C3 A3 CALIFORNIA DIVISION OF MINES BULLETIN 172 Jtai An^elu Counif^ Qcdi^o^mia 1958 / UBRAR-Y STATE OF CALIFORNIA GOODWIN I. KNIGHT, Governor DEPARTMENT OF NATURAL RESOURCES DEWITT NELSON. Director DIVISION OF MINES FERRY BUILDING. SAN FRANCISCO 11 OLAF P. JENKINS, Chief SAN FRANCISCO BULLETIN 172 FEBRUARY 1958 GEOLOGY AND MINERAL DEPOSITS OF SAN FERNANDO QUADRANGLE LOS ANGELES COUNTY, CALIFORNIA BY GORDON B. OAKESHOTT Price $3.75 UBRARY UMIVERSITY OF CALIFORNIA DAVIS CONTENTS Page 1,1'tli'i- iif (liinsinittnl 7 Alistract i> Iiitroduction W CiMicraphy 12 Topojjriiiih.v and culture 12 Climate Ifi Water resources 16 Soils 17^ Vecetiition 18 Descriptive geolocy 19 Siimmnry of rock formations anil stniotiiral fealiues 19 Intrusive aiul metamorphic rocks 21 Mendeiiliall j;iieiss 21 Aiuirtliosite-fialihro rocks in the San Fernando and TnjunKa Ifi-minute quadrangles 2!) IVlona schist 49 Plaeerita series 50 Diorite gneiss 52 Syenite and hornblende diorite 53 Crancxliorite 54 (Jninite 5j> Granite peRmatite and aplite 56 Tertiary and Quaternary sedimentary and volcanic rocks — 57 Intrdduction 57 Martinez formation 57 DomeuKiiie formation and subsurface Eocene units 58 Vasquez formation 59 Tick Canyon formation 63 Topanga ( ?) formation 63 Mint Canyon formation 65 Modelo formation 69 Pliocene and lower Pleistocene geologic units 74 Repetto formation 75 Pico formation 78 Saugns formation 83 Pacoima formation 8/5 Terrace deposits 87 Landslides 88 Recent alluvium 88 Stnictural history of the Cenozoic era 89 Faulting 89 San (ialiriel fault zone 89 Sierra Madre fault zone 92 Whitney fault 94 Mission Hills faults 94 Pacoima Hills fault 94 Faults north of San flabriel fault zone 95 Folding 100 Soledad basin folds.. 1 lOO Folds of the San Gabriel fault zone and Placerita area__ 101 Folds of the San Fernando basin and margins 101 Summary of historical geology and geomorphogeny 103 Pre-Cambrian 103 Later pre-Tertiary 103 Tertiary 104 Quaternary 105 Economic geology 105 Geologic occurrence of mineral deposits 105 Metals 108 Antimony 108 Chromium 108 Cobalt 108 Copper 108 Gold 108 Lead-silver-zinc 109 Molybdenum 109 Titanium 109 Uranium and thorium 110 ( Pape Miscellaueoiis iionmelallic minerals HO Aslieslos ]10 Bituminous sandstone HI Itorates m ('lial<-ei and other j;eoh>j;i(' i|ii:i(lr:iii^'li's of llie area recently published h.v the Divi- sion of .Mines 10 (leiiei-alized fiOoIoKit* <*oIunin south of San (laliriel fault 22 (leneraliziMl ;;eohi;;ie <'(ilunni north of San (laliriel fault 2;! Sketch of iiuartzo-feldspathic srnnulite from Mendenhall gneiss ._ 2^ Skelcli of h.viiersthene (luartzo-feldspathic grnniilite from Mendenhall gneiss • 2." riioloniieroKraiih of nntiperthitic feldspar in Mendenhall gneiss 25 I'hotoniieroKraph of antiperthitic feldspar in Mendenhall KUeiss 28 I'liotoniioroKraph of antiperthitic feldspar in Mendenhall j,'ueiss 2S lMiotonii<'ro;;rai)li of Meuih'uhall gneiss from Pacoima- Santa Clara divide on IJttle Tujunga road 28 (leologie ni:iii of anortluisite-gabhro rocks in San Fernando and Tujnuga l.~t-niiunte quadrangles v?0 I'hase-rule diagram for plagioclase 34 Differential therunil aual.vses curves of anorthosite samples :t4 .1. Skelcli showing pyroxene replaced liy filirous aggregate of aiiligorite and chlorite, in titauomagnetite rock. /{, Sketch showing intergrowtli of ijmenite, developed par- allel to crystal directions in magnetite l?8 .1. Sketch showing altered apatite-ilmenite-magnetite py- roxeuite. /{, Sketch of olivine galiliro 4(1 I'liotomicrograph of litanoniagetile olivine gahbro 42 I'hotomicrograph of hornlileude titauomagnetite gabbro from I'acoima Canyou near Xorth Fork 43 I'^ield sketch showing intrusive <'lili(|ue ai'rial view northeast across Soledad basin to Sierra I'elona 14 •"i. \'iew northwest from Santa Clara truck trail into Bear Canyon l."i (1. I'auoraniic view north toward western San Gabriel Moun- tains from Hill Kose Street in Tu.junga l."i 7. View from upiier Kagel Canyon into Limerock (^anyou ITi 5. Meudenhall blue quartz gneiss in Hear Canyon 21 II. .Mendenhall blue quartz gneiss on Little Tujunga road 24 10. Meudenhall lilue (|uartz gneiss on Little Tu.junga mad 24 11. .Vnorthosite in Soledad Canyon 2!l 12. .Viiortbosite in Soledad Canyon 31 Kl. .Viiortliosile in Soledad (^an.von 31 14. .Vuorthosite in North Fork I'acoima Can.von 3."> l."i. (lahbro-norite in Hear Canyon 3r> 1(5. (labbro-uorite in He;ir Canyon 3."i Photo Page 17. Handed chloritized gabbro, gray anortliosite-gabbro, and white anorthosite, on truck trail south of Mt. (!leason__ 'Mi IS. .Vnortliosite, pyroxenite, and gabbro-norite in Xorth Fork I'acoima Canyon 36 1!). View north toward Dagger Flat in Pacoimn Canyon 3(J 2(1. .\iiortliosite and metagabbroic rooks, Soledad Canyon Road near Sulphur S|iriugs 37 21. Hands of gabbro-norite, gabbroic anorthosite, diorite, white anorthosite, and ilmeuite-maguetite rocks 38 22. Fractured anorthosite on road a mile below Monte C'risto .Mines, Tujunga iiuadrangle 39 23. S]iecimeii of (piartz-ilmenite-magnetitc chlorite schist in fracture zones in anorthosite, Mt. (Ileason quadrangle 43 24. Siiecimen of pegmatitic hornblende gabbro from near Mt, (Ileason 44 2."!. Anorthosite cut by metapyroxenite stringers in Soledad Canyon 4C 2(i. Anorthosite cut by pvroxenite (?) and metagabbroic stringers 40 27. Dark metagabbroic rock or metapyroxenite injected in frac- tured anorthosite, Soledad Can.\"on 40 25. Dark inclusions of metagabbroic rocks in anorthosite, Sole- dad Canyon west of .\gua Dulce 47 2!l. Hlock of anorthosite in gabbro-norite, I'acoima Canyou 47 '.'•(>. Hlock of anorthosite in gabbro-norite, I'acoima Can.von 47 31. I'od of anorthosite in gabbroic rock. Lower Iron Can.von _ 48 32. Dike of anorthosite in banded gabbroic rock.s. Dagger Flat Canyon ' 4S 33. Peloua schist in Hon(|net Can.von ."lO 34. Siieciineu of graphite schist from ridge west of Limerock Canyon .">1 :{.">. Jligmatites of granite-injected quartz diorite gneiss. Little Tujunga Road in Brick Canyou ~t'2 ."!(!. .Migmatized iinartz diorite gneiss, Little Tujunga Road at Hiick Canyon 52 ."■7. Migmatite in Buck Can.von 52 38. (iraiKidioifite intruding anorthosite, -■Vngeles Forest High- way, 'yujuuga quadrangle .">4 ■3!). Dikes, sills, and irregular injections in anorthosite at con- tact of grauodiorite, .\ugeles Forest Highway, Tujunga (piadr.ingle 50 4(1. Va.squez formation at Vasquez Rocks, upper .\gua Dulce Canyon 59 41. Vasquez Kocks 59 42. Sandstone and conglomerate beds of Vasquez formjition (30 43. Sandstone and conglomerate beds of Va.stiuez formation (5(1 44. A'asquez fanglomerate beds in Hoiupiet Canyon (id 45. Vasquez fanghimerate beds in HoiKiuet Canyon (id 4(>. Vasquez fanglomerate in Bouquet Canyou (i2 47. A'as<|uez formation in Texas Canyon 02 4S. Jlint Canyon and Va.squez formations from I'uckett Mesa 65 49. Mint Canyon formation in Sand Canyon 00 ~tO. .Mint Canyou formation in lower Hear Canyon 60 51. Mint Canyon formation on .Sand Can.von Road 66 •52. ilint Canyou from Sand Canyon Road 67 .53. Mint Canyou formation at Solamint (!7 .54. Puckett Mesa 68 .55. Diatomaceous shale in Modelo formation 69 50. Modelo .shale at San Fernando re-servoir dam 70 57. Reiietto formation on Little Tujunga Road 75 .58. Repetto formation on Sepulveda Boulevard 7(i .59. Repetto formation on Little Tujunga Road 76 (id. Klsuiere member of the Riqietto formation __ 77 61. Repetto formation and Jlodelo shale 78 62. Sunshine Ranch member of the Pico formation at San Fer- nando reservoir 82 (4) CONTENTS— Continued (it. ti.'i. (iii. t>7. <;s. ti!). 70. iito Page Siiiisliinc RiiiK'h member of the Pico formation at San Fer- nane.Mille and San Cabriel faults 91 Klippe (if Placerita rocks thrust over Repetto formation, Sylniar 02 Hospital-Lopez fault zones 92 Quaternary gravel and Saugus formation along Lopez fault 9.S Repetto formation thrust over Pico formation 04 Photo Page 76. Fault contact between Pico and Modelo formations 94 77. Soledad fault, Soledad Canyon 95 78. Anorthosite and gabbro, Soledad Canyon 95 70. Fault contact, Vasquez formation and granite 96 80. Pole Canyon fault, from Soledad Canyon 97 81. Humphreys syndine in Keyuier Canyon 101 82. Anticline in Modelo .shale, Sepulveda Boulevard 102 8S. Modelo formation, Wentworth and Foothill Blvds 102 84. Hanson dam 114 85. Tnjunga Wash and Hanson dam 115 80. Plant of Sierra Pelona Rock Company 116 87. Plant of Sierra Pelona Rock Conii)any 116 88. MacArthur ready-mi.x plant, Soledad Canyon 117 89. Gravel deposits in Tujunga Wash 118 !HX Gravel plant of City Rock Company 118 91. Gravel plant of City Rock Company 118 (5) Fron-tisi-ieck. Di.rU p.-o-fambrim. MoiHlrnhall ^-noiss faulted a^-ainst lisht Cri'taceous (?) srano.liorite <.n l.ranrh of San^ Gabriel fault. Width of exposure is about 25 feet. Off Little Tujunsa Koail iu I'acoiina Caiivon at locality showing- :le reports which are based on geoloji:ic mappint; — scale one inch equals one mile — of areas which are significant for their mineral resources or potential. The author, Gordon B. Oakeshott, carried on the long-time field and laboratory studies of this part of the San Gabriel Mountains in addition to his duties as Deputy Chief, Division of Mines. San Fernando quadrangle, because of its complex geologic history and diver- sity of rock formations, has produced a large number of mineral commodities. Cumulative mineral production from the quadrangle, to the end of If)"):!, is estimated at $r)l,000,UOO. Petroleum, principally from Placerita oil field, ac- counts for 84 percent of this; rock products, 9 percent; borates from Lang (Sterling) mine, 6 percent; and gold and minor amounts of titanium ore, about 1 percent. The region has an important potential for mineral production, par- ticularly as it lies within a few miles of the great Los Angeles metropolitan area. Respectfully submitted, DeWitt Nelson, Director Department of Natural Resources November 25, 1958 (T) GEOLOGY AND MINERAL DEPOSITS OF SAN FERNANDO QUADRANGLE, LOS ANGELES COUNTY, CALIFORNIA Including Anorthosite-Gabbro Rocks in San Fernando and Tujunga Fifteen-Minute Quadrangles By (JoRDON H. Oakeshott ♦ ABSTRACT San Fernando (luadrantrle, latitude 34° 15' to 34°30' N., longitude n8°ir)' to 118°30' W., includes approxi- mately 245 s(|uare miles of the western end of tlie San Gahriel Mountains in Los Aufjeles County. The east- eentral part of the quadranprle — the western end of the pre-Tertiary erystalline massif of the San Oahriel Moun- tains — is an area of ru^jfred topography and higli relief topped by Magie Mountain, elevation 4,878. Pre-Cambrian rocks include the Mendenhall gneiss (new name) and the anorthosite-gabbro group wliieh in- trudes the gneiss. The pre-Cainbrian rocks crop out over an area of 91 scpiare miles north of the San Gabriel fault. Tliree groujis of rocks of undetermined age represent time between late pre-Cambrian and early Cretaceous. They are the Peloua schist. Placerita formation, and diorite gneiss. The Peloua schist is found only north of the San Gabriel fault ; the Placerita formation only south of that fault. All three units have been intruded by gran- odiorite, (piartz monzonite, and granite which collectively crop out over 33 square miles of the quadrangle. Syenite crops out in the northeastern corner of the quadrangle. The granitic rocks are probable correlatives of similar plutouic rocks of Upper Jurassic (?) and Lower Cre- taceous (?) age elsewhere in the Transverse and Penin- sular Ranges, the Mojave Desert, and southern Sierra Nevada. Tertiary and Quaternary sedimentary and volcanic rocks, flanking the central crystalline-rock mass, were deposited in two principal basins : the Soledad basin northeast of the San Gabriel fault, and the San Fer- nando basin southwest of the fault. Slivers of Paleoeene marine .sedimentary rocks of the Martinez formation are along the San Gabriel fault. Marine beds of the Me- ganos, Capay, and Domeugine stages of late Paleoeene to middle Eocene age are present in the Elsmere Canyon- Placerita area, south of the San Gabriel fault. In the Soledad basin, late Eocene to late Miocene time is repre- sented by nearly 14,000 feet of nonmarine and volcanic rocks of the Vas(|uez, Tick Canyon, and Mint Canyon formations. Remnants of the continental and near-shore middle ( ?) Miocene Topanga formation are found in the San Fernando basin. The marine middle to upper Mio- cene Modelo formation is thickest in Little Tu.iuuga syncline in the San Fernando basin but also is present in the western part of the Soledad basin. Lower Pliocene marine beds of the Repetto formation are found aroiuid the south, west, and northwest margins of the erystalline rocks ; the marine upper Pliocene Pico formation is less extensive. The nonmarine upper Pliocene Sunshine Ranch member of the Pico formation is present in both basins, but reaches its maximum thickness at San Fer- nando Reservoir. The continental lower Pleistocene Saugus formation is very widely distributed, both north • Deputy Chief, California State Division of Mines. Manuscript sub- mitted for publication December 1957. and south of the San (iabricl fault. This formation is overlain unconformabjy by fanglomcrates of the Pacoima formation (new name) and b.v late Quaternary terrace deposits. Structural