o 224 MINERAL PRODUCTION OF CALIFORNIA 1 944 Page Slate 76 producers 184 production, 18S9-1944 • 76 roofing granules 76 Smelters, list of 195 Soapstone 111 composition 111 producers 184 total productions 112 use 112 varieties 111 Soda 1?~ producers 18t. total production 123 Solano County -- 143 Sonoma County 143 Spark plugs, andalusite for 110 Specific gravities of oil produced 25 Spelter. {8ee Zinc.) Standard Oil Company, cited 25-27 Stanislaus County 144 State Division of Oil and Gas, cited 20, 28, 29, 30-o3 State Mineralogist Report, cited 23, 4S, 55 Mining Bureau, cited 50, 55 Oil and Gas, cited 30-33 Stone, miscellaneous 77-82 producers 185-191 production by counties 79-81 production by years S2 Stoneware 90 Strontium . 113 producers 192 Structural materials 64-82 Sulphur 113 production by years : 114 Summary of Mineral Industry, 1944 11 Summary of Operations, California Oil Fields, cited 29, 30-33 Sutter County 144 Talc 111 producers 184 uses 111 Tehama County 145 Tei-ra cotta 90 Tile 90 Tin 5 8 Titanium 59 producer 192 Topaz 96 Tourmaline 96 Travertine 73 Trinity County 145 Trona 122 Tube mill pebbles 78 Tuff, used for building stone 69 Tulare County 145 Tungsten 60 producers 193 total production 61 Tuolumne County 146 Turquoise 96 S. S. Bureau of Mines, cited 20, 28, 41, 44, 45-46, 49, 57, 58, 62, 6S Census Bureau, cited 124 Geological Survey, cited 17, 23, 39, 47, 50, 55, 58 ■Vanadium 61 Ventura County 146 Vitrified brick 66 Volcanic ash 106 producers 178 "Well data, oil 24 Witherite 86 Wolframite 61 Wollastonite 88 Yale, Chas. D., cited 46 Yolo County 146 Yuba County I 147 Zinc 62 producers 194 production of United States 62 total production 63 Zircon 114 50792 11-45 1200 STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES GEOLOGY OF THE SAN JUAN BAUTISTA QUADRANGLE CALIFORNIA BULLETIN 133 Issued by the DIVISION OF MINES FERRY BUILDING, SAN FRANCISCO 1946 UNIVERSriY OF CALIFORNIA LIBRAR > COLLBCE OF AGRICULTURE STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES WARREN T. IIANNUM, Director DIVISION OF MINES WALTER W. BRADLEY, State Mineralogist . GEOLOGIC BRANCH OLAF P. JENKINS Ferry Building, San Francisco Chief Geologist San Francisco Bulletin 133 IVIarch 1946 Geology of the San Juan Bautista Quadrangle California By JOHN ELIOT ALLEN and Operations of the Granite Rock Company Quarry and Plant at Logan, San Benito County By ROYAL E. FOWLE jtrin/eil in caiifornia state printing office 51298 LETTER OF TRANSMITTAL To His Excellency, The Honorable Earl Warren, Governor of the State of California Sir : I have the honor to transmit herewith Bulletin 133 of the Divi- sion of Mines of the Department of Natural Resources, on Geology of the San Juan Bautista Quadrangle, California. This is one of a series of such reports on specific areas in California being presented by the Geologic Branch of the Division of Mines. Two previous reports covered the San Benito and the Jamesburg quadrangles, and were pviblished in the April 1943 and April 1944 chapters, respec- tively, of the State Mineralogist 's annual report. Because of particular geologic features (some of which relate to the San Andreas fault rift) and economic mineral resources, this report is issued in separate bulle- tin form. The report is accompanied by a geologic map and sections, also an economic sheet. The author is John Eliot Allen. There is also a paper especially prepared for this bulletin on Operation of the Granite Bock Company Quarry and Plant at Logan, San Benito County, California, by Royal E. Fowle, engineer and production manager for the company. Respectfully submitted. • Walter W. Bradley State Mineralogist San Francisco, February 8, 1946. (3) CONTENTS Page PREFACE J 7 GEOLOGY OF THE SAN JUAN BAUTISTA QUADRANGLE, CALIFOR- NL\, BY JOHN ELIOT ALLEN 9 OPERATIONS OF THE GRANITE ROCK COMPANY QUARRY AND PLANT AT LOGAN, SAN BENITO COUNTY, BY ROYAL E. FOWLE__ 77 SERVICES OF THE DIVISION OF MINES 83 PUBLICATIONS OF THE DIVISION OF MINES 87 INDEX 105 ILLUSTRATIONS Plates Progress in geologic map publication Frontispiece Plate 1. Geologic map of the San Juan Bautista quadrangle, California In pocket 2. Economic geology of the San Juan Bautista quadrangle, California In pocket 3. Geologic structure sections, San Juan Bautista quadrangle In pocket 4. A, Case hardening and cavernous weathering in Pinecate sandstone, half a mile southeast of Aromas School. B, Pinecate formation ; sandstone with caves 32 5. A, Red beds, dipping south. San Juan grade, 1 mile north of summit. B, Horizontal and cross-bedded gravels in axis of Pliocene syncline 1 mile north of Sargent Station : 32 6. A, Gullying in Aromas red sands in summit highway cut 1 mile north of Langley School. /?, Cuesta topography in Pliocene on south slope of Lomerias Muertas 33 7. Sargent landslide of March 5-9, 1939 33 8. Geological map, Sargent oil field, Santa Clara County 72 9. Aerial photograph showing Granite Rock Company quarry and plant at Logan, San Benito County, November 24, 1941 78 10. A, Granite Rock Company quarry. B, Granite Rock Company quarry, showing 100-foot and 75-foot levels 78 11. A, Granite Rock Company quarry, 75-foot level. B, Loading cars with crushed rock, Granite Rock Company quarry 79 12. A, View east of south across San Juan Bautista quadrangle. B, Look- ing east toward quarry face, Granite Rock Company quarry 79 Figures Fig. 1. Index map showing location of San Juan Bautista and adjoining quad- rangles 12 2. Stratigraphic column in the Gabilan Range 18 3. Stratigraphic column in the Santa Cruz Range 19 4. Santa Lucia granitic rocks (plane polarized light) 22 5. Franciscan volcanic rocks (plane polarized light) 24 6. Lavas of volcanic group (crossed nicols) 32 . 7. Pliocene section along railroad between Betabel and Sargent Station 36 8. Pliocene section along highway 2 miles north of Aromas 37 9. Pliocene section in highway cut 1 mile south of Sargent Station 40 10. Permanente Metals Corporation quarry, 1 mile north of Natividad, Monterey County 68 (5) I I i If I 116" c D E r|G H I J |k l m n |o p q r|s t u v|w X y z|a' b' C d'|e' r' g' h'|i' j' k' l'Im'n^ '2*° 123° 122° 121° 120° 119° 116° 117° 116° 115° O'P' i i 1 PREFACE The new program of publishing colored lithographed geologic maps on uniform-sized quadrangles throughout California is one of the most significant services which the State Division of Mines has ever under- taken. It represents the same type of Avork as the famous Geologic Folios (publication now discontinued) of the United States Geological Survey ; these old folios once sold for 25 cents apiece ; now, if they can be pur- chased at all, second-hand copies cost several dollars each. Under the direction of the Geologic Branch of the Division of Mines, three maps of the new series of quadrangle geologic maps have now been prepared and published. These are the San Benito Quadrangle, by Ivan F. Wilson, and the Jameshurg Quadrangle, by William Morris Fiedler, previously released ; and the San Juan Bautista Quadrangle, by John Eliot Allen, which accompanies -this bulletin. Each map repre- sents the results of several years of research by geologists who have done the work in partial fulfillment of the degree of Doctor of Philosophy at the University of California. Acknowledgment is hereby made to the faculty members of the University, particularly to Dr. N. L. Taliaferro, who assigned and supervised the work. Dr. John Eliot Allen, who mapped the San Juan Bautista quad- rangle is, at present writing. Chief Geologist of the Oregon Department of Geology and Mineral Industries. He chose the area because of its particularly interesting Coast Range features. The world-famous San Andreas rift, with its long history of surprising events, transects the area from northwest to southeast; along it a series of horizontal slips have displaced the west side of the mountain range northward in respect to the east side. Two different geographic and geologic provinces are repre- sented by the terrain on either side of this great rift, so that we know the activity dates far into prehistoric time. The best-remembered event of recent time, however, was the 1906 tremor, caused by an enormous shift along this crustal break. One result of movement along the San Andreas rift is illustrated by the second contribution to this bulletin, a description of a huge granite quarry on the fault, by Royal Fowle. Movement along the fault has crushed the quarry rock to material suitable for extensive economic use. Numerous landslides are associated with the crushed rocks along the San Andreas fault, where water-soaked clays predominate. Some of these slides extend the length of a mile or more. Much older slides can be found trapped between the late Tertiary strata. Within the borders of the San Juan Bautista quadrangle is the Sargent oil field, known before 1860, and operated for many years. Though a small field, it is one of the few which occur in northern Cali- fornia. Each map of the present series of geologic maps is drawn on a very accurate topographic quadrangle base, which shows by contour lines the surface form of the earth. The topographic quadrangles which serve as bases were prepared and published by the United States Geological (7) 8 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Survey, and similar maps are issued for all States of tlie Union. The overprinted colors and symbols representing the different geologic units have been carefully chosen to conform with standard usage. The lithog- rapher, A. Iloen and Company of Baltimore, Marjdand, has been engaged in this sort of work for more than 100 years, and is conveniently located where original transfers of the topographic base maps of the Federal Survey's printing department in Washington, D. C, can be secured. The use of quadrangle geologic maps is manifold. To the mineral industry they are indispensable because they show the structure and position of the rocks as they are related to the mineral deposits which they enclose ; these mineral deposits include metalliferous and non- metalliferous minerals, oil and gas, coal, and ground water. To the agri- culturalist these maps show the rocks from which the soil is derived ; to the engineer they show wiiat rocks may be encountered in road building and in construction ; to the tourist they show not only the geographic fea- tures, roads, streams, ridges, and earth forms, but also the rock forma- tions which often control earth forms, migration of water, distribution of wild life, vegetation, and civilization itself. In California there are about 780 topographic quadrangles on the scale of 1 :62500 (15-minute sheets), on which the series of geologic maps is being issued. About 100 quadrangles (on various scales) have been mapped geologically, but little of the work has been published. In 1938 the Division of Mines issued a geologic map of California on the scale of 1 :500,000, in six sheets. When mounted, it forms a wall map 7 feet square. This earlier, more general map serves as a guide to the greater detail and usefulness of the present series of individual quad- rangles, the scale of which is about 1 inch equals 1 mile. If and when the program of quadrangle geologic maps is completed, the map of the entire State, assembled, would be about 56 feet square. Olaf p. Jenkins, Chief Geologist California State Division of Mines February 15, 1946. GEOLOGY OF THE SAN JUAN BAUTISTA QUADRANGLE, CALIFORNIA* By John Sliot Allen** OUTLINE OF REPORT Page ABSTRACT 11 INTRODUCTION n ACKNOWLEDGMENTS 13 LOCATION AND GEOGRAPHIC FEATURES*. 14 Location 14 Accessibility and transportation 14 Climate 14 Vegetation and exposures 14 Population and industry 15 Land divisions 15 PREVIOUS LITERATURE '_ 15 STRATIGRAPHY 17 Introduction 17 Sur series and Gabilan limestone (pre-Santa Lucia granite) 17 Santa Lucia granite (pre-Franciscan) 21 Franciscan group (Upper Jurassic) 22 General character 22 Agglomerate and tuff member 23 Basalt member 24 Sedimentary members 25 Serpentine 26 Age of the Franciscan 26 San Lorenzo group (Oligocene) 27 General character 27 San Juan Bautista formation 27 Pinecate formation 27 Age and correlation 27 Vaqueros group (lower Miocene) 28 General character 28 Vaqueros sandstone 28 Red beds 28 Columnar sections 29 Age and correlation 30 Volcanic group (lower or middle Miocene) 30 General character 30 Columnar sections 31 Lithology 32 Age and correlation 33 Monterey group (middle and upper Miocene) 33 General character 33 Sandstone, arkose, and clay-shale members 34 Diatomaceous and siliceous shale member 34 Age and correlation 35 Santa Margarita formation (upper Miocene) 35 Purisima formation (middle and upper Pliocene) 38 General character 38 Lithology 38 Columnar sections 39 Unconformities within the formation 42 Age and correlation 42 Aromas red sands (middle? Pleistocene) 43 General character 43 Lithology 44 Physiography 44 Age and origin 45 * Submitted in partial satisfaction of the requirements for the degree of Doctor of Pliilosophy in Geolog-y, in the Graduate Division of the University of California, Berl^elev, California. Manuscript submitted to the Division of Mines for publication May 1945. ** Geologist, State Department of Geology and Mineral Industries, Portland, Oregon. (9) 10 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 STRATIGRAPHY— Continued Terrace deposits and alluvial fans (Quaternary) 45 Brea deposits (Quaternary and Recent) 46 Travertine deposits (Recent) 47 Alluvium (Recent) _ 47 Landslides (Recent) 47 STRUCTURE _• 48 Introduction 48 San Andreas fault 48 Santa Cruz Range 50 Carnadero fault 50 Structures within the Franciscan belt 51 Transverse faulting within the Franciscan belt 51 Sargent fault 52 Branches of the Sargent fault 52 Structures within the Miocene belt 53 Structures in the Pliocene northeast of the San Andreas fault 54 Structures in the Santa Cruz Range southwest of the San Andreas fault- 55 Gabilau Range 55 Introduction 55 Anzar buried fault 56 Cement AVorks fault 56 Pinecate fault 56 County Line fault 57 Folding southwest of San Juan Bautista 57 Vergeles fault 57 Transverse faulting 58 Faulting within the granitic area 58 Structural history 60 Introduction 60 Pre-Oligocene faulting 60 Lower Miocene faulting 60 Upper Miocene or lower Pliocene folding and faulting 60 Late Pliocene or early Pleistocene folding and faulting 60 Middle or upper Pleistocene and Recent deformation and active faulting 61 GEOMORPHOLOGY 61 Introduction 61 Drainage 61 Cycles of erosion . 62 Summary of the Quaternary record 63 Monterey submarine canyon 64 PALEOGEOGRAPHY 65 Introduction 65 Pre-Tertiary 65 Eocene 65 Oligocene — lower Miocene 66 Middle and upper Miocene 66 Pliocene 66 Pleistocene and Recent 66 SUMMARY OF GEOLOGIC HISTORY 67 MINERAL RESOURCES 67 Limestone and dolomite 67 Pacific Portland Cement Company 67 Bethlehem Steel Company 67 Permanente Metals Corporation 68 Small limestone quarries 72 Crushed rock, sand, and gravel 72 Granite Rock Company 72 Small road-metal quarries 73 Petroleum 73 Sargent oil field 73 Other wells 74 Black sands in Capitola quadrangle 74 Barite 75 GEOLOGY — -ALLEN 11 ABSTRACT The San Juan Bautista quadrangle lies east of Monterey Bay, at the junction of Santa Cruz, Santa Clara, San Benito, and Monterey Counties, and covers the extreme southern Santa Cruz and northern Gabilan Ranges in the central Coast Ranges of California. It is traversed by the San Andreas fault and by the Pajaro River, the latter being the only water-gap south of the Golden Gate between the Santa Clara-San Benito trough and the sea. Of 18 cartographic units mapped, 7 appear in the Santa Cruz Range only, 6 appear in the Gabilan Range only, and 5 appear in both stratigraphic provinces. In the Gabilan Range the oldest rocks consist of the Sur series of quartzites, schists, and Gabilan (crystalline) limestones of unknown age. These are intruded by the Santa Lucia acid to basic granitics. San Lorenzo (Oligocene) shales and sandstones lie upon the granite; followed by Vaqueros (lower Miocene) sandstones and red beds; and by andesitic and rhyolitic flows and agglomerates and interbedded sandstones. In the Santa Cruz Range Franciscan (Upper Jurassic) basaltic tuffs and agglomerates are overlain by basalt flows and by sandstones and shales which include limestone and black chert lenses near the base and red chert lenses near the center of the section. Serpentines appear as "cold intrusions" along boundary faults of the Franciscan area. The main portion of the range is composed of Monterey (middle Miocene) arkosic sandstones and clay shales overlain by diatomaceous and siliceous shales. Purisima (Pliocene) and later gravels, sands, and silts unconformably overlie older rocks of both provinces, and are unconformably overlain by Aromas (Pleistocene) red sands and by terrace gravels, alluvial fans, and valley alluvium. Landslides are numerous in areas of Pliocene rocks. Structurally, the Santa Cruz Range is divided by two longitudinal faults which parallel the San Andreas fault, into the Franciscan belt and the Monterey belt, both of which are overlapped by Pliocene rocks at the southeastern end of the range. Folding is most pronounced in the Monterey and Pliocene areas. The Tertiary rocks in the Gabilan Range are separated from the granite by the east-trending Vergeles thrust and are further broken by parallel thrusts and numerous cross-faults. Faulting on the San Andreas zone was initiated in the Eocene, and repeated in the Miocene, Pliocene, Pleistocene, and Recent. The Vergeles and Anzar faults origi- nated in the Miocene, but most of the faulting and folding took place during the upper Miocene-lower Pliocene interval, some faulting and folding occurred in the Pleistocene. Recent minor movements have also occurred. Quaternary eustatic changes in sea level ^ have been less important than differen- tial land movements, resulting in erosion of most of a late-mature land surface, the development of a series of terraces, and changes in drainage within the area. Economic resources include crushed rock, particularly that mined for many years by the Granite Rock Company at Logan quarry ; limestone from both the Franciscan and the Sur series ; and dolomite, being mined near the southern edge of the quadrangle. Sand and gravel have been taken from several small roadside quarries. The Sargent oil field has been a small producer since the 1860s. INTRODUCTION The San Juan Bautista quadrangle is an area of complex structure, the unraveling of which necessitates detailed field work. It is also a key area in the interpretation of the stratigraphic history of the central California Coast Ranges. The Santa Cruz and the Gabilan provinces, two separate structural and stratigraphic units with different histories, are separated in this area by the San Andreas fault, one of the major features of the Coast Ranges. The only water-gap south of San Francisco Bay between the great Santa 1 Changes in sea level that are not the result of elevation or depression of the land. 12 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Fig. 1. iiiOex luai) whowin GEOLOGY — ALLEN 13 Clara-San Benito trough and the Pacific Ocean, cuts through the center of the quadrangle, and this same water-way existed at various times far back into the Tertiary. The epochs of deformation exhibited here differ in at least three points from those prevalent elsewhere in the Coast Ranges. Lower middle Miocene faulting, not previously emphasized, strongly affected the strati- graphic sequence in the area. ' Since no lower Pleistocene is definitely known to be present in the quadrangle, there is no direct evidence of the character and extent of the late Pliocene orogeny. Furthermore, it is impossible to distinguish between the effects of the late Pliocene and mid-Pleistocene diastrophisms. Both are known to be strong in adjacent areas. The writer spent about 5 months in the field during the summers of 1933 and 1934, and the fall of 1944. He was assisted during 1934 by Robert R. Coats. The topographic quadrangle was mapped by the U. S. Geological Survey on a scale of 1 : 62,500 and covers 245 square miles, of which about 60 square miles is alluvium. Aerial photographs made for the Agricultural Adjustment Administration were obtained for parts of the area in January 1945, so their field use was restricted to a few days spent in the field in March of that year. They were, however, of consid- erable use in checking some of the details of the previous mapping, although photographs were lacking for most of the important area south- west of San Juan Bautista. ACKNOWLEDGMENTS The writer is indebted to Dr. N. L. Taliaferro, who suggested the problem in 1932, encouraged its completion in 1944 and 1945, and made valuable suggestions and criticisms. Dr. Olaf P. Jenkins, by impressing upon the draft and ration boards the necessity for publication of the survey, made it possible for the writer to undertake its completion at this time, and F. W. Libbey, director of the Oregon Department of Geology and Mineral Industries, extended the leave of absence necessary. Numerous fossil determinations were made by Dr. A. Myra Keen and Dr. H. G. Schenck of Stanford University, who has permitted the inspection of the list of San Lorenzo fossils collected by the Stanford Geological Survey in 1924. Dr. Bruce L. Clark was very helpful in identifying fossils and assisted in obtaining check lists and locality data. Robert R. Coats spent 4 weeks in the field in 1934, mapped certain portions of the area, and engaged in numerous helpful discussions. Mr. Frank Nelson and Mr. Eric W. Allen, Jr. were companions in the field for varying periods of time. The writer wishes to express his grati- tude to the numerous ranchers in the area for their hospitality and help- ful attitude, and to the officials of several oil companies for their per- mission to use well-log data. The writer also wishes to express his appreciation to the Permanente Metals Corporation for information they supplied, and for the courtesy extended during his visit. 14 SAN JUAN BAUTISTA QUADRANGLE [BuU. 133 LOCATION AND GEOGRAPHIC FEATURES Location The San Juan Bautista quadrangle lies due east of Monterey Bay, about 50 miles south of San Francisco, and covers portions of Santa Cruz, Santa Clara, Monterey, and San Benito Counties. The eastern edge of the quadrangle lies in the Santa Clara-San Benito Valley, and the southwestern portion in tlie Salinas Valley. It covers the north end of the Gabilan and the south end of the Santa Cruz Ranges ; the Pajaro River, which is joined by the San Benito River just east of Pajaro Can- yon, commonly being taken as the dividing line between the two ranges. Accessibility and Transportation With the exception of the higher parts of the Santa Cruz and Gabilan Ranges, all points within the quadrangle lie within a mile or two of accessible roads. The main coastal highway U. S. 101 runs through the area from Gilroy, just off the northeastern edge of the map, to Salinas, 5 miles south of the quadrangle. El Caraino Real originally took a course a few miles east of the present highway, crossing the north- ern spurs of the Gabilan Range east of the ' ' San Juan Grade. ' ' Other paved highways run from Watsonville to Santa Cruz, 18 miles to the northwest ; to Monterey, 25 miles to the southwest ; and over the Hecker Pass to Gilro}^, a distance of 18 miles. Paved roads also follow the Pajaro River from highw^ay 101 to Watsonville and to Hollister, 5 miles east of the edge of the map. Secondary roads are mostly improved and graveled. The main line of the Southern Pacific railroad traverses the area from Gilroy through Pajaro Canyon to Watsonville Junction and Salinas. Climate The climate on the west side of the ranges is mediterranean, with low summer fogs and small winter rainfall; in the Santa Clara-San Benito Valley it is semi-arid, although Hollister has an average annual rainfall of about 13 inches.^ The temperature falls below freezing for short periods during the winter months, and reaches 80 to 100 degrees in summer. Vegetation and Exposures As elsewhere in the Coast Ranges ^ the subsurface geology affects the natural vegetative cover to a lesser or greater degree, depending upon climatic as well as upon topographic factors such as the steep northeasterly and gentle southwesterly slopes discussed by Reed.* In the spring of the year, mapping of the red beds, which are char- acterized by a high percentage of limestone pebbles and boulders, is assisted by the luxuriant growth of the larkspur {Chalochortus alius) which does not grow on the adjacent sandstones and lavas. The first growth of winter grasses on grazing lands underlain by Pliocene sands and gravels frequently enables the determination of the attitude of the beds by means of the denser or lighter bands of grass due to variations in 2 Report on the Cooperative "Western Range Survey in San Benito County, Cali- fornia., (mimeographed) p. 20, 1938. ^. ,t^ilso"' ^"^^^ ^•' Geology of the San Benito quadrangle, California: California Div. Mines Rept. 39. pp. 189-190, 1943. ^Reed, R. D., Wind and soil in the Gabilan mesa. Jour. Geol., vol. 35, pp. 84-88, 1927. GEOLOGY — ALLEN 15 the porosity and fertility of the various layers. Serpentine is nearly always barren of any but a sparse grass cover. Due to the various differing climatic and topographic areas within the quadrangle, no generalizations as to the effect of the underlying for- mations, other than those above noted can be made. Occasional mention is made, however, in the section on stratigraphy, of some of the relation- ships observed. Population and Industry Watsonville, the largest town in the area (population 11,400 in 1944) lies near the center of the west edge of the map ; San Juan Bautista, well known for the mission founded in 1797 and still in good repair, lies toward the southeastern edge of the area. Sargent, Betabel, Chittenden, Aromas, and Watsonville Junction are little more than stations on the Southern Pacific railroad. The wide fertile flood plains and terraces of the lower Pajaro Valley make it an important lettuce and orchard district, while artichokes are extensively grown on the coastal terraces around Castroville just off the southwest edge of the map. An interesting recent development is the planting in the southern terrace area of considerable acreages of guayule sage for the production of rubber. Second only in importance to market- gardening is the beef-cattle industry. The mountainous portions of the area have been grazed since the days of the Spanish ranches. Land Divisions Original Spanish land grants cover most of the quadrangle ; only a few square miles in the Santa Clara aiid San Benito Valleys have been sectionized. Some of the picturesque names ^ are Salsipuedes (get-out- if-you-can), Los Carneros (the sheep), Lomerias Muertas (dead hills). Las Aromitas Y Agua Caliente (little smells and hot water), Canada de la Carpenteria (cleared and plowed valley), Bolsa Nueva Y Moro Cojo (new pocket and lame moor), and Cienega del Gabilan (hawk marsh). A grant about 1 mile square near San Juan was given in 1848 to Patrick Breen, who was one of the survivors of the famous Donner party. Breen maintained a hotel for many years in San Juan Bautista, which was then on the main route both to Monterey and to the New Idria quick- silver mines. His rates were $5 a night, furnish your own bedding and sleep on the floor. An interesting sidelight is the name Fremont Peak, now sometimes used for Gabilan Peak. It was on March 4, 1846, that Captain Fremont, then a trespasser on Mexican territory, raised the American flag on the crest of the peak, the first time the flag had been lifted in California. The date is still celebrated by a local festival in San Juan. PREVIOUS LITERATURE Although the Pajaro Gap was one of the chief passes from northern to southern California, and the Camino Real traversed the area, the first recorded notes of a geologic nature were taken by Whitney and Brewer in 1861," when they were en route to the New Idria quicksilver mines. 5 Marshall, M. L., A pronouncing dictionary of California names, H. J. Carle & Son, 1925. Whitney, J. D., Geological Survey of California; Geology 1, pp. 159-160, 18C5. Brewer, W. H., Up and down California in 1860-64, edited by Francis P. Far- quhar, pp. 117-126, (Yale University Press), 1930. 16 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Later, in 1888, Becker'^ commented on some of the features of the Gabilan Range, and the asphalt deposits near Sargent were noted in early reports of the California State Mining Bureau.^ Early studies were made of nearby areas such as Carmelo Bay,^ the Santa Cruz quadrangle,^^ the Salinas Valley,^ ^ and Pajaro Valley,^^ ^^^t the first geologic reports on portions of the San Juan Bautista quad- rangle were the papers by Eeid ^^ on the granite at Logan quarry, and by Jones ^^ on the Sargent oil field. Other reports on the quadrangle include a physiographic study of a part of the San Andreas fault made by Robin Willis ^^ and the study of the area made by the Stanford Geo- logical Survey in 1924 and published in part by Kerr and Schenck ^"^ in 1925. Their published map, on a scale of 4 miles to 1 inch, covers approximately the southeast one-third of the quadrangle, but unpub- lished maps at Stanford University give considerable data in the Santa Cruz Range as well. In 1938 Bailey Willis ^"^ made a study of the struc- tures in Logan quarry ; Krauskopf and others ^^ examined the great Lomerias Muertas landslide of 1938 ; and Michelin ^^ made a short report with map on the Sargent oil field. Other geological investigations of nearby quadrangles include those of the Point Sur,^^ Salinas and Jamesburg,^! Soledad,^^ and San Benito ^^ ''Becker, G. P., Geology of the quicksilver deposits of the Pacific Slope: U. S. Geol. Survey, Mon. 13, p. 181, 1888. 8 Hanks, H. G., Petroleum: California Min. Bur. Rect. 4, page 289, 1884. Watts, W. L., Petroleum: California Min. Bur. Kept. 10, p. 607, 1890. B Lawson, A. C, The geology of Carmelo Bay, Calif. : Univ. California, Bull. Dept. Geol. Sci., vol. 1, no. 1, pp. 1-59, 1893. "Branner, J. C, Newsom, J. P., and Arnold, R., Santa Cruz folio : U. S. Geol. Survey, Geol. Atlas, no. 163, 1909. 11 Nutter, E. H., Sketch of the geology of the Salinas Valley: Jour. Geol., vol. 9, pp. 330-336, 1901. Hamlin, Homer, Water resources of the Salinas Valley, California : U. S. Geol. Survey, Water-Supply Paper 89, pp. 1-91, 1904. Hawley, H. J., Stratigraphy and paleontology of the Salinas and Monterey quadrangles, California: Geol. Soc. America Bull., vol. 28, p. 225 (abst.) 1917. i^Mackie, W. W., Soil survey of the Pajaro Valley, California: U. S. Dept. Agri- culture, Bur. Soils, Rept. 10, pp. 1331-1372, 1911. 13 Reid, J. A., The igneous rocks near Pajaro : Univ. California, Bull. Dept. Geol. Sci., vol. 3, no. 6, pp. 173-190, 1902. " Jones, W. P., The geologv of the Sargent oil field : Univ. California, Bull. Dept. Geol. Sci., vol. 6, pp. 55-78, 1911. 15 Willis, Robin, Physiography of the San Andreas fault between Pajaro Gap and the Cholame Plains: unpublished Ph.D. thesis, Stanford University, 1924. Willis, Robin, Physiography of the California Coast Ranges : Geol. Soc. America Bull., vol. 36, pp. 041-678, 1925. i« Kerr, P. P., and Schenck, H. G., Active thrust faults in San Benito County, Cali- fornia : Geol. Soc. America Bull., vol. 36, no. 3, pp. 465-494, 1925. "Willis, Bailey, San Andreas rift, California: Jour. Geology, vol. 46, pp. 793- 827, 1938. 18 Krauskopf, K. B., Peitler, S., and Griggs, A. B., Structural features of a land- slide near Gilroy, California: Jour. Geology, vol. 47, pp. 630-648, 1939. 19 Michelin, James, Sargent oil field: California Div. Mines Bull. 118, pp. 475-476, 1943. 20 Trask, Parker D., Geology of the Point Sur quadrangle, California : Univ. Cali- fornia, Bull. Dept. Geol. Sci., vol. 16, pp. 119-186, 1926. -1 Piedler, William Morris, Geology of the Jamesburg quadrangle, Monterey County, California: California Div. Mines Rept. 40, pp. 177-250, 1944. Herold, C. L., Geology of the Salinas quadrangle, California : Geol. Soc. America Proc. 1935, p. 337 (abst.) 1936. Herold, C. L., Distribution of Eocene rocks in the Santa Lucia Mountains, Cali- fcrnia: Am. Assoc. Petroleum Geologists Bull. 20, pp. 491-494, 1936. 22 Schombel, L. P., Geology of the Soledad quadrangle, California: unpublished M.A. thesis. University of California, 1940. Schombel, L. P., Soledad quadrangle: California Div. Mines Bull. 118, pp. 467-470, 1943. Nickell, P. A., Geology of the Soledad quadrangle: Pan Am. Geol., vol. 54, no. 2, p. 157 (abst), 1930. 23 Wilson, Ivan P., Geology of the San Benito quadrangle, California: California Div. Mines Rept. 39, pp. 183-270, 1943. Wilson, Ivan P., Geology of the San Benito quadrangle, California: PhD. thesis, University of California, 1941. GEOLOGY ALLEN 17 areas. Unpublislied work has recently been under way in the Morgan Hill and New Almaden quadrangles by Gilbert and his students ; ^* and Beard, during the summers of 1938, 1940, and 1941 worked in the western half of the San Juan Bautista area. An abstract of his thesis -^ indicates that some attention was paid to the structure and stratigraphy of the area, but the main contribution was to the history of the drainage of the Pajaro River, and the "Elkhorn Valley," which was recognized as being a main drainage channel during the Pleistocene. Several fairly extensive fossil collections have been made from the Tertiary rocks in the San Juan Bautista quadrangle. The most impor- tant are those by Martin,^^ Schenck,^'^ and Loel and Corey.^^ Grant and Gale -^ also list several localities within the area. A collection made by Arnold and Hannibal,^^ now in the Stanford University collection, was also examined. STRATIGRAPHY Introduction The San Juan Bautista quadrangle is divided into two stratigraphic provinces. The Santa Cruz Range province has a Franciscan (Upper Jurassic) basement, overlain by a thick sequence of Monterey (middle Miocene) sandstones and diatomaceous shales. The Gabilan Range province has a granitic basement, and is overlain by a much thinner series of San Lorenzo (Oligocene) sandstones and shales and Vaqueros and later (lower and middle Miocene) sediments and volcanics. Both regions are overlapped by Pliocene and Pleistocene rocks. The two provinces, separated by the San Andreas fault, are thus represented by separate stratigraphic columns, which are equivalent, in part, only during the late Pliocene and Quaternary. Sur Series and Gabilan Limestone (Pre-Santa Lucia Granite) The Gabilan limestone and the associated metaniorphics are the oldest rocks exposed in the region. The limestone was named by Becker ^^ from the exposures appearing in Gabilan Peak, in the southeast corner of the quadrangle. It occurs as roof pendants in the Santa Lucia granite in several elongated discontinuous bands up to 2 miles in length, and in a large number of isolated lenses and patches. =^^ Gilbert, C. M., personal communication, 1944. 25 Beard, C. N., Drainage development in the vicinity of Monterey Bay, California ; PhD. thesis (abst.), University of Illinois, 1941. 2« Martin, Bruce, The Pliocene of middle and northern California : Univ. California, Bull. Dept. Geol. Sci., vol. 9, no. 15, pp. 215-259, 1916. Martin, Bruce, faunal relations of the upper Neocene in the Sargent oil fields, California: Geol. Soc. America Bull., vol. 24, p. 129 (abst.), 1913. 2T Schenck, H. G., Unpublished lists of fossils from the San Juan Bautista, Pine- cate and Vaqueros formations west of San Juan Bautista, California ; Stanford Uni- versity. 28 Loel, W., and Corey, W. H., The Vaqueros formation, lower Miocene of Cali- fornia, Paleontology I: Univ. California Bull. Dept. Geol. Sci., vol. 22, pp. 31-410, 1932. 28 Grant, U. S., and Gale, H. R., Catalogue of the marine Pliocene and Pleistocene mollusca of California: San Diego Soc. Nat. Hist., Mem. 1, 1036 pp., 1931. 30 Arnold, Ralph, and Hannibal, H., The marine Tertiary stratigraphy of the north Pacific Coast of America: Philcs. Soc, Proc. 52, pp. 559-605, 1913. SI Becker, G. P., Geology of the quicksilver deposits of the Pacific Slope : U. S. Geol. Survey Mon. 13, p. ISl, 188S. 2 — 51298 18 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 AGE FORMATION | COLUMN THICK DESCRIPTION Recent Alluvium \'.°''^.-9':.9y. 0-200' Silts , sands and clays U. Pleis. Terraces |. 0-100' Chiefly granitic gravels Middle (?) Pleisto- cene Aromas red sands 1: •.■•;■.•;.';•.■;; - 0-800' Red to yellow , friable, well-sorted, cross-bedded sands. Upper and middle Pliocene Purisimo formation N 004, 2000' + Fossiliferous grovels, sands and a few silts and clays. ...... 900 O '--~-~',~:' .'r^ ^■•>J^^-l,-\y-\jtj-,. ^ «•«••«.. . ot in contact Middle (?) and lower Miocene Sandstone 0-1000' Andesite porphyry, and agglomerate , with some interbedded arkosic sand- stones and black flow at base. Volconic -• -.**.*.*.'..'■'."■ ,',•-*. grou p "Basalt" >.-•.-»'«' *- ^ «- milUlllllMHifRi Vaqueros group Sandstone 0-800" Torrentially bedded red coarse conglomerate ond breccia, with limestone boulders. V- 1 * . •*.'-" '.* '. r 150-400' Coarse, fossiliferous sandstone. Oligocene San Lorenzo group o'o» • 1000' + Massive, poorly bedded, cavernous-weathering yellow arkosic sandstone. Few fossils. rr=: rTTTT .7" 1500' + Buff- colored , medium-to fine-grained sandstone and sandy shale. Fossiliferous. ■ - - ■ * ■..■-*•.