i'HYSICA \ Sci.LiB, STATE OF CALIFORNIA DEPARTTVIENT OF NATURAL JfUBSOXJRCES awwwwiiMWiMiMWftaiMMMBMBM BBarHW'iwmi i wirKBMiM aM i imnniiMMBBMami iii ntmwinnmwnflfwip iiW GEQLOGfY AJND MINERAL DEPOSITS OF AN AREA NORTH OF SAN FRANCISCO BAY, CALIFORNIA VAaWILLE, AiNTIOCH, MOUNT ^ACk, CAKQUINEZ, jVIARE ISIATsD, 30N0JMA, SANTA ROSA, PETALUMA, AJND POINT REYES QUADRANGLES BULLETIN 149 1949 HHtl DIVISION OF MINES FERRY BOILDING. SAN FRANCJISCO ■HMMHHMnBJHHaBMKfi STATE OF CALIFORNIA EARL WARREN, Governor DEPARTMENT OF NATURAL RESOURCES WARREN T. HANNUM, Director DIVISION OF MINES FERRY RUILDING, SAN FRANCISCO OLAF P. JENKINS, Chief SAN FRANCISCO BULLETIN 149 SEPTEMBER 1949 GEOLOGY AND MINERAL DEPOSITS OF AN AREA NORTH OF SAN FRANCISCO BAY, CALIFORNIA VACAVILLE, ANTIOCH, MOUNT VACA, CARQUINEZ, MARE ISLAND, SONOMA, SANTA ROSA, PETALUMA, AND POINT REYES QUADRANGLES By CHARLES E. WEAVER UNIVERSrrY OF CALIFORNIA UBRARY 'XJLLECE OF AGf ICULTURE Davis LETTER OF TRANSMITTAL To His ExccUcncy The Honorable Earl Warren Governor of the State of California Dear Sir : I have the honor to transmit lierewith Bulletin 149, Geology and Mineral Deposits of an Area North of San Francisco Bay, California, prepared under the direction of the Chief of the Division of Mines, Olaf P. Jenkins. The area covered by this bulletin includes a group of quad- rangles, namely the Vacaville, Antioeh, ]\Iount Vaca, Carquinez, Mare Island, Sonoma, Santa Rosa, Petaluma, and Point Reyes. There is, in addition to the descriptive material on geology and mineral deposits, a series of colored geologic maps which have been printed on the standard topographc quadrangles originally prepared by the U. S. Geological Sur- vey. The following counties are involved in this survey: Contra Costa, Napa, Sonoma, Marin, Solano, and Yolo. The Division of Mines has been publishing a series of reports and geologic maps of quadrangle areas in California, and this bulletin repre- sents one of the series. Bulletin 149 contains a revision and condensation of a longer scientific treatise prepared by Dr. Charles E. Weaver of the University of Washington for publication by the Geological Society of J5/ America as Memoir No. -78. It also contains a chapter on the commercial mineral deposits found in the area, prepared in part by a member of the Division of Mines, William E. Ver Planck, Jr. The results of this investigation are basic and fundamental to the understanding of the state's mineral deposits and related geologic fea- tures. As the district described is in close proximity to the industrial and market areas in the San Francisco Bay region, it is of particular economic importance. The following minerals are described in Bulletin 149 : asbestos, clay, coal, diatomaceous earth, gold and silver, graphite, limestone, magnesite, manganese, mineral water, oil and gas, perlite, pumice, quicksilver, crushed rock, building stone, travertine, and other structural materials. The occurence of ground water is also described, in its relation to the general geologic features. Respectfully submitted. Warren T. Hannum, Director Department of Natural Resources July 11, 1949 §7418 CONTENTS Page ARSTHACT 7 INTKODITCTION 8 Geograpliy 8 I-iocatioii 8 Climat.' 11 VoRt'tation 12 Geologic work 12 Literature 13 DESCRIPTIVE GEOLOGY 14 Sur series 14 Franciscan group 16 Upper Jurassic and Cretaceous 20 General statement 20 Undifferentiated Kuoxville, I'askenta, and Horsetown 21 Chieo formation 26 Tertiary formations 30 General statement 30 Paleocene and Eocene 31 Martinez formation 32 Capay shale 33 Doniengine sandstone 33 Markley sandstone 34 Oligocene rocks 36 San Ramf)n formation 36 Miocene formations 37 Monterey group 37 Laird sandstone 39 Monterey shale 39 Age of Monterey group and Monterey shale in mapped area 40 San Pablo group 40 Briones sandstone 40 Hercules shale member 41 Cierbo sandstone 42 Neroly sandstone 42 Pliocene formations 44 Petaluma formation 44 Relation of Petaluma beds to those of the Orinda formation 46 Orinda formation 46 Merced formation 47 Wolfskin formation 48 Age and correlation 50 Quaternary formations 50 Fre-Pleistocene gravel 50 Pleistocene formations 50 Huichica formation 50 Glen Ellen formation 51 Millerton formation 51 Millerton (V) formation 52 Montezuma formation 52 Recent and Pleistocene 53 Recent 53 Igneous rocks 56 Quartz diorite 56 Igneous rocks associated with the Franciscan group 57 Solano diabase and hornblendite 59 Sulphur Springs Mountain andesite 59 Tolay volcanics 60 (4) CONTENTS— Continued DESCRIPTIVE GEOLOGY— Continued Page Igneous rocks — Continued Pinole tuff 60 Lawlor tuff 61 ^ Sonoma volcanics -- 61 St. Helena rhyolite 08 Putnam Peak basalt 6."> STRUCTURE 66 General statement 66 Faults 66 Folds 72 GEOLOGIC HISTORY 76 ECONOMIC GEOLOGY 84 Asbestos 84 Clav -- 84 Coal 86 Diatomaceous earth 87 Gold and silver 87 Graphite 87 Limestone 88 Maguesite . 89 Manganese 90 Mineral water 91 Oil and gas 92 Perlite deposits 94 Pumice deposits 95 Quicksilver 98 Sulphur Springs Mountain area 98 Oakville area — 101 Area west of Yountville 103 Petaluma area 104 Stone 104 Introduction 104 Operating quarries 104 Geologic distribution 105 Descriptions of indivdual operations 106 Producers of aggregate 106 Producers of creek gravel 110 Producers of "flagstones" and colored building stone 112 Water resources . : 113 Ground water 113 Surface water 114 ACKNOWLEDGMENTS 114 BIBLIOGRAPHY 115 INDEX 123 (5) ILLUSTRATIONS Page Figure 1. Index map of region about San Francisco Bay 9 2. Correlation chart for Miocene formations 15 3. Igneous rocks in Coast Ranges nortli of San Francisco Ray 55 4. Index map showing location of aerial photographs, plates 21-24 64 Plate 1. Geologic map of Santa Rosa quadrangle In pocket 2. Economic map of Santa Rosa quadrangle In pocket 3. Geologic map of Sonoma-Mt. Vaca quadrangles (combined with plate 5) In pocket 4. Economic map of Sonoma-Mt. Vaca quadrangles (combined with plate 6) In pocket 5. Geologic map of Sonoma-Mt. Vaca quadrangles (combined with plate 3) In pocket 6. Economic map of Sonoma-Mt. Vaca quadrangles (combined with plate 4) ^ In pocket 7. Geologic map of Vacaville quadrangle In pocket 8. Economic map of Vacaville quadrangle In pocket 9. Geologic map of Pt. Reyes quadrangle In pocket 10. Economic map of Pt. Reyes quadrangle In pocket 11. Geologic map of Petaluma quadrangle In pocket 12. Economic map of Petaluma quadrangle In pocket 13. Geologic map of Mare Island quadrangle In pocket 14. Economic map of Mare Island quadrangle In pocket 15. Geologic map of Carquiuez quadrangle In pocket 16. Economic map of Carquinez quadrangle In pocket 17. Geologic map of Antioch quadrangle In pocket 18. Economic map of Antioch quadrangle In pocket 19. Geologic sections across area north of San Francisco Bay In pocket 20. Generalized stratigraphic section of the sedimentary rocks in the Coast Ranges of California immediately north of Sau Francisco Bay In pocket 21. Aerial view east from Sonoma-Napa County line toward Napa Valley 64-65 22. Aerial view northwest from a point about 2 miles southwest of Napa 64-65 23. Aerial view north from a point about 5 miles west-northwest of Napa 64-65 24. Aerial view northwest up Carneros Creek from the south boundary of the Sonoma quadrangle, southwest of Napa 64-65 (6) GEOLOGY AND MINERAL DEPOSITS OF AN AREA NORTH OF SAN FRANCISCO BAY, CALIFORNIA* Vacaville, Antioch, Mount Vaca, Carquinez, Mare Island, Sonoma, Santa Rosa, Petaluma, and Point Reyes Quadrangles By Charles E. Weaver ** ABSTRACT The geography, systematic geology, structure, and economic deposits of the Point Keyes, Petaluma, Santa Rosa, Sonoma, ]\Iare Island, Car- quinez, Mt. Vaca, Vacaville, and Antioch quadrangles which involve an area of approximately 2,215 square miles, are discussed in this report. This area includes a section of the Coast Ranges of central California from Sacramento Valley westward to the ocean. The Coast Ranges immediately north of San Francisco Bay occupy three northwestward trending areas, each of which is composed of distinct groups of rock formations, separated by the San Andreas fault and the northern exten- sions of the Hayward fault. Fifty-three cartographic units are mapped. The oldest rocks occur in the Point Reyes peninsula and consist of quartz diorite and residual patches of metamorphie rocks of probable Paleozoic age. They represent a remnant of a once extensive coastal land that lay west of the present coast of California, but which late in the Tertiary or early in the Pleistocene foundered beneath the Pacific Ocean. This land area may haA^e furnished a part of the sediments deposited in the Coast Range area east of the San Andreas fault during the Mesozoic and Tertiary. The next younger rocks consist of sandstones and associated basic igneous rocks of the Franciscan group which are extensively developed between Tomales Ba^^ and the Petaluma-Cotati Valley trough. They probably accumulated during the early half of the late third of Jurassic time. The Coast Ranges between the Petaluma-Cotati trough and the Sac- ramento Valley are composed of more than 30,000 feet of marine and fresh-water sediments ranging in age from Upper Jurassic to Quater- nary, together with 1200 feet of andesite, rhyolite, and associated tuffs of Pliocene age. The lower 17,000 feet of the sequence consist of clay shales and subordinate amounts of sandstone and conglomerates of Upper Jurassic and Cretaceous age. The Paleocene and Eocene rocks are repre- sented by the following cartographic units : Martinez formation, Capay shale, Domengine sandstone and Markley sandstone which are marine and range from 2000 to 5000 feet in thickness. Two hundred to 1000 feet of silty shales and sandstones of Oligocene and middle Miocene age and 2500 feet of upper Miocene sediments were deposited locally in shallow marine basins. The Pliocene rocks, consisting largely of 100 to 1200 feet of alternating flows of andesite, basalt, rhyolite and associated tuffs and agglomerates occupy large areas in the Santa Rosa and Sonoma quad- * Condensation of the paper Geology of the Vacaville, Antioch, Mount Vaca, Car- quines:. Mare Island, Sonoma, Santa Rosa, Petaluma, and Point Reyes Quadrangles, California, Geol. Soc. America Mem., by Charles E. W'eaver. ** Professor of Geology, University of Washington, Seattle, Washington. (7) 8 GEOLOGY OP AN AREA XOU'llI OI'^ SAN FRANCISCO HAY [Bull. 149 rangles. Ni'ar rctalnma. tlicse iiiterfinyer willi iiiiddlc Pliocene marine sediments \\ hicli (tiiitiiuie westAvard towainl the ocean. Durintj;' early Pliocene, the entire mapped area was folded, faulted, and deeply eroded and the middle Pliocene Yolcanie materials Avhich accumulated upon the beveled surface were tliemselves moderately folded and broken by normal faults and several tlirusts near the close of the Tertiary. Durini;' the (Quaternary pci'iod, this area was diffei-entially elevated and depressed ; accompanA'ing' dejiosition, erosion, and stream adjustment produced a complex Quaternarj^ history. Igneous activity was confined largely to the pre-Franciscan intrusion of quartz dioritc; late Jurassic peridotites, gabbros, and basalts associated with the Franciscan group ; and middle and late Pliocene extrusions of andesitic and rhyolitic material. The mineral resources of the mapped area include quicksilver, mag- nesite, limestone, road metal, building stone, natural gas, clays, perlite and pumice, and surface and ground water. Quicksilver mining, although formerly important, is now not very active. Quarries in the andesites formerly furnished paving blocks for the surrounding cities, but are now idle except those which furnished crushed rock. At one time, limestone was mined and used in the manufacture of cement, but because of partial exhaustion and lack of lime content, the lime quarries are inactive at present. The water resources have special importance now because of the increasing settlement of the area and of local irrigation in nearby areas. • INTRODUCTION Geography Location The area under investigation includes nine quadrangles in the Coast Ranges of California immediately north of San Francisco Bay and com- prises parts of Contra Costa, Napa, Sonoma, Marin, Solano, and Yolo Counties. The area of these quadrangles covers approximately 2,215 square miles and lies between 38° and 38° 30' north latitude and 121° 45' and 123° west longitude. It is approximately 35 miles wide from north to south and extends across the Coast Ranges from the Sacramento Valley to the ocean, a distance of 70 miles. Slightly over one fifth of it is occupied by the waters of the San Pablo, Suisun, and Tomales Bays and the margi- nal portion of the Pacific Ocean, leaving a total mapped area of about 1770 square miles. The region lies north and northeast of that covered by the San Francisco folio. The Coast Ranges of northern California occupy an area 300 miles long, extending from San Francisco Bay northward to South Fork Mountain, which extends from the upper part of Sacramento Valley northwestward to the mouth of Klamath River at approximately 41° 30' north latitude, a distance of about 80 miles. This area includes a series of nearly parallel mountain ranges and intervening valleys which trend obliquely to the coast in a direction N. 40° W. The ranges are grouped into the western or Mendocino Range and the eastern, which includes the Miyakma and Vaca Ranges. The two groups are separated by the elongate depression drained by the Russian and Eel Rivers. Each of these groups is subdivided into minor ridges and spurs which are separated by narrow valleys. These 1949] IXTRODUCTIOX Fig. 1. Index map showing quadrangles covered by this report, and tectonic provinces in the San Francisco Bay region. 10 GEOLOGY OF AX AREA NORTH OV SAX FRANCISCO BAY [Bull. 149 rangres extoiul smithward inlo tlie area ui" (lie nine (luadrangles discussed in this report. The soutliern extension of the Miyakma Range forms the (liYide between Napa ami Sonoma \'alleYs and terminates at tlie head of San Pablo Bax'. A snbsidiary of the Miyakma Range, consisting of several ridges. sei)arates J'rom tlie main range in the vicinity of Mount St. Helena and extends south along the eastern side of Napa Valley as far as Car- ((uinez Strait where it merges into the Contra Costa County hills east of San Franeisco P>ay. 'Hie \'aea Mountains, which form the western wall of the southern part of Sacramento Valley, terminate at the head of San Francisco Bay. The Mendocino Range, bordering the Pacific Ocean, eontinues southward through Sonoma and Marin Counties to Golden Cate. Point l\(\ves Peninsula, west of Tomales Bay, in Marin County is topograpliicall\' and geograpliically distinct from the hills of the Mendo- cino Range on the east. The Coast Ranges of the San Francisco Bay area contain longitud- inal depressions which are in part below sea level and form Suisun, San Pablo, and San Francisco Ba^'s. Carquinez Strait and San Francisco B&y are erosional and submerged channels which cut directly through the Coast Ranges and carry the drainage of the Sacramento and San Joaquin Rivers to the Pacific Ocean. There is a notable tendency to parallelism in the ranges, ridges, and intervening valleys wathin the area mapped. Portions of all the above-named topographic units between Sacramento Vallej^ and the ocean are involved in the nine quadrangles under discus- sion and maj^ be referred to as the Sacramento and San Joaquin Valleys including delta plains, flood basins, islands, salt marshes, dissected terraces, San Pablo and Suisun Bays, Vaca Mountains, Vacaville Hills, Potrero Hills. Contra Costa Hills, Los Medanos Hills, Howell Moun- tains. Miyakma Mountains, Sonoma Mountains, Vaca Valley, Sonoma and Kenwood ^'alleys, Petaluma Valley, Cotati Valley, Mendocino Range, and Point Reyes Peninsula. The portions of the Sacramento and San Joaquin Valleys within the area of the quadrangles form a flat and extensive plain with an almost imperceptible slope toward the east and southeast, and occupy large parts of the Vacaville, Antioch, and Carquinez quadrangles. The valley floor is less than 100 feet above sea level and somewhat undulating and the lower depressions during flood time are temporarily covered with river water. The delta plains of the Sacramento Valley occupy a considerable part of the Vacaville quadrangle and extend westward into the terrace deposits between Vacaville and AVinters and southward into the Montezuma Hills of the Antioch quadrangle. They constitute large areas of rich agricul- tural land. The surface of Suisun Valley is less than 100 feet above sea level and is filled wnth alluvium. The extreme southern part gradually merges into the salt-water marshes of Suisun Bay. Flood basins sur- rounded by natural levees 10 to 20 feet higher than the adjacent plain have been built up in the Vacaville and Antioch quadrangles along the banks of the Sacramento River. These become flooded during periods of heavy rains and silt and sand, suitable for crops such as rice, are deposited. The islands formed in the Antioch quadrangle near the junction of the Sacramento and San Joaquin Rivers between wdnding sloughs and sur- rounded by artificial levees, built upon natural levees, have been reclaimed and are now under cultivation. The largest of these is Sherman Island, 194:9] INTRODUCTION 11 situated immediatel}^ east of the junction of the two rivers. Dissected ter- races elevated to 200 feet above sea level along the western border of the Sacramento Valle}' and erosional remnants of the Montezuma Hills in the eastern part of the Antioch quadrangle are composed of rich soil given over largely to grain production. The Vaca Mountains form an area approximately 10 miles long and 6 miles wide, extending southeastward through the j\It. Vaca quadrangle, and disappear beneath the tide marshes of Suisun Bay. Their average altitude is approximately 2000 feet, although at IMt. Vaca it reaches 2870 feet. The Howell Mountains lie betAveeu Napa Valley on the west and Berrj'essa Valley on the east. These mountains are 6 to 8 miles wide and extend northward from Carquinez Strait and Suisun Bay to Mount St. Helena, a distance of about 54 miles. They consist of several nearly parallel ridges separated by intervening valleys together with the sur- rounding outlying hills with no well-defined pattern. The average altitude is approximately 1500 feet. The Miyakma Mountains, well developed on the eastern side of Russian River north of the area mapped, enter the Santa Rosa and Sonoma quadrangles and extend southeastward to the tide marshes at the north end of San Pablo Bay. They are composed of several subsidiary ridges and intervening valleys produced in part by geologic structure and to some extent by the resistance to erosion of the hard layers of lava and tuff. Their general altitude varies from 1000 to 2000 feet. The highest summits are Mt. Hood, 2715 feet high, and Veeder Mountain, 2670 feet. The Sonoma Mountains form a series of irregular and somewhat elongate ridges trending N. 30° W. and extending from the northwestern corner of the Santa Rosa quadrangle southeast for 30 miles to the shores of San Pablo Bay. The general altitude of these hills is from 1000 to 1500 feet. Sonoma Mountain, 2165 feet, is the highest peak. The Mendocino Range, within the area of the quadrangles, lies between Tomales Baj^ on the west and Cotati and Petaluma Valleys on the east. The average altitude of this range is about 1000 feet, with a maximum elevation of 1276 feet in Black Mountain in the southwest part of the Point R«yes quadrangle. Point Reyes Peninsula is a triangular area with its long side parallel to Tomales Bay and the extension of the San Andreas fault depression. The other two sides are bounded by the Pacific Ocean and Drake 's Bay. The principal topographic feature of the area is Inver- ness Ridge which lies close and parallel to Tomales Bay. Climate The climate of the Coast Ranges in the region immediately north of San Francisco Bay is characterized by two seasons, wet and dry respec- tively, the dry season extending from early June to late September, with an average precipitation of less than 0.5 inch. Dense fogs are frequent along the coast and in the regions adjacent to San Pablo and Suisun Bays. Inland, among the hills and valleys, fog is less common, although at times the entire area from the ocean to the Sacramento Valley is blanketed. The mean annual rainfall in the area mapped ranges from 20 to 33 inches and at Mount St. Helena it reaches nearly 60 inches. The minimum and maxi- mum temperatures have ranged from 19° F. in January to 115° in July. Along the coast, the daily range is small. Altitude and topography are the important factors influencing temperatures in the interior valleys. 12 GKOLOOY OK A\ AKKA XOKTIl OK SAN KUAXCISCO BAY |l^ull. 149 Vegetation The several types of floras present in llic ai'(>a doscribed liave been produced lar<4vly by toiiofn-aphic and i-liiuatc indnoncos. Two types pre- vail on the tidal marshes bordoi-inu' Suisnn and San Pablo Ba.vs. The alluvial lands oi" the lower Saci-aniento X'alley are mostly treeless except for occasional oaks and willows. The ^\ ild grasses are represented by the wild oat. Arena fatua. The low area north of San Francisco Bay and rar(|uinez Strait contains bi'j iirovos of the live oak Qncrcus agrifoUa alon instances make U)) lu^ai'ly half the bulk of a single lens. The jjcbbles are composed of white (puirtz, variously colored cherts, quartzites, (juartz porphyries, quartz diorite, schist, cr^-stalline limestone, and sandstone. Some of the conglomerates east of Steel Canyon in the ]\rt. Vaca (juadi-angle contain red cherts Avhich, when examined microsco])ically in thin sections, reyeal the presence of radiolaria. Associated with these are occasional pebbles composed of serpentine and schist, resembling rocks of the Franciscan group. However, the Fran- ciscan rocks have not contributed greatly to the composition of the con- glomerates. The majority of the pebbles are derived from rocks very similar to those occurring in the Sur series. The depositional base of the Shasta series has not been observed in any place within the nine quadrangles. In all places where the Franciscan sandstone is in contact with the Knoxville rocks, the plane of separation is a fault. At many places between Suisun Valley and Steel Canyon, tongues of serpentine, which are so characteristic of the Franciscan, appear surrounded on all sides by shales of the Knoxville formation. However, when the field relations are carefully studied, these serpentines do not seem to have been intruded into the Knoxville, but rather to have been thrust along zones of faulting. The shales at the serpentine contacts show no evidence of metamorphic action. Stratigraphic Sections. The Vaca Mountains are composed of a very thick series of shales and sandstones having a predominantly east- ward dip. They represent rocks of the Shasta and Chico series. The Shasta series extends from a line from Suisun Valle.y northward to Capell Valley, eastward to the crest of the range. The Chico series is confined to the eastern side of the range. Two stratigraphic sections were meas- ured with the aid of transit and plane table. One of these lies between Gordon Valley and the crest of the Vaca Mountains ; the other lies along the highway cut following Putah Creek from the southern end of Berryessa Valley eastward to the crest of the Vaca Mountains. The Gordon Valley section consists of dark-gray, bedded shale 10,000 and 12,000 feet thick overlain unconformably by the massive sandstones and conglomerates of the Chico series. An unknown portion of the Lower Cretaceous is missing in this area because of a fault extending from Gordon Valley to Wragg Canyon. The base of this section is at the dam on the southern end of the Gordon Valley reservoir and probably repre- sents the middle part of Anderson's Paskenta formation of tlie northern Coast Ranges. The thickness is approximately 10,885 feet. 1949] DESCRIPTIVE GEOLOGY 23 Siratigraphic seciion of undifferentiated KitoxvUle, Paskenta, and Horsetown formations from Gordon Valley reservoir eastward to the crest of the Vaca Mountains Thickness (feet) Lithologic character Top of section 100 Basal sandstones and conglomerates of the Chico formation. 2400 Dark-gray banded clay shale containing 15 percent of thinly bedded brownish-gray medium-grained sandstone layers. This may be top of Horsetown. 