ^bui?^ +e'eoO >< :/',M \*v,^ ihl ■/■■|:d / ■(•(■■ ;-V.' lid) it'; 41 U^J \-:M^ u 1- Ol- s tH - rD o a bti es i) ■^ 1- Oj I-H -i-t 0) _ iJX) .X C3 a n o 0) 4) 4_t cn c3 v^' ^ 0) s 3 o o H) ca U* 0) C3 n ^ "k H S o CO '-> 1; X 0) 1 .a 4-1 m d ^ ,^ o • ^ -1-" "^ cS 'r. a o • o •~j C3 ^1 a> /■' .o r^ • r-l r/) r« .^ O 5 P. (T Cl r3 O a ^ C3 c t/3 CI •a Oi o tlJ cn +-* a o 73 ■J. -> o o c: 73 ■/. a o c *^ 7J o o •Ji Q g O ^_< ^^ A O o D p< <1> >. 7} M* in 166 CALIFORNIA STATE MINING BUREAU. area at Taft, where some of the oil has collected in the sandy beds of the Miocene diatomaceons shale and has given rise to the so-called ''shale oil." Also at Sunset, on the Pioneer anticline, some oil has col- lected in the Vaqueros sandstone. MIDWAY-SUNSET. The Midway-Sunset area is generally considered as one field, which stretches in an unbroken line of production from Sunset to a point three miles north of Shale, a total distance of nearly twenty miles. The southern portion is known as tlie Sunset district and the northern portion as the jNIidvvay district. The Sunset district lies at the extreme southern end of the valley and may be considered as embracing the region around Sunset, Maricopa and the Maricopa flats. Its northern limits are placed at the furthest town- ship north of the San Bernardino Meridian (T. 12 N.), at which point the Midway district is considered as beginning. The oil has collected along a monocline that runs from Sunset to Maricopa,^nd in a plunging syircTthe which lies just north of Maricopa, and finally in the great "Thirty-five" or "iMaricopa" anticline, which runs out of the hills into Maricopa flats at the northern end of the field. This last structure has been one of tlie most prolific folds discovered in California. On its northern flank is located well No. 1 of the old Lake View Oil Company. This well w;is probably the largest ever 'brought in' in California. It flowed wild for approximately eighteen months, with a reported produc- tion of over 8,000,000 barrels and a maximum daily production of about 65,000 barrels. At the present time it is producing about 30 barrels per day. The Sunset field may be considered as about three-fourths drilled up. The most favorable area for extension lies eastward from Hazelton and Pentland towards the San Emigdio District, especially along the Pioneer anticline and the Western INIinerals area. In INIareh, 1921, the total proven area in this field was 5868 acres. The Midway district may be considered as comprising the region around Taft, Fello^vs, Shale and the Buena Vista Hills. The oil has col- lected along three general lines of structure. The first of these may be considered a.s an eastward-dipping monocline, containing minor anti- clinal folds, some of which are quite extensive, such as the "Twenty^-five Hill anticline. " This structure exists along the foothills of the Temblor Range, west of the IMidway Valley, and in general takes in the region back of Taft and Fellows. The Avells on this structure average around 2000 feet in depth and are fair and constant producers. East of thi area lies the IMidway Valley, which, structurally, is a plunging syncline. While oil has collected along this structure, the wells are not very prolific and this, together with the depth to the oil (average about 3000 feet) and serious water conditions, has not made drilling very profitable in this area. The last structure consists of the dome of the Buena Vista Hills, which lies .iust east of the ^Midway Valley. In general these hills may be regarded as an elongated dome, along th(^ crest of which there are minor anticlinal folds. This region is the district of the largest pro- ducers and the heavy gas pressure. It is probable that the IMcNee lease of the Standard'Oil Company, on Sec. 36. T. 31 S.. R. 23 E., when in its prime about eight years ago, was the most prolific square mile of •S PETROLEUM RESOURCES OF CALIFORNIA. 167 oil territory in the world. The average depths of wells in the area is about 3000 feet. While big gushers are no longer found here, the region still produces fair sized wells. In general, the ^lidway district may 1)0 considered as two-thirds drilled up. The most favorabl(> arca.s for exteusion lie at the cast and west ends of the Buena Vista Hills. In addition the region north from Fellows to IMcKittrick, lying ea.st of the highway, offers opportunity for small- well development. In ]\Iarch, 1921, the total proven area was 39,447 acres. The total daily average production in the Midway-Sunset area in December, 1920, was 84,580 barrels of oil. The average number of wells producing was 2429, with an average daily production per well of 35 barrels of oil and 18 of water. The gravity ranges from al)out 11° Baume to 31° Baume, the heavy oil being found along the outcrops in the Sunset district, while the lighter oil is encountered in the sealed anticlines of the IMaricopa Flat and the Buona Vista Hills. Figure 2, section 1, page 17, .shows the general structure across the IMidway field in the vicinity of Taft. McKITTRICK FIELD. The ^IcKittrick field lies about three miles north of the present nortlieni limits of tlie Midway field. It is probable, however, that future drilling in the low hills east of the highway will connect the two fields. These low hills contain several well developed anticlines in the iMcKit- trick formation which are capal)le of producing small wells of heavy oil at depths of from 1000 to 1500 feet. The structure of the McKittrick field as mapped by Arnold & Johnson^ is extremely complicated, consisting of a double anticline, overturned. However, recent Avork on the underground structure indicates that this is not the condition. A peg model, based on the well logs and con- structed by the Department of Petroleum and Gas of the State ^Mining Bureau at Taft, indicated that the structure really consists of a great over-thrust fault, the older I\Ionterey shale being thrust over the younger McKittrick beds. This structural condition exists in the McKittrick field proper, which lies between iMcKittrick and Reward, and west of the McKittrick Valley. The wells start down in the diatomaceous shale of the JMonterey and encountei- showings in these beds, but the productive sands are not reached until the McKittrick sands are entered below the fault zone. While the wells are not large producers, they are steady and long-lived, and show a remarkably slow rate of decline. This probably is due to the fact that the oil is heavy and continues to hold the gas in solution over a long period of time, thus forcing it to do its full share of work in expelling it from the sands. This process is explained more fully in Chapter I, under "Saturation and Recovery. ' ' The low hills east of the ^McKittrick field proper, and separated from it by the McKittrick Valley, which structurally is a syncline, are known as the McKittrick Front field. The structure here consists of three small, parallel anticlines. Periodically this area has been the scene of t^fiHing operations, which after a few years have ceased and the wells 'U. S. Geol Survey. Bull. 406. Preliminary Report on the McKittrick-Sunset Oil Region. By Ralph Arnold and Harry Johnson. 1909. 168 CALIFORNIA STATE MINING BURE.