fcat\ires of San Fernando (luadrangle are dominated by the right lateral San Gabriel fault, wliich extends ol)li(piely across the western San Gabriel moun- tains. North of tiiat fault, the pattern comprises the normal east-trending Soledad fault and a group of left lateral northeast-trending faults. The Sierra I\Iadre fault zone is a series of discontinuous, east-trending, north-di])ping reverse faults along the northern margin of San Fernando Valley. The most prominent fold struc- ture of Soledad basin is the northeast-striking, west- plunging Soledad basin .syncline. The east-striking Little Tujunga syncline is the dominant fold of San Fernando basin. The complex geologic history and diversity of rock formations of San Fernando <|uadrangle are reflected in the large number of mineral commodities present there. In San Fernando quadrangle 25 of California's 78 mineral commodities have been found and 11 of them have been produced in significant amounts. Cumulative mineral production from the (piadrangle, to the end of 1953, is estimated at $51,000,000. Petroleum, principally from Placerita oil field, accounts for $43,000,000, or 84 percent of this ; rock products, nearly $5,000,000 or 9 percent ; borates, from the Lang or Sterling mine, $3,000,000 or 6 percent ; and gold and minor amounts of titanium ore, about 1 percent. The pre-Canibrian anorthosite-gabbro rocks have yielded several mineral products and are a potential source of others. Anorthosite, nearly pure soda-lime feld- spar about 27 percent alumina, is a potential source of aluminum ; it has been quarried for use as an abrasive and for poultry grits, and has been successfully tested for pozzolanic concrete. Titaniferous magnetite, in these rocks, has been jiroduced in small amounts for titanium oxide pigment, use in heavy rollers, and for roofing gran- ules. Titaniferous magnetite in the western San Ga- briel mountains is the major California occurrence of ilmenite. The high phosphate content of some of the apatite-rich pyroxenites and norites may eventually be of economic interest. Some of the pre-Cambrian pegma- tites contain snuill proportions of the rare minerals of uranium and thorium. Crystalline limestone, dolomite, and graphite have been obtained from the Placerita formation. Fractured schist and gneiss of this formation are the reservoir for light oil in the Schist area of Placerita Canyon. Granitic rocks of Lower Cretaceous ( ?) age have been used for granite blocks and facing, crushed stone for roads, and decomposed granite for road-base material. Mineraliza- tion in the late jiegmatitic and hydrothermal stages of granitic intrusion has developed the pegmatites, which (9) 10 California Division of Mines [Bull. 172 Fioi-KK 1. Index ninp of a part of southern California showing area covered by San Fernando, Tujunga, and other geologic quadrangles recently published by the Division of Mines. have been explored for (|uartz, feldspar, and mica ; and the quartz veins, whieh in some places carry sulfides and gold. Cenozoic sedimentary formations have yielded the most valuable mineral products in the iiuadrantrle. The late Eocene ( '!) to early Miocene ( ?) Vasqiiez forma- tion contains interbedded borates, which were mined for many years in Tick Canyon, and minor g:ypsum beds. Glassy tuff of the upper Pliocene Mint Canyon formation has been utilized as chinchilla dust and for roofing. Dia- tomaccous shale of the upper Miocene marine Modelo formation has been sold for an insecticide carrier. Sand- stone of the lower Pliocene marine Uepctto formation is the principal reservoir rock for i)etroleiun in the IMaccr- ita oil field ; upper Pliocene marine Pico sandstone and some of the upper Pliocene nonmarine Sunshine Ranch sandstone are also oil-saturated. Eocene beds in the Whitney Canyon field formerly yielded some high-grav- ity oil. The greatest value of Quaternary alluvial sand and gravel of San Fernando Valley and the Santa Clara River has been as a source of sand, gravel, and crushed stone for concrete aggregate; stone production has been second in value only to petroleum in tlie quadrangle. Minor amounts of placer gold and titaniferous magnetite have been derived from the gravels. The placer gold discovery site of 1842 is now marked by a monument in the state park in Placerita Canyon. INTRODUCTION Location. The San Gabriel Mountain range, one of tlic prominent Transverse Ranges of southern California, comprising an area of over a thousand square miles, is a high, rugged lens-shaped mountainous area extend- ing from Newhall Pass eastward about 60 miles to Cajon Pass. Its maxinnun width of about 25 miles is in the central part of the range. San Fernando quadrangle. 19581 San Fernando Quadrangle — Oakesiiott 11 latitude 34°15' to 34°30' N., loiifjitude llS^lf)' to 118°30' W., includes approximately 245 square miles of the western end of the San Gabriel Mountains. The northern part of the quadrangle extends across Soledad Canyon to the southern margins of the Sierra Pelona. The southwestern part of the quadrangle includes the city of San Fernando and part of San Fernando Valley ; in the southeast are the towns of Sunland and Tujunga and part of the Verdugo Mountains. Los Angeles city hall is about 13 miles due south of the southeast corner of the quadrangle. Field Work and Maps. Field mapping was started in the fall of 1931 and was carried on intermittently until 1936 when the writer received the doctor's degree on a thesis based on the geology of part of the quad- rangle, flapping of the quadrangle was continued on an irregular basis during 1939-41, was interrupted by World War II, and carried on to completion during 1945-52. Geologic map, economic map, and sections, with- out text, were published by the Division of Mines in 1954. The base used for the earliest mapping was aerial photographs by Fairehild Aerial Surveys, Inc. on an approximate scale of 1 inch equals 1,500 feet, supple- mented by the incomplete 1:24,000 6-minute topographic maps issued by the Los Angeles County Surveyor. Later, complete photo coverage, scale 1:24,000, was ob- tained from the United States Department of Agricul- ture and the 6-minute series of 1:24,000 topographic maps was completed by the United States Geological Survey in cooperation with Los Angeles County. The geologic map (pi. 1) was drafted on a base constructed from a compilation of the latest 6-minute sheets availa- ble in 1954 (see index to 6-minute quadrangles, south- west corner pis. 1 and 2) ; 200-foot contours were drafted from these sheets to make the topographic base. Acknowledgments. During a project covering as long a period as this, a writer receives the advice and help of man}' geologists. I would like to remember gratefully the encouragement given by A. 0. Woodford and Thomas Clements in starting the project, and supervi- sion by the latter during field and laboratory work for the doctor's thesis. Olaf P. Jenkins published a synopsis of the thesis, secured the financial assistance of the California Division of Mines, and has contributed con- stant encouragement and help for the past many years. Thomas E. Gay Jr. made a complete field check of the economic mineral deposits and furnished data for the tabulated list. Charles W. Jennings field-checked well locations. Others of my colleagues on the geological staff of the Division of Mines who have been particularly helpful are Oliver E. Bowen Jr., Charles W. Chester- man, Richard A. Crippen Jr., J. Grant Goodwin, Salem J. Rice, and Lauren A. Wright. Hoyt Rodney Gale determined many of the Pliocene fossils; Leo Hertlein examined others. The late Chester Stock determined vertebrate fossils. The help of several micropaleontologists of the oil companies in studying collections of foraminifera is appreciated. The oil com- panies were also most helpful in releasing well data. C. C. Church, Otto Hackel, Richard H. Jahns, George J. Neuerburg, and L. A. Norman are among those who have contributed through helpful correspondence or field discussions. A grant from the Penrose Bequest of the Geological Society of America (No. 490-46) was of great assistance in obtaining thin sections for study of the pre-Cambrian rocks. Prcrioits Work. The San Gabriel Mountains received brief mention in the geologic literature more than 100 years ago, but the first important contribution to their geology did not come until nearly 70 years later. Trask (1855), Marcou (1855), and Blake (1857) made brief mention of the range in exploration reports. Whitney (1865), in his first volume on the geology of California, discussed relationships between the granite and sedimen- tary series. Hershey (1902 a, b, c, d, and 1912) pub- lished several very interesting papers on the area in which he suggested some formation names which are still in use. Arnold and Strong (1905) described a group of crystalline-rock specimens found north of Pasadena. Mendenhall (1908a,b) made some observations concern- ing faults in the San Gabriel and San Bernardino Mountains, and R. T. Hill (1920, 1928, 1930) discussed faulting in southern California, including the San Gab- riel Mountains. The modern era of geologic study of the western San Gabriel Mountains, and the first geologic map (scale 1 :62,500) of San Fernando quadrangle began with Kew's (1924a) well-known bulletin on the Geology and Oil Resuurces of Part of Los Angeles and Ventura Coi(nfie.ni Mt. Oleasim tnicli trail east of Ma^ic Monntain. White anorthosite in forecronnd. Plioto hij CInnles W. Chen- ternian. vensity of California at Los Anoplps, University of South- ern California, and Pomona College. Work by Jahns and his students, beoinning with his paper in 1940, has greatly increased knowledge of the complex stratigraphy and structure of the Soledad basin. Among the most significant unpublished theses which deserve special mention are tho.se by Daviess (1942), H. S. Hill (1939), Irwin (1950), Menard (1947), Muehlberger (1954), Sharp (19;u;) Wallace (1940), Wright (1943, 1951), and Wozab (1952). Many contributions to the geology of San Fernando quadrangle have been published since 1950. The writer has published short papers and abstracts from time to time, indicating progress in w^ork on the quadrangle (Oakeshott, 1950a,b; 1951a,b,c; 1952; 1954a,b), and also published a preliminary edition of the geologic map and economic map and sections accompanying this bulletin in 1954. Crowell (1952) has offered evidence of major right-lateral movement on the San Gabriel fault, leading to better understanding of this important fault zone. Higgs (1954a) contributed a detailed study of the anorthosite and related rocks and Neuerberg and Gott- fried (1954) proved their pre-Cambrian age by lead alpha studies on zircon. California Division of Mines (1954) Bulletin 170, Geology of Southern California, in- cludes 24 papers dealing wholly or in part with geolog- ical features of San Fernando quadrangle. Many contributions to the geology of San Fernando quadrangle which are not mentioned in this section on Previous Work are discussed, more conveniently, in the sections where they apply. GEOGRAPHY Topography and Culture The east-central part of San Fernando quadrangle is the western end of the crystalline massif of the San Gabriel Mountains. It is an area of rugged topography and high relief bounded by faults. The highest peak is Magic Mountain, elevation 4,878 feet, at the center of this area. Magic Mountain tops an east-west ridge of rather low summit relief which is followed by the Santa Clara truck trail. Mendenhall Peak, elevation 4,582 feet, about 3 miles south of Magic Mountain, dominates the east-trending ridge followed by the Mt. Gleason truck trail. Between the two ridges Pacoima Creek flows west- ward, at elevation 2.700, in an extremely steep narrow canyon which turns sliarjily south to the San (fabriel Fault zone, follows it for about 1.] miles and then cuts due south acro.ss the ridge capped by Los Pinetos Look- out, elevation 3,570. Near the mouth of this last gorge Pacoima Dam (once the highest in the world) has formed a reservoir whose shoreline at capacity follows the 2,000- foot contour. Los Pinetos ridge forms a topographic high at the southwestern end of the San Gabriel Mountains. The Soledad basin, lying northwest of the San Gabriel crystalline massif, forms an area of lower relief and ele- vation, but still rugged topography, in Cenozoic sedi- mentar.y rocks. At the northern border of the quadrangle are the crystalline rocks of the mature surface of the Sierra Pelona. The Santa Clara River at the south border of Soledad basin has developed Soledad Canyon in the Soledad fault zone between the San Gabriel block and the basin. The Santa Clara River drains Soledad basin westward to the Ventura coast. Bou(inet Canyon, Mint Canyon, and Agua Dulce Canyon bring drainage south- ward by rather gentle gradients to the Santa Clara River. Sand Canyon, Pole Canyon, Bear Canyon, and Indian Creek, which drain the San Gabriel Mountains northward to the Santa Clara River, rise high in the mountains and have extremely steep gradients; all are marked by successions of falls in their middle reaches. South of the San Gabriel fault, the high block of crystalline rocks continues southeast-by-east of Los Pinetos Lookout across Little Tujunga Canyon to the southeast corner of the quadrangle where they reach an elevation of 4,220 feet. At the contact between crystal- line and sedimentary rocks, this ridge drops off very abruptly to the gentler slopes and lower elevations of the San Fernando Valley. Elevation of San Fernando is about 1,000 feet. Mission Hills, Pacoima Hills, and the western Verdugo Mountains form outliers a few hundred feet high. Principal drainage courses on the south side — Grapevine Canyon, Pacoima Wash, Lopez Canyon, Kagel Canyon, Little Tujunga Canyon, and Big Tujunga Can- yon — drain eventually to Los Angeles River which runs ■m. M^ I'liuii. i;. \ irw n(irllii'a.