250 Layers of medium- to coarse-grained brown sandstone with 15 percent of interbedded brownish-gray shale together with lenses of fine pebbly con- glomerate. 165 Interbedded thinly laminated brown medium-gray sandstone and grayish- brown sandy clay shale in about equal proportions and in layers varying in thickness from 1 foot to 2 feet. 350 Chocolate-brown shale containing about 5 percent of thin layers of medium- grained brown sandstone averaging 2 inches in thickness. 450 Well-bedded medium-grained grayish-brown sandstone occurring in layers averaging 2 feet in thickness and interbedded with thinly laminated brownish-gray clay shale whose average thicknes is about 1 foot. 450 Alternating layers of brownish-gray pebbly sandstone and thinly bedded gray shale. 75 Hard medium-grained brownish sandstone layers varying in thickness from 6 inches to 1 foot and interbedded with grayish-brown clay shales. 1800 Brownish-gray shale containing 20 percent of well-bedded medium-grained sandstone and occasional nodules of limestone. 50 Grayish-brown thinly bedded clay shale containing numerous limestone lenses and nodules and about 10 percent of banded brown sandstone occur- ring in layers averaging 2 inches in thickness. 1100 Grayish-brown clay shale conchoidally weathered, containing limestone nodules and occasional thin layers of fine-grained brown sandstone. 75 Medium-grained medium-gray banded sandstone containing 20 percent of layers of soft brownish-gray thinly bedded clay shale, each layer averaging 6 inches in thickness. This assemblage of strata is probably the base of the Horsetown. 350 Brownish-gray clay shale containing 20 percent of interbedded layers of sandstone averaging 1 foot to 2 feet in thickness. This may correspond to the top of Anderson's Paskenta formation. 50 Thin-bedded brown shale containing 10 percent of sandstone layers varying from 2 to 6 inches in thickness. 375 Thin-bedded brown shale containing 20 percent of layers of sandstone of different thicknesses. 25 Massive chocolate-brown clay shale. 800 Grayish-brown clay shale containing interbedded layers of brown sand- stone varying in thickness from 2 to 6 inches. 220 Chocolate-brown clay shale with conchoidal fracture and containing thin layers of coarse-grained brown sandstone ranging from 1 to 3 inches in thickness. 1900 Thick-bedded brownish-gray clay shale containing 10 percent of layers of brown medium-grained sandstone varying from 6 inches to 2 feet in thick- ness. These beds represent the base of the exposed part of the Paskenta beds in the axis of the Gordon Valley anticline at the dam near the lower end of the Gordon Valley reservoir. 10,885 Total exposed thickness of Cretaceous part of the Knoxville, and including Horseto^Ti. 24 GEOLOGY OF AN AREA XORTIT OF SAN FRANCISCO BAY [Bull. 149 The following; section occurs along Piitah Creek canyon from Devil's Gorp:e westward and stratijiraphically downward to a liorizon well down in tlie lowermost part of tlie Cretaceous portion of the Shasta series. This section is a])])roximately 13,230 feet thick. Thickness (feet) Lithologic character Top of section 530 Greatly contorted bedded clay shales resting with an erosional uncon- formity beneath the crossbedded massive sandstones and conglomerates of the basal part of the Chico series at the western end of Devil's Gorge in the canyon of Putah Ci'eek. This may be the top of the Horsetown. 4100 Mainly thickly bedded brownish-gi*ay clay shales which contain layers of medium-grained brownish-gray sandstone ranging from 6 inches to 5 feet in thickness. The prevailing dip is east at angles greater than 45°. Occasional thin layers of light brownish-gray fine-grained dense limestone occur intercalated within the shale and often within these are fossil remains of Aucella terebratuJoides and specimens of ammonites which seem to belong to the genus Phylloceras. These beds cross Putah Creek and are exposed in the steep escarp- ment along the western front of the Yaca Mountains as far south as Suisun Valley. They form the upper third of the western slope of the Vacas and farther south contain progressively thicker strata of sandstone and pebbly conglomerate which contain fossil molluscs. 750 Thick-bedded dark-gray clay shale with numerous layers of thinly lami- nated brown sandstone which become thicker on the southern side of Putah Creek canyon. 500 Mainly thick-bedded brownish-gray shale. 700 Interbedded shale and sandstone in the ratio of 10 to 1. 750 Mainly thick-bedded brownish-gray .shale with occasional thin layers of sandstone averaging 4 inches in thickness. 800 Similar shale with thin layers of limestone. It is possible that the base of this member may be near the contact of the Horsetown and the top of the Paskenta formation. There is insufficient evidence at present to estab- lish the line of separation. 230 Interbedded brown shale and sandstone in the ratio of 90 percent shale to 10 percent sandstone. This may be the base of Horsetown. 800 Interstratified brownish-gray thick-bedded shale making about 92 percent of this member and S percent of thin laminations of medium-grained brownish-gray sandstone in layers usually less than 7 inches. This is pos- sibly the top of Anderson's Paskenta formation. 700 Interbedded shale and sandstone in the ratio of 85 to 15 percent. 1340 Mainly thick-bedded shale with occasional interbedded layers of sandstone averaging inches in thickness. Specimens of Aucella c)-assicolis and fragments of an ammonite which resembles Steueroceras occur in this member. 1949] DESCRIPTIVE GEOLOGY 25 40 Interbedded sandstone and shale in the proportion of 50 percent of each. The individual layers average from 6 to 12 inches. 50 Massive bedded shale. 50 Thin-bedded brownish-gray sandy shale. 200 Interbedded shale and sandstone in layers averaging about 8 inches in thickness and occurring in approximately equal amounts. 400 Shale, largely slumped. 320 Dark-gray poorly bedded shale. 220 Thin-bedded sandy .shale. 250 Sandstone and shale interstratified in the ratio of 60 to 40 percent and occurring in layers varying in thickness from 6 inches to 3 feet. 500 Interbedded dark-gray sandy shale and brownish-gray medium-grained Siindstone in approximately equal amounts. The base of this member occui-s at the junction of the Putah Canyon road leading west to Monticello and the private road which turns south across Putah Creek and up Wragg Canyon. This member may be the basal portion of the Paskenta formation but it is more probable that the contact with the underlying Knoxville shales of the Jurassic is stratigraphically 500 or 1000 feet farther down. 13,230 Base of measured section t Conditions of Deposiiion. The sediments of the Shasta series prob- ably accumulated in a north trending basin which occupied a considerable part of the present Coast Kanges of northern California. These sediments are believed to have been derived from land areas which once existed west and northwest of the present coast, as suggested by Anderson and Reed. Reed postulated the existence of a landmass called Salinia on the west, with a gulf on the eastern side closed at the south and open to the Pacific Ocean farther north. Elevation early in the late Jurassic which accompanied or followed the epoch of intrusive action in eastern Cali- fornia and Nevada brought extensive areas of igneous and metamorphie rocks into the zone of erosion. It is possible that similar rocks, such as the quartz diorite and those of the Sur series, were above sea level west of Tomales Bay in the suggested land area west of the present San Andreas fault zone. The area between Tomales Bay and the Sacramento Valley may have consisted of the rocks of the Franciscan group which, on the west, were only slightly above sea level and, on the east, somewhat below. A persistent .subsidence of the trough during late Jurassic and early Cretaceous would permit a marine environment suitable to the deposition of the thinly laminated siltstones and the occasional sandstones and con- glomerates of the Shasta series. The very slight elevation of the area between Tomales Bay and Petal uma A^alley would have prevented the erosion and removal of any great quantity of Franciscan rock and would at the same time have permitted the transportation of the sediments derived from the igneous and metamorphic rocks from the far western landmass across this area by stream action. The higher elevations may have caused a somewhat arid climate on its eastern slopes thus accounting for the incompletely weathered condition of the plagioclase minerals which characterize the sandstones of both the Upper Jurassic and the Lower Cretaceous formations of the eastern part of the Coast Ranges. If a small thickness of such sediment once covered the Franciscan area west of Petaluma Bay, it since has been removed by erosion. 26 (iKOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 Age (I ml Correlation. Fossils are not abundant in the different sections of the Shasta scries exposed in the area of the nine quadrangles. Accordingly, it is difficult to give tlicir exact stratigraphic positions in the sccjucncc measured by Anderson farllicr nortli in tlie Coast Ranges in Tehama County. Faunas collected from the shales west of Cordon Valley are similar to those listed by Anderson ^^ from the Jurassic beds which he includes in his Knoxville formation. This fauna at Gordon Val- ley includes Aucdia ])iochii, Aucclla sp., AurcUa stantoni, PhiiJloceras knoxville nsis, and BclUinnitcs tehainac)isi.s tSlanton and some poorly pre- served pelecypods and gastropods. This fauna, when compared witli that listed from i\lcCarthy Creek in Tehama County by Anderson seems to correspond most closely with that of the middle faunal division of his Knoxville fornuition. The Aucella show great variation in their outward form, due largely to their adaptation to the i)hysical condition of the sea floor on which they lived. Consequently, the identification of species of .Aucclla may be o])en to some question. The evidence suggests that the Mower faunal division of the undifferentiated Shasta in the area at Gordon i^alley which contains Aucella piochii and Phylloceras knoxvillensis is of T^piier Jurassic age. HoAvever, these beds cannot be separated at present on the basis of lithology from the upper part of the sequence in the Shasta series. Fossils from beds above the Jurassic division in the mapped area are fragmentary^ yet the evidence warrants correlation with the faunal divi- sions recognized by Anderson in the northern Coast Ranges. Fifteen species were collected by the writer from beds in the upper part of the undifferentiated Shasta series exposed on the western slopes of the Vaca Mountains. Although these beds cannot be distinguished for mapping purposes on the basis of lithology from the shales below, yet they probably i-epresent a faunal division of the Shasta series equivalent to Paskenta and Ilorsetown. Chico Formation General ^Statement. All of the deposits of Upper Cretaceous age in the Coast Ranges of northern California, the Mount Diablo region, in southern Oregon and around Vancouver Island were included under the general name Chico group by Gabb. The name was derived from Chico Creek in Tehama County where fossiliferous rocks occur. Exposures of the Chico formation in the nine mapped quadrangles are best on the eastern slopes of the Vaca Mountains from the northern boundar}^ of the Mount Vaca quadrangle southward to the tidal marshes of Suisun Bay. The rocks of this series are also well exposed in an area between Sulphur Springs Mountain and the marshes along the lower course of Napa River ; from here they extend across Carquinez Strait into Contra Costa County east and west of Martinez. Other small areas of lesser importance occur in several parts of the other quadrangles. The Chico formation is composed largely of thinly laminated alter- nating layers of dark brownish-gray clay shale and dark-brown sandstone making up approximately 80 percent of the rocks in the area mapped. Interbedded with these, at intervals from bottom to top, are medum- to coarse-grained massive brownish-gray sandstones and conglomerates 35 Anderson, F. M., Jurassic and Cretaceous divisions in the Knoxville-Shasta suc- cession of California: California Div. Mines Rept. 28, p. 316, 1932. 1949] DESCRIPTIVE GEOLOGY 27 ranpino- in thickness from 5 to more than 100 feet. The alteriiatinj>- thin layers of shale and sandstone range from 2 to 8 inches in thickness and form zones several hundred feet thick. These zones alternate with each other, but when followed laterally along the strike are found to change both in lithology and thickness so that the sequence of members in sections measured several miles apart do not exacth^ correspond. The thick sand- stone beds show great variations in coarseness when followed along the strike. Crossbedding is conspicuous and in some places the sandstone may pass into pebbly sandstones or even conglomerates. The most complete sections of the Chieo series occur on the east flanks of the Yaca Mountains where thicknesses range from 9,000 to 12,000 feet. At the Devil's Gorge, in Putah Creek canyon, the basal member is composed of medium and coarse conglomerate and sandstone which form the crest of the range. It is more than 1,000 feet thick in Putah Canyon, but thins southward along the crest toward Suisun Bay. The upper portion of this member decreases in coarseness and finally passes into alternating sandstones and shales. The conglomerate at the base in Putah Creek canyon bends southward and disappears about 10 miles south of the ereek. The sequence of strata above the basal sandstone mem- bers is characterized bj' alternating thick zones of shale, laminated shale and sandstone, thick-bedded sandstones and conglomerate. Near the top of the sequence, west of the mouth of AVeldon Canyon, there occurs a member about 900 feet thick composed of light-gray to maroon siliceous shale which is overlain by 1400 feet of interbedded argillaceous sand- stone and massive coarse-grained grayish-brown sandstone. This shale member may correspond to the Moreno formation exposed farther south in the Coast Ranges. The sandstone above the shale contains fragments of molluscan fossils with a possible indication of the genus Venericardia. If this poorly preserved fauna could be identified, these sandstones might be found to belong in the Paleocene. However, there is no information at present wdiich warrants such a classification. The thinly laminated silt- stones of the Chico series resemble somewhat those of the Knoxville forma- tion, but in general they are more sanely. The conglomerates consist of pebbles derived from quartz, diorite, many kinds of schist, quartzite, quartz porphyry, slate, sandstone, shale, and chert. The pebbles usually are subangular in shape and range in diameter from the size of a marble to over one foot. The best exposures may be seen in the Devil's Gorge of Putah Canyon in the road cuts. The sandstones are composed prevail- ingly of subangular to moderately rounded grains of quartz and oligo- clase. Very small quantities of rutile, apatite, zircon, and magnetite may also be present. The quartz grains contain many inclusions as observed under the microscope. Two sections have been measured by alidade and plane table across the Yaca Mountains. One of these occurs in Putah Creek valley about one mile north of the Mt. Yaca quadrangle. The strata exposed in this section are representative of the Chico series as far south as Weldon Canyon where the thickness decreases approximately 20 percent. The upper siliceous shale member is present in Putah Creek valley, but is greatly weathered and eroded so that the details of the stratigraphy cannot be measured. The top of the measured section stops about 200 feet strati- graphicalh^ below the siliceous shale. The following stratigraphic section- was measured along Putah Creek on the eastern side of Devil 's Gorge. 28 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 StraVigraphic section of the Chico series measured along Piifah Creek on flic eastern side of the Deril's (lonje. Thickness (feet) Litli(>loi;io oh.u-iicter Top oC flection 100 Hard gray massive sandstone stratiRraphically below the purplish-gray siliceous sli;il(>s wliicli may ropr(>s(Mit the Moreno formation exposed on the wcsttTu sido of tli(> Sau Joaquin Valley. 270 Thin-bedded grayish-brown sandy shale. 70 Hard, gray, massive, medium-grained sandstone. 870 Hard brownish-gray medium-grained banded sandstone with minor inter- calations of shale in thin layers. 90 Hard, gray, massive sandstone containing occasional specimens of Meekia sella. 200 Thin-bedded grayish-brown sandy shale. 75 Light grayish-brown sandstone with laminations of shale. 80 Light -brown massive sandstone. 200 Thin-laminated gray-brown sandy shale. 100 Hard, massive, grayish-brown sandstone containing occasional shale laminations. 90 ^Massive brownish-gray sandstone. 75 liight ])rownish-gray laminated sandstone. 50 Hard, massive, l)rownish-gray medium-grained sandstone containing thin- laminated layers of shale. 60 Thin-laminated brownish-gray sandy shale. 125 Hard, massive, brownish-gray medium-grained sandstone. 40 Weathered light-brown medium-grained sandstone. 60 Interbedded hard sandstone and soft clay shale. 40 Interbedded hard grayish-brown sandstone and softer argillaceous sand- stone. 40 Medium-grained tan-colored sandstone. 50 Hard, massive, brownish-gray medium-grained sandstone. 65 Light brownish-gray weathered sandstone. 60 Hard, massive, brownish-gray sandstone with interbedded shale. 50 Weathered massive brownish-gray sandstone. 50 Alternating layers of thin-bedded shales and brownish-gray sandstone. 250 Thick-bedded brownish-gray argillaceous shale with thin sandstone lamina- tions containing badly broken oyster shells. 200 Thin laminated beds of brownish-gray sandy shale containing specimens of Inoccramus tvhitneyi Gabb. 830 Thin-bedded brownish-gray shale containing layers of grayish-brown medium-grained sandstone averaging 6 inches to 3 feet in thickness. 500 Thick-bedded light-brown shale containing numerous interlaminated thin layers of brownish-gray fine-grained sandstone usually less than 6 inches thick. 100 Massive brownish-gray shale. 305 Massive, hard, gray medium-grained sandstone. 310 Thin-laminated light grayish-brown sandy shale containing thin layers of fine-grained brownish-gray sandstone. 50 Massive brownish-gray medium-grained sandstone. IGOO This member is composed of alternating layers of thin-laminated sandy shale, clay shale, and thin layers of brownish-gray medium-grained sand- stone. The lower third of the member is predominantly argillaceous and the sandy layers become more prominent toward the top. 280 Alternating layers of soft brownish-gray argillaceous sandstone and harder layers of compact medium- to coarse-grained brown sandstone. 100 Massive, hard, brownish-gray medium-grained sandstone. 480 Massive grayish-brown medium-grained sandstone containing thin lamina- tions of clay shale and sandy shale. 210 Interbedded thin-laminated grayish-brown sandy shale and tan-colored medium-grained sandstone in the ratio of 40 to 60 percent. The individual layers are 2 to 5 feet thick. 50 Banded sandstone in layers averaging G feet in thickness with subordinate amounts of light grayish-brown sandy shale. 1949] DESCRIPTR'E GEOLOGY 29 ISO luterbedded layers of shale and sandstone in the ratio of 60 to 40 percent. Individual layers are 2 to 5 feet thick. 440 Hard, massive. lif?ht-bn>wn medium-grained sandstone with occasional interstratified layers of clay shale. 200 Light-brown medium-grained weathered sandstone. 460 Interstratified brownish-gray coarse-grained sandstone and thin-laminated light-brown sandy shale in the ratio of SO to 20 percent. 150 Massive and laminated brownish-gray fine- to medium-grained sandstone. 570 Interbedded medium-grained brownish-gray sandstone and laminated sandy shale, usually in rather thin layers. 990 Massive brownish-gray sandstone with interstratified subordinate amounts of thinly laminated shale. The sandstone layers are often 20 feet thick ; the shale usually less. 1030 Massive, banded, brownish-gray sandstone with occasional interstratified layers of sandy brownish-gray shale. The basal third of this member con- tains thick lenses of conglomerates composed of well-rounded boulders and cobbles of rock derived from quartz porphyry, granite, schist, sandstone, and rock within the Knoxville. These sandstones are pebbly and cross- bedded, and rest unconformably upon the underlying shales of the middle Cretaceous. They are well exposed in the Devil's Gorge in Putah Canyon. This is the base of the Chico group. 12,195 Base of section A second representative section of the Chico series was measured in the southern half of the Vaca ^Mountains immediately south of Gates Canyon from the alluvium of Vaca Valley westward to the basal sand- stone of the Chico series at the summit of the range. Gates Canyon section of the Chico formation. Thickness (feet) Lithology Top of section 1400 Interbedded massive argillaceous sandstone and massive coarse-grained grayish-brown sandstone. 900 Light-gray shale. 2400 Massive grayish-brown medium-grained sandstone occurring in alternating hard and soft layers. 100 Layers of platy brownish-gray sandstone and grayish-blue shale in beds varying from a few inches to 2 feet. 1-500 Massive brownish-gray medium-grained sandstone containing layers of siliceous gray shale varying in thickness from a few inches to a few feet. 850 Bluish-gray soft arenaceous shale containing 15 percent interbedded platj' layers of brown sandstone. 1200 Massive grayish-brown sandstone containing layers of hard siliceous shale averaging 20 feet in thickness. 150 Brown arenaceous shale with thin interbedded layers of brownish-gray platy sandstone. 700 Soft brown massive shaly sandstone. 