\U. for the most part have been abandoned. At the present time the produc- tive region is confined to the property of the Cymric Oil Company and Nevada County Oil Company. There is, however, no reason wlw this area should not be commercially productive, as past drilling and the present return on the Cymric and Nevada County properties indicate that long-lived wells of from 30 to 40 barrels daily yield can be obtained at depths ranging from 800 to 1500 feet. The gravity of the oil is about 15° Baume. The trouble with the past work has been that the chief company which formerly operated there was lax in shutting off water, and was mainly concerned with drilling deep holes into the IMonterey shale, where only small showings were encountered, whereas the real production lies at moderate depths in the jNIcKittrick formation. In March, 1921, the total proven area in the McKittrick field was 1635 acres. The total daily average production in December, 1920, was 7260 barrels. The average number of wells producing was 377, with an average yield per well per day of 20 barrels of oil and 70 of water. BELRIDGE FIELD. The Belridge field lies out in the flat valley area, about four miles north of the jMcKittrick field. The structure connsists of a buried anticlinal fold, of which there is no surface evidence. "Well logs indicate that the McKittrick formation is present on the axis to a depth of about 800 feet, below which brown shale is encountered, this probably being diatomaceous shale of the Monterey or Santa Margarita formations. There are two distinct oil zones, one a shallow, heavy oil zone, found at the base of the McKittrick formation, and the second a deep light-oil zone, found in the Monterey shale. The first zone is the principal source of production and yields from 40 to 60 barrel wells of from 17° to 24° Baume gravity oil, at depths ranging from 800 to 1200 feet. The light-oil zone consists of lenticular areas of fine, sandy shale, which produces a light-gravity oil of over 30°, commonly known as shale oil. The depths of wells in this zone vary from 3000 to 4500 feet, and generally have an initial production of about 150 barrels. The zone, however, is extremely spotted, and no correlation of the sands from well to well is possible. The North Belridge field lies at the southern end of the Antelope Hills, and has a small production from sandy lenses of shale in the IMonterey and Santa Margarita formations. THE LOST HILLS FIELD. The Lost Hills field lies about twelve miles north of Belridge. The structure consists of an anticlinal fold striking about N. 45° W. and plunging sharply to the southeast. The only surface evidence consists of a few outcrops at the northern end, and it has been necessar}' to determine the positions of the fold by well logs, as in the case of the Belridge field. The structure is probably a continuation of the Kettle- man Hills anticline. The underground conditions are similar to those of the Belridge field. The wells, however, are generally larger and better producers than in the latter area. In March. 1921, the total proven area in the Belridge-Lost Hills area was 4379 acres. The total daily average production in December, 1920, was 11,500 barrels. The average PETROLEUM RESOURCES OF C^VLIFORNIA. 169 number of wells producing was 571, with a daily average yield per well of 21 barrels of oil and 21.5 of water. The limits of both the Belridge and Lost Hills fields have been prac- a great nat-toppea aome on wnicn the dips range from li" to lU". On ~ Elk Hills Field, Kern County (Showing- Tupman Lease of Standan '""'"M inri?" ,S3i ing Tupiiiaii Ltuac o! Standard Oil Company, Sec. 36, T. 30 S., R. 24 E.), 168 CALIFORNIA STATE MINING BURE.\U. for the most part have been abandoned. At the present time the produc- tive region is confined to the property of the Cymric Oil Company and Nevada County Oil Companv. There is. however, no reason whv this ...jige PETROLEUM RESOURCES OP CALIFORNIA. 169 number of wells producing was 571, with a daily average yield per well of 21 barrels of oil and 21.5 of water. The limits of both the Belridge and Lost Hills fields have been prac- tically determined. Tliore is. however, a possibility of small-woU devel- opments in tlie region at the north end of Lost Hills and around the North Belridge area. THE DEVILS DEN FIELD. The Devils Den field lies to the northwest of Lost Hills. While .small, shallow wells of from five to ten barrels have been reported in this region for a number of years, no commercial production has been obtained to date. These wells lie in the flat valley area to the south and east of what is known as the Pyi'finiid Hills. The formations exposed in these hills consist mainly of diatomaeeous shale of the Santa jNLargarita, with some Vaqueros sandstone. Both formations are folded into a number of sharp antjclines. In the region to the west of the hills, the older Cretaceous and Oligocene formations are exposed. On the eastern edge of the hills the shale dips at angles of from 30° to 40° to the east, and apparently disappears beneath the valley soil. It is probable, how- ever, that beneath the valley soil the IMcKittrick formation is present, lying uneonfonnably against the shale, and dipi)ing at a slightly less angle to the east. The oil, which probably had its origin in the shale, has apparently' collected at the contact of these two formations, mainly iirtlic basal sands of the McKittrick. If the surface sand could be renioved. it would probably be apparent that the so-called Devils Den field is nothing more than a series of seepages at the contact of the Santa Margarita and IMcKittrick formations. The shallow w^ells above referred to start down in the valley soil, and at depths from 100 to 300 feet encounter these seepages and oil sands, penetrating them for about 50 feet. There are in the neighborhood something like twenty of these shallow welLs, almost all of which have encountered oil, and have been reported as capable of producing from five to ten barrels per day. How- ever, none of these have been pumped over any length of time, so no estimate can be made as to their commercial value. The chief interest the Devils Den district has, however, is that it indicates that the McKit- trick formation is oil-bearing in this region, and that in the flat area from three to four miles east of the region of the shallow wells there may be a buried structure which is capable of producing large Avells. Therefore, the flat area between Devils Den and the Lost Hills field is worthy of being thoroughly investigated for evidences of buried structure. THE ELK HILLS FIELD. The Elk Hills field lies to the northeast of the Midway district, being separated from the Bnena Yista Hills by the ^Midway Valley. At date of this report, this region is the chief 'gusher' area of the .state. In Decem- ber, 1920, a total of 34 wells were producing approximately 40,000 bar- rels of oil per day, an average of about 1176 barrels per well per day. The initial production varies from 2000 to 6000 barrels in the Tupman area and from 100 to 400 barrels in the Hay area. The structure consists of a great flat-topped dome on which the dips range from 2° to 10°. On 170 CALIFORNIA STATE MINING BUREAU. the flanks of this general structure, however, there are a number of sharp minor anticlines, which apparently do not influence underground condi- tions. The actual