-.l fnuii U|i|h r lv:;;;il Canyon. Highest point on sliyline is Mendenliall renk, type locality of the pre- Canihrian Mendenhall gneiss; white ontcrops in miihlle ground are (^retaceous (?) granodiorite, seiiarated from gnei.ss l)y San (Jahriel fault which cuts through prominent saddle on skyline west of Mendenhall Peak. Saugns beds in foreground. I'liiito hij Charles W . Cheslerman. 1958] San Fernando Quadrangle— Oakeshott 13 14 California Division of Mines [Bull. 172 |Br W V. "Z V. '„ z: ? c u 5 S -r ^ ■ C 55 ^1 || I III ' y. . = .- 2 4- C 3 "5. S I ^ - — -*--. t) 0) u _ S :zj Ui CJ 2 ^ t^ 2 *o .2 c o t. ^ '*' >! X c c: a. o ~ .'z _ >» -r u y. > 0, rt M 73 o a: ■ x' J= ,4_, u £ ffi i e1 » ^ o x' o C tc OJ u /, 53 2 ^ U> S O S X t. >» 3 C b p. p. 3 .i ^ w _^ o^ > x ^ »; o X C5 X [S 6" a> :j o V o JZ -^ .H" .5 ^ >v "^ •"^ ^ £ c o -3 o - 0,' Z 5 •a- a; s - a; o >-^ £ rt H s o S [J X a X X c &I "ti g o §K aJ 19581 San Fernando Quadrangle — Oakeshott 15 I'HOTO ."). \'ipw northwest from Santa Clara truck trail across pre-Cambrian Meiidenliall gneiss and gabbro into Bear Canyon. Photo hy Chories IT. Vhfsfernian. eastward in San Fernando Valley. Pacoima and Big Tujunga Rivers head high in the San Gabriel Mountains and have cut tremendous canyons in their upper courses. Most of the ilraiiiage courses mentioned now have one or more dams to control runoflf, conserve water, and re- plenish ground water in the alluvial gravels. Hansen Dam and flood control basin receive water from Kagel, The earliest cultural development in San Fernando quadrangle centered around San Fernando Mission, founded in 1798, southwest of the present town. The Mission fathers began the establishment of agriculture, chiefly the raising of grapes, figs, olives, grain, and garden crops, and taught the natives farming nu'thods. Cattle, horse, and sheep raising were of prime importance on the large land grants until about 1850. Grain was the major agricultural commodity in the second half of the century. About 1905 subdivision was begun and by 1920 most of the large tracts in the valley had been divided into small farms. During this period of early subdivision, a rapid transition took place from grain and hay to fruit and garden crops; citrus fruits became important in the Sylmar to Sunland area. The Los Angeles Aqueduct, bringing water from Owens Valley, was completed about 1913 and shortly thereafter most of the San Fernando Valley, excepting the city of San Fernando, was brought within the corporate limits of the city of Los Angeles. In the past 20 years, urban development of San Fernando Valley has proceeded rapidly. Excellent highways have been developed in San Fer- nando Valley and across the mountains of San Fernando quadrangle, excepting only the areas of the high crystal- line-rock massif. Highway 99 and its complex feeders cross San Fernando Valle.y, and Foothill Boulevard joins this highway and all the valley towns along the I'HOTO 6. Panoramic view north of western San Gabriel Mountains from Hill Rose Street in Tujunga. Phofo by Mnry Hill, November 1950. Little Tujunga, and Big Tujunga canyons. The west shore of the Reservoir has been developed for Los An- geles City recreation. San Fernando Reservoir in the Mission Hills receives water from the Los Angeles City Aqueduct, which transports water from the Owens and Mono basins. The only thickly populated part of San Fernando quadrangle is San Fernando Valley. This part of San Fernando Valley is within the city limits of Los An- geles but includes San Fernando as a separate munic- ipality. San Fernando is on the main line of the Southern Pacific railroad and on Highway 99 between Los Angeles and Bakersfield. Sunland and Tujunga, in the southeast corner of the quadrangle, are on the low divide between Big Tujunga River and Verdugo Canyon. San Fernando Valley is a very rapidly growing residen- tial area and its towns, inehiding San Fernando, Pa- coima, Sylmar, and Olive View are swiftly merging into an urban area. Sunland and Tujunga already merge southeastward with the Los Angeles Metropolitan area. ,S r, ^»Wiif Photo 7. \'ii'w lidiii upinT KiikcI Cnn.von duwii mlci l.imerock Can.von (sharp notch at center). Low nearby brush-covered hills underlain by Pleistocene Saugus gravel; higher hills are Cre- taceous (?) granodiorite. Old graphite millsite on (birk hill right of center. Photo by Charles W. ('he.ilermaii. 16 California Division of Mines [Bull. 172 front of the raufre. Mint Canyon highway (U.S. 6) crosses the Placerita oil field and eonneets Los Angeles with the Mojave Desert. Good througli highways extend up Boiuiuet Canyon and across the quadrangle via Sole- dad Canyon. Little Tu.junga Road is a paved highway whieh crosses the western part of the erystalline massif to connect with the Sand Canyon Road, Soledad Canyon Road, and Highway 6 in Mint Canyon. The principal access roads to the central San Gabriel Mountains are the truck trails of the U.S. Forest Service, such as Santa Clara, Mt. Gleason, Pacoima Canyon, and others. They are good unsurfaeed mountain roads, but quickly become impassable in wet weather; they are locked off during the .seasons of high fire hazard. Poot- and horse-trails, which formerly criss-crossed the moun- tainous areas have not been maintained and are mostly overgrown by brush. Climate Climate of the Los Angeles region, including the area of San Fernando quadrangle at the western end of the San Gabriel Mountains, is classified as Mediterranean because of characteristically warm, dry summers and mild winters with moderate precipitation. The California coast receives most of its precipitation from moisture- laden air masses which bring air from the Pacific Ocean, most frequently during the winter season. In the south- ern California area, the moist northeastward-moving air masses are slowed and elevated by mountain barriers .such as the San Gabriel. This results in a local distribu- tion of rainfall which is closely adjusted to topography. Contours of equal rainfall in the San Gabriel Moun- tains are elongated east-west, parallel to the range (See fig. 4, Isohyetal map of the San Gabriel Mountains, Storey, 1948, p. 11). Average annual rainfall at Los Angeles is 15.22 inches, and at San Fernando (elevation 1,000 feet) is 16.77 inches. The 20-iuch isohyetal line extends eastward along the south front of the range across San Fernando quadrangle at about 1,400 feet elevation and the 24-inch line at elevations between 2,000 and .S,000 feet. Just south of the San Gabriel divide, above 4,000 feet, precipitation reaches approxi- mately 36 inches, some of it in the form of winter snow- fall. On the north .side, precipitation rapidly falls off in the rain shadow of the mountains. The 16-inch iso- hyetal line follows the Santa Clara River, and parts of tile Soiedatl basin appear to have an annual average I)recipitation of less than 12 inches. Newhall, elevation 1,200 feet, at the extreme western end of the range, averages between 16 and 17 inches. Experience at a num- ber of San Gabriel Mountains stations shows than even minor topographic features strongly influence local rain- fall (Storey, 1948, p. 11-12, and fig. 5). An isohyetal map of the San Gabriel Mountains for the flood- precipitation of February 27 to March 4, 1938 (Troxell, 1942, pi. 12, scale 1 ;2r)0,000) illustrates the effects of local relief and rainfall. San Fernando received 10 inches. Magic Mountain 22 inches, and Soledad Canyon 10 inches during this 6-day storm. About 75 percent of the annual rainfall total comes in the four winter months December to March ; 96 percent from October to April. Another characteristic of the semi-arid Mediterranean rainfall regime is extreme variability from year to year. Troxell and Hofmann (1954, p. 50iS ) have used the ob- served precipitation at Los Angeles as an example, show- ing a range in the 75-vear record from 5.59 inches in 1M98-99 to 38.18 inches {n 1883-84. They have also quoted studies of tree rings in southern California from about the year 1400 to 1950 to show tliat annual precipitation has been c.vclic; wet sequences have ranged from 4 to 24 years in length and dry sequences from 6 to 43 years. Temperature at low elevation in the western San (iabriel Mountains is warm in summer and mild in winter. Winter becomes colder and summer warmer as distance from the coast increases. For example, average temperature for the month of January is 53° F. at Los Angeles, 48° F. at Newhall; average temperature for August, the hottest month, is 69° F. at Los Angeles and 77° at Newhall. Mid-summer daily maxima in the Mint Canyon area are freipiently as high as 110° F. Tempera- ture decreases more or less in direct proportion to in- creased elevation. Summer days are quite pleasant above 4,000 feet and winter temperature is low enough so that snow is the normal form of precipitation above that level. The fact that the season of heaviest precipitation coincides with the time of lowest average temperature in this ilediterraneaii type of climate is of utmost impor- tance ill the effectiveness of moisture supply. Water Resources The principles expressed by Troxell and Ilofmann (1954) on hydrology of the Los Angeles region apply also to the more limited area of the western San Gabriel Mountains in San Fernando quadrangle. The areal dis- tribution of precipitation is extremely irregular because of the ditt'erenee in relief, and .seasonal and annual varia- tion in ]irecipitation reaches great extremes. Natural water loss, which includes the water used by the native vegetation, as well as water evaporated from leaves and land surface, accounts for the major part of the precipi- tation ; in some years, all of it. In the higher mountains natural water loss is least. Annual runoff' of the princii)al streams in San Fernando quadrangle is extremely vari- able. Seasonal runoff' for most of the streams varies from nothing in the latter part of the dry season to a maximum immediately after heavy rainfall. Average annual runoff" ranges from less than 0.25 of an inch on the valley floors to more than 20 inches in the high, steep mountain areas. Table 1 shows data for the major streams in San Fernando quadrangle (U.S. (ieol. Survev 1954, p. 134, 114, 118, 116, 119). In addition to the runoff, a certain amount of recover- able water in the area comes from precipitation which penetrates below the root zone of plants and enters Table 1. Runoff of rivers of Snn Fernando iiuadrangle. Drainage area Discharge feet per in cubic second Stream in square miles (iauge Av. Min. Max. Santa Clara River Pacoi nia Creek _ Little Tujuiiga Creek, BigTujuDKa River... Big Tujunga River... 410 28.2 21.0 106 148 .3 mi. west of Saugiis. Pacoima Dam Foothill Blvd 4 mi. northeast of Sunland 16.0 9.55 2.95 30.3 0.1 24.000 2,640 8,500 50,000 3,000 10581 San Fernando Quadrangle — Oakeshott 17 ground-water storage. Urouiul-water storajjre is also re- charged by the absorption of surface runoff alonp stream channels and in alluvial fill. Such recharge is fostered by dams like Hansen Dam which sjircad the runoff widelj' over coarse alluvial-fan material. Total recoverable water for the Los Angeles metro- politan area has long been inade(|uatc to meet water demands of this fast-growing community. Owens Valley water has been imported since 1913 ; the aqueduct crosses western San Fernando quadrangle and empties into San Fernando Reservoir. Colorado River water has been imjiorted since 1942. Troxell and Ilofmann (1954, p. 12) state that local water reserves have con- tinued to be depleted, or overdrawn, since 1950. (In)ini(J \V(it(r. Wozah (19.'i2) has made an interest- ing study of the characteristics of ground water in San Fernando Valley. Ground water in the valle.v comes principall.v from infiltration from precipitation, irriga- tion return, and water spreading. Water-spreading re- charge adds 8,000 acre-feet per year and irrigation contributes 17,500 acre-feet per year. Depth of water table in the valley ranges from zero in the Reseda dis- trict to over 80 feet in the eastern part of the valley. Ground water in the valley moves generally east and southeast and drains to the Los Angeles River. Ground water is present in three principal water- bearing series : Recent alluvium, late Quaternary ter- race deposits, and the lower Pleistocene Saugus forma- tion. The greatest yield of water comes from the Quaternary alluvial fan deposits of Pacoima and Tu- .iunga "Washes where the gravel and coarse sand reach a depth of more than 1,000 feet. Limited areas of terrace deposits yield water. The Saugus is one of the principal water-bearing formations in San Fernando Valle.v. Chemically, the predominant cation in ground water of the valley is calcium ; predominant anion is sulfate in the western, and bicarbonate in the eastern part of the valley. Composition of ground water in the southwestern part of the valley has been affected by calcium sulfate waters from the g.vpsiferous, diatoma- ceous shale of the j\Iodelo formation; that in the east by erosion of the weathered feldsjiars of the granitic rocks. Sodium chloride content has been increasing in the past few years in relation to pollution by the rapidly increasing population. Erosion. The northern margin of San Fernando Valle.v is part of a region that extends eastward along the south front of the San Gabriel Mountains ; it is particularl.v sub.iect to extensive damage b.v rapid runoff and erosion. Sinclair (1954, p. 264-268) has given a summary of this jjroblem and investigations of measures of prevention and correction ; figiires used here are from his paper. The complexity of altered rocks, extensive faulting and fracturing, thin soil cover, steep topograph.v, semi- arid Mediterranean climate, and extreme variation in water runoff are all conducive to a high rate of erosion. An additional factor of great importance is the cliapar- ral-t.vpe of brnsh.v vegetation which is periodican.