1.50 Hard, massive, medium-grained brownish-gray sandstone forming the base of the Chico group and resting unconformably upon the shales and sand- stones of the Horsetown beds. 9150 Base of formation 10 GEOLOGY OF AX AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 The Chieo series is well represented in the hills between Sulpluir Sprin«i:s ^Mountain and Suisun Bay in the Carcjninez quadrangle. These hills are tliickly covered by soil. renderin north of Millerton and at Tom's Point near the entrance to Tomales Ba3^ The basal part of the formation as exposed on the north shore of Millerton Head is at least 20 feet of conglomerate composed of well-rounded cobbles, water-worn pebbles of quartzitc, schist, quartz diorite, chert, and rocks of the Franciscan group. Above these are 15 feet of alternating sands and gravels containing Ostrea hirida Carpenter and Venerupis (Protothaca) staminea Gabb. Immediately above these strata is a 2-foot bed of poorly consolidated conglomerate containing a marine invertebrate fauna of 12 species, of which Pecten (Aequipecten) latiauraius Conrad is most abundant. A section ^1 feet thick occurs on the north side of Double Point. Complete and very fossiliferous sections of the formation occur on both the north and south shores of Tom's Point about a mile north of the mouth of Walker Creek near the entrance of Tomales Bay. Sections have been measured at all of these localities. Faunas collected from the Millerton formation at Millerton Head and at Tom's Point show that the same species of invertebrates range from the base to the top of the formation. Thirty-seven species of molluscs have been collected and a Pleistocene flora of 53 species. Both the fauna and flora indicate a climate slightly warmer than that which prevails toda3% possibly representing an inter-glacial epoch. Millerton (?) Formation The type section of the Millerton ( ? ) formation is exposed as nearly" horizontal deposits in raised beaches at several places along the shores of Carquinez Strait and San Pablo Bay. The basal part of the forma- tion is composed of sand containing molluscan shells belonging to species now living in the bay. The beds above are largely sand, clay, and gravel which grade upward into alluvium. The thickness is at least 40 feet and the beds rest unconformably on Paleocene, Miocene, and Pliocene formations. These beds are best exposed at Benicia, Mare Island, and on the shores of San. Pablo Bay between Oleum and Pinole Point. It is impossible to show that the Millerton ( ?) formation was deposited con- temporaneously with the Millerton formation at Tomales Bay; there- fore, the name Millerton ( ? ) formation is used for the purpose of describing these deposits in the southern parts of the Mare Island and Carquinez quadrangles. The formation is of late Pleistocene age. Montezuma Formation The Montezuma formation is named from the Montezuma Hills in the Antioch quadrangle, where it occupies an area of nearly 90 square miles. This area is a remnant of a once more extensive terrace whose aver- age altitude is between 20 and 250 feet. The formation consists of hori- zontally bedded, slightly consolidated, yellowish- and grayish-brown clayey sands, crossbedded pebbly sands, and clays and gravels all more or less lenticular in character. The deposits of the Montezuma formation at the south end of the Montezuma Hills may formerly have connected 1949] DESCRIPTIVE flEOLOGY 53 directly with the grravcls and sands of the same aj^e and litholopric compo- sition occniTin<>' alonp- the northern tlank of Los Medanos Hills in the Antioch qnadranji'le. They probahly were separated by the excavation processes of the combined Sacramento and San Joaqnin Rivers which flow westward throng-h Carqninez Strait. "Remnants of the Monteznma forma- tion occnr on the slopes of the Potrero Hills and alonp- the western marJ1' tlio Point Reyes Peninsula. Sand from dunes bordering the coast has been transported eastward during winter rains, and washed into lagoons or valley bottoms, sorted and roughly stratified. Tliese alluvial deposits are almost entirely derived from the dunes. This formation is continuously being deposited, and since its origin differs from that of the ordinary valley alluvium, it has been mapped separately. Younger Valley Alluvivni. The Recent valley alluvium occupies large areas in the Sacramento Valley as well as in the smaller tributary valleys, and on the borders of San Pablo and Suisun Bays. The material consists of interbedded fine silts, sands, and gravels -which were deposited on the flood plains of the present streams. These deposits rest uncon- formably on all the older formations exposed along the margins of the valleys and grade imperceptibly downward into the older terrace or alluvial sand deposits which border the valleys where they merge into the salt-water marsh deposits. The deposits vary greatly in different localities, depending largelj^ on the mineral composition and matrix of the rock formation in the drainage areas from which they came. Thick deposits of the younger valley alluvium occur in the drowned valleys around the Marin peninsula, such as Walker and Salmon Creeks, which very recently have been slightly elevated. They are composed of a brown sandy loam derived mainly from the sandstones of Franciscan age. Marsh Deposits. The marsh deposits consist of silts and clays which are continuously depositing upon the rock floors of San Pablo and Suisun Bays. They surround the Potrero Hills, Kirby Hills, and numerous other^ small knob-like masses which project through the salt marshes and are still in the process of accumulating. The depth of the deposit varies greatly in different localities up to a maximum of 80 feet near Pittsburg in the Antioch quadrangle. The marshes are gradually passing over into tj'pically alluvial and soil-covered lands, partly as the result of natural processes and partly by reclamation projects. Landslides. Landslide topography has been developed in places in all of the quadrangles, especially where the underlying rocks are composed of softer shales, sands, and volcanic tuffs, and especially on the steeper slopes where springs issue during periods of excessive rain- fall. In places where faulting has permitted the development of many springs, as along the west side of Sulphur Springs Mountain in the Carquinez quadrangle, the altered serpentines of the Franciscan grouj) have slumped onto a considerable area of the Knoxville shale making it difficult to place the contact between the different mappable units. The rapid disintegration of the landslide material often conceals the under- lying formation. Similar landslides are present in the northern part of the Petaluma quadrangle where the clay of the Petaluma formation and the relatively loose sand have moved, obscuring the real contact between the andesite and tuff and the underlying rocks of the Petaluma formation. WA9] DESCRIPTIVK GEOLOGY 55 TABLE OF IGNEOUS ROCKS IN THE COAST RANGES IMMEDIATELY NORTH OF SAN FRANCISCO BAY Pliocene Putnam Peak Basalt Dense black and vesicular basalt. m o S o > S o § St. Helena Rhyolite Member Lava flows, luffs and breccias with lentils of sand- stone and conglomerate. DiATOMACEOUS BeD Light gray fresh water shales containing diatoms in tuffaceous beds. 1 Lava flows, tuffs, agglomerates, and flow breccias, mainly andesitic but locally basaltic; occasional beds of gravel, clay, and sandstone. Lawlor Tuff Pumiceous andesitic tuff confined to Los Medanos Hills. Pinole Tuff Pumiceous tuff of andesitic composition and inter- bedded fresh-water deposits of gravel, sand, and clay exposed in Mare Island quadrangle. ^ w "Tolat" Volc.\nics ~ ® (Not exposed) ^ as u Basalts, andesites, dacites, breccias, and tuffs in well cores from beneath Petaluma formation in Peta- luma quadrangle. Not exposed. Post-Knoxville and Pre-Middle Eocene hornblendite (Solano Diabase) Small masses of igneous rock penetrating shal s of KnoxviUe age in the Carquinez quadrangle and composed predominantly of hornblende and sub- ordinate amounts of augite and plagioclase. Fine- grained and diabasic facies are common. 1- Sulphur Springs Mountain Andesite Fine-grained greatly altered reddish andesite intrusive into and resting upon the Knoxville formation in Carquinez quadrangle. .-.2 Intrusive into Franciscan Series Peridotite, Serpentine AND Silica-Carbonate Rock Intrusive bodies of serpentinized peridotite, with gabbro and pyroxenite, associated with the Fran- ciscan. Silica-carbonate rock derived from the alter- ation of serpentine. 3 = Basalt and Diabase Lava flows with ellipsoidal structures contempora- neous with Franciscan group, and intrusive rocks of similar composition. k CO Pre- Fran- ciscan Quartz Dioritb Point Reyes Peninsula. Fig. 3. Table of igneous rock,- intersecting veinlets of carbonate which are everywhere stained with linionite. These rocks appear as lioneyconibed masses and when extremely altered are composed of crumbly quartz and limonite, which ultimately breaks down to a soil. The hydrous silicate minerals, which constitute the serpentine rock, appear to have been acted upon chemically by heated solutions, presum- ably maginatic, which have produced carbonates i'l-om the maynesium and calcium silicates with the freeing of the silica. This has been redeposited from solution as chalcedony, opal, and quartz. Small crystals of chromite and sometimes the nickle sulphide, millerite, occur within the carbonate minerals, but they are nowhere abundant. Solano Diabase and Hornblendite "'" The Solano diabase has been found in the Carquinez quadrangle in American Canyon on the line between Solano and Napa Counties in sees. 21 and 28, T. 4 N., R. 3 "W. ; other areas occur slightly to the south and in the vicinity of Sulphur Springs IMountain. This diabase in places is sur- rounded by the Knoxville and in other places lies in contact with both the Knoxville and the Eocene sandstone. Numerous small springs issue from along the contact. The rock varies from very fine grained to coarse, the crystals attaining a diameter of half an inch. However, the finer- grained diabasic facies are more widely exposed. The rock is completely crystalline and usually rather fresh. Common hornblende comprises from 60 to 70 percent. Augite occurs intergrown with the hornblende and ranges in amount from 10 to 20 percent. Plagioclase w'ith an average composition of Ab55 to Ab45 is fairly abundant, ranging from 8 to 15 percent. The time of intrusion cannot definitely be determined, but the diabase appears to penetrate rocks of Knoxville age, and boulders and pebbles derived from it occur in the conglomerates in nearby exposures of the Domengine sandstone. ^fc-" Sulphur Springs Mountain Andesite The Sulphur Springs Mountain andesite is confined to the central part of the Carquinez quadrangle, and penetrates the Franciscan ser- pentine and the shales and sandstones of the Knoxville formation in the upper part of Sulphur Springs Valley north of Sulphur Springs Moun- tain. Dikes of the same material have been encountered in the workings of the St. John quicksilver mine in Sulphur Springs Mountain. The rock is fine grained and has a pink to reddish buff color. It consists of pheno- crysts of plagioclase. imbedded in a groundmass of lath-shaped plagio- clase microlites exhibiting a well-marked flow structure. Both pheno- crysts and microlites are altered, rendering it difficult to determine their composition. A few partially altered crystals appear to have a composi- tion of Ab50-An50 and the microlites a composition of Ab40-An60. Greatly altered augite appears imbedded in the groundmass. In addition, there are irregular patches and grains of iron carbonate and a small amount of secondary quartz. The Knoxville shales are slightly altered along the contacts of these volcanics. The andesites may represent intru- sions which have consolidated at relatively shallow depths. This rock, °5 The Solano diabase has coarser hornblendite facies and has been shown as horn- blendite on the accompanying geologic maps ; the name "Solano" is not used on Uiose maps. 60 GEOLOGY OF AN AREA NORTH OP SAN FRANCISCO BAY [Bull. 149 wliich is well exposed in the -workings of the old St. John quicksilver mine, in Sulphur Springs Mountain, assumes a creamy white to light brownish-gray color. It is pi-obable that the alteration of the rock, as well as the deposition of the sulpliides, was produced by heated alkaline solu- tions as an after-effect of these or later intrusions. Tolay Volcanics The Tolay volcanics are not exposed at the surface in any of the mapped quadrangles. They consist of basalts, andesites, dacites, breccias, and tuffs. They were penetrated in a well on Adobe Creek 3 miles north- east of Petaluma, in the Petaluma quadrangle at a depth of 2,223 feet to 5,964 feet. The base was not penetrated in the well. They are overlain by sandstones, clays, and conglomerates of the Petaluma formation and are therefore of pre-Petaluma age. They probably represent a very thick accumulation of volcanic products in a formerly existing valley which lay on the northeast side of the Tolay fault. These volcanic products may have been associated with volcanism dviring San Pablo time. Pinole Tuff The Pinole tuff is exposed at several localities on the south side of San Pablo Bay in the southern part of the Mare Island quadrangle. The exposures along Pinole Valley near the town of Pinole have been dropped by faulting and are not representative of the entire sequence. There are good exposures along the shore of San Pablo Bay between Oleum and Rodeo where the tuffs lie in a synclinal fold and crop out both in the north and south limbs with a thickness of approximately 1000 feet. The true sequence in this anticlinal fold is stratigraphically in place and it could well be considered as the type section of this formation. It rests upon the Neroly sandstone and consists of interbedded tuffs and poorly consoli- dated sands and gravels. The basal part is a coarse, massive rock with very little evidence of bedding. The upper part is somewhat stratified and locally contains thin layers of tuft'aceous clay shales. The tuff is generally light creamy white to brownish yellow and ranges from a very fine, compact, microcrystalline, glassy material to a coarse-grained pumice. Many angular fragments of vesicular lava ranging in size from 5 to 6 millimeters occur in the basal tuffs, and upon microscopic exam- ination show laboradorite feldspar and pseudomorphs of hornblende. The mineral association suggests that the rock is presumably of ande- sitic composition and petrographically similar to some of the Sonoma andesites farther north. The Pinole tuff in the San Pablo syncline is definitely younger than the Neroly sandstone and, on purely local stratigraphic evidence, may have been formed in any interval of time during the Pliocene. It is prob- able that the Pinole tuff accumulated upon a land surface after the withdrawal of the San Pablo seas from the area southeast of San Pablo Bay, and either before or during the time of the outpouring of the Sonoma andesite and interbedded tuffs which are so well represented not far to the north and northwest. Fossil vertebrates examined by R. A. Stirtoii from the tuff in the San Pablo syncline suggest a lower Pliocene age. The tuff exposed near Pinole may be the equivalent of beds stratigraphically higher than any in the sea cliffs along San Pablo Bay. 1949] DESC'lUl'TIVE (iEOLOOV 61 Lawlor Tuff The Lawlor tuff is exposed in Lawlor Ravine in tlie southwest part of the Antioeh quaclranolp whore it forms an outcrop less than 300 feet wide. These tuffs extend alon M an Hi 2§ H .-?> c o HI (0 u £ D ■J". ^ 2i§ Is? o . CO O. 00 «?| (P-M S u w ^ .5^ O C T CO o a; 0) — ^ X 2 2 X 'J — :t ^ *■ _ o -2 — H 1 ^ w — x '•o ^> £53 <- ■Sx rO • ■« "V \, '■'"". ~~ -^ b ^ ^ "" - S) -^ - » < — X -^ 7;> ~ 3 '.^ '- " ^ ^ ^ 7. => _ o ^ H 3 ri ""S s ^ o K < P. 1— P O o (—1 02 t> h- ( P J, 2: < := 1949] DESCRIPTIVE GEOLOGY G5 The prevailing: type of rhyolito is a bliiisli-f^ray coarse-textured porpliyritic rock Avliich shows Avell-defiued banding and flow structure. Other types consist of light-colored, creamy white dense vitreous rock in which the phenocrysts are invisible to the unaided eye. Other varieties are pitchstone and obsidian. The phenocrysts are sodic oligoclase and subordinate amounts of quartz imbedded in a microcrj-stalline aggregate of feldspar and quartz. The ratio of phenocrj^sts to groundmass varies in different specimens, but sanidine is always fairly abundant and occurs in well-developed crystals or in angular fragments with rounded corners. Plagioclase is subordinate to sanidine and occurs in tabular crystals. Its composition places it at the sodic end of the oligoclase group. A micro- crystalline groundmass composed of minute fragments of quartz and feldspar and particles of magnetite is the prevailing type and in some places this alternates in thin layers with microspherulitic bands. The glassy phases exhibit the characteristics of obsidian with perlitic cracks and minute crystallites. I'he flows of pitchstone at the base of the rhyo- litic sequence are pale brown, but contain phenocrysts of sanidine and quartz ; all show marked corrosion effects. The St. Helena rhyolite rests upon the Sonoma volcanics, w^hich may be middle Pliocene, and in places passes beneath deposits of Pleistocene age. The St. Helena rhj-olite may be late Pliocene in age. Putnam Peak Basalt The Putnam Peak basalt is named from Putnam Peak in the north- east part of the Mt. Vaea quadrangle, where it covers an area of slightly more than 1 square mile. It is also exposed in small patches east of Vaca and Pleasants Valley's and north of Vacaville where it rests unconform- ably upon the Markley and San Pablo formations and dips at a low angle to the east. It is possible that at an earlier time these residual patches were connected. The Putnam Peak basalt may be intricateh' connected with the Wolfskin formation which contains layers of tuff. It ranges in thickness from 5 to 300 feet. No tuffaceous beds were observed inter- fingered with it. Petrographically, it is a dark, iron-black, dense, compact lava with a splintery to subconchoidal fracture. Vesicular types are exposed near the top of the flow at the eastern end of Putnam Peak. The lava is composed of phenocrysts of plagioclase, augite. and olivine imbedded in a microerystalline groundmass consisting of very small lath- shaped microlites of laboradorite and grains of augite, and subordinate amounts of granular and crystalline magnetite. These crystals are in a glassy groundmass. The olivine crystals are deeply corroded and rounded on the margins and traversed by numerous irregular fractures along which the mineral is extensively altered to serpentine. The Putnam Peak basalt is younger than the San Pablo and is pre-Pleistocene. It probably represents outpourings of lava more or less contemporaneous with others of Pliocene age in the area mapped, and may correspond to the tuffs in the lower part of the Wolfskill formation which is probably middle Pliocene. 6—7173 66 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [BuU. 149 STRUCTURE General Statement The principal structural features in the nine quadrangles include three orographic blocks : the Montara block ; the San Francisco-Marin block; the Berkeley Hills block; and the Vaca Mountain block. Each of these blocks is tilted slightly toward the northeast. The first three were described originally by Lawson ^^ in the San Francisco folio. The Mon- tara block is represented in the Point Reyes quadrangle on the western side of Tomales Bay by the Point Reyes Peninsula as well as an area of unknown extent whose surface at present is beneath sea level. The San Francisco-Marin block lies between Tomales Bay and the extension of Santa Rosa and Petaluma Valleys. The Berkeley Hills block, if continued northward, would extend into the Miyakma, Sonoma, and Howell Moun- tains. The Vaca Mountain block lies between the Berkeley Hills block and the Sacramento Valley and includes the Vaca Mountains and the Vaca- ville Hills. The structural chart accompanying this report contains numerous cross sections through all of the quadrangles and shows the relation of faults and folds to the geology. The rocks of the Franciscan group were deformed and locally meta- morphosed by igneous intrusions prior to the deposition of the Knoxville strata. Overlaps and small unconformities between the different forma- tions belonging to the Cretaceous and Tertiary systems are the result of minor disturbances associated with elevations and subsidences. Com- pressional movements resulting in folding, faulting, and thrusting were important very late in the Miocene or early in the Pliocene. A second extensive deformation occurred near the close of the Pliocene and con- tinued early in the Pleistocene. Recurrent disturbances, related to these ^ later movements, have taken place at intervals throughout the Quarter- nary and down to the present day. Faults San Andreas Fault Zone. The San Andreas fault, which lies in the northwest-trending rift valley between Bolinas and Point Reyes Sta- tion and Tomales Bay, is the most important structural feature in the entire area under discussion. The course of this fault trends from the mouth of Tomales Bay northwestward parallel to the coast and inter- sects the coast line east of Bodega Head northwest of the Point Reyes quadrangle. It continues southeastward a short distance west of Golden Gate and enters the San Francisco Peninsula at Mussel Rock and thence continues southeastward through the southern Coast Ranges for several hundred miles. The rock formations in the Montara block on the west side of the San Andreas fault are entirely different from those in the San Francisco-Marin block on the east side. The rocks in the Point Reyes Peninsula consist of quartz diorite and residual patches of crystalline limestone and quartzite overlain by marine sediments of Monterey shale. These rocks lie in fault contact with the sandstones and associated igneous rocks of the Franciscan group on the east side. Thin layers of marine sandstone of the Merced formation and occasional residuals of the Sonoma volcanics are the only younger rocks resting on the Fran- ks Lawson, Andrew C, op. cit., pp. 2, 3, 1914. 1949] STRUCTURE 67 ciscan and their areal distribution is small. Tlie Franciscan rocks have been strongly folded and the axes trend diagonally to and abut against the eastern border of the San Andreas fault zone. Originally, the Fran- ciscan rocks may have extended over the surface of at least a part of the Montara block including the Point Reyes Peninsula, although the relative geographic positions of the rocks on the east and west sides of Tomales Bay were probably different than today, due to differential lateral as well as vertical movements along the San Andreas fault plane. The char- acter of the sediments of the Franciscan group near the fault zone east of Tomales Bay is not suggestive of shoreline deposition. No rocks of the Franciscan group have been observed on the western side of the fault. Quartz diorite is entirely absent in the area between Tomales Bay and the Sacramento Valley. If the rocks of the Franciscan group were deposited on the quartz diorite on the western side of the fault, the earliest movements along the San Andreas fault were post-Franciscan and pre-Miocene. The occurrence of quartz diorite, as well as Monterey shale, along Inverness Ridge at altitudes of more than 1400 feet above sea level, and the presence of Franciscan rocks at corresponding altitudes east of Tomales Bay is evidence for post-Miocene movements along the fault and the elevation of the ]\Iontara block. During a part of the Monterey epoch, the sea may have extended across the face of the fault zone and covered a part of the Franciscan area in the San Francisco-Marin block as is evidenced by the lack of shoreline deposits in the Monterey shale near the San Andreas fault. The rocks of the Franciscan group east of the San Andreas fault are locally covered with relatively thin formations of Pliocene age, indicating that the San Francisco-Marin block was again depressed below sea level, allowing the deposition of the Merced forma- tion, but with no intervening formation of Miocene age. Later, probably at the close of the Tertiary, the San Francisco-Marin block was elevated so as to bring the Merced beds to altitudes of more than 500 feet. The numerous activities along the San Andreas fault have continued down to the present day, the last noteworthy movement being associated w^ith the earthquake of 1906, w-hen the Point Reyes block was moved north- westward and the San Francisco-Marin block was displaced south- eastward. Faults of the San Francisco-Marin Block. Faults in the sandstones of the Franciscan group are usually difficult to trace because of the massive character of the rock. Burdell Mountain has been dropped along the Burdell Mountain fault at least 400 feet, and the southeastern exten- sion of this fault can be traced to the tidal flats on the west side of Peta- luma. It is again exposed in the hills northwest of Grand View where it separates a narrow area of lavas and tuffs on the southwest from serpen- tine and the overlying Novato conglomerate on the northeast. The Tolay fault, which may represent the northwest continuation from beneath the waters of San Pablo Bay of the Hayward fault east of San Francisco Bay, enters from the shore of San Pablo Bay about 1 mile south of the mouth of Sonoma Creek and continues northeastward to the valley of Tolay Creek until it finally passes beneath the alluvium of Petaluma Valley east of Petaluma. The sharply folded sandstones, shales, and conglomerates of the Petaluma formation, exposed in Tolay Valley, abut against the rocks of the Franciscan group along the Tolay fault and are 68 OKOT.OGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 downthro-\vn on the northeast side, an nnknown distance which may amount to several thousand feet. The knobs and tuffs of the Sonoma volcanics rest on the bcA^eled surface of the Petahima formation and, Avhere they have not been removed by erosion, they stand up against the Tolay fault by which they are cut. This fault may be observed half a mile northeast of the Lakeville School and residuals of the Sonoma volcanics still rest in patches on the Franciscan rocks on the southwest side of the fault. Near the fault, the Petaluma strata dip steeply, probably as a result of drag. A prominent, steep, rounded hill, 2 miles northwest of Fairville, on tlie eastern side of a re-entrant of the Petaluma beds Is composed of andesites m\d tuffs which are strongly folded and dip 57° SW into the Petaluma formation. These disturbed rocks may be asso- ciated with the drag along the Tolay fault. The Tolay-Hayward fault separates the San Francisco-Marin block from the Berkeley Hills block and may have come into existence early in the