underground structure probably conforms in a large measure to the surface topogra])hy. To date the proven area consists of two districts, one in the vicinity of Sec. 36, T. 30, R. 23 E., known as the Hay area, and the other in tlie vicinity of Sec. 36, T. 30, R. 24 E., known as the Tnpman area. Drillins: to date indicates that the proven area can be carried to a distance of about one mile north or south of the center of the dome. The total proven area in March, 1921, was 1451 acres. Following is a brief description of the field, written for this report by C. C. Thorns •} "The Elk Hills cover, roughly speaking, an elliptical area about six- teen miles long and seven miles wide, with the major axis running in a northwesterly and southeasterly direction. These hills reach a maximum elevation of about 1540 feet in Sec. 28. T. 30 S., R. 23 E., M. D. B. and M., and topographically represent the anticlinal structure of the area. ''The structure probably represents a single major anticline with minor folds on either flank which ])robably do not extend deep enough to affect the oil l)earing formation, or if they do reach that depth are mere slight undulations. The surface drainage indicates that the present crest of the hills corresponds quite closely with the axis of the fold. This broadly-arching anticline has low angles of dip and probably extends from about IMcKittrick to the north end of Buena Vista, where it plunges beneath the San Joaquin Valley. The axis of the fold probably passes south of the northeast corner of Sec. 8, T. 31 S., R. 25 E. Sufficient drilling has not yet been done to definitely locate the sub-surface struc- ture. However, present indications are that the probable axis runs from a point near the northeast corner of Sec. 8, T. 31 S., R. 25 E., about through the center of Sec. 6, T. 31 S., R. 23 E., the northwest corner of See. 1, T. 31 S., R. 24 E., then nearly in a straight line, slightly convex to the north, to about the northeast corner of Sec. 36, T. 30 S., R. 23 E. "The approximate dips as shown by the correlations of the oil-bearing formations are as follows : "Dip along the east line of the Standard Oil Company Tupman wells, on Sec. 36, T. 30 S., R. 24 E., abont 400' in a mile to tlie north. "Dip along the south line of the Standard Oil Company Tupman wells is about 500' in a mile to the east. The dip to the southwest from the northeast corner of Sec. 36, T. 30 S., R. 23 E.. is about 230' to the mile. "The logs of the wells on Sec. 36. T. 30 S., R. 24 E., and Sec. 31, T. 30 S., R. 26 E., show about 700' of sandy formation (sandy shale or sand), then about 2000' of shale or sandy shale. At this point the top of the oil zone is encountered, which in the deepest well stratigraphically in this area has been drilled only about 340' below the top of the oil-bearing formation. These oil-bearing formations are mainly sand. ' ' The logs of the wells of the Standard Oil Company wells on the Hay and Carman leases on Sec. 36, T. 30 S.. R. 23 E., show about 1200' of sandy shale and sand above the gas zone, then about 1200' of rotten shale comprising the gas zone. From this depth to the greatest depth drilled in this area lies the oil zone, which is practically all sandy shale. The deepest well, stratigraphically, in this westerly portion of the proven •Deputy State Oil and Gas Supervisor, Taft, California. PETROLEUM RESOURCES OF CALIFORNIA. 171 field is Standard Oil Company well No. 15, which has been drilled about 1400' below the top of the oil zone. "There is not sufficient i:-('olo<,M<'al information available to correlate stratigraphically the formation in the easterly and westerly portions of the proven Elk Hills field, and, therefore, it cannot be said definitely whether or not the oil-bearing zones in the two fields are at the same stratigraphic horizon. The upper or sandy formations, however, are probably Tulare or Paso Kobles. The formations below this depth are probably all Etchegoin, since it is the generally accepted belief that none of the wells in this field have yet been drilled deep enough to reach the Montere}'. The oil-bearing formations in the easterly portion of the field, it will be noted, are mainly sand, while those of the westerly portion are shale or sand}- shale. "No prominent markers have yet been noted in this field above the oil zone. Occasionally some two or three wells seem to show a possible marker above tbe oil zone, but adjacent wells lack such markers. The main oil sand, however, does seem to be a consistent marker in the eastern portion of the field. "No ])romin('nt water zones luivc been noted and no water has been found below the top of the oil zone in the easterly portion of the field or below the top of the gas zone in the westerly portion of the field. The lowest top water has been quite definitely located as being about 200 feet above the top oil sand. "As has been noted above, in the westerly portion of the field there is a 1200' gas zone, while in the easterly portion no gas zone has been noted. See. 36. T. 30 S., R. 24 E., M. D. B. and M. Only one oil zone has apparently been penetrated and the depth and thickness of this zone has not been determined, since the deepest wells drilled are apparently still within the zone." For a complete description of the "West Side fields the reader is referred to the publications of the T7uited States Geological Survey'^ and the Cali- fornia State ]\lining Bureau. - A full description of the surface geology and underground conditions will be found in these reports. In addition, peg models of the various fields are open to inspection at the office of the Department of Petroleum and Gas, California State ^Mining Bureau, Taft, California. COALINGA FIELD. This is the most northerly field in California from which any appre- ciable amount of production is being obtained. Tin re lypcs of structure are present. ' 'The great, plunging Coalinga anticline, wliidi I'uns out into the valley in a southeast direction, forms what is known as the 'East Side field,' and furnishes the greater portion of the production. Lying west of this anticline is the plunging Coalinga syncline, which runs down the Pleasant Valley. "An area around the head of this syncline is productive^ SjOn the west side of the Pleasant Valley, and forming the 'U. S. Geol. Survey. Bull. 406. Preliminarv Report on the McKittrirk-Sunset Oil Region. By Ralph .\rnolcl and Hanv .John.son. 1909. U. S. Geol. Survey. Professional Paper 116. The Sun.'^et-Midway Oil Field. By R. W. Pack, 1920. -'California State Mining Bureau. Bull. 69 and Map folio. Petroleum Industry of California. By R. P. McLaughlin and C. A. Waring, 1914. First, Second, Third, Fourth and Fifth .Annual Reports of the State Oil and Gas Supervisor, California State Mining Bureau. 