-'■ U- - — ^-r- Pre- Fronciscon Santa Lucia quartz diorite N / \ / \ / \ / \ / Biotite-quortz diorite aplite , etc. Sur series a Gabilon Is. 2000'+ Quartzite , schist , and limestone. Fig. 2. Stratigraphic column in the Gabilan Range GEOLOGY — ALLEN 19 AGE FORMATION COLUMN THICK. DESCRIPTION Recent Alluvium / ;:o;.-:-o.-. :•. o;.-. .-•.»>•• .,0-200' Clays, silts and gravels. O ."o" ••»o'0.-_3^ U. Pleis. Terroces , O t» O • • o « e '• \0-50' Gravels. Upper and middle Pliocene Puri sima formati on 7000- 10,000' Cross-bedded, gypsiferous, continental gravels , grits and sonds. Marine, higtily fossil iferous gravels, sands and silts. Basal conglomerates. . ; . ... ^^-^J\J *^-»/^'^ ^ '- o o o • » o„o o o o o o « o o o o <» O o Upper and middle Miocene Monterey group 2000- 3000' Diotomoceous and siliceous shales. Clay-shale. Limestone lenses and sili- ceous shale interbed. Arkosic sandstones and grits. __ _ N 1 ^-^^r=-r-^i=-= ***** *** Upper Jurassic Franciscan group Fault contac t 5000' Well indurated dork- colored arkosic sand- stones , shales , and some conglomerates. Rodi ola ri on cherts. Limestones. .'•.'■',• • • ."_^-i^ ." «9 o' 9 •« .O O \ «- *- i-- *- 0-1600' Altered and amygdaloidal basalts . 3000' Basaltic agglomerates and tuffs. Serpentine intrusions along faults. Fig. 3. Stratigraphic column in the Santa Cruz Range 20 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 The Gabilan limestone is a part of the Sur series ^^ of qiiartzites, mica schists, and hornfels, in which it generally occurs. The mapping of the contacts of the Sur series and the granite in the rugged Gabilan Range was not considered to be feasible within the time available, as detailed work is necessary to differentiate it from the granite due to the similarity of appearance of the soil and outcrop. It can be assumed that consider- able amounts of Sur series rocfe are associated with many of the numerous mapped outcrops of Gabilan limestone. One 600-foot section of meta- morphics with enclosed limestone is exposed in higliAvay cuts on the San Juan grade 1 mile south of the summit ; a 4000-foot section appears along the old road up Steinbach Canyon north of Gabilan Peak. A section 1-| miles west of Gabilan School across a roof pendant in the granite showed : 200' fine-grained mica schist 250' limestone 50' light-colored, fine-grained quartzite 300' limestone 180' pure well-bedded quartzite The Gabilan crystalline limestone varies from a few to many hun- dreds of feet in thickness. Attitudes in the metamorphics are nearly always very steep, with general easterly trends. The limestone varies in color from a dark gray or even black to a pure white ; in texture, from dense fine-grained to coarseh^ crystalline ; in composition, from a nearly pure limestone to a low-grade dolomite or to a rock high in barium content, or high in graphitic constituents. It generally has a low silica content, in spite of its association with siliceous sediments. The limestone generally shows a faint banding, and sometimes bed- ding is well developed. In places it is closely interfingered and inter- bedded with quartzite and schist in beds up to 10 feet thick. One section on Gabilan Peak showed a gradation from quartzite into slate and schist and then into pure crystalline limestone. A 700-gram sample of a graphitic phase from Gabilan Peak was dis- solved in cold hydrochloric acid, separated with bromoform and magnet, and studied under the microscope. The results are as follows (with the exception of the last column, percentages are of the whole sample) : 95% (6G5g.) / 3.57% (25g.) graphite [ altered hiotite 75% calcite 10.86% flOg.) lights I cordierite 15% I [chlorite? 7% 5% (35.627g.) )o.0835% (0.27g.) f diopside 85% insoluble j non-mag. heavies \ wollastonite 8% I [ diallage ±— 5% 10.005% (Tr.) f diopside 70% \ magnetic heavies | hedenbergite 30% A few grains of hematite, hypersthene, and fluorite were also observed. On the north side of Gabilan Peak black elongated tubular segrega- tions of graphite weather out to suggest the ' ' round crinoid stems ' ' first noted by Smith.^^ These structures are up to 1 inch in diameter and •■'2 Trask, P. D., Geology of the Point Sur quadrangle, California : Univ. California, Bull. Dept. Geol. Sci., vol. 16. p. 134, 1926. ^ Smith, .T. P., The geologic formations of California : California Min. Bur., Bull. 72, p. 20, 1910. GEOLOGY — ALLEN 21 several inches long.^'* Flat lenticular bodies which suggest algal growths are not uncommonly found. Wherever good exposures occur, the limestone appears to be intruded by granite with very slight contact effect beyond recrystallization. Com- monly long apophyses of granite may penetrate for many feet along bedding planes, or cut abruptly across the structure. In places numerous veins of secondary calcite appear, or the limestone is brecciated and recemented either by lime or by yellow chalcedony. One of the larger lenses of dolomitic limestone is now being mined on the southern edge of the quadrangle by the Permanente Metals Corpo- ration, for the production of magnesium metal, Santa Lucia Granite (Pre- Franciscan) Intrusive into the Sur series is the Santa Lucia granite,^^ which composes most of the Gabilan Range within the area mapped. The gran- ite is in fault contact with the lower Tertiary rocks southwest of San Juan Bautista, and is overlain by the Pleistocene Aromas sands and terrace gravels in the central southern half of the quadrangle. In the area between Dunbarton and Langley School it is exposed through the sands in a number of small irregular areas by recent faulting and by erosion. Along the west side of the San Andreas fault between San Juan Bautista and Pajaro Canyon granitoid rocks also appear beneath the Tertiary and later sediments. These are more basic in nature than the granite farther south, and have been somewhat metamorphosed. They were called the Anzar metamorphics by Kerr and Schenck,^^ who believed them to be a metamorphic facies of the basic phase of the Santa Lucia granite, probably produced by serpentinization. The dark rock at Logan quarry was called an ultrabasic or basic diorite by Reid,^'^ but the thin sections examined all showed small amounts (5 to 10 percent) of quartz, with equal amounts of hornblende and saussuritized andesine feldspar. The rock has been metamorphosed, and some of the hornblende is poikiloblastic around feldspar fragments, and the quartz shows sutured structures. There are minor amounts of iron ores, and much chloritic material, zoisite, and secondary calcite. Lighter colored and less altered phases from farther south in the Gabilan Range show as much as 30 percent quartz with oligoclase and biotite, a fairly normal quartz diorite. An aplitic dike from south of Dunbarton contained zoned albite (50 percent), quartz (30 percent), both biotite and muscovite, and some garnet which is resorbed and has developed reaction rims of biotite. 8^ "I have submitted them (specimens from the Gabilan limestone) to various paleontologists and find agreement on two points — that the specimens are of organic origin and that they cannot be crinoidal. No agreement was found beyond that. Some paleontologists suggest an algal origin, comparing the specimens to altered Girvanella ; others suggest sponges, corals, or filled borings. There seems to be no fine structure left in the crystalline material that would give any real clue to the original nature of the fossil. About all that can be said is that at least some of them were cylindrical in form and must have been cylindrical solids or hollow tubular objects. No basis for an estimate of the age of the beds is afforded." Personal communicatiori from John B. Reeside, Jr., U. S. Geological Survey, April 9, 1945. 35 Lawson, A. C, The geology of Carmelo Bay : Univ. California, Bull. Dept. Geol. Sci., vol. 1, p. 6, 1893. =« Kerr, P. F , and Schenck, H. G., Active thrust faults in San Benito County, California: Geol. Soc. America Bull. 36, p. 471, 1925. ^ Reid, J. A., The igneous rocks near Pajaro : Univ. California, Bull. Dept. Geol. Sci., voL 3, p. 190, 1902. 22 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 5 MILLIMETERS Fig. 4. Santa Lucia granitic rocks (plane polarized light). A, Highway cut 2 miles south of Chittenden Junction (41-A). Dark-colored hornblende-quartz diorite. Poikilitic hornblende, partially kaolinized basic labradorite, sutured quartz, and iron ores. B, Hill S96', just south of Vergeles fault, \\ miles northeast of Langley School (60). Quartz diorite. Crushed and slightly kaolinized oligoclase, strained and sutured quartz, and biotite. C, In canyon J-mi!e south of Hill 555', J-mile west of highway, 2 miles south of Dunbarton Junction (50). Garnetiferous aplite dike. Albite, quartz, biotite, and garnet with biotite rim. Franciscan Group (Upper Jurassic) General Character The Franciscan group of western California was first subdivided by Lawson,^^ and the sandstones and cherts of the group were studied in detail by Davis. ^'^ Eocks of the group occupy a northwest-trending belt 3 miles wide, in the northeast portion of the quadrangle, which is bounded on the northeast by the Carnadero and on the southwest by the Sargent faults, being in contact with rocks of Monterey (middle Miocene) age on either side. Structurally, this belt is an anticline, with a core of basaltic agglomerate overlain on both sides by steeply dipping sediments. Stratigraphically, there is a minimum of 3000 feet of agglomerate, over- lain on the north flank of the fold by a lenticular body of basalt up to 1600 feet thick, followed by upwards of 5000 feet of arkosic sandstones and shales with lenses of limestone and black radiolarian cherts near the base on both sides of the fold. Red radiolarian cherts appear higher <«.... ^Lawson, A. C, San Francisco folio: U. S. Geol. Survey, Geol. Atlas, no. 193, 1914. 3» Davis, E. F., The Franciscan sandstone: Univ. California, Bull. Dept. Geol. Sci., vol. 11, pp. 1-44, 1918. .„ ,, ^■'^^"^i?' ^- F-' '^^^ radiolarian cherts of the Franciscan group : Univ. California, Bull. Dept. Geol. Sci., vol. 11, pp. 235-432, 1918. GEOLOGY — ALLEN 23 in the section. Serpentine appears adjacent to the boundary faults on both sides. Silica-carbonate rock, and giaucophane and actinolite schists as found in other Franciscan areas, do not appear in the San Juan Bautista quadrangle. To the southeast, the Franciscan belt is overlapped by Pliocene sediments and Quaternary terraces and alluvium. Neither the base nor the top of the group is exposed. Small serpentine bodies surrounded by Pliocene gravels appear at four points just north of La Brea Creek, and in a northern spur of Lomerias Muertas. South of Anzar Lake there is a small area which is scattered with giant boulders and fragments of red and buff-colored radiolarian chert up to 25 feet in diameter, and some pieces of serpentinous rock, appar- ently resting upon granitic rocks and beneath Aromas sands. This may represent a remnant of Franciscan, but it is more likely that it is derived bj^ late Tertiary landsliding from the Franciscan highlands across the San Andreas fault to the northeast. The characteristic "knobby" topography exhibited in other Fran- ciscan areas is present only in or near the serpentine exposures ; the agglomerates and sandstones as a rule erode to form steep rounded and smooth slopes, supporting grass on the southern and dense chaparral, manzanita, and liveoak on the northern slopes. Agglomerate and Tuff Member The Franciscan agglomerate and tuif member, which covers about 7 square miles in the center of the belt and forms the highest ridges, is a remarkably monotonous assemblage of unsorted basaltic pyroclastic material at least 3000 feet thick. Bedding and attitudes are difficult to determine with certainty, even in the good outcrops along the new road east of Bodfish Creek or in the narrow canyon farther east. In one or two areas the less resistant tuffaceous layers do affect the physiography so that tentative attitudes were obtained. A few thin flows of dense amygdaloidal basalt are included in the pyroclastic member, but it is mostly composed of angular to subangular basalt fragments varying in size from a few millimeters to over 1 foot, with such poor sorting that all sizes may be found in a single piece. Fresh surfaces are dark green, saussuritization having equally affected the basalt fragments and the tuffaceous matrix, and the rock weathers to a dark yellow or red. Quartz veination is sometimes present, but not common. Jointing is widely spaced and highly irregular. In some areas near faults the rocks have been rendered schistose, and platy structures and serpentinized slickensides appear. The tuffaceous beds, which are subordinate in amount, not uncommonly contain frag- ments and thin discontinuous lenses of limey chert, bands of silicified shale, and foraminiferal limestone, suggesting their submarine origin. Along the northern edge of the quadrangle where the agglomerate has been eroded by the youthful tributaries of Bodfish Creek, it stands out in prominent cliffs, although elsewhere it is usually expressed by gently rounded hills and knobs, grassy and open on their southern, and covered with dense chaparral on their northern slopes. Outcrops most commonly occur as rounded boulders with knobby surfaces, lying on the crests of the ridges. 24 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 5 MILLIMETERS Fig. 5. Franciscan volcanic rocks (plane polarized light). A, A quarter of a mile south of Hill 1749', 2 miles northwest of Castro Flats (93). Altered basaltic amygdaloid. Amygdules filled with quartz, calcite, zeolite, and chlorite, in an inter- sertal base of saussuritized plagioclase laths and glomeroporphyritic augite, in equal amounts, and devitrified glass. Quartz occurs in amygdules, in phenocrysts, and as fillings of dictytaxitic openings. B, On road up gulch at forks |-mile south of north edge of map and 2 miles east of Bodfish Creek. Elevation 700' (94). Green basaltic agglomerate. Basaltic fragments have glomeroporphyritic altered plagioclase and augite in an intersertal groundmass of saussuritized plagioclase, augite, iron ores, and altered basaltic glass. Interstitial material largely chlorite, some veinlets of chrysolite. C, On ridge west of Babbs Canyon, elevation 1200' (71). Basalt. Laths of andesine Avith intersertal augite, large amounts of iron ores as euhedral and subhedral grains and crack fillings, and microcrystalline and in large part chloritized groundmass. A few quartz grains always associated with and usually surrounded by chlorite. Basalt Member The agglomerate is overlain on the north flank of the Franciscan anticline by a series of basalt flows with minor amounts of interbedded tufi's and sediments. They have a maximum thickness of about 1600 feet, and pinch out both to the east and west. Outcrops are poor, and the contact of the basalt with the agglomerate is difficult to map, as the basalt has a fine blocky cleavage, and the fragments in the soil are identical to those in the agglomerate areas. Several small lenses of limestone and red chert appear within the member. On the ridge just west of Babb's Canyon 950 feet of basalt has a north-dipping section as follows : Contact with sandstone and shale on the north 150' basalt flows 25' green schistose agglomerate 5-10' chert lenses 800' basalt flows Contact with agglomerate on the south The west end of the basalt lens is offset to the north by the Castro fault about half a mile. A small area of basalt appears in a similar strati- graphic position northeast of Castro Flats.' GEOLOGY ALLEN 25 In thin section, the basalt is seen to have an intersertal texture, with laths of andesine and augite, and grains of primary iron ores in a thoroughly devitrified glassy groundmass. Quartz, chlorite, zoisite, and iron ores are secondary, the plagioclase being more or less completely saussuritized. Sedimentary Members The basalt and agglomerate members are overlain on both sides of the Franciscan anticline by as much as 5000 feet of dark gray-green arkosic sandstones and lesser amounts of shale, interbedded at or near the contact with numerous lenses of limestone and intercalated black chert. These have an areal extent slightly greater than that of the agglomerate. Limestone lenses in the lower 800 feet of the sedimentary sequence are from a few feet to over 200 feet thick, and from a few tens of feet to over 1 mile in length. The smaller lenses are discontinuous, but reappear from place to place along the strike of the sediments. They tend to be arranged in groups of parallel lenses, without wide lateral extent, suggesting that they were deposited in a narrow channel or upon a reef. The limestone is usually gray in color, but varies from pure white to brown, gray, and nearly black. It is usually well bedded, and inter- calated with thin shale partings and with black chert, the latter at places making up 50 percent or more of the rock. At one place the chert bands averaged from 3 to 6 inches thick, the limestone bands from 1 to 12 inches. Broken chert fragments are commonly found imbedded in limestone. Weathered surfaces of limestone at a few places showed small structures which may have been large Foraminif era. Stylolites have been noted. At least 1000 feet above the base of the sedimentary member there is a zone occupied by numerous and in places quite thick lenses of red, and to a lesser extent green, radiolarian chert, similar to those which have been described by Davis.^^ Red chert appears in a number of bodies up to 100 feet thick in the ridges just west of Castro Flats and on the ridge east of the Castro fault at the north edge of the quadrangle. From the amount of chert in the stream beds both east and west of Babbs Canyon, there must be large masses in the relatively inaccessible brush-covered northern slopes of the main ridge. East of Castro Flats, bedded green chert over- lies a conglomerate composed largely of black and white quartzite pebbles from a quarter to 1^ inches in diameter. These cherts are well bedded, the individual lenses being up to 3 inches thick, interbedded with reddish shale. Manganese stain is commonly found along the blocky joint frac- tures of the cherts. It is probable that both the cherts and the limestones are closely related to the preceding submarine volcanism.^^ The Franciscan sandstones are dense, usually indurated, and dark green to gray when fresh, weathering buff and red. They are generally fairly massive, although thin shaly interbeds appear at some places. A thin-bedded gray sandstone with plant remains occurs in one gulch half a mile west of Castro Flats, underlying a medium to coarse-grained ^0 Davis, B. F., op. clt. vol. 11, pp. 235-432, 1918. *i Taliaferro, N. L., The lelation of volcanism to diatomaceous anrl associated siliceous sediments: Univ. California Bull., Dept. Geol. Sci., vol. 23, pp. 1-56, 1933. Kania, J. E. A., Precipitation of limestone by .submarine vents, fumaroles, and lava: Am. Jour. Sci., 5th ser., vol. IS. pp. 347-359, 1929. 26 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 sandstone which encloses angular shale fragments up to 1 inch in diameter. Under the microscope the sandstone shows numerous cross sections of Foraminifera, Radiolaria, and Bryozoa, identified by Dr. B. L. Clark. A mile farther west both massive and thin-bedded sandstones appear, some of them carbonaceous, some with white mica developed on cleavages, simulating bedding. Conglomerates were noted at a few places east of Castro Flats and northwest of Sargent oil field. Dark-colored quartzite is the most com- mon pebble constituent. Shale is subordinate in amount to sandstone, but is fairly common. It is usually thin-bedded, hard, and occasionally slaty, sometimes with a cleavage developed at a low angle to the bedding planes. It is black or gray, weathering to yellow or reddish. The saddles in the ridges on the north side of the main Franciscan ridge at about 1200 feet elevation are developed in a shale member in the predominantly sandy series. On the north-trending ridge just south of the midpoint of the edge of the map the shale is schistose and sericitized, with a golden sheen on the paper- thin flakes. Serpentine Serpentine masses are found squeezed up by cold intrusion along the boundary faults of the Franciscan area, as well as into Pliocene rocks north of La Brea Creek. They are also found in sill-like intrusions in the Franciscan sediments near these faults. Although originally peri- dotite, they are now found in all degrees of alteration to a greenish to grayish and occasionally dark brown to black, much sheared and slicken- sided serpentine. In places small cores of less completely altered olivine with diallage phenocrysts may be seen in the center of joint blocks whose borders have been minutely veined with chrysotile, usually less than an eighth of an inch in thickness. Chromite grains are present but not common. At a few places massive unsheared serpentine appears. It is quite hard, has a dull waxy lustre, weathers to a purplish gray, and shows brown bastite pseudomorphs. Age of the Franciscan The evidence concerning the age of the Franciscan has been recently reviewed by Taliaferro, ■*- who states that it is Upper Jurassic, equivalent to the Tithonian as defined by Muller.^'"^ The abundance of volcanic material, limestones, and cherts in the Franciscan of the San Juan Bautista quadrangle indicates that the posi- tion of the group in the series as a whole is in the "second stage, upper Franciscan," of Taliaferro,'*^ possibly extending into the lower portion of the ' ' third stage. ' ' •■2 Taliaferro, N. Tj., Franciscan-Knoxville problem: Am. Assoc. Petroleum Geo- logists Bull., vol. 27, pp. 190-195, 1943. «Muller, S. W., Standard of the Jurassic: Geol. Soc. America Bull., vol. 52, pp. 1427-44, 1941. ** Taliaferro, N. L., Geologic history and .structure of the Central Coast Ranges of California: California Div. Mines Bull. 118, p. 126, 1943. Taliaferro, N. L.. Genesis of the- manganese deposits of the Coast Ranges of California: California Div. Mines Bull. 125, p. 223, 1943. GEOLOGY ALLEN 27 San Lorenzo Group (Oligocene) General Character The San Lorenzo rocks in the San Juan Bautista quadrangle were originally described by Kerr and Schenck '^^ and were divided into two formations, the San Juan Bautista and the Pinecate. These occupy large portions of the Tertiary area west and southwest of the town of San Juan Bautista as far as Pinecate Peak. Both formations are largely composed of sandstone, but were difPerentiated on the basis of presence or absence of fossils and topographic expression. The contact between them is reported to be disconf ormable, but if so, it is a minor and perhaps local break and was not observed in the present study. Both formations are also disturbed and broken by thrust and cross faults, the strike of the beds in some blocks being at right angles to that in other adjacent blocks. Repetition by thrusting from the southwest occurs not once, but two and three times. It may be that a very detailed survey would permit a line of contact to be drawn, but it was not done during the present survey. San Juan Bautista Formation The San Juan Bautista formation consists of as much as 1500 feet of poorly bedded, fine-grained, fossiliferous, argillaceous and calcareous sandstones, carbonaceous grits often containing numerous wood frag- ments, and shales. The sandstones are blue and indurated when fresh, but become soft, friable and buff-colored under the influence of weathering. The base of the formation where it rests upon granite lies 1 mile northwest of the town of San Juan Bautista. Thicknesses in several measured sections ranged from 1500 to 1800 feet. The low hills west of San Juan Bautista and the grassy lower slopes of the main ridge running west to Pinecate Peak are made up of the rocks belonging to the formation, the cliffed upper portion of the ridge is the overlying Pinecate sandstone, and the ridge is capped with Vaqueros red beds. Pinecate Formation The Pinecate formation consists of about 1000 feet of massive but sometimes crossbedded quartzose sandstone, in places pebbly or contain- ing lenses of conglomerate. It varies from medium to coarse grained, the fragments being usually sharp and angular. It weathers to a pale buff color, and stands up in rugged cliffs and giant blocks, in contrast to the subdued expression of the underlying San Juan Bautista formation. Solution during weathering of the calcareous material in the sandstone, and redeposition at the surface has produced a "case-hardening" which has resulted in hollowed-out caverns that are characteristic of the forma- tion. Calcite and quartz veins are not uncommon along joint planes. Age and Correlation Fossils were collected by the Stanford University Summer Camp from 23 localities, mostly in the San Juan Bautista formation, and were studied by Dr. H. G. Schenck. This list has never been published, but is included in the author's thesis on the San Juan Bautista quad- rangle, on file at the University of California, Berkeley. According to *5Kerr, P. P., and Schenck, H. G., op. cit., pp. 471-472, 1925. 28 SAN JUAN BAUTISTA QUADRANGLE [BuU. 133 Schenck/^ some of those fossils which establish the age and marine origin of the San Juan Bautista formation are Bruclarkia gravida (Gabb), Fusinus chehalisensis Weaver, Acila muta Clark, Epitonium wagneri Durham, and Modiolus kirJcerensis Clark. Fossils from one locality in the usually barren Pinecate formation were chiefly Spisula mulinaformis "Wagner and Schilling and Antigona matheivsoni (Gabb). In the same paper it is stated that ' ' there seems to be a close relationship between the San Juan Bautista and the San Emigdio formations and between the Pinecate and the Pleito formations in California." In 1936, Schenck and Kleinpell ^'^ state that the San Juan Bautista formation and ques- tionably the Pinecate formation are believed on the basis of molluscan evidence to be of Refugian age. Vaqueros Group (Lower Miocene) General Character The Vaqueros group, first given the name ' ' Vaquero sandstone ' ' by Hamlin,^^ consists in the San Juan Bautista quadrangle, of fossiliferous sandstones and red beds up to 1800 feet in thickness, but usually much less, which form the highest points of the rolling hills south and west of the town of San Juan Bautista. Tliey conformably overlie the Pine- cate formation, the contact being determined only by the lowest horizon containing Vaqueros fossils, and are overlain unconformably by the lavas and agglomerates of the volcanic group. Vaqueros Sandstone The Vaqueros sandstone, found beneath the red beds and inter- bedded with them, varies from about 100 to possibly as much as 800 feet in thiclvuess. It is a fossiliferous, coarse arkosic and calcareous sand- stone, yellow to white in color and quite friable on weathered surfaces. It contains a few interbedded shaly members, and some conglomerate made up of angular to sub-rounded pebbles of granite, limestone, and schist in a buff-colored sandy matrix. Another common type is a loose, pale gray, sugary sandstone. Red Beds The red beds of Kerr and Schenck ^^ conformably overlie and are at places interbedded with the Vaqueros sandstone. They consist of a series of reddish continental breccias and conglomerates up to 1000 feet in thickness, which are well exposed at several places along the San Juan grade, the best exposures being about 3^ miles southwest of the town. The pebbles and boulders are predominantly Gabilan limestone, ranging in size from a few millimeters to over 4 feet in diameter, with lesser amounts of gneiss, granite, schist, quartzite, and sandstone in a reddish clayey and sandy matrix. In highway cuts, which are the only good exposures, they show a rude stratification and cross-bedding, which to Kerr and Schenck,^*^ indicate ' ' a conglomerate laid down under torren- •"=Kerr, P. F., and Schenck, H. G., op. cit., pp. 471-472, 1925. « Schenck, H. G., and Kleinpell, R. M., Refugian stage of Pacific Coast Tertiary : Am. Assoc. Petroleum Geologists Bull., vol. 20, p. 161, 1936. ^8 Hamlin, Homer, V^ater resources of the Salinas Valley, California: U. S. Geol. Survey, Water-Supply Paper 89, pp. 14, 1904. J" Kerr, P. P., and Schenck, H. G., op. cit., p. 472, 1925. ^"Op. cit. p. 473, 1925. GEOLOGY ALLEN 29 tial eo7iditions in an arid climate" in a stream channel. The breccia is interbedded at a number of places with fossiliferous arkosic sand- stones, and while its coarse character indicates a terrestrial origin and extremely rapid accumulation, the apparent distribution in a "channel" from the Gabilan Range is considered to be coincidental and due only to later faulting and erosion. The red beds are believed by the writer to be due to sea-cliff erosion along a shoreline, or possibly fanglomerate accumulation resulting from uplift of the Gabilan Range, probably by initial movements along the Vergeles fault. The presence of sandstone interbedded with numerous agglomerate layers in the overlying volcanic group seems to corroborate the idea that the area of deposition was never far above sea level, while the adjacent Gabilan Range stood high enough to contribute very coarse debris. The red beds are characterized by rounded grassy slopes, support- ing sparse sagebrush on only a few steep northerly and easterly slopes. Lines of limestone boulders and "grass-dips" are the only indications' of structure over much of its area. Columnar Sections Good exposures at a few places permitted measurement of sections which give an idea of the variation in character wdthin the red beds, and their relationship with the adjacent formational units. Above the Gabilan School on the east side of San Juan Creek : Contact with overlying lava 20' coarse, yellow arkosic sandstone. 30' fine, dense, gray sandstone. 1000' coarse arkosic sandstone with three thick layers of limestone breccia, with boulders averaging 6-8 inches in diameter. Saddle east of Hill 1210', 1 miles west of summit of San Juan grade : Contact with overlying lava 120' massive, medium-grained, buif-colored sandstone, with scattered pebbles, lenses, and beds of conglomerate, one horizon composed almost entirely of angular lava fragments. 40' cobble conglomerate composed of boulders and pebbles of lava, sandstone, and limestone, up to 6 inches in diameter. 20' massive medium-grained, buff-colored arkosic sandstone. 50' sandstone and conglomerate with well-rounded and polished pebbles. 10' medium-grained, friable, lemon-yellow sandstone. 10' soft friable buff-colored sandstone. 20' lenses of limestone breccia intercalated with soft calcareous sand- stone. 60' soft friable buff-colored sandstone. 20' soft friable white calcareous sandstone. 500' plus, limestone breccia red beds. South side of Hill 1350', west of San Juan grade summit : 175' limestone breccia and gravel to top of hill. 40' giant conglomerate, composed of boulders of limestone, lava, quartzite, and granite, up to 2 feet diameter, all well rounded and polished. 8' gray sandstone and shale. 25' breccia of angular fragments of granite (70%), lava (25%), and schist (5%), in a granular arkosic matrix. Contact with underlying sandstones 30 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Highway cut on San Juan grade 3 miles west of town : 15' red clays and cross-bedded gravels with limestone boulders. 20' alternating yellow and gray arkosic sandstone. 3' pebble conglomerate and breccia. 5' medium-grained arkosic sandstone. 8' sandstone and thin-bedded shale. 2' conglomerate with equal amounts of limestone and sandstone pebbles. 30' alternating sandstone, and conglomerates with limestone pebbles and an earthy matrix. 60' massive yellow arkosic sandstone. Age and Correlation Fossils were collected in 1924 by the Stanford Summer Camp from 3 localities,^^ and Loel and Corey ^^ list fossils from 4 localities in the quadrangle. In the range table given by Loel and Corey,*^^ Echinarachnius, Ostrea vaquerosensis, and Turritella inezana hicarmd limit the fauna to the upper Vaqueros, but below the ' ' uppermost ' ' Vaqueros. According to Kleinpell,^^ the red beds are ''of possible Saucesian age, the Vaqueros sandstone definitely Zemorrian." Volcanic Group (Lower or Middle Miocene) General Character The volcanic group consists of a series of flows of andesite, rhyolite, and thick beds of agglomerate, with interbedded arkosic sandstones, aggregating in places over 1000 feet in thickness. Thej^ occur in an east-west belt for 8 miles along the southern crest of the range of hills southwest of San Juan Bautista, where they parallel and over most of its course adjoin the Vergeles fault, being in contact with Santa Lucia granite and Sur series on the south. The volcanics rest upon both red beds and Vaqueros sandstone, and may overlap upon the Pinecate, but no angular discordance was noted at any of the contacts. Thej^ are overlain by more than 500 feet of coarse arkosic sandstone which is litho- logically similar to the lower Monterey sandstones in the northern portion of the quadrangle. At the western end of the belt of volcanics, south of Pinecate Peak, they are overlapped by the Pleistocene Aromas sands. The total areal extent of the volcanics in the northern Gabilan Range is very little greater than the area mapped, and undoubted centers of eruption, most of them close to the Vergeles fault, were noted in several localities. On the crest of the highest ridge 2 miles due south of San Juan Bautista, an irregular outcrop of andesite is intrusive through the thick red beds. The outcrop is irregular, forming a strip over half a mile long. At several places it is bounded by steep, outward-dipping grooved surfaces with sinuous contours; near the southern margin an intrusive breccia is developed, with angular fragments of lava imbedded in a white glassy fijie-grained matrix along with rounded pebbles of limestone and quartzite derived from the red beds. Internal structures are prominent, the flow planes being steep or vertical throughout. 61 Stanford Geological Survey notes, 1924. 52 Loel, W., and Corey, "W. H., The Vaqueros formation, lower Miocene of Cali- fornia: Univ. California Bull., Dept. Geol. Sci., vol. 22, pp. 124-125, 134. 1932. MQp. cit, p. 134, 1932. ^ Kleinpell, R. M. Miocene stratigraphy of California : p. 108, American Assoc, of Petroleum Geologists, 1938. GEOLOGY ALLEN 31 The lavas var}^ in attitude from Iioriznntal to vertical, but generally dip at angles greater than 40 degrees. They are duplicated at places by thrusting along a branch of the Vergele.s fault. One and a half miles south of Pineeate Peak they form both flanks of a narrow anticlinal ridge. Individual flows are generally quite thin, usually 50 feet or less, although one or two flows up to 120 feet thick were noted. On the north side of the main ridge only thin tiows of lava appear ; apparently, the volcanics thin rapidly to the north. Columnar Sections Several sections through the volcanic group were measured at favor- able localities, and these best give an idea of the variations encountered, and the extremely lenticular nature of the flows. Section through Hill 851', 2 miles south of Pineeate Peak : 25' plus massive soft fria))le gritty samlstone. thin bed of flow breccia or agglomerate. massive cemented gritty sandstone and poorly cemented sand- stone, in beds 10 feet thick and 20 feet apart, white biotite andesite. variegated and banded gray and lavender porphyritic andesite. glassy lavender andesite porphyry, dark gray andesite porphyry, white biotite andesite. variegated andesite porphyry similar to 5. dark andesite similar to 7. white andesite similar to 4. dark porphyritic rhyolite. white andesite similar to 4 and 11. coarse tuffaceous sandstone interbed. white andesite. alternating massive (up to 10 feet) and thin-bedded coarse sand- stone and tuffaceous breccia, white andesite. coarse-grained tuffaceous sandstone, andesitic agglomerate, dense greenish andesite. andesitic agglomerate, dense black glassy "basalt." coarse tuffaceous sandstone, light-colored andesite. contact with massive sandstones (Vaqueros?). Section through Hill 951', half a mile southeast of above section : 1. 300' plus soft buff-colored massive sandstone. massive andesite and andesite agglomerate, coarse tuffaceous sandstone and some agglomerate beds, dense black glassy "basalt." light-colored andesite. contact with sandstone (Vaqueros?). Section through Hill 1210', 1 mile west of summit of San Juan grade : massive and thin beds of andesite, breccia, and agglomerate. • cross-bedded coarse arkosic sandstone. white glassy andesite. massive coarse-grained sandstone. light-colored andesite. giant conglomerate, boulders well rounded, up to 3 feet in diameter. dense brittle dark-colored andesite. fine-grained sandstone, contact with red beds. 1. 25' 2. 2' 3. 150' 4. 20' 5. 14' 6. 14' 7. 77' 8. 35' 9. 56' 10. 22' 11. 42' 12. 18' 13. 28' 14. 10' 15. 10' 16. 147' 17. 15' 18. 70' 19. 84' 20. 18' 21. 24' 22. 10' 23. 40' 24. 10' 2. 50' 3. 30' 4. 10' 5. 10' 1. 60' 2. 30' 3. 10' 4. 20' 5. 25' 6. 5' 7. 50' 8. 