Tertiary. Faults East of the San Francisco-Marin Block. The Rogers Creek fault occupies a zone of normal faulting several hundred feet wide that trends approximately N. 40° W. The amount of vertical displacement is probably less than 200 feet and the downward movement is on the northeast side. The fault is confined entirely to the lavas and tuffs of the Sonoma volcanics and its trend may be in part identified by peculiarities of topography such as fault sags and shallow sag ponds. Many of the smaller gullies which formerly crossed this fault zone appear to have been disturbed where they intersect the zone and the small amounts of drainage carried through them have been diverted to the valley of Rogers Creek along the fault. The Carneros fault, Avhich trends slightly west of north in the Sonoma quadrangle, forms a prominent escarpment along Carneros Creek where marine sediments of the Oligocene and Miocene, as well as the overlying Pliocene lavas and tuffs, have been dropped down on the west against the shale of the Knoxville on the east. Near the head of Carneros Creek, many small transverse faults on the western side of the main fault have progressively lowered the sandstone of the San Pablo and the volcanics in a step-like manner until finally the andesites and tuffs are in contact along the Carneros fault with the shales of the Knoxville. Northwest of Calabazas Creek this contact continues beneath the lavas and cannot be distinguished at any place in the area mapped. It may extend beneath the plane of the St. John Mountain thrust fault. Field relations of the volcanics to the Knoxville formation suggest that the Carneros fault was active prior to the beginning of Pliocene volcanic activity. It may have originated at the close of the Miocene or during the early Pliocene. The attitude of the fault plane in Carneros Creek is nearly vertical and the amount of vertical displacement along the fault is possibly 1500 feet. The Sulphur Springs Valley thrust fault lies along the eastern slope of Sulphur Springs Mountain in the Carquinez quadrangle and sepa- rates the Franciscan and later intrusive rocks on the west from the shales of the Knoxville on the east. Sulphur Springs Mountain and its northern extension toward Napa Junction represent a large sliver block which has been brought up along the main fault. An intricate network of small faults intersects this block and small masses of Ejioxville shale 1949] STRUCTT'RE 69 are wedged in with the serpentine, but are not intruded by it. Knoxville masses are, lu)\vcvei\ iiiti-iuh-il by the Sulpliur Spriiit!S Mountain andes- ite Avliieli also cuts the serpentine. S(»utheast of Sul])hur Si)rinjrs Moun- tain the shales and sandstones of the Chico formation are in contact aU)n"- this fault with the shales and sandstones of the Knoxville. A tunnel of the Hastings quicksilver mine in sec. 11, T. 3 N., R. 8 W., has been driven west through fossiliferous shales of the Knoxville to the fault contact with the brecciated shale, and a raise has been extended to the surface along the contact. The plane of the thrust fault dips 54° E. in the mine. On the north side of American Canyon, serpentine is badly shattered and small wedges have been forced into the Knoxville ; the northern extension of the main mass of the serpentine has been thrust for at least half a mile onto the Domengiue sandstone. The Sulphur Springs Valley fault may represent the southeasterly continuation of the Carneros fault. A trace of the St. John ^Mountain thrust fault extends in a general westward direction through the northwest corner of the Sonoma quad- rangle. The sandstones and associated igneous rocks of the Franciscan group have been thrust in a general southward direction onto the folded rocks of the Knoxville. The fault continues in a northwesterly direction across the northeastern part of the Santa Rosa quadrangle. It may be followed from the edge of Napa Valley west of Rutherford into the head- waters of Santa Rosa Creek in the Sonoma quadrangle. The trace of the fault may be observed on the edge of Xapa Valley west of Rutherford where the Knoxville formation rises from the floor of the valley and contacts the rocks of the Franciscan group about 300 feet higher up. A crosscut tunnel has been driven westward from the slope of the hills to the fault and many stopes have been made along this plane affording an opportunity for studying its general character. Farther west, the contact between the Franciscan sandstones above and the Knoxville shales below may be observed in road cuts leading to La Jolla mine. Here, the dip of the plane is approximately 60°. As the result of erosion, small isolated patches of the Franciscan rest on the Knoxville shale a short distance from the main trace of the fault. West of the valley of Sonoma Creek, the fault is lost beneath the lavas and tuffs of the Sonoma volcanics, but it probably continues westward as a buried structure, to the valley north of Santa Rosa. A large area of Franciscan sandstone and intrusive serpentine occurs in the northwest corner of the Mt. Vaca quadrangle where it rests on the strongly folded Knoxville along a thrust plane dipping toward the north. The trace of the fault, which may repre- sent the continuation of the St. John Mountain thrust fault, extends in a westerly direction south of Capell Valley to Atlas Peak and passes beneath a thick cover of the Sonoma volcanics which occupies an area westward to Napa Valley. The eastern end of the Franciscan area is in fault contact with the shales of the Knoxville on the west side of Steel Canyon along a plane with an undetermined dip to the west. South of the fault trace occur isolated patches of the Fraliciscan sandstone, many of them too small to map, surrounded by Knoxville beds. Several small local normal faults occur in the region of Conn Valley east of St. Helena, probably associated with the major St. John Mountain thrust fault. It is believed that this thrust fault occurred before the outpouring of the andesite and rhyolite as the volcanics lie upon all the contacts and have not been cut bv the same faults although they are 70 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAT [Bull. 149 involved in strong folding. It is possible that all these tectonic move- ments may have been associated near the close of the early Pliocene, and that they were followed by extensive erosion until a relatively level plain was developed upon which the thick accumulations of Pliocene vol- canics piled up. The Conn Valley fault, which trends N. 45° W. for approximately 1^ miles and then turns westward at the mouth of Conn Creek Canyon, is concealed beneath the alluvium of Napa Valley. The Sonoma volcanics series exposed in the east limb of the Conn Creek anti- cline is in fault contact with the serpentine and has been dropped on the west side of the fault. At an earlier time, the lava covered the serpentine. The amount of displacement becomes less toward the south and the fault finally dies out a short distance southeast of the place where the Sonoma volcanics normally rest on the serpentine. The Soda Creek fault east of Napa, with a vertical displacement of over 700 feet, and the downthrow toward the west, separates two promi- nent peaks at the head of Soda Creek Canyon. This fault extends south- ward along Soda Creek and is concealed beneath the terrace deposits at the mouths of Milliken and Sarco Creeks. The Browns Valley and Mill Valley faults occur in the Sonoma quadrangle in the hills west and northwest of Napa. The Browns Valley fault separates the Knoxville on the west from the Domengine on the east and the amount of vertical displacement is probably more than 2000 feet. In the lower valley of the south branch of Mill Creek, the wedge- shaped rocks of the Knoxville lie between Domengine sandstone and Pliocene lavas and tuffs. The contact of the shale with the Domengine is a fault, whereas that with the lavas and tuffs shows normal flow relations. Numerous other smaller and less well defined faults occur in the incom- petent shales of the Knoxville between Browns Valley and Dry Creek Valley. The Wragg Canyon high-angle thrust fault which lies on the west side of the Vaca Mountains extends from Gordon Valley northward through Wragg Canyon to Putah Creek. This fault develops in the axial portion of the southward-plunging Gordon Valley anticline in which are involved a thick sequence of Knoxville sediments. The western limb of this fold is completely folded and crushed, and north of Gordon Valley is in part overridden by the rocks in the eastern limb along the Wragg Canyon fault, which becomes progressively more pronounced toward the north. It extends along the northern course of Gordon Valley and thus through Wragg Canyon where the fault plane may be seen in sec. 2, E,. 3 W., T. 7 N. The axes of the minor folds in the Knoxville on the west side of the fault are somewhat diagonal to it. The Wooden Valley fault extends from the northern end of Wooden Valley in the Mt. Vaca quadrangle southeastward along the western side of Suisun Valley and thence is concealed beneath the alluvial floor of Suisun Bay. The evidence for its existence is based on the occurrence of numerous patches of serpentine of the Franciscan group intercalated in the shales of the Knoxville as sliver wedges. These patches are in align- ment and show no evidence of intrusive effect upon the shale, but instead there is crushing and slickensiding in the shale adjacent to the serpen- tine. The incompetent character of the shales and considerable land- sliding makes it difficult to place on the map a definite line for the extension of the fault. 1949] STRUCTURE 71 Green Valley owes its orir()l)ably eontiiuied for an unknown distance to the north. The Oli^orene invertebrate faunas have some Asiatic affinities and suggest sub-tropical climatic conditions and possibilities for migra- tions sontlnvard ah)nlied the Pacific Portland Cement Compjuiy's ]ilant at Cement. Tlie ])ure crystalline limestone deposit Avhich occurs in granodiorite west of Tomales"Bay has not been exploited. The deposit at Cement is on land owned by E. N. Tooby, about 5 miles northeast of Fairfield. Many years ago "Suisun marble" was quar- ried here, and prior to 1900 the material was used for flux at the Selby smelter."'^ From 1902 until about 1910 it was the principal source of limestone for the cement plant. W. L. Watts ''^ describes the deposit as resembling a stockwork, for the surrounding rock is a breccia of sand- stone and shale cemented by lime and traversed in all directions by vein- lets and irregular bunches of the so-called marble. Much of this has the luster of resin, and some is delicately banded. Most of the lime was taken from what was known as the main quarry which covers about 9 acres in the NE^ NWi sec. 8, T. 5 N. R. 1 W. A second quarry covering about 80 | acres was opened later in the E^ sec. 8. The shale used in cement manu- | facture occurs interstratified with Cretaceous beds and was quarried about a mile from the mill site. Until 1927 the plant continued to operate, using an increasingly larger proportion of limestone brought by rail from El Dorado County. Analyses of the clay and limestone have been fur- nished by T. S. Montgomery, former superintendent of the plant. Typical Typical analysis analysis of of clay travertine Silica 58.65 Silica 1.25 Alumina 18.25 Alumina and iron 1.00 Iron oxide 7.35 Lime oxide 54.00 Lime oxide 2.15 Magnesia 0.55 Magnesia 1.15 Loss on ignition 4;i.00 Alkali 2.05 Sulphuric anhydride 0.50 99.80 Loss on ignition 10.00 100.10 The limestone deposit southeast of Napa Junction from 1903 to 1908 furnished material to a plant owned by the Standard Portland Cement Company. The limestone is interbedded with Knoxville shales and ranges from argillaceous varieties to pure limestone. The deposit is described "''^ as containing regular beds of limestone from 1 foot to 4 feet thick, striking N. 70° E. and dipping 65° NW., which are overlain by a yellow calcareous clay. About 100 feet of limestone and 50 feet of the clay were exposed in the pit from which both materials were obtained. It is stated that the clay became more calcareous toward the east and merged into limestone. This company also failed after an attempt was made to supplement the local limestone with material brought from near Santa Cruz. The follow- ™ Logan, C. A., Limestone in California : California Jour. Mines and Geology, vol. 43 p 3.32 1947 '■^ Watts, W. L., Solano County: California Min. Bur. Rept. 10, p. 670, 1890. '-Auburv, L. E., The structural and industrial materials of California: California Div. Mines Bull. 38, pp. ISl, 182, 1906. 1949] ECONOMIC GEOLOGY 89 ing analyses -were made by the Standard Portland Cement Company's laboratories. llif,'h-f;r:ule Low-grade material material SiOa 6.63 20.2.", AI2O3 3.61 8.68 FezOa — 1.26 3.11 CaCOa 85.17 65.23 MgCOa 1.83 1.72 SO3 0.91 0.25 The Tomales Bay deposit has been deseribed by Eekel.''^ Coarsely crystalline limestone of possible Paleozoic age outcrops about half a mile west of Point Reyes Station and extends north about a mile to a point west of Trout Farm. The deposit is about half a mile wide and covers an area of 300 to 400 acres. It is cut off on the east and north by granodiorite and overlapped by Miocene shale on the southwest. The rock lias been quarried for lime burning at several points, but Eckel thinks this work was done before 1900. Eckel gives the following analyses.'^'* No. SiO^ AloOs Fe^Oa CaCOs CaO MgCOa MaO COz 1. 1.66 0.44 0.20 96.60 n. d. 0.75 n. d. n. d. 2. 2.26 0.55 0.2o 95.48 n. d. 1.10 n. d. n. d. 3. 2.3 0.76 incl. 96.0 53.8 n. d. 0.35 42.7 4. 1.3 0.3 iucl. 97.0 54.32 u. d. 1.25 42.68 No. 1 from near Trout Farm by C. A. Newhall ; No. 2 from Lockhart tract near Inverness Park by C. A. Newhall ; No. 3 from Lockhart tract near Inverness Park by U. S. Bureau of Standards; No. 4 from near Inverness Park by F. Huber. Magnesite Limited amounts of magnesite, a little of which has been mined, have been noted in three localities within the quadrangles here discussed. Magnesite has been found a short distance west of Capell Creek and about a quarter of a mile from its junction with Soda Creek Canyon ; in the hills west of Rutherford ; and 1^ miles east of Napa Junction. It occurs in the Franciscan formation as veins or irregular masses in serpentine or its alteration product, silica-carbonate rock. The magnesium has probably been derived from serpentine by the action of circulating water heavily charged with carbon dioxide and has been precipitated in fracture zones of the serpentine. The silica which has also been taken into solution has been partly precipitated as quartz and partly carried away. The North (Cleveland) mine is near Capell Creek in the NE-^ sec. 35, T. 8 N., R. 4 W., on the north side of Greasy Bank Creek. The magnesite forms small .segregations and intersecting veins within a large mass of serpentine. The property has been opened on a small scale by several open cuts and pits. About a quarter of a mile southeast of the North mine is a vein of pure magnesite 5^ feet wide, striking northwestward and dipping 30'^ NE. This vein has been developed by open cuts and a short tunnel. Both ■'3 Eckel, E. C, Limestone deposit.s of the San Francisco region : California Div. Mines and Mining Rept. 29, p. 353, 1933. "* Logan, C. A., Limestone in California : California Jour. Mines and Geology, vol. 43, p. 252, 1947. yU GEOLOCiY OF AN AREA NOIM'll oi'' SAN FRANCISCO HAY [lUlll. 14!) l)roperties are idle, but during World War I ore was hauled 16 miles to Ivutlicrford where it was loaded onto cars. The iiiagnesite Avest of Kutherford occurs as small |)atchos associated with serpentine. They have never been of commercial importance. East of Napa Junction li miles there are small segregations of magnesite in silica-carbonate rock. During World War I several were completely extracted, leaving pits 3 or 4 feet deep and approximately 5 feet in diameter. No magnesite deposits are known in the serpentine of the Franciscan rocks betAveen Tomales Bay and Petaluma Valley. Manganese Small deposits of manganese oxides of the type characteristic of the Coast Ranges are associated with chert in areas of Franciscan rocks. The nature and origin of this type of deposit have been discussed by Talia- ferro and Iludson."^^ During World War I several deposits in the area covered by this report were prospected and found to be uneconomical ; although reinvestigated during World War II, only one property actually produced. The quantity of good ore found has been so small that mining has thus far been confined to periods of unusual demand and high prices. The Knutte mine, which is about a mile south of Novato, belongs to Messrs. Connell and Brazil and was leased to Mr. L. R. Knutte. Man- ganese was obtained from two open cuts during 1942 to 1945. Manganese oxide occurs in a small lens of chert near its contact with Franciscan sandstone. The chert strikes N. 65° W. and dips 45° NE. There is some manganese along the base of the chert, but most of the ore is near the top contact. Approximately 6 feet of sooty black oxide grades into siliceous material and then to mere black films staining the chert. The manganese is associated with thin-bedded chert and shale and not wnth a massive variety, a bed of which is in the sandstone close by. Two other similar but smaller deposits developed by M. Vonson during World War I were unproductive. One is on R. Mazza's property about 3| miles south of Petaluma; the other is on the Moredo property 6 miles west of Petaluma. The Hoist- Weeks prospect which is on land now belonging to R. B. Weeks has been described by Davis and Hudson.^*^ ''The (Hoist- Weeks) prospect is located — about 10 miles by road northeast from Santa Rosa. ' ' The prospect lies about 150 yards south of the summit of a promi- nent east-west ridge. A small open cut exposes a five- to seven-foot thick mass of metamorphosed chert. ' ' The chert is for the most part of a lustrous bright yellow variety. This alters to an earthy limonitic material. Within the chert there are irregular masses made up of resinous, brown to red and dull buff material evidently the result of metamorphism of a mixture of manganiferous opal and siliceous carbonate. Greenstone was observed in place, about ten yards to the east. The intrusion of this greenstone was doubtless respon- sible for the metamorphism. " Taliaferro, N. L., and Hudson, F. S., Genesis of the mang:anese deposits of the Coast Rang-es of California: California Div. Mines Bull. 125, pp. 217-275, 1943. ™ Davis, E. F., and Hudson, F. S., The Weeks prospect, in Manganese deposits of California, pp. 393-394. An unpublished report written March 2, 1918. 3949] ECONOMIC GEOLOGY 91 ''Altoration to black oxides of man^aiiosc lias takon jilaco along joints within the inanjiaiiese-bcariii^' material and black sliells liave formed locally on the periphery of the chert mass. "Down the hill slope to the west of the prospect, the soil carries nnmerous an<;nlar fragments of inanay, and the Honker Bay area on the north shore of Honker Bay. Gas and oil have been encountered in lower Pliocene sands in the Petaluma area. The thick deposits of sandstone of the Franciscan group in [Nlarin and Sonoma Counties are not known to contain petroleum. The Knoxville, Paskenta, and Horsetown beds on the western side of the Vaca Mountains are folded into anticlines, but are not known to contain oil in this area. Neither have evidences of petroleum been reported from the folded micaceous sandstones of the ^Markley formation which are well exposed in the northern part of the Carquinez quadrangle. The Rochester Oil Company well is in sec. 24, T. 5 N., R. 1 W. at the southern end of a low rock ridge where indications of oil had been reported.®^ Gas and salt water were encountered together in a stratum of sand at a depth of 1520 feet, and although the well was drilled to 1820 feet nothing more was obtained. The gas, reported to have flowed at the i-ate of 20,000 cubic feet per day, was used in Suisun, Fairfield, and Cement. Crude salt was recovered from the brine by solar evaporation. Four more wells were later drilled in the same region but were not com- pleted, and no gas was struck. The well is on the east limb of a south- plunging sharply folded anticline, the surface formation of which is Domengine sandstone. The source of the gas may be in the underlying sandstones and shales of the ^Martinez formation or in the jMoreno shale. The Potrero Hills gas field has been described by F. B. Tolman.^- The Richfield Oil Corporation's Potrero 1, which is situated in the eastern part of the Potrero Hills anticline, was drilled to 5334 feet in 1938. Gas was encountered in 30 feet of Cretaceous sands between 326.5 feet and 3235 feet. An earlier well drilled to 3047 feet found gas showings, prin- cipally at 2100 feet. The lowest formation penetrated was the Panoche shale, the upper part of which contains the gas sands. Overlying this is 1000 ± feet of Martinez sandstone, and this in turn is overlain by the lower ]Meganos, Capay, and Domengine shales totalling 2075 ±: feet. The upper formation is the Markley sandstone, 1400 zh feet thick. The Potrero Hills anticline coincides in general with the topography of Potrero Hills. It trends eastward, and is eastward-plunging and asym- metrical. The structure is complicated by several faults, one of which runs along the south flank at the west end. Farther east a northwest- curving fault pattern cuts across the structure. The Petaluma district ^^ is about 5 miles east of Petaluma. During the summer of 1948 the Trico Gas and Oil Company completed an oil well and a gas well and began another in the same locality. The first shallow wells, one of which produced a little gas from a depth of 800 feet,^^ were drilled here about 1910. Deeper wells were drilled by the Shell Oil Company and others from 1927 to 1935. The Shell Oil Com- pany's Murphy 1 was 6385 feet deep. Trico Oil and Gas Company's « California State Mining- Bureau, Solano County : California Min. Bur. Kept. 14, p. 310, 1915. s^Tolman, F. B., Potrero Hills gas field: California Div. Mines Bull. 118, pp. 595- 59S, 1943. ^ Morse, R. R., and Bailev, T. L., Geological observations in the Petaluma district, California : Geol. Soc. America Bull., vol. 46, pp. 1437-1456, 19.'?5. Johnson, F. A., Petaluma resjion : California Div. Mines Bull. 118. pp. 622-627, 1943. « California State Mining Bureau, Sonoma County : California Min. Bur. Kept 14. p. 342, 1915. 94 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 Petaluma Community 5 No. 2 produces a small amount of oil from an oil sand interbedded Avith bentonitic claystone between 950 and 970 feet. Total depth of the liole is 975 feet. The oldest rocks encountered are the Tolay volcanics, probably of earh^ Pliocene age. Tliis formation is more than 4000 feet thick ; the base is not exposed nor was it penetrated by the deepest test well. The portion penetrated was from top to bottom ])yroclastic, andesitic, and basaltic. The Petaluma beds which are 4000 feet thick have been divided into a lower 500 to 600 feet of dark clay shales and an upper section of clays, sands, and jaravels. The basal beds are interbedded with the upper mem- bers of the Tolay volcanics. The Sonoma volcanics overlie the upper Petaluma beds with pronounced angular unconformity along the south edge of Sonoma Mountain north of the wells. The gas- and oil-producing area lies immediately north of a wedge of Franciscan which has been elevated between two steeply dipping reverse faults, the Tolay fault and the Lakeville fault. The axes of the folds in the Petaluma beds are faulted, disconnected, and difficult to trace, but it is clear that northeast of the Franciscan wedge an open syncline is followed by an anticline, the axis of which is offset by several cross- faults. A small domed area, now complexly faulted, evidently was formed in the vicinity of the Murphy, Ducker, and Trico wells. Gas was discovered on the north shore of Honker Bay in 1944 when the Standard Oil Company of California completed Honker Community well 1-A which is in sec. 25, T. 3 N., R. 1 W. Gas in Eocene or Paleocene sands was encountered between depths of 7190 and 7220 feet. Only one well has been successfully completed in this area. In the same year the Suisun Bay gas field was discovered on the north shore of Suisun Bay. The first producing well was Standard Oil Company of California Suisun Community 3 located in sec. 5, T. 3 N., R. 1 W. ; at the end of 1947 there were but two producing wells. Gas is found in an Eocene sand locally called the "Suisan sand" from 3410 to 3640 feet, and in the Domengine sand from 3820 to 3909 feet. The Kirby Hill gas field was discovered with the completion of Shell Oil Company, Incorporated well Lambie 1-A in sec. 25, T. 4 N., R. 1 W. Production is from sauds below the top of the Domengine at about 2055 feet. At the end of 1947 there were nine potential gas wells. Commercial delivery of gas from the Suisun Bay and Kirby Hill fields began in 1947. ■'to"^ Perlite Deposits* The search for lightweight materials to be used in aggregates led to the discovery of several deposits of perlite in Napa and Sonoma Counties. Although there has been no production of perlite from any of the deposits located in the area covered by this report, an appreciable production is being made from a deposit in the N^ sec. 34, T. 8 N., R. 5 W., MD. Here the National Perlite Company is currently mining perlite and shipping it to their expanding plant at Campbell where the perlite is converted into a plaster aggregate. In general, the perlite occurs in the form of flows of variable thickness associated with rhyolites, dacites, basalts, tulfs, and agglomerates of the Sonoma volcanics. * Prepared by C. W. Chesterman April 6, 1948. 