172 CALIFORNIA STATE MINING BUREAU. west limb of the Coalinga syncline, is the 'West Side' field. This structure is a monocline. The formations exposed along this monocline and on the Coalinga anticline consist of the Cretaceous, the Tejon, the Kreyenhagen shales, the Vaqueros sandstone, the Santa ]\Iargarita and the Etchegoin and Jacalitos formations. These last three formations are not oil-bearing in this region, and only act as an overburden above the oil measure. The greater portion of the oil was formed by the Kreyenhagen shales and has collected in the sandstone beds of the Vaqueros formation. This oil is black and of an asphaltic base. The gravity ranges from about 11° to 38° Baume. A little oil was also formed by the Moreno shale, which is the upper- most member of the Chico. This oil is found in the old Oil City field, at the head of the Coalinga anticline. This is the only region in Cali- fornia where the Cretaceous is commercially productive. Here, under the most favorable conditions, the total daily production is 135 barrels. This comes from twelve producing wells. The oil is light green in color and ranges above 50° in gravity. The wells in the West Side field range from 500 to 2500 feet in depth. Those at the head of the syncline and along the Coalinga anticline in the East Side field range from 800 to 4000 feet in depth. In March, 1921, the total proven area was 14,272 acres. The total daily average production in December, 1920, was 40,500 barrels of oil. The average number of wells producing was 1288, with an average daily yield per well of 35 barrels of oil and 10 of water. The limits of the field are practically fixed, with the possible exception that the proven region may be extended south of Waltham Canyon along the Jacalitos anticline Old wells drilled in this region have reported small showings, and it is worthy of being examined carefully as a pos- sible productive area. The region west of the proven area and up Waltham Canyon, west of Alcade, is not favorable for drilling operations. For a detailed description of the geology and underground conditions, the reader is referred to the publications of the United States Geological Survey^ and the State Mining Bureau. - KERN RIVER FIELD. This field lies along the Kern River, just north of the town of Bakers- field. The structure consists of a low monocline, dipping to the south- west, the dips varying from 5° to 7°. The reason for the oil collecting in a structure such as this is somewhat obscure. Following are two theories Avhich may possibly account for the accumulation: the first is that the oil has been trapped in the monocline by a buried anticlinal fold which lies out in the valley west of Bakersfield. The second is that the oil has accumulated by reason of the unconformity of the McKittrick beds on the upturned edges of the IMonterey shale. The oil is found 'U. S. Geol. Survey. Bull. 39S. The Geology and Oil Resources of the Coaliiga District. By Ralph Arnold and Robert Anderson, 1910. U. S. Geol. Survey. Bull. 581-D. Geology and Oil Prospects of the Waltham. Priest, Bitterwater and Peachtree Valleys. By R. "W. Pack and W'alter English, 1914. ^California State Mining Bureau. Bull. 69. Petroleum Industry of California. Bv R. P. McLaughlin and C. A. Waring. The First, Second, Third, Fourth and Fiftii Annual Reports of the State Oil and Gas Supervisor, California State Mining Bureau. PETROLEUM RESOURCES OF CALIFORNIA. 173 in the loose, incoherent sands of the upper portion of the IMcKittrick formation, and probably had its oriirin in the diatomaceous shale of the Monterey Along the northeast edge of the fieUl the bitnininized beds at the base of the ^IcKittriek may be seen. However, no jNIonterey shale is exposed, the IMcKittrick beds aparently overlapping directly on the Vaqueros formation which in turn rests on the granite. At Poso Creek, however, the jMonterey shale is exposed beneath the IMcKittrick and it is probably present beneath these latter beds over a considerable portion of the Kern River field. Tliis field is a consistent, steady producer of long-lived wells of from 40 to 100 barrels daily. The oil averages in gravity about 15° Baurae and the wells range in depth from 200 to 1500 feet. The total proven area in March, 1921, was 7152 acres. The total daily average production in December, 1020. was 20.067 barrels of oil. The average number of producing wells was 2067 and the daily average yield per well was 10 barrels of oil and 40 of water. Recent exploration work has extended the field north to Poso Creek. The wells in this new district are small producers, coming in with an initial yield of about 40 barrels at depths of about 2000 feet. From this it is apparent tliat the Poso Creek district is not going to be as prolific a producer as the old field. To date, no commercial production has been obtained north of Poso Creek, but several wells drilling just north of the creek have reported showings, and it is probable that the Poso Creek district can be extended to the nortli for several miles j'et. The struc- ture and geological conditions are somewhat obscure, as there is a lack of good surface outcrops. It is proliable, however, that the same condi- tions are present here as in the main Kern River field. In the region east of Bakersfield, and south of the Kern River, no production has been obtained except for a few small wells along the south bank of the river. From the meager surface indications that are available, it is probable that the formations which are present in the Kern River field continue south across the river and underlie the plateau region east of Bakersfield. This region is, therefore, worthy of being examined carefully as a possible, productive area. UNPROVEN AREAS. SOUTH END OF THE VALLEY. Tliis i-egion includes the tiat i)ortion of the valley lying south of Tulare Lake, together with the foothills of the San Emigdio and Tejon regions. This foothill area at the south end of the valley has been mapped and reported on by the U. S. Geological Survey.^ The formations exposed along the San Emigdio and Tejon hills are similar to those found in the IMidway-Sunset district. At IMuddy Creek and along "Wheeler Ridge there are seepages of oil in the McKit- trick formation. The general structure of this foothill area, how- ever, is unfavorable for the accumulation of petroleum, with two exceptions: these consist of the Wheeler Ridge anticline and the Tejon 'U. S. Geol. Survey. BuU. 741. Preliminary Report on the Geology and Possible Oil Resources of tlie South End of the San Joaquin Valley. By Robert Anderson, 1910. U. S. Geol. Survey. Professional Paper 116. The Sunset-Midway Oil Field. By R. W. Pack, 1920. 174 CALIFORNIA STATE MINING BURE/VU. Hills autirline. Both of the striu-tiires are worthy of being tested, and the Wheeler Ridge fold is now being drilled on by the Standard Oil Company. In the flat valley area lying out in front of these hills and extending north to Tulare Lake, there are no surface indications of petroleum. However, the outcrops in the foothills that surround this portion of the valley on three sides indicate that it is underlaid by the ^Miocene diatomaceous shale, and the reservoir beds of the ]\IcKittrick forma- tion and, as stated in the article on "Buried Structures," it may possibly contain anticlines which may prove i)roductive. Section C-D, (page 165) is a hypothetical section across this portion of the valley, and shows how possible oil-bearing structures may exist. REGION OF THE FOOTHILLS OF THE TEMBLOR RANGE. This area lies west of the Sunset-Midway, jNIcKittrick and Lost Hills fields. In general this region is not favorable for tlie accumulation of any appreciable amount of petroleum. The formations are older than those of the producing field, and the structure is highly tilted and folded. On Sec. 36, T. 29 S., R. 