100' 32 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 5 MILLIMETERS Fig. (i. Lavas of volcanic group (crossed nicols). A, Ridge on east line Los Carneros grant (57). Blue-gray biotite and audesite. Zoned andesine including bio- tite and apatite, biotite partially altered to iron ore.s in microgranular andesine base. B. Hill .S51', \l miles soutli of Pinecate Peak ((;3). Purple to gray audesite porphyry. Acid andesine in two generations, hornblende altered to chlorite and iron ores, in very line felsitic andesine and brown glass base. C, Half a mile east of summit of San .Juan grade, elevation 800' (4!)). Glassy black augite andesite. Resorbed and in part altered oligoclase including hornblende ; augite ; and resorbed quartz with reaction rims; in a fine felsitic base of andesine laths, augite granules, iron ores, and brown glass. Lithology The nio.st abundant type of lava, as can be seen from the above sec- tions, is a dark, often purplish, flow-banded andesite porphyry, which in thin section is seen to be composed of zoned and resorbed phenocrysts of andesine (AbsAiiT) and altered hornblende in a felsitic groundmass of acid andesine and yellowish glass. Only slightl}^ subordinate in amount is the light-colored biotite andesite and tufFaceous breccia, also composed of zoned andesine and biotite phenocrysts in a microfelsitic groundraass. The tuffaceous matrix of the breccia contains rounded and fragmented quartz (5 percent), and angular fragments of albite, as well as biotite, in an altered glassy groundmass. The thin flow of "basalt" near the base of the volcanic group is composed of resorbed phenocrysts of oligoclase (7 percent) with well- developed kaolinized rims, a few resorbed augite crystals, and an occa- sional resorbed quartz grain with reaction rims composed of augite granules in broAvn glass. The groundmass is felsitic, with laths of basic andesine oriented around the phenocrysts, interstitial augite grains (26 percent) and reddish glass (20 percent). Rhyolite appears only towards the eastern end of the belt, where the most common rock-type is a pale gray biotite-rhj^olite porphyry com- posed of biotite, quartz, and sanidine phenocrysts in an aphanitic groundmass. DIVISION OF MINES BULLETIN 13:', PLATE 4 A, CASE HAKDENING ANJJ CAVERNOUS WEATHERING IN PINECATE SANDSTONE HALF A MILE SOUTHEAST OF AROMAS SCHOOL B, PINECATE FORMATION : SANDSTONE WITH CAVES Location : just east of cement works, south of San Juan Bautista Photo by Olaf P. Jenkins, A})ril 19.ir> DIVISION OF MINES BULLETIN 133 PLATE 5 >"v. f ■^'^'*- t A, KKU UKOS, Dll'i'ING SOUTH : SAN JUAN GRADE, 1 MILE NORTH OF SUMMIT Note large boulder 5 feel left of figure, and minor fault to right of figure B, HORIZONTAL AND CROSS-BEDDED GRAVELS IN AXIS OF PLIOCENE SYNCLINE 1 MILE NORTH OF SARGENT STATION DIVISION OP MINES BULLrBTIN 1:53 PLATE 6 A, GULLYING IN AROMAS RED SANDS IN SUMMIT HIGHWAY CUT 1 MILE NORTH OP LANGLEY SCHOOL B, CUESTA TOPOGRAPHY IN PLIOCENE ON SOUTH SLOPE OP LOMERIAS MUERTAS w EH Oh i-t Eh tn W O o t— t TO I— t > P o 1^ b£" J- --^ .^5 o d 0) o P -i-^Z i-l J CO H O -J' O ~ o ^ *< g OJ s O +^i>h' ^-. ^ -*-»_, '^ t'-' " Si oj a;0 £&■«-■ 3 O O 1-1 a*"* n: C i^ GEOLOGY ALLEN 33 Age and Correlation The volcanic group overlies the Vaqueros (Zemorriaii) rocks without marked unconformity. No fossils have been found associated with them, but Kleinpell ^^ believes them to be of Saucesian age. He also remarks erroneously ^^ that the ' ' basalt ' ' flows are probably Luisian in age, cor- relative with other middle Miocene basaltic lavas, but this is impossible, since the ''basalts" lie near the base of the volcanic section. A great series of Miocene rhyolitic and more basic flows, dikes, and pyroclastics has been described in the Gabilan Range 30 miles to the southeast by Andrews ^'^ and Wilson,^^ the latter concluding that they are most likely middle Miocene in age. Herold "^ describes vitric tuffs associated with Santa Margarita (upper Miocene) fossils in the Salinas and Jamesburg quadrangles to the southwest, and erroneously suggests that they may have been derived in part from the volcanic activity near San Juan Bautista. The writer believes that the interbedding of the marine sediments with the lavas, and the lack of marked unconformity between them and the underlying Vaqueros rocks, indicate no large lapse of time, and that the volcanic group is Saucesian and possibly even upper Zemorrian in age. Monterey Group (Middle and Upper Miocene) General Character k . The Monterey group, first mentioned by Blake,^° is represented in the Santa Cruz Range of the San Juan Bautista quadrangle by a con- formable sequence of at least 3000 feet of arkosic sandstones, with minor amounts of clay-shale and a few limestone lenses, which, towards the top, are interbedded with and grade into about 2000 feet of diatomaceous and in places siliceous shales. The Monterey rocks lie in a belt, bounded on the west by the San Andreas and on the east by the Sargent faults. South of the Sargent oil field they are overlain with strong unconformity by the Pliocene sands and gravels of the Purisima formation. The base of the section is buried and the top is eroded, so the thicknesses given are minimum esti- mates. Two small isolated areas of Monterey appear west of the San Andreas fault in the Pajaro Canyon, where they are overlapped by Plio- cene, and lie upon granite. The thickness here of the sandstone member cannot be much over 1500 feet. The Monterey rocks are highly folded ; at places the folds are nearly isoclinal and are occasionally overturned. Attitudes within the diato- maceous shales are extremely variable, due to crushing. Minor crenula- tions are well exhibited in the highway exposures in Pajaro Canyon. Attitudes within the massive sandstone member are difficult to determine. Occasional shaly interbeds and lenses of limestone have yielded most of the recorded dips. ^Kleinpell, R. M., op. cit, p. 115, 1938 ; also Schenck, H. G., and ICleinpell, R. N., op. cit., pp. 215-225, 1936. 66 Kleinpell, R. M., op. cit., p. 124, 1938. s'' Andrews, Philip, Geology of the Pinnacles National Monument: Univ. Califor- nia Bull., Dept. Geol. Sci., vol. 24, pp. 1-38, 1936. M Vinson, I. F., op. cit., pp. 215-220, 1943. ^^ Herold, C. L., Further evidence for age of volcanism. Pinnacles National Monu- ment, California: Am. Assoc. Petroleum Geologi.sts P.ull., vol. 21, pp. 1341-1344, 1937. «" Blake, "W. P., Notice of remarkable strata containing the remains of Infusoria and Polythalmia in the Tertiary formation of Monterey, California : Philadelphia Acad. Nat. Sci. Proc, vol. 7, pp. 328-331, 1856. 3—51298 34 SAN JUAN BAUTISTA QUADRANGLE [Bllll. 133 Sandstone, Arkose, and Clay-Shale Members The lower 3000 feet of the Monterej^ group consists predominantly of a remarkably uniform, generally massive, friable, medium- to coarse- grained arkosic sandstone. Within the upper portion particularly, lenses up to several hundred feet in thickness of dark gray clay-shales with fish scales appear, as well as interbeds of white, sandy diatomaceous shale, and characteristic buff-colored fine-grained limestone lenses. The sandstone, while usually weathering to a pale buff color, varies from dark red through yellow to cream and even white with limonitic streaks. Although usually well consolidated, it is poorly cemented, at only a few places being dense and hard, where it outcrops as rounded monoliths. The average sandstone has a grain size of about 1 millimeter, but it varies from less than 0.5 millimeter to a coarse grit with grains up to 2 millimeters in diameter. Buff-colored lenses of fine-grained limestone appear in the sandstones northwest of the Sargent oil field. They are discontinuous and usually less than 2 feet tliick and 20 feet long. In thin section they are seen to contain unidentifiable Foraminifera. One thick bed of white to gray silty siliceous shale is interbedded with sandstone on the north side of Pescadero Creek between the mouth of Hatfield Canyon and the Sargent oil field. Like the upper member of the Monterey group, this 300-foot-thick bed is more resistant to erosion and favorable to tree growth than the sandstone, and forms a line of tree- covered points and saddles on the ridges rising northwards from Pesca- dero Creek. A detail of the lithology of this shale is the common occur- rence of irregular interfingering of sandy and shaly facies, on a scale measured in millimeters. Dark gray to chocolate-colored clay-shale with numerous fish scales is found at several places immediately below the upper diatomaceous shale member of the group. A section at least 200 feet tliick appears along the highway in Pajaro Canyon, as well as on the San Jose highway at the north edge of the quadrangle. The mapped contact between the lower sandstone and clay-shale member and the upper diatomaceous shale member of the Monterey group is an arbitrary one, placed at the top of the highest sandstone, above the zone of yellow limestone lenses and the clay-shales. Fossils were only infrequently found, and then consisted of a few small, poorly preserved thin-shelled peleeypods, fish scales and Foraminifera, mostly in the clay shale just below the diatomaceous shales. Diatomaceous and Siliceous Shale Member The upper 2000 feet of the Monterey group, exposed in greatest thickness in the Mount Pajaro and Atherton Peak ridge, and appearing intermittently along the crest of the ridge north nearly to the edge of the quadrangle, is composed of the characteristic "Monterey diatomaceous shale" of central California. It is a well-bedded, punky-to-hard siliceous shale, commonly occur- ring in layers from 2 to 4 inches thick, at places being more massive. It breaks into blocks by fracturing normal to the bedding planes. On weathered surfaces it is white to pale cream in color ; fresh surfaces may be white, buff, chocolate, or dark gray. Foraminiferal casts are abund- ant, fish scales not uncommon, and small thin-shelled peleeypods are infrequently found. GEOLOGY — ^ALLEN 35 It is more resistant to erosion that the underlying clay-shales and arkosie sandstones, and forms steeper slopes. It weathers to a sparse black soil, breaking do^\Ti so easilj^ that it is hard to find even small rock fragments where soil has developed. It commonly forms steep grassy southwest slopes, with sparse to dense chamisal on the lee side of the ridges. Redwoods in the San Juan Bautista quadrangle are largely restricted to the crest and canyons of the Atherton Peak ridge, under- lain by diatomaceous shale. Age and Correlation Few megafossils were found within the Monterey group in the area, and an accurate determination of the age of these rocks awaits detailed foraminiferal work. It is, however, perhaps justifiable to correlate it lithologically with the type Monterey section ^'^ and the section described by Kleinpell ^- southeast of Del Monte, only 25 miles away, which may be summarized as follows : Thickness : "Lower Pliocene" Santa Margarita sandstone 500' Delmontian Diatomite SOO' Cherty shale and chert 250' Mohniau Organic shale, thin-bedded 1400' Silicified mudstone 500' Luisian Organic shale 500' Relizian Sandstone ] m 1 1 ' f 550' Sandy red beds j '^^'^^^^'- ( 500' Unless the Monterey sea shallowed rapidly to the northwest, and published paleogeographic maps ^^ show no such shoreline nor source of coarse sediment from that direction, the lower sandstone member of vlie Monterey group in the San Juan Bautista quadrangle may be correlated with Kleinpell 's "Relizian" stage, more or less equivalent to a part of the Temblor formation of Anderson.^"* Carrying the comparison a little further, it may be that the 500 feet of Luisian organic shale in the type section is the equivalent of the 300 feet of shale in the sandstone area north of Pescadero Creek. The contact between the two members of the Monterey group as mapped in the quadrangle most nearly approaches, so far as can be told by the lithologic similarities, the line between the lower Mohnian silicified mudstone and the upper ]\Iohnian organic shale. The diatomaceous and siliceous shale of the upper 2500 feet of the section are probabl}^ Delmontian in age, and may extend up into the Mohnian and possibly down as low as the Luisian. Santa Margarita Formation (Upper Miocene) This formation was not found outcropping within the quadrangle, although Jones ^^ reported ' ' a formation composed of white sandstone, eiLawson, A. C op. cit., p. 22, 1893. 82 Kleinpell, R. M., Miocene stratigraphy of California: fig-; 6, also p. 131, Am. Assoc. Petroleum Geologists, 1938. *« Reed, R. D., Geology of California: pp. 185, 21S, Am. Assoc. Petroleum Geolo- gists, 1933. "* Anderson, F. M., A stratigraphic study in the Mount Diablo Range of Califor- nia: Cal. Ac. Sci., Pr (3) G2, pp. 168-187, 1905. 66 Jones, W. P., op. cit, p. U9, 1911. 36 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 6000 South -10,000 SS'\ - 9000 10,000 SARGENT STATION 5000 - 9000 8000 T# - 7000 tS- - 6000 North 5000 50 » 100* 500' 100* 775' 150' 650' 50 • 300' 150' loeo 2.M0 fecr red sands yellow sands silty clnys and buff-colored sands massive cross-bedded gravels thin bedded silts silts and mudstones with lenses of fine gravel sandstones conglomerate massive buff sandstone massive buff sajidstone with interbeds of ooarse grit & fine conglomerata 1350' not exposed 200' silts with some carbona- cous shales 200' not exposed 100' conglomerates composed of shale pebbles BETABEL Fig. 7. Piioceiie ;:iction along railroad between Betabel and Sargent Station GEOLOGY — ALLEN 37 West 1' ' 250 » deep red massive structurless sandstone (Aromas) 1000 • soft sandstone with a few thin layers of broken shells (not all exposed) IvsX^ 1- •. ■■ -300 -200 35» 5' 20' 50' sandy shell marl (mostly Ostrea vespertine) soft yellow clay shale soft sandstone with shell fragments massive soft medium grained sandstone |3S ^:'_' iz: , . ■ 3' •shell marl (mostly Mytilus sp.) *', 60' soft coarse grained sandstone -100 -0 2' shell marl 30' soft coarse grained sandstone 18' Enndy sholl marl 10' soft coarse grained sandstone 5' sandy i'ossil marl 40' soft coarse grained sandstone 5' basal conglomerate. Unconformable contact with Monterey shale li^^ I.'.;-. l.--J-.-_\i mm East Fig. S. Pliocene section along highway 2 miles north of Aromas which is quite friable and which breaks down into a pure white quartzose sand. . . . There are many beds practically composed of Astrodapsis antiselli, the characteristic echinoid of the Santa Margarita formation." This formation outcrops "about one mile west of the edge of the area mapped, and just north of the Pajaro River, " which would be northwest across the river from Logan quarry. A coarse-grained, sugary textured white quartzose sandstone less than 30 feet thick lies directly upon the granite across from Logan quarry, beneath the Pliocene sands and gravels. In thin section the grains are sharp, angular, and broken. It is composed of 70 percent quartz, nearly all of which is strained and anomalously biaxial, but other- wise quite clear. The next most abundant constituent is fresh clear untwinned albite (optically positive, r less than v) about 20 percent. There are small amounts of angular chert grains, and some myrmekite and microcline grains. Lithologically it appears not unlike the "feldspathic" white sand- stone of the Santa Margarita in the Santa Cruz quadrangle immediately to the northwest, but no fossils were found in it ; abundant fossil beds containing Dendraster appear immediately above it in the overlying Purisima sediments. 38 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Purisima Formation (Middle and Upper Pliocene) General Character The Purisima formation includes a conformable series of nearly 10,000 feet of poorly consolidated clays, silts, sands, and gravels, pre- dominantly marine towards the base and continental in its upper portion, which overlaps upon Santa Lucia granite, Franciscan, and Monterey, and is overlain unconformably by the Pleistocene Aromas red Bands. It is highly variable in composition both vertically and laterally, fossil- iferous in its marine facies, and has been folded so as to exhibit attitudes varying from horizontal to vertical. It occupies most of the region northeast of the San Andreas fault and east of Chittenden, and lies upon the Franciscan north of the Sargent oil field. It composes nearly all of Lomerias Muertas, the hills east of Anzar Lake, and those north of the upper Pajaro Canyon. West of the San Andreas fault, it lies unconformably upon the Santa Lucia granite and Monterey in Pajaro Canyon, and covers most of the strip of hills between the fault and Pajaro-Corralitos Valley. Few trees or brush grow upon rocks of the Purisima formation, at least in the eastern portion of the quadrangle. A large part of the extensive beef-cattle industry of the region depends upon grazing of these grasslands. The unconsolidated and porous nature of the sands and gravels and the presence of interbedded plastic clays has resulted in large- and small-scale landsliding, particularly on the north side of Lomerias Muertas, 80 percent of which is covered with old and new landslide scars. The latest large movement occurred in 1938, when a strip several hundred yards wide broke and slid over a distance of nearly a mile.^® Lithology The basal gravels of the Purisima formation are usually composed of debris from underlying rocks. Along the western contact, from Sargent oil field south to Pescadero Creek and Chittenden, the Pliocene unconformably overlies Monterey diatomaceous shale, and in many places these gravel beds are largely'' composed of angular to subangular fragments of white shale. North and east of the Sargent oil field they overlie the Franciscan, and the rudely bedded, dark-brown to deep red gravels are predominantly Franciscan sandstone, with lesser amounts of chert, black shale, basalt, and quartz. North of La Brea Creek branch of the Sargent fault, the basal gravels are very thin, and three serpentine outcrops are exposed along the fault either by erosion or faulting or both. A heavy conglomerate made up of slabs of Franciscan sandstone and smaller pebbles lies adjacent to the middle exposure of serpentine. The crest of a Franciscan ridge north of the oil field and east of the Sargent fault is capped up to an elevation of 800 feet by south-dipping conglom- erates and a sandy marl Avhich fills teredo or pholad borings in underlying sandstone beds. West of the San Andreas fault and 2 miles down river from the Logan quarry, a coarse basal conglomerate only 5 feet thick rests uncon- formably upon white diatomaceous shale. It is composed of boulders up to 6 inches in diameter of Franciscan sandstone, white shale, granite, eoKrauskopf, K. B., et al.. op. cit, pp. 630-638, 1939. GEOLOGY ALLEN " 39 rhyolite, chert, and shell fragments. At Logan quarry, both granite and Monterey sandstones and shale are anconformably overlain by a layer of subangnlar granite boulders, followed by a 1-foot bed of fossil- iferous grit and pebble-conglomerate, which also forms the matrix between the boulders. Most of the fossils are barnacles. The pebbles are 80 percent quartzite, the rest being chert, granite, etc., and compose only 10 percent of the rock ; the gritty matrix forms 70 percent and the interstices are filled with 20 percent clayey and calcareous matter. This bed is overlain by about 35 feet of soft friable gray to buff -colored sandstone, which caps the ridge above the quarry and dips about 12° SW. Above the basal conglomerates in the Sargent area there is a bed of massive, friable, fine- and even-grained buff-colored sandstone about 1500 feet thick. It is reported in old well records ^"^ to rest on Franciscan south of the Sargent fault, but this is doubtful in view of the thick underlying Monterey section, unless complicated by unrecog- nized structural features. Marine fossils are abundant throughout the lower 4500 feet of the south- and southeast-dipping section south of La Brea Creek. A few fossiliferous lenses appear as high as 7000 feet up in the section. The fossils usually occur in hard calcified lenses which weather out to form resistant float boulders ; in a few places they occur in silts and the pres- ervation is poor. A prominent conglomerate composed largely of shale pebbles occurs about 5500 feet above the base of the section. It is from 30 to 50 feet thick and has been traced for nearly 2 miles in a north- easterly direction from near the mouth of Pescadero Creek almost to Sargent Station. A similar bed 40 feet thick occurs about 7500 feet up in the section, and forms one of the cuesta-like ridges on the south slope of Lomerias Muertas. It is composed of 70 to 90 percent well-rounded white shale pebbles in a matrix of coarse grit composed of angular and rounded fragments and grains of shale, quartz, chert, and volcanics. It overlies and fills channels in a coarse sandstone and is overlain by sandstone. The upper 5000 feet of the section, judging from the presence of gypsum, a few fresh-water fossils,*"^ and its highly variable, lenticular and cross-bedded nature, is predominantly continental. The Purisima formation west of the San Andreas fault is even more highly fossiliferotis than to the east. In the basal 300 feet exposed along the highway in Pajaro Canyon, about 63 feet are fossil beds, largel.y made up of small oysters {Ostrea vespertinaf) , one individual bed being 35 feet thick. Northward along the San Andreas towards the corner of the quadrangle, the Pliocene tends to become coarser, with thicker conglom- erates, interbedded with massive sandstone. In the Capitola quadrangle Gregerson ^^ has mapped two members in the sandstones and gravels ; the upper predominantly conglomeratic, and the lower, mainly sandy. Columnar Sections A better idea of the variations in lithology can be obtained from the accompanying measured sections (figs. 7, 8, 9) on different scales than from any amount of written description. The distances given "up in the section" are fairly exact, although there is undoubtedly considerable overlap of the Pliocene against the older rocks, as the basin deepened dur- s^Michelin, op cit., p. 476, 1943. 88Krauskopf, K. B., Feitler, S., and Griggs, A. B., op cit., p. 631, 1930. «B Gregerson, A. L., personal communication, 1945. 40 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 South Wli'i.ljtaaij 7400 ■ 7300 7200 -^ 7100 North Thickness Ft. In. 18 massive coarse grained sandstone 24 fins grained clayey sandstone 24 20 2 3 3 2 3 12 6 6 6 30 15 IB 2 1 18 2 10 2 8 42 5 6 24 12 2 30 3 18 3B7' massive coarse grained sandstone soft fine grained clayey sandstone coarse grained clayey sandstone fine grained clayey sandstone coarse grit and fine conglomerate soft clayey sandstone blue silty shale massive sandstone massive sandstone with conglomerate lenses massive sandstone well bedded sandstone massive sandstone pebble conglomerate and grit masEive and cross bedded sandstone pebble conglomerate and grit massive and cross bedded sandstone pebbly sandstone blocicy siltstone massive and cross bedded sandstone fossiliferous lenses and sandstone shaly siltstone discontinuous conglomerate lenses blue shale silty sandstone grading up into shale massive and cross bedded sandstone silty sandstone fossil lenses interbedded sandstone and silt fosr.il lenses sandstone fossil lenses silty s'^ndstone massive nodular sandstone interbedded silt, sandstone and fine eg. fossiliferous conglomerate interbedded silt, sandstone and fine eg. pebble cinglonerate pebbly sandstone (Beds strike N. 65-85° W. and dip 45° S.) Pig. 9. Pliocene section in highway cut 1 mile south of Sargent Station GEOLOGY — ALLEN 41 iug tbe deposition of the sediments. The tliickness of the section south of the Sargent oil field correlates very well with the thickness of 5250 feet measured in the deep well (Tidewater Associated 's ''Murphy No. 1") drilled half a mile southeast of Sargent Station. Conglomerates are more abundant in the surface section, close to the Santa Cruz land mass, than they are in the well section, 3 miles farther east. Log of Tideioater- Associated' s well ''Murphy'' No. 1 located half n mile sonflieast of l^arf/ent Station (Revised and corrected for a 40° dip) 3500' Not logged from surface to this depth 46 siltstone with shaly interbeds ■ 33 fine gi\iy silty sandstone 168 shaly siltstone 46 fine gray silty sandstone 38 shaly siltstone 69 fine-grained siltstone 138 shaly siltstone 115 fine-grained shaly siltstone with 4 thin sandstone beds 230 fine-grained sandstone with a few shaly siltstone beds 191 shaly siltstone interbedded with fine-grained silty sandstone, 2 horizons of pebbly sandstone and 1 bed of grit 10' thick 77 fine-grained siltstone 33 fine-grained silty sandstone 405 massive fine- to medium-grained sandstone 54 fine-grained silty sandstone 23 siltstone 91 fine-grained silty sandstone 54 siltstone 38 fine-grained silty sandstone 15 shaly siltstone 69 fine- to medium-grained sandstone with some silty sandstone 253 fine- to medium-grained sandstone with occasional shale, thin lime- stone, and peb!)Iy interbeds. Conglomerate near base. 15 pebble conglomerate 284 fine to medium-grained sandstone with occasional silty sandstone and 1 conglomerate interbed near base 23 shale 15 conglomerate with limestone at base 50 medium-grained sandstone 35 conglomerate 52 F^ranciscan sandstone (V) 6921' Total depth In the northwest corner of the quadrangle the upper gravels of the formation are folded in a syneline trending west-northwest. The section exposed in a quarry at the crossroads north of Casserly School strikes N. 56° W. and dips 20° NE., being as follows : 10' yellow unsorted silt and boulders 30' soft fine-grained buff-colored sand with some clayey layers, grading down into coarse-grained crossbedded sand with streaks of pebbles 35' coarse crossbedded gravels, with layers of pebbles from 1 to 4 centimeters in diametei', usually sub-rounded to sub-angular, in a matrix (20 percent) of gray gritty to silty sand. Pebbles are 40 percent granite and aplite, 15 percent white shale, 15 percent chert, 15 percent basalt and andesite, 10 percent Franciscan sandstone, with a few pebbles of quartz and other rocks. About 20 percent of the pebbles are l)adly weathered so that they crumble easily. The crossbedding dips to the northeast. 5' plus reddish, medium-fine-grained, well-sorted, well-rounded sandstone, com- posed of about SO percent quartz, 15 percent feldspar, and 5 percent dark lithic grains 80' plus 42 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Half a mile farther west, in another quarry, there is a similar section which dips 65° NE.: 10' coarse gravels 10' gray silt 20' medium gravels 15' soft friable gray sand 50' coarse gravels Unconformities Within the Formation The Purisima formation is more than twice as thick as the maximum thicknesses given for the rocks described by ^ones'^*' ; none of the section is Miocene in age, and, as was first recognized by Martin,'^^ there are no pronounced unconformities within the group. No discordances not attributable to slumping, folding, or local faulting were observed, the degree of folding is much the same tliroughout, and non-marine gravels, although less frequent in the lower portions, are interbedded throughout the section. The apparent unconformity between the south-dipping beds along the railroad south of Sargent Station and the southeast-clipping beds 1 mile to the west is exj^lained by a sharp swing in the strike. Some geologists have suggested a fault up the creek half a mile west of the railroad, but this is not believed to be probable. The only recognized fault cutting the section in the Sargent area is the Sargent fault, and the displacement on this is in the order of 600 feet. The fauna west of the San Andreas has a decidedly different aspect than that to the east. It contains numerous echinoids, barnacles, oysters, and pectens not found to the east, and appears to represent a shallower facies. Perhaps the northern spur of the Gabilan Range west of the fault was an offshore shallow reef. The northward initial dips of the foreset beds in the upper part of the section in the northwest corner of the map suggest that the Santa Clara delta had by this time filled the Pajaro seaway and was spreading out west of the gap. No Santa Margarita fossils were found in the area just north of Pajaro Canyon mentioned by Jones,'^^ or in the Sargent district northwest of Hoi lister, as indicated by Wilson.'^^ Age and Correlation Fossil collections made b}^ Martin,''^ Arnold and Hannibal,'^^ and by the writer, totalling over 80 forms, have been examined, revised, and combined by Dr. A. Myra Keen and the writer to form a locality check list which is given as an appendix to the author 's thesis on the San Juan Bautista quadrangle, on file at the University of California, Berkeley. The Purisima formation, as mapped in the San Juan Bautista quad- rangle ranges in age from lower middle to upper Pliocene. In the type section the Purisima is regarded by Schenck and Keen as including all ''"Jones, W. F., op. cit., p. 65, 70, 71, 1911. "Martin, Bruce, op. clt., p. 233, 1916. •-Jones, W. F., op. cit., p. 69, 1911. ■^3 Wilson, Ivan F., op. cit., p. 262, 19 43. ■'* Martin, Bruce, Pliocene of middle and northern California: Univ. California, Bull. Dept. Geol. Sci., vol. 9, no. 15, p. 233, 1916. ''5 Arnold, Ralph, and Hannibal, Harold, collection at Stanford Museum of Pale- ontology. GEOLOGY — ALLEN 43 of the lower and middle PlioceneJ^ In the San Juan Bautista quad- rangle, it does not extend into the lower Pliocene, and it may contain sediments that are younger than any in the type sectionJ'^ Since the name Purisima has been applied by earlier workers to these beds in the area under consideration, its use will be continued in the present paper. It is possible that the upper part of the San Juan Bautista Purisima may be equivalent to the Merced.'^^ Aromas Red Sands (Middle? Pleistocene) General Character Most of the southwest quarter of the San Juan Bautista quadrangle is mantled with a dark brown to red, friable, quartzose sandstone, which disintegrates and washes easily when exposed in gullys and roadcuts to form miniature badlands. These beds were first noted by Blake '^^ and Antisell ^^ as overlying both Monterey shale and Merced, and thej^ were later described briefly by Hamlin ^^ who remarked that they were later than the Paso Robles formation. The mapped boundaries of the formation agree remarkably with the boundaries of the "Moro Co jo loamy sand" mapped by Carpenter and Cosby ^^ in their soil survey of the Salinas Valley. The Aromas red sands are at least 600 feet thick, but probably not over 800 feet thick, south of the town of Aromas. A typical section of the sands 180 feet thick appears in the railroad cut 1 mile west of town. The Aromas sands unconformably overlie all older formations with which they are in contact, successively overlapping upon Santa Lucia granite, San Lorenzo, Vaqueros, volcanics, and Pliocene rocks. They extend eastward to form the crests of the ridges 2 miles northeast of Pinecate Peak, where the}^ also reach their maximum elevation in Hill 796'. They are overlain by terrace gravels and alluvium. The mapped contact between the Aromas sands and terrace gravels in the southern portion of the quadrangle is in large part based upon physiographic expression of the terrace levels as observed in the field. The extreme southeastern portion of Lomerias Muertas within the quadrangle is composed of nearly horizontal dark brow^n to red cross- bedded sands, quite similar in appearance and composition to the Aromas sands, with which they have been mapped. They overlie the Purisima gravels, which dip gently to the south, with a slight unconformity. Several of the lowermost foothills bordering the Pajaro-Corralitos valley west of the San Andreas fault are composed of Aromas sands. The ridge 1 mile north of the Carlton School and just east of the San Jose highway is the northernmost of these exposures in the quadrangle. ™ Schenck, H. G., and Keen, A. Myra, California fossils for the field geologist, p. 85, Stanford University Press, 1940. " Haehl, H. L., and Arnold, R., The Miocene diabase of the Santa Cruz Mountains in San Mateo County, California: Am. Philos. Soc. Proc, vol. 43, pp. 16-53, 1904. ™Lawson, A. C, The post-Pliocene diastrophism of the coast of southern Cali- fornia: California Univ. Bull. Dept. Geol. Sci., vol. 1, p. 1893. TO Blake, W. P., op. cit., pp. 328-331, 1856. 80 Antisell, T., Survey for railroad, U. S. 33d Cong., 2nd Session, Senate Ex. Doc. no. 78, vol. 7, part 2. p. 36, 1856. 81 Hamlin, Homer, op. cit., p. 16, 1904. 8- Carpenter, E. J., and Cosby, S. W., Soil Survey of the Salinas area, California : U. S. Dept. Agr., Bur. of Chemistry and Soils, no. 11, pp. 1-80, 1925. 44 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Attitudes within the sands are difficult to obtain, due to its massive nature as well as to the cross-bedding occasionally present. Dips seldom exceed 6 degrees, however ; and most of them have westward components. Recent minor faulting and subsequent erosion in the area between Dun- barton and Langley School has disturbed the sands and exposed a num- ber of small patches of granite. Lithology The base of the Aromas sands, where they overlie granite, is fre- quently composed of a breccia made up of angular blocks up to 6 inches in diameter of granite, aplite, limestone, and schist in a dark red or brown muddy arkosic matrix. Areas of a similar breccia appear up to elevations of 1200 feet well within the granite area, usually on the crests of the ridges in the Gabilan Range. Some of these areas cover as much as an acre, but the deposits are seldom over 20 feet thick. "When over- lain by the sands, the breccia grades upward into them within a few feet. The type section for the Aromas sands, fairly characteristic of the sands as a whole, is in the railroad cut 1 mile west of the town of Aromas. Here an exposure 800 feet long and 170 feet high on the south side of the track gives the following section : (1). 30' plus fine, even -grained, buff-oolored friable sands, well cross-bedded with aeolian type fif bedding (concave upwards), all foreset beds dipping to the east ; lies upon an even surface which dips 6 degrees to the west. (2). 2 to 8' reddish and varicolored, massive, friable, porous fine-grained sand, partly cemented with iron oxide and containing iron oxide nodules. Composed of 80 percent quartz, sub-rounded to sub-angular, with iron-oxide coatings, .2-..5 mm. in diameter ; 15 percent feldspar, both fresh and altered, sub-rounded to well rounded, .1-.3 mm. in diameter; 10 percent dark lithic and mineral grains, well rounded, averaging .3 mm. in diameter ; in 25 percent matrix of fine limonitic clay. Porosity of the sand is perhaps 10 percent. This overlies (4) throughout most of the exposure, but at one place a channel in (4) is filled with : (3). to 5' deep red to black well-bedded hematitic sand, weathering to yellow along fractures. Beds from half an inch to .3 inches thick, some of the thinner beds being nearly pure black secondary hematite, but most of the rock containing up to 40 percent quartz, even-grained, sub-rounded to sub-angular, .2-.5 mm. in diameter. (4). 30 to 40' massive, faintly cross-bedded, very friable and loosely com- pacted buff-colored even granular sand, weathering to white in a few places. Composition much the same as (2), except that there is less iron-oxide cement, the quartz grains are better rounded, there is up to 20 percent feldspar and a few biotite flakes present, and the porosity is greater. There are a number of variations from the above types, perhaps the most common being the addition of coarse angular granitic debris. Plant material and carbonaceous matter is also quite common. Physiography From the point of highest elevation of the Aromas sands in Hill 796' south of Anzar Lake, the quite uniform and concordant tops of the ridges made up of the sands slope to the southwest about 100 feet to the mile, merging with the upper terrace gravels near the southwest edge of the quadrangle. A few flat-topped initial surfaces remain on the ridges, GEOLOGY — ALLEN 45 indicating' a physiograpliie stage of latest youth. The area, however, is well dissected by mature valleys, which have been partially filled with gravels to elevations reaching 100 feet in the western, and 500 feet in the central portion of the quadrangle. These terrace deposits were then re-excavated deeper than before and filled again. The Aromas sands are so poorly cemented, despite their iron content, that under present climatic conditions the slightest break in the vege- tation mantle is sufficient to begin gullying. Manj^ of the remnants of the old fiat-topped ridges are bounded by gullied cliffs from 5 to 30 feet high. Age and Origin The Aromas sands were deposited during the Pleistocene physio- graphic cycle which developed the late mature "high-level" valleys and surfaces in the Gabilan Range. They have suffered only very minor faulting and tilting, and are believed, without fossil evidence, to be at least as late as middle Pleistocene in age. They are later than the Paso Robles formation, ^^ and older than the high terrace gravels. They were laid down by the action of both wind and waves, on a low-lying plain, as lagoonal deposits, sand dunes, and bars. After uplift, the oxidization and solution of the magnetite in the sand resulted in the development of red colors, cementation, and reprecipitation of hematite. Terrace Deposits and Alluvial Fans (Quaternary) Dissected terrace deposits occur along most of the drainage systems in the area, up to an average elevation of over 400 feet. The upper portions of these terraces grade at many places into gently sloping alluvial fans from the hills behind them. The alluvial fans are later than the terraces, but it is difficult to differentiate them on the map. Terraces are best preserved along the western portion of the course of "Elkhorn Valley", the extension of the drainage of Elkhorn Slough through the center of the quadrangle. Three levels have been developed near the west edge of the map at elevations of 60, 80, and 200 feet, and these levels rise eastward so that in the area immediatelj^ west of San Juan Bautista, gravels cap the low hills at elevations up to 450 feet, rising in one or two places to 500 feet. The general slope to the west of the terraces in this drainage is about 35 feet to the mile. Along the southern edge of the quadrangle the best developed ter- race, which also is the level of the northern end of the Salinas Valley, rises from about 60 feet near Del Monte to over 500 feet north of Gabilan Creek. On the soil survey map of the Salinas Valley,^^ the various terrace levels, particularly in the southwest quarter of the map, correspond closely with soil divisions. The upper terrace is mapped as "Tierra sandy loam, ' ' the middle terrace as ' ' McClusky sand loam, ' ' and the low terraces as the "Elkhorn sand." The high-level terraces in the granite area on Gabilan Creek are mapped as "Placentia sandy loam." The writer did not complete the mapping of the various terrace levels, but they are approximated by the soil map. ^ Fairbanks, H. W., Geology of a portion of the soutliern Coast Ranges : Jour. Geology, vol. 6, pp. 551-576, 189S. »* Carpenter, E. D., and Cosby, S. W., op. cit., 1925. 