1949] ECONOMIC GEOLOGY 95 Tliin lenticular bodies of perlite occur in tlie tufTs on the A. W. Frazier property about 4 miles east of State Iligliway 12. Here the perlite is overlain in part by riebeckite rhyolite. Relatively larpre deposits of perlite occur on the J. J. Coney Ranch 3 miles northwest of Kenwood and State Iligbway 12, in flows of variable thickness and leufrth. These deposits are overlain by basalt, and underlain by rhyolite from wiiich building and flagstones are currently being (juarried at the Gordenecker flagstone quarry. Another large deposit of perlite occurs on the C. M. K. Quinlan property in sec. 7, T. 6 N., R. 7 W., MD., about 4 miles east of U. S. Highway 101. The perlite here resembles remarkably that found east of St. Helena and tests performed upon it indicate that it would be suit- able for plaster aggregate. The perlite occurs as flows of variable thick- ness associated with rhyolite, basalt, and tuffs of the Sonoma volcanics. Pumice Deposits Pumice lapilli have been mined from certain tuff beds of the Tertiary volcanics. Tuffs comprise much of the Sonoma volcanics which occupy a large area covering parts of the Mt. Vaca, Sonoma, Santa Rosa, Petaluma, and ]\Iare Island quadrangles. Tuff also is interbedded vrith Tertiary sedi- ments south of Suisun Bay. Not all the tuffs, however, contain pumice. The most important pumice-producing area is east of Napa along Sarco Creek and the north slope of Mount George where the Basalt Rock Com- pany, Cicero, Pearl, Walker, and 'Wilson pits are located. Some pumice has been obtained from the Diablo Pumibloc and Alvernaz pits southwest of Pittsburg. The Frazier pit is in the ]\Iivakma IMountains east of Glen Ellen. Production began on a small scale about 1932 and has increased markedly within the last year or two. It is used almost entirely as aggre- gate for lightweight building blocks which are becoming increasingly popular. The blocks produced are used throughout the bay area. Frazier. A. W. Frazier 's deposit is on Trinity Road about 4 miles from State Highway 12. A little pumice was produced in 1933, but the property has been idle since that time. DiaUo Pumihioc Company. The Diablo Pumibloc Company has, since 1945, leased a deposit belonging to j\Ir. Bailey, east of Bailey Road and 1^ miles south of U. S. Highway 40. The pit now worked is about 500 yards east of the Bailey house, but pumice is also exposed in a small pit close to the house. At the main pit a 10-foot bed of tuff containing sand grains and pumice fragments up to half an inch in diameter lies between beds of sandstone which strike N. 70°W. and dip 25°NE. The overlying sandstone is coarse and friable ; at the bottom the tuff and pumice grade into sandstone. A 50-foot water well near the house is stated by Bailey to have been sunk entirely in pumice. At the surface near this well the tuff and pumice contain small lenses of cross-bedded coarse sand. The main pit is on a dip slope. About 3 feet of friable sandstone overburden is removed by bulldozing, and the underlying pumice is moved to a stock pile at the foot of the slope. From here it is carried by _a dragline scraper to a screen and hammer mill where the oversize is reduced. The material is then stored in three steel tanks. The output is used in the company's lightweight building-block plant on U. S. High- way 40 near Bailey Road. 96 GEOLOGY OF AN AREA NORTH OP SAN FRANCISCO BAY [Bull. 149 Alvernaz. A deposit similar to that of the Diablo Pumice Company lies 11 miles uoi-tlnvesi alonti' the same tufl' bed and 1 mile south of the east end of Willow Tass. It is on property owned by ]\1. Alvernaz. In 1945 Messrs. Furman, Gieji', and Vierra leased the property. The next j^ear control passed into the hands of Pittsbur^' Pumice Industries who have, however, jn-odueed no ])umiee recently. In j>'eue]-al the tleposit is sinnlar to the neighboring one to the east. Here, also, the tuff outcropping ranges from material that is almost entirely tuff with scattered half-inch pebbles and bits of pumice to a loosely consolidated mass of pea-sized pumice fragments. An irregular body of coarse friable sandstone exposed in the pit crosscuts the tuff* and the enclosing sandstone. The pit has been opened along the strike of the beds which strike N. 55°W. here and dip into the hill at an angle of 25° NE. The remnants of a small grinding plant are also on the property. Basalt Rock Company. The Basalt Rock Company of Napa has been producing pumice since 1934. Current production is from the Mount George deposit 4| miles northeast of Napa on State Highway 37. The original pit, which w^as abandoned in 1946, lies just northwest of the pit from which rock is currentl.y obtained. Davis ^-^ describes the old pumice pit as follows : ' ' This deposit consists primarily of fragments of pumice imbedded in a matrix of volcanic tuff". Lapilli of other volcanic material such as scoria and obsidian, and bombs of basalt, are also present. ' ' The quarry face is semi-circular in shape and reaches a height of 75 feet at the center of the deposit. The face is about 600 feet long * * *." Since 1946 the Basalt Rock Company has produced pumice from the Mount George deposit. This is a massive deposit of pumiceous breccia containing fragments of light-gray pumice which average less than an inch in diameter though some have diameters of several inches. There are also bits of lava and an occasional bomb several feet in diameter. This volcanic material is set in a matrix of orange clay, which makes up less than 5 percent of the total volume. After the overburden and brush have been removed, bulldozers traveling across the deposit accumulate a load of pumice which is delivered to a loading bin at the lower edge of the deposit. Occasionally a rooter or a sheep foot roller must be used to pre- pare the ground for scraping. All material is passed through a grizzly of 3-inch pipe with 9-inch openings before being loaded on trucks for the 8-mile haul to the washing and block plant. ^^ Cicero Pit. The Cicero pit, owned by Frederica A. Pearl and leased to C. Cicero, is 4^ miles northeast of Napa on State Highway 37. Accord- ing to Davis,^'^ ' ' The deposit is a pumiceous tuff near the surface and grades down- ward into a massive pumice containing some volcanic fragments. The surface layers dip about 20° SW. and show the following changes: 85 Davis, F. F., Mines and mineral resources of Napa County, California : California Jour. Mines and Geology, vol. 44, pp. 172, 173, 1948. ^ Davis, F. F., Mines and mineral resources of Napa County, California: Cali- fornia Jour. Mines and Geology, vol. 44, p. 173, 1948. 8' Davis, F. F., Mines and mineral resources of Napa County, California : California Jour. Mines and Geology, vol. 44, p. 174, 1948. 1949] ECONOMIC GEOLOGY 97 Section near center of pumice pit Description I']stimated tliickness Chocolate brown surface soil, mud, fra^^uients 1-2 feet Fragmental pink puuiice with brown clay coatings 18 inches Fragniental pink pumice in gray pumicite matrix 4 inches Fragmental pink pumice, brown clay coatings 3 feet Gray pumice with obsidian pebbles 4 feet Fragmental pink pumice, brown clay coatings S inches Massive gray pumice, some ash and obsidian pebbles 20 f»*et "It is reported that the floor of this quarry was drilled, showing massive gray pumice to a depth of 80 feet. * * * " Pumice was produced from 1937 to 1940 and from 1946 to the present. Lightweight building blocks and acoustical plasters are made in a plant near the deposit. Pearl. The Pearl pumice pit is owned by Frederica A. Pearl and has been operated intermittently, including a continuous period from 1933 to 1936. It is 4| miles northeast of Napa and a quarter of a mile north of State Highway 37. The pit is separated from the Cicero deposit bj" a ridge. Beneath a maximum of 2 feet of soil, a yellowish tuff con- taining fragments of gray pumice grades downw^ard to massive pumice at the level of the pit floor. The operator of this property sold crude or screened pumice. Silva. The Silva pumice pit, owned by William Silva and leased to 0. Wright and A. Wilder, is on State Highway 37, 6f miles northeast of Napa. In 1946 about 400 tons of massive clean gray pumice containing some fragments of ash and obsidian were mined. Walker. The Walker deposit, on State Highway 37 about 6 miles northeast of Napa, is a pumiceous tuff containing lapilli of ash, basalt, and obisdian. Davis ^^ reports that in 1946 Messrs. Rice, Bergum, and Pankost leased it from the owner, D. C. Walker, and began clearing and leveling the surface with a caterpillar thirty diesel scraper equipped ^vith special wear-resisting teeth. A jaw crusher and screen on the property reduces the pumice to minus 1 inch in size. Wilson. T. D. Wilson's deposit on State Highway 37, 5^ miles northeast of Napa, has been leased to Lava-Lite Products Company. Although called "black pumice" the material actually is black scoria, probably representing the surface of a flow. Davis^^ reports : ' ' Operations began * * * early in 1946 on a side-hill exposure over an area of about two acres. * * * Lateral variations from black scoria to black volcanic mud containing fragments of scoria up to 3 inches in diameter can be seen. Fragments of ropy vesicular lava are also pres- ent. The scoria is exposed over a vertical distance of about 35 feet. It is overlain by a bed of light-colored volcanic tuft' containing a few gray pumice fragments averaging about an eighth of an inch in diameter. This tuff is about 30 feet thick and is itself overlain by tuff' containing pumice fragments half an inch in size. This latter tuff is seen at the north edge of the quarry near the property line. "A bulldozer delivers the * * * crude scoria to a wooden hopper. Oversize is sledged by hand. The hopper feeds the conveyor belt of a 88 Davis, F. F., Mines and mineral resources of Napa County, California : California Jour. Mines and Geology, vol. 44, pp. 175, 176, 1948. .-,,., • ^ ,-, 8» Davis, F. F., Mines and mineral resources ot Napa County, California : Calirornia Jour. Mines and Geoloev, voL 44, p. 176, 1948. 8—7173 98 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [BuU. 149 portable Owa one-piece screeniuj^r plant. * * *" containino; a 1-inch vibrating? screen, a 10-x 36-incli Cedar Rapids jaw crusher, and rolls. "Tlie end product is sold as an aggregate for manufacturing lightweight building blocks * * *." Quicksilver Quicksilver has been produced in quantity from two widely sepa- rated areas in the quadrangles covered by this report. Tliese are the Sulphur Springs Mouiitain area with three mines and the Oakville area with two. In addition, development was done many years ago west of Yountville and, dui-ing World War II, in Marin County southwest of Petaluma. The ore bodies commonly occur as stockworks within areas of complex faulting and are composed of irregular masses of brecciated rock cemented witli cinnabar and gangue. The deposits are characteristically associated with silica-carbonate rock, an alteration product of serpentine, and, in the Sulphur Springs Mountain area, with the Knoxville sand- stone and shale which are in contact with silica-carbonate rock. The history of these operations, except for the Marin County pros- pect, closely reflects that of the California quicksilver industry as a whole. The period of greatest production was from 1874 to 1878 w^hen the mining of low-grade and comparatively large deposits was made practical by new treating methods. A period of lower prices followed, and after 1880 all the mines operated intermittently. All of the principal mines were active during World Wars I and II, but none were operating in 1948. Sulphur Springs Mountain Area Sulphur Springs Mountain is a horst-like fault block composed prin- cipally of serpentine and silica-carbonate rock and extensively intruded by andesite which has been highly altered. The block trends N. 20°W. and is in fault contact on the northwest and southeast with shales and sandstones of the Knoxville group. These sediments, which are appar- entl}'- later than the serpentine, also occur within the block as slivers bounded by faults of relatively small displacement. An older series of fault zones which intersect the folded shales, the silica-carbonate rock, and the andesite dikes has resulted in shear planes and breccia zones, some of which served as channels for the mineralizing solutions. The Knoxville shale, wherever it is in contact with silica-carbonate rock, is silicified and brecciated. Ore is found in fault zones between silica-carbonate rock and the Knoxville shales, as disseminations or pockets among minor fractures within the silica-carbonate rock, as disseminations in Knoxville sand- stone or altered andesite near fissures, and replacing the carbonates of shattered andesite bodies. The ore bodies are bounded, often on the hanging wall, by clay seams or gouge known as ' ' atlas. ' ' The mines in the Sulphur Springs Mountain area are the St. John (Vallejo) mine at the north end, the Brownlie near the crest of the moun- tain about 2^ miles southeast of the St. John mine, and the Hastings mine on the east slope below the Brownlie. St. John Mive. The St. John mine has been the largest quicksilver producer in the quadrangles under discussion. It lies in sec. 33, T. 4 N., R. 3 W. on land owned by Clifford K. Dennis. Here the mountain divides northward to form two spurs, Mount St. John on the east and Mount 1949] ECONOMIC GEOLOGY 99 Luffman on the west. These have respective elevations of 1110 and 1060 feet. There are tliree groups of workings. Tlie principal workings lie in a small basin-like depression between Mount St. John and Moinit Luffman. Mining was done also on the north side of Mount St. John about half a mile away and on Mount Luffman. Mount Luffman and the ridge extending north from it are composed of reddish silica-carbonate rock which outcrops in ragged crags. A nearly vertical fault separates this mass on tlie east from soft folded Knoxville shales. These shales lie beneath the basin and outcrop along the slopes of the ridge which culminates to the north in Mount St. John. The crest of this ridge is an intercalated layer of hard Knoxville sandstone. The first discoveries of ore were made in 1852 and the first mining work was begun in 1855 on the north side of Mount St. John. Until 1873 all development work was confined to the north side of the mountain in the NE^ sec. 33, T. 4 N., R. 3 "W. These workings have long been abandoned and are now inaccessible. In 1873 mining operations were transfered about half a mile south to the basin in the SE-| sec. 33. The St. John mine, after producing 11,530 flasks of quicksilver, was forced to close in 1880 by low quicksilver prices. Probably it was during this first production period that the pits, trenches, shallow shafts, and short tunnels were made on Mount Luffman. Production was renewed in the periods 1899 to 1908 or 1909 and 1914 to 1918. Li 1916 ore averaging 0.5 percent quicksilver was reported mined at the rate of 1000 tons per month. Operations since World War I have been sporadic, and since a fire destroyed the plant in 1923 there has been no furnace on the property. Some quicksilver was recovered from the dumps about 1936, and development work was done during World War II. Total production probably is between 18,000 and 20,000 flasks. The principal workings consist of a tunnel driven from slightly above the furnace level almost due north for 1100 feet. A shaft sunk 400 feet from the tunnel level connects tliree main and five intermediate levels. There were, in addition, other shorter tunnels and shafts. The ore bodies mined varied both in shape and size. One of the largest was from 300 to 400 feet long, 25 to 30 feet wide, and 12 or 15 feet thick. At present almost all the tunnels and shafts are caved, but during 1903 to 1916 most of the workings were accessible to Charles E. Weaver. The following description of the ore bodies is based on observations made at that time. The principal workings lie within the Knoxville shales and intrusive andesites which lie in fault contact with the silica-carbonate rock of IMount Luffman. Intrusive masses and dikes of andesite in the different levels of the mine have a general northwest strike with a southwest dip. Both the dikes and the shales which they intrude are intersected by faults whose prevailing strike is N. 35 °E. and dip 55° to 65° NW. The dike rocks occurring between these shear zones are shattered and intersected by numerous systems of minor fractures. In many places the Knoxville shales have been silicified along the contact with the intrusive andesite, and later brecciated by faulting. The quicksilver ores occur within these fault zones as irregular bodies of varying size and shape. The andesites have been thoroughly altered, and the original minerals have been widely replaced by quartz or dolomite. In portions of the altered rock near the fissures there are impregnations of marcasite and cinnabar which replace the carbonates of the dike rock. Such ore bodies are intensely altered dikes containing disseminated particles and veinlets of cinnabar. 100 GEOLOGY OP AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 Operations north of Mount St. John. The old mine workings on the north side of Mount St. John occur in a zone of brecciated silicified shale of the Knoxville formation whicli in depth is cut by intrusive andesite. Immediately east of tliis liard sliale a sjindstone member of the Knoxville stands nearly vertically. The ore occurs in minute veiiilets in the sand- stone as well as in the breccia, and the location of the pockets seems to be controlled bv intersecting fracture zones which were connected with the main fissures along wliieh the mineralizing solutions rose. The cinuabar on ]\Iount Lufi'man occurs in minute intersecting vein- lets in the silica and also in small pockets of irregular shape formed at the intersections of small shear zones within which are intricately intersecting fractures filled with minute quartz veinlets. It is reported that the early miners obtained rich specimens here. In addition to cinnabar, the ore contains little but a small amount of marcasite. Two varieties of mineral bitumens are associated with it, both on IMount Luffman and Mount St. John. One, a dark brown to black, soft, resinous wax which forms a coating on the drusy faces of quartz-lined cavities, resembles posepnyte. This is supposed to be a mixture of ozocerite and a substance having the formula C22H3CO4 which is soluble in ether. The other, presumably napalite (C3H.1), is yellow to reddish brown in color, has the consistency of shoemaker 's wax, and forms very thin coat- ings along fracture planes adjacent to shear zones. It is probable that alkaline sulfide solutions as an after effect of the andesite intrusion rose along the breccia zones beside and within the dikes and precipitated the ore minerals there. The common association of cin- nabar with opal, chalcedony, calcite, and dolomite suggests that these solutions were of magmatic origin. Possibly the ores were deposited at intervals from the early Pliocene to the present, although many of the bodies are cut by prominent faults of probable late Pliocene age which show no effects of mineralization. Extensive areas of sharply folded Knox- ville shale which are intersected by andesite dikes both north and east of Sulphur Springs Mountain contain no ore. Hastings Mine. The Hastings mine is 2| miles southeast of the St. John mine in sec. 11, T. 3 N., R. 3 W. A small amount of land around the mine belongs to the Hastings estate. Production has been small. The Hastings mine was discovered during the seventies and was operated on a small scale by a series of shallow cuts and trenches. Although develop- ment was done in 1904 and 1905, no further production was made until 1917. The mine w^as closed the following May. In 1929 a new crosscut tunnel was driven into Sulphur Springs Mountain in a southwesterly direction. Such large quantities of water were encountered that in 1930 the mine was closed and sealed. Besides the shallow workings of the early days there are at least two tunnels. The main tunnel of 1917 intersected the ore at 950 feet from the portal and had a total length of 1,100 feet. One of the largest stopes measured 30x15x10 feet, while another was 40x20x10 feet. There were smaller stopes also. In this part of the mountain a fault zone, which at the mine strikes N. 30° W. and dips 54° NE., divides Knoxville shales on the east from a zone of silicified and brecciated shale on the west. Bradley ^^ mentions »o Bradley, W. W., Quicksilver resources of California : California Min. Bur. Bull, 78, p. 172,1918. 1949] ECONOMIC GEOLOOY 101 an altered igneous mass immediately west of the breccia zone. The ore bodies are irregular masses of cinnabar which occur in fractures within the breccia zone. BrownJie Mine. The Brownlie mine has produced a small amount of quicksilver but is now idle. It is on land owned by J. Ilayden Perkins, half a mile due west of the Hastings mine in sec. 10, T. 3 N., R. 3 W. Here also the earliest workings, consisting of sliort tunnels and shallow cuts, were made in the seventies. Except for development by E. C. Beck about 1945 nothing more has been done here. The ore appears to have been similar to that of the Hastings. Oakville Area The mines in the Oakville area are the Bella Oak, 1^ miles northwest of Oakville, and La Joya, 3^ miles west of Oakville. La Joy a mine seems to include what in the seventies was known as tlie Summit or "Whitton mine. The Bella Oak mine is credited Avith 1,792 flasks of quicksilver, while the yield of the La Joya was 2,017 flasks. Both mines have been described by Fix and Swinney,^^ and the following description has been abstracted from their report. Mesozoic sedimentarj' rocks of the Franciscan and Knoxville groups make up most of the Oakville district, but the higher divides are capped by Sonoma volcauies. The principal folds and faults strike northwest- ward in harmony with the geologic structure of the northern California Coast Ranges. The most important fault is the Bella Oak thrust fault on which Franciscan rocks have been thrust over Knoxville. It strikes N. 45° W. and dips 10° to 35° SW. Tabular to irregular pipe-like bodies of serpentine occupy many of the faults and some of the sheared bedding planes. The largest bodies are several miles long, 50 to 200 feet thick at the outcrop, strike northwest, and dip southwest. Silica-carbonate rock contained all of the quicksilver ore known to have been mined in the Oakville area. Cinnabar, chiefly in veinlets of chalcedony and quartz, is the ore mineral of La Joya and Bella Oak mines. The finely divided variety known as "paint" is said to have been found in several prospects. Native mercury has not been seen in the district. Considerable pj-rite occurs with the ore at both mines. At La Joya mine a small amount of a solid black hydrocarbon with a bro"svn streak was seen in quartz-lined \aigs in a few of the cinnabar veinlets. The location of the ore bodies was determined by the coincidence of two factors, the first of which was the presence of structural troughs or channels along the major faults. Through these came first the hydro- thermal solutions which formed the most important bodies of silica- carbonate rock along the faulted margins of serpentine bodies. Appar- ently much later, the mercury-bearing solutions rose along the same channels. The second factor was an environment suitable for the deposi- tion of cinnabar. This environment was provided by breccia zones of silica-carbonate rock along the margins of serpentine bodies where abrupt changes in dip and strike caused the solutions to be slowed. Fault gouge and shale played an important part in guiding and blocking the movement of the solutions. M Fix, P. P., and Swinney, C. M., Quicksilver deposits of the Oakville district, Napa and Sonoma Counties, California: California Jour. Mines and Geology, vol. 45, pp. 31-46, 1949. 