\- burnt. Sinclair (1954, p. 264) states that within the last 60 years, most of the brush cover of the San Gabriel Mountains has been burnt over at least once ; some areas three times. Experience has shown that acceh'rated road construction has also resulted in accelerated erosion. Even in those areas not recently burnt over, the erosion late in the San (labriel Motuitains is between 1.000 and :i,0()0 cubic yards per square mile annuall.v. Figures of the V. S. Forest Service show that in such areas average annual rates of erosion vary from 450 cubic yards i)cr scpiare mile on the north side of the range to 6,000 cubic yards per square mile on the south side. During the first year after burning, these rates were fomid to increase 15 times on the north side and 30 times on the south side. The effect of accelerated ei'osiou continues for 8 to 10 years after burning. An extensive fire on the mountain slope north of La Crescenta (just southeast of southeast corner of San Fernando (piadraugle) in November 1933, followed by a very heavy rainstorm, brought the disastrous floods of January 1, 1934. Six hundred thousand cubic yards of boulders, rock, and soil were deposited in the com- munities on the alluvial fans of the area. Thirty lives were lost and projierty damage was about $5,000,000. Tinder conditions of such rapid erosion reservoirs soon fill with debris; nine reservoirs in the San Gabriel Mountains observed over a period of 17 years lost 21 percent of their capacities. The water running off dur- ing flood is largely wasted to the ocean. Most efforts to prevent the effects of accelei-ated ero- sion have been directed toward protection of vegetation from fire, restoration of vegetation after fire, and con- struction of debris- and flood-control dams. The U. S. Forest Service and Los Angeles County Flood Control District have been most active in this program. The quick-growing mustard is one of the plants seeded to burnt-over watersheds of the San Gabriel. Proper drain- age provisions and stabilizing measures on cnt-and-fill road slopes have helped to reduce erosion which has been accelerated by road construction. Research by the U. S. Forest Service is being continued in the Los Angeles River watershed, which includes the drainage areas of Pacoima, Little Tujunga, and Big Tu.iunga rivers. Sin- clair (pp. 267-268) reports that : Tlic invciitor.v of physical conditions in the samiilc aroa.s re- vealed that: (1) the surface area is 20 per cent greater than the map area; (2) average slope of the land is 68 per cent; (3) the angle of repose is approximatel.v 70 per cent; (4) 59 per cent of the land is steeper than the angle of repose; (6) channel gradi- ents average 44 per cent, or 2,300 feet per mile. The sources of eroded sediments, in their appro.ximate order of importance, were found to he: (1) stream hanks and slopes re- juvenated h.v undercutting; slopes with south e.vposnres ; (3) ver.v sleep uplaiul slopes; (4) fault zones and steep fault faces; and (."i) deep colluvial-alluvial deposits on upland slopes when under- cut h.v roads or streams. The mantle rock and soil were found to move by gran- ular soil-surface movements and by deep-seated mass movements. Slides, caused by undercutting, were the most common form of mass wasting found. Soils A soil surve.v of San Fernando Valle.v was made in 1915 by the U. S. Department of Agriculture and the University of California. The resulting publication (Holmes, 1917) includes .soil descriptions and a soil map (scale 1:62,500, topographic base) which embraces the 18 Califorxia Division of Mixes [Bull. 172 southern one-third of San Fernando (luadranple. Three main soil ly and temperatures. Soil, rock type, steepness of slopes, burning, and the activi- ties of man have all had lesser influence on vegetation types and in limited areas one or other of these factors may become significant. Since the local climatic factors have been so important, the immediate effects of local relief and stream courses are apparent. Vegetation pat- tern of the area shows a broad overall east-west trend which is broken by the local variations in drainage pattern. Natural vegetation of the quadrangle is dominated by shrub types which include chainise chaparral, sage- brush, cliaparral, and semidesert chajiarral, in the order of their abundance. Shrub types cover 73 i)er cent of the area of the quadrangle. Woodland tree types, including live oaks, alder, sycamore, willows, juniper, and bigcone spruce, form 10 per cent of the cover. Cultivated and urban areas account for 15 per cent of the (piadrangle area, and grasslands about V/^ per cent. Slirith Types. Chaparral types, which are character- istic of the Upper Sonoran life zone, are divided into three types: ehamise chaparral, chaparral, and semi- desert chaparral. Chamise chaparral is dominated by ehamise {Adenostoma fasciculatuni). a shrub with fine needlelike leaves and thin crown canop.y, ranging from 3 to 8 feet in height. Chamise chaparral is very widely distributed over the quadrangle and constitutes 41 per- cent of the total cover. It does not stand by itself but usualh' includes one or more additional species such as scrub oak {Quercus dnniosa), hoary leaf ccanotiius (C. crassifolius), coast sagebrush {Artoiiisia culifornica) , buckwheat brush {Erigonum fascicidatiini), wooll.y man- zanita {Arctosfaphiilos tontentosa), whitebark ceanothus (C. divaricatus), grayleaf ceanothus (C. vcstitiis), and bigberry manzanita {AretostapJnjlos (jlniica). Chaparral is distinguished from the chamise chapar- ral type by the near absence of Adcnostoiiui fascicula- tuni. Because of greater height and denser cover, it is a greater fire hazard than chamise chaparral. One effect of repeated fires has been to extend this type at the expense of bigcone spruce. Semidesert chaparral is similar to the other chaparral types but forms a more open cover. It often covers mountain slopes bordering the desert and is most com- mon north of Soledad Canyon. It onlj' covers one per- cent of the quadrangle. Sagebrush is an "open association containing sages, sagebrushes, or other woody vegetation of similar char- acter." It is very widespread below elevations of 3,000 feet and covers about 20 percent of the entire area. It is characteristic of the lower part of the Upjier Sonoran life zone. The sagebrush shrub type includes broom- brush (Lepidoapartum squamatnm), buckwheat brush {Erigonum fasciculatum), coast sagebrush (Artemisia californica), chaparral yucca {Yucca whipplci), black sage {Salvia mcUifera), white sage {Salvia apiana), laurel sumac {Rhus laurimi), and broom deervetch {Lot Its scoi)arius). Woodland Tree Types. Woodland tree types cover about 10 percent of San Fernando quadrangle. They in- clude the coast live oak {Quercus agri folia), canyon live oak {Quercus chrysolepis), California juniper {Juni- perus californica), bigcone spruce {Pseudotsuga macro- carpa), white alder {Alnus rhomhifolia), cottonwood {Populus froiiontii), California sj-camore (I'lataiius racemosa), and willows {Salijr si)p.). There are three important subtypes of broad-leaved trees in the quadrangle. The first, canyon live oak, in pure stands, is confined to the upper part of the Upper Sonoran life zone and is found on steep rocky slopes and canvons at higher elevations. Trees are 4 to 12 inches lOoSl San Fernando Quadranci.k — Oakesiiott 19 in diameter ami 15 to 80 feet in hci^lit. This type may iiierfie into areas of bijrcone spruce. The seeond subtype, coast live oak, is found in the canyons at lower eleva- tions, and is a much larjrer tree. The third subtype, stream-bottom woodland, includes alder, cottonwood, and sycamore, sometimes mixed with oak. These trees use a larjre amount of water. Junipers occupy about fj percent of the (juadranfjle, ^rrowiufi: only in open stands north of Soledad Canyon. They are shrublike trees whicii are usually less than 7 feet hif;h. They are characteristic of the borderline be- tween Ui)per and Lower Sonoran life zones. The bijjcone spruce occupies the same general areas as the canyon live oak. It is a conifer which may be 12 to 30 inches in diameter and 50 to 70 feet hifrh. Repeated fires have gradually reduced the area of bi^jcone spruce and have relatively increased the canyon live oak and chaparral. Less than 2 percent of the (juadranjiie area now supports the bigcone spruce. Miscellaneous Types. About 15 percent of the (|uad- ranple is cultivated and urban land of the San Fernando Valley and Santa Clara River. Reservoirs occupy a very small part of the land and about half of one jiercent of the (|uadran -Disconformify5 t Unconformity ■^ 1,000 + 200 500 - 1,000 6.400 ( Upper Pico 300 ?) 3,000 700 Coarse sand, gravel, and boulders of San Fernando and Tujunga valleys. Fanglomerate , stream terrace gravels, and older alluvium. Brown-reddlsh-brown, poorly sorted conglomerate and fanglomerate; folded. Light-colored, poorly sorted, loosely consolidated non- marine conglomerate and coarse sandstone; fluviatile and alluvial-fan deposits. Non-marine fluviatile, lacustrine, and brackish-water gray gravel, greenish-gray sandstone, sandy mudstone, conglomerate and thin freshwater limestone beds of Sunshine Ranch gradational. In part, into marine sand- stone of Upper Pico mbr. in Placerita area and west of San Fernando Reservoir. Marine brownish sandstone, siltstone, and conglomerate; foe.siliferouQ calcareous sandstone beds. Id z> o UJ o < UJ o LOWER PLIOCENE Repello fm. undiff. Elsmere mbr. :mi£ 3,000 ( Elsmere 1,400) "^^ Unco n for m ify^ Marine coarse sandstone and conglomerate, sandy shale, laminated gray and brown shaly sandstone, massive chocolate- brown siltstone with carbon fragments, yellow jarosite ( ?)^and gypsum. Marine conglomerate, gray and brown sandstone, massive gray and chocolate brown siltstone, eilty shale and white arkose; base oil-saturated in Elsmere Canyon area.. UPPER TO MIDDLE MIOCENE Modelo fm. 3,000 Marine fine to coarse arkoaic sandstone and conglomerate; thinly bedded ailicious, calcareous, silty and diatoma- ceous shale. MIDDLE (?) TO LOWER (?) MIOCENE ^Disconformify Topongo C) fm. 1,000 MIDDLE EOCENE .^Nof in confacf- Coarse reddish and yellowish arkoBlc sandstone, mud- stone, conglomerate and a large proportion of vesicular basaltic flows and reddlsh-piorple breccia, mostly near- shore uon-marlne but top 200 feet marine in Facoima Hills. Domengine fm. 650 Marine greenish-gray calcareous sandstone, coarse brown sandstone, and cobble conglomerate. LOWER EOCENE TO PALEOCENE ( Capoy sloge ) Subsurface in Whitney Canyon area. ( Megonos stoge ) Subsurface In Whitney Canyon area. PALEOCENE Martinez fm. 1,500 • in o LU o o ? Z bJ < tr Placerito and Diorite gneiss fms. ( Lole Paleozoic ) and intrusive granitic rocks. a. Marine dark greenish-black to olive gray sandstone, thin interbeds of black shale. Thick massive well- cemented lenticul€U" beds of pebble conglomerate. In San Gabriel fault zone. : Plocenta 2,000*) Crystalline limestone and dolomite, graphite and biotlte schist, and quartzite of the Placerite fm. (pm); associated with and intruded by dark quartz diorite gneiss, migmatites, and biotite schist (dgn); all in- truded by Upper Jurassic (?)-Lower Cretaceous (?) granitic rocks (gr). Pioi'RE 2. Generalized geologic column south of San Gabriel fault. 