46 ■ SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Small terrace remnants also occur along the course of tlie I'ajaro and San Benito rivers, and are well developed on the south side of Lomerias Muertas. Remnants appear along the course of San Miguel Canyon and its tributaries. An east-sloping terrace from 350 to 200 feet in elevation and up to 1 mile in width is well preserved along the base of the mountain front southwest of Gilroy. Remnants of this Kame level occur as far south as Sargent Station. The terrace deposits are predominently composed of granitic material, with subordinate amounts of Sur metamorphics, although locally they are in part or largely made up of material derived from the adjacent older rocks, as for instance, the terraces southwest of Gilroy which have Franciscan components, and those north of the San Benito River, which are derived from the Pliocene rocks of Lomerias Muertas. Everywhere thej'' are poorly sorted, torrentially bedded, with relatively few of the component rock fragments rounded. When such rounded pebbles and cobbles appear they are often broken, indicating their origin from older formations. Along Gabilan Creek where the terraces rest upon granite, they can not be distinguished unless they show physio- graphic expression, or are exposed in cuts. In areas where they lie upon the Aromas sands, they have a considerable admixture of the red sand which at places forms lenses of appreciable size within the gravels. There is a well defined cementation of the upper surface of the highest terrace. This mesa-like capping appears at a number of places in the western half of the quadrangle. The Pleistocene San Benito River extended westward from San Juan Bautista across the center of the quadrangle, down the now over- sized "Elkhorn Valley" into the drowned valley now occupied by Elkhorn Slough, and out into the deep Monterey submarine canyon, which heads directly opposite the mouth of the slough, not opposite the present mouth of the Pajaro River. The various emergences and sub- mergences which produced the terrace deposits are discussed in more detail under the heading geomorpliology. Brea Deposits (Quaternary and Recent) Between 2 and 3 miles up the creek from the mouth of Pescadero Creek canyon, a peculiar dark-brown to black breccia is plastered against the north canyon wall and outcrops in the tributary stream beds up to an elevation of about 200 feet, where it appears to underlie remnants of an old terrace surface. The breccia is made up of angular fragments of diatomaceous shale in a matrix which in the creek beds is hard brittle asphalt, but which on the ridge points has weathered to a punky, dirty brown, mudlike material. These deposits, mapped by Jones ^^ as Pliocene, are remnants of Pleistocene valley fill corresponding with the upper terrace stage, which have been cemented by asphalt from oil seeps in the area and since that time mostly eroded. There are many recent oil and asphalt seeps in the Sargent region. These were mined as early as the 1860 's^^ along La Brea Creek, years before the first attempt to drill for oil was made, and a refinery operated at Sargent in 1864. s^> Jone.s, W. P., op. cit., pi. 18, 1911. 80 California State Mining Bureau, Catalogue and description of the minerals of California: California Min. Bur. Kept. 4, pp. 2S8-289, 1884. GEOLOGY ALLEN 47 In nearly every case, the seeps are associated with the unconformable contact of the Pliocene over the Miocene rocks, or with faults in both formations. The deposits are not large, except on La Brea Creek, where they cover, in one or two cases, an acre or more. Travertine Deposits (Recent) A tributary to Hatfield Canyon (running south into the canyon at the " d " in Hatfield on the geologic map, pi. 1 ) has built up its bed for over half a mile with travertine terraces. The lime-rich waters are derived from a series of small springs which are aligned in a northwest- erly direction in the headwaters of the tributary. The terraces consist of cemented boulders and blocks of sandstone at the base, overlain by alternating pools and falls whose lips are made up of buff to gray travertine. Alluvium (Recent) Recent alluvium consisting of unconsolidated gravels, sands, eilts, and clays, cover large portions of the wide valleys of the Pajaro and San Benito rivers and the floors of the larger tributary stream in the area. Alluvium grades into terraces in the lower Pajaro Valley in such a way that the contact is very difiicult to draw. The meanders of the major streams are incised from 20 to 40 feet deep in these deposits, this recent rejuvenation more probably resulting from a slight climatic change than from a change in base level.^'^ In the areas south of Gilroy and immediately north of San Juan Bautista there are flowing wells, and it has been suggested by Clark ^^ that the groundwater level, sloping from the northeast and from the south, is dammed by the bedrock channel of the lower Pajaro River. These artesian basins ^^ are believed to be better explained by recent slight warping. Bedrock does not appear in the upper canyon of the Pajaro, and the artesian basins do not extend into the canyon south of Sargent or west of Chittenden Junction. Landslides (Recent) Landslides are quite common in the San Juan Bautista quadrangle, being particularly abundant in the unconsolidated Purisima formation and along the course of the San Andreas fault. Only the more prom- inent were mapped. The outstanding landslide is also one of the most recent, having occurred in 1938, on the north slope of Lomerias Muertas. It is over a mile in length and several hundred yards wide, extending from an elevation of over 1000 feet down to 250 feet at its toe. It has been described in detail by Krauskopf, Feitler, and Griggs."° Most of the north face of Lomerias IMuertas is covered with old landslide scars, and there are 12 slides on the south side of the hills large enough to map. Extensive landsliding has taken place adjacent to and just west of the San Andreas fault along its course north of Pajaro Canyon. It is 8^ Grant, U. S., and Putnam, W. C, Barrancos and arroyos in California ; Geoi. Soc. America Proc, 1935, p. 331, 1935. ^ Clark, W. O., Ground water in Santa Clara Valley, California : U. S. Geol. Survey, Water Supply Paper 519, p. 79, 1924. 89 Idem., plate XIX. »o Krauskopf, K. B., et. al., op. cit, 1939. 48 SAN JUAN BAUTISTA QUADRANGLE [BuU. 133 possible that these movements have carried Monterey sediments down and over the Pliocene west of the fault, so tliat the mapped contacts between these formations is in error. The oversteepening of the north wall of Pajaro Canyon, due indirectly to recent horizontal movements along the San Andreas fault, has resulted in large landslides north of Chittenden. STRUCTURE Introduction The junction of the Santa Cruz Range on the north with the Gabilan Range on the south occurs within the area mapped. These ranges are separate structural, as well as stratigraphic provinces, characterized in the former by 10,000 to 25,000 feet of highly folded Franciscan and middle Tertiary deposits, and in the latter b.y to 3500 feet of faulted lower Tertiary sediments and volcanics resting upon a granitic basement. The boundary between these two areas of ' ' thick-blanketed ' ' and ' * thin- blanketed" mountains approximates the San Andreas fault zone; topographically they are separated by the Pajaro canyon, the only water-gap south of the Golden Gate between the Santa Clara-San Benito trough and the sea. The rocks of the Santa Cruz Range have not only been highly folded, they have also been broken by thrust faults along which repeated move- ment has taken place, into 4 and possibly 5 more or less parallel belts from 1 to 3 miles in width. The rocks within the Gabilan Range have been folded only adjacent to major faults ; they have been thrust-faulted by at least 3 sets of faults so that detailed structure is difficult to determine. The structure of the San Juan Bautista quadrangle can best be dis- cussed by first considering the chief structural feature of the area, the San Andreas fault, and then by taking up in turn the various faults and intervening belts from the northeast to the southwest, first in the Santa Cruz and then in the Gabilan ranges. San Andreas Fault The San Andreas fault zone, which is from 100 to 800 feet in width and appears wider in places due to parallel and en echelon faults, is a prominent and well defined physiographic feature throughout most of its course, which trends N. 47°-48° W. within the San Juan Bautista quadrangle. The line of recent movement easily can be traced upon the topo- graphic map, upon air photographs, or in the field, by the abrupt break in slope along the west side of the Santa Cruz Range and the straight course of the trough-valleys, which mark the fault both northwest and southeast of San Juan Bautista. The fault trough separates the rolling foothills which rise from the Pajaro Valley to elevations of 600-1000 feet, from the steep upper slopes of the Santa Cruz Range. The streams drain- ing the upper portion of the range are offset to the northwest as they cross the fault. Other common fault fea4;ures include a series of undrained hollows and sag ponds, numerous small recent scarps, and numerous recent and not-so-recent landslides. GEOLOGY — ALLEN 49 The straight course of the fault across irregular topography indicates that it is essentially vertical. Several tributary faults largely in Plio- cene sediments but expressed topographically by saddles, benches, and sag ponds, come into the San Andreas fault from the nortlnvest at acute angles. One of these apparently forms the contact between the Pliocene and the Aromas red sands in the foothills just east of the San Jose highway 3 miles northeast of Watsonville. Two springs and a small scarp 10 feet high, with the east side do"\vn, give evidence of recent move- ment on this fault. The San Andreas fault zone coincides within the San Juan Bautista quadrangle with a line of movement which was first initiated in pre-San Lorenzo time. The first recorded movement along this line, which may be referred to as the "ancestral San Andreas fault," was normal down- faulting of the northeast side, in post-Franciscan time, followed by ero- sion and complete removal of the rocks of the Franciscan group from the Gabilan Range, which they presumably once covered. There are great thicknesses of Cretaceous conglomerates and sandstones overlying Franciscan, both in the Santa Cruz Range of the New Almaden quad- rangle immediately to the northwest,^^ and in the San Benito quadrangle to the southeast.^^ In the area northeast of Morgan HilP^ and in the San Benito quadrangle ^* middle Eocene sandstones and shales rest unconformably upon the Cretaceous. It is believed by Taliaferro ^^ that this initial movement on the ancestral San Andreas fault took place in the lower Eocene. Renewed movement along the fault occurred in lower middle Miocene and again in post-Monterey and pre-middle Pliocene times, when granite west of the fault was uplifted. These movements were in the same direc- tion as the original Eocene faulting, but the latter at least was a result of thrusting rather than normal faulting, since the Monterey group was highly folded at this time. Evidence for the direction of movement during the lower or middle Pleistocene is contradictory. North of the Pajaro River the Pliocene sediments west of the fault are in contact with Monterey rocks to the east ; south of Pajaro River, Pliocene rocks east of the fault abut on granite west of the fault. Apparently the area west of the fault was subjected to differential uplift of the Gabilan Range and do^^^awarp of the area farther north. Upper Pleistocene uplift of the west side of the fault is shown by several lines of evidence, and recurred at least two times. The middle ? Pleistocene Aromas sands are tilted to the southwest about 100 feet to the mile. The upper Pleistocene terrace gravels rise to the east about 35 feet to the mile, and east of the fault the terrace surfaces drop about 150 feet. The foothill ridge west of the fault and east of the lower Pajaro Valley has been uplifted about this amount, offsetting the slope from the crest of the Pajaro-Atherton Peak ridge. 81 Gilbert, C. M.. personal communication, 1945. »2 Wilson, L F., op. cit, pp. 198-205, 1943. »3 Gilbert, C. M., Tertiary sediments northeast of Morgan Hill, California: Am. Assoc. Petroleuir. Geologists Bull., vol. 27, no. 5, pp. 640-646, 1943. SI Wilson, I. F., op. cit., pp. 205-210, 1943. 85 Taliaferro, N. L., Geologic history and structure of the central Coast Ranges of California: California Div. Mines Bull. US, p. 154. 1941. 4—51298 50 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Recent moveiuent along the San Andreas fault api)ears to have been entirely horizontal, the southwest side having moved relatively to the northwest. About 15 youthful canyons and gulches drain the southwest slope of the main Santa Cruz ridge. Several of the streams join as they cross the fault to flow down through the foothills in six canyons. Several other canyons southwest of the fault now have no matching headwaters east of the fault. By plotting the course of the streams crossing the fault on a sheet of paper, and then by cutting the paper along the trace of the fault, 14 of 15 streams may be matched by moving the slip of paper rep- resenting the southwest side of the fault to the southeast an equivalent of about 3800 feet, demonstrating that the recent horizontal movement has been in the order of less than 1 mile. No evidence other than that mentioned previously has been found to substantiate reports of hori- zontal displacements greater than this. Recent vertical displacements by normal faulting on a small scale appear in highway cuts 2 to 3 miles northwest of San Juan Bautista. At one point just south of the main fault zone, terrace gravels have been dropped down against granite on the southwest. Half a mile north across the fault zone, steeply southwest-dipping Pliocene sands and con- glomerate have been dragged down on the southwest side of a normal fault whose footwall is composed of nearly horizontal Pliocene sediments. Both of these normal faults are approximately parallel and dip steeply towards the. San Andreas fault. During the San Frp>i^isco earthquake of 1906, the western piers of the railroad bridge across the Pajaro Kiver moved 3.5 feet to the north- west, and fences halfway between the bridge and San Jiian Bautista were displaced an equal amount. ^^ Farther south the fissure appeared to leave the main fault zone and trend more easterly towards Hollister. The epicentre of the earthquake of July 24, 1921, was located at Chittenden,^^ but there was no displacement at the surface. Santa Cruz Range Carnadero Fault Franciscan sediments and serpentine are in fault contact with Mon- terey silty shale and arkosic sandstone at the north edge of the map 2 miles west of Gilroy. Although masked by terrace deposits at all but one point, the fault presumably dips southwest toward the Franciscan belt which has been thrust up against the Miocene rocks on the northeast. The fault parallels Carnadero Creek in a N. 50-60° "W. direction for several miles, and may be a branch of the "Uvas Creek fault" ^^ to the northwest. Post-Monterey movement along the fault has been large, but no evi- dence of its magnitude appears within the quadrangle. It is at least 3000 feet, since upper Monterey shale is exposed at the base of a Fran- ciscan escarpment 2000 feet high. The serpentines found along the course of the fault have been squeezed up along it as "cold intrusions." ""Lawson, A. C, et. al., The California earthquake of April 18, 1906: Report of the State Earthquake Investigation Commission, vol. 1, p. 38, 1908. sTRemnitzer, W., The Chittenden earthquake of July 24, 1921 : Seism. Soc. Ameri- can Bull., vol. 11, pp. 198-190, 1921. «8 Willis, Robin, op. cit., 1924. GEOLOGY ALLEN 51 Structures Within the Franciscan Belt The Franciscan belt in the northern part of the quadrangle averages 3 miles in width, and is bounded on the northeast by the Carnadero and on the southwest by the Sargent faults. Serpentine cold intrusions parallel and are adjacent to both fault boundaries throughout much of their course. The northeastern slopes of the Santa Cruz Range are composed of steeply northeast-dipping Franciscan sediments, and underlying basalts and agglomerates form the highest peaks along the Franciscan ridge. South-dipping sediments form the other flank of an east-plunging anti- cline which is cut off on the southwest by the Sargent fault. East of the Sargent oil field, the Franciscan rocks are overlapped by Pliocene. The Castro fault, which cuts across the Franciscan anticline at a low angle, approximately parallel to and 1| miles southwest of the Carna- dero fault, offsets the axis of the anticline, the area south of the fault being moved half a mile to the northwest. It forms the contact between Franciscan sediments and agglomerates over the eastern part of its course, it offsets the basalt flows 1 mile west of Hill 1982', and its course is marked by aligned drainages, sharp saddles, and disturbed attitudes in adjoining rocks. Beyond the northern edge of the quadrangle, it apparently joins the Sargent fault ; it cannot be traced to the southeast of Castro Flats and probably dies out rapidly. A parallel fault upon which recent movement has taken place lies a quarter of a mile southwest of the Castro fault along the northern por- tion of its course, and probably joins it near the north edge of the map. This fault is expressed by the alignment of drainage, by sharp saddles, and at one point east of Hill 1749' b}^ a 10-foot scarp with the north side down, lying across a high saddle. Several branch faults cut across the southern part of the Franciscan area, joining the Sargent fault from the east. They are discussed with the Sargent fault. Transverse Faulting Within the Franciscan Belt Only those transverse faults within the Franciscan area which have offset sedimentary beds or lavas or have definite physiographic expres- sion were mapped, although there are frequent indications that there are many more. Transverse faults which occupy the first two canyons west of Babbs Canyon offset both the basalt contacts near the crest of the ridge and the narrow zone of serpentine at the foot of the hill. They bound a block less than half a mile wide which has been raised relative to the adjoining terrain, and the faults form deep narrow troughs where they cross the crest of the ridge. The western fault may be offset to the west and continue south of the Castro fault, where a deep trench cuts across the slope of the ridge forming a well-defined kernbut and kerncol.^^ Upward movement of the south side of the fault for a distance of about 100 feet would account for the break in topography. Much of the folding and faulting in the Franciscan belt undoubtedly took place during the upper Miocene-lower Pliocene orogeny, although probably some occurred during the upper Pleistocene as well. There ^° Lawson, A. C, The geomorphog'eny of the Upper Kern basin : Univ. California, Dept. Geol. Sci., Bull., vol. 3, pp. 331-343, 1904. 52 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 has been a slight amount of recent activity, producing' the small scarps and saddles present at a number of places within the area. Sargent Fault The Sargent fault zone extends approximately N.55°W. from a point Avest of Sargent Station to beyond the edge of the map. Further work in the Morgan Hill and New Almaden quadrangles may show that it is a part of the same zone of thrusting that produced the Pilarcitos and Uvas Creek faults. Southeast of the Sargent oil field the fault cuts through Pliocene deposits and passes into the Sargent anticline, to dis- appear in the landslide topography on the north flank of Lomerias Muertas. Northwest of the oil field it forms the contact between the Franciscan and Monterey belts. A branch of the fault trending east from Sargent Station would explain the presence of the serpentine in the north foothill spur of Lomerias Muertas. The Sargent fault zone is from a few tens of feet to about 500 feet in width, at places exhibiting one or more small ridges and troughs. A soil ridge 2 feet high, at a point 1^ miles from the north edge of the map indicates slight recent movement. Springs are common throughout its length, and serpentine has been squeezed up as cold intrusions along much of its course. Minor changes in the trend of the fault as it passes over ridges and across canyons suggest steep dips to the north at many places, and dips to the south at a few others. Franciscan rocks on the northeast have been thrust up at least 3000 feet against the Monterey sandstone on the southwest. Pliocene rocks, which are found on both sides of the fault east of the Sargent oil field have been displaced about 600 feet in the same direction, as shov^oi in sections and well logs. Branches of the Sargent Fault A branch of the Sargent fault leaves the upper course of Pescadero Creek and cuts eastward through a low windgap in the Franciscan rocks across the lower end of Castro Flats, Avliere it apparently splits again. One of these branches may run through a low gap to join the Castro fault, other branches cross the hills to the southeast where, near the center of section 25, two fault trenches 50 to 100 feet wide and 10 to 20 feet deep trend S.60°E. across successive ridges, the spurs to the north of the faults being offset horizontally from 250 to 300 feet to the southeast. Small ponds, springs, and undrained hollows appear in the trenches. The faults can be followed for about a mile, but disappear to the southeast. Another important branch of the Sargent fault runs easterly from a point half a mile north of the oil field. It follows the creek which lies north of La Brea Creek, runs 100 feet north of the lower course of La Brea Creek, and under the terrace at its mouth. It is marked by steep and anomalous dips in the Pliocene rocks, three small outcrops of serpen- tine, and five brea seeps. The earliest recorded movement on the Sargent fault took place during the upper Miocene-lower Pliocene orogenic epoch, and most of the movement took place at that time. Repeated movement in the same direc- tion but to a lesser degree accompanied the folding of the Pliocene rocks in the lower Pleistocene. There has been some slight activity on the Sargent fault and on its tributaries in recent times. GEOLOGY — ALLEN 53 Structures Within the iVliocene Belt The belt of Monterey sandstones and shales averages 3 miles in width. It is bounded on the northeast by the Sargent fanlt and the Franciscan belt ; on the southwest by the San Andreas fault. The south- eastern end is overlapped by Pliocene sediments whose structures will be discussed separately. To the northwest of the mapped area, near Loma Prieta, a thick series of Cretaceous conglomerates and sandstone occupy most of this belt.^oo The Miocene belt is the most closely folded portion of the area mapped. At many places the diatomaceous shales and sandstone are isoclinally folded and even overturned. Attitudes of less than 40° are uncommon. The axes of the folds generally trend N. 65-75° W., at a slight angle to the bordering faults which trend N. 50-60° W. Within a quarter to half a mile of the Sargent fault, the rocks are broken and disturbed, and the axes of the folds approaching the fault at several places swing around to the east and northeast, to meet the fault at a high angle. The Shale Mountain syncline, recognized and named by Jones ^^^ for the southwesterly spur of Mount Pajaro, is the most prominent fold, since its axis approximately follows the crest of the ridge through Mount Pajaro and Atherton Peak, which are composed of upper Monterey diatomaceous shale. Farther northwest along the ridge where it is composed largely of massive sandstone, the course of the fold is obscure. There are four tightly folded, southeast-plunging synclines and intervening anticlines between the Shale Mountain syncline and the Sargent fault where it crosses upper La Brea Creek. One additional prominent syncline and adjacent folds appear farther west. Some of the folds do not extend far ; others may be traced for as much as 3 miles. Folds within the sandstones west of the Sargent oil field have been plotted by means of attitudes on the included lenses of buff-colored limestones ; farther nortli these lenses are scarce or absent, and mappable attitudes are few. Undoubtedly there are folds within this area which have not been mapped. Faulting within the Miocene belt is also difficult to determine. A fault with the north side do^vn probably parallels Pescadero Creek for 2 miles or more. The south wall of the creek for this distance is composed of Monterey sandstone, and the north bank is steeply dipping shale, presumably belonging much higher in the section. Attitudes are steep and overturned, and two breas occur along the creek. Local faulting and disturbances of dip occur at a number of other places. Local folding occurs along a southwest-dipping thrust fault exposed in the highway cut on the San Jose road near the north edge of the map. Farther south along the highway there are similar areas where the rocks are highly disturbed. Faulting has displaced blocks adjacent to the San Andreas fault in at least three places, on the San Jose high- way 1| miles northeast of Casserly School, on the spur west of Atherton Peak, and south of Mount Pajaro. This last fault probably continues up Pajaro Canyon, since structures south of the river do not correspond with those on the north. ^"Gilbert, C. M., personal communication, 1945. 101 Jones, W. F., op. cit., pi. 18. 54 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Transverse faulting appears at several places. The abrupt change in the width of the diatomaceous shale belt just north of Atherton Peak and the deep saddle across the ridge at this point both indicate a fault with the south side dropped dowa at least 500 feet, but its course could not be accurately determined. The right-angle bend in Pescadero Creek 1 mile northeast of Atherton Peak, combined wdth the abrupt cut-off at the creek of a shale belt in the sandstone north- of the creek are both suggestive of the continuation to the northeast of this transverse fault. Structures in the Pliocene Northeast of the San Andreas Fault The basal conglomerates of the Purisima formation overlie the southeast end of the Franciscan and Monterey belts with a 90-degree angular unconformity. In the ridge just south of the Sargent oil field, the Monterey shales strike east and stand nearlj^ vertical, the overlying Pliocene sands and gravels which cap the ridge strike north to northeast and dip 20 to 45 degrees to the east and southeast. Attitudes in Pliocene rocks are usually difficult to obtain. Outcrops are not common, and the conglomerate members are either poorly bedded or cross-bedded. A few of the more resistant members stand out physio- graphically as on the south side of the Lomerias Muertas, and at certain times of the year "grass-dips" appear on the water-carrying beds. Plotted attitudes in the area between the Pajaro River and the Sargent fault nearly alwaj^s have southerly components, with the exception of a few north dips near the river, which outline an east-plunging syncline whose axis passes through Betabel Station. North of the Sargent fault and 1 mile north of Sargent Station, an east-plunging sjmcline is cut off on the west by the fault. The dips in the north slopes of Lomerias Muertas and just south of Sargent Station are to the north and northeast. North of La Brea Creek the Pliocene is crumpled into four closely spaced folds which strike a little north of east. The first ridge north of the creek approximates an anticline, the next small valley is synclinal in nature. Between the valley and the Franciscan contact a third of a mile farther north, there are two more folds in the basal red conglomer- ates, with dips up to 45 degrees. A small north-trending anticline passes through the ridge just south of the Sargent oil field, and may be accom- panied by faulting.^'^2 It is probably responsible for the accumulation of the oil in this field. Faulting within the Pliocene area is undoubtedly present but can not be localized with an}- degree of certainty. Various geologists have postulated a fault trending north-northeast up the creek half a mile west of the Pajaro River north of Betabel. An abrupt change in attitude appears 1 mile south of the Sargent oil field, and its projection eastward would explain the apparent abrupt change in strike of the beds. ■Jones ^^^ interpreted these features as an unconformity within the group, but the writer has traced a bed of shale-conglomerate across the proposed fault and unconformity, and believes that it only represents a sharp eastward bend in the strike of the south and southeast-dipping strata. _ The ridge of Pliocene rocks which lies south of the Pajaro River is anticlinal, but the beds are highly disturbed as they near the San Andreas fault on the south or the river on the north. Structures in the highway i02Michelin, J., op. cit, p. 476. fig-. 200, 1943. ii^ Jones, W. F., op. cit., pi. IS. GEOLOGY ALLEN 55 cuts along the river are at right angles to those north of the river, strongly suggesting the presence of a fault paralleling the course of the Pajaro River from Betabel westward. structures in the Santa Cruz Range Southwest of the San Andreas Fault The mile-wide belt of foothills lying north of the Pajaro River and just west of the San Andreas fault is composed largely of Pliocene rocks, dipping southwest from 20 to 60 degrees and overlapping both Monterey and granite. West of the fault, 3 areas which have been mapped as Monterey are composed of Monterey sandstone and carbonaceous shale, but the rocks are so badly broken and there is so much landsliding that it is possible that they may have come down the hill across the fault in past landslides. Several faults from the west expressed by fault troughs, lines of saddles, and springs, join the San Andreas fault at acute angles. It is impossible to determine the amount or direction of movement upon these faults, there being no good marker horizons in the Pliocene rocks of this part of the area. A north- or northeast-trending fault, with the east side down at least 400 feet, has brought Pliocene rocks against Monterey sandstones and shale in the lower Pajaro Canyon, about 14 miles north of Aromas. A synclinal axis in the Purisima gravels which strikes N. 60° "W. in the extreme northwest corner of the quadrangle, crosses the Hazel Dell road half a mile north of Casserly School. Gabilan Range Introduction Faulting is predominant over folding in the ' ' thin-blanketed ' ' area of lower Tertiary rocks southwest of the San Andreas fault zone. Not only is faulting predominant, but the rocks are so complexly faulted, on such a small scale, that many of the details of structure cannot be shown on a. 1 :62,500-scale map, and many of them, as was observed by Kerr and Schenck,^^^ cannot be deciphered in the field even with the aid of the easily identifiable "red beds" horizon. In the Tertiary area southwest of San Juan Bautista there are four chief thrusts which trend towards the San Andreas fault from the northwest and west, as well as several branches of these thrusts. The belts between them have been broken by a number of transverse faults into what may be called "thrust blocks", to distinguish them from ' ' fault-blocks ' ' resulting from normal faulting. Most of the faults of this complex system may be resolved into three sets : 1. The main curved thrusts (from the south) which have southeast trends, and swing eastward to meet the San Andreas fault. 2. North-trending- faults, usually with their west sides down. 3. Northeast-trending faults, usually with their east sides down. Although Reed ^^^ questions the predominance of faulting and fault- block features anywhere in the Coast Ranges, detailed work in this area failed to disprove the presence of those structural features which were first outlined by Kerr and Schenck.^"^ w^Kerr, P. P., and Schenck, H. G., op. cit., p. 480, 1925. 103 Reed, R. D., op. cit, pp. 49-53, 1933. "8 Kerr, P. F., and Schenck, H. G., op. cit., 1925. 56 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Anzar Buried Fault One mile northwest of San Juan Bautista, San Lorenzo rocks overlie granite; at Pajaro Gap 5 miles farther north, Monterey sandstone and shale lie directly upon granite. Such a relationship suggests a fault, which is believed to lie at a slight angle to and west of the San Andreas fault, joining it a few miles north of San Juan Bautista. Movement of this fault must have occurred in post-Vaqueros and pre-Monterey time, probably at the same time as the first movements on the Vergeles fault. The northeast side of the fault moved up at least 3000 feet and the San Lorenzo and Vaqueros rocks were eroded before deposition of the Mon- terey. The alternate hypothesis is that the San Lorenzo sea was very narrow and did not extend as far northeast as this point. The fine- grained character of much of the San Juan Bautista formation does not favor this concept. Cement Works Fault The northernmost of the well defined thrust faults south of the San Andreas trends north of west from the cement works 1 mile south of San Juan Bautista, along the base of the main escarpment to a point 1 mile northeast of Pinecate Peak. It is expressed structurally as well as physiographically, since north of the fault the dips in the San Lorenzo rocks have easterly components, while to the south of the fault the rocks in the main ridge all dip to the southwest. To the northwest the fault passes beneath the Aromas sands; to the southeast it appears to join the San Andreas. Half a mile west of the cement works a transverse fault offsets it several hundred feet to the south, and it may be similarly offset by other cross-faults farther west. The amount of thrusting from the south on the Cement Works fault could not be determined. The age of the faulting on this and the County Line and Pinecate faults is post-Vaqueros and pre-Aromas, and prob- ably took place during either the upper Miocene-lower Pliocene or the lower Pleistocene epochs of orogeny. Pinecate Fault The red beds in the main ridge extending southwest from Pinecate Peak dip from 12 to 30 degrees to the southwest. They are in fault contact on the south with massive sandstones which dip 35 to 65 degrees in the same direction. A few dips measured near the contact were 80 degrees to vertical. The fault bounding the red beds on the south is offset by small cross faults 1 mile southeast of Pincate Peak. South- eastward it cuts througli the gap south of Hill 1000' where it splits, one branch extending southeasterly, displacing the andesite contact about 400 feet down on the north side. Another branch extends easterly along the north edge of the main ridge to appear in the Avest wall of San Juan Canyon half a mile south of the cement works. Just south of Hill 1000', half a mile west of the San Juan grade on the north side of the main ridge, the Pinecate fault dips 32 degrees south; on the highway it is vertical. Along most of its course, Pinecate and Vaqueros sandstones are in fault contact against red beds, the ver- tical displacement on the north branch being determined at two places where the depositional contact between them is thrust up from the south 1200 and 1600 feet. GEOLOGY ALLEN 57 Transverse faulting has offset the north branch at three or more points, but only for distances of a few hundred feet or less. County Line Fault A well-developed fault valley extends east-southeast from Dun- barton, paralleling the Monterey-San Benito county line for about 2 miles. Southeast of the corner of Los Carneros grant, the fault runs just north of Hills 1280' and 1180', paralleling the north boundary of Los Vergeles grant at least as far as Hill 1417', where the slight dis- placement of the lavas indicate that it is fading out. The south side of the fault has been upthrust a distance varying from a few feet to over 400 feet west of Hill 1280'. Lavas have been dropped down on the north side of the fault, to occupy the crest of sev- eral north-trending ridges, well below the main southeast-trending ridge composed of red beds which normally underlie the lavas. Folding Southwest of San Juan Bautista The sediments in the thrust-blocks north of the County Line fault all dip to the south from 15 to 80 degrees. Between the County Line and Vergeles faults west of the San Juan grade, there is a well-defined, although faulted and therefore somewhat discontinuous anticlinal fold, which plunges to the northwest beneath the Aromas sands between Dun- barton and Pinecate Peak. The fold is asymmetrical, being steeper on the northeast flank, and is cut off by the Vergeles fault near the San Juan grade. East of San Juan Creek, there is an equally well-defined syn- cline which, although offset to the south as it crosses San Juan Creek, continues into the area of very thick red beds west of the creek, where the structure becomes obscured. Folding is reportedly unusual in areas with granitic basement ; here it is undoubtedly a result of the movement on the Vergeles thrust, and appears only in the upper portion of the 3500-foot section of lower Tertiary rocks. Vergeles Fault The most prominent fault in the area southwest of the San Andreas is the great curved Vergeles fault, which cuts across the northern part of Los Vergeles grant and has thrust up the granite of the Gabilan Range against lower Tertiary sediments and lavas for a distance within the quadrangle of 10 miles, from Dunbarton southeasterly to the edge of the map. The fault plane itself is best observed 1 mile east of the summit of the San Juan grade, where it cuts rhyolite and the face is exposed for several hundred yards, striking N. 60-80° AV. and dipping 70-80° S. Striations and grooving in the rhyolite are vertical. Elsewhere the fault trace can be followed easily, not only by the abrupt contact between rocks of widely different age and character, but by zones of breccia, deep saddles and troughs, and by sharp folds in the adjoining Tertiary rocks. Minimum vertical displacement on the fault is at least 3500 feet, the total being undoubtedly much more. No residual patches of Tertiary rocks are found on the granite south of the fault ; the entire San Lorenzo, Vaqueros, and volcanic groups (and possibly younger rocks) have been completely eroded. 