102 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 La Joya Mine. La Joya mine, the larger of the two in the Oakville area, is in see. 24, T. 7 N., R. 6 W., on the divide between Napa Valley and the head of Dry Creek. It is owned by 11. W. Gould and Company. It apparently includes what in the seventies was known as the Summit or Whitton mine. In this area serpentine bodies have intruded sandstone and shale of the Franciscan group. The Summit claim was located in 1865, apparentlj^ on the summit of the mountain ridge that extends northwest from Mount St. John. The Summit mine was operated until some time after 1881, but its later his- tory is not known. Ore mined in 1872 is said to have ranged from 1 to 2\ percent mercury. Production probably was small, for the ore was carried on mules to a retort of 1^ tons capacity in 24 hours. La Joya mine, including what apparently has been known as the Summit mine, was opened in 1898 but was shut down again the same year. Since then it has passed through the hands of numerous owners. Quick- silver was produced from 1915-18, 1928-34, in 1936, 1938, and 1939. The last work was done by F. A. Bachich and T. C. Mellersh in 1943 when their attempt to reopen the main adit failed at a caved shaly zone 575 feet from the portal. The underground workings, including six shafts and three principal adits, are said to total more than a mile. The main haulage way is said to be about 820 feet long and there are about 900 feet of workings along the strike of the ore-bearing zone. In 1943 the principal stoped areas and all but 1100 feet of workings were inaccessible. All known ore bodies were found in brecciated silica-carbonate rock along the sheared and faulted contacts of serpentine with Franciscan sandstone and shale. The principal mine workings are along the north- west margin of an irregular, pipe-shaped body of serpentine 1500 feet in diameter. jMost of the mine's output came from a westward-plunging trough which forms a narrow, deep pocket filled with brecciated silica- carbonate rock in an unusually sharp re-entrant angle in the margin of the serpentine body. Rich impregnations of cinnabar in the host rock are said to have been found in addition to the usual veinlets of cinnabar, quartz, and chalcedony. The smaller outlying ore bodies are thought to have been localized by similar breccia filled re-entrant angles in serpentine. Bella Oak Mine. The Bella Oak mine is in sees. 20, 21, and 28, T. 7 N., R. 5 W., on the west side of Napa Valley at an elevation of 500 feet above sea level. It is on land owned by Martin Stelling, Jr. The ore bodies were found in silica-carbonate rock in the Bella Oak thrust fault zone. The mine was located in 1868 as two adjoining claims, the Oakville on the north and the Bella Union on the south. Both were operated inde- pendently until 1875 or 1876 when they were merged as the Bella Union mine. Shortly afterward a decrease in the grade of ore mined and a decline of the price of quicksilver caused the mine to be closed. Late in 1876 a little development was done and also during the winter of 1909-10, but not until 1916 did the mine produce again. A 4-year period of inter- mittent production was ended in 1920. In 1928 it became known as the Bella Oak mine, and various leasers produced quicksilver from 1928-34 and also in 1936, 1938, and 1939. In 1942 F. A. Bachich and T. C. Mellersh reopened and deepened one of the old shafts, but no ore bodies were developed. 1949] ECONOMIC GEOLOGY 103 The workings are in three p:roups between wliich there are a few short adits wliich were nnpi-odnctive. There are {il)<)ut ()400 feet of nndcr- ground workings including adits and three inclined shafts; all but 1400 feet were inaccessible in 1943. The important feature of tlie Bella Oak mine is the Bella Oak thrust fault which strikes N. 45° W. and dips 10° to 85° RW. except at two places underground where the dip flattens, reverses, and rolls over again. The hanging wall is conglomeratic sandstone of the Franciscan group, and the footwall is black Knoxville shale. A tabular body of serpentine 30 to 50 feet thick occupies the fault zone in most places. The bodies of silica-carbonate rock, which contained all the known ore bodies, were formed from the lower part of the serpentine mass but are separated from it by several feet of black gouge full of finely sheared serpentine and from the underlying shale by a foot or two of black gouge. The three main groups of workings seem to mark the upper ends of plunging inverted troughs in the hanging wall that guided the quicksilver-bearing solutions upward along the fault. The average thickness of the silica-carbonate rock is about 7 feet, but it varies greatly. It reaches a maximum of 50 feet at one place in the north workings where there is no serpentine, and silica-carbonate rock is in contact with the overlying sandstone. The maximum thickness in the central and south workings is 15 feet. The minimum thickness between the main groups of workings is 2 or 3 feet, and there are spots where no silica-carbonate rock crops out. Cinnabar shows a marked tendency to occur in the lowest part of the silica-carbonate rock, probably because the solutions followed the foot- wall of the fault where less gouge was encountered. Most of the best ore bodies were formed, however, where cinnabar was deposited throughout the entire thickness of silica-carbonate rock where the silica-carbonate rock was brecciated, and its contact with the overlying serpentine flat- tened. The 1943 shaft in the deepest part of the central workings encountered scattered cinnabar in silica-carbonate rock under a plunging inverted trough in the hanging-wall serpentine. Similar conditions prob- ably were found in the lowest parts of the north and south groups of workings also, although little confirmatory evidence was seen in the accessible workings. It is thought that these troughs were the distributary channels which guided the quicksilver-bearing solutions upward to environments favorable to the deposition of cinnabar. They simply mark the "roots" of the known ore bodies and do not necessarily suggest addi- tional ore bodies farther down the dip. Area West of Yountville The Yountville area is on the eastern slope of the ridge between Dry Creek and Napa Valley west of Yountville. The Mountain mine, known also as the Mountain View and Simmons, is located here but has produced little, if any, quicksilver. There are in addition many small prospect pits and shafts whose history has been lost. In this area a block of Franciscan consisting of sandstone, chert, glaucophane schist, and diabase has been thrust upon the Knoxville shales. At one time it probably was continuous with the Franciscan rocks in similar fault contact with the Knoxville north of the head of Dry Creek. On the east the Franciscan is overlain by the Sonoma andesites 104 nKOT.OOY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 and tuffs. A narrow area of silica-carbonate rock lies along the eastern edge of the Franciscan mass. Prominent exposures of it may be seen in sec. 3, T. 6 N., R. 5 W., west of the andesite contact and just north of the road running west from Yountville. Mountain Mine. The Mountain mine is the only prospect of impor- tance in this area. It is about 2 miles west of Yountville on land belonging to Giusep]ie Luechesi. From time to time development work has been carried out, and there are three tunnels, one said to be 400 feet long. No work has been done here for many years. The dump contains serpentine and typical silica-carbonate rock stained with cinnabar. Petaluma Area During 1947 the Cordero Mining Company did considerable develop- ment on Gabinini's property 8 miles southwest of Petaluma, but the property was inactive in 1948. Trenches and the muck from a tunnel now caved indicate that fractured sandstone and shale of the Franciscan contain a body of silica-carbonate rock from which rich specimens of cinnabar were obtained. Stone Introduction Eock suitable for road metal, aggregate, and building stone underlies a large part of the area. By far the greater part of the road metal and aggregate has come from Pliocene volcanics, although the diabase, basalt, and chert associated with the Franciscan group provide a reserve as yet largely untapped. An additional source is the gravel of certain streams which drain areas of volcanic or Franciscan rocks. Operating Quarries Aggregate is currently produced from non-alluvial material by the Marin Gravel Company, Point Reyes Station ; Hein Brothers Basalt Rock Company, Petaluma; the Basalt Rock Company and Juarez Quarry, Napa ; Cordelia Quarry, Cordelia ; and Parish Brothers north of Benicia. The following are now producing aggregate or road metal from stream gravel : Onsrud Construction Company and J. C. Spaletta, Santa Rosa Creek; L. J. Wrobel, C. E. Palmer, and J. P. Serres, Sonoma Creek; H. W. and T. F. McGill, Conn Creek ; W. M. Roderick, Napa River ; and H. V. Smith, Sulphur Creek. Colored building stone and "flagstones" are obtained from the following quarries in volcanic rocks near Glen Ellen : Valley of the Moon, Gerberding, Candy Rock or Nuns Canyon, Johnson, Rainbow, and Gordenker. The stone industry has undergone a revolutionary change since the latter part of the nineteenth century, yet stone has been and remains one of the most important mineral assets in Napa and Sonoma Counties. When cit}' streets were surfaced with paving blocks, quarries in the area thrived and sent blocks to San Francisco, San Jose, and even Stockton. Between 1900 and 1915, with increasing production costs and the need for smoother street surfaces, the paving block industry declined in importance. Of the large number of block quarries, the few that survived are now large producers of crushed rock. These also supply aggregate used in reinforced concrete, a material which has rendered dimension stone almost obsolete. Forty years ago sandstone, hardened tuff, or banded 1949] ECONOMIC GEOLOGY 105 rhyolite was invariably used in the construction of culverts, retaining walls, farm buildings, and even some of the larger bridges and buildings in the area ; but today the building stone industry survives only at the previously mentioned quarries near Glen Ellen. Geologic Distribution Crushed Rock. Crushed rock suitable for aggregate is widely dis- tributed. The volcanics on the east side of the Howell Mountains are largely hard, massive, and dark colored. On both sides of Sonoma and Kenwood Valleys fine-grained andesites, some vesicular, are interbedded with tutfs. The Coutts E^i-othei-s, Hutchison Tvanch, and Titania quarries, and many others too numerous to mention operated in this area.''- Outliers of the southwest extension of the Sonoma andesite that rest upon the Franciscan west of Petaluma provide excellent stone for blocks and crushed rock. On both sides of Napa Valley the rock, which is of especially good quality, has been quarried whenever there was a demand for it. Near Point Reyes Station a chert lens in the Franciscan is a source of crushed rock. Stream Gravel. The gravel of several of the larger streams is made up largely of volcanic cobbles. This material, when crushed, screened, and perhaps washed, is similar to the non-alluvial product described above. Not all the gravel is crushed and screened ; some is used as it comes from the stream for subgrades and road fill. Gravel of commercial grade has been recovered from Sonoma Creek from tidewater to a mile or so northwest of Agua Caliente, from the Napa River 2f miles north of Napa, from Conn Creek 1^ miles east of Oakville, from Sulphur Creek near St. Helena, and from Santa Rosa Creek about 2^ miles northeast of Santa Rosa. Road Metal. More numerous in this area than any other type of operation are pits which supply road metal. ]\Iany are operated on a royalty basis by county highway departments, some by contractors ; a few sell material to private customers. They may be large or small, opened for one job and abandoned, or operated intermittently over a period of many years whenever roads are rebuilt in the vicinity. A wide variety of materials has been used because availability is the primary consideration. Pits have been opened in the Novato conglomer- ate near Black Point, in the Knoxville shale and breccia near Sulphur Springs Mountain, and the Wolfskill sandstone west of Pittsburg. On Point Reyes the quartz diorite has been a source; elsewhere in ]Marin County ciiert and diabase in the Franciscan group have been employed on a small scale. River gravel and unscreened rock from crushing plants have also been used. The most widely used material is the interbedded lava, tuff, and breccia of the Sonoma volcanics. The Meachim and Stony Point pits northwest of Petaluma, the Zameroni, O'Connor, and Onsrud pits near Santa Rosa, the Potter pit west of Napa, the Williams pit in Bennett Valley, and the Joulie pit east of Glen Ellen are all in this type of material. In these variable amounts of lava are interbedded with the tuff, and blasting is occasionally required at most pits. Usually crushing is not necessary, and often power shovels or scrapers load directly into trucks. »2 California State Mining Bureau, Sonoma County : California Min. Bur. Kept. 14, pp. 351-366, 1915. 106 GEOLOGY OF AN AREA NORTH OF SAN FRAl^CISCO BAY [Bull. 149 Building Stone. Hard interbedded sandstone from the Knoxville and Chieo formations have been quarried as building stone. They are exposed in the hills on both sides of Suisun and Wooden Valleys and on the eastern slopes of the Vaca Mountains. Sandstone beds range from 2 to 30 feet in tliiekness, are light grayish broAvn in color, fine grained, and usually of uniform texture and moderate strength. The massive sand- stones of the Franciscan group are usually so badly crushed and weathered that they are not suitable for building purposes. Sandstones of the Martinez, Domengine, and Markley formations have low crushing strengths. The hardened tuffs and banded rhyolites which occur on both sides of the ]\Iiyakma Mountains have been used for local construction. Their hardness, strength, and texture varj^, but carefully selected material can be quarried in large uniform blocks. This type of rock has been used in building the northern bridge over Napa River north of the city of Napa and also the bridge over Milliken Creek. The quarrying of banded rhyolite for "flagstones" and colored building stones near Glen Ellen began about 1937. Travertine. Several small deposits of travertine occur at Tolenas Springs about 4 miles north of Suisun in the Vaca Mountains. These are spring deposits formed by precipitation of the carbonate-bearing water, probably when the springs were more active than now. Similar patches of travertine are found about 3 miles north of the springs near the crest of the Vaca Mountains and also in the hills 6 miles northeast of Suisun on property formerly owned by the Pacific Portland Cement Company. Many years ago beautifully banded pieces of travertine were obtained both here and at Tolenas Springs, but it was impossible to secure large enough blocks for a profitable operation.^^ Descriptions of Individual Operations Producers of Aggregate Parish Brothers. The Parish Brothers operate a pit which is leased from Pacific Coast Aggregate at Hoyt Siding on State Highway 21 about half way between Benicia and Cordelia. A small paving-block quarry was active here in 1890. This enterprise, and an attempt to produce aggregate, failed before 1904. Except for the production of aggregate during 1913 and 1914 no further work was done here until modern times.®* The operation is on an isolated hill composed of southwest-dipping flows and tuff beds of the Sonoma volcanics. The upper beds contain closely spaced angular fragments of hard vesicular black lava in a matrix of tuff. Some of the lava fragments are altered on the surface. Under- lying this is a sandy tuff which has a clastic texture and contains rounded yellow grains. The attitude is most easilv obtained from the lower beds which strike N. 60° W. and dip 72° SW.' Old inactive pits are in both breccia and tuff on the north, east, and south side of the hill. The present work is a bulldozer and scraper opera- tion which is planing the hill from the summit northwest to the screen- 's watts, W. L,., Solano County: California Min. Bur. Rept. 10, p. 668, 1890. ** California State Mining Bureau, Structural materials : California Min. Bur. Rept. 12, p. 390, 1894. . . . Rent. 13, p. 627, 1896. California State Mining Bureau, Solano County : California Min. Bur. Rept. 14, p. 315, 1915. 1949] ECONOMIC GEOLOGY 107 ing plant at the base. The breccia contains very hard fragments, but is sufficiently unconsolidated to permit this method of operation. Rock from the pit is passed through a jaw crusher which feeds a portable screening plant containing rolls and a classifier. At times road metal has been produced, but now the product is absorbed almost entirely by the com- pany's asphalt plant in Benicia. Cordelia Quarry.^'' The Cordelia Quarry, a mile east of Cordelia produces aggregate from an isolated hill composed of Sonoma volcanics. J. M. Nelson is the owner and operator. As early as 1875 paving blocks were produced here, but large-scale operations which within a few years regularl}^ employed 75 to 80 men did not begin until 1883. This quarry was one of the few which successfully changed from producing blocks to crushed rock. The change came about gradually, for although crushing equipment was installed about 1890, a small block production continued until 1913. Since 1913 the pit. although it has changed hands several times, has operated almost continuously. The hill is capped by a thick flow of olivine basalt which dips to the east. The flow is massive and breaks into blocks, some of which are a yard or two in diameter. Along the joints there is frequently up to an inch of a soft apple-green alteration product. Tuff beds lie beneath the basalt and are separated from it by 4 or 5 feet of brick-red material containing bits of scoria. The tuff, Avhich is well exposed in pits on the east and north- east sides of the hill consists of fragments of lava and light-gray tuff in a dark-gray tuffaceous matrix. Rock has been removed from the entire top of the hill, but the present work is at the southern edge of a pit which occupies much of the central part of the hill. A face about 20 feet high is advanced by blasting, and the broken rock is loaded with a power shovel into trucks for a short run to the primarj^ crusher. At present the larger blocks are reduced by second- ary blasting. An electrically operated crushing plant extends from the quarry level down the steep hillside to stock piles and loading chutes at the base. Gyratory crushers and trommels are used throughout. Rock from the large primary crusher is screened, and the undersize is washed in a trommel which separates sand and slime from the overside which is used for road metal. The undersize passes through a screw classifier which produces clean sand. The oversize from the first trommel is then crushed and screened twice more. The final oversize is sent to the aggregate storage pile, and the undersize is added to the road metal produced from the wet trommel. Hein Brothers Basalt Rock Company. The Hein Brothers pit, owTied by Mark Hein, is at Haystack Landing on U. S. Highway 101 east of Petaluma. It is close to the old Petaluma Rock Quarry which formerly produced paving blocks and crushed rock.^*^ The Hein Brothers pit was first opened in August 1925 on a basalt flow 100 feet thick which caps a small hill. Material near the top and bot- tom is scoriaceous and grades inward to a black porph}Ty which is « Watts, W. L,., Solano County: California Min. Bur., Rept. 10, p. 325, 1890. California State Mining Bureau, Structural materials: California Min. Bur. Rept. 12, p. 390, 1894. . . . Rept. 13, p. 627, 1S9G. „„,„,„„- Laizure, C. McK., Solano County : California Div. Mines Rept. 23, p. 212, 192 <. Auburv L E., The structural and industrial materials of California: California Div. Mines Bull. 38, p. 325, 1906. ^ ^ „ . ,. »a California State Mining Bureau, Sonoma County : California Min. Bur. Rept. 14, p. 361, 1915. 108 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 140 higlily vesicular. The central part ol: the How is a fine-grained tough basalt. This pit has a face about 50 feet liigli. Tliirty-foot holes are drilled into tlie too, nud Avlion llieso are bhisted, tlie upper part of the face caves. Two trucks which ai-e loaded by a steam shovel carry the broken rock to the primary crusher wliich is just below the level of the pit floor. The crushing and screeniug plant, which is flexible enough to meet the specifications of any order, is located on the hillside above the highway. Equipment includes two trommels to remove fines from the feed to the secondary crushers which are cone crushers, double-decked vibrating screens, and crushing rolls. Belt conveyors and one .bucket elevator are used. A. B. Siri Pit. The A. B. Siri pit is located just to the east of the Petaluma Hill road near the Steuben School, 4^- miles southeast of Santa Rosa. This operation, which is less than 2 years old, produces crushed rock from a flow on the southwest flank of Taylor Mountain. The lava, which is 150 feet thick, lies between tuff beds. The underlying tuff is sandy and contains partly rounded cobbles up to 2 inches in diameter. It is a hard, bluish, aphanitic rock which is cut by joints spaced so closely that sound pieces greater than a foot in diameter are uncommon. The wider cracks are filled with shaly brown material ; fine cracks are stained sulfur yellow and are commonly lined with dendritic manganese. Blasting is seldom necessary. Formerly several benches were main- tained with bulldozers which pushed material do^vnward from bench to bench. Now one bulldozer scrapes the rock from the top to the edge where it falls to the pit floor, and a second bulldozer brings it to the feed bin. A portable plant has been installed consisting of a belt feeder, grizzly, jaw crusher, and shaking screen. Oversize from the screen is passed through rolls and screened again. The product is nsed for paving and grading. Basalt Rock Com/pany. About 2| miles south of Napa on State Highway 29 and a mile southeast of the sanitarium, is the large pit of the Basalt Rock Company of Napa. AVork began here in 1921 as a hand opera- tion. The first plant, which was built in 1923, was replaced by the present one about 1942.^" Much of the rock quarried is a gray porphyry with feldspar phenocrysts. Some of it breaks easily and is in layers 3 or 4 inches thick separated by rusty seams. Much of it, however, is more mas- sive and stronger. There is a smaller amount of massive, very hard, aphanitic, basalt. Conspicuous joints cut the flows. The flows that are worked lie on beds of tuff and scoria. To the south they consist of beds of moderately consolidated earthy brown ash full of angular fragments of pumice, obsidian, scoria, and lava. Farther north the underlying beds change to a black glassy material containing closely spaced feldspar crystals, and farther still a massive dull red material with streaks of black glass appears. Between these underlying beds and the lava, there is a transition zone a foot thick resembling baked soil. The present quarry consists of a series of benches made by blasting churn-drill holes. The rock, as blasted, contains large masses that require secondary blasting. Rock of varying quality is taken from different parts of the quarry. Approximately half a mile to the east is another large quarry which has now been abandoned. o^Averill, C. V., Napa County: California Div. Mines Rept. 25, pp. 239, 240, 1929. Davis, P. F., Mines and mineral resources of Napa County : California Jour. Mines and Geology, vol. 44, pp. 184-187, 1948. 