19381 San Fernando Quadraxole — Oakeshott 23 GENERALIZED GEOLOGIC COLUMN NORTH OF SAN GABRIEL FAULT AGE FORMATION OR MEMBER LITHOLOGY MAXIMUM THICKNESS (FEET) DESCRIPTION RECENT UPPER PLEISTOCENE MIDDLE PLEISTOCENE LOWER PLEISTOCENE UPPER PLIOCENE MIDDLE PLIOCENE Terrace deposits Pocoimo fm. Sougus fm Sunshine Ranch mbi Upper Pico mbr Lower Pico mbr. ■> angular " ""^unconformify—T-^ ^—^Uncontormtly' 'Not in conlocfr 650 ,300 Few hundred 700 C) Coarse sand, gravel, and bouldere of Santa Clara River and ItB tributaries. Fanglomerate, stream terrace gravels, older alluvium. Brown and reddlflh-brown, poorly sorted conglomerate and fanglomerate; folded. Light-colored, poorly sorted, loosely consolidated non- marine conglomerate and coarse sandatone; fluvlatlle and alluvial-fan deposits. Non-marine fluvlatile, lacustrine, and brackish-water gray gravel, brown and greenish sandstone, sandy mudstone, conglomerate and thin white freshwater limestone beds. In San Gabriel fault zone: light brownish poorly sorted conglomerate and coarse greenish sandstone; brackish-water to continental (7). Not found north of the fault zone. Marine brownish sandstone, siltstone and conglomerate in the San Gabriel fault zone. Not found north of the fault . LOWER PLIOCENE Repelto fm. 500 Marine gray and brownish-gray siltstone, fine-grained sandstone, mudstone; pebble and boulder beds. 7-^-^Un conformily- 500 Marine buff and gray Bandstone, ailty shale, dlatomaceouH Bhale, and conglomerate. -Uncon/ormpfy- UPPER MIOCENE Mm! Canyon fm. Fine- to coarse-grained more or less vell-consolldated non- marine aedlmentB of fluvlatile and lacustrine origin: red and reddish-brown conglomerate and breccia, v«ry coarse basal breccias; yellow, red, and greeniah aandstone, silt- stone and mudstone; coarse gray sandstone and conglomerate; thin-bedded lacuatrliie siltstone and volcanic tuff beds. o 4 o £^ ^ o^A fr" o ■--rr U n c n f r m I f y — 2- MIDDLE TO LOWER MIOCENE Tick Conyon fm. 600 Fluvlatile and lacustrine reddish sandstone, siltstone and claystone, and gray, tan, and reddish conglomerate, usually well-cemented and well-stratified. o ArtqulQf 'o^^j^ uncontormily LOWER MIOCENE TO UPPER EOCENE Vasquez fn f[||fl/f /fiii;mi)f |jnilW"""""r mumSSmiZ 8,800 Non-marine light-colored and highly colored red, yellow, and buff eandfltone, conglomerate, fanglomerate, and lesser proportions of mudstone and shale; flows of black and reddish vesicular basalt and andesite, purplish breccia, and minor beds of llthic tuff; borate-and gypsum-bearing shale and sandstone. Monollthologic breccias are charac- teristic of parts of the formation. UPPER JURASSIC (?) LOWER CRETACEOUS [_^ Major > J •■{ ""^ tjncon formifjr Syenite - Hornblende diorite Hot in conrocf — '+ + 2 < o ^itf^ . Mendenhall gneiss ond onorthosite - gabbro group pCm Dark red-weathering auglte and quartz auglte syenite and related hornblende diorite. Mendenhall blue-quartz-feldspar gneiss (pCm) Intruded by anorthoaite-gabbro rocks (an); all Intruded by Upper Jurassic (7)-L(3wer Cretaceous (?) granitic rocks (gr). FkU'KK .'1. (ifiu'ralized Kenlofjio column nortli of San (lahrit'l fniilt. 24 California Division of Mines [Bull. 172 hall gneiss is exposed. In Pacoinia Canyon, about mid- way between Dajrger Flat and Dutch Louis Camp, dark altered gabbro-norite intrudes quartzo-feldspathic gneiss and numbers of large and small inclusions of the gneiss may be seen in the dark gabbroie rocks of this part of Pacoima Canj'on. West of Paeoima Canyon, the gneiss- gabbro contact is rarely well exposed, but on Santa Clara truck trail 1.6 miles in a straight line east of Paeoima-Santa Clara divide, dark fine-grained to coarse- massive gabbro-norite crops out crosscutting regularly banded Mendenhall gneiss over a distance of several hundred feet. At this locality, Neuerburg and Gottfried (1954, p. 465) obtained an age of 930rt 90 million years from zircon of the intruding mafic gabbroie rocks. Internal structure of the Mendenhall gneiss is com- plex; more so than that of the anorthosite-gabbro group. Many apparently minor pre-Cretaceous (?) faults (ear- lier than granodiorite intrusion), irregular joints, and fractures break up continuity of structure. li'oliation, or gneissic banding, is universal and is so irregular and varies so much from place to place that generalities ap- pear to be of somewhat doubtful value. Attitudes of foliation indicated on the geologic map, plate 1, have been shown only where .some consistency in planar band- ing was observed. Tlie most frequent strike of foliation is west-northwest, parallel to structural trends in the San Gabriel fault zone; this is most consistent east of Mendenhall Peak. Most dips are steep, and the most frequent direction of dip is south, off the anorthosite- gabbro core of the range. I'lioio 1). F;nill<'(l ami luet'ciatcd li!;lit .'iiid dark facifs of iiit>- Cainlti-iati Mt'iidcnhall Idii** (juartz gnei.ss cxpo.scd on Little Tiijmi^a Uojul a few .\ard.s nortli of San iJabrifi f:iult. The foliation reflects actual differences in composition of the rock; light bands being higliest in quartz and feldspar, dark bands highest in biotite, hornblende, and relict pyroxenes. Individual baiuls range in thickness from less than one millimeter to several feet ; all are discontinuous and lenticular. Large-scale foliation, frac- turing, jointing, and blocky shattering, apparent in the field, arc also reflected in textures and microscopic struc- tures of the rock. The characteristic texture is fine to coarse granoblastic ; microfoliation can be seen in some sj)ecim('ns, and veinlets of late biotite, chlorite, and quartz are common. Photo 10. Faulted rocks of the pre-Cambrian Mendenhall hlue iiuartz t;neis.s on I^ittle Tujunj,'a Koad. Petrology. The Mendenhall gneiss comprises dark, blue-gray, fine- to coarse-grained quartzo-feldspathic granulite, fine- to medium-grained hypersthene quartzo- feldspathic granulite, sheared, much-altered greenish- brown amphibolite, biotite schist and dense, fine-grained metadiorite. The most common rock is mottled blue-gray granulite, very high in blue quartz, with irregular bands, streaks, zones, and clots of greenish-brown ferromag- nesian minerals, sparse small pink garnet crystals, and pyrite. Irregular and lenticular alternating light and dark bands | millimeter to 1 centimeter thick are most characteristic of these gneisses but coarser banding is quite common. The most striking and universal charac- teristic of the Mendenhall gneiss is the high percentage of blue-gray quartz, so dark that the gneiss looks much higher in ferro-magnesian minerals than it acttmlly is. The shade of quartz is not unlike that of bluish-gray plagioclase in the darker facies of anorthosite and asso- ciated gabbroie rocks. Petrography of the Quart zo-Feldspathic Granulite. Colorless quartz was found in all thin-sections studied, and ranged from 16 to 40 percent of the quartzo- feldspathic granulites. It is present in both light and dark bands of the gneiss but forms a larger part of the light bands. All of the quartz is blue-gray in hand specimen. High-power magnification shows streaks of inclusions which could not be identified. A spectre- graphic analysis by Charles W. Chesterman showed titanium to be "moderately common" and suggested that the blue coloration may result from a titaniinn mineral. Qiuirtz is in anhedral grains of irregular sizes and in clusters, or mosaics. It is always a late mineral and may be seen embaying and replacing plagioclase. Veinlets of quartz and calcite cut across fractured older quartz grains, feldspars, and ferromagnesian minerals in some sections. Myrmekite borders some feldspar grains. Plagioclase, in anhedral unzoned grains, is the most abundant mineral, forming from 20 to 65 percent of the granulites studied in thin section. It is characteristically antiperthitic with slim lenses, pods, or blebs of potash feldspar in the plagioclase. Such antiperthite is common in the granulites, according to Eskola (1952, p. 148). 1958] San Fernando Quadrangle — Oakesiiott 25 Figure 4. Sketch of thin-section of quartzo-feldspathic granulite from Mendeii- hall gneiss (see table 2, 122-1). Relict hypersthene grain in center of field sur- rounded by rim of pale greenish hornblende, quartz mosaic, and selvage of irregularly oriented wisjis of biotite. Abundant highly altere> _3 so 'a c to o ■g 00 e •5 «> s Ct, B o 1 s5 o CM » M IM g t-S C4 e E :^ T to a V V V V V o ■S S M3 ^ ^ „ ti V V V F f^ o *« ^ — <33 00 o OO V ~" CO eo e « S V V g s w: - r^ - V - u ■o A ^ 7 V g CO g C^I V " ' o c^ «o Wi »o ^ ^ cc "" "" V V -, J3 t o ir ^^ W w M ^^ ^^ _ ^^ CO T «o \/ V V " cS h- „ „^ ^^ _^ „_ T CO CM V V V "" s d » -o -o 1 C &• «a o 1 o 3 ■^ ; ii V * 1 1 •< 3 O PQ S 'E J 1 o .4 Oh 1 g 1 5 6 s ^ CO „ t^ <-3 s CO ^" CO "* eo **" ^ o o o o ec o ^ •o CO pj r^ o CM CO OO CO »o i>- CO to S2 o ->* "^ CO (M CO o o « o QO -«• •^ U3 OO ■-»• •a "f o» C^I CO r- M C>1 ^- S CO CO i^ N ■V N ca eo M o o o o „ _. _ _ , ^ •r ^^ (O c^ CO w O W3 O CO M »o o o -»■ ^ c» § d e4 eo CO ' o o o o o Oi CO r- o »• «o o> >o W5 r>. eo iS CO o '^ o CO CO o o o o •o CO C4 -H .-> s CO CS> M ,4 .« u >< s < z -< -< g 'i" o s^ s U i ^ Tf r^ ^r rH M M 04 as j^ eo H J H ^ ^ T T N '^ J3 ^ J.^ 00 OO CI a> 00 M .4 o o ci (4 CM " o 9 9 th 9 ^ d 1 9 + 9 l" 9 6 4 c3 •< E^ 2: u '^ ^ X X H (C i!t:)S| San Fernando QtADRANc.LE— Oakerhott 27 s » s s s S CO " CO rt 8 CO 5 QO Tf ■^ — • "■ d OC OO _^ OS CM CM -r o -n to oo CO o o s 09 g a , 00 t^ -»■ 'I" s CO CO C4 8 CM M lO '^ ■<1' " d C>< o CO OS -r CO CM ^ g oo o r-. oo ■^ U3 CO o CM fC CM CO PO ^ d n CM CM to ^ eo r^ _ CD CO w OS CO o 00 ^ CM CM s c4 o o* d o CM t^ CO CD « to •* s Ol o OS CO o o CO CO 2 oo CM O d d 1 M A OS kO OS : t- CM r> CM o o ec -r CO OS CO CM 1 « ec CO C3 to ^ d d -f eo 1 *— « -o d S O g. H e 8 "^ "a CO a "" •o «? T3 e 5 CD -»• ■rr lO M CO o W5 tXi t GO CO CO CM M3 OS — . o § :; 2 CM O CM CM "" d O « OS t^ n E- J w eo t- -^ *? eo an "S t^ T e^ -" ^ ^ (A CD ■^ to o »o c< "2 t^ ^ CJ •o d to OS ^ CO CO ^ ^ O d d e^ C4 CO J2 T ^ "S '5 o i 3" < < K 1 .5 S < -2 & 1 o ii o -< 3 1 s 1 t < I 2 =S « = 2 <^ -S E § ■ tt> re 2 i: -^1- E ■;:■ ^ CO „ ' E EI ZZ a "O J2= =f °- E H — a; = E re ^ P- < - c '-o ~ S * - " . S S fe .2 -ii „■ i; _■ ^ =■= ^ _ aJ ■*" i ~ Q. >,:5-r -=' >,^os CH = = c _ = ^ go S i s- o c E =j: •= S ^^c'S--^-^ = ^•= '^ = CM c ■ ~ M x: . . . . - . . . . CM t- O cCceCC30'-'C-0:0'^ fh m H — '-iCMCMOicMece'S .g= 3 11 M -E i:K .5 '^'e K il^ E^= =■=^5 S=_5XE M re ■ 3 aj — 5 t^ — S'^'c c^: ^^'S|i# .111 £^ a . re .r-c M« re a.S C- I*. , "^ "c ^ C^ i g i-5 = 2 i^ ^ 5 =« |s|oE2 5 .^ O. O Q. = fcCT ! 3 ^i-o >.-a 3 u S "S . M M =* 2 '^ ^■ a, ^ trf t; ~ E^-^SS 11 "re re .5 > C o Qi p, - ^ >( "ac-c "^ .^ 3 - re ^ ^ 5 3 ■ re N! ^5 — = -=Ji-3CfCf = 28 California Division of Mines [Bull. 172 0.5 mm ^ I FiuiRE 7. Aiitiperthitic felilspnr in Menden- hall Kiiei.ss. Cri>s.sed nicols. Photo micrograph hy (_'h(irleti ir. ('hestt'niKiii. Ilmenite, ina<>netite, pyrite, apatite, ^arnet, and rutile are present as minor accessories. Ilmenite, embayed and rimmed by secondary leucoxene, is the most abundant and persistent. Apatite, when present, is in euhedral to subhedral grains, and may be represented bj' two genera- tions of crystals. Pyrite and pink garnet are present as small euhedral crystals. I\Iost of the ilmenite is in anhe- dral grains bnt some of it is in euhedral crystals. Very late secondary, or hydrothermal, minerals in- clude biotite, chlorite, quartz, ealcite, leucoxene, epidote, muscovite, and ealcite. All appear replacing older min- eral grains, in fractures, and as veinlets. Texture of the rocks comprising the Mendenhall gneiss is granoblastic — xenoblastic granular — the "granulitic fabric" typical of granulites (Williams, Turner, and 0.5 mm I- -I Gilbert, 1954, p. 235-239). Most grains are xenoblastic, some subidioblastic, and some, such as garnet, pyrite, and ilmenite may be euhedral porphyroblasts. Mosaics of such minerals as quartz, biotite, and hornblende, and irregular thin alternating bands of predominantly light and predominantly dark minerals are characteristic textural features. One mm Fi(a KK S. Aiitiperthitic feldspar in .Meiulenlinll gneiss. ("ros.sed nicols. Photo- micrograph by Charles W. Chesterman. Fici'KE !•. Xlendenliall gneiss from I'aooima-Santa Clara divide cm Little Tnjunga Ruad, illnstratin;; xencihlastic grannlar textnre. I'eldspnr.'' are micnifline anil idigoela.se antipertliite ; white min- eral is late auhedral quartz. Calcite is in fractures and partiall.v replaces feldspar. Crossed nicols. Photomicrograph by Charles W. Chealernian. Chemical Analyses. Chemical analyses were made of two specimens selected as typical of the Mendenhall gneiss. Modes, analyses, and norms of these rocks, and others for comparative purposes, are shown in table 2. One of the analyses of the hypersthene quartzo- feldspathic grannlite (specimen 12-47-1 b) facies of the Jlendenhall gneiss closely resembles the average of 11 biotite tonalites (Xockolds, 1954, p. 1015). The other, Mendenhall quartzo-feldspathic graiuilite (specimen 122-1), is similar to the average of 45 biotite adamellites (Nockolds, 1954, p. 1014). These two analyses are strikingly similar to those of 10 eharuockites and acid charnockites (Pichamuthn, 1953, p. 165) showii in table 2. Rock Name. Pre-Cambrian gneisses of granoblastic texture, similar in field appearance to gneisses of recog- nized plutonic origin, high in quartz and plagioclase and containing pyroxene, hornblende, biotite, microcline, ilmenite-magnetite, and garnet, have been given various names, including charnockite, (luartzo-feldspathic gneiss or schist, and gramdite. In south India Holland (1803) gave the name char- nockite to a granulitic rock composed essentially of hypersthene, microcline, and (juartz, a rock type used in the tombstone of Job Charnock, founder of Calcutta. Holland used the term charnockite series for the rocks genetically related to each other, and to charnockite, in a pre-Cambrian petrographic province which includes norite, gabbro, and pyroxenite. Pichamuthu (1953, 178 pp.) has summarized world-wide work on the charnockite i!):)8i San Fkknamx) QrADKANc.LE — Oakeshott 29 Itrohlcin. Thi' two lpiuliiire-Canibriau terranes. The Mendenhall fiueiss is similar to acid-to-interniedi- ate eharnoekitie roeks in other parts of the world in its l)re-Cainbrian ape and association with an anorthosite- chaiMiockite series, its field structures, textures aiul mi- crostructnres, mineraloi>:y, and chemical composition. In preference to "charnockite" the rock most typical of the Mendenhall pneiss i.s here designated by the more de- scriptive term quartzo-feldspathic pranulite. Oriyiii. Mueh more work must be done before the characteristics and origin of the Mendeidiall gneiss can be discussed with any degree of finality. However, the foregoing description and discussion seem to point to the following broad sequence of events. 