20 E., there is a production of about 20 barrels per day of 15° Baume gravity oil, from about fifteen shallow wells. This is known as the Temblor field. The oil has accumulated in the Vacjueros sandstone at a point where it is faulted against the ^Monterey shale. The accumulation is only local and of no great conuuercial value. In the Gould Hills there are some tar sands at the contact of the Santa ^Margarita and ]\IcKittrick formations. Wells drilled here have encountered small showings of heavy oil, and there is no reason to believe that future drilling would meet with any better success. In the flat area lying between the northern end of the Temblor Range and the Lost Hills-Belridge area, there is a possibility that buried anticlinal folds exist which may be productive later. This region is known as the Antelope Hills and Antelope Plain district. KETTLEMAN HILLS. The district consists of the range of hills running from Coalinga south to Lost Hills, and lying just west of Tulare Lake. They are separated from the Diablo Range by the Kettleman plain. The struc- ture of these hills consists of a great anticline, the axis of which runs along the highest ridge in the center of hills, with a general northwest and southeast trend. The dips on the flank vary from 10° to 35°. This structure may be considered as a continuation of the Coalinga anticline and it, in turn, continues into the Lost Hills region. The formations exposed along the axis of this fold are soft, loose sands and clays of the Etchegoin formation. As to what is present beneath these beds there is no direct evidence. It can be assumed, however, that in the northern portion, formations similar to those found in the Coalinga field should be present; while on the southern end, rocks similar to those found in the Lost Hills and Devils Den district should be present. This assumption is based not only on the fact that the Kettleman Hills is a portion of the general structure that runs from Coalinga to Lost Hills, and should, therefore, contain rocks PETROLEUM RESOURCES OF CALIFORNIA. 175 those regions, l)ut it is also based on a study of the forma- osed in the hills west of the Kottlenian plain and which runs ■By IWi^-ii j^iiiuiu aim rcooert Anaerson, I9i( Midway Oil Field, Kern County (Looking East from Fellows East from Felbws; Elk ffiUs and Buena Vista in Backgfround) . 174 CALIFORNIA STATE MINING BUREiVU. Hills anticline. Both of the struetures arc -worthy of being tested, and the Wh eeler Ridge fold is now being drilled on by the Sta ndard from Coalinga to Lost Hills, and should, therefore, contain rocks PETROLEUM RESOURCES OF CALIFORNIA. 175 similar to those regions, but it is also l)asetl on a study of tlie forma- tions exposed in the liills west of the Kettleman ])lain and which runs from Waltham Canyon to Devils Den. The oil possibilities may be summed up as follows: The structure is extremely favorable for the accuiuulalion of petroleum. At the northern end of the hills it is possible tbat the oil-bearing formations similar to those found in the Coalinsa field may be present, while in the southern end a similar condition may exist in regard to the oil- bearing fornuitions of the Lost Hills region. Wliether or not these formations, if present, would contain oil in commercial ciuantities, or be within reach of the drill, can only be told by actual drilling. Wells drilled to date indicate that there is no commercial production above approximately 4000 feet. There are, however, sufificient favor- able conditions present to make this region worthy of being tested by at least several deep wells located on the axis of the fold. In the northern end about nine wells have been drilled, only two of which were located sufficiently close to the axis of the fold to afford a fair test. These two wells were the Coalinga-Kettleman, located in Sec. 4, T. 22 S., R. 17 E, and drilled to a depth of 4810 feet, and the Medallion Oil Company well, located in Sec. 20, T. 22 S., R. 18 E., drilled to a depth of 3848 feet. Neither of these wells revealed any showings of oil, and it is pi"obal)le that they did not penetrate deep enough to encounter the Vaciueros sandstone which is believed to contain the oil in this portion of the hills. At the south end of the hills two wells have been drilled in recent years, one of which, the Crescent Petroleum Company's well, has been abandoned, and second, the Standai'd Oil Company's 'Kettleman well,' is still drilling. The Crescent well was located in Sec. 2, T. 25 S., R. 19 E., and was drilled to a depth of about 2700 feet. Between 1600 and 1700 feet several small showings of black oil were encountered. When tested, these showings yielded al)out 3 bailers full of oil. It is reported that the Standard Oil Company, in their well on Sec. 34, T. 24 S., R. 19 E., encountered similar showings at about the same depth. The foi'mations penetrated by the Crescent well were soft sands and clays of the iMcKittrick series. A description of the geology of the Kettleman Hills, as well as the region to the west, can be found in Arnold and Anderson's Coalinga report.^ KREYENHAGEN HILLS REGION. This district may be considered as comprising the foothills of the Diablo Range, between Waltham Creek and Devils Den. The north- ern and central portions are known as the Kreyenhagen Hills and the southern end in the vicinity of the McClure Valley is known as the Pyramid Hills. The general structure of the region is that of a steep monocline dipping about 40° to the east. The formations exposed are the Cretaceous, the Eocene, the Kreyenhagen shales, the Vaqueros, the Santa ]\Iargarita, and the Etchegoin and Jacalitos formations. At the northern end, in the vicinity of Waltham and ^U. S. Geol. Survey. Bull. 39S. Geology and Oil Resources of the Coalinga District. By Ralph Arnold and Robert Anderson, 1910. 176 CALIFORNIA STATE MINING BUREAU. Jacalitos creeks, the hills widen out and there is a well-developed anticline lying in the hills east of the general monoelinal structure. This fold is known as the Jacalitos anticline, and was referred to in the article on the Coalinga field as a possible productive area. The axis of this fold is plunging sharply to the south, so tliat in the vicinity of Jacalitos Creek the oil-bearing formations (Vaqueros) are more than likely below a depth of 4500 feet. The Azores well, located on the axis o'f the fold, in Sec. 26, T. 21 S., R. 15 E., reached a depth of 4420 feet and found only slight showings, these being reported at about 3500 feet. At the northern end of this fold, however, in the vicinity of Waltham Canyon, the oil-bearing formations should be shallower, and it is possible that the proven area of the Coalinga field may be extended into the region. Along the general monoelinal struc- ture of the central and southern portions of this region, there is little possibility of obtaining oil in any appreciable quantities. This is due to the unfavorable structure. In Canoas, Big Tar and Little Tar canyons, there are prominent seepages of oil in the basal sands of the Vacpieros, and w^ells drilled here have encountered small quantities of oil. The territory in the region of these canyons is known as the Krey- enhagen field. Two general groups of wells have been drilled here; namely, those that are drilled in the Kreyenhagen