1949] ECONOMIC GEOLOGY 109 The crushing and screening plant contains a primary jaw crusher which feeds a gyratory. The product of the gyratory crusher is treated on double-decked screens which produce several sizes. The oversize from these screens is reduced by a second gyratory and then rescreened. There is also a simpler plant consisting of a grizzly and trommel. Juarez Quarry. The Juarez Quarry ^^ is a pit owned by M. L. Reidenback and is about 2 miles east of the Napa Station, off Terrace Drive and on the south side of Tulucay Creek. It has been a producer of crushed rock since before 1900. An inclined basalt flow is worked. Where fresh, this is a purple-black rock, very hard and fine grained. Most surfaces, however, have a white coating, perhaps an eighth of an inch thick ; and weathering is pronounced, especially near the surface. Well- developed columnar jointing is present. Beneath the flow are beds of tuff a few inches thick. They are yellow white and non-uniform ; some contain pumice. An old river channel cutting the tuff beds has been discovered. This is filled with cobbles and sufficient clay to tightly pack the gravel. Most of the cobbles, which range from walnut size to cocoanut size, are vol- canic ; but a few are chert and sandstone. The deposit has been worked with disconnected benches at several levels with faces 25 feet high. Blasting is required, and a power shovel is used to load broken rock into trucks for haulage to the nearby crusher. The primary crusher discharges to a screen the oversize, which is recrushed in a cone crusher. The undersize from the first screen goes to the 1-inch stock pile, while the product of the secondary crusher is sized on a graduated screen. The product is used chiefly for road construction by Napa County. Marin Gravel Company. The Marin Gravel Company crushed rock from Franciscan chert on Lagunitas Creek 2 miles east of Point Reyes Station. The pit, which is on the south side of Black Mountain has but a single face, which is 100 feet long and 50 feet high. Blasting is required, and holes are made with wagon drills. Broken rock is passed through a jaw crusher located on the hill just below the pit floor. A belt conveyor takes the product to the secondary crusher, a gj^ratory, and the product of this is sized by a Symons vibrating screen. Five sizes are produced and are placed in stock piles divided by vertical radial steel partitions. Under- ground chutes from these discharge to a common belt conveyor which leads to a smaller bin of several compartments at the road level. Here there is a washing plant and also an asphalt plant. Fairville Quarry and Gravel Company. At the point marked ''Quarries" north of Sears Point on the Mare Island quadrangle the Fairville Quarry and Gravel Company operated a pit from 1907 to 1910.^'' Volcanic breccia and lava flows here dip at about 30° SE. The upper layers are a gray porphyry with many feldspar phenocrysts, some eighth of an inch long. Joints are so numerous that sound pieces greater than about 2 feet in diameter are rare. There is a strong suggestion of columnar jointing. The underlying rock which the quarry penetrated is very porous, amounting to an open netAVork of feldspar crystals contain- "s Averill, C. V., Napa County : California Div. Mines Rept. 25, p. 240, 1929. Davis, P. P., Mines and mineral resources of Napa County, California : California Jour. Mines and Geology, vol. 44, p. 187, 1948. 09 California State Mining Bureau, Sonoma County: California Min, Bur. Rept. 14, p. 355, 1915. I 110 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull, 149 ing angular inclusions an inch or two in size of both porphyry and basalt. In places a canary yellow material fills the interstices; in other places they are filled with a brick-red material. Producers of Creek Gravel J. C. SpaleUa. The Spaletta operation, owned by Mrs. J. C. Spaletta, produced aggregate gravel from the Santa Rosa Creek bottom about 2^ miles northeast of the court house at Santa Rosa. This plant was closed in mid- July, 1948, because of the death of Mr. Spaletta. The pit is approximately 1000 feet in diameter and averages 10 feet in depth. i The gravel consists of material ranging in size from that of fine sand up | to cobbles 6 inches, or occasionally a foot or more in diameter. The cobbles are composed of diabase porphyry, and highly vesicular basalt. Fran- ciscan sandstone fragments are also present, though less common. The gravel was loosened with rooters where necessary and taken with carry-all scrapers to the screening plant at the edge of the pit. Here it was passed over a grizzly where boulders greater than 8 inches in diameter were rejected. From here a shaking screen produced three products. Material greater than 2 inches was reduced in a jaw crusher. That less than 2 inches but greater than 1 inch passed through rolls, and both crushed products passed through the screen again. The minus 1 inch material was taken by belt conveyer to the top of wooden bins where a double-decked shaking screen produced several sizes. An asphalt plant close to the pit absorbed a large part of the output. Onsrud Construction Company. A quarter of a mile to the north- east on Santa Rosa Creek the Onsrud Construction Company had a plant which produced aggregate, but it was dismantled during the summer of 1948. Wrohel Pit. A gravel plant on Sonoma Creek about a mile south- west of the center of Sonoma is operated by L. J. Wrobel. Here from 45 to 50 feet of gravel lie on clay which has not been penetrated. The gravel is unsorted, ranging from sand to cobbles 6 inches or more in diameter. Almost all of them are basalt or andesite, but there is a minor amount of white banded rhyolite and an occasional bit of chert. Cobbles of olivine basalt, highly vesicular lava, and porphyry containing feldspar pheno- crysts are common. Mr. Wrobel is now rebuilding the screening plant. When it is com- pleted, gravel will be taken from the river by an electrically operated scraper and passed over a grizzly to remove cobbles greater than 6 inches in diameter. That which passes through the grizzly will be screened in a trommel. A gravel pump capable of handling rocks 6 inches in size will also be available to supply gravel to the trommel. It will be mounted on a 36-foot landing craft and driven by a 240 horsepower engine. The trom- mel will separate five sizes. Sand will be cleaned in a rake classifier and, will be further sized when additional equipment is obtained. Pea gravel, f-inch rock, and drain rock (| to 2| inches) will be stored in bins. That greater than 2| inches will be crushed and passed through the trommel again. Palmer Pit. Two and a half miles below the Wrobel plant C. E. Palmer operates a pit, but there is no washing or screening equipment. Gravel which is used for fill is loaded with a drag line scraper directly into trucks. The gravel is similar to that at the Wrobel pit except that it contains little, if any, rhyolite. 1949] ECONOMIC GEOLOGY 111 Serves Pit. Gravel similar to that at tlio Wrobel pit but containing a considerable amount of rhyolite occurs in Sonoma Creek a mile above Agua Caliente. J. P. Serres has a screening plant here, but it has not been used for 2 or 3 years. McGill Pit. The McGill plant owned by N. W. and T. F. McGill is on Conn Creek 1^ miles east of Oakville. This plant began operating in 1929 and was acquired by the present owners in 1932. The gravel is unsorted, ranging from sand up to 8-inch pieces which are rounded, but flatter than cobbles. Over half of it is sandstone and chert with subor- dinate serpentine from the Franciscan ; most of the remainder is volcanic, either gray porphyrj", red porphyry, or black vesicular rock. Gravel is taken from bars at several points within 2 or 3 miles of the plant. The plant has been described by Davis ^^" as follows : ' ' The creek gravels are loaded to dump trucks by an Insley crawler-mounted clam- shell bucket. * * * The trucks dump to a bin feeding a vertical bucket elevator which discharges to a revolving screen. Here the feed is sprayed and screened. All products except the sand pass directly to the underlying storage bunkers. The sand is removed by a screw conveyor to an adjoining bunker. The screen oversize is carried by chute to a recently installed Straub jaw crusher. The crusher discharges to a chute which returns the crushed material to the elevator. The products usually made are 1^-inch rock, pea gravel, and sand. On special orders such products as 25-inch rock can be produced by suitable screen adjustments. This plant is of wood construction and is electrically operated by a 30-horsepower motor. ' ' Roderick Pit. On the Napa River about 21 miles north of Napa W. M. Roderick has been obtaining gravel intermittently for 23 years. There is no plant, but gravel, sand, and loam are obtained by selecting material from bars along a half mile section of the river. Smith Pit. H. V. Smith recovers gravel from Sulphur Creek a mile southeast of Spring Street and a quarter of a mile southwest of State Highway 29 near St. Helena. The gravel which has a maximum size of about 3 inches is finer than other creek gravels described above. It is com- posed almost entirely of a medium-grained, poorly sorted, gray, arkosic sandstone. The plan has been described by Davis ^"^ : "A new washing and screening plant has been built to produce graded aggregate from creek gravel. A scraper moves the gravel to a bin set over a 100-foot inclined belt conveyor which discharges its load onto the bed of a three- decked 4 by 8 foot shaking screen. A water spray removes the clay and fine dirt. The screen separates four products, namely: plus 1^ inch (over- size) ; minus I5 inch to plus f inch; minus f inch to plus f inch; and minus f inch or sand. The oversize is carried by chute from the top screen to a Telsmith 2-H reduction crusher driven by a six-cylinder gasoline engine. The crusher product is discharged onto a second inclined con- veyor belt about 60 feet long traveling counter to the first belt. This second belt terminates at a chute set normal to the conveyors, where the load is transferred back to the original belt and screened. The inter- mediate screen products are moved by chutes to compartments in a 12- by 12-foot bunker. The sand is collected below the bottom screen and moved by an inclined screw conveyor to an adjoining 10- by 10-foot bunker. This plant is wood construction on concrete foundations. ' ' iw Davis, F. F., Mines and mineral resources of Napa County, California : Cali- fornia Jour. Mines and Geology, vol. 44, p. 188, 1948. i« Davis, F. F., Mines and mineral resources of Napa County, California : Cali- fornia Jour. Mines and Geology, vol. 44, p. 188, 1948. 112 GEOLOGY OF AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 Producers of "Flagstones" and Colored Building Stone Valley of flic Moon. Quarry. The Valley of the Moon or Cabrol quarry is one of the largest producers of ' ' flagstones ' ' in the area and has operated more or less continuously' since 191^8. It is owned by S. Cabrol but leased and operated by R. J. Johns. The quarry is south of Trinity Road half a mile from State Highway 32 in sec. 10,'t. (5 N., R. G AV. The rock quarried is a blue-gray banded rhyolite which readily splits into layers 1 or 2 inches thick, along parting planes formed by tiny elongated vesicles. The layers are nearly horizontal and almost parallel, although near the edges of the quarry they become somewhat distorted. This banded rhj^olite seems to occur as large irregular masses in the volcanics. In quarrying, occasional blasting with light charges of slow dynamite, is necessary. Blocks are pried out and hauled onto the quarry floor where they are split by hand. Gerherding Quarry. The Gerberding quarry is now leased by Richard Pittock. It is northwest of the Valley of the Moon quarry, north of Trinity Road about half a mile from State Highway 12. The quarry 3'ielded a large quantity of stone, including that produced in 1928 and 1929 when J. S. Taylor had a lease, but not much valuable stone remains. It also produced a porous banded rhyolite which, however, is less uniform than that at the Valley of the Moon quarry. Red bands, or more commonly red films, occur along the porous parting planes. The quarry now in use is a pit approximately 100 by 200 feet in plan by 20 feet deep, but there are several abandoned openings as large as this. Candy Rock Quarry. A mile and a half up Nuns Canyon from State Highway 12 in sec. 3, T, 6 N., R. 6 W., is the Candy Rock or Nuns Canyon quarry, owned and operated by V. 0. Campbell. Highly colored building blocks, gray, green, and pink, are produced very occasionally by the owner and a helper as the demand for them arises. The rock, a blocky altered rhyolite heavily stained with limonite along the joints, is some- what softer than steel, and banded, although it does not split along the bands. In general the blocks are pink at the center with a very irregular outer zone of gray or green suggesting alteration which worked in from the joints. The blocks are cut by cracks perhaps yV of an inch wide in which tiny quartz crystals and cubes of pyrite, partially altered to limonite, have formed. In places the rock is spotted with blebs of opal, while in others there are small chalky looking amygdules partially filling rectangular openings. Here and there an irregular calcite veinlet as much as f of an inch wide cuts the rock. Johnson Quarry. The Johnson quarry is on land belonging to Wil- liam Youngman near Trinity Road, a mile from State Highway 12. "Flagstones" are produced here, in a quarry that now has a face 20 feet high and approximately 100 feet long. The rhyolitic flows, which readily split into flat slabs an inch or more thick, strike on the average N. 55° W. and dip 60° SW. The rock is gray, fairly hard, and contains ^-inch layers separated by more or less connected vesicles in planes. An occasional phenocryst of plagioclase which lies at an angle to the layering is large enough to cut one or two of the layers. Rainbow Quarry. John Sitenga, contracting stone mason, obtains both flagstones and building stones from the Rainbow quarry located in sec. 36, T. 6 N., R. 6 W., half a mile east and a little north of the Agua Caliente Post Office. 1949] ECONOMIC GEOLOGY 113 The rock in the southwest part of the deposit is a soft, blue-gray rhyolite which splits readily along layers of flattened vugs 1 to 3 inches apart. Along some of these parting planes there is a red stain of iron. To the southwest, this rock abuts against perlite in a steeply dipping fault contact which strikes northwest. At the northwest end of the deposit the perlite is not exposed. The rock quarried is porous, ashy looking, stained yellow and red with iron oxide, and crumbles easily. Both varieties have a mica-like sparkle caused by very small quartz crystals. The quarry consists of three openings, each about 15 yards in diameter at one level along the hillside and within 100 yards of each other. The most southeasterly one is behind the perlite and is reached through a narrow cut about 40 feet long. Light blasting is occasionally necessary. It has been found that rock within 3 feet of the surface is weathered and must be discarded. Freshly quarried stone is damp and crumbles instead of splitting cleanly. Splitting is done with a blunt axe-like tool. Oordenker Quarry. A banded rhyolite deposit on land belonging to the Annadel Farm on Bennett Mountain 1^ miles west of La\vndale was leased bj' Rodney Gordenker early in 1948. Both blocks and flag- stones are produced. The rhyolite is harder than at the Valley of the Moon quarry but splits less readily. Layers are ^o to ^ of an inch thick, and are alternately pale pink and green or white. The beds are nearly horizontal and grade successively westward into scoria and perlite. A bench 15 feet wide and 60 feet long has been made. The rock is split by hand and broken transversely with a hydraulic cutter. Water Resources Ground Water Ground water occurs in both the consolidated rock formations and in the valley alluvium and small supplies sufficient for domestic use are obtained in all the nine quadrangles. Water is found near the surface in the alluvium of the valleys and is recovered in shallow-dug wells. The weathered rock debris, ranging from 5 to 15 feet thick, which covers most of the sendimentary and igneous formations, furnished water for domestic purposes from dug wells. In the more thickly settled communi- ties and in areas near a source of contamination, many of these shallow wells may become unsatifactory from a sanitary standpoint. The rock formations which compose the mountains and underlie the alluvium in the valleys consist chiefly of sandstone, shale, and volcanic rock. The marine sandstones of the Franciscan group in northern Marin County yield little water except at the contact with igneous rocks. Supplies for municipal use and for irrigation are obtained generally from deeper wells in the alluvium or from water-bearing beds of tuff or sandstone which are discontinuously pervious and form the water-bearing strata of the bed rock. Tlie gravelly parts of the alluvium are, however, the most dependable water-bearing materials and will usually yield the largest supplies. The precipitation on the valley and from streams which discharge into the valley from the surrounding mountains or hilly areas accumulates in the valley alluvium as ground water. During the rainy season, a considerable volume of water is added to storage in porous beds of the alluvium. During the dry season, however, ground-water storage diminishes greatl}^ owing to evaporation and transpiration, seepage into certain streams, and withdrawal from wells. Hence, there is an annual 8A — 7173 114 GEOLOGY OP AN AREA NORTH OF SAN FRANCISCO BAY [Bull. 149 fluctuation of the water table caused by the replenishment during the rainy season and the depletion during the dry season. There is also a fluctuation from year to year resulting from fluctuation in yearly precipitation. Because the alluvium varies in composition with depth and with locality, water-bearing beds are found at varying depths from place to place. In general, enough water for domestic and stock purposes can be found at shallow depths, and w^ells for these purposes are usually less than 30 feet deep. On the areas of alluvium west of Suisun and Fairfield, a number of wells are 40 feet deep and the water level is usually 15 feet below the land surface. Similar conditions exist in Napa Valley, although some of the wells are deeper. For domestic purposes and for watering of stock, shallow wells are adequate, but for public supply and irrigation it is generally necessary to sink wells somewhat deeper so as to penetrate a greater thickness of water-bearing materials. In general, the beds of fairly assorted gravel and coarse sand yield water to wells freely, but clayey and silty beds yield water so slowly that they are of little value as sources of water in wells. Surface Water The surface water within the area of the nine quadrangles is dis- charged into Sacramento River and Suisun, San Pablo, and Tomales Bays through numerous rivers and their tributaries. The surface water of the Great Valley of California at the junction of the Sacramento and San Joaquin Rivers in the southern part of the Antioch quadrangle is discharged into Suisun Bay and thence through Carquinez Strait into San Pablo and San Francisco Bays. The principal tributaries of Sacra- mento River in the area under investigation are Putah, Ualtis, and Alamo Creeks. Suisun Bay receives the drainage of the Suisun, Green Valley, Sulphur Springs Valley and Pacheco Creeks and Arroyo del Hambre. The surface waters of Carneros, Sonoma, Tolay, Petaluma, Novato, Gallinas, and Rodeo Creeks and Napa River discharge into San Pablo Bay. The northwestern part of the Santa Rosa quadrangle is drained through Santa Rosa Creek and its tributaries into Russian River and thence into the ocean. The western portion of the Petaluma quadrangle and all of Point Reyes quadrangle east of Tomales Bay is drained through Olema, Lagunitas, Salmon, Chileno, and Walker Creeks into Tomales Bay and thence into the ocean. The drainage of the Point Reyes Penin- sula east of Inverness Ridge is carried by numerous short creeks into Tomales Bay and that on the western side of the ridge by numerous creeks directly into the ocean. ACKNOWLEDGMENTS The study of the Napa area originally was undertaken at the sug- gestion of Dr. A. C. Lawson to whom the writer wishes to express deep gratitude for many helpful suggestions and valuable criticisms not only during the early stages of the investigation but during later years when the study involved a larger territory. The writer wishes to express his acknowledgment to Dr. J. C. Merriam, Dr. R. E. Dickerson, Dr. F. M. Anderson, and the late Dr. B. L. Clark, whose numerous publications have presented much information which could be applied to the area under discussion. The investigations of 1949] BIBLIOGRAPHY 115 Dr. R. A. Stirton and Dr. Chester Stock on the fossil mammals have been of direct aid in the correlation of certain formations of continental origin. The work of many other contributors whose investigations were consulted are listed in the chapter on literature. The opportunities afforded the writer by the Paleontological Museum of the University of California and the California Academy of Science for comparisons of material with the type collections has been of tremen- dous aid in the preparation of the manuscript. The geologic maps of the nine quadrangles and the accompanying -cross sections were submitted to the U. S. Geological Survey and the resulting geologic cartography is due entirely to the efforts of Porter L. Mattox and Mr. Pusey. Dr. G. W, Stose contributed greatly in the earlier preparation of the maps. BIBLIOGRAPHY Allen, Victor T., The lone formation of California : Univ. California Dept. Geol. Sci. Bull., vol. IS, pp. 347-448, 1929. Anderson, F. M., Some Cretaceous beds of Rogue River Valley, Oregon : Jour. Geology, vol. 3, pp. 455-468, 1895. Anderson, F. M., The geology of Point Reyes peninsula : Univ. California Dept. Geol. Sci. Bull, vol. 2, pp. 119-153, 1899. Anderson, F. M., Cretaceous deposits of the Pacfic Coast: California Acad. Sci. Proc, 3d ser., Geol., vol. 2, pp. 1-54, 1902. Anderson, F. M., A stratigraphic study in the Mount Diablo Range of California : California Acad. Sci. Proc, 3d ser., vol. 2, pp. 155-248, 1905. Anderson, F. M., A further stratigraphic study in the Mount Diablo Range of California : California Acad. Sci. Proc, 4th ser., vol. 3, pp. 1-40, 1908. Anderson, F. M., Jurassic and Cretaceous divisions in the Knoxville-Shasta suc- cession of California : California Div. Mines Rept. 28, p. 316, 1932. Anderson, F. M., Knoxville-Shasta succession in California : Geol. Soc America Bull., vol. 44, pp. 1137-1270, 1933. Anderson, F. M., Lower Cretaceous deposits in California and Oregon : Geol. Soc. America, Special Paper 16, pp. 1-339, 1938. Anderson. F. M., Faunal and chronological aspects of the Upper Cretaceous in the Great Valley of California : Geol. Soc. America., Proc 1937, p. 235, 1938. Anderson, F. M., Synopsis of the late Mesozoic in California : California Div. Mines Bull. 118, pp. 182-186, 1941. Anderson, Robert, and Pack, R. W., Geology and oil resources of the west border of the San Joaquin Vallev north of Coalinga, California : U. S. Geol. Survey Bull. 603, 1915. Antisell, Thomas, Geological report, in Reports of explorations *** for a rail- road from the Mississippi River to the Pacific Ocean : 33d Cong., 2d sess., S. Doc. 78, vol. 7, pp. 1-204, 1856. Applin, E. R., Correlation of the California Ttirritella andersoni zone with the Gulf Coast Eocene (abstract) : Geol. Soc. America Proc 1934, p. 392, 1935. Arnold, Ralph, The Tertiary and Quaternary Pectens of California : U. S. Geol. Survey Prof. Paper 46, pp. 15-17, 1906. Ashley, G. H., Studies in the Neocene of California : Jour. Geology, vol. 3, pp. 434-454, 1895. Ashley, G. H., The Neocene stratigraphy of the Santa Cruz Mountains : Cali- fornia Acad. Sci. Proc, 2d ser., vol. 5, pp. 273-367, 1895. Anbury, L. 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Clark, Bruce L., The San Lorenzo series of middle California : Univ. California Dept. Geol. Sci. Bull., vol. 11, pp. 45-234, 1918. Clark, Bruce L., Stratigraphic and faunal relationships of the Meganos group, middle Eocene of California : .Tour. Geology, vol. 29, pp. 143-145, 1921. Clark, Bruce L., Marine Tertiary of the west coast of the United States : Jour. Geology, vol. 29, pp. 586-614, 1921. Clark, Bruce L., The Domeugine horizon, middle Eocene of California : Univ. California Dept. Geol. Sci. Bull., vol. 16, pp. 99-118, 1926. Clark, Bruce L., Stratigraphic and faunal horizons of the Coast Ranges of Cali- fornia, p. 22, 1929. Published privately by B. L. Clark. Clark, Bruce L., Tectonics of the Coast Ranges of middle California : Geol. Soc. America Bull., vol. 41, pp. 747-828, 1930. Clark, Bruce L., Pliocene sequence in the Berkeley Hills (abstract) : Geol. Soc. America Bull., vol. 44, p. 151, 1933. Clark, Bruce L., Tectonics of the Mount Diablo and Coalinga areas : Geol. Soc. America Bull., vol. 46, pp. 1025-1078, 1935. Clark, Bruce L., Fauna from the Markley formation (upper Eocene) on Pleasant Creek, California : Geol. Soc. America Bull., vol. 49, pp. 6S3-7.S0, 1938. Clark, Bruce L., and Palmer, D. B. K., Revision of the Eimella-like gastropods from the west coast of North America : Univ. California Dept. Geol. Sci. Bull., vol. 14, pp. 277-288, 1923. Clark, Bruce L., and Vokes, Harold, Summary of marine Eocene sequence of western North America : Geol. Soc. America Bull., vol. 47, pp. 851-878, 1936. Clark, Bruce L., and Woodford, A. O., The geology and paleontology of the type section of the Meganos formation (lower-middle Eocene) of California: Univ. Cali- fornia Dept. Geol. Sci. Bull., vol. 17, pp. 63-142, 1927. Clark, Clifton W., The geology and ore deposits of the Leona rhyolites : Univ. California Dept. Geol. Sci. Bull., vol. 10, pp. 361-382, 1917. Crickmay, Colin H., The Jurassic rocks of Ashcroft, British Columbia : Uuiv. California Dept. Geol. 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Ill Post Office, 112 Springs, 92 Alamo Creek, 114 Alaska. 78 Alcatraz Island, 19 Alvernaz, M., owner Alvernaz pit, 96 pit. 95 American Canyon, 34. 35, 59, 69, 71, 79, 86 fault, 71 Minerals Company, 87 Anderson. F.M., cited, 14. 21. 22, 23, 24, 25, 26, 33 Anadara montereyana, 44 Angel Island. 19 Annadel Farm. 113 Antioch quadrangle. 10. 11, 12, 14, 31, 35, 37, 43, 49, 52, 53, 54, 61, 72, 74, 114 Antisell, Thomas, cited, 13 Arrowhead Mountain syncline, 75 Arroyo del Hambre, 38. 114 Asiatic, faunas. 80 Astrodapsis hreicerianus Rcmond,4:l cierioensis, 42 pailoensis, 42 ttiniidus, 43 Atlas Peak, 69 Aubury, L.E.. cited, 87, 88, 107 AuceUa, 11, 19, 78 tereiratuloides, 24 crassicoUs, 24 piochii, 26 sp., 26 stantoni. 26 Averill, C.V., cited, 87, 91, 108, 109 Bachich, F.A., 102 Bailey, — , 95 T.L.. cited. 14, 93 Road. 95 Basalt Rock Company. 87. 95, 96, 108 Bear Valley syncline, 72 Beck, E.C.. lessee Brownlie mine. 101 BeUa Oak fault. 101, 102. 103 mine. 101. 102, 103 Union mine, 102 Bellemnites tehamaensis Stanton, 26 Benicia, 13. 32, 43. 52. 71. 73, S3, 104, 106 Bennett Valley. 44, 45. 62, 105 Mountain. 113 Bergum. lessee Walker pumice pit, 97 Berkeley Hills. 47. 72 block, 66, 68, 72, 82 Berryessa Valley, 11, 22 Bismark Knob, 63 syncline, 73 Black Mountain, 11, 109 syncline, 72 Point, 105 • Prepared by Geil Bartels. (123) 124 INDEX I l?luo Hock Springs, !U Boiilk'h. K.S., cited. S4 li(>(lt\L:;i I lead, r>G, l>(» Boliiiiis. ()(! Boyes Spring's, !)1 Hot Spriiifjs, !H Bradley, W.W., cited. 100 llraiiner.J.C, cited. 1(i. 17 Bra/.t'lton. owner of fullers earth deposit, 8.T Brazil and (Vmiiell. owners Knutte mine, !)() Briones sandstone, 15, 31>, 40, 41, 42, 44, 74 British Columbia. 7S Brof^an. J.S., owner Kohler and Chase deposit, S4 Brownlie mine, 9S. 101 ISrown's Valley. .■'.;'.. 70 anticline, 73 fault, 70 Burden Mountain. 4S. .lO. 61, G2, 67, 75, 82 fault, 67 Byron quadrangle, 42 Cabrol. S., 112 Calabazas Creek, 42, 44, 68 California, IS). 20. 21, 25, 26, 85, 40, 52, 72, 76. 79, 80, 81, 98, 101 State ^NliniuK Bureau, cited. 86. 9.S, 105, 106, 107, 109 , University of, 12, 13 Camp. Charles L., cited, 19 Campbell, 94 , V.O., owner Candy Rock quarry, 112 Canada del Cierbo, 39. 41. 42 Candy Rock quarry, 104, 112 Cannou anticline. 4 Capay formation, 31, 32, 33, 74, 79, 93 Valley, 33 Capell Creek, 89 syncline. 74 Valley, 21, 22, 58, 69 Carneros anticline, 73 Creek, 36, 37. 40, 42, 44, 68, 114 fault, 44, 68, 69, 73, 75 Valley, 36 Carquinez quadrangle, 10, 14, 24, 31, 32, 33, 35, 36, 37, 38, 39, 40, 41, 42, 46, 49, 52, 54, 58, 59, 68, 71, 73. 74. 79. 93 Strait, 10, 11, 12, 13, 26, 32. 37, 39, 52, 53, 71, 73, 79, 80, 82, 83, 84, 85, 114 Carriger Creek syncline, 75 Cement, 88, 93 Cenozoic epoch, 14 Chesterman, C.W., cited, 94 Chico Creek, 26 formation, 23, 24, 26, 29. 69, 71. 74, 77, 78, 79, 105 group, 26, 28, 29, 92 series, 20, 22, 24, 27, 28, 29, 32, 38, 40, 41, 53, 73, 74 stratigraphic section of, 28 Chileno anticline, 72 Creek, 114 Cicero, C, lessee Cicero pumice pit, 96 pumice pit, 95, 97 Cierbo sandstone, 15, 35, 39, 42, 43, 81 time. 44 Claremont shale, 15. 38, 47, 72 Creek, 38 Clark, Bruce L., cited, 13, 14, 34, 36, 37 Coalinga, 33 Coast Ranges, 8, 10. 11, 12. 14. 16, 19, 20, 21, 22, 25, 26, 27, 31, 36, 46, 58. 57, 66, 72, 76, 77,79,80,82,90,92,101 INDEX 125 Concord quadrangle, 31. 3G, 37, 38, 39, 40, 47, 71, 73 Coney Ranch, owner of porlite deposits, 05 Conn Creek, 104. 10"), 111 anticline, 70 Canyon, 70 Yallev, 50, 61, 69 fault, 70 Connell and Brazil, owners Knutte mine, 90 Contra Costa County, 8, 10, 26, 32, 37, 38, 46, 47, 80 Hill, 101 Corhiciila gahbiana, 46 Cordelia, 43, 104. 106 quarry. 104, 107 Cordero Alining Company, 104 Cotati, 11 -Petaluma Valley, 61, 62 Valley, 10. 45, 53. 61. 62, 81, 82 Coutts Brothers quarry, 105 Cowlitz formation, 35 Creston syncline, 73 Cretaceous period, 13, 14, 19, 20, 21, 23, 24, 25, 31, 43, 66, 71, 84, 88, 93 Lower, 21, 22, 25, 34, 77, 78 middle, 29 Upper, 26, 32, 34, 92 Dana, J.D., cited, 13 Davis, E.F., cited. 17 , F. F., cited. 84, 90, 91, 96, 97, 108, 109, 111 Dennis, Clifford K., 98 Deuverton, 49 Desmoceras, 78 Devil's Gorge. 24, 27. 28 Diablo Pumibloc Company, 95 Dickerson. Roy E.. cited, 13, 86 Dietrich. W.D., cited, 85 Diller, J.S., cited, 20 Dohrman deposit, 87 Domengine age, 79 formation, 31, 33, 34, 59, 62, 69, 70, 71, 73, 74, 86, 93, 94, 106 Ranch, 33 Dorf, Erling, cited, 47 Dosino Dicrrianii, 42 Dothan formation, 20 Double Point, 52 syncline, 72 Drake's Bay, 11, 53 Drakes Estero, S3 syncline, 72 Dry Creek, 102, 103 syncline. 73 Valley. 70, 75 Ducker Well, 94 Dunn's Peak, 33 Echinarachnius gaihi, 42 Eckel, E.C., cited, 89 Eel River, 8 El Dorado County, 88 El Verano, 91 Elkhorn Peak, 35 Elmira, 92 Enterprise anticline, 75 Eocene epoch. 20, 31, 59, 73, 74, 79, 84, 92, 94 lower, 31 middle, 35, 55 upper, 31, 35 126 INDEX Etchofroin formntion. 50 Kuri'ka Scluxd, 4."). 7- Eiirope, 78 Faiiti.'ld. 74, SS, 93, 114 Fairville, OS QuiiiTy and Gravel Company, 100 Faralloii Islands, r.n. 7(? FotttTs Hot Spring's. Oli FicuK gliinfonlcusis, 42 Fix, r.F.. cited. 101 Foss Valley syncline, 7G Franciscan formation, 14. 10, IS. 10. 20, 22, 2'., 44, 4.'), 48, 50, 52, 54, 55, 50, 57, 5S, .50, 02. (i(), (>7, 08. 00, 70, 72. 75, 70,' 77, SO, 81, 87, 89, 90, 93, 94, 101, 102. 103, 104, 105, 100, 111, 113 post-, 07 pre-, 10, 55, 70 Franklin fault, 71, 73, 74 syncline, 73 Frazier, A.AV., owner Frazier pumice pit. 95 pumice pit. 95 Furmau, lessee Alvernaz pit, 96 Gabb. W.M., cited. 13, 26 Gabilan Ranj;e. 70 Gabinini. — , 104 Galice formation, 19, 20 Gallinas anticline, 72 Creek, 114 Station, 85 Gates Canyon, 29 Geig, lessee Alvernaz pit, 96 Gerberding quarry, 104, 112 Glen Ellen, 85, 87, 95, 104, 105, 100 formation. 50. 51 Golden Gate, 10, 19, 56, 66, 82, 83 Goldstein Ranch, 87 Goodyear, W.A., cited, 86 Station, 42, 43 GoniohnKis rodeoensis, 46 Gordenker, quarry, 104, 113 . Rodney, lessee Gordenker quarry, 113 Gordon Valley, 21, 22, 26, 70, 74 anticline, 23, 70, 74 reservoir, 22, 23 Gould, H.W., and Company, owners La Joya mine, 102 Graham Creek anticline, 75 Grand View, 67 Grapevine Canyon, 35 Grayson Creek, 36, 37 Greasy Bank Creek, 89 Great Valley of California, 82, 83, 114 Green Valley. 71 Creek, 114 fault, 71 River, 71 Gualala beds, 78 Hagin Creek, 45 Hambre sandstone, 15, .38, 39 Harris, E., owner of a hot springs resort, 92 Hastings estate, owner Hastings quicksilver mine, 100 quicksilver mine, 09, 98, 100 Haystack Landing, 107 Hayward fault, 07 INDEX 127 Hein Brothers Basalt Kot-k Company, 104 pit. 107 , Mark, owner Hein Brothers pit, 107 Hercules shale member, 15, 40, 41 Station, 41 Hickman, Al, lessee Agua Caliente Springs, 02 Hinde. G.H., cited, 19 Ilipparion, 4."), 46 Halst-AVeeks prospect, 00 Honker Bay, 03. 04 Horsetown formation. 21, 23. 24, 26, 20. 03 ; stratigraphic section of, 23, 24 Howell :Mountains, 10. 11, 61, 62, 63, 66, 73, 74, 82, 105 Hoyt Siding, 106 Hudson, F.S., cited. 00 Huichica formation, 50, 51, 53, S3 Creek, 50 Hutchinson Ranch quarry. 105 Hyatt, Alpheus, cited, 10 Ichthyosaurus posthumus, 10 Industrial Highway, 31, 34, 36, 41 Inoceramus. 10 if^i/neyiGabb, 28 International Filter Company, 91 Inverness. 16 Park, 89 Ridge, 11, 40, 56, 67, 114 Jameson Canyon, 35, 61, 71, 70 shale, 35 syncline, 73 Johns, R.J., lessee Valley of the ^loon quarry, 112 Johnson, F.A., cited. 92, 93 , W.S., and Harry, owner Boyes Hot Springs, 01 quarry, 104, 112 Joulie pit, 105 Juarez quarry, 104. 109 Jurassic period, 19, 21, 25, 26 pre-, 14, 55 Upper, 20, 21, 25, 26, 55, 77, 78 Kawana Springs, 86, 91 Kenwood, 51, 75, 91, 92, 95 -Sonoma syncline. 75 Valley, 10. 51, 82, 105 Kimmeridgian, 20 Kirby, J.M., cited, 14 Hills, 54 gas field. 03. 94 Kirker Creek. 49 Klamath River. 8 Kleinpell. R.M.. cited. 31 Knoxville formation. 16, 19, 21, 22. 23. 26. 27. 20. 36, 57, 59. 61, 62, 66. 68. 69. 70. 73. 74, 76, 77, 78, 79. 84, 93, 98, 100, 101. 106 : stratigraphic section of, 23. 24 post-, 55 pre-, 57 shale. 25, 53, 54. 63, 68, 60, 88, 98, 99, 100, 103, 105 Knutte, L.R., lessee Knutte mine, 90 mine. 00 Kohler and Chase, owners Kholer and Chase deposit, 84 deposit, 84 La Jolla mine, 60 La Joya mine, 101, 102 Lafayette. 47 Dam, 47 Lagunitas Creek, 57, 109, 114 128 INDEX Lninl sandstone, 30 Laird's Laudiuji, 30 Laizure, C. Mi-K. citt-d. ST, 107 Lake Connty, 7S Lakeville. 4") fault, 04 School, (!S, 7") Lava-Lite Products Company, lessee AVilson pumice pit, 07 Lawlor R.-incli hcds, SlJ Ravine. 42, CI tuff, 48, 40, 55, (>1 Lawudale, 113 Lawson, Andrew C cited, 13, 10, 17, 37, 40, 41, 66, 71 Lepori, .Tohn, owner ^'ich.v Springs, 02 Logan, C.A.. cited, 88, 80 Los Guilicos Warm Springs, 02 Los Medanos Hills. 10, 35, 42, 43, 40, 53, 61, 72 Lucchesi. Giuseppi, 104 Lynch Creek, 45 Lytoceras, 78 McCarthy Creek, 26 McGill, N.W.. owner IMcGill pit, 104, 111 pit. 111 . T.F.. owner McGill pit, 104, 111 Mare Island, 40, 52, 71, 83 quadrangle, 21, 32, 37, 38, 30, 40, 41, 42, 46, 47, 50, 52, 60, 63, 72, 73, 75 Marin County, 8, 10, 17, 48. 81, 03, 08, 105, 113 Gravel Company, 104, 100 Peninsula, 16 Mariposa slate, 10, 20 Markley age, 70 Canyon, 34, 35 sandstone, 31, 34, 35, 42, 43, 44, 40, 65, 72, 74, 03, 106 Martinez age, 78 formation, 13, 20, 26, 31, 32, 33, 36, 37, 40, 71, 73, 74, S3, 03, 106 Strait, 12 syncline, 31, 32, 33, 34, 36, 37, 40, 41. 71, 73, 70 Martini, Louis, owner Goldstein Ranch, 87 Matanzas anticline, 72, 73 Mazza, R., 00 Meachim pit, 105 Meelcia sella, 28 Meganos formation, 31, 85, 03 Mellersh, T.C., 102 Mendocino County, 78 Range, 8, 10, 11, 62 Merced formation, 44, 45, 47, 48, 50, 52, 63, 66, 67, 72, 74, 75, 81, 82 Lake, 47 post-, 72. 73, 74 pre-, 72, 74. 81 Merriam. J.C, cited, 13, 20, 46 INIesozoic era, 14, 76, 101 Metamorphic rocks, 18 Middletown, 43 syncline, 73 Mill Creek, 70 Valley, 70 Millerton, 42, 52 formation, 50, 51, 52, 83 Head, 51, 52 Milliken Creek, 62, 70, 106 anticline, 76 I INDEX 129 Miocene epoch, 31, :?9, 40, 46, 55, 56, 68, 71, 80, 84, 89 ; formations of, 37, 52 ; sediments of, 56 middle, 15, 38, 44, 80 post-, 67 pre-, 67 upper, 15,41,47,81 Miyakma anticline, 75, 76 Mountains, 8, 10, 11, 61, 62, 63, 66, 75, 76, 95, 106 Montara block, 66, 67, 82 Monterey age, 80 Bay, 52, 76 shale, 15, 36. 37, 39, 40, 41, 66, 72, 73, 80, 83 Montezuma formation, 49, 50, 51, 52, 53, 83 Hills. 10, 11, 49, 51, 52 Montgomery, T.S., 88 Monticello, 25 Road, 24 Moredo, — , 90 Moreno formation, 27, 28. 92. 93 Morse, Roy R., cited, 14, 46, 93 Morton, H.L., owner Los Guilicos Warm Springs, 92 Mount Diablo, 14. 26, 40, 42, 78 quadrangle, 34, 49 George, 95. 96 Hood, 11, 51, 62 Luffman, 99. 100 Pisgah Vineyard deposit, 87 St. Helena, 10, 11, 63 St. John, 98, 99, 100 Vaca, 11, 27, 35, 46. 53, 61, 63, 65, 73 quadrangle, 11, 12, 19, 21, 22, 24, 26, 69, 70, 79, 95 Mountain mine, 103 Schoolhouse, 86 Muir Station, 34 Mulinia pabloensis, 43 Murphy Well, 94 Murray Ranch coal deposit, 86 Mussel Rock, 66 Napa, 33, 40, 62, 63, 70, 84, 91, 92, 95, 96, 97, 104, 105, 106, 108, 111 County, 8, 59, 94, 104 Junction, 35. 68, 88, 89, 90 quadrangle, 12 River, 31, 83, 104, 105. 106, 111, 114 Soda Incorporated, 91 Springs, 91 Station, 109 svncliiiG T5 Valley. 10, 11, 33, 42, 44, 51. 53, 61, 62, 69, 70, 73, 76, 82, 83, 102, 103, 105, 114 Vichy Springs, 91, 92 National Perlite Company, 94 Research Council, cited, 31 Nelson, J.M., owner Cordelia quarry, 107 Neohipparion gidleyi, 46 Neroly formation, 15, 42, 43, 44, 49, 60, 61, 72, 81 post-, 61 Nevada, 25 anticline. 72 Nevadan orogeny, 19, 20 -Coast Range region, 20 Newberry, J.S.. cited, 13 Nicasio, 17, 86 anticline, 72 North America, 3, 78 mine, 89 Norton, R.R., owner Kohler and Chase deposit, 84 130 INDEX Novate, 1)0 conjjlomcrntc. (>7, ]()"> Crock, 114 Nuns Canyon, N't, 112 O'Connor pits, 10r» Oakville,97, lOr., Ill area, 101.102 i\()^ i";?: ..-. . .. 'S> • district. 101 mine. 102 sync-line. 73 Otema Creek, 114 Oleum, 52, GO Oligocene epoch, 36, 68. 79, 80 sandstone. 40 Onsrud Construction Company, 104, 110 pit, 105 Oregon, 16, 19, 20. 26, 36, 80 ■ Orinda formation, 46, 47, 49 r.y, "• ■ Osmout, Vance, cited. 14, 48, 63 .IC: ,n:., Ostrea hourgeoisii, 37 ;4i-hq?? mir.lf ;;(*• ilh-^' lurida, 52 t^V ,;;^^ Oursan Ridge, 38 (>ii. > ■'• sandstone, 15, 38, 72 Oxfordian, 19. 20 middle, 19 Pacheco Creek, 114 Road, 32 Pacific Coast Aggregate, 106 Ocean, 8, 10, 11, 25, 56, 78 , T <»' Portland Cement Company, 106 Palache, Charles, cited, 13 Paleocene epoch. 20, 27, 31, 34, 52, 71 , 74, 78, 79, 81, 94 lower. 79 Paleozoic era, 76. 89 Palmer, C.E.. 104, 110 pit, 110 Pankost, lessee Walker pumice pit, 97 Panoche formation, 93 -Vj" .i""- J-Of ,'. ■ q'-'A Parish Brothers, 104, 106 Paskenta formation, 21, 22, 23, 24, 25, 26, 93 ; stratigraphic section of, 23, 24 Pearl, Frederica A., owner Cicero pumice pit and Pearl pnmice pit, 96. 97 \ pumice pit, 95 Pecien (Aerjuipecten) latiauratus Conrad, 52 Pengrove. 44, 45, 72 Perkins, J. Hayden, 101 Petaluma, 14, 45, 48, 60, 62, 67, 82, 83, 86, 87, 90, 92, 94, 98, 104, 105, 107 area. 93, 94, 104 Bay, 25 i^.. Creek, 114 formation, 44, 45, 46, 54, 60, 62, 63, 67, 68, 73, 81, 94 Hill, 108 pre-. 60 quadrangle, 12, 14, 19, 33, 44, 45, .48, 50, 57, 58, 60, 63, 72, 75, 81, 95, 114 Rock quarry, 107 Valley, 10, 11, 16, 17, 19, 25, 44, 45, 48, 53, 58, 61, 66, 67, 72, 75, 80, 81, 82, 90 I'hi/lloceras, 24 knoxvillensis, 26 Pinole. 38, 47, 60, 72, 87 fault. 72 Point. 47, 52 tuff. 38, 43, 46, 47. 49, 55, 60, 61, 72, 73 Valley. 38, 60 Pit fir hehri.42 stalderi, 42 ' - '■ INDEX 131 Pittock, Richard, losspo Ooi-lxn-din;; (Hiai-i-.v, 112 Pittsbui-fih, .T), rA, ;»."., 105 .• • r I'umice Industries, owium- Alvcriia/ pit, !)(> Pleasants Valley, 33, 34, 35. (i.j, 7!) Pleistocene epoch, 35, 3S, 43. 51 , 52, 53, 65, 66, 82 formations, 50, 63 ' «, . ^ middle, 51,53 -'?•.►}■■ terrace deposits, 49 ; pre-, 50, 65 upper, 52 Pliocene epoch, 14. 16, 35. 44, 46, 49, 50, 51, 52, 55. 60, 65, 66, 67, 68, 70, 74. 75, 76, 81, 82, 93. 94, 100 lower. 47, 60, 63, 81 middle, 47, 61, 65, 81 upper, 65, 81, 100 volcanics, 44, 62, 104 Point Reyes. 10. 14. 56, 57^ 105 blocli, 6( Hill, 16 Peninsula. 39, 40. 53. 54. 55. 56, 62, 66, 67, 72, 76, 80, 82, 83. 114 quadranjjle. 11, 12, 14, 16, 19, 33 37, 48, 50, 53, 57, 58, 66, 75, 114 Station. 16. 51, 66, 89, 104, 105, 109 Port Chicago, 49 Costa, 84, 85 Brick Works, 85 Portlandian, lower, 19 middle. 19 Potrero Hills. 10, 14, 32, 33, 35, 43. 48, 49, 53, 54, 74, 85, 92, 93 anticline, 33, 34, 35, 74, 93 gas field, 93 Potter pit, 105 Priscofusus caudata, 32 Putah Creek, 22, 23, 25. 27. 28, 49, 70, 114 Canyon, 24, 27, 29 road, 25 Putnam Peak, 35, 65 Basalt, 55, 65 Quaternary formations, 50 period. 45. 06, 74, 75, 82. 83. 84 Quinlau, C.M.K., owner of perlite deposit, 95 . Radiolarian chert, 17 Rainbow quarry. 104, 112 Ransome. F. lieslie, cited, 13 Recent epoch, 14, 53, 54 Rector Canyon. 62 Reed. R.D., cited, 25 Reidenbock, ]M.I>., owner Juarez quarry, 109 Reservoir syncliue, 74 Retlaff, A.R., owner of a hot springs resort. 92 Rice, lessee AValker pumice pit, 97 Richey, K.A., cited, 47 Richfield Oil Company, Potrero 1 , 93 Richter property, 87 Rincon Valley, 75 Rochester Oil Company, 92, 93 Rodeo, 42. 43, 60. 83 anticline, .38. 73 Creek, 39. 114 ^-. , anticline. (3 shale. 15, .38, .39 syncline. 73 Roderick pit. Ill , W.M.. 104, 111 Rogers Creek. 68 fault, 68 , George, owner Murray Ranch coal deposit, 86 132 INDEX Russia, 78 RussianHivor, S, n,S2, 114 Rutherford, tiJ), 8!», !M) anticline, 73 Sacramento River, 10, 53, 114 Valley, 8, 10, 11, 12, 20. 21, 25, 37, 49, 50. 53, 54, 66, 67, 77, 7!), SO, 81, 82 Sage Canyon, 50 St. Helena, 50, 51, 58, 62, 69, 91, 95, 105, 111 rhyolite, 51, 55, 01, 63, 65, 75, 82 John Mountain fault, 68, 69 quicksilver mine, 59, 60, 98, 99 Salinia, 25 Salmon Creek, 54. 114 San Andreas fault. 11, 19, 25. 56, 66, 67, 72, 76, 77, 80, 81, 83 Francisco, 31, 47, 87, 104 Bay, 8, 10. 11, 12, 14. 36, 40, 67, 79, 82, 83, 114 area, 13, 18, 63, 81 -Marin block. 66, 67, 68, 72, 75, 77, 78, 80, 81, 82, 83 Peninsula, 16, 47, 50, 66 quadrangle, 17, 38, 47 Joaquin Basin, 50 River, 10, 53, 114 Valley, 10, 19, 20, 28, 33, 36, 80, 92 Jose, 104 Mateo, 19 Pablo age, 80 Bay, 8, 10, 11, 12, 32, 38, 39, 40, 41, 43, 46, 47, 49, 50, 52, 53, 54, 60, 67, 71, 72, 73 75 83 114 formation, 15, 37, 39, 40, 41, 42, 43, 44, 47, 48, 60, 63, 65, 68, 73, 74 sea, 60, 81 syncline, 39 40, 60, 73, 74 Ramon Creek, 36 sandstone, 36, 37 Santa Cruz, 88 quadrangle, 17 Fe Railway, 32, 36, 41 Rosa, 44, 46, 48. 50, 51, 62, 63, 69, 83, 85, 86, 90, 91, 105, 108 Creek, 51, 62, 69, 104. 105, 110, 114 quadrangle, 11, 12, 33, 44, 46, 48, 51, 58, 61, 62, 63, 69, 72, 75. 95, 114 Valley, 66 Sarco Creek, 62, 70, 95 Scandia syncline, 74 Sears Point, 109 anticline, 75 Selby, 32, 71 Serres, J.P., 104, 111 pit. 111 Shasta series, 20, 21, 22, 24, 25, 26 Shell Oil Company, 45, 46, 93 Murphy, 1, 93 Lombie lA, 94 Sherman Island, 10 Shroyer Mountain, 17 syncline, 72 Siberia, 78 Sierra Nevada, 19, 20, 78, 81 Silva pumice pit, 97 , William, owner Silva pumice pit, 97 Siri, A.B., pit, 108 Sitenga, John, 112 Skinner graphite mine, 87 Small, E., cited, 87 Smith, H.V., 104, 111 pit, 111 INDEX 13.3 Sobrante ridge, 37 sandstone, 15, 37 Soda Creek, 70, 76 Canyon, 70, 89 fault, 70 Valley, 62 Springs fault, 76 Solano County, 8, 59, 92 diabase, 59 Solenhofen formation, 19 Sonoma, 51, 75, 87, 91, 105 County, 8, 10, 48, 81, 93, 94, 104 Creek, 51, 67, 69. 91, 92, 104, 105, 110, 111, 114 Mountain Road, 87 Mountains, 10, 11, 45, 61, 63, 66, 73. 75, 79, 94 quadrangle, 11, 12, 19, 21, 36, 37, 42, 44, 50, 58, 62, 63, 68, 69, 70, 73, 95 River, 83 svncline, 75 Valley, 10, 51, 53, 62, 82 volcanics, 43, 44, 45, 46, 47, 48, 50, 51, 60, 62, 63, 65, 66, 68, 69, 70, 71, 72, 73, 74, 75, 81, 82, 86, 87, 94, 95, 101, 103, 105, 106, 107 South Fork Mountain, 8 Southampton Bay, 71 fault, 32, 33, 71, 73 Southern Pacific Railroad, 42, 49, 71 Spaletta, J.C., owner Spaletta operation, 104, 110 Operation, 110 Spring Street, 111 Standard Oil Company of California, 85, 94 Honker Community Well lA, 94 Suisun Community, 3, 94 Portland Cement Company, 88, 89 Stanford University, 13 Stanton, T.W., cited, 13, 20 Steel Canyon, 22, 69 Stelling, Martin, Jr., 102 Steuben School, 108 Steueroceras, 24, 78 Stirton, R.A., cited, 47, 60 Stock, Chester, cited, 46 Stockton, 104 Stony Point pit, 105 Suisun, 13, 53, 92, 106, 110, 114 Bay, 8, 10, 11, 12, 21, 26, 27, 34, 35, 42, 53, 54, 70, 72, 74, 78, 83, 92, 94, 95, 114 gas field, 93, 94 Creek 114 Valley, 10, 22, 24, 57, 70, 106 "Suisun marble", 88 sand" 94 Sulphur Creek', 104, 105, 111 Springs andesite, 55, 59, 69 Mountain, 26, 54, 58, 59, 60, 68, 69, 98, 100, 105 Valley Creek, 114 fault, 68, 69 syncline, 71, 73 Summit mine, 101, 102 Sur series, 14, 16, 17, 18, 22, 25, 56, 76, 77 Suscol Creek, 33, 62 Swinney, CM., cited, 101 Taff, Joseph A., cited, 14 Taliaferro, N.L., cited, 14, 19, 57, 90 Tamalpais quadrangle, 17 Tancred Station, 33 134 INDEX Taylor, J. S., lessoo riorlicnlinK quarry. IIL* ■ 'iiii;T.i , Mountain. (>'2. l().s (lopi)sit. SO i!. ("oal .Mining,' Company. S(> i Tt'liania ('oiint\ . I'tl Tcjon lonnaf ion. '.\\. 35 Tonihlor formation, 40 Terrace Drive. TO!) ,. Tertiary deposits. .'>1. .">•">. .">.". ."»S period. 1.".. (i(i. (iT, OS, 72, 7."., 74. 77, S2, 92, 95 Ticeshale, 15. .-.s. 72 Valley. :?S Titauia quarry, 105 Tolay Creek, 44. 45. 0.",. 07. 75, 114 svnclino. 72 : ■ fault, do. 07. 0,s. 72. 75, 77, 80, SI, 82, 94 -Ilayward fault, OS Valley, 07 volcanics, 50. 00. 94 Tolenas. 53 "'■ '"' •'-- '^'- ■< . Spring.s. 100 '•' .■*<"*"'•/-'-. Tolman. F.B.. cited, 93 Tomales Bay. S, 10, 11, 16, 17, 25, 39, 48, 51, 52, 53, 56, 62, 66, 67, 72, S3, 88, 89, 90, 114 Bluff. 50 ;■ Tom's Point, 52 .*'T / ' Tooby, E.N., SS 'n ! -4-01 nr' Trask, P.D., cited. 10, 40 Triassic period, 70 Trico Gas and Oil Company. 92, 93 Petaluma Community 5 No. 2, 94 Well. 94 <-■- .'' ,-?-«:r:Jiraa:oJ i-r>>;:: -; Trinity Road, 95, 112 fi'i .iJ ai'aqin: — - •■■ Trout Farm, 89 Tulucay Creek, 109 Turritt'Uu jtnchecoensis, 32 infraffratiulata, 32 nrasdua aedificata, 34 Twin Sisters Peaks, 71 Tyon group, 20 • I^altis Creek, 33, 114 U.S. Arsenal, 32 Geological Survey, 12, 13 • ; i-1 . . ■ ' , cited, 31 ' Jo ,7~. ■;«-."■ - ' - ■• Vaca Mountains, 8, 10, 11, 22, 23, 24, 26, 27, 28, 29, 53, 56, 70, 74, 82, 83, 93, 106 block, 66 - quadrangle, 21 Valley, 10, 33. 34, 35, 65, 79, 92 Vacaville, 10, 33, 48, 49, 65, 85 Hills, 10, 42, 43, 48. 49, 66 quadrangle, 10, 12, 35, §7, 48, 49, 79 ..- Valanginian, 78 Vallejo, 33, 85, 91 ^-. :...•■•; syncline,73 Valley of the Moon quarry. 104, 112, 113 Vancouver Island, 26 Veeder Mountain, 11, 62, 63 . syncline, 73 Venericardia, 27 Venerupis (Protothaca) stamineaGahh, 52 Ver Planck, William E., Jr., cited, 84 Verde Canyon syucline, 72 I INDEX 135 Vierra, lessee Alvernaz pit, 96 Vonson, M., owner of a manganese niino, 00 Waldrue Heights syncline, 75 ^Yalkel• Creek, 52, 54. 114 anticline, 72 , D.C., owner Walker pumice pit, 97 pumice pit, 95, 97 Walnut Creek, 37, 38 Waring. G.A., cited, 91 Warm Si)rings, 91 Washington. 35, 36, 80 University of, 12 Washoe Creek anticline, 72 Watts, W.L., cited, 88. 106, 107 Weaver, Charles E., cited, 13, 99 , E.M.. owner Taylor Mountain deposit. 86 W^eeks, R.B., 90 Weise. J.H., owner of kaolin deposit, 85 Weldon Canyon, 27 Western Cenozoic Subcommittee, cited, 31 White Sulphur Springs, 91 Whitney. J.D., cited, 13, 20 Wild Horse syncline, 76 Wildcat Ranch anticline, 72 Wilder, A., 97 Williams pit, 105 Willow Pass, 96 Wilson pumice pit, 95 ~ , T.D., owner Wilson pumice pit, 97 Wilson's Ranch, 48, 50 Wing Canyon anticline, 73 Winters, 10, 48 W^olfskill formation, 43, 48, 49, 53, 61, 65, 72, 105 pre-, 61 Station, 48 Wooden Valley, 57. 58, 61, 62, 70. 71, 72. 100 anticline, 74 fault, 70, 71 syncline, 74 W^ragg Canyon, 22, 24, 25. 70 fault, 70, 74 Wright, O., 97 W^robel, L.J., 104, 110 pit, 110, 111 Yolo County, 8, 33 Toungman. William, 112 Tountville, 76, 98, 103, 104 Zameroni pit, 105 7173 4-49 2M THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW BOOKS REQUESTED BY ANOTHER BORROWER ARE SUBJECT TO IMMEDIATE RECALL j= FEB 13 1996 RODEIVi!^ MAR 1 9 1996 PHYSICAL SCS.UBRAHY FfB0 9 m D PE3 ^ 1SB8 Physic^ ^^^^^'^' Zfj LIBRARY, UNIVERSITY OF CALIFORNIA, DAVIS D4613(7/92)M f ^ 'VT . V^e. ■>. ^ VJ iw^C - PHYSICAL SCIENCES LIBRARY A5 yaiVERSITY OF CAUFQUftft PAVXS e?418 ^1^^ PS Si