1. Dcep-.soated liiKli-tPiniierature, hish-pressuip ii>f;ional meta- morphisni (pliitdiiicV i of (|unvtz monzonite to (luartz diorito rocks to prodiK't' ^nl:lrtz-pl.■lJiioclasf-p.^ roxeiit' rocks of the ^ranulite facies (Tiiriifi-, 1!I4,S. p. 1(I0-1(« ; Turner and ^■(•rllc>of;lMl. til.')l : Willi.-ini.-!, Turner, and (iilhert, l!1.")-t, p. 2.X.">-i'{!)) . Chemical anal- yses and relict textnres favor a plntonic origin of the.se rocks, although the possiliilit.v of the original presence of sedinientar.v and volcanic rocks cannot he ruled out. This high-grade nieta- niorphisni was fidlowed in pre-Camhrian time liy intrusion of the anorthi>site-galiliro-norite group. 2. I'nloadiiig and lowering of pressures in much later time to jiroduce fracturing, shattering, and retrt)gressi\e metamori)!iisin with the development of minerals and features characteristic of the aniphiliolite facies, including hornhlende. perthitic feldspars. and grern luu'nl)le!nie reaction rims around relict pyroxene. .H. Ciuitinued lowering of temperature and pressure resulting in the partial replacement of all the older minerals hy quartz, and hiotite and chlorite of the greenschist facies of metamorphism. l-'irst surface exposure of the Mendenhall gneiss was proliahly ill late geologic (Cretaceous?) time. Anorthosite-Gabbro Rocks in the San Fernando and Tujunga 15-Minute Quadrangles Xoiiunclature and Distribution. The anorthosite-gab- bro group of closely associated and genetically related rocks shown on figure 10, Geologic Map of Aiiorthositv- O'abbro in the San Fernando and Tujunga 15-Miuute Quadrangles crops out over an area of 82 square miles in the central part of the western San Gabriel Moun- tains. This occurrence was unique in California so far as was known until John C. Crowell (1957) reported a smaller area of similar roeks in the Orocopia Mountains northeast of the Salton Sea. Principal rock types in the San Gabriel anorthosite- gabbro complex are andesine anorthosite (52 square miles of outcrop area), gabbroie anorthosite, anortho- sitic gabbro, metagabbro, metanorite. diorite and meta- diorite, metapyroxenite, titanomagnetite rocks, horn- blende olivine gabbro, minor olivine gabbro, and small bodies of gabbro pegmatite. These rocks are all facies of the anorthosite-gabbro group and are of the same, or only slightly ditferent overlapping ages. Contacts be- 'ify!^^ .'.V ''^'•■■.- "t^iA^#'^"^^'' ^ „ .• ■■••V ^ir^-^'V->>ii-isi I'HOTO 11. .Vnorthosite in Soledad Can.Moi. I'lal) How hand- ing of alternating white anorthosite-dark aiiorthositic galiln'o is shown in cut aliove the bulldozer. The more massive anorthosite above has blocks of dark gabbroie rock injected as residual basic magma into shear zones late in the crystallization of anorthosite. Photo voinlfHy Soiithcni Pti<-i/ic Conifiani/. tween facies range from sharp to gradational. Particu- larly, wide ditt'erences in the proportions of feldspar and ferromagnesian minerals characterize the common rock types between anorthosite and gabbro or norite. Bud- dington (1939, p. 19) has set useful division lines for the different rock facies, as follows : anorthosite, to 10 percent mafic minerals; gabbroie, noritic, or dioritic anorthosite, 10 to 22| percent mafic minerals; aiiortho- sitic gabbro, norite, or diorite, '2'2i to 35 percent mafic minerals ; gabbro, norite, or diorite, 35 to 65 percent mafic minerals ; the rocks over 65 percent mafic minerals are chiefly olivine gabbro and norite, and metap.yrox- enite — all high in ilmenite-magnetite (titanomagnetite). Iliggs (1954, p. 183) used the name "transition rock" for the gradational types in the range 10-35 percent mafic minerals. Such rocks — gabbroie anorthosite and anorthositic gabbro — comprise as much as a quarter of the outcrop area of the anorthosite-gabbro group, but are not shown separately on the accompanying geologic maps because of the difficulty of mapping the highly irregular gradational contacts. In a detailed petrographic study of the western half of the anorthosite massif, Higgs (1954) recognized the prevalence of relic hypersthene in the gabbroie rocks and so referred to them as "norite." The presence of some monoclinic pyroxene in rocks of this group, the many instances in wliieh almost complete replacement of pyroxene by brown hornblende has taken place, and the presence of green hornblende and chlorite, which ob- scure the original character of the pyroxene, have led the present author to retain the more general name gabbro for many of the rocks in which the predominance of an orthorhombic pyroxene could not be established. Ill a strict mineralogical sense, much of the "gabbro" or "norite" is more properly diorite, as the feldspar is in most cases andesine rather than labradorite. The 30 Cai-ifornia Division of Mines [Rnll. 172 , . fiyr r > i z%' . }i- , :\rii^;- , } ' v\ « o tn > o o o S 5 E Q. - c C 01 S o 1- o« c 6 -St! ♦, thtt! "S" 6 !t:)8 1 San Kkrnando Quadranoi.e — Oakesiiott 31 prefix iiicta- is properly applied to iiuieh of the aiiortlio- site-tral)t)ro trroii)), as frraimlatioii, some recrystalli/atioii, replaeeiiieiit of pyroxenes by honihliMule, and other abbro mas- sif as it existed pi'ior to the Cretaeeous ))eriod have been profoundly modified by Cretaceous (?) granitic intru- sions and by Cretaceous (?) and Tertiary-Quaternary orogeny. The present outcrop area is only generally sug- gestive of the pre-(.'retaceous plan of the massif. Present exposures show the anorthosite-gabbro body to be oval in plan witli the long axis extending for 17 miles N. 6")° W., closely jiaralleled by the San (iabriel fault. The oval is 7 miles wide at its broad northwest end, but only 3 miles at the southeast end. In only one area in San Fernando (juadrangle is an anorthosite-gabbro intrusive contact with older rocks clearly demonstrable: 4 miles of steep contact with Mendenhall gneiss along the south- western margin of the body of anorthosite-gabbro. In this area mafie metagabbro, metapyroxenite, anortho- sitic gabbro, and gabbroic anorthosite are roughly grada- tional in the order named, from the outer part of the massif to inner anorthosite. In the eastern half of the region southeast of the Transmission Line fault, the bulk of the gabbroic rocks (those with over 10 percent mafic minerals) is distributed within and surrounded by anorthosite. The true character of the San Gabriel anorthosite was first recognized by A. C. Lawson who examined four specimens collected by Ilershey (l!)0'2b) from Soledad Canyon just east of Lang station. The specimens in- cluded an "allotrimor])hic aggregate of jilagioclase, green hornblende and magnetite" called "hornblende dioryte" by Lawson, and an "allotriomorphic aggre- gate of plagioclase" recognized as andesine, constituting a rock which "bears the same relation to dioryte that the anorthosytes do to gabbro." Hershey remarked that "All (tlie rocks) are related — a complementary series. They are bound together by a common feldspar, ande- sine." Other than this brief reference by Ilershey, the first description of the San Gabriel anorthosite was bv W. J. Miller (in28b). This was followed by a series of papers by the same author (1929, 1930, 19:h) in which the princijial conclusions were discussed at length ; a reconnaissance geologic map was published in 19:i4. Miller described the "anorthosite series" as comprised of these facies : anorthosite proper, dioritic and gabbroic facies, white and femie facies of anorthosite, and mag- netite-rich facies. In a recent petrographic study of the western half of the anorthosite massif and related rocks, lliggs (19r)4) mapped and described the major units of the "norite-anorthosite complex" as norite, norite- anorthosite transition rock, anorthosite, and apatite- ilmenite rock. AnorthosHc. Anorthosite in the western San Gabriel Mountains ranges through light gray, very light gray, medium light gray and white rock * which, by definition contains le.ss than 10 percent mafic minerals. Light shades of gray predominate. Over-all color in any par- ticular area is dependent on proportion of mafic min- erals, composition of the predominating plagioclase, • Colors by comparison with Rork-color ate magmatic, or deuteric, and hydrothermal minerals include muscovite. albite, biotite, quartz, hornblende, epidote, elinozoisite, chlorite, sphene, calcite, and kao- linitic minerals, diodes of eight specimens of anortho- site selected for chemical analysis (table 3) average 90 percent plagioclase, 2 percent potash feldspar. 2 percent hypersthene, and 1 percent, or less, each of ilmenite, magnetite, biotite, muscovite, chlorite, epidote, kaolin- ite (?), quartz, albite-oligoclase, apatite, and zircon. Primary or early magmatic plagioclase of the anortho- site ranges from oligoclase to labradorite but is predom- inantly basic andesine, a conclusion reached by all other workers in the San Gabriel Mountains. Modes from thin- section study of 27 selected specimens average An 40, norms calculated from eight analyses (table 3) show An 50, and three differential thermal analyses range from An 40 to An 57. "While this does not constitute an ade- quate sampling, it is interesting that the average of these 38 determinations by various means is An 43, the same figure obtained by Higgs (1954, p. 178) from a large niunber of universal-stage determinations. One of the interesting features of the andesine is its general lack of zoning and, in fact, its general uniform- ity in composition through anorthosite and the related mafic facies of the anorthosite-gabbro group. This is a characteristic, compatible with large grain size of some variants, suggesting crystallization under long-continued uniformity of environment. Andesine crystals are char- acteristically twinned according to the albite law. with very minor pericline twinning, but many grains are un- twinned. Minute euhedral inclusions, many of which are recognizable as apatite and zircon, are abundant in many andesine grains. ]\Iany of these inclusions are oriented parallel to twinning and to cleavage directions of the plagioclase. Many of the feldspars are fractured within individual grains and across several grains. Other feldspars present in the anorthosite are micro- cline, orthoelase, albite or albite-oligoclase, perthite, and antiperthite. All these are later than andesine, replacing the latter in some places, surrounding andesine grains, and very commonly i>resent in fractures and cleavage traces with such minerals as quartz, muscovite, and bio- tite. Albite-oligoclase shows distinct zoning in some sec- tions. Antiperthite constitutes a large part of the feld- spar in some sections; it was determined as oligocla.se 3 to orthoelase 1 in one instance. These relationships indicate that andesine was crystallized, fractured, and then affected by late introduction of potash and soda feldspars. In general, however, albitization and other deuteric effects are much less pronomieed in the anortho- site than in its more mafic relatives, as noted in the dis- cussion following. A few .small grains of pyroxene, most of them euhe- dral or subhedral, from 0.2 to 1 mm long may be seen in most sections. The percentage of pyroxene ranges from none to about 6. Some of the grains are recognizable as pale greenish slightly pleochroic hypersthene, probably relatively low in iron. A few euhedral grains of similar appearance but with high birefringence (third order interference colors) appear to be colorless augite or diopside. Pyroxene crystallized with andesine as an early magmatic mineral. Many pyroxene grains enclose or appear to be intergrown with andesine. In many thin sections only relict pyroxene remains, and the grains are replaced by ilmenite-magnetite in their cores and by uralitic hornblende (actinolite) and chlorite on their borders. Early euhedral apatite crystals in some places show the .same deuteric replacement. Patches of actinolite and chlorite of roughly rectangular form suggest the complete replacement of pyroxene. The advanced stage of deuteric alteration in many rocks makes determina- tion of the pyroxene mineral impossible. JIuscovite and biotite are very persistent constituents of the anorthosite, occurring in most specimens. Musco- vite averages about 1^ percent of the rock, biotite about i percent. Some mu.scovite crystals are in flakes large enough to be clearly seen in hand specimen. Both micas appear to be distinctly later than andesine and pyrox- ene, and have been introduced by deuteric action. Still later hydrothermal ( ?) alteration of the feldspar has formed sericite. The presence of significant amounts of late micas is interesting as suggestive of potash enrich- ment in the late magmatic stage. Quartz, in small grains and mosaics, is common as a late mineral bordering pla- gioclase grains and in fractures in plagioclase. Myr- mekite has a similar occurrence. In a few sections studied, quartz forms as much as 40 percent of the rock but 1 or 2 percent is more common. Secondary sphene surrounds and embays some ilmenite grains. Kaolinitie alteration products, epidote, and minor amounts of cal- cite cloud some of the plagioclase, and in some speci- mens are abundant (see, for example, specimen 7, table 3). The average proportion of deuteric and hydrother- mal minerals in the samples of anorthosite studied was less than 10 percent. Differential thermal analy.ses of three samples of anorthosite (samples 2, 5, and 7 in table 3) were made by Joseph A. Pask of the Division of Mineral Tech- nology, University of California, in an effort to identify the decomposition products in one sample (7, table 3) and to determine whether such analyses can supply useful information on anhydrous material such as an- orthosite. Curves for the three anorthosite samples plus 34 Cauforxia Division of Mines fBull. 