58 SAN JUAN BAUTISTA QUADRANGLE [BuU. 133 In three places the Vergeles fault is offset an average distance of 800 feet by later transverse faults. In two of these cases the west side is moved to the north, in one case (three-quarters of a mile west of Gabilan School) the west side is moved south. There are several branches of the Vergeles fault which take off from the main fault at low angles to form thrust ' ' splinters ' ' up to half a mile wide, duplicating portions of the Tertiary sequence. The displacement on these tributary thrusts is in the order of hundreds, rather than thou- sands of feet. It has been previously noted that the volcanic rocks are restricted to a zone everywhere within 1 mile of the Vergeles fault, the red beds also lying less than 2 miles from the fault. The presence of known vol- canic vents near the fault, and the character of the red beds suggest that they are both genetically related to the faulting. It is believed that the red beds represent a fanglomerate or were derived from erosion of the fault escarpment, and that later movement permitted the extrusion of the volcanic group. The original movement on the Vergeles fault, there- fore, occurred in Vaqueros (Zemorrian) time and continued in post- Vaqueros (Saucesian?) times. It is probable, although not determin- able within the area, that movement was renewed during the upper Miocene-lower Pliocene orogenic epoch. Possibly the movements on the parallel faults took place during this later epoch. Transverse Faulting Numerous transverse faults have offset the lower Tertiary rocks and in places the longitudinal thrust faults in the area west of San Juan Bautista. These faults have two fairly well-defined trends, the west sides of the north-trending faults have moved down, the west sides of the northeast-trending faults have moved up. Where the fault planes can be observed, their attitudes and the direction of movement shows that they are thrusts, as on the top of the ridge 14 miles southeast of the cement works, where the red beds have been thrust up from the northwest over volcanics, along a fault which strikes N. 60° E. and dips 57° NW. Striations on the fault plane, how- ever, strike N. 10° E., indicating that the movement has actually been more horizontal than vertical. This fault extends southwest into the granite area where it offsets Gabilan limestone. Displacements along these faults range from 150 to over 800 feet, but do not appear to be much greater, with the exception of the fault up San Juan Creek. Generalizations as to the age and direction of movement of the trans- verse faults are difficult to make. Usually they do not appear to cross and offset the longitudinal thrusts, but there are several notable excep- tions which have already been mentioned. Probably most of the fault- ing, with the exception of the movements along the Vergeles thrust in the lower Miocene, took place during the upper Miocene-lower Pliocene orogenic epoch. Faulting Within the Granitic Area South of the Vergeles fault and west of Gabilan Creek, the Aromas sands overlie the granite. In the area north and east of Langley School the sands have been faulted down into the granite at a number of places, as is indicated by the irregular contacts of the granite "windows," by GEOLOGY ALLEN 59 the presence of springs, and by the occurrence of small recent fault rifts, one of which occurs 1 mile due north of Langley School, striking N. 25° W. Another such fault, striking N. 50° W. and dipping 40° NE., appears in the highway quarry at the road forks half a mile northeast of Langley School. Aromas sand is dropped down on the northeast against granite. As has been recog-nized by Kerr and Schenck,^"^ -faulting undoubt- edly extends farther south into the granite area, where stratigraphic criteria are usually inapplicable. There is a strong physiographic suggestion of a continuation of the zone of faulting north and east of Langley School still farther to the southeast and up the remarkably straight course of Gabilan Creek. Concordant ridges slope gently west to the creek, whereas the ridge west of the creek has a steep east and a much gentler west slope, standing relatively several hundred feet higher than the slope east of the creek. South of the edge of the quadrangle there are a number of springs along the creek which contribute to its all-year flow. Minor faults parallel to this Gabilan Creek zone offset the limestone in Sugarloaf Peak and the hill just south. Displacement is about 30 feet on each of three faults, which appear to be thrusts with the southwest side moved up. A small branch fault lies a quarter of a mile east of Gabilan Creek, appearing as a line of saddles and spurs, with springs in the valleys where they cross the fault, and soil and plant changes on the two sides of the fault. It is entirely possible, if the Gabilan Creek zone represents a major fault along which the recent movements have taken place, that the earth- quake of December 27, 1924, whose epicenter was reported ^"^ to lie northeast of Salinas, was a result of movement along this fault zone. The existence in the granite area of a system of faults with north- easterly trends is suggested by the step-like nature of the ridge tops extending northward from the main Gabilan Peak ridge. It is believed that the decrease in elevation of the range in this region may be due to this faulting, with the downthrow side on the northwest, rather than entirely to the downwarping suggested by Robin "Willis.^"^ In Steinbach Canyon the contact between southwest-dipping Sur series quartzites and schists and the granite is offset over a quarter of a mile by a northeast-trending fault parallel to the canyon, the southeast side having been moved relatively to the northeast. A similar fault may follow the course of Queen Canyon. One mile northwest, the northeast- trending fault which forms the contact between the rhyolite and the red beds east of San Juan Creek extends into the granite and offsets the line of Gabilan limestone. The age of the faulting in the granite area can not be determined with any certainty. Around Langley School there has been post-middle- Pleistocene movement, and it is probable that faulting in the Gabilan Range has disturbed the lower Pleistocene erosion surface. if^Kerr, P. F., and Schenck, H. G., op. cit, 481-482. 108 Kemnitzer, L. E., The Salinas earthquake of December 27, 1924, (California) : Seism. Soc. America, Bull. 14, pp. 2.30-231, 1924. 109-vp-illis, Robin, op. cit., p. 670, 1925. 60 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Structural History Introduction The histoiy of pre-Tertiary cliastrophic events that took place within the San Juan Bautista qiiadrane^le is similar to that of the central Coast Rang'es as a whole but there are several minor differences. These differ- ences will be brought out in the following discussion. Pre-Oligocene Faulting The earliest structural event of which there is record is the initiation of the ancestral San Andreas fault, which coincides closely throughout the San Juan Bautista quadrangle Avith the present line of rifting. The northeast side was dropped a minimum of 10,000 feet, bringing the Franciscan into juxtaposition with the granite southwest of the fault. This faulting, probably normal in character, first divided the area into two structural provinces. It occurred, judging from evidence outside of the area, in the Eocene. Lower Miocene Faulting There is reasonable evidence for faulting during lower Miocene time in the San Juan Bautista quadrangle ; movement at this time is one of the minor points of difference in the structural history of this region and the central Coast Ranges in general. However, movements during the lower Miocene in the Coast Ranges of ('alifornia are known to have taken place in other areas and hence the local area under discussion is not unique in this respect. The Vergeles fault may have had its beginning at this time but the evidence is not conclusive. The coarse debris in the Miocene beneath the volcanics indicates steep slopes that may have resulted from faulting. Some movement (downthrow on the east) took place on the ancestral San Andreas fault at this time, as the thickness of lower Monterey Band- stones west of the fault is much less than on the east. Upper Miocene or Lower Pliocene Folding and Faulting A very important period of folding took place after the deposition of the Miocene sediments of the area and the deposition of the middle Pliocene. Movement took place along the Carnadero and Sargent faults and possibly along the Castro fault. The Monterey Bay dovmwarp and Pajaro channel were also initiated during this time, permitting influx of the sea into the San Benito-Santa Clara trough. There is clear evidence that strong movement took place along the Sargent fault, either in the late Miocene or early Pliocene, as the Purisima formation rests on the Franciscan on the northeast side of the fault and on Miocene sediments on the southwest side. There appears to have been some continued uplift of the west Bide of the ancestral San Andreas fault, and much of the faulting in the lower Tertiary rocks west of San Juan Bautista may have taken place at this time. Late Pliocene or Early Pleistocene Folding and Faulting ^ The Santa Cruz Range was again subjected to compression resulting m folds whose axes trend more w^esterly than those resulting from the previous erogenic epoch. Thrusting was renewed on the Sargent and possibly on the Pescadero Creek and Carnadero faults. The transverse GEOLOGY — ALLEN 61 faulting ill the north end of tlie Gabilan Range may have taken place at this time. Middle or Upper Pleistocene and Recent Deformation and Active Faulting Several stages of uplifts, submergence, and tilting took place in the Gabilan Range, followed by recent. faulting of small magnitude. Hori- zontal displacement of 1 mile occurred along the San Andreas fault. These movements are described in greater detail under geoniorphology. GEOMORPHOLOGY Introduction Major faults, more or less parallel to the San Andreas fault, have strongly influenced the physiography and drainage, both by relative movements of the blocks between them or by folds produced in them. The sculpturing of the ranges has been strongly affected by the zones of weakness resulting from the faulting and folding. Drainage The Pajaro River flows westward from the wide Santa Clara-San Benito Valley and cuts between the two ranges across the center of the quadrangle to flow into Monterey Bay. Llagas Creek, which drains the Santa Clara Valley as far north as Morgan Hill, joins the Pajaro 4 miles northeast of Sargent Station. Several authors ^^^ have concluded on physiographic and fresh-water faunal evidence that the Santa Clara Valley has drained alternately in San Francisco and iVIontere}'^ Bays. It would be very easy for Coyote Creek to take a southern rather than a northern course across its great alluvial fan to Llagas Creek and the Pajaro River. Before the Pajaro River enters its narrow canyon, it is joined by Carnadero, La Brea, and Pescadero Creeks, which drain the eastern slopes of the Santa Cruz Range, by the San Benito River, draining ihe main valley to the southeast, and by San Juan Creek, which drains a part of the east side of the Gabilan Range. Pescadero Creek offers a good example of a drainage sj^stem governed by erosion along fault zones. Its upper course follows the Sargent fault for 2 miles, then turns 90 degrees and for 1 mile follows a cross fault. The next four miles of its southeast-trending course probably parallels another fault. After passing through Pajaro Canyon, the river meanders across the wide, terraced Pajaro-Corralitos Creek valley to join Monterey Bay 3 miles west of the edge of the map. A number of short streams flow down the steep westerly slopes of the Santa Cruz Range into this valley, crossing and being offset to the north by the San Andreas fault. Several are per- manent streams within their upper canyons, but become intermittent or are lost altogether when they flow out on the fans and terraces of the valley. The central portion of the quadrangle drains directly into the sea bj^ way of the wide, terraced, and oversized "Elkhorn Valley" and slough, 110 Branner, J. C, A drainage peculiarity of the Santa Clara Valley affecting fresh water fauna : Jour. Geology, vol. 15, no. 1, pp. 1-9, 1907. Clark, W. O., Ground water in Santa Clara Valley, California : U. S. Geol. Survey, W'ater-Supply Paper 519, p. 64, 1924. 62 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 undoubtedly the Pleistocene course of the San Benito River across the area. The channel of this stream was never much more than 50 feet deeper than at present, except along the western few miles of its course, as the terrace gravels are thin and bedrock appears beneath them at a number of points. The southern portion of the quadrangle is drained by several short creeks flowing due west to the coastal sloughs, by the tributaries to San Miguel Canyon, which flows south and then west to the bay, and by Gabilan Creek and its tributaries, most of which head in the Gabilan Range and flow out on and are dispersed in the alluvium and terraces of the Salinas Valley to the south. Except in the area of gently west-dipping Aromas sands, where the streams have consequent, or like San Miguel Canyon, subsequent courses, most of the drainage patterns in the quadrangle are irregular, following zones of faulting and cutting across other structures. The Pajaro River between Sargent Station and Betabel may be antecedent, if it pursued the same course previous to the lower Pleistocene folding of the rocks of Lomerias Muertas. Its course through the lower canyon, judging from the terraces at about 400 feet elevation, was cut into the granite, and was then moved northwest against the precipitous buttress of Mount Pajaro by horizontal movement of the San Andreas fault. Cycles of Erosion Although the extensive Pliocene and Quaternary movements in the San Juan Bautista quadrangle and the resulting erosion have obliterated much of the evidence of old physiographic features, an erosion surface older than those developed during the present c^^cle can be recognized in a number of places, and some attempts have been made to correlate and date it.^^^ As in the San Benito quadrangle to the southeast, ^^- there is good evidence for at least two cycles of erosion, the second in places being divisible into substages. The Gabilan Range within the quadrangle is a faulted and tilted granite block. Its general back-slope is to the west, while the northern end of the range is either warped down or dropped by a succession of small faults. The crest of the high east-trending ridge of Gabilan Peak stands at an elevation of 3169 feet, several hundred feet above a west- sloping surface which forms benches on both the north and south flanks of the ridge. This surface is preserved in a few places along the crest of the ridge north of the peak, dowm to an elevation of 1700 feet, as well as on several concordant ridges farther west. High-level valleys refer- able to this cycle of erosion are well preserved in the Gabilan Range of the Salinas and Gonzales quadrangles to the south. ^^^ The wide high troughs at about 1000 feet elevation along the crest of the sedimentary hills southwest of San Juan Bautista have a relief above them of about 300 to 400 feet, and also, as suggested by Willis,^^^ represent high-level ^11 Willis, Robin, The physiography of the San Andreas fault between Pajaro Gap and the Cholame Plains, unpublished PhD. thesis, Stanford University, 1924. Willis, Robin, Physiography of the California Coast Ranges : Geol. Soc. America Bull., vol. 36, pp. 641-678, 1925. 112 Wilson, I. F., op. cit, pp. 191-192, 1943. "3 Wilson, I. F., op cit., 1943. WillLs, Robin, op cit., 1924 and 1925. 114 "Willis, Robin, op cit., p. 670, 1925. GEOLOGY ALLEN 63 valleys of the same cycle. This surface coincides with the highest eleva- tions of the Aromas red sands, which slope westward to sea level from a maximum elevation of 800 feet on the flanks of the northern end of the range. In the Santa Cruz Range the first-cycle surface is well preserved at a number of places along the crest of the 1400 to 1700-foot ridge north of Mount Pajaro, as well as on its west-sloping spurs. East of the main ridge there are wide areas in Monterey sandstone where this late-mature surface appears, with several wide and in one case alluviated high-level valleys upon it. The maximum elevation of the surface is in Hill 1751', just east of Bodfish Creek, and it slopes gently to the southeast to an elevation of 900 feet a mile west of Sargent oil field and to 670 feet east of Chittenden. Pescadero and Bodfish Creeks and their tributaries are incised in youthful canyons in this surface, leaving a few spurs on the flanks of the higher ridge to the west. In the Franciscan area north of the Sargent fault the general eleva- tion and relief are greater, and only suggestions of the old surface remain. The first cycle of erosion was developed during the lower and middle Pleistocene, when the land stood much lower than at present, and the Aromas red sands were deposited during the same epoch. The second cycle of erosion, resulting from differential uplift of 600 to 2500 feet, occurred in at least 2 substages, with an intervening period of submergence. It has resulted in the rejuvenation of nearly all the streams, which are still youthful throughout all but their lower courses. Castro Flats and the small alluviated area to the east may represent the first substage, but it is also possible that a reversal of movement on the north fork of the Sargent fault dammed the drainage north of the fault. Near the northern edge of the map the Sargent fault passes beneath a remnant of the first-cycle surface without disturbing it, however. Summary of the Quaternary Record Following the uplift w^hich brought the first cycle to a close, the Pajaro and San Benito rivers were incised in separate channels across the ridge west of the San Andreas fault, and subsequent submergence of about 250 feet caused both of their valleys to be filled with terrace gravels. Faulting was renewed on the San Andreas, with repeated uplift of the area to the west, totalling over 150 feet, and consequent disturbance of the terrace elevations on opposite sides of the fault. Following this uplift, the Pajaro River cut down into the sheared and broken granite more rapidly, due to plucking, than the San Benito River was able to do in the massive San Lorenzo sandstone along the course of Elkhorn Valley, and the Pajaro captured it through the gap at Chittenden Junc- tion. The Pajaro River at this time was probably augmented by the Coyote Creek drainage, and was able to maintain its course across the granite ridge in spite of the uplift. Lateral movement of 3800 feet on the San Andreas fault may have occurred at this time, or may have taken place at a later time. The high terraces were dissected during the period of intermittent uplift, and several lower terraces were formed at different stages. The 64 SAN JUAN BAUTISTA QUADEANGLE [Bull. 133 lakes on the two north-trending canyons southwest of Aromas were dammed by the gravel fill of one of the later terrace stages. These terraces correspoiid in general with the lower wave-cut ter- races in the Santa Cruz quadrangle, which are reported ^^^ to occur at elevations above sea level of 20 to 100 feet, and at 250 feet. It isi dangerous, due to prevalence of differential movements, to correlate ter- races over even such short distances. The series of lakes north of Watsonville were formed by a "flood" of recent alluvium from an overloaded Corralitos Creek, which dammed the mouths of small valleys incised a few feet in the low terraces of the Pajaro-Corralitos Valley.^^^ The last land movement in the area was a submergence of from 50 to 150 feet, with alluviation of the Pajaro River and its chief tribu- taries. The recent rejuvenation and incision of the main streams into their flood-plains 20 to 40 feet is more likely due to climatic than to base-level changes. Monterey Submarine Canyon No discussion of the geomorphic history of the San Juan Bautista area would be complete without a consideration of the submarine canyon mapped and described by Galliher ^^''' and by Sheperd and Emery.^^^ The latter ^^^ ascribe the development of the deep outer trough which forms the continuation seaward of the inner Monterey Canyon beyond depths of 9000 feet to ' ' some early sea-floor diastrophism which resulted in development of fault troughs with a north Avest-southeast axis. ' ' They suggested that the inner canyon was cut prior to late Pliocene as a result of general elevation of this portion of the coast, following which the coastal area sank until the canyon reached its present outer depth of 9000 feet. Elevation of the land by some 2000-3000 feet during the Pleistocene then allowed rivers from the land to flow into the re-exposed heads of the old submarine valley. After the upper canyon was cut, during this pre-Wisconsin epoch, it was again submerged. During the Wisconsin ice epoch the inner ends of the canyon were again exposed b}' emergence and eroded down to about 300 feet. Elkhorn Slough was excavated during this lesser lowering of the sea level. The pre-middle Pliocene epoch of folding and uplift was pro- nounced in the area east of the bay. Faulting was extensive, and it is quite probable that such a deep trough was formed, just as the Salinas and San Benito troughs were deepened at this time. The east-trending Monterey-Pajaro seaway was initiated at this time, to be later filled with Pliocene sediments. General elevation of this part of the coast began perhaps during late Pliocene, but did not become important until late Pliocene or early Pleistocene, when the Purisima formation was folded and elevated. Certainly the land as a whole did not sink 9000 feet following this orogenic epoch, since deposits laid down during such a submergence would undoubtedly be found somewhere in the area. Later Pliocene iisBranner, J. C, Newson, J. F., and Arnold, Ralph, op. cit, p. 6. 1909. 118 Beard, C. N., op. cit., 1941. '^'' Galliher, W^ayne, Sediments of Monterey Bay, California : California Min. Bur. Kept. 28, no. 1, pp. 43.-79, 1932. ii8Shepard. F. P., and Emery, K. O., Submarine topography off the California coast: Geol. Soc. America, Spec. Paper, no. 31, 1941. us Idem, p. 155. GEOLOGY ALLEN 65 or early Pleistocene uplift probably did raise the area as much as 2500 feet, possibly even more. Following this period of folding the land was above sea level long enough for it to be reduced to the first-cj^cle stage of late maturity, remnants of which still appear, and the Aromas sands filled much of the basins to the west and south of the quadrangle. Differential elevation of the land did occur during the upper Pleis- tocene, but it was of the order of 600-2500 feet, and due to tilting rather than to eustatic uplift. Probably the key to the apparent great sub- mergence of the Monterey Bay area lies in this tilting and downwarping of the bay region, which is also evident in the tilted block of Ben Lomond Mountain north of Santa Cruz. Uplift of 2500 feet in the Gabilan Range may have meant downwarp in the center of the bay of an equivalent or even greater amount. No channel 2000 feet deep was cut through the quadrangle, unless, as suggested by the writers, its course was southward up the Salinas Valley, and is' now masked by the deep alluvium cover there. This elevation did allow the rivers, in particular the "Elkhorn River, ' ' to flow into the heads of the submarine valley, but they did not cut it to any great depths below present sea level. The postulated pre- Wisconsin submergence corresponds to the substage of terrace gravel filling, and the Wisconsin uplift corresponds to the substage of terrace cutting. This substage was associated with tilting which may have fur- ther depressed the canyon in the bay. Recent submergence of 50-150 feet completes the diastrophic record. PALEOGEOGRAPHY Introduction The geologic study of the San Juan Bautista quadrangle sheds a little additional light upon paleogeographic conditions, although only the coor- dinated results of researches over a large area can give authenticated results. The Pliocene "San Benito trough" ^^^ was undoubtedly con- nected with the sea by way of the Monterey Bay-Pajaro depression, but evidence within the area is not so conclusive for its existence in the Eocene, although a restricted Oligocene seaway appears to have extended through the area. Pre-Tertiary There is little evidence as to whether the Franciscan (upper Juras- sic) rocks once covered the Gabilan Range or not. Only a few small patches of conglomerate suggestive of shore-line conditions were observed in the Franciscan area. Cretaceous sediments with large amounts of conglomerate appear both to the northwest in the Santa Cruz and to the southeast in the Diablo Ranges, but do not outcrop within the area. It is probable that the area was submerged in the pre-Tertiary Coast Range syncline during much of Jurassic and Cretaceous time. Eocene The minimum extent of the Eocene seaway is mapped by Wilson ^-^ as extending northwest from the San Joaquin Valley through the ' ' Butts 1^ Clark, B. L., Tectonics of the Coast Ranges of middle California: Geol. Soc. Amerca, Bull. vol. 41, pp. 747-828, 1930. Reed, R. D., San Benito trough : Geol. Soc. America Proc. for 1937, pp. 247-2.50, 1938. Wilson, I. P., op. cit., p. 260, 262, also flg. 11, p. 229, 1943. 121 Wilson, L F., op. cit., p. 229, 1943. 5—51298 66 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Rancli-Vallecitos trough" to a point immediately south of Hollister. Eocene rocks are present west of Salinas, and in the Santa Cruz quad- rangle to the northwest, and they have recently been found ^^^ in the Diablo Range northeast of Morgan Hill. Eocene rocks do not appear in the San Juan Bautista quadrangle, where the Oligocene rests upon granite. It is possible that the Eocene seas did not extend across the area, but that they occupied separate seaways east and west of the uplifted Gabilan Range. Oligocene — Lower Miocene The Oligocene embayment, which was wider and deeper to the north- west, gradually became more and more restricted with a corresponding coarsening of sediments during late San Lorenzo and Vaqueros time. Faulting and uplift in the Gabilan Range produced the continental red beds which were deposited towards the head of the narrowing trough. Local volcanism assisted in filling the trough with a series of lavas. Middle and Upper Miocene Middle Miocene seas transgressed, first over the area east of the ancestral San Andreas, then farther westward, although they did not cover the Gabilan Range farther south, which continued to supply large amounts of granitic debris to adjoining basins. Continued submergence widened and deepened the seas until the adjacent lands were so low that they contributed only slightly to the basins. This period of submergence was brought to an end by the greatest orogenic upheaval to affect the area, an orogenic period which probably started slowly, and culminated in the lower Pliocene with intense folding, faulting, and uplift of the Santa Cruz Range, the development of the Santa Clara-San Benito trough east of the range, and the Monterey Bay-Pajaro downwarp. Pliocene Marine and continental sediments, equivalent in thickness to all the rest of the Tertiary column together, were deposited during Pliocene times in the trough east of the Santa Cruz and Gabilan ranges, over por- tions of the low Santa Cruz Range, and in the shallower seaway which connected it through the Monterey Bay-Pajaro downwarp with the ocean to the west. It is not known whether this connection existed in the lower Pliocene or not, although the downwarped area in the center of the region had been initiated previously. In the upper Pliocene the rapidly sinking and aggrading trough was filled and continental deposits predominated, although there were a few short-lived marine invasions. Pleistocene and Recent Following the lower Pleistocene period of folding and thrust fault- ing, the land was eroded to form a low-ljdng late-mature land surface, and slight submergence caused the development of a wide sand- and lagoon-covered coastal plain on the west. Gentle warping, faulting, and tilting, resulting in vertical movements of considerable magnitude, were accompanied by some eustatic changes of sea level. The present high ranges, with their valleys and terraces are the result of these complex movements and the accompanying and subsequent erosion. 122 Gilbert, C. M., op. cit, 1943. GEOLOGY ALLEN 67 SUMMARY OF GEOLOGIC HISTORY The Sur series of sandstones, shales, and Gabilan limestones was deposited in pre-Santa Lucia times and was metamorphosed and intruded in pre-Franciscan times by the Santa Lucia granite. During the upper Jurassic there was widespread extrusion of basaltic agglomerates and flows, mostly submarine in origin, which was followed by deposition of limestones and cherts, probably resulting indi- rectly from the same period of volcanism. Arkosic sandstones and shales were then laid down in great thickness, and the entire sequence was intruded by ultra-basic rocks, now altered to serpentine. Faulting along the ancestral San Andreas fault uplifted the western portion of the area, and the Franciscan rocks were completely eroded from the granite. No evidence of deposition during the Cretaceous and Eocene appears within the area, although it is possible that sediments were laid down and eroded prior to the deposition in a narrowing seaway of the Oligocene and lower Miocene rocks. Emergence and volcanism in the lower Mio- cene produced red beds and lavas of varied composition. The Monterey group of arkosic sandstone grading into clay-shales and diatomaceous shales was deposited in transgressive seas which eventu- ally covered most of the quadrangle. After a period of intense folding and faulting, the middle Pliocene seas invaded the central and eastern portions of the area, and were rap- idly filled with highly fossiliferous and relatively coarse sediments from the nearby low mountains. Non-marine deposits continued to pile up after the retreat of the sea. Pleistocene folding caused uplift and erosion of these sediments, and the area was reduced to a stage of late maturity, with deposition of sub- aerial sands over most of the western portion. Late Pleistocene tilting, uplift, and fluctuations of sea level pro- duced a series of terraces and the present stage of youth and early matur- ity. Horizontal movements along the San Andreas fault were some of the last events to take place. MINERAL RESOURCES Limestone and Dolomite The Pacific Portland Cement Company (formerly Mission Portland Cement), whose plant is located 1 mile south of San Juan Bautista, has not been in operation for several years, although the plant has been kept in good repair. Limestone was formerly brought down San Juan Creek from quarries located off the map on spurs of Gabilan Peak, over a narrow gauge railroad, a distance of from 5 to 8 miles. More recently the lime- stone, which occurs in the roof pendants of the Sur series, has been trucked over a highway constructed on the old railroad grade. The Bethlehem Steel Company now owns a quarry located in a large lens of Gabilan limestone on the southern edge of the map 1| miles south of Sugarloaf Peak, half a mile north of the Permanente Metals Company quarry. This quarry was opened around the turn of the century to supply limestone to the beet sugar factory at Salinas. ^-^ The lens of 1^ California State Mining Bureau Bull. 38, p. 73, 1906. 68 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Fault North South Attitude of limeston N60°W 40° NE QUARRY FACES Scale 50ft.= I In, — -^.^ E S (opprox.) OF QUARRY FACES Scole ZOO ft.= I in Sketch by J e Allen, Nov 12,' 44 Fig. 10. Permanente Metals Corporation quarry, 1 mile north of Natividad, Monterey County limestone, wliich is a continuation of the one being mined farther south, has an exposed thickness of over 50 feet in the quarry. The rock is so massive and pure that, at time of visit in 1934, there were no internal structures visible whereby its attitude could be determined. The Permanente Metals Corporation dolomite quarry is located on the eastern edge of the Salinas Valley just off the southern edge of the quadrangle. The quarry is 800 feet in length, and the rock is mined in two benches, with about 70 feet difference in elevation. A large electric shovel and carryalls permit operation on a considerable scale. The rock is predominanth^ massive, pure white and coarsely crystal- line. It is a dolomitic limestone, differing from other lenses in the area which are pure calcite. An analysis supplied by Mr. E. A. Hassan, Jr., engineer for the company, is quite representative of the dolomite : CaO 31.7 percent MgO 20.5 SiO:2 1.0 Fe^Os 0.2 AlsO^ "0.2 CO2 46.4 100.0 percent In a few places a light-gray finer-grained phase appears. The chief mining impurity consists of irregular apophyses, sills, and dikes of dark granite, now so completely decomposed that it can be scooped out with the hand. These intrusions follow obscure bedding planes in the lime- GEOLOGY — ALLEN 69 stone, which strikes N. 60° to 70° W., and dips 40° to 45° NE. They vary in thickness from a few feet to 25 feet. The south face of the lower bench consists of giant elongated blocks of limestone completely sur- rounded by decomposed granite. There has been some faulting, best exhibited at the northern end of both benches, more or less parallel to, but steeper than the bedding. Narrow pegmatite dikes intrude the granite at the south end of the upper bench. They occasionally have quartz crystals up to 3 centi- meters in diameter and biotite plates 4 centimeters across. Shearing adjacent to the granite-limestone contacts commonly has developed a soft yellow to white cheese-like gouge. The body of limestone in which both this and the Bethlehem Steel Company's quarry is located is 1 mile long and three-quarters of a mile wide, extending from an elevation of 275 feet on the west, to the crest of the ridge at 985 feet, as mapped by the writer and Herold ^^^ in 1934. The contact on the east side of the ridge is not far below the summit. The following report ^-^ on the plants of the Permanente Metals Corporation is based on the author 's visit in December 1944, to the Per- manente Metals Corporation and the Permanente Cement Company, located about 15 miles west of San Jose; also to the two raw-materials plants located east of Monterey Bay. ' ' Magnesium is produced at Permanente by the carbothermic, or Hans- girg, process; the metal being obtained from dolomite (MgCOa.CaCOs) and sea water in equal parts. The dolomite quarry is located at Nativi- dad, about 8 miles northeast of Salinas, California, where the rock is mined by open cut quarry with electric dipper shovels and crushed and calcined at 2000° F. to the double oxide in two large rotary kilns of the cement calcining type. Calcined dolomite is trucked a distance of about 12 miles to the coast on Monterey Bay. Water is taken from the ocean at this Moss Landing plant at the rate of 6500 gallons per minute through a 5-foot-diameter wood stave line and delivered to hj^drotreator tanks where suspended solids and carbonates are precipitated. The treated sea water then flows through reactor tanks where the calcined dolomite, slaked to the hydroxide, is introduced. Here the magnesium in the sea water, being higher in the electromotive series than the calcium in the dolomite, replaces it to produce magnesium hydroxide. This slurry is then thickened in four 250-foot thickeners and washed in a fresh-water flow of 1000 gallons a minute. The excess water is then removed in a battery of Oliver filters and the filter cake is conducted by a screw con- veyor to another large rotary kiln where it is hydrated at a temperature of 2300° F. This material, over 96 percent MgO, is trucked in large trailer trucks to the Permanente plant west of San Jose. ' ' At Permanente it is mixed in molecular proportions with petroleum coke, and interground in a 26-foot ball mill. This material is briquetted in a series of presses and distributed to air-locked feed bins of the five 8000 KVA reduction furnaces. From this stage on until the finished metal comes out of the retorts, the process is conducted in an oxygen-free atmosphere. The reduction furnaces are approximately 16 feet high and 16 feet in diameter, and are heated by three electrodes coming in from the top, each electrode being 20 inches in diameter. The electrodes are 12* Herold, C. L., personal communication. 