shales and draw their oil from sandy beds in that formation, and those that start down in the Santa INIargarita and probably draw their oil from the Vaqueros. The first group is credited with eight wells, all of which encountered showings and one of which, Kreyenhagen No. 1, located in the SE^ of Sec. 32, T. 22 S., R. 16 E., is reported to have yielded at the rate of about 15 barrels per day at the start, but soon fell to 5 or 6 barrels. The depth of the well Mas 650 feet. The oil is said to have been light green, and of 37° Baume gravity. The second group includes four Avells, all of which encountered showings of heav}', black oil. Well No. 1, of the Black Mountain Oil Company, located in the NW:|^ of Sec. 33, T. 22 S., R. 16 E., is said to have produced 5 or 6 barrels of 18° Baume gravity oil at a depth of 720 feet. None of the wells in either group were of commercial value. This region is chiefly of interest because the oil-bearing formations are dipping to the east, and may possibly continue across the Kettle- man plain, and come up again in the Kettleman Hills. Here, on account of the anticlinal structure, the conditions for the accumula- tion of oil in appreciable quantities would be quite favorable. In the region between the Kettleman Hills and the Kreyenhagen Hills there is little possibilit.v of finding oil, as the structure is tJiat of a great syncline in which the oil-bearing formations are beyond the reach of the drill, and also very likely barren of oil. The geology and oil possibility of the Kreyenhagen Hills is covered in Arnold and Ander- son's Coalinga Report.^ THE REGION NORTH OF COALINGA. This district includes the foothills and the western side of the valley from Coalinga to Livermore Pass. The general structure of the foothill area is that of a great monocline dipping to the east. In •U. S. Geol. Survey. Bull. 398. The Geology and Oil Resources of the Coalinga District. By Ralph Arnold and Robert Anderson, 1910. PETROLEUM RESOURCES OF CALIFORNIA. 177 the hills just north of Salado Creek, and at the mouth of Panoche Creek, there is evidence of anticlinal folds, and further work in this region may disclose other folds. The formations that outcrop along the monocline consist of the Cretaceous, the P]occne, the Kreyenhageu diatomaeeous shales, sandstone and shale beds of the [Monterey series, the Santa ^Margarita formation, and finally loose sands, clays and shales of Pliocene age, belonging to the Etchegoin, Jacalitos and Tulare formations. Of these, tlie Krcyenhagcn shales and the sandstone beds of the Monterey series, are of chief interest, as the former is a probable source of petroleum, and the latter would act as the reservoir forma- tion for such oil. The popular belief that there are no evidences of petroleum in this region is contrary to facts. Numerous seepages have been reported to the writer a.s occurring along ^Monocline ridge. In the SW ^ of Sec. 9, T. 16 S., R. 13 E., about one-fourth of a mile southwest of the Union Oil Company's well, tliere is a good outcrop of dry oil .sand which, when tested by the writer with ether, gave an excellent test for petroleum. 'J'his sand occurs about the middle of the Monterey series, and would indicate Uiat this fornuition is a possible reservoir for oil in this region. The possibilities may be summed up as follows : Along the foothills the chances are not good on account of the steep monoclinal structure. The fact, however, that the Kreyenhagen shales outcrop here, and are a possible source of oil, and that the lower Pliocene sands above them show petroleum, would lead to the ])elief that, if favorable structure could be found in this region, in whjch the lower ^Miocene sands were folded, they would contain petroleum in commercial quantities. The most likely place for such structures would be out in the flat valley area lying from 2 to 10 miles east of the foothills. In this region it is possible that buried anticlinal folds may exist similar to the Lost HilLs and Belridge areas, and along the axis of which the lower [Miocene sands would be present. Consideration, however, must be taken of the fact that a great overl)urden of Pliocene and upper [Mio- cene beds are also present, and in case any buried fold was located, these beds would have to be penetrated before the possible oil sands of the lower Miocene would be encountered. However, the entire region of the west side of the valley may he considered as worthy of being carefully examined for the possibility of containing buried structure which might be indicated on the surface by low mounds or ridges. Section A-B, Fig. 12 (page 165), is a hypothetical section across this portion of the valley, showing how {)ossible oil-beai-ing structures may exist. This mattei- is also taken up at the beginning of this chapter under "Buried Structures." REGION AROUND TULARE LAKE. In the low marshy area around Tulare Lake gas has been obtained for a number of years from shallow water wells, and recently some deep wells have been drilled which showed large Ciuantities of gas at depths below 2000 feet. In no case, however, has the State Mining Bureau been able to verify any of the reported oil -showings. The gas encountered resembles strongly the 'marsh gas' obtained in the wells 12—13322 178 C/VLIFORNIA STATE MINING BUREAU. around Stockton and Sacramento. It is perfectly odorless and burns with an uncolored tlarae. As yet there is no evidence that this gas is connected with any petroleum deposit. The surface in this region is flat and covered with valley alluvium and soil wliich gives no evidence as to what is beneath it. This portion of the valley, however, falls within the area that may possibly contain buried anticlinal folds, and it is possible that the gas found here has accumulated by reason of such a fold. Whether or not it would contain petroleum, or actually exists, can only be told by drilling. BUTTON WILLOW DISTRICT. This district lies about 8 miles northeast from, and parallel to, the Elk Hills field. Running in a northwest direction across the center of T. 29 S., R. 24 E., is a low ridge which continues to the northwest in the direction of Lost Hills. It is believed that this ridge may mark the axis of a buried anticline which, on account of its relationship to the Elk Hills and Lost Hills area, should be highly productive. Out- side of the low ridge there is no other surface evidence that would indi- cate a fold. Attention was first called to this area by Mr. R. N. Ferguson, of Bakersfield, who gave the name of Button Willow anti- cline to this low ridge. At the present time four wells are drilling here and encouraging results have been obtained to date. The Petroleum :\Iidway wells, located in Sec. 12, T. 29 S., R. 23 E., and Sec. 6, T. 29 S., R. 24 E., have both encountered large quantities of gas which is in apparently sufficient amount to be of commercial value. In the National Exploration well, on Sec. 27, T. 28 S., R. 23 E., samples tested by the State IMining Bureau, from a vicinity of 3000 feet, gave good indications of petroleum. The region may, therefore, be considered as Avorthy of being thoroughly tested. It may also be noted here that the results obtained at Button Willow will, in a large measure, prove or disprove of the theory that the San Joaquin Valley contains buried