172 AL8ITE-AN0RTHITE SYSTEM ^7 LIQl JID ^ / / LIQUID h ND CRYSTAL / S/ A '^ PL/ VGIOCLASE ^ y &LBITE PERCENT SO 100 UNORTHITE Fir.URK 11. Phase-rule (HiiKram for plagioclases (iiftei- X. I.. I'xiwen). comparative curves for muscovite, mica, kaolinite, and nioiitniorillonite are shown in fijjure 12. Dr. Pask fur- nished the following comments on the results : "Sample 2 curve shows a small dip followed by a rapid rise at appro.ximatelv I.'JIO" C : sample 5 does the same at approximately l.'!(K)° ('. Since the samples were fused, this thermal activity can l)e attril>uted to melting. Examination of the phase rule diagram for plagioclase (ti;;. 11) indicates that the first appearance of liquid at \'MW° C corresponds to a cimiposition of approximately 'i7\ percent anorthite. No significant peaks at lower temperatures suKftest ahsence or near-absence of decomposition products. Sample 7, on the other hand, shows ccuisideralde activity indicating pres- ence of decomposition or weathered products. By comparison of curves, the.se are not pure micii, kaolinite, or montniorillonite. The indicated curves for these minerals represent 1(X1 percent (pmntities; smaller i)eicenta(;e amounts would result in smaller peaks. Fnun the appearance of the sample curves it appears that the clayey material is largely kaolinitic, proliably tending toward the lieidellite type. Such materials have curves similar to that for kaolinite but with smaller peaks and the exothermic peak rounded off instead of sharp." Chemical analyses of eip;ht selected specimens of an- orthosite from the western San Gabriel Mountains are compared with anorthosite and gabbro-norite from other parts of the world and with average analyses of a large luunber of subsilicic rocks in table 3. The average San^ Gabriel anorthosite is closely similar to Nockolds' (1954) average anorthosite (in massifs) in percentages of silica, lime, and soda, but slightly lower in alumina and significantly lower in potash. The San Gabriel anorthos- ite carries only a fraction of the iron, titanium, mag- nesia, and phosphate of Nockolds' average anorthosite. In the mafic gabbroic rocks descritjcd in the section be- low, these constituents are extremely high; titanium, phosphorous, and iron reaching their highest extremes in the pegmatitic ilmenite-niagnetite-apatite rocks. An average of five analyses of the latter from the San Gabriel Mountains is (FeO+FeoO.O 57.34, TiO-. 11.52, PoO,, 2.59. Higgs (1954, p. 198) estimated the ratio of anorthosite to the ilmenite-magnetite-apatite rock as 35:2. If analyses of these two end types (anorthosite and ilmenite rock) are adjusted in that proportion, the resulting mean would be a rock containing 4.3 per- cent (FeO-fFeaOa), 0.7 percent TiOo, and 0.18 percent V2O:,. Except for high alumina content, this is not far from Nockolds' (1954, p. 1032) average for these constituents in 794 silicic igneous rocks. Thus, analytical data are in support of differentiation of a high-alumina anorthositic-gabbro magma which crystallized to form an early anorthosite fraction and late residual ilmenite- magnetite-apatite fraction. Although chemical analyses showing potassium in the ilmenite-magnetite rocks are lacking, the common presence of microcline with the ilmenite-magnetite rocks is evidence of increased potash, also, in the late magmatic stage. The close correspondence of the norms, or standard minerals, computed from chemical analyses of the San Gabriel anorthosite (table 3), with the modes, which represent actual minerals present, is a reflection of the comparative simplicity of mineralogy of the anorthosite. Muscovite and biotite of the modes appear in the norms Fu.CRE 12. Itifferential thermal analyses of anorthosite sam- ples and reference material (fi>r chemical analyses of -J, 5, and 7. see table S). I nirefnitii of California. Diriaioii of Mineral Tech- noloQii. 1958 J San Fernando Quadrangle — Oakeshott 35 ■^:^^^ • -i-/^'' v. Photo 14. North Fork of Pacoima Canyon, a few hundred feet northwest of anorthosite-galibro contact. Fine-grained lamprophyre and Kaliliro-noritf dikes in anorthosite. Pod of trahbroic anorthosite aliout a foot long just to right of pick. eliiefly in the feldspar.s; potash of the micas, of course, appears in orthoclase (Or). A small excess af alumina found in computation of the norms may be dissolved in the pyroxenes. Silica, in small excess in all the samples except two, is actually late quartz which appears in the modes. The excess silica, alumina, and water of sample 7 probably make up the kaolinitic alteration products recognized in thin section and diflferential thermal analyses. In comparison with Nockolds' norms for an- orthosite (in massifs), the San Gabriel anorthosite is significantly hij;her in ((uartz (Qu) and lower in ortho- clase (Or), mantial scttliiij>: of aiule- sinc and iiyroxeiie crystals of slifrbtly ilittVreiit density and roufrhly the same order of size eoutimiously sepa- i-atini'oic rocks. Soledad Can.von Road near Sulphur Spring.s. granular rock with s.vnneusis texture, composed of 80 liercent calcic andesine, 8 percent actinolite and chlorite after pyroxene, 4 percent green and brown deuteric biotite. 2 percent perthite or microeline, 3 percent late apatite, and the balance ilmenite-magnetite, and late epidote, clinozoisite, calcite, and quartz. The plagioclase is partly replaced by albite-oligoclase and perthite or microeline and is saussuritized. In manv places the rock has a coarse gneissic .structure and ma.v show primary regular banding. The typical anorthositic gabbro (norite, diorite) is a dark, medium-grained xenomorphic granular rock, in general with mottled ophitic texture, composed of 68 percent andesine or andesine-labradorite, 22 percent hypersthene or elinopyroxene which has been largely replaced bv actinolite with some chlorite and biotite, to 5 percent olivine, 3 percent late apatite, and 4 percent ilmenite-magnetite. The plagioclase is saussuritized and deutericall.v replaced b.v albite-oligoclase. The olivine, where present, has been largely replaced by antigorite and iddingsite. The rock is gneissic or massive ; primarv banding is less prominent than in gabbroic anorthosite. The more basic gabbro (norite, diorite) .or metagabbro group includes those rocks having 35 to 65 percent mafic minerals. Thev are verv dark, massive, fine-to-medium- 38 California Division op Mines fBnll. 172 2.0mm. 3.0 mm. Figure i;^. A, Pyroxene entirely replaeeil l)y fibrons iiKKregate of iintiKorite and chlorite (An + Cll. Apatite (A) in lar^e sulihedral and euhedral grain.s. Hrown liornlijende (H). abundant in this section, forms only a small part of the rock, li, Interj;ro\vth of ilmenite (li^ht), developed parallel to crystal directions in magnetite. Sketched from polished surface of titanomagnetite, etched by HCl. graiiipd rocks with tlie proportions of plagioelase and mafic minerals ranging more widely than the dark color of the hand specimen suggests. The plagioclase, 30 to 60 percent of the rock, is apparently identical with that of the more anorthositie rocks. The predominant mafic mineral is hornblende, with the green-to-brown variety less common than the bright green actinolite. Most, if not all, of the hornblende has been formed by deuteric replacement of pyroxene, but determinable relict pyrox- ene is rarely seen. The hornblende has, in turn, been corroded and partly replaced by aggregates of chlorite, epidote, and clinozoisite. Deep red-brown (titaniferous?) biotite and green biotite are present in nearly all speci- mens; they have replaced pyroxene and were noted selectively replacing plagioclase. From 5 to 10 percent anhedral to euhedral crystals of apatite, and like amounts of ilmenite, magnetite, or titanomagnetite are present in nearly all specimens. These rocks generally are in small Photo 21. Light and dark bands of gabbro-norite, gabbroic anorthosite, diorite, white anorthosite, and ilmenite-magnetite-rich rocks. The ilmenite-magnetite rocks al.so are found in lenses, pods, and blebs of various sizes and shapes. Scnith of Transmission Line fault. San Fernando-Tujnnga quadrangles. Camera case is !) inches long. irregular bodies gradational into more anorthositie rocks on the one hand aiul more basic types on the other. They are predominantly massive but show gneissie structures which may be both primary and tectonically induced. Titanomagnetite Rocks. The rocks in the western San Gabriel anorthosite-gabbro complex, comprised of over 65 percent mafic minerals, are characterized by very large proportion of ilmenite, magnetite, and apatite, and are here described as the titanomagnetite rocks. They are very dark, black or brownish-black, massive, fine-to-coarse granular crystalline rocks and schistose metapyroxenites comprising such varieties as apatite- titanomagnetite metapyroxenite, biotite-chlorite schist (metapyroxenite), amphibolite, clilorite-titanomagnetite rock, hypersthene-apatite-titanomagnetite rock, titano- magnetite-apatite gabbro, titanomagnetite-augite-olivine gabbro, hornblende norite, hornblende gabbro, and titan- omagnetite rock. They occur as irregular lenticular masses with sharp to gradational contacts with anortho- site or gabbro, as pegmatitie bodies carrying quartz and microcline, and as dike-like bodies. The titanomagnetite rocks crop out as many small bodies over possibly 3 square miles of the 82 square miles of the anorthosite- gabbro complex. The author has previously described some of these rocks and their utilization as titanium ore (Oakeshott, 1948, 194!)). Their occurrence as ore deposits is also discussed in this bulletin under the heading Titanium in the section on Economic Gcologxj. llagnctite, ilmenite, and titaniferous magnetite all occur in the titanomagnetite rocks, but it is iisually diffi- cult to say how much is titanium-bearing magnetite, how much is a micro-intergrowth of ilmenite-magnetite, and how much distinct separate grains of ilmenite and mag- netite. In this section the term "titanomagnetite" is used to cover all these combinations. The percentage of titanomagnetite in these rocks ranges from 1 to 98. Titanomagnetite studied under the metallographic mi- 1!1581 San Fernando Quadrangle — Oakeshott 39 I'llOTO 22. IJoail 1)110 mile l>clow Monte Cristo miiips. Tnjiiii(;:i quadniiiKle. Much fractured anorthosite with ilnienite-inaf,'netite- chlorite-pyroxenite in fractures and interban(U'(l with aimrthositp. croscope appears as an iiitergrowth of ilmenite and maIonte Cristo mine. they probably represent complete replacement of early pyroxene crystals. Apatite erj-stallized in two genera- tions, represented by early minute euhedral crystals and abundant large, late-deuteric, anhedral to subhedral crystals. Hornblende is a red-brown variety, partly re- placed internally and marked by reaction rims of titano- magnetite. Titanomagnetite also transects, includes, and embays apatite and pyroxene (?). As nearly as can be determined, chlorite, treinolite, and titanomagnetite were formed simultaneously. Order of crystallization was pyroxene ( ? ) -early apatite, hornblende, chlorite-tremo- lite-titanomagnetite. 2.0 mm 2.0 mm FlGi'HK 14. .1, Sketch of thin .section of alteied iipiitite-ilmenite-mnRnetite pyroxenite. Pyroxene entirely replaced hy fibron.s aKKregate of antijiorite and chlorite (An-fCll. Apatite (A) in lai'^e siihhedral to euliednil grains. Hrown hornhlende |H) almndant in this .section, forms only a small part of rock. Ilinenite-ni.iKnetite replacin;; hornlilcnde and altered pyroxene often along cleavage traces and mineral grain contacts; also reirlacing apatite at contacts and along fiactures. /{. Sketch of thin section of olivine gabbro, plane polarized light, (iOx magnification. Augite {Xu) and olivine (Oil surrounded by fibrous, green actinolite reaction rims and partly replaced by ilmenite-magnetite. Apatite was first mineral to crystallize. Antiperthite makes up the balance of the rock. \9:->s] San Fernando Quadrangle — Oakeshott 41 e O e e ■ Is 5 S a (ei6I pinMaauig 'eudiiiioods f oavjoAv) OpBjo]oj 'jjo (jiji noquBQ (Fe 45.57) Tr to 36.76 0.05 67 8 .'; « c o a (£161 'PlB.