1^ Previously published in The Ore Bin, vol. 7, no. 1, for January 1945, pp. 4-G, ■ State Department of Geology and Mineral Industries, Portland, Oregon. 70 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 fed automatically into the furnaces and are insulated against electricity, pressure and heat. At the operating temperature of 2000° C. the reac- tion MgO+C=:Mg-j-CO takes place and the gaseous products come out a port in a side of the furnace where they are shock-chilled by jets of natural gas. The microscopic magnesium dust produced by this reaction and shock-chilling is removed from the gas by a battery of bag filters. When the plant was first put in operation it was found that carbon tended to build up in the discharge ports of the furnaces. An automatic reamer was then built, which periodically during the operation slides into the furnace and cleans out this port. The magnesium dust from the bag filters is conveyed to dust bins and from dust bins to gas-tight enclosed pelleting presses of special design. Pellets are loaded, still in a closed atmosphere of gas, into vertical air-tight retorts about 4^ feet in diameter and 20 feet high. These steel retorts are metal ized with aluminum on the outside to retard their oxidizing under the heat of the electric resistance furnaces into which they are then lowered. The fur- naces, heated by banks of nichrome wire coils, sublimate the magnesium metal at 1400° F. at an absolute pressure of 0.2 millimeter of mercury. In the upper condensing portion of the retort is a removable liner which during the 90 hours of heating collects the crystalline magnesium sub- limate. The area over which the retorts are prepared for loading, fur- naced, set to cool, and stripped, measures about 230 by 290 feet. The retorts, which weigh about 10 tons loaded, are lifted and conveyed from place to place by two large gantry cranes. Loading is conducted on a rotating scale platform containing five retorts, which places each retort in turn beneath an automatic air-lock connected to pellet storage bins. Each retort must be completely purged of air before it is loaded. When the retorting is completed, the magnesium crystals are exposed to the air for the first time. They are cracked loose from the liners and routed to the ingot casting foundry where they are melted in gas-fired tilting fur- naces. The crystals, which are over 99.99 percent pure, are alloyed in these crucible furnaces and cast into ingots to be used subsequently for sand castings, forgings, and extrusions. Sulfur and SO2 gas are used for protecting the metal from burning during pouring. ' ' Magnesium production is only one of the activities at Permanente. The original plant at this locality was erected by the Permanente Cement Company. The wet process is used and clinkering is done in four 364- foot kilns — the largest in the world. Limestone for the cement is mined in the hill above the plant from a great lens of dark-colored bedded lime- stone lying in the Franciscan series of Jurassic age. An altered volcanic rock nearby is used to furnish the siliceous and iron elements of the cement in proper amount. High-grade limestone is sold directly from the quarry and waste limestone is sold as commercial rock. The seven types of Permanente cement are sold in bags and in bulk, shipment being made by bulk-truck, box car and company-owned steamships. "The third separate and distinct operation on the property is the ferrosilicon plant. It consists of three 8000 KVA electric furnaces. Raw materials used are silica in the form of quartz, coke, and steel shavings. Quartz is mined at a company-owned quarry near Merced, California, and coke is furnished by Fontana. The plant was brought into production about the middle of 1942 to furnish ferrosilicon for the Kaiser sponsored D.P.C. magnesium plant at Manteca, California. Magnesium was produced here using the silicothermic, or Pidgeon GEOLOGY ALLEN 71 process. Tlie government shut the Manteca plant down in 1944 and since then the ferrosilicon plant at Permanente has been supplying the ferro-alloy to users throughout the country — principally steel producers. ' ' Plants tributary to the magnesium plant consist of a nitrogen plant which produces the inert gas for some portions of the process. Here air and natural gas are introduced into retorts in which the oxygen is burned out of the air and the resulting nitrogen is cleaned of the other products in scrubbing towers. A Girbotol water-gas plant is operated to produce hydrogen which is used as an inert gas in portions of the process. A sand casting plant produces magnesium castings which are going exclusively toward the war effort. A refactories plant utilizes magnesium oxide to produce periclase refractory brick for lining the cement kilns and open hearths at the Kaiser steel plant at Fontana and also for sale to other plants. A flux plant produces the various fluxes used in the foundry and also produces for sale on the outside market. Natural gas is dried and scrubbed in order to make it available for use. A complex system of piping of the various raw materials and products is spectacular in that each pipe is colored to indicate the material which it carries. Water pipes are painted black ; natural gas, red ; high vacuum, yellow ; low vacuum, brown ; high pressure, low pressure, nitrogen, hydrogen, mag- nesium dust, exhaust or vent pipes are all painted distinctive colors ; and the complexity of various colored and sized pipes running through the pipe trenches and tunnels from plant to plant is interesting indeed. "By-products marketed by The Permanente Metals Corporation are numerous, the most important ones being : Raw dolomite — Used in open hearth steel furnaces. Hydrated and processed 7 — Used in the building trade, oil refining and for general high magnesia lime J commercial and chemical use Dead burned dolomite and ramming mix -Electric furnace and open hearth bottom maintenance Magnesium oxide (various burns and compositions) -Rubber compounding Chemical uses Basic brick (periclase) Ladle and furnace linings (periclase) Carbothermic magnesia ] (residue from the i- — Compounding neoprene and GR-S synthetic rubbers carbothermic process ) J The first four are more or less standard products and are produced and shipped direct from the Natividad or Moss Landing plants. Carbo- thermic magnesia is a special product produced from treating the residue obtained from the retorting* step in magnesium production at Perma- nente. The special treating is done in a separate plant using a process developed by the research staff at Permanente. "Magnesium is the lightest metal in commercial use. It weighs only two-thirds as much as aluminum, one-fourth as much as steel, and one-fifth as much as copper. Some magnesium alloys have the tensile strength of structural steel. It can be machined faster than any other metal and can be fabricated into desired shapes by any method commonly used in making other metals. It can be sand-cast, die-cast, extruded, forged or rolled into flat or tapered sheets. It may be rolled into sheets varying from 0.014 to 0.500 inch in thickness. Magnesium may be welded by the use of a special arc which is insulated from the air by a jet of helium or argon gas. ' ' 72 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Several small limestone quarries have been operated from time to time in various parts of the Gabilan Range within the quadrangle. A few tons have been removed from lenses within the Franciscan north of La Brea Creek. In a few places giant boulders of limestone have been quarried from the red beds, as in an old quarry 1 mile west of Gabilan School. Quarries in lenses of Gabilan limestone are located at elevation 1925' on the ridge east of Steinbach Canyon ; at the top of the hill south of Sugarloaf Peak (this rock was burned in an old brick kiln located near the forks of Gabilan Creek 1 mile northeast of Sugarloaf Peak) ; at elevation 700', half a mile south of San Juan Creek up a western branch ; and at several points along the long east-trending line of roof pendants which crosses the San Juan grade 1 mile south of the summit. Crushed Rock, Sand, and Gravel The Granite Eock Company, whose quarry is located at Logan siding, 14 miles northeast of Aromas in Pajaro Gap, is one of the largest and oldest quarry operations on the coast, and has supplied large amounts of railroad ballast, road metal, and crushed rock for other purposes for many years. The main quarry floor is about 80 feet above the railroad, the material being transported from the quarry face, where it is loaded by electric shovel, by a narrow gauge railroad to the crusher bins. The face has now been advanced to a point where the sand and gravel overburden is from 20 to 40 feet thick, and benches 20 feet below the main bench are being developed which require raising the rock this distance to the bin level. Another bench some 60 feet below the main bench has been started, this rock being lifted by means of a steep tramway and cable. Production over a period of years is reported to have been about 300,000 tons a year, but recent increased demand for airport and army camp ballast and road material has increased the output many fold. The quarry is located on a northwest-trending spur 450 feet in average elevation, which is composed of dark hornblende-quartz diorite. The San Andreas fault parallels the northeast side of the spur, and the granite, which is about half a mile wide in outcrop, is bounded on the west by steeply dipping Monterey sandstone and shales exposed in the railroad cut just west of the quarry. Both the Monterey and the granite are overlain unconformably by 10 to 40 feet of Pliocene basal con- glomerate and soft sandstone, which strikes N. 60 to 70° W. and dips 10 to 12 degrees southwest. Granite is exposed in gullies along the east flank of the spur for a distance of 5 miles to the southeast, althongh its outcrop width is narrow due to the overlap of the Pliocene and Pleistocene sands which form the high ridges east of Aromas and south and Avest of Anzar Lake. The contact varies somewhat, probably due to northeast-trending trans- verse faulting. Across the Pajaro River northwest of the main quarry, granite outcrops in the precipitous wall of the canyon beneath a heavy cover of Pliocene rocks, and has been quarried at one point on the highway. The rock types exposed in the quarry were first described by Reid,^26 and the structures have been discussed in detail by Willis.i^^ ' The pre- „ , !;"?^*^''^', -^A ^•' '^'■'*' i?:'>fioiis rocks noar Pajaro: Univ. California Pub. Bull. Dept. Geol. Rci., vol. ."?, no. 6, pp. 173-190 1002 J2T Willis, Bailey, op. cit., 1938. '4 DIVISION OF MINES WALTER W BRADLEY STATE MINERALOGIST OLAF P JENKINS CHIEF GEOLOGIf STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOU ■■'■ T GEOLOGICAL MAP SARGENT OIL FIELD SANTA CLARA COUNTY , CALIFORNIA GEOLOGY BY J.E ALLEN LEGEND Course of outcrops Troced In port from aerioi photos of Itifl AAA ACCOMPANYING BULLETIN 133 19'4s"' T.TST OF WELLS DRILLED WITHIN THE SAN JUAN BA0TISTA QUADRANGLE AND ADJACENT AREAS Date driUed Name of well Eleva- tion Depth Depth to oil sand Initial production Average production Gravity Baume Comments Location 1906 A. Sargent oil field Watsonville Oil Co. #1 - - Ft. 335 329 322 485 429 346 421 646 600 ± 300 ± 311 318 469 462 485 337 335 550 ± 150 d= 150-300 230 170 700 ± 450 ± 675 ± 175± 1,165 157 ? Ft. 1,620 1,218 935 1,904 902 1,535 3,050 1,975 1,675 1,335 1,320 2,020 1,325 2,050 1,482 740 ? 3,552 3,680 Shallow 3,583 4,427 3,053 1,681 2,580 ? 5,200 6,921 1,500 2,896 914 Ft. 704 and 1,603 Bbls. 40 250 150-300 Bbls. 3 4 15 4 14 7 9 5 15-16 Degrees 17-20 18-20 22 1908 Watsonville Oil Co. #2 . . . - . 637-690, 1,184-1,204 ? Entered Monterey at 70' All in Sec. 36, T. US., R. 3E. Pumped on alternate days for initial production 1904 Watsonville Oil Co. #3 - - - - - Entered Monterey at 175' ? WatsonviUe Oil Co. #4 (Old) 1,142 1913 Watsonville Oil Co. #4 (New) . . 711-812 Little 9 Watsonville Oil Co. #5 947-982, 1,000-1,150 1916 Watsonville Oil Co. #6--. 945 6 to 15 Asphaltum 5 ? Watsonville Oil Co. #7 350-365 Conglomerate at 1 900 ' Sec. 31, T 11 S., R. 4E. 9 Watsonville Oil Co. #8 1,515-1,670 1916 Watsonville Oil Co. #9 .-- -- - -. Per "^fi T 1 1 S T? "^ F 9 Watsonville Oil Co. #10 80-110, 450-558 Sec 36 T 1 1 S R 3 E 1919 WatsonviUe Oil Co. #11 1,410, 1,445, 1,655, 1,685... 12 Sec 36 T 11 S R 3 E 7 Watsonville Oil Co. #12 Sec. 6, T 12 S R 4 E 1918 Watsonville Oil Co. #13 1,552-1,560 11-20 18 Entered Monterey between 70 and 120' 1919 Watsonville Oil Co. #14 958-1,450 Sec 36 T 1 1 S R 3 E 1919 Watsonville Oil Co. #15 - 657-700 Sec 36, T 11 S R 3 E 1920 Watsonville Oil Co. #16 7... Sec. 5, T 11 S, R 3E 9 1,700 or 1,800 36 Heavy Heavy Entered Franciscan at 3 960 ' Sec 36 T 1 1 S R 3 E 1906 Martin-De Sabia 1,700-1,800 Sec 5, T 12 S R 4 E 1905 ca. Chittenden #1 to 7 (#6 in Sec. 2) Sec. 11, T. 12 S., R. 3 E. 1923 Santa Clara Oil Co #1 3,305 Bottomed in blue shale Sec. 1, T. 12 S., R. 3 E. 1920 Shell Oil Co Lomerias #1 All in Pliocene. Entered Franciscan at 6,869' All in Pliocene. Entered Franciscan at 6,869 ' Sand and shale, fossils at 561 and 904' . Sec. 4, T 12 S., R. 3 E. 1927 Continental Oil Co. Sar #1 Sec. 31, T. 11 S., R. 4 E. 1928 Continental Oil Co. Sar #2 Sec. 31, T 11 S., R. 4 E. 1928 Continental Oil Co. Sar. #3 Sec. 1, T. 12 S., R. 3 E. 1921 Breacita #1 Sec. 5, T. 12 S., R. 4 E. 1925 Petroleum Midway Oil Co. #1 (now Texas Company) Tidewater .Associated #1 Sec. 10, T. 12S., R. 4E. 1936 1 Sec. 5, T. 12 S., R. 4 E. 1922 B. Other wells drilled within quadrangle Sec. 14, T. 11 S., R. 2 E. 1933 Lee, or Wellton 0. & G. Galletly #1 . Alternating sand and shale. Shale 1,994-2,823', Betabel Fruit Farm 432 Sec. 14, T. 11 S., R. 2 E. Shile, sand, and conglomerate. . . . - . Sec. 31 or 32, T. 12 S., McAbee, L. A. R. 4E. 1932 2,170 1,490 ? 680 685 968 1,440 3,198 4,009 Sec. 31, T. 12 S., R. 4 E. 1924 Harper, Henry 200 Fossiliferous shale, sandstone, and conglomerate Sec. 33, T. 12S., R. 4E. Pre-1936 Sec. 14, T. 11 S., R. 2E. 1936 Rysek, Gerald Sec. 14, T 11 S.. R. 2E. 1936 Shepherd, M P Sec. 14, T. US., R. 2E. 1924 C. Wells drilled adjacent to quadrangle United Royalties Co 1927 Marik, Frank 300 181 Sandstone and blue shale. Fossil above 79', only. . . Mostly sandv shale, fossils abundant Sec. 18, T. 11 S., R. 2 E. 1932 Western Gulf Oil Co., Johnson #1 Sec. 29, T. 12 S., R. 2 E. 1937 Elba Oil Co. Capurro #1 Aptos to 1,058', Merced to 2,240', Santa Margarita General Petroleum Co . Sec. 29, T. 12 S.. R. 2 E. 1944 Merced to 2,023', Purisima to 2,767', Santa Mar- Sec. 6, T. 13 S., R. 2 E. ''"Reid .T A., The isrnftoiis rocks noar Pajaro Geol. Rcr vol. 3 no. G, pp. 173-190, 1902. 527Willis, Bailey, op. cit., 1938. GEOLOGY — ^ALLEN 73 dominant type is a dark-colored coarse-grained altered quartz diorite, previously described and figured under Stratigraphy. A still darker phase in which horneblende is predominant is not uncommon, and there are numerous acid dikes, pods, and stringers, ranging from aplitic to pegmatitic in texture. The proximity of the quarry to the San Andreas fault zone is responsible for the jointing and crushing which facilitates quarrying of the rock. Several small road-metal quarries located near higlnvays have supplied material for road construction from time to time. One such quarry is located half a mile east of Langley School on U. S. 101. It is in decomposed granite, which is soft enough to be excavated by dipper shovel without blasting. The granite is bounded on the northeast by fault contact with Aromas sands. Another quarry is located in similar material on the San Juan grade half a mile east of Lagunita Lake. Here the weathered granite is overlain by Aromas sands, and terrace gravels lie on both sides of the cut. On the east side of San Juan Creek a few hundred yards south of Gabilan School, there is a quarry in Sur meta- morphics and granite, from which road material was apparently taken during the construction of the Gabilan Peak road. Two small sand and gravel quarries are located just north of, and half a mile northM^est of Casserly School in the northwest corner of the quadrangle. The sections of the Pliocene sediments exposed are described in the section on Pliocene stratigraphy. Petroleum Sargent Oil Field As early as 1861, Brewer ^-^ recounts that he visited, on the ranch of a Mr. Sargent, "tar springs and oil works, where oil is made from asphaltum. " Twenty-three years later Hanks ^^^ reported that "about 20 years ago" a refinery was built on the Sargent Ranch, and that 20 or 30 tons of asphaltum were taken from the breas near the mouth of La Brea Creek, 75 carloads from the breas half a mile farther up the creek, and 200 carloads from the largest seeps (at the present oil field) 1|- miles farther up the creek. According to Watts ^^*^ the first well Avas drilled in 1886, on the south- side of the creek to a depth of 700 feet, a second was drilled in 1890 on the large seep on the north side of the creek, to a depth of 80 feet. Neither was successful. By 1900, 7 wells had been drilled,^^^ one of them producing 5 bar- ]-els a day. By 1903 Prutzman i^- reports that there were 3 producing wells, 30 wells had been drilled and abandoned, and 2 wells were drilling. Between 1907 and 1920 ^^•"' a total of about 10 producing wells and 6 dry holes were drilled in the Sargent field, 7 dry holes were drilled 128 Brewer, W. H., Up and down California in 1S60-G4, edited by Francis P. Far- quhar, Yale University Press, p. 126, 1930. 129 Hanks, H. G., Fourth Annual Report of the State Mineralogist : California Min. Bur. Kept. 4, p. 289, 1884. 130 Watts, W. L., Tenth Annual Report of the State Mineralogist : California Min. Bur. Rept. 10, p. 607, 1890. 131 Watts, W. L., Oil and gas yielding formations of California: California Min. Bur. Bull. 19, p. 152, 1900. 13- Prutzman, P. W., Production and u.se of petroleum in California: California Min. Bur. Bull. 32, p. 19, 1904. i33Michelin, J. op. cit, p. 475, 1943. 74 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 north of Chittenden (in 1905) and the Martin & De Sabla well was drilled near the railroad south of Sargent Station (1906). Beginning with the 4400 foot Shell Oil Company dry hole, drilled in 1920, six comparatively deep wells were drilled during a period of 8 years, most of them east of the producing field, one of them, by the Santa Clara Oil Company, to the south. The seventh and deepest was drilled to 6921 feet in 1936 by Tidewater Associated. All were dry holes. Production has been restricted to the 75 acres covering the present Sargent field. Up to 1904, it totalled only 20,000 barrels of oil. The peak year was 1909 with 63,780 barrels, and the estimated total to January 1, 1941, is about 600,000 barrels. At the present time it is reported that 9 Avells produce about 30 barrels a day. Other Wells Dry holes have been drilled at a number of localities elsewhere in the quadrangle. A mile west of San Juan Bautista there are five shal- low wells, and one well is located just south of town. At least five wells were drilled in sec. 14, T. 11 S., R. 2 E., in the Santa Cruz Range foothills between the San Andreas fault and the Pajaro Valley east of Casserly School. Five other holes have been drilled a mile or so west of the edge of the map in the Capitola quadrangle. These holes indicate the presence beneath rocks of the Pliocene group, of Santa Margarita shale, which does not outcrop within the San Juan Bautista quadrangle, unless the uppermost part of the Mount Pajaro section should prove to be Santa Margarita in age. Black Sands in Capitola Quadrangle A magnetite-sand plant, producing ship ballast, is operated by the Nevada Santa Cruz Company, 1999 Brj-ant Street, San Francisco, in the Capitola quadrangle, which adjoins the San Juan Bautista quad- rangle on the west. This plant is 4 miles south of Aptos on the beach and railroad, in Santa Cruz County. For approximately- 2 miles along the beach of Monterey Bay to the south and east of the plant, lenses of naturally concentrated magnetite sand are deposited by winter storms. These lenses are from a few inches to 3 or 4 feet in thickness and from a few feet to several tens of feet in width. The 40- to 60-foot cliff behind the beach is composed of soft, unconsolidated, deep-red, cross-bedded sand which has a high mag- netite content, from which the black beach sand is undoubtedly derived. These terrace deposits are of Pliocene or Pleistocene age. During most of the year, except for interruptions by winter storms, this section of the beach may be traversed along the base of the cliff by large-tired carryalls with several yards capacity. The sand, which in the natural state contains up to 80 percent magnetite, is deposited over an automatic feed into which it is fed by a bulldozer at a rate of from 16 to 17 tons an hour. From the feeder it is lifted by a bulldozer directly to a two-section 42'' by 42" Pan American jig. The concen- trate section of the jig feeds to a sand pump which delivers the concen- trate to a classifier and stock pile. A belt conveyor from beneath the stock pile loads the concentrate directly onto railroad cars at Manresa siding. The second half of the section delivers the lower-grade material to two settling tanks from which it is fed to two 16-foot Wilfley tables. GEOLOGY — ALLEN 75 The concentrate of the first two Wilfley tables goes to the sand pump and classifier. The middlings from these two tables are delivered to a third table whose concentrates go to the sand pump. The tails from all three tables are delivered to a rock washer and are dumped on the beach. The concentrate product must meet specifications requiring specific gravity of 4.79 to 4.80. The pure magnetite of this deposit, mixed with some ilmenite, has a specific gravity of about 5.05. The plant, with a normal operation of 8 to 10 hours a day, can easily produce a carload a day of concentrate. Barite In 1916 and 1918-1920, inclusive, barite was mined and shipped com- mercially from lenses in the limestone on the north side of Gabilan Peak in Monterey County near the San Benito County line.^^^ 13* See Bradley, Walter W., California Mineral Production : California State Min- ing Bureau, Bull. 74, p. 89 ; Bull. 86, p. 113 ; Bull. 88, p. 106 ; Bull. 90, p. 116. OPERATIONS OF THE GRANITE ROCK COMPANY QUARRY AND PLANT AT LOGAN, SAN BENITO COUNTY By Royal E. Fowle' OUTLINE OF REPORT Page Introduction 77 Early quariy operations 78 Present quarry operations 78 Present crushing and screening plant operation 79 Crushing and screening equipment SO Regrindiug plant 80 New plant operations 80 Uses of granite rock and granite crusher-run base 80 Other equipment 81 INTRODUCTION The Granite Rock Company of Watsonville, California, owns and operates a quarry and plant at Logan, San Benito County. The land was a part of the Judge Logan Ranch, located in Raneho Las Aromitas Y Agua Caliente (Ranch of Little Fragrances and Hot AVater), one of the land grants made by the Spanish Government when the area was ruled by that country. The deposit is on the south side of the Pajaro River Gap, 93 miles south of San Francisco and on the main line of the Coast Division of the Southern Pacific Company. The Gap forms the most constricted passageway in Chittenden Pass, the dividing line between the Santa Cruz Mountains on the north and the Gabilan Range of the Gabilan Mesa on the south. Both are a part of the southern Coast Ranges. The company was incorporated in February of 1900 when the Fletcher property and its small local quarry was purchased bj' A. R. Wil- son and W. R. Porter. A. R. Wilson was a civil engineer, formerly city engineer of Oakland, contractor and operator of the Leona Heights quarry near that city. His family owns the Granite Rock Company toda}'. Mrs. A. R. Wilson is president ; A. J. AVilson, son of A. R. Wilson, is now vice-president and general manager. W. R. Porter was a local lumberman and president of the Pajaro Valley Bank. In 1905 he became Lieutenant Governor of the State of California. John E. Porter, son of W. R. Porter, is now secretary and sales manager. Royal E. Fowle is engineer and production manager ; Frank Swearingen is superintendent. The plant has been in continuous operation under the Wilson manage- ment since 1900. As the State grew, the Granite Rock Company grew, until today it has a production capacity of 750 tons per hour. In submitting this article the author wishes to express his apprecia- tion for the assistance given him by AYalter W. Bradley, Olaf P. Jenkins, Charles V. Averill. and John Eliot Allen. * Engineer and production manager, Granite Rock Company. Manuscript sub- mitted for publication December 5, 1945. Much of this material has also been pub- lished bv the author under the title Ticenty MUHon Years of Primary Crushing, in Rock Products, vol. 4S, no. 12, pp. 119-120, 122, 124, 143, 144, 14.5, December 1945. (77) 78 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 EARLY QUARRY OPERATIONS The quarry operations of 1900 were ^\•ithout benefit of machinery of any type. The rock was barred down from the sides of the sloping g:ranite dome and caused to fall to the toe of slope lying next to the Southern Pacific tracks. The larger pieces of rock were then broken by sledge hammers to a maximum of about 6 inches after which they were hand-loaded on flat cars and shipped to the various jobs. The output per day averaged five 35-ton cars. This daily tonnage of 175 tons or 17^ tons per hour, was produced by about 15 men, who averaged about 12 tons per man per day. The rate of pay per man was $1.75 per day of 10 hours. PRESENT QUARRY OPERATIONS The rudimentary quarry operations of 1900 have developed until todaj^ they consist of the following steps : ( 1 ) removal of the overburden ; (2) drilling and blasting; (3) shovel-loading the quarry rock into cars; (4) hauling the rock to the crushing plant chutes and dumping it. The first operation, removal of the overburden, is accomplished by hydraulicking ; water from the Pajaro River is pumped through two 4-incli lines to the top of the quarrj^ dome by Deane Triplex mine pumps, where a hydraulic giant is used to direct the jet. Used water is impounded in hydraulic dams where the solids settle out, allowing the clear water to return to the river. A mastodon was uncovered in the overburden in 1931. The second step, drilling and blasting, is more readily accomplished than in many quarries, as well drilling on top of the exposed rock dome is unnecessary. About twenty million years ago there came a period of great folding and faulting in the quarry area. The granite was intensely folded and broken, crushed and uplifted. Later action along what is now the San Andreas fault, which passes through the quarry, con- tinued this crushing. This action has resulted in quite low powder costs; costs which otherwise might have been prohibitive. It is only necessary to use toe holes or snake holes at the base or toe of the quarry face. These are put in by a Gardner-Denver wagon drill to a slope depth of about 24 feet. All holes are sprung so that they will contain a charge of from 5 to 8 boxes of 40 percent Nitro Starch Trojan Powder for normal shots. Several holes are usually fired simultaneously, bringing down the quarry face in sizes that can be handled by the power shovels. Nitroglycerine powder (gelatine) is used when water is encountered. Rocks too large for the crushers are set out by the shovel operator and later blasted or "bulldozed" to smaller sizes when the shovel is in the clear. The third operation, car loading, is done by two electric shovels, with Ward-Leonard controls. A 75-B Bucyrus 2|-yard shovel operates on the top or 100-foot level (see plate lOB). A 100-B Bucyrus 4-yard machine works on the middle or 75-foot level (see plate llA). A 37 Marion is now used for development work on the lower level at the Southern Pacific tracks. Five-yard Western side-dump quarry cars are loaded from a pit at the toe of the quarry face. The 75-B uses about a 5-foot pit, the 100-B, one of 12 feet. These pits are desirable in that they give a greater depth of cut in the rock formation; they normally keep loose rocks and shot rock from blocking the circular 4 fa O o en p— I > 2 o E-i M 2: H ^" -15 C3 o Q o u o o H ci 2 z ^ o m t-H O O t^ O DIVISION OP MINES BULLETIN 133 PLATE 10 V* •, . A, GKANITF, UOCK I'O.Ml'AXV QUAUllV B, GRANITE KUCK CO.Mi'ANY QUAUliY 100-foot and 75-foot levels DIVISIOX OF MINES BULLETIN 133 PLATE 11 ?;,■ ''-^.j,;- I A, GRANITE ROCK COMPANY QUARRY 75-foot level. The shovel is a 100-B Bucyrus 4-yard machine I m' B, GRANITE ROCK COMPANY PLANT Loading cars with crushed rock < Ah Eh m H P-H o o t-l m (—1 > I— I P 0) O < -< o O -2 Pi c o g td ■" he O ft m -c fa O h H M 133 £ o ^ O ,M o o « OJ 4-J c rt u, O GRANITE ROCK COMPANY FOWLE 79 track and they give the shovel dipper a better digging and loading condition. The fourth and final quarry operation takes place when the cars are hauled to the head of the crushing plant rock chutes where the rock is dumped. There are two of these chutes, one located above a No. 8 McCully crusher, the other over a No. 7^ of same make. They are adjacent and parallel, forming two separate and distinct crushing and screening plants, which makes a very flexible and economical layout. The quarried material flows over 30-foot Tee bar grizzlies where the minus 3-inch quarry fines pass through the bar openings and are collected in storage hoppers placed directly underneath. These fines are not overburden, as this is removed by Iwdraulicking. They consist of pieces of crushed and ground granite found between the larger pieces that make up the deposit and show clearly in the quarry face. This face has a blue-gray to a stained light-brown surface appearance, depending on the degree of iron oxidation from the hornblende which makes up much of the dark particles in granite. The granite itself is a mixture of quartz, feldspar, and hornblende. Water seeping down through the frac- tured rock dome over millions of years furnished most of the oxygen for the iron oxidation of the rock surfaces. PRESENT CRUSHING AND SCREENING PLANT OPERATION The plant operation begins with the quarried rock flowing over the Tee-bar grizzlies. The quarry fines thus removed are fed from their storage hoppers by reciprocating feeders to stub 30-inch conveyor belts. There is one for each grizzly hopper, set at right angles to the chutes and discharging onto a 30-inch belt set between and parallel to the two parallel rock chutes. The fines are then carried to a 4' x 16' revolving scalping screen hav- ing 25-inch openings. The rock going over the screen can be placed in the crushing circuit of either plant; that passing through the screen is discharged to a 30-iuch reversible conveyor belt running directly under the center-line of the screen. This belt carries the minus 2^-inch product to a heavy bucket elevator which lifts it to a truck bunker placed near the head of the chutes on the 100-foot level. The 30-inch belt can be reversed and the material discharged to a bunker for the loading of railroad cars. All or part of the cru.shed sized material from either or both of the plants, i.e. No. 7| or No. 8, can be run to this same bunker, giving a verj^ flexible method of correctly grading crusher-run base. This product is widely used in highway and airport construction. The lieav}^ quarried rock, after having its fines removed by passing over the 3-inch bar-grizzly openings, is fed from the rock chutes to the primary crushers, where it is reduced to crushed rock of approximately 3-inch maximum size. It is then screened and that over 2^-inches in size crushed to smaller pieces. After further screening and crushing it is segregated and bunkered in various standard commercial sizes ranging from 2V' x 1^" to i" x 3^". The smallest size produced is known as crusher fines or j^'^ x — 200 mesh ; this is used as fines in asphalt con- crete and plant mix surfacing. All crushed rock from the various plant bunkers or from stockpile is re-sized, washed, and de-watered as part of the car-loading operation (see plate IIB). 80 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 CRUSHING AND SCREENING EQUIPMENT No. 7^ Plant. The No. 7| crushing plant equipment consists of the No. 71 McCully and a No. 4 Telsmith. This latter crusher will soon be replaced by a No. 636 Allis-Chalmers. The screening equipment is made up of a 4' x 10' revolving scalping screen and a 4' x 10' Robins Gyrex two-deck sizing screen. The revolving scalper will soon be replaced by a two-deck vibrating screen. No. 8. This plant's crushing equipment consists of the No. 8 McCully, a 4-foot Symons cone with a coarse bowl, and a 6-inch McCully fine reduction crusher. The screening equipment is made up of a 4' X 10' revolving scalper, a 4' x 16' revolving scalper, a 4' x 10'6" Robins Eliptex single deck scalper and two 5' x 20' revolving sizing screens with jackets. This latter equipment will be removed in the near future and replaced with vibrating screens, REGRINDING PLANT A regrinding plant for the production of the smaller sizes of rock is located near the No. 7^ plant. The crushing equipment is made up of a 4-foot Symons with a fine bowl, a 3-foot Symons short head and a 6-inch McCully fine reduction crusher. The screening equipment con- sists of a 4' X 8' Niagara, a 4' x 10' Allis-Chalmers low head, a Robins 4' X 10'6" Eliptex and a Robins 4' x 14' Eliptex. All the screens have two decks. NEW PLANT OPERATIONS A 48" X 60" primary jaw crushing plant is being constructed at the lower or Southern Pacific track level. This will be in operation in the early part of 1946. The quarry fines will be removed by feeding the shovel-loaded rock over heavy bar-grizzlies by means of a 9'-0 wide pan feeder. The heavy quarry rock when reduced in size by this large crusher will be carried by a conveyor belt to the No. 7| and No. 8 crusher plant chutes located on the 100-foot level. It will be fed to the existing crushers which will then serve as secondary rather than primary ones. The balance of the existing plant operations will remain essentially the same except for improvements in equipment. Screening facilities are being increased as rapidly as feasible, to divide the rock into more sizes, and to make the sized rock more uniform. The resulting products will give less segregation and more accurate com- bined mixes. The customer requiring a smaller spread in size, particu- larly in rock for highway maintenance work, can be more readily supplied. USES OF GRANITE ROCK AND GRANITE CRUSHER-RUN BASE Some of the main uses of crushed granite rock are : portland-cement concrete pavements, structures, walks, floors, pipe; railroad ballast, asphalt concrete, plant-mix surfacing, Virginia mix, parking-area surfaces, screenings, sewage-disposal plant filters, water-supply filters, chicken and turkey grits, penetration-asphalt macadam, armor coat, retreads, seal coats, drains, and rip-rap. I GRANITE ROCK COMPANY — FOWLE 81 Some of the main uses of granite crusher-run base are : bases for highways, runways, parking areas, hard-standing areas, warehouse and factory floors, driA^eways, and walks. It has been successf ull,y used as fill and base material on unstable or sandy soils in connection with railway and highway construction. OTHER EQUIPMENT I Testing Materials Laboratory. The Granite Rock Company has a " well-equipped testing materials laboratory used not only bj^ its own personnel, but also open to all engineers and laboratory technicians wishing to make use of its facilities. Machine and Blacksmith Shop. The machine and blacksmith shops contain modern equipment for the repair, manufacture, and mainte- nance of all plant and rolling equipment. Abrasive-resistant chute liners, cast-manganese chutes, metal-spray, and hard-surface rod are a few of the materials used to reduce maintenance costs. Electrical Department. The electrical department not only does the maintenance and repair of all the electrical equipment, but also the electrical installation and construction. Plant Maintenance and Repairs. Maintenance and repair work are done by the plant personnel, in conjunction with the machine and black- smith shop force. Shovel Maintenance and Bepairs. The shovel crews maintain and repair their equipment, working in conjunction with the electrical department and machine shop. Loading Department. The loading department keeps check on the bunker material levels, the combination of bunker sizes for combined mixes, along with the re-sizing, washing, and shipping of the materials ordered. 