productive structures other than those already known. EAST SIDE OF THE VALLEY. This region as described here includes the eastern portion of the valley lying north from the vicinit}' of Tulare Lake to Stockton. The eastern side of the valley lying south of Tulare Lake has been included in the article on the "South End of the Valley." At Terra Bella the Pliocene beds which continue on north to this point from the Kern River area, disappear, and from this point north to the region east of ^ladera, the vallej' soil rests directly against the crystalline rocks of the Sierra Nevada. Evidence of the presence of sedimentary rocks is lacking, and it is probable that the granite is present at shallow depths beneath the surface sand over a great portion of this region. From the vicinity of Madera northward to Stockton, the foothills of the Sierra Nevada are composed of highly-altered slates and intru- sive rocks belonging to the ^lariposa formation (Jurassic). Resting against these older rocks along the foothills is a body of sedimentary rocks of Eocene age. These beds consist of a coarse sandstone at the PETROLEUM RESOURCES OF CALIFORNIA, 179 bottom whioh, in somo plaoos, is of a dark red color, due to stains from various iron eumpouuds. Above tbe sandstone are found beds of clay, volcanic tuff, and eonfrlomorate. It is probable that these beds repre- sent the most southerly extension of the lone formation and Dickerson^ has found ^ood Tejoii fossils in tlie sandstone member in the vicinity of I\Ierced Falls. These beds do not contain any indication of petroleum, and they lie in a gentle monocline, dipping a])out 4° to the east. It is i)robable that they underlie the greater part of the northeast portion of the San Joaquin Valley. The geological conditions of this region are distinctly unfavorable for the production of petroleum. This is based on the following facts: There are no surface indications of oil; the oil-bearing formations, which are present in the proven areas of the valley, are lacking here; such .sediments as are present are not of a character to form oil; there is no structure evident that is favorable for the accumulation of petroleum. From the above it is evident that the region is not a desirable one in which to prospect for oil. Near Knights Ferrv, in See. 18, T. 1 S., R. 12 E., W. H. Clary is drilling a well. At Oakdale, in Sec. 1, T. 2 S., R. 10 E., the Southern Oil and Gas Company's well has reached a depth of nearly 4000 feet. Showings have been reported from this well, but liave never been verified bj- any representative of this Bureau. 'University of California. Department of Geology-. Bull. 17, Vol. 9. Stratigraphy and Fauna of tlie Tejon Eocene of California. By Roy E. Dickerson, 1916. INDEX. Page Accumulation of Oil, Areas of 20 Conditions necessary for 21 Metiiods of 1^ Tlieory of — 1^ Acreage, Total proven • — 11 Acknowledgments 1*^ Alameda County 61 Alpine County *8 Amador County 48 Anderson and Pack 61, 62, 70, 93 Anderson. Robt. 75, 173 Anticlinal Theory 14 Arnold. R. 61, 109 and Anderson, Robt.- — 102, 175, 176 and Johnson. Harry 98, 99, 167, 171, 172 Arrovo Grande Oil Field — 32, 95 Augur, Irving V — 10, 131, 136, 151 Ball, Sidney H 155 Bear Valley 52 Bell, H. W 103 Belridge Field — ___ 32, 168 Bitterwater and Peachtree Valley, Geology of 78 Bradley-San Miguel Oil Company — 90 Bradlev, Walter W 10 Branner, J. C — 62, 63, 66 Brea Canyon, Area vicinity of 123 Field — 136 Bullis, C. G — ___ 10 Burnt Shale areas — 22 Butte County, Eastern 48 Western — 49 Button Willow District 178 Calaveras County 48 California, Geological facts of origin and accumulation 13-22 Geology and structure of__-- 23-34 Index map of — 8 Map of In Pocket Oil-bearing formations of — 23—34 Statistics for 1920 11 Summar.v of conclusions — 11 Theory of origin and accumulation of oil in '. 13—22 Camarillo, Oxnard and El Rio, District 126 Carpinteria, Region near-- 111 Carrizo Plains and San Juan Creek 98 Geology — 100 Oil Wells — 100 Chico formation -_ 27, 28 Chino-Corona United Co — 159 Chino Land and Water Co _- 159 Ciervo Anticline, Crest and flanks of 75 Clark, Prof. B. L.. University of California 10, 30, 34 Coalinga District 31 Field -- r 171 Coast Ranges 23-32 From Pajaro River as far south as Santa Maria River 69-101 From San Francisco Bay as far south as Pajaro River, Area 60-68 Coast area north of Bay of San Francisco, Possibilities of oil 35-44 From Santa Maria to Santa Monica Mountains 102-130 Collom, R. E 10 Colusa County 49 Conclusions, General summary of — 11 Conejo Field, Ventura County 128 Contra Costa County -_ — _— 60 Coyote Hills Field 137 Cretaceous formations — 27 182 INDEX. Page Cuyama Valley, Area of 107 Cymric Oil Co 68 Daly, Marcel 16 Decius, C. L 10 Del Norte County 44 Desert Region — 153—161 Southeastern 26 Devils Den Field 32, 169 Diablo Range south of Panoche Valley 70 Vallecitos District 70 Diastrophic theory 16 Diatomaceous shale — 31, 32 Dickerson, R. E 56, 154, 158 El Dorado County 48 Eldridge, G. H., and Arnold, Ralph 67, 112, 113, 121, 131, 157 Elk Hills Field — 170 El Rio, Oxnard and Camarillo, District of 126 Elsmere Canvon wells — 130 English, Walter A 88, 89, 90, 94, 98, 112 Eocene formation 28 Eureka Wells 121 Fairbanks, H. W 95, 96, 112, 149 Ferguson, R. N — 10 Folger, A. — 10 Foraminifera 13 Formations, nonoil-bearing 26 Oil-bearing — 27 Fresno County 48, 162 Production, 1919-1920 11 Gas blows 21 Gas pressure, Explanation of — 16 Gavilan Mountains, Area of 86 Geology and Structure of California — 23-34 Sacramento Valley, west side 49 Geological structures yielding oil in commercial quantities 16 Glenn County 49, 51 Great Central Valley of California 24 Hershey, O. H 155 Hollister and Lomas Muertas, Area between 69 Hooker Hills 56 Huasna District 96 Huguenin, E. 9, 10 Humboldt County — 40 Map of In Pocket Wells drilled and results — 42 Huntington Beach Field 138 Hydrostatic pressure — 16 Imperial County 148 Map of ^^-In Pocket Wells drilling 152 Inglewood Hills to Beverly, Region of 140 International Petroleum Company 159 Introduction -- 9 Inyo County 153, 155 Kern County, eastern — 153, 155 In Sierras — 48 Midway District, showing accumulation 17 Western half 162 Production 1919-1920 11 Kern River Field 172 Kettleman Hills 174 Kew, W. S. W 113, 148, 151 Kings County 162 Kreyenhagen Hills region 175 Laguna to Santa Ana Mountains, Across Laguna Hills and Capistrano Valley 144 La Jolla, San Diego County 147 Lake County 49-51 Lassen County 47 Lautenwasser Creek, Structure 61 Lawson, A. C 23, 60, 61 INDEX. 183 Page Lewis Creek — '^ and peachtree Valley, Monterey County 70 Lewis, J. O l^ Lomas Muertas and Hollister, Area between 69 Loon Point, Wells near HO Los Angeles City Field -— 135 Los Angeles County, northeastern 153, 156 Northwestern — 12 8-130 Wells drilling 129 Production, 1919-1920 -- H Southern 'and Orange County 131-144 Salt Lake Field 17. 135 Los Gatos 64 Lost Hills Field 32, 168 Madera County, western — 162 Mahala Oil and Gas Company 159 Marin County 35 Point Reyes Peninsula 37 Martinez formation 28 MarysviUe Buttes 56 McDonald, R. C — 10 McKinney, Don 10 McKittrick Field 167 McLaughlin, R. P., and Waring, C. A 94, 98, 100, 111, 155, 171, 172 Madera County, eastern part 48 Mariposa County — 48 Mendocino County 39 Wells drilled — 40 Merced County 162 Midway District, showing accumulation 17 Midway-Sunset area 32, 166 Miocene formation — 30 Modoc County — 46 Monocline, form of 15 Mono County 153-154 Montebello Field 135 Montecito, Region west of 111 Monterey Bay, District bordering on 83 Monterey County 31, 32, 82 Monterey sliale formation — 31, 32 Montezuma Hills 57 Napa County 49, 51, 52, 56 Nevada County 48 Newhall Fields 129, 130 Newport District 138 Northeastern California oil possibilities 45-47 Lava beds of 25 Oak Ridge and South Mountain, North flank of 117 Oil-bearing formations. Description 23-34 Cretaceous . 27 Eocene 28 Oligocene 29 Miocene -- 30 Pliocene 32 Oil City Field 2S Oil, Origin and Accumulation 13-20 Possibilities Northeastern California 45-4 7 Possibilities, Area north of Bay of San Francisco — 35-44 Production by counties 11 Surface indications of 21 Summary of conditions necessary for accumulation in commercial quantities-- 21 Ojai Valley Field -- 32, 113 Ojai Valley and Sulpliur Mountain 114 Oligocene formation 29 Olinda Field -- 136 O'Neal, Tom 10 Orange County, Coastal plain area 134 Laguna to Santa Ana Mountains 144 and Soutliern Los Angeles County 131-144 Eastern portion of 142 Production 1919-1920 11 184 '* ' INDEX. Page Origin and accumulation of oil, theory of __13-20 Oxnard, El Rio and Camarillo, district around 126 Pack. R. W., and English, W 77, 91, 92, 157, 171, 172, 173 Pan-American Petroleum Co 123 Parkfield District 92 Location of wells in 93 Peachtree Valley, Geolog>- of 78 Petroleum (see Oil) Piru Field --__32, 120 Eureka wells 121 Placer County, Eastern 1 48 Western -- 49 Pleyto oil district 88 Wells drilled in 88 Plumas County 48 Pomona Petroleum Company 159 Potrero Hills 51-52 Production of oil for 1920 11 Proven oil land, Total 11 Prutzman, P. W 113, 129, 131 Point Arena, Map of In Pocket Point Reyes, geologic section — 37 Report, purpose of 9 Reservoirs ^ 18, 19 Richfield District 136 Rincon Creek and Cajpinteria, wells near — 110 Riverside County 153, 159 Sacramento County 49 Sacramento Valley, including east slope of Coast Range and foothills of Sierra Nevada, Area of -_ 49-59 District of valley floor 56-57 East side and foothills of Sierra Nevada 58-59 Western side, sections 53 West side and east slope Coast Ranges 49-56 West side, Map of In Pocket Salinas Valley from Greenfield south to County line 89 From King City soutli to County line. Area of 91 Mouth of, and district Bay of Monterey 83 Salinas to Greenfield, Area of 86 Salt Lake Field I35 Section of 17 San Antonio Hills, Area of 87 San Ardo, Area west of 90 San Benito County 1 69-82 River valley , 82 Southwestern portion of 76 and Tres Pines valleys 70 San Bernardino County — 156 Mountains lying west of 158 Wells drilling — 159 San Diego and Imperial counties 145-152 San Diego County — 145 La Jolla : 147 Santa Margarita Valley, along north side — 147 Wells drilled 146 San Fernando Valley district 132 San Francisco County 62 San Gabriel Valley 142 San Juan Creek and Carrizo Plains 98 San Joaquin County 162 Valley, Region of 162-179 East side of 178 Proven fields, Region of — 164 Tulare Lake, proven fields and possible accumulation 165 Unproven areas 173 San Luis Obispo County 94 San Mateo County 62 San Pablo Valley indications . 61 San Pedro Hills, Region of 141 San Pedro and Santa Monica, Region between — ^ ^.^_,.^_„. 141 INDEX. 185 Page Santa Ana, upper San Benito and Tres Pinos valleys, Area of-- 70 Santa Barbara County, Coast area of 109 Santa Barbara County 102 Production 1019-1920 — 11 Proven fields and adjoining areas . 102 Santa Maria Field, sliowing accumulation 17 Santa Clara Countyl 63 Moody Gulch — _— 30, 31, 65 Santa Cruz County 66 Santa Fe Springs District 137 Santa I^ucia Mountains, Area of 83 Santa Maria Field 31-32 Santa Maria River to Santa Monica Mountains, Coast area from 102-130 Santa Monica and San Pedro region, Between 141 Santa Paula I-'ield 32, 115 Santa Ynez Mountains west of Santa Barbara, Area of 106 Sargent Ranch field — 66 Schumacher, \V. E 10 Sespe Canyon area 120 Shasta County 46 Sliell Co. 66, 90 Sierra County 48 Sierra Nevada Mountains 25, 26 Area of — 48 Signal Hill district 139 North to Inglewood Hills, Region 140 Simi Valley, Section of 114 Unproven areas -- 124 Sisar Creek field : 113 Siskiyou County — 45 Solano County 49, 52, 55, 57 Sonoma County — 36 Evidences of petroleum 38 South Mountain and Oak Ridge, District along north flank of 117 Staldf-r, W -- 43 Standard Oil Co 76, 106 Stanislaus County — 162 State Mining Bureau cited __43, 62, 64, 77, 86, 89, 91, 94, 96, 98. 110. Ill, 112, 113, 117, 129, 131, 146, 149, 151, 154, 171, 172 State Oil and Gas Supervisor 11, 103, 104, 105 Structure, types of — 15 Sulpliur Mountain and Ojal Valley 114 Summary of Conclusions 11 Summary of conditions necessary for accumulation In commercial quantities 21 Summerland Field 109 Region northeast of HI WelLs in mountains northeast of 110 Surface indications of oil — 21 Sutter County 49, 56 Syncline, form of --__ 15 Tapo Canyon wells — 122 Tehama County — 49, 50 Tejon formation 29 Temblor Range, region of foothills — 174 Theories as to origin and accumulation of oil 13-22 Thoms, C. C 10, 170 Tickkell, F. 10, 96 Topo Ranch, Geology of — 81 Wells drilled 82 Toro Creek — 76 Tnrrey Field 121 Tres Pinos and San Benito valleys — 70 Tres Pinos, upper San Benito and Santa Ana valleys. Area of 70 Trinity County 44 Tulare County, eastern part — 48 Western half 162 Tulare Lake, Region around — 177 Tuolumne County 48 Tuscan Oil Company — 56 Union Oil Company 123 13—13322 186 INDEX. rage U. S. Bureau of Mines -- 19 U. S. Geological Survey 10, 17. 46, 56, 60, 61, 62, 63, 66, 67, 70, 75, 77, 85, 87, 89, 90, 91, 92, 93, 95, 96, 98, 102, 104, 107, 109, 112, 113, 131, 148, 151, 155, 157, 167, 171, 172, 173, 175, 176 University of California-, Department of Geology 23, 56, 150, 154, 158 Upper San Benito, Tres Pinos and Santa Ana Valleys, Area of-- -- 70 Vaca Valley 51 Vallecitos District -- - 70 Vaqueros formation 30. 31 Ventura County -- 32. 112 Central portion, area of proven fields 113 Conejo Field -- — -- -- 128 Field 116 Northern half. Geology and oil possibilities 112 Production, 1919-1920 11 Santa Monica Mountains district 126, 131 Simi Valley 114 Sulpluir Mountain and Ojai Valley '. 114 Waring, C. A -- 64, 89 and E. Huguenin 155 Watsonville Oil Company 66 Western Union Company 106 West Side field.s -_ 164 Whittier Field -" 136 i'olo County 49, 52, 55 Yuba County 48, 49 13.^22 1-22 3O00 Sea Level" Santa Lucia Series San+a Margarita Pliocene Sec A SeaXevel" Sec c u o a. c « c « o a> a. O- Z3 _5 St & o « (5 w c « u o L. §: 3 Sea Level w Peachtree Sec Fig. 0. Section A-B — East-west section across the San Benito and Tres I'iuos vallej-s, 1 Vallecitos District, San Benito County (adapted from the U. S. G. S. Bull. GOo). Section Monterey County (adapted from the U. S. G. S. Bull. 5S1-D). tl F,-^. 6 "Sea Level A-B Chico Sriswold Hills ciervo anticline. Psnoche Va//ey Sea Level P Sea Level J^ the tovyn of Tres Pinos. San Benito County. Spction C'-D— Nortli-sonth section across fliP :..st-west section across Lewis Cn-ek and the Peachtree Valley in th^ vicinity of Lonoak^^ 13322 THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW BOOKS REQUESTED BY ANOTHER BORROWER ARE SUBJECT TO RECALL AFTER ONE WEEK. 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