«»auig '«^A\ 'HV "OJI 62.99 23.49 trace 50 42 X X X X X (S16I 'piBMoauig 'suaiu -pads 11 aSBjaAV) eajo snojajiuBjii ojqq^a Hl'iinQ 66.16 10.96 trace X Locally abundant; ave. low X X X X XXX (£161 'pI^Maaaig 'IHH pJO|w«S 'suaiuiaads g aSBjaAy) ajo noBpuojipy Chemical Analyses •> 15.77 S 1 S g X X X X X (£161 'PIB-ttaauis 'puoj uioaui'i) 'aJO IBUIJO^ ajo 3(0BpuOJipY 58.60 12.31 0.82 44 23 — CO tt) 7.3 0.09 (£161 'piB.waSuis— paoj ujojun 'suaiuioade j; aSBjaAV) ajo noBpuojipy 47.80 15.95 0.16 27 30 Chroniite 0.55 c^ d (£161 'p[B.wa3uig "anun 5|ooy li]dg) -ajo j^oBpuojTpY' 43.79 15.66 0.04 23 29 ■* Ph CO d (1061 'n«9— aJO euauiioade i agBjaAy) Chemical Analyses 73.24 25.30 trace Modes X X X X X (9^61 '^ajjl 9 "? — ..aauiioadsiBDidXx..) m 2 ^ x x ■o-«AV "IIV aoJI ^ o X X X (£161 '-laq^X P"« nosiB^^i) ,,ajiuos|au,. apuaiqujofj Bmi3ji^\ ucjauiAo^ jBaj^ 22.73 6.85 12.97 3.29 given on o rocks X X X X X (£161 'JaqBX puB uoeiBAV) Brai3ji^\ aojBaiAOT JBajij 20.20 31.45 15.78 9.40 No modes these tw X X X (S£6I ■uasuuBi(Of) aii^i^anSBui jaaidg puBidBT qsipaAvg FeO 28.29 FejOi 43.01 11.10 0.013 X 00 X ■-H X X X (tl-01) snooj c JO aSBjaAV ical yses' 14) 57.34 11.52 2.59 des' 45 22 to CM XXX 1 c 3 o O c •^ Chem Anal (10- 49.87 10.88 5.49 Mo 40 21 CO X X 2 65.17 5.65 0.53 55 11 ^ s X w 43.70 5.07 6.48 39 10 lO X X = 64.97 18.20 0.19 49 34 - «D o 62.98 17.80 0.26 44 34 - 00 X 9. a ■'B c s i s s OS E i S i < 1 i c i a < 5 •< 1 c c a c j: X § ^2 -a s ■Is .1 a ■a c a c u o X B^, '^ >. - 3 c-i • £"« " - bo 3^ & ^ = °" - -*; = * . I*" -«" O oj ^ i =■' E -S ^ -S o c c ^■ M E c E '-^ = §*:«« P^HHOpC SJ « « 3 t^OJ ■ti : o in o '■^.oc-1 5 — "S^^ /: O C CS 3 li= = ig =5 - 42 California Division ok Mines [Bull. 172 Titanomagnetite Gabbro *. A significant part of the titanoniafrnetite prroup of rocks consists of a closely related but unusual series of gabbros, qtiite distinct ill several respects from the nietapyroxenites. In the field they are readily recognized as massive, extremely tough, compact fine- to medium-granular lustrous black or brownish-black, high-density rocks, generally weather- resistant in outcrop. The minerals present — plagioclases. pyroxenes, olivine, titanomagnetite, green spinel, apa- tite, hornblendes, and biotite — are tho.se found in the more basic facies of the anorthosite-gabbro complex, but are characterized by extreme freshness and complete lack of any cloudy secondary or alteration products. The simi- larity in appearance of various hand specimens disguises the great range in proportions of the constituent min- erals as determined by the microscope. Any one of the minerals named may be lacking in a single specimen, but in another specimen may constitute 20 percent, or more, of the rock. Textures are predominantly xenomorphic granular but some are hypautomorphic ; there is a marked tendency for individual minerals to be agglomer- ated or clustered to develop a synneusis texture. Four of these rocks examined in thin section are described. A specimen selected from the large area of titano- magnetite rocks (designated "gbm" on plate 1, Geologic Map) on Santa Clara Truck Trail in upper Sand Canyon is coarse - grained titanomagnetite - olivine - hornblende gabbro composed of an estimated 50 percent plagioelase, 15 percent red-brown amphibole, 10 percent olivine, 7 percent titanomagnetite. 1 percent green spinel, 5 per- cent biotite, and minor enstatite, colorless augite, and apatite. The minerals show mutual boundaries and tex- ture is xenomorphic granular, synneusis. The feldspar is very fresh andesine (An 43) in anhedral grains 2 • Oliver E. Bowen Jr. kindly furnished data on the amphibole.s and pyroxenes of these rocks based on universal-stage examination of the thin sections. One m m -I millimeters and less in diameter. About one-fifth of the andesine has been replaced by equally fresh oligoelase (An 28) which transgresses twinning and cleavage of the andesine. Augite is in anhedral grains and olivine is in irregular subhedral grains of various sizes as large as 1 mm in diameter. Neither shows any alteration or replacement. Apatite is in stubby subhedral cry.stals averaging half a millimeter in length. Titanomagnetite is in anhedral grains as large as 1 mm in diameter, some of which include as much as 15 percent green spinel grains. Biotite is deep reddish-brown to pale 3-ellow-brown. The most distinctive mineral of this rock is the red-brown amphibole. Ten grains measured on the universal stage gave the following maximum extinction angles: 1 — 7 ± 1 ■2 — ^2 ±2 3 — >.)' ± 1 4 — 12° =: 1 ■"■. — 14° ±2 (1 — 18= ± 1 7 — 12° ±2 S — 13° ±1 — 22° ± :i (2V = 7:{° : opt. iies.) 10 — 10° ± 1 FlOT'RE 1"). Titanoui.iKnetite olivine gabbro. Ausite (top cen- ter), olivine (riKht center), stul)b.v white apatite cr.vstals, plagio- elase. and al>iin(lant ver.v late ilmenite-niaiinetitc appe.ir in this field. Photomicrograph hy Charles 11'. Chexteniiiin. These data indicate an amphibole between common horn- blende and oxyhornblende ; data on two grains (6 and 9) appear anomalous. Possibly tlie hornblende is titaiiif- erous. A second specimen, of medium-grained gabbro, picked a few feet from the first and regarded in the field as the same rock, jn-oved to have no olivine but to consist of an estimated 20 percent andesine (An 40), 45 percent titaniferous cliuopyroxene, 15 percent apatite. 14 per- cent titanomagnetite, 1 percent green spinel, and 5 percent biotite, a minor amount of enstatite, and color- less amphibole. The andesine in this rock was not even partly replaced but the pyroxene crystals show very thin, narrow actinolite reaction rims. Universal-stage examination of six grains of the cliuopyroxene showed Z A c = 38° ; augite-diop.side. The colorless amphibole is within the range of common hornblende. A near-black medium-granular rock from Santa Clara Truck Trail about three-quarters of a mile west of the two specimens described, also shown on plate 1, Geologic Map. as "'gbm," is hornblende gabbro, lacking olivine and low in titanomagnetite. It is composed of an esti- mated 55 percent andesine (An 43), unaltered and with broad albite-twinning lamellae, 20 percent hypersthene, and 20 percent green amphibole and green cliuopyrox- ene. The hypersthene is strongly pleochroie — pale green to pale pink — and perfectly fresh. Fresh, deep green to yellow pleochroie hornblende shows mutual boundaries with hypersthene. Universal-stage examination shows the hornblende to be intermediate to common hornblende and oxyhornblende; similar to that in the Sand Canyon .specimen, except for color. The pyroxene is intermediate between augite and diopside. A coarse-granular, lustrous black titanomagnetite rock from Pacoiina Canyon about one mile southeast of its .iunction with the North Fork proved to be a hornblende gabbro of unusual type. It is comprised of an estimated 50 percent colorless clinopyroxene. 5 percent plagio- elase, 10 percent apatite, 15 percent red-brown anii)hi- bole, 18 percent titanomagnetite and one percent green spinel iiitergrown with titanomagnetite. The plagioelase is fre.sh unaltered andesine (An 38) part of whicii is cut by later oligoelase (An 25). The abundant clinopyrox- ene, determined as augite, is completely nnaifected by i!)r)8| San Fernando Quadrangle — Oakkshott 4-A One mm I — FuiiBK ICi. IIonihlt>niI(< titaiioniagnetite Kiil>lii(i fnim I'lifoinia Caiiyiiii near Xortli Fork. Whitf miiiPial at far liclit is cdlorless i-linop.vri)xcne, several stuhliy white apatite erjstals api)ear at lower eeiiler, and dense hlaeli mass of ilmeiiite-inaj;netite ai)pears to have trans;;resse(l hornhh-nde. Crossed nicols. PIiotomiirogriii>li hi/ Charles W . Chfatfi-mnu. alteration as are all the rest of the minerals in this roek. Apatite is in stubby subhedral grains. The amphibole (oxyhornblende ?) is an unusual variety for this type of roek, similar to that of the Sand Canyon specimen described above. The amphibole errains are anhedral to subhedral. but more crystal faces are shown than by any other niiiu^ral in this thin section. Texture of the rock is synneusis, xenomorphic granular. The freslmess of these rocks as variants of, and en- closed by. the deuterically and hydrothermally altered ultramafic facies of the norites and gabbros is striking and requires explanation. Tliey have been deuterieal'y altered, as partial replacement of andesine by later oligoclase shows, and as the common presence of biotite, amphibole. and titaiioinagnetite suggest. However, these rocks largely ese-aiied the latest deuterie processes which formed so much chlorite and actinolite and saussuritized the plagioclase of the other rocks, and they completely escaped any hydrothermal alteration. Perhaps the ex- treme compactness and tiglitness of the interlocking min- eral crystals in these rocks allowed minimum access of deuterie and hydrothermal solutions once initial cry.stal- lization had taken place. Williams (in Williams, Turner, and Gilbert, 1954) suggests a similar explanation for the f reshne.ss of some dunites. Gahhro rcginofifes. Facies of various members of the anorthosite-gabbro complex are pegmatitic. Pegmatites are recognizable in anorthosite. the gabbroic rocks, and in the titanoniagnetite rocks. The author, in an earlier paper (Oakeshott, 1!)48. p. 2(i3-(i4). called attention to the "close relationship between the deuterically altered titanomagnetite pyroxenites and the pegmatites." Iliggs (l!).54a, l!)r)4b) described facies of anorthosite and aiior- thositic gabbro distinguished by the develoi)nient of giant andesine and hypersthene crystals with poikilitic textures. .lahns (1954) in a pai)er on Pegmatites of Sontlu'in California (\\. :5!)-4()) commented that these coarse-grained "segregation masses" . . . "niiglit be re- gar(h'd as special varieties of jiegniatite. " In Figure ;! of Jahns' paj)er is a very interesting diagram of a "pod- like mass of gabbroic jiegmatite in coarse-grained iiorite, western San Gabriel Mountains." The pod is about 12 feet in longest dimension and is zoned from augite- labradorite pegmatite adjacent to the wall rock through an inner zone of hornblende-labradorite jiegmatite to the core which consists of andesine-hornblende pegmatite with minor pertliite-()uartz-albite-epidote jiegmatite. Photo 2.S. Specimen of quartz (liyht) -ilinenite- maKnetite chhirite .schist in joint and fracture zones in anorthosite in upper Xorth Fork Mill Creek. Mt. Oleason 7J' quadrangle. Phnto hy Mnru Hill. Extremely coarse-grained, or pegmatitic, facies of anorthosite and anorthositic gabbro are not regularly distributed. In the western half of the anorthosite-gabbro complex Iliggs believed the coarsest crystals were formed near the central part of the massif as consolidation of the magma took place from the margin inward. Giant crystals of andesine, for example, are found east of Magic Mountain. However, the widespread presence of very large crystals as characteristic of the central core area was difficult for the present writer to confirm ; in the eastern half of the anorthosite-gabbro complex some of the largest crystals were found very close to the east- ern boundary of the anorthosite body exposed — for ex- ample, on Angeles Forest Highway. On the north and east slopes of Mt. Gleason a very common border facies of anorthosite is coarse pegmatitic hornblende gabbro. The rock has a witle range of grain sizes and consists almost entirely of black hornblende and gray anorthite (An 95). a very unusual plagioclase in the gabbroic rocks of the San Gabriel Mountains. Some hornblende crystals are 8 inches long. Epidote is a common mineral in irregular masses, in veins, and dis- seminated in the hornblende gabbro. In this rock there is no evidence to suggest derivation of the hornblende from an earlier pyroxene. Small bodies of gabbro pegmatites containing rare crystals of green beryl and allanite occur as facies of the gabbro-norite, particularly in a belt along the north slopes of Pacoima Canyon. The largest and one of the most interesting of these is shown on the accompanying plate 1, Geologic Map, by the notation "gb peg" and is the "allanite pegmatite" later described by Neuerburg 44 California Division of Mines [Bull. 172 Photo 24. Specimen of pegmatitic hornblende gahhro, wholly compo-sed of coarse black hornblende cr.vstals and gray anorthite feldspar, a border facies of anorthosite near Mt. Glea.son, east of San Fer- nando quadrangle. Photo by Mary Hill. (1954, p. 831-834). His location should be eorreeted to projected section 5, T. 3 N., R. 13 W., Paeoinia Canyon, approximately 1400 feet southeast of its junction with North Fork. Data for the following description are modi- fied from Neuerburg 's report : The pegmatite crops out in a roughly horizontal zone of irregularly bulging