6 — 51298 I SERVICES OF THE DIVISION OF MINES The Division of Mines (formerly State Mining Bureau) is main- tained for the purpose of assisting in all possible ways in the develop- ment of California's mineral resources. As one means of offering tangible service to the mining public, the State Mineralogist for many years has issued an annual or a biennial report reviewing in detail the mines and mineral deposits of the various counties. As a progressive step in advancing the interests of the mineral industry, and as permitting earlier distribution to the public, publica- tion of the Annual Report of the State Mineralogist in the form of monthly chapters was begun in January 1922, and continued until March 1923. Owing to a lack of funds for printing this was changed to a quarterly publication, beginning in September 1923. For the same reason, beginning with the January 1924 issue, it became necessary to charge a subscription price. This covers approximately the cost of printing. Pages are numbered consecutively throughout the year and an index to the complete report is included annually in the closing number. Beginning with the 1930 issues, the activities and progress of the Geologic Branch are recorded also in these quarterly chapters. The important part that geology plays in the economic development of our mineral resources is further recognized in the change of title from Mining in California to California Journal of Mines and Geology, beginning with the January 1933 chapter. While current activities of all descriptions are covered in these chapters, the practice of issuing from time to time technical reports on special subjects will be continued as well. A list of such reports now available is appended hereto, and the names of new bulletins will be added in the future as they are completed. The chapters are subject to revision, correction and improvement. Constructive suggestions from the mining public will be gladly received, and are invited. The one aim of the Division of Mines is to increase its usefulness and to stimulate the intelligent development of the wonderful, latent resources of the State of California. TYPES OF REPORTS In general the reports presented in these chapters are grouped into three classes : 1. Mines and mineral resources of a given county or area (describ- ing kind, character, distribution and extent of development). 2. Specific economic and industrial mineral products (listing and describing the resources over the entire State of a given mineral sub- stance, e.g., feldspar). 3. Geological reports on specific areas (recording results and con- clusions with maps, derived from field studies ; and tied in with economic possibilities and developments). (83) 84 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 Reports of District iVIining Engineers In 1919-1920 the Mining Bureau was organized into four main geographical divisions, with the field work delegated to a mining engi- neer in each district, working out from field offices that were established in Redding, Auburn, San Francisco and Los Angeles, respectively. This move brought the office into closer personal contact with operators, and it has many advantages over former methods of conducting field work, including lower traveling-expense bills for the Bureau's engineers. In 1923 the Redding and Auburn field offices were consolidated and moved to Sacramento. The Redding office was reestablished in 1928, and the boundaries of each district adjusted. The counties now included in each of the four divisions and the locations of the branch offices are shown on the frontispiece outline map of the State. Reports of mining activities and development in each district, pre- pared by the District Engineer, will continue to appear under the proper field division heading. Special Articles Detailed technical reports on special subjects, the result of research work or extended field investigations, will continue to be issued as separate bulletins by the Division, as has been the custom in the past. Shorter and less elaborate technical papers and articles by members of the staff and others are published in each number of California Journal of Mines and Geology. These special articles cover a wide range of subjects both of historical and current interest; descriptions of new processes, or metallurgical and industrial plants, new mineral occurrences, and interesting geo- logical formations, as well as articles intended to supply practical and timely information on the problems of the prospector and miner, such as the text of new laws and official regulations and notices affecting the mineral industry. MAIL AND FILES The Division of Mines maintains, in addition to its correspondence files and the library, a mine file which includes original reports on the various mines and mineral properties of all kinds in California. During each quarterly period there are several thousand letters received and answered at the San Francisco office alone, covering almost every phase of prospecting, mining and developing mineral deposits, reduction problems, marketing of refined products and mining law. In addition to this, hundreds of oral questions are answered daily, both at the main office and the district offices, for the many inquirers who come in for personal interviews and to consult the files and library. The library has a card-file system for references to individual Cali- fornia mines, occurring in the publications of the Division of Mines, in the Mining and Scientific Press, the Engineering and Mining Journal, and the Arizona Mining Journal. COMIVIERCIAL MINERAL NOTES | The producer and consumer of mineral products are mutually dependent upon each other for their prosperity, and one of the most direct aids rendered by this Division to the mining industry in the past SERVICES OF THE DIVISION OF MINES 85 has been that of bringing producers and consumers into direct touch with each other. This work has been carried on largely by correspondence, supple- mented by personal consultation. Lists of buyers of all the commercial minerals produced in California have been made available to producers upon request, and likewise the owners of undeveloped deposits of various minerals, and producers of them, have been made known to those looking for raw mineral products. When the publication of Mining in California was on a monthly basis, current inquiries from buyers and sellers were summarized and lists of mineral products or deposits 'wanted' or 'for sale' included in each issue. It is important that inquiries of this nature reach the mining public as soon as possible and in order to avoid the delay incident to the present quarterly publication of California Journal of Mines and Geology, these lists are now issued monthly in the form of a mimeographed sheet under the title of Commercial Mineral Notes, and sent to those on the mailing list of California Journal of Mines and Geology. EMPLOYMENT SERVICE Following the establishment of the Mining Division branch offices in 1919, a free technical employment service was offered as a mutual aid to mine operators and technical men for the general benefit of the mineral industry. Briefly summarized, men desiring positions are registered, the cards containing an outline of the applicant's qualifications, position wanted, salary desired, etc., and as notices of 'positions open' are received, the names and addresses of all applicants deemed qualified are sent to the prospective employer for direct negotiations. Telephone and telegraphic communications are also given imme- diate attention. Technical men, or those qualified for supervisory positions, and vacancies of like nature only, are registered, as no attempt will be made to supply mine and mill labor. Registration cards for the use of both prospective employers and employees may be obtained upon request, and a cordial invitation is extended to the industry to make free use of the facilities afforded. Parties interested should communicate direct with our San Francisco office. DETERMINATION OF MINERAL SAMPLES Samples (limited to two in one month) of any mineral found in the State may be sent to the Division of Mines for identification, and the same will be classified free of charge. No samples will be determined if received from points outside the State. It must be understood that no assays, or quantitative determinations will be made. Samples should be in lump form if possible, and marked plainly with name of sender on outside of package, etc. No samples will be received unless delivery charges are prepaid. A letter should accompany sample, giving locality where mineral was found and the nature of the information desired. PUBLICATIONS OF TUB DIVISION OF MINES During the past sixty-five years, in carrying out the provisions of the organic act creating the former California State Mining Bureau, there have been published many reports, bulletins and maps which go to make up a library of detailed information on the mineral industry of the State, a large part of which could not be duplicated from any other source. One feature that has added to the popularity of the publications is that many of them have been distributed without cost to the public, and even the more elaborate ones have been sold at a price which barely covers the cost of printing. Owing to the fact that funds for the advancing of the work of this department have usually been limited, the reports and bulletins men- tioned are printed in limited editions many of which are now entirely exhausted. Copies of such publications are available for reference, however, in the offices of the Division of Mines, in the Ferry Building, San Francisco 11 ; State Building, Los Angeles 12 ; State Office Building No. 1, Sacramento 14 ; Redding ; and Division of Oil and Gas at Santa Barbara, Santa Paula, Taft, Bakersfield, Coalinga. They may also be found in many public, private and technical libraries in California and other states and foreign countries. A catalog of all publications from 1880 to 1917, giving a synopsis of their contents, is issued as Bulletin No. 77. Publications in stock may be obtained postpaid by addressing the San Francisco, Los Angeles or Sacramento offices and enclosing the requisite amount. Remittances of stamps in an amount not to exceed 26 cents, cur- rency or coin will be accepted at sender's risk. Payment is preferred in the form of money orders. Money orders should be made payable to the Division of Mines. Write for latest revised price list. Note. — The Division of Mines frequently receives requests for some of the early Reports and Bulletins now out of print, and it will be appreciated if parties having such publications and vp'ishing to dispose of them will advise this office. (87) 88 SAN JUAN BAUTISTA QUADRANGLE [Bull. 133 REPORTS Price (including Asterisks (♦*) indicate the publication is out of print. postage and sales tax) ** Report I of the State Mineralogist, 1880, 43 pp. Henry G. Hanks ** Report II of the State Mineralogist, 1882, 514 pp., 4 illustrations, 1 map. Henry G. Hanks ** Report III of the State Mineralogist, 1883, 111 pp., 21 illustrations. Henry G. Hanks **Report IV of the State Mineralogist, 1884, 410 pp., 7 illustrations. Henry G. Hanks **Report V of the State Mineralogist, 1885, 234 pp., 15 illustrations, 1 geo- logical map. Henry G. Hanks **Report VI of the State Mineralogist, Part 1, 1886, 145 pp., 3 illustrations, 1 map. Henry G. Hanks Part II, 1887, 222 pp., 36 illustrations. William Irelan, Jr Price $0.75, sales tax $0.02 $0.77 ** Report VII of the State Mineralogist. 1887, 315 pp. AVilliam Irelan, Jr. **Report VIM of the State Mineralogist, 1888, 948 pp., 122 illustrations. William Irelan, Jr Report IX of the State Mineralogist, 1889, 352 pp., 57 illustrations, 2 maps. William Irelan, Jr Price $1.15, sales tax $0.03 1.18 ** Report X of the State Mineralogist, 1890, 983 pp., 179 illustrations, 10 maps. William Irelan, Jr Report XI (First Biennial) of the State Mineralogist, for the two years end- ing September 15, 1892, 612 pp., 73 illustrations, 4 maps. William Irelan, Jr. Price $1.50, sales tax $0.04 1.54 ** Report XII (Second Biennial) of the State Mineralogist, for the two years ending September 15, 1894, 541 pp., 101 illustrations, 5 maps. J. J. Crawford ** Report XIII (Third Biennial) of the State Mineralogist, for the two years ending September 15, 1896, 726 pp., 93 illustrations, 1 map. J. J. Crawford Chapters of the State Mineralogist's Report XIV, Biennial Period, 1913-1914, Fletcher Hamilton : **Mines and Mineral Resources, Amador, Calaveras and Tuolumne Coun- ties, 172 pp., paper Mines and Mineral Resources, Colusa, Glenn, Lake, Marin, Napa, Solano, Sonoma and Yolo Counties, 208 pp., paper_Price $0.50, sales tax $0.01 .51 Mines and Mineral Resources, Del Norte, Humboldt and Mendocino Coun- ties, 59 pp., paper Price $0.35, sales tax $0.01 .36 Mines and Mineral Resources, Fresno, Kern, Kings, Madera, Mariposa, Merced, San Joaquin and Stanislaus Counties, 220 pp., paper Price $0.75, sales tax $0.02 .77 Mines and Mineral Resources of Imperial and San Diego Counties, 113 pp., paper Price $0.50, sales tax $0.01 .51 **Mines and Mineral Resources, Shasta, Siskiyou and Trinity Counties, 180 pp., paper ** Report XIV of the State Mineralogist, for the Biennial Period 1913-1914, Fletcher Hamilton, 1915 : A General Report on the Mines and Mineral Resources of Amador, Calaveras, Tuolumne, Colusa, Glenn, Lake, Marin, Napa, Solano, Sonoma, Yolo, Dei Norte, Humboldt, Mendocino, Fresno, Kern, Kings, Madera, Mariposa, Merced, San Joaquin, Stanislaus, San Diego, Imperial, Shasta, Siskiyou and Trinity Counties, 974 pp., 275 illustrations, cloth Chapters of the State Mineralogist's Report XV, Biennial Period, 1915-1916, Fletcher Hamilton : **Mines and Mineral Resources, Alpine, Inyo and Mono Counties, 176 pp., paper Mines and Mineral Resources, Butte, Lassen, Modoc, Sutter and Tehama Counties, 91 pp., paper Price $0.50, sales tax $0.01 .51 **Mines and Mineral Resources, El Dorado, Placer, Sacramento and Yuba Counties, 198 pp., paper DIVISION OF MINES PUBLICATIONS 89 REPORTS— Continued Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) **Mines and Mineral Resources, Monterey, San Benito, San Luis Obispo, Santa Barbara and Ventura Counties, 183 pp., paper **Mines and Mineral Resources, Los Angeles, Orange and Riverside Coun- ties, 136 pp., paper **Mines and Mineral Resources, San Bernardino and Tulare Counties, 186 pp., paper ♦♦Report XV of the State Mineralogist, for the Biennial Period 1915-1916, Fletcher Hamilton, 1917 : A General Report on the Mines and Mineral Resources of Alpine, Inyo, Mono, Butte, Lassen, Modoc, Sutter, Tehama, Placer, Sacramento, Yuba, Los Angeles, Orange, Riverside, San Benito, San Luis Obispo, Santa Barbara, Ventura, San Bernardino and Tulare Coun- ties, 990 pp., 413 illustrations, cloth Chapters of the State Mineralogist's Report XVi, Biennial Period, 1917- 1918, Fletcher Hamilton : **Mines and Mineral Resources of Nevada County, 270 pp., paper Mines and Mineral Resources of Plumas County, 188 pp., paper Price $0.50, sales tax $0.01 $0.51 Mines and Mineral Resources of Sierra County, 144 pp., paper Price $0.75, sales tax $0.02 .77 Report XVII of the State Mineralogist, 1920, 'Mining in California during 1920,' Fletcher Hamilton ; 562 pp., 71 illustrations, cloth Price $2.50, sales tax $0.06 2.56 Report XVIII of the State Mineralogist, 1922, 'Mining in California,' Fletcher Hamilton. Chapters published monthly beginning with January, 1922 : ** January, **February, **March, April, May, June, July, August, September, October, November, December, 1922 Price $0.30, sales tax $0.01 .31 Chapters of Report XIX of the State Mineralogist, 'Mining in California,' Fletcher Hamilton and Lloyd L. Root. January, February, March, September, 1923 Price $0.30, sales tax $0.01 .31 Chapters of Report XX of the State Mineralogist, 'Mining in California,' Lloyd L. Root. Published quarterly. January, April,** July, October, 1924, per copy Price $0.30, sales tax $0.01 .31 Chapters of Report XXI of the State Mineralogist, 'Mining in California,' Lloyd L. Root. Published quarterly : January, 1925. Mines and Mineral Resources of Sacramento, Monterey and Orange Counties Price $0.30, sales tax $0.01 .31 **April, 1925. Mines and Mineral Resources of Calaveras, Merced, San Joaquin, Stanislaus and Ventura Counties **July, 1925. Mines and Mineral Resources of Del Norte, Humboldt and San Diego Counties ♦♦October, 1925. Mines and Mineral Resources of Siskiyou, San Luis Obispo and Santa Barbara Counties Chapters of Report XXII of the State Mineralogist, 'Mining in California,' Lloyd L. Root. Published quarterly : ♦♦January, 1926. Mines and Mineral Resources of Trinity and Santa Cruz Counties ♦♦April, 1926. Mines and Mineral Resources of Shasta, San Benito and Imperial Counties July, 1926. Mines and. Mineral Resources of Marin and Sonoma Coun- ties Price $0.30, sales tax $0.01 .31 ♦♦October, 1926. Mines and Mineral Resources of El Dorado and Inyo Coun- ties, also report on Minaret District, Madera County Chapters of Report XXIII of the State Mineralogist, 'Mining in California,' Lloyd L. Root. Published quarterly : January, 1927. Mines and Mineral Resources of Contra Costa County ; Santa Catalina Island Price $0.30, sales tax $0.01 .31 90 SAN JUAN BAUTISTA QUADRANGLE REPORTS— Continued Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) April, 1927. Mines and Mineral Resources of Amador and Solano Counties Price $0.30, sales tax $0.01 $0.31 **July, 1927. Mines and Mineral Resources of Placer and Los Angeles Coun- ties October, 1927. Mines and Mineral Resources of Mono County Price $0.30, sales tax $0.01 .31 Chapters of Report XXIV of the State Mineralogist, 'Mining in California,' Lloyd L. Root. Published quarterly : January, 1928. Mines and Mineral Resources of Tuolumne County Price $0.30, sales tax $0.01 .31 April, 1928. Mines and Mineral Resources of Mariposa County Price $0.30, sales tax $0.01 .31 **July, 1928. Mines and Mineral Resources of Butte and Tehama Counties October, 1928. Mines and Mineral Resources of Plumas and Madera Coun- ties Price $0.30, sales tax $0.01 .31 Chapters of Report XXV of the State Mineralogist, 'Mining in California,' Walter W. Bradley. Published quarterly: ** January, 1929. Mines and Mineral Resources of Lassen, Modoc and Kern Counties ; also on Special Placer Machines ♦*April, 1929. Mines and Mineral Resources of Sierra, Napa, San Francisco and San Mateo Counties July, 1929. Mines and Mineral Resources of Colusa, Fresno and Lake Counties Price $0.30, sales tax $0.01 .31 October, 1929. Mines and Mineral Resources of Glenn, Alameda, Mendo- cino and Riverside Counties Price $0.30, sales tax $0.01 .31 Chapters of Report XXVI of the State Mineralogist, 'Mining in California,' Walter W. Bradley. Published quarterly : January, 1930. Mines and Mineral Resources of Santa Clara County; also Barite in California Price $0.40, sales tax $0.01 .41 **April, 1930. Mines and Mineral Resources of Nevada County; also Min- eral Paint Materials in California **July, 1930. Mines and Mineral Resources of Yuba and San Bernardino Counties; also Commercial Grinding Plants in California October, 1930. Mines and Mineral Resources of Butte, Kings and Tulare Counties; also Geology of Southwestern Mono County (Preliminary) Price $0.40, sales tax $0.01 .41 Chapters of Report XXVII of the State Mineralogist, 'Mining in California,' Walter W. Bradley. Published quarterly : January, 1931. Preliminary Report of Economic Geology of the Shasta Quadrangle. Beryllium and Beryl. The New Tariff and Nonmetallic Products. Crystalline talc. Decorative effects in Concrete Price $0.40, sales tax $0.01 .41 April, 1931. Stratigraphy of the Kreyenhagen Shale. Diatoms and Sili- coflagellates of the Kreyenhagen Shale. Foraminifera of the Kreyen- hagen Shale. Geology of Santa Cruz Island Price $0.40, sales tax $0.01 .41 **July, 1931. (Yuba, San Bernardino Counties.) Feldspar, Silica, Anda- lusite and Cyanite Deposits of California. Note on a Deposit of Anda- lusite in Mono County; its occurrence and chemical importance. Bill creating Trinity and Klamath River Fish and Game District and its effect upon mining October, 1931. (Alpine County.) Geology of the San Jacinto Quad- rangle south of San Gorgonio Pass, California. Notes on Mining Activ- ities in Inyo and Mono Counties in July, 1931 Price $0.40, sales tax $0.01 .41 Chapters of Report XXVIII of the State Mineralogist, 'Mining in California,' Walter W. Bradley. Published quarterly : January, 1932, Economic Mineral Deposits of the San Jacinto Quad- rangle. Geology and Physical Properties of Building Stone from Car. mel Valley. Contributions to the Study of Sediments. Sediments of Monterey Bay. Sanbornite Price $0.40, sales tax $0.01 .41 DIVISION OF MINES PUBLICATIONS 91 REPORTS — Continued Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) **April, 1932. Elementary Placer Mining Methods and Gold Saving Devices. The Pan, Rocker and Sluice Box. Prospecting for Vein Deposits. Bibliography of Placer Mining ♦♦Abstract from April quarterly ; Elementary Placer Mining Methods and Gold Saving Devices. Types of Deposits, Simple Equipment. Special Machines. Dry Washing. Black Sand Treatment. Marketing of Products. Placer Mining Areas. Laws. Prospecting for Quartz Veins. Bibliography (mimeographed) **July-October, 1932. (Ventura County). Report accompanying Geologic Map of Northern Sierra Nevada. Fossil Plants in Auriferous Gravels of the Sierra Nevada. Glacial and Associated Stream Deposits of the Sierra Nevada. Jurassic and Cretaceous Divisions in the Knoxville Shasta Succession of California. Geology of a part of the Panamint Range. Economic Report of a Part of the Pana- mint Range. Acquiring Mining Claims Through Tax Title. The Biennial Report of State Mineralogist Chapters of Report XXIX, 1933 (quarterly) : titled 'California Journal of Mines and Geology,' containing the following : ** January-April, 1933. Gold Deposits of the Redding and Weaverville Quadrangles. Geologic Formations of the Redding-Weaverville Dis- trict, Northern California. Geology of Portions of Del Norte and Sis- kiyou Counties. Applications of Geology to Civil Engineering. The Lakes of California. Discovery of Piedmontite in the Sierra Nevada. Tracing 'Buried River' Channel Deposits by Geomagnetic Methods. Geologic Map of Redding-Weaverville District, showing gold mines and prospects. Geologic map showing various mines and prospects of part of Del Norte and Siskiyou Counties July-October, 1933. Gold Resources of Kern County. Limestone Deposits of the San Francisco Region. Limestone Weathering and Plant Associations of the San Francisco Region. Booming, Death Valley National Monument, California. Placer Mining Districts, Senate Bill 480. Navigable Waters, Assembly Bill 1543 Price $1.00, sales tax $0.03 $1.03 Chapters of Report XXX, 1934 (quarterly) : titled 'California Journal of Mines and Geology,' containing the following : January, 1934. Resurrection of Early Surfaces in the Sierra Nevada. Geology and Mineral Resources of Northeastern Madera County. Geology and Mineral Deposits of Laurel and Convict Basins, South- western Mono County. Notes on Sampling as Applied to Gold Quartz Deposits Price $0.60, sales tax $0.02 .62 April-July, 1934. Elementary Placer Mining in California and Notes on the Milling of Gold Ores Price $1.00, sales tax $0.03 1.03 October, 1934. Current Mining Developments in Northern California. Cur- rent Mining Activity in Southern California. Geology and Mineral Resources of the Julian District, San Diego County. Geology and Mineral Resources of Elizabeth Lake Quadrangle, Dry Placers of Northern Mojave Desert. Biennial Report of State Mineralogist. Assessment Work Within Withdrawn Areas Price $0.60, sales tax $0.02 .62 Chapters of Report XXX!, 1935 (quarterly) : titled 'California Journal of Mines and Geology,' containing the following : January, 1935. Review of Gold Mining in East-Central California, 1934. Current Mining Activities in the San Francisco District with Special Reference to Gold. Geological Investigation of the Clays of Riverside and Orange Counties, Southern California. Information regarding Mining Loans by the Reconstruction Finance Corporation Price $0.60, sales tax $0.02 .62 92 SAN JUAN BAUTISTA QUADRANGLE REPORTS — Continued Price (including Asterislcs (**) indicate the publication is out of print. postage and sales tax) April, 1935. A Geologic Section Across the Southern Peninsular Range of California. New Technique Applicable to the Study of Placers. Grubstakes Permits Price $0.60, sales tax $0.02 $0.62 July, 1935. Mines and Mineral Resources of Siskiyou County (with map). Dams for Hydraulic Mining Debris. Leasing System as Applied to Metal Mining. Mine Financing in California. New Laws Make Radical Change in Mining Rights Price $0.60, sales tax $0.02 .62 October, 1935. Mines and Mineral Resources of San Luis Obispo County. Mineral Resources of Portions of Monterey and Kings Counties. Mining Activity at Soledad Mountain and Middle Buttes — Mojave District Kern County. Geology of a Portion of the Perris Block, Southern California. Mineral Resources of a Portion of the Perris Block, Riverside County Price $0.60, sales tax $0.02 .'i2 Chapters of Report XXXll, 1936 (quarterly) : titled 'California Journal of Mines and Geology,' containing the following : January, 1936. Gold Mines of Placer County, including Drag-line Dredges Geologic Report on Borax Lake, California Price $0.60, sales tax $0.02 .62 April, 1936. Geology, Mining and Processing of Diatomite at Lompoc, Santa Barbara County. Essentials in Developing and Financing a Pro-spect into a Mine. Gold-bearing Veins of Meadow Lake District, Nevada Comity. Semi -Precious Gem Stone Collection in Division Museum 1 Price $0.60, sales tax $0.02 .62 July, 1936. Mines and Mineral Resources of Calaveras County. Mining in California by Power Shovel. Assessment Work on Mining Claims Within Withdrawn Areas. Joshua Tree National Monument. Cost of Producing Quicksilver at a California Mine in 1931-1932. The Age of Mineral Utilization Price $0.60, sales tax $0.02 .62 October, 1936. Mineral Resources of Lassen and Modoc Counties. Mechanics of Lone Mountain Landslides, San Francisco. Biennial Report of the State Mineralogist, Properties and Industrial applica- tions of Opaline Silica ^ Price $0.60, sales tax .$0.02 .62 Chapters of Report XXXIII, 1937 (quarterly) : titled 'California Journal of Mines and Geology,' containing the following : January, 1937. Source Data of the Geologic Map of California, January, 1937. The Geology of Quicksilver Ore Deposits. Prospecting for Lode Gold Price .$0.60, sales tax .$0.02 .62 April, 1937. Mineral Resources of Plumas County (with Geologic Map). List of preferred mineral names. New Placer Mining Debris Law. Price $0.60, sales tax $0.02 .62 July, 1937. Mineral Resources of Los Angeles County (with map showing principal Mines and Oil Fields). Geology and mineral deposits of the Western San Gabriel Mountains, Los Angeles County Price $0.60, sales tax $0.02 .62 October, 1937. Mineral Resources of the Resting Springs Region, Inyo County. Paleozoic Section in the Nopah and Resting Springs Moun- tains, Inyo County, California. Native Arsenic from Grass Valley. California Price $0.60, sales tax $0.02 .62 Chapters of Report XXXIV, 19-3S (quarterly) : titled 'California Journal of Mines and Geology,' containing the following : **January. 1938. Mineral Development and Mining Activity in Southern California during the year 1937. Doing Something About Earth- quakes. Gold and Petroleum in California. Gem Minerals of Cali- fornia, Lapidary Art April, 1938. Gold dredging in Shasta, Siskiyou and Trinity Counties; Geology of the Central Santa Monica Mountains; Marketing Mica Price $0.60, sales tax $0.02 .62 July, 1938. El Dorado County, Mineral High-Lights of California; Strategic Minerals of California; Cyanide Treatment of Gossan at Mountain Copper Co.; Submarine Canyons off the California Coast. Price $0.60, sales tax $0.02 .62 DIVISION OF MINES PUBLICATIONS 93 REPORTS — Continued Price (including- Asterisks (**) indicate the publication is out of print. postage and sales tax) October, 1938. Inyo County, Biennial Report of State Mineralogist, Sul- phur Deposits of Inyo County, Geology of the Darwin Silver- Lead Mining District Price $0.60, sales tax $0.02 $0.62 Chapters of Report XXXV, 19S9 (quarterly) titled "California Journal of Mines and Geology," containing the following : January, 1939. San Diego County, Geology and Oil Possibilities of South- western San Diego Co.; Prospect for 'Minor Metals' and Nonmetallic Minerals; The Right to Mine Price $0.60, sales tax $0.02 .62 April, 1939. Shasta County, Public's Interest in Mine Taxation Price $0.60, sales tax $0.02 .62 July, 1939. Tertiary Formations of Northern Sacramento Valley, Cali- fornia ; Geology and Oil Possibilities of Caliente Range, Cuyama Valley and Carrizo Plain, California; Bibliography of the Geology and Mineral Resources of California for the year 1937 ; The Giant Goose Lake Meteorite from Modoc County, California Price $0.60, sales tax $0.02 .62 **Oetober, 1939. Quicksilver Resources of California; Sulphate Minerals of the Leviathan Sulphur Mine, Alpine County, California Quicksilver Resources of California. Reprint Price $0.50, sales tax $0.01 .51 Chapters of Report XXXVI, 1940 (quarterly) titled "California Journal of Mines and Geology," containing the following : January, 1940. Current Mining Activity in Southern California ; Notes on Beryl with a Qualitative Analysis for Beryllium; Strategic Minerals Investigations Procedure followed by the U. S. Bureau of Mines Price $0.60, sales tax $0.02 .62 April, 1940. Mineral Resources of Mono County; General Geology and Ores of the Blind Spring Hill Mining District, Mono County, Califor- nia ; Short Report on the Geological Formations Encountered in Driv- ing the Mono Craters Tunnel; Methods and Costs of Mining and Concentrating Chromite Price $0.60, sales tax .$0.02 .62 July, 1940. Economic Mineral Deposits of the Newberry and Ord Moun- tains, San Bernardino County; Geology of the Newberry and Ord Mountains, San Bernardino County, California ; Notes on the Geology of a Portion of the Calico Mountains, San Bernardino County, Cali- fornia ; Study of Chrome Process Aided by Martin Dennis Company Price $0.60, sales tax $0.02 .62 October, 1940. Mineral Resources of the Kernville Quadrangle; Strategic Problems of the Mineral Industry in California ; Descriptive Geology of the Kernville Quadrangle, California ; Biennial Report of the State Mineralogist; Strategic Tax Exemption; Federal Loans for Strategic Minerals Price $0.60, sales tax $0.02 .62 Chapters of Report XXXVII, 1941 (quarterly) titled "California Journal of Mines and Geology," containing the following : January, 1941. Mineral Resources of Trinity County ; Strategic Minerals Procurement; Geologic Investigation of the Chromite Deposits of California ; United States Supreme Court Renders Far-reaching Deci- sion on Power Permits on "Navigable" Streams; Securities and Exchange Commission Price $0.60, sales tax $0.02 .62 April, 1941. Tungsten Resources of California; Geological Progress of State Division of Mines ; California Earthquakes of Mission Period, 1769-1838; Marketing of Talc, Pyrophyllite and Ground Soap-Stone Price $0.60, sales tax $0.02 .62 July, 1941. Nevada Co., report and map Price $0.60, sales tax $0.02 .62 October, 1941. Humboldt County report. Tin in California; California Quicksilver Program by the U. S. Geological Survey; Recent Tung- sten Developments; Manganese and Chrome Ore Specifications and Prices; Does Scheelite always Fluoresce? Bentonite Price $0.60, sales tax $0.02 .62 94 SAN JUAN BAUTISTA QUADRANGLE REPORTS — Continued Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) Chapters of Report XXXVIII, 1942 (quarterly), titled "California Journal of Mines and Geology," containing the following : January, 1942. Sierra County report. Chromium in California Price $0.60, sales tax $0.02 $0.62 April, 1942. Imperial County report and map. Geology and Mineral Deposits of Cargo Muchacho Mountains Price $0.60, sales tax $0.02 .62 July-October, 194Z Contact Metamorphic Rocks of the Twin Lakes Region; Tabulated List of Tungsten Properties; Geology of Welsh Tungsten Prospect, iVladera Co.; Tungsten Deposits in Confidence Mining District, Tuolumne Co.; Ghost Canyon Tungsten Claims, Madera Co.; Hot Springs Deposits, Coso Mountains; Biennial Report of State Mineralogist ; includes map showing Tungsten Prop- erties in California Price $1.20, sales tax $0.03 1.23 Chapters of Report XXXIX, 19i3 (quarterly), titled "California Journal of Mines and Geology," containing the following : January, 1943. (Santa Cruz County report and map.) Current Notes on mining Activities in Strategic Minerals. Organization and Serv- ic» of Division of Mines. Dept. of Interior Information Service by U. S. Geological Survey. Tom Cat, Tungsten Property, Tulare Co. Price $0.60, sales tax $0.02 .62 April, 1943. Manganese Discovery in San Mateo County. Current Activ- ities in Strategic Minerals. Clerbus-Mae Tungsten Prospect, Trinity County. Mylonites of Eastern San Gabriel Mountains. Geology and Tungsten of Sierra Nevada N. E. of Visalia, Tulare County. Geology of San Benito Quadrangle, with map. Lithium. Quartz Price $0.60, sales tax $0.02 .62 July, 1943. Carbon Dioxide, Mendocino and Southern Sonoma Counties. Current Activities in Strategic Minerals. Crestmore Minerals. Isometrograph as Developed and Used at New Idria Mine. Sutter (Marysville) Gas Field. Sillimanite Group of Minerals. New Fed- eral and State Legislation Price .$0.60, sales tax $0.02 .62 October, 1943. San Bernardino County report and map. Current Notes on Activity in Strategic Minerals Biennial Report of State Mineralogist Price $0.60, sales tax $0.02 .62 Chapters of Report XL, 1944 (quarterly), titled "California Journal of Mines and Geology," containing the following : January, 1944. Geology of Palm Springs-Blyth, Riverside County. Geol- ogy of Parts of Barstow Quadrangle, San Bernardino County. Geol- ogy of Needles-Goffs Region, San Bernardino County. Airox Concrete Aggregate. Marketing Magnesite and Allied Products Price $0.60, sales tax $0.02 .62 April, 1944. Status of Topographic and Geologic Mapping. Geology of Jamesburg Quadrangle Monterey County. List of Libraries having Division of Mines Publications Price $0.60, sales tax $0.02 .62 July, 1944. Mines and Quarries of the Indians of California. Fluorescent Minerals in Exhibit of Division of Mines. Fluorescent Minerals used in Lighting and Elsewhere Price $0.60, sales tax $0.02 .62 October, 1944. Biennial Report of State Mineralogist. Pellet- Phospho- rite from Carmel Valley. Geology of Quartz Crystal Mine near Mokelumne Hill, Calaveras County. Strategic Mica. Marketing Vermiculite. Act Regulating Mineral, Oil, and Gas Brokers and Salesmen Price $0.60, sales tax $0.02 .62 Chapters of Report XLI, 1945 (quarterly), titled "California Journal of Mines and Geology," containing the following : January, 1945. Quicksilver Deposits of Central San Benito and North- western Fresno Counties; War-Time Mineral Industry Price $0.60, sales tax $0.02 .62 April 1945. Quicksilver Deposits of Knoxville District; Unexpected Use of Quicksilver; Story of Steel Price $0.60, sales tax $0.02 .62 DIVISION OF MINES PUBLICATIONS 95 BULLETINS Price (including Asterisks (•*) indicate the publication is out of print. postage and sales tax) •♦Bulletin No. 1. Description of Some Desiccated. Human Remains, by Winslow Anderson. 1888, 41 pp., 6 illustrations ♦♦Bulletin No. 2. Methods of Mine Timbering, by W, H. Storms. 1894, 58 pp., 75 illustrations ♦♦Bulletin No. 3. Gas and Petroleum Yielding Formations of Central Val- ley of California, by W. L. Watts. 1894, 100 pp., 13 illustrations, 4 maps ♦♦Bulletin No. 4. Catalogue of California Fossils, by J. G. Cooper, 1894, 73 pp., 67 illustrations. (Part I was published in the Seventh Annual Report of the State Mineralogist, 1887) ♦♦Bulletin No. 5. The Cyanide Process, 1894, by Dr. A. Scheidel. 140 pp., 46 illustrations ♦♦Bulletin No. 6. California Gold Mill Practices, 1895, by E. B. Preston, 85 pp., 46 illustrations ♦♦Bulletin No. 7. Mineral Production of California, by Counties, for the year 1894, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 8. Mineral Production of California, by Counties, for the year 1895, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 9. Mine Drainage, Pumps, etc., by Hans C. Behr. 1896, 210 pp., 206 illustrations ♦♦Bulletin No. 10. A Bibliography Relating to the Geology, Paleontology and Mineral Resources of California, by Anthony W. Vogdes. 1896, 121 pp. ♦♦Bulletin No. 11. Oil and Gas Yielding Formations of Los Angeles, Ven- tura and Santa Barbara Counties, by W. L. Watts. 1897, 94 pp., 6 maps, 31 illustrations ♦♦Bulletin No. 12. Mineral Production of California, by Counties, for 1896, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 13. Mineral Production of California, by Counties, for 1897, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 14. Mineral Production of California, by Counties, for 1898, by Charles G. Yale ♦♦Bulletin No. 15. Map of Oil City Fields, Fresno County, by John H. Means, 1899 ♦♦Bulletin No. 16. The Genesis of Petroleum and Asphaltum in Califor- nia, by A. S. Cooper. 1899, 39 pp., 29 illustrations ♦♦Bulletin No. 17. Mineral Production of California, by Counties, for 1899, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 18. Mother Lode Region of California, by W. H. Storms, 1900, 154 pp., 49 illustrations ♦♦Bulletin No. 19. Oil and Gas Yielding Formations of California, by W. L. Watts. 1900, 286 pp., 60 illustrations, 8 maps ♦♦Bulletin No. 20. Synopsis of General Report of State Mining Bureau, by W. L. Watts. 1901, 21 pp. This bulletin contains a brief state- ment of the progress of the mineral industry in California for the four years ending December, 1899 **Bulletin No. 21. ^lincral Production of California, by Counties, by Charles G. Yale. 1900. Tabulated sheet ♦♦Bulletin No. 22. Mineral Production of California for Fourteen Years, by Charles G. Yale. 1900. Tabulated sheet Bulletin No. 23. The Copper Resources of California, by P. C. DuBois, F. M. Anderson, J. H. Tibbits and G. A. Tweedy. 1902, 282 pp., 69 illustrations, 9 maps Price $0.75, sales tax $0.02 $0.77 ♦♦Bulletin No. 24. The Saline Deposits of California, by G. E. Bailey, 1902, 216 pp., 99 illustrations, 5 maps ♦♦Bulletin No. 25. Mineral Production of California, by Counties, for 1901, by Charles G. Yale, Tabulated sheet ♦♦Bulletin No. 26. Mineral Production of California for the Past Fifteen Years, by Charles G. Yale. 1902. Tabulated sheet 96 SAN JUAN BAUTISTA QUADRANGLE BULLETINS— Continued Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) **Bulletin No. 27. TheQuicksilver Resources of California, by William Forstner. 1903, 273 pp., 144 illustrations, 8 maps **Bulletin No. 28. Mineral Production of California for 1902, by Charles G. Yale. Tabulated sheet **Bulletin No. 29. Mineral Production of California for Sixteen Years, by Charles G. Yale. 1903. Tabulated sheet ♦♦Bulletin No. 30. Bibliograpliy Relating to the Geology, Paleontology and Mineral Resources of California, by A. W. Vogdes. 1903, 290 pp ♦♦Bulletin No. 31. Chemical Analyses of California Petroleum, by H. N. Cooper. 1904. Tabulated sheet ♦♦Bulletin No. 32. Production and Use of Petroleum in California, by Paul W. Prutzman. 1904, 230 pp., 116 illustrations, 14 maps ♦♦Bulletin No. 33. Mineral Production of California, by Counties, for 1903, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 34. Mineral Production of California for Seventeen Years, by Charles G. Yale. 1904. Tabulated sheet ♦♦Bulletin No. 35. Mines and Minerals of California, by Charles G. Yale, 1904, 55 pp., 20 county maps. Relief map of California ♦♦Bulletin No. 36. Gold Dredging in California, by J. E. Doolittle. 1905. 120 pp., 60 illustrations, 3 maps ♦♦Bulletin No. 37. Gems, Jewelers' Materials, and Ornamental Stones of California, by George F. Kunz. 1905, 168 pp., 54 illustrations ♦♦Bulletin No. 38. Structural and Industrial Materials of California, by Wm. Forstner, T. C. Plopkins, C. Naramore and L. H. Eddy. 1906, 412 pp., 150 illustrations, 1 map ♦♦Bulletin No. 39. Mineral Production of California, by Counties, for 1904, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 40. Mineral Production of California for Eighteen Years, by Charles G. Yale. 1905. Tabulated sheet ♦♦Bulletin No. 41. Mines and Minerals of California for 1904, by Charles G. Yale. 1905, 54 pp., 20 county maps ♦♦Bulletin No. 42. Mineral Production of California, by Counties, 1905, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 43. Mineral Production of California for Nineteen Years, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 44. California Mines and Minerals for 1905, by Charles G. Yale. 1907, 31 pp., 20 county maps ♦♦Bulletin No. 45. Auriferous Black Sands of California, by J. A. Edman, 1907. 10 pp ♦♦Bulletin No. 46. General Index of Publications of the California State Mining Bureau, by Charles G. Y'ale. 1907, 54 pp ♦♦Bulletin No. 47. Mineral Production of California, by Counties, 1906, by Charles G. Yale. Tabulated sheet ♦♦Bulletin No. 48. Mineral Production of California for Twenty Years, by Charles G. Yale. 1906 ♦♦Bulletin No. 49. Mines and Minerals of California for 1906, by Charles G. Yale. 34 pp Bulletin No. 50. The Copper Resources of California, 1908, by A. Haus- mann, J. Kruttschnitt, Jr., W. E. Thorn and J. A. Edman, 366 pp., 74 illustrations. (Revised edition) Price $1.50, sales tax $0.04 $1.54 ♦♦Bulletin No. 51. Mineral Production of California, by Counties, 1907, by D. H. Walker. Tabulated sheet ♦♦Bulletin No. 52. Mineral Production of California for Twenty-one Years, by D. H. Walker, 1907. Tabulated sheet ♦♦Bulletin No. 53. Mineral Production of California for 1907, with County Maps, by D. H. Walker, 62 pp ♦♦Bulletin No. 54. Mineral Production of California, by Counties, by D. H. Walker, 1908. Tabulated sheet ♦♦Bulletin No. 55. Mineral Production of California for Twenty-two Years, by D. H. Walker, 190S. Tabulated sheet DIVISION OF MINES PUBLICATIONS 97 BULLETINS— Continued Price (including Asterisks (•*) indicate the publication is out of print. postage and sales tax ) **Bulletin No. 56. Mineral Production for 1908, with County Maps and Mining Laws of California, by D. H. Walker, 78 pp ♦♦Bulletin No. 57. Gold Dredging in California, by W. B. Winston and Chas. Janin. 1910, 312 pp., 239 illustrations, 10 maps ♦♦Bulletin No. 58. Mineral Production of California, by Counties, by D. H. Walker. 1909. Tabulated sheet ♦♦Bulletin No. 59. Mineral Production of California for Twenty-three Years, by D. H. Walker. 1909. Tabulated sheet ♦♦Bulletin No. 60. Mineral Production for 1909, with County Maps and Mining Laws of California, by D. H. Walker. 94 pp ♦♦Bulletin No. 61. Mineral Production of California, by Counties, for 1910, by D. H. Walker. Tabulated sheet ♦♦Bulletin No. 62. Mineral Production of California for Twenty-four Years, by D. H. Walker. 1910. Tabulated sheet ♦♦Bulletin No. 63. Petroleum in Southern California, by P. W. Prutzman. 1912, 430 pp., 41 illustration, 6 maps ♦♦Bulletin No. 64. Mineral Production for 1911, by E. S. Boalich. 49 pp. ♦♦Bulletin No. 65. Mineral Production for 1912, by E. S. Boalich. 64 pp. ♦♦Bulletin No. 66. Mining Laws of the United States and California. 1914, 89 pp ♦♦Bulletin No. 67. Minerals of California, by Arthur S. Eakle. 1914, 226 pp. ♦♦Bulletin No. 68. Mineral Production for 1913, with County Maps and Mining Laws, by E. S. Boalich. 160 pp ♦♦Bulletin No. 69. Petroleum Industry of California, with Folio of Maps (18 by 22), by R. P. McLaughlin and C. A. Waring. 1914, 519 pp., 13 illustrations, 83 figs. [18 plates in accompanying folio.] ♦♦Bulletin No. 70. Mineral Production for 1914, with County Maps and Mining Laws. 184 pp ♦♦Bulletin No. 71. Mineral Production for 1915, with County Maps and Mining Laws, by Walter AV. Bradley, 193 pp. 4 illustrations ♦♦Bulletin No. 72. The Geologic Formations of California, by James Perrin Smith. 1916, 47 pp ♦♦Reconnaissance Geologic Map (of which Bulletin 72 is explanatory), in 23 colors. Scale: 1 inch = 12 miles. Mounted ♦♦Bulletin No. 73. First Annual Report of the State Oil and Gas Super- visor of California for the fiscal year 1915-16, by R. P. McLaughlin. 278 pp., 26 illustrations ♦♦Bulletin No. 74. Mineral Production of California in 1916, with County Maps, by Walter W. Bradley. 179 pp., 12 illustrations ♦♦Bulletin No. 75. United States and California Mining Laws. 1917, 115 pp., paper Bulletin No. 76. Manganese and Chromium in California, by Walter W. Bradley, Emile Huguenin, C. A. Logan, W. B. Tucker and C. A. War- ing. 1918, 248 pp., 51 illustrations, 5 maps, paper Price $0.75, sales tax $0.02 $0.77 Bulletin No. 77. Catalogue of Publications of California State Mining Bureau, 1880-1917, by E. S. Boalich. 44 pp., paper Free ♦♦Bulletin No. 78. Quicksilver Resources of California, with a Section on Metallurgy and Ore- Dressing, by Walter W. Bradley. 1919, 389 pp., 77 photographs and 42 plates (colored and line cuts), cloth Bulletin No. 79. Magnesite in California, by Walter W. Bradley. 1925, 147 pp., 62 photographs, 11 line cuts and maps, cloth Price $1.25, sales tax $0.03 1.28 tBulletin No. 80. Tungsten. Molybdenum and Vanadium in California. (Not issued— See Apr. 1941 Chapt. Report XXXVII.) tBulletin No. 81. Foothill Copper Belt of California. (Not issued.) t Not issued 7 — 51298 98 SAN JUAN BAUTISTA QUADRANGLE BULLETINS— Continued Price ( including' Asterisks (**) indicate tlie publication is out of print. poslase and sales tax) ♦♦Bulletin No. 82. Second Annual Report of the State Oil and Gas Super- visor, for the Fiscal Year 1916-1917, by R. P. McLaughlin. 1918, 412 pp., 31 illustrations, cloth ♦♦Bulletin No. S3. California Mineral Production for 1917, with County Maps, by Walter W. Bradley. 179 pp., paper ♦♦Bulletin No. 84. Third Annual Report of the State Oil and Gas Super- visor, for the Fiscal Year 1917-1918, by R. P. McLaughlin. 1918, 617 pp., 28 illustrations, cloth ♦♦Bulletin No. 85. Platinum and Allied Metals in California, by C. A. Logan, 1919. 10 photographs, 4 plates, 120 pp., paper ♦♦Bulletin No. 86. California Mineral Production for 1918, with County Maps, by Walter W. Bradley. 1919, 212 pp., paper ♦♦Bulletin No. 87. Commercial Minerals of California, with notes on their uses, distribution, properties, ores, field tests, and preparation for market, by W. O. Castello. 1920, 124 pp., paper ♦♦Bulletin No. 88. California Mineral Production for 1919, with County Maps, by Walter W. Bradley. 1920, 204 pp., paper ♦♦Bulletin No. 89. Petroleum Resources of California, with Special Ref- erence to Unproved Areas, by Lawrence Vander Leek. 1921, 12 figures, 6 photographs, 6 maps in pocket, 186 pp., cloth ♦♦Bulletin No. 90. California Mineral Production for 1920, with County Maps, by Walter W. Bradley. 1921, 218 pp., paper ♦♦Bulletin No. 91. Minerals of California, by Arthur S. Eakle. 1923, 328 pp., cloth ♦♦Bulletin No. 92. Gold Placers of California, by Charles S. Haley. 1923, 167 pp., 36 photographs and 7 plates (colored and line cuts, also geological map), cloth ♦♦Bulletin No. 93. California Mineral Production for 1922, by Walter W. Bradley. 1923, 188 pp., paper ♦♦Bulletin No. 94. California Mineral Production for 1923, by Walter W. Bradley. 1924, 162 pp., paper ♦♦Bulletin No. 95. Geology and Ore Deposits of the Randsburg Quad- rangle, by Carlton D. Hulin. 1925, 152 pp.,49 photographs, 13 line cuts, 1 colored geologic map, cloth ♦♦Bulletin No. 96. California Mineral Production for 1924, by Walter W. Bradley. 1925, 173 pp., paper ♦♦Bulletin No. 97. California Mineral Production for 1925, by Walter W. Bradley. 1926, 172 pp., paper Bulletin No. 98. American Mining Law, by A. H. Ricketts, 1931, 811 pp. flexible leather Price $2.50, sales tax $0.06 $2.56 Bulletin No. 99. Clay Resources and Ceramic Industry of California, by Waldemar Fenn Deitrich. 1928, 383 pp., 70 photogi-aphs, 12 line cuts including maps, cloth Price $2.00, sales tax $0.05 2.05 ♦♦Bulletin No. 100. California Mineral Production for 1926, by Walter W. Bradley, 1927, 174 pp., paper ♦♦Bulletin No. 101. California Mineral Production for 1927, by Henry H. Symons. 1928, 311 pp., paper ♦♦Bulletin No. 102. California Mineral Production for 1928, by Henry H. Symons. 1929, 210 pp., paper Bulletin No. 103. California Mineral Production for 1929, by Henry H. Symons. 1930, 231 pp., paper Bulletin No. 104. Bibliography of the Geology and Mineral Resources of California, to the end of 1930, by Solon Shedd Price $2.50, sales tax $0.06 2.56 ♦♦Bulletin No. 105. Mineral Production in California for 1930 and Direc- tory of Producers, by Henry H. Symons Bulletin No. 106. (See Bulletin No. 127.) Bulletin No. 107. Mineral Production in California for 1931 and Direc- tory of Producers, by Henry H. Symons I DIVISION OF MINES PUBLICATIONS 99 BULLETINS— Continued Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) Bulletin No. 108. Mother Lode Gold Belt of California, by Clarence A. Logan, 1934, 240 pp., with geologic and claim maps, cloth Price $2.25, sales tax $0.06 $2.31 Bulletin No. 109. Califoi-nia Mineral Production and Directory of Min- eral Producers for 1932, by Henry H. Symons, 200 pp., paper Bulletin No. 110. California Mineral Production and Directory of Min- eral Producers for 1933, by Henry H. Symons, 214 pp., paper Bulletin No. 111. California Mineral Production and Directory of Min- eral Producers for 1934, by Henry H. Symons, 334 pp., paper Bulletin No. 112. California Mineral Production and Directory of Min- eral Producers for 1935, by Henry H. Symons, 205 pp., paper **Bulletin No. 113. Minerals of California, by Adolf Pabst, 1938 Bulletin No. 114. California Mineral Production and Directory of Min- eral Producers for 1936, by Henry H. Symons, 199 pp., paper Bulletin No. 115. Bibliography of Geology and Mineral Resources of California, 1931, to 193G, Supplementing Bulletin No. 104 Price $1.25, sales tax $0.08 1.28 Bulletin No. 116. California Mineral Production and Directory of Min- eral Producers for 1937, by Henry H. Symons Bulletin No. 117. California Mineral Production and Directory of Min- eral Producers for 1938, by Henry H. Symons Bulletin No. 118. Geologic Formations and Economic Development of the Oil and Gas Fields of California. (Includes map showing Oil and Gas Fields.) PREPRINTS of 4 Parts (not sold separately) Price per set $4.00, sales tax $0.10 4.10 Part I. "Development of the Industry." Part II. Geology of California and the Occurrence of Oil and Gas. Part III. Descriptions of Individual Oil and Gas Fields. Part IV. General Index, Glossary and Bibliography. Complete in one volume, cloth bound Price $6.()0, sales tax $0.15 6.15 ♦♦Bulletin No. 119. Mineral Production of California for 1939, and Direc- tory of Producers, by Henry H. Symons Bulletin No. 120. Superseded. (See Bulletin 127.) Bulletin No. 121. Mineral Production of California for 1940, and Direc- tory of Producers, by Henry H. Symons Bulletin No. 122. Mineral Production of California for 1941, and Direc- tory of Producers, by Henry H. Symons Bulletin No. 123. American Mining Law, with Forms and Precedents, revised to February, 1943 Price $5.00, sales tax $0.13 5.13 Bulletin No. 124. Commercial Minerals of California (Loose-leaf and mimeographed) Price $1.00, sales tax $0.03 1.03 Bulletin No. 125. Manganese in California, with map showing location of manganese properties Price $3.00, sales tax $0.08 3.08 Bulletin No. 126. Mineral Production of California for 1942 and Directory of Producers, by Henry H. Symons Free Bulletin No. 127. Manner of Locating and Holding Mineral Claims in California (with forms) including 1943 statutes (revision of Bulletin 120) Price $0.25, sales tax $0.01 .26 Bulletin No. 128. Mineral Production of California for 1943 and Direc- tory of Producers Price $0.75, sales tax $0.02 .77 Bulletin No. 130. Economic Mineral Resources and Production of Cali- fornia. A Survey with Reference to Postwar Employment Price $2.00, sales tax $0.05 2.05 100 SAN JUAN BAUTISTA QUADRANGLE PRELIMINARY REPORTS Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) ♦*Preliminary Report No. 1. Notes on Damage by Water in California Oil Fields, December, 1913. By R. P. McLaughlin, 4 pp ♦♦Preliminary Report No. 2. Notes on Damage by Water in California Oil Fields, March, 1914. By R. P. McLaughlin, 4 pp Preliminary Report No. 3. Manganese and Chromium, 1917. By E. S. Boalich. 32 pp. Free ♦♦Preliminary Report No. 4. Tungsten, Molybdenum and Vanadium. By E.'S. Boalich and W. O. Castello, 1918. 34 pp. Paper ♦♦Preliminary Report No. 5. Antimony, Graphite, Nickel, Potash, Stron- tium and Tin. By B. S. Boalich and AV. O. Castello, 1918. 44 pp. Paper Preliminary Report No. 6. A Review of Mining in California during 1919. By Fletcher Hamilton, 1920. 43 pp. Paper Free ♦♦Preliminary Report No. 7. The Clay Industry in California. By E. S. Boalich, W. O. Castello, E. Huguenin, C. A. Logan, and W. B. Tucker, 1920. 102 pp. 24 illustrations. Paper ♦♦Preliminary Report No. 8. A Review of Mining in California during 1921. with Notes on the Outlook for 1922. By Fletcher Hamilton, 1922. 68 pp. Paper MINERAL ABSTRACTS (Mimeographed) Antimony, 21 pp. Price $0.25, sales tax $0.01 $0.26 Iron, 52 pp. Price $0.35, sales tax $0.01 .36 Pumice and Volcanic Ash, 50 pp Price $0.35, sales tax $0.01 .36 Sulphur, 23 pp Price $0.25, sales tax $0.01 .26 Tungsten, 33 pp Price $0.25, sales tax $0.01 .26 MISCELLANEOUS PUBLICATIONS ♦♦First Annual Catalogue of the State Museum of California, being the collection made by the State Miiting Bureau during the year ending April 16, 1881. 350 pp ♦♦Catalogue of books, maps, lithographs, photographs, etc., in the library of the State Mining Bureau at San Francisco, May 15, 1884. 19 pp. ♦♦Catalogue of the State Museum of California, Volume II, being the col- lection made by the State Mining Bureau from April 16, 1881, to May 5, 1884. 220 pp ♦♦Catalogue of the State Museum of California, Volume III, being the col- lection made by the State Mining Bureau from May 15, 1884, to March 31, 1887. 195 pp ♦♦Catalogue of the State Museum of California, Volume IV, being the col- lection made by the State Mining Bureau from March 30, 1887, to August 20, 1890. 261 pp ♦♦Lakes of California ♦♦Drift Mining in California (Reprint) ♦♦Catalogue of the Library of the California State Mining Bureau, Sep- tember 1, 1892. 149 pp ♦♦Catalogue of West North American and Many Foreign Shells with Their Geographical Ranges, by J. G. Cooper. Printed for the State Mining Bureau, April, 1894 ♦♦Report of the Board of Trustees for the four years ending September, 1900. 15 pp. Paper ♦♦Bulletin. Reconnaissance of the Colorado Desert Mining District. By Stephen Bowers, 1901. 19 pp. 2 illustrations. Paper Commercial Mineral Notes. A monthly mimeographed sheet (by mail 25(f annually) Free Write for latest revised price list DIVISION OF MINES PUBLICATIONS 101 MAPS Register of Mines with Maps Asterisks (**) indicate the publication is out of print. Price (including postage and sales tax) ♦♦Register ♦♦Register ♦♦Register ♦♦Register ^♦Register ♦♦Register ♦♦Register ♦♦Register ♦♦Register ♦♦Register ♦♦Register ♦♦Register ♦♦Register Register ♦♦Register ♦♦Register ♦♦Register ♦♦Register ♦♦Register Register ♦♦Register of Mines, witli Map, Amador County of Mines, with Map, Butte County of Mines, with Map, Calaveras County of Mines, with Map, El Dorado County of Mines, with Map, Inyo County of Mines, with Map, Kern County of Mines, with Map, Lake County of Mines, with Map, Mariposa County of Mines, with Map, Nevada County of Mines, with Map, Placer County of Mines, with Map, Plumas County of Mines, with Map, San Bernardino County of Mines, with Map, San Diego County of Mines, with Map, Santa Barbara County (1906) Price $0.15, sales tax $0.01 $0.16 of Mines, with Map, Shasta County of Mines, with Map, Sierra County of Mines, with Map, Siskiyou County of Mines, with Map, Trinity County of Mines, with Map, Tuolumne County of Mines, with Map, Yuba County (1905) Price $0.15, sales tax $0.01 .16 of Oil Wells, with Map, Los Angeles City (1906) Other Maps ♦♦Map of California, Showing Mineral Deposits (50x60 in.) ♦♦Map of Forest Reserves in California ♦♦Mineral and Relief Map of California ♦♦Map of El Dorado County, Showing Boundaries, National Forests ♦♦Map of Madera County, Showing Boundaries, National Forests ♦♦Map of Placer County, Showing Boundaries, National Forests ♦♦Map of Sierra County, Showing Boundaries, National Forests ♦♦Map of Siskiyou County, Showing Boundaries, National Forests ♦*Map of Tuolumne County, Showing Boundaries, National Forests ♦♦Map of Mother Lode Region ♦♦Map of Desert Region of Southern California Map vi Minaret District. .Madpra County Price .10 Map of Copper Deposits in California Free **Map of Calaveras County **Map of Plumas County **Map of Trinity County **Map of Tuolumne County ♦♦Geographical Map of Inyo County. Scale 1 inch equals 4 miles ♦♦Map of California accompanying Bulletin No. 89, showing generalized classification of land with regard to oil possibilities. Map only, with- out Bulletin ♦♦Geologic Map of California, 1916. Scale 1 inch equals 12 miles. Shows railroads, highways, post offices and other towns. Geological details lithographed in 23 colors. Mounted ** Unmounted Geologic Map of California, 1938. Scale 8 miles per inch. Lithographed in 80 distinguishing colors and patterns showing geolgic units. In 6 sections, each 32 in. x 42 in. Set of 6 sheets, unmounted. Sheets not sold separately Price $4.00, sales tax $0.10 4.10 ♦♦Topographic Map of Sierra Nevada Gold Belt, showing distribution of auriferous gravels, accompanying Bulletin No. 92. In 4 colors (also sold singly) 102 SAN JUAN BAUTISTA QUADRANGLE Other Maps — Continued Price (including Asterisks (**) indicate the publication is out of print. postage and sales tax) (Map of Ancient Channel System, Calaveras County (Map of Ancient Channels Between San Andreas and Mokelumne Hill Price for set of 2 maps $0.25, sales tax $0.01 $0.26 Commercial Minerals of California, chart of Free Geologic Map of Northern Sierra Nevada, showing Tertiary River Chan- nels and Mother Lode Belt accompanying July-October, 1932, Chap- ter of Report XXVIII of the State Mineralogist. (Sold singly) Price $0.25, sales tax $0.01 .26 ^ Map of Northern California, showing rivers and creeks which produced ^ placer gold in 1932 Price $0.15, sales tax $0.01 .16 Redding and Weaverville Quadrangle Geologic Map and the Northwest- ern Part of the Red Blufl; Quadrangle, showing location of gold mines. (Accompanying January-April, 1933, Chapter of Report XXXIX), ^ sold separately Price $0.15, sales tax $0.01 .16 .„ Mother Lode, Geologic Price .10 Mother Lode Maps showing Geology and Mining Claims in Amador, Cala- vera.s. El Dorado, Mariposa, and Tuolumne Counties, accompanying Bulletin 108, 5 maps, sold separately, each Price $0.15, sales tax $0.01 .16 Geologic Map of Elizabeth Lake Quadrangle, Los Angeles and Kern Counties (accompanying October, 1934, Chapter of Report XXX), sold separately Price .10 Mariposa Co. INIap, accompanying report on Mines and Minei-als of Mari- posa Co. in January, 1935, Chapter of Report XXXI, .sold separately Price $0.15, sales tax $0.01 .16 Map of Western Portion of Siskiyou County Showing Location of Prin- cipal Gold Mines (accompanying July, 1935, Chapter of Report XXXI), sold separately Price $0.15, sales tax $0.01 .16 Perris Block Map (accompanying Oct., 1935, Chapter of Report XXXI). sold separately Price .10 Plumas Co. Map, accompanying Report on Mines and Mineral Resources of Plumas Co. in April, 1937, Chapter of Report XXXIII, sold sep- arately Price $0.15, sales tax $0.01 .16 Los Angeles County Map, accompanying report on mines and mineral resources of Los Angeles County, in July, 1937, Chapter of Report • XXXIII, sold separately Price $0.15, sales tax $0.01 .10 El Dorado Co. Map, accompanying report on Mines and Minerals of El Dorado Co. in July, 1938, Chapter of Report XXXIV, sold separately Price $0.15, sales tax $0.01 .16 Santa Monica Mts., "Western Geologic Map of Price .10 Inyo Co. Map, accompanying report on Mines and Minerals of Inyo Co., in October, 1938, Chapter of Report XXXIV, sold separately Price $0.15, sales tax $0.01 .16 San Diego Co., Map, accompanying Report on Mines and Mineral Resources of San Diego Co. in January, 1939, Chapter of Report XXXV, sold separately Price $0.15, sales tax $0.01 .16 Shasta Co. Map, showing mines, accompanying Report on Mines and Min- eral Resources of Shasta Co. in April, 1939, Chapter of Report XXXV, sold separately Price $0.15, sales tax $0.01 .16 Quicksilver deposits, sold in conjunction with October, 1939, Chapter of Report XXXV Price $0.50, sales tax $0.02 .52 Mono County Map, accompanying report on mines and mineral resources of Mono County in April, 1940, Chapter of Report XXXVI, sold sep- arately Price .10 ■ Kernville Quadrangle Geologic Map, accompanying report on mines and mineral resources of Kern Quadrangle in October, 1940, Chapter of Report XXXVI, sold separately Price .10 Trinity County, Showing Locations of Principal Mineral Deposits (accom- panying January, 1941, Chapter of Report XXXVII) Price $0.15, sales tax $0.01 .16 DIVISION OF MINES PUBLICATIONS 103 Other Maps — Continued Price (including' Asterisks (**) indicate tlie publication is out of print. postage and sales tax) Chromite deposits (showing California geology uncolored) Price $0.60, sales tax $0.02 $0.62 Grass Valley and Nevada City District claim map accompanying report on mines and mineral resources of Nevada Co. in July, 1941, Chapter of Report XXXVII, sold separately Price .10 Nevada City District Claim Map, accompanying report on mines and mineral resources of Nevada County in July. 1941, Chapter of Report XXXVII, sold separately 1 Price .10 Nevada County Map, accompanying report on mines and mineral resources of Nevada County in July, 1941, Chapter of Report XXXVII, sold separately Price $0.15, sales tax $0.01 .16 Oil and Gas Fields (showing California geolog.v uncolored), accompanying Bulletin 118. sold separately Price $1.00, sales tax $0.03 1.03 Index map of Economic Minerals and Geomorphic Provinces Free Imperial Co. IMap, accompanying report on mines and mineral resources of Imperial County in April, 1942, Chapter of Report XXXVIII, sold separately Price .10 Tungsten Properties in California, accompanying .July-October, 1942, Chapter of Report XXXVIII (showing California geology uncolored), sold separately Price .$0.G0, sales tax $0.02 .62 Santa Cruz Co. Map, accompanying report on mines and mineral resources of Santa Cruz County in January, 1943, Chapter of Report XXXIX, sold separately Price $0.15, sales tax $0.01 .16 San Benito Quadrangle Geologic Map, accompanying report on geology of area in April, 1943, Chapter of Report XXXIX, sold separately Price $0.40, sales tax $0.01 .41 San Bernardino County Map, accompanying report on mines and mineral resources of San Bernardino County in October, 1943, Chapter of Report XXXIX, sold separately Price $0.15, sales tax $0.01 .16 Manganese Deposits (showing California geology uncolored), accompany- ing Bulletin 125, sold separately Price $0.60, sales tax $0.02 .62 Jamesburg Quadrangle Geologic Map and Structure Section, accompany- ing report on geology of area in April 1944 Chapter of Report XL, sold separately Price per set $.40, sales tax $0.01 .41 OIL AND GAS FIELD MAPS The following maps are on sale at the State Division of Oil and Gas, Ferry Building, San Francisco, and the various branch offices. The maps are revised as development work advances and ownerships change. Price includes postage and sales tax. No. Price 1— Sargent, Santa Clara County $0.75 2 — Santa Maria, including Cat Canyon — Los Alamos, Santa Barbara County 1.25 3 — Santa Maria, including Casmalia and Lompoc, Santa Barbara County 1.25 4 — Brea Olinda and East Coyote, Los Angeles, Orange Counties 1.25 6 — Salt Lake — Beverly Hills, Los Angeles County 1.25 7 — Sunset, including San Emidio, Kern County 1.25 8 — South Midway, including Buena Vista Hills, Kern County 1.25 9 — North Midway and McKittrick, Kern and San Luis Obispo Counties 1.25 10 — South Belridge and McKittrick-Temblor oil fields, Kern County 1.25 11 — Lost Hills and North Belridge, including Antelope Hills, Kern County 1.25 12 — Devils Den, Kern County 1.00 13 — Kern River and Kern Front fields, including portion of Poso Creek field, Kern County 1.00 14 — Coalinga and East Coalinga Extension, Fresno County 1.50 15— Elk Hills, Kern County 1.25 16— Ventura-Ojai, Ventura County 1.25 17 — Santa Paula-Ojai, including South Mountain, Ventura County 1.25 104 SAN JUAN BAUTISTA QUADRANGLE OIL AND GAS FIELD MAPS— Continued No. Price 18 — Sespe-Piru-Simi, including Bardsdale, Ventura County $1.50 18a — Newhall, Aliso Canyon, Newhall-Potrero, Del Valle and Oak Canyon, Los Angeles County 1.25 19 — Arroyo Grande, San Luis Obispo County 1.00 20 — Long Beach, Los Angeles County 1.75 21B — District 5, boundaries of areas including oil fields, Fresno, Kings and Kern Counties , 1.00 21C — District 4, boundaries of areas including oil fields, Kern, Kings and Tulare Counties 1.25 22 — District 3, boundaries of areas including oil fields, Santa Barbara County .75 23 — District 2, boundaries of areas including oil fields, Ventura County 1.00 24 — District 1, boundaries of areas including oil fields, Los Angeles and Orange Counties 1.00 26 — Huntington Beach, Orange County 1.50 27 — Santa Fe Springs, Los Angeles County 1.25 28 — Torrance, Los Angeles County 1.25 28a — Townlot area, Torrance field, Los Angeles County .75 29 — Dominguez, Los Angeles County 1.00 30 — Rosecrans, Los Angeles County 1.25 31 — Inglewood, Los Angeles County 1.25 32 — Seal Beach, Los Angeles and Orange Counties 1.25 33 — Rincon, Ventura County 1.50 34 — Mt. Poso and Poso Creek, Kern County 1.00 35 — Round Mountain, Kern County 1.00 36 — Kettleman North Dome and Middle Dome, Fresno and Kings Counties 1.50 37 — Montebello, Los Angeles County 1.00 38— Whittier, Los Angeles County 1.25 39 — West Coyote Oil Field, Los Angeles and Orange Counties 1.25 40 — El wood, Goleta (abandoned). La Goleta (gas), Santa Barbara County 1.25 41 — Potrero, Los Angeles County 1.00 42 — Playa del Rey, Los Angeles County 1.50 43 — Capitan, Santa Barbara County 1.00 44 — Mesa, Santa Barbara County 1.50 46 — Richfield, Orange County 1.25 48 — Mountain View and Edison, Kern County 1.25 49 — Fruitvale, Kern County 1.00 50 — Wilmington, Los Angeles County 1.25 51 — Santa Maria Valley, Santa Barbara County 1.00 52 — El Segundo and Lawndale, Los Angeles County 1.50 53 — Rio Bravo and Greeley, Kern County 1.00 54 — Wasco oil field, Buttonwillow and Semitropic (gas), Kern County 1.25 55 — Canal, Canfield Ranch, Coles Levee, Strand, Ten Section, Kern County 1.25 56 — Paloma, Kern County 1.25 57 — Rio Vista (gas), Sacramento, Solano, and Contra Costa Counties 1.00 58 — Trico Gas, Kern, Kings and Tulare Counties 1.00 59 — Raisin City, Helm and Riverdale, including Wheatville area, Fresno County 1.25 INDEX A A. Hoen and Company, Inc., 8 Accessibility of San Juan Bautista quadrangle, 14 Acila muta Clark, from San Juan Bautista formation, 28 Aerial photographs, 13 ; showing Granite Rock Company quarry and plant, pi. 9 ; showing Sargent landslide, pi. 7 Agricultural Adjustment Administration, aerial photos by, 13 Algal growths, from Gabilan limestone, 21 Allen, Eric W.. Jr., 13 Allen, John Eliot, 3, 7, 9, 77 ; cited, 69 Alluvial fans. Quaternary, 11, 45 Alluvium. Recent, 47 American flag raised on Fremont Peak, 15 Ancestral San Andreas fault, 49, 60 Anderson, F. M., cited, 35 Andrews, Philip, cited, 33 Antiqoud mafhovsoiii (Gabb), from Pinecate formation, 28 Antisell. T.. cited. 43 Anzar liuried fault, description of, 50 ; Lake, 23, 38, 44 ; metamorphics, 21 Aptos. black sand deposits near, 74 Arnold, R., cited, 16, 17, 42, 43, 64 Aromas. 15 : red sands in vicinity of, 43 ; faulting in vicinity of, 55 ; Pliocene section north of, 37 Aromas red sands, 11, 18, 21, 23, 30, 37, 38 ; age and origin, 45 ; anticline beneath, 57 ; covering Cement Works fault, 56 ; description of, 43-45 ; fault contact with Plio- cene, 49 ; faulted into granite, 58 ; in terrace deposits, 46 ; lithology of, 44 ; photo showing gullying in. pi. QA ; physiography, 44 ; tilting of, 49 ; type section of, 44 Aromas School, pi. 4J. Artesian wells, explanation of, 47 Artichoke raising, Castroville region, 15 Asphalt seeps, near Sargent, 16, 46 Astrodapsh antiselli, in Santa Margarita formation, 37 Atherton Peak, faulting in vicinity of, 53, 54 Atherton Peak ridge, exposures of Monterey group on, 34, 35, 53 Averill. Charles Y., 77 B Babbs Canyon, 24, 25, 51 Barite, 75 Barnacles, from Purisima formation, 39, 42 Basement, Franciscan, in Santa Cruz Range province, 17 ; granitic, in Gabilan Range province, 17 Beard, C. N.. cited, 17, 64 Becker, G. F., cited, 16, 17 Betabel. 15 : faulting in vicinity of, 54, 55 ; Pliocene section between Sargent Station and, 36 Betabel Station, syncline through, 54 Bethlehem Steel Company limestone quarry, 67 Black sand, in Capitola quadrangle, 74 Blake, W. P.. cited, 33, 43 Bodfish Creek, 23, 24 Bolsa Nueva v Moro Cojo, 15 Bradley, Walter W., 3, 77 ; cited, 75 ; photo by, pi. 12A, pi. 12B Branner, J. C, cited, 16, 61, 64 Brea deposits, on Pescadero Creek, 53 ; Quaternary and Recent, description of, 46 Breen Patrick, land grant given to, 15 Brewer, W. H., 15 ; cited, 15, 73 BrucJarkia gravida (Gabb), from San Juan Bautista formation, 28 Bi'yozoa, in Franciscan sandstone, 26 Butts Ranch — Yallecitos trough, 65, 66 California, geologic map of, S ; topographic quadrangles in. 8 California State Mining Bureau, 16 ; cited, 46, 67 Canada de la Carpenteria, 15 Capitola quadrangle, black sands in, 74 ; Pliocene in, 39 Carlton School, exposures of Aromas red sands near, 43 Carmelo Bay, studies of geology of, 16 Carnadero fault, 22 ; age of movement on, 60 ; boundary of Franciscan belt, 51 description of, 50 Carpenter, E. J., cited, 43, 45 (105) L 106 SAN JUAN BAUTISTA QUADRANGLE Casserly School, exposure of Purisima formation near, 41 ; faulting near, 53 ; syn- clinal structure near, 55 Castro fault, 24, 25, 51, 52 ; age of movement on, 60 Castro Flats, 24, 25, 26, 51, 52 Castroville, 15 Cattle raising-, San Juan Bautista quadrangle, 15, 38 Cement Works fault, description of, 56 Chalochortus albus, as aid in mapping red beds, 14 Chittenden, 15, 38 ; landslides near, 48 ; earthquake, 1921, 50 ; Junction, 22 ; Pass, 77 Cienega del Gabilan, 15 Clark, Bruce L., 13 ; cited, 65 ; identification of Frr.nciscau microi'ossils l>v, 2 vf ■•e KTavels lans (h rty granilir ffra Oand trf»l ll-torlfd. GAB1LAN mus red sa Uow/rlablr iif RANGE t^ Purlalma gioup irniilinnttat omi'lii mid imnils: mnrhte fnnUiferuiig grtn-rt, iuntii». nufKl<>tiit-rates (uTHarted t>a*allic luffx and aoolc'i'Tuifl) NOT IN CONTACT WITH OLDER ROCKS , UNCONFORMITY c e SANTA CRUZ FWl Santa Lucht Kriinlte ibioliie quutU dionle, apiUe dttor. In. ciudetSur «ma vrUA Uie exception oftAe GatriXan limetilonei Oabtlan limestone (dark ffwif to white crutlalline limeMtone) a I Know-ji position a I S 1 Approxlmaie position Alluvial boundaries Known position . ^ I Approximate position Coocealecl by later deposits Axlt3 of anilcllue — -i Axis ol syncliue "X Accurately determined Approximate direction VerUcftl Horizontal X By John Eliot Allen Contour inlei'VMl 2& fbct. '/ ■"^^ I! STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES s^ UNIVERSITY OF CAUFOWBA /^ UBRARY » OOLLECE OF AGRICULTURE r)A\/ia MAP LEGEND 7^/^-2^ J 3 .-; 3 (SD Alluvium itiitn. tntuU, and etav*} Terrace Ki-avels (t) and lane (fl (rtttrtv oranilir oraveU) Qa GABILAN Aromas red sandK {rfd In vHlo-W friablf wfll-nnTtrit . rroM-htdded »andii) Purlslmagroup i^nnlinnitnl gmtflit nvd Miiirf*: mnrhit filUiUi/f'uiiK omirl. luijift*. mid tUt») Monterey shale {dialomacfom and fdlicfou* ulutif uHlti gomf intrrhtddfd limfstonr Imaefi} Monterey sandstone inrkonir nandtl/mfii and oritM) Volcanic Kroup luiid^tile porphvm nnii aaolomtralf. inlrrbrdded mth mmr ortoiriV »and*ton^ (ss) and black tia^aitftoir at hii*rl Vaqiieios group {.reddish colorfd iorrmliallv beddnt caane eunafomrrol'' and hreecia with limridoiu- Imiildirn: roanf JamUiJn Vwrlleiil a. e ^ \ Horizontal X Uuari-i • I'rodiiclnfc well o Dry hole Contuux' interval 2B I'eet. II n ( DIVISrON OF MINES WALTER W BRADLEY STATE MINERALOGIST OLAF P JENKINS CHIEF GEOLOGIST STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES Qls.ol.t.f Qa LEGEND LANDSLIDE.ALLUVIUM, TERRACES, FANS AROMAS RED SANDS Tp !-=5V^| PURISIMA FORMATION >- DIATOMAGEOUS SHALE Qtf JP^^ ■•'.■■ '.a'' ■■::■ \^- y--::X Tmd Tmar — '^ ■ .-■■■. '; — ; ^ Tmd Igggrg- Tmor '■■.■.■.■.■ Tmv TrD Tvar Tolp Tolsj Jfsp Jfls.ch Jfs Jfb Jfog VO CO o A O A O tr LiJ 3 , O < > o A o A ARK03IC SANDSTONE AND CLAY SHALE VOLCANIC GROUP RED BEDS ARKOSIC SANDSTONE JPINECATE FORMATION X X >C X I* fc * ^ ° SAN JUANBAUTISTA FM SERPENTINE ■ LIMESTONE a CHERT SANDSTONE a SHALE BASALT U s / \ qd ^ < o en < AGGLOMERATE SANTA LUCIA QUARTZ DIORITE SUR SERIES AND GABILAN LIMESTONE UNIVERSITY OF CAL UBRi* RV COLLEGE OF A( RIC DAVS STRUCTURE SECTIONS ACROSS SAN JUAN BAUTISTA QUADRANGLE. CALIFORNIA A0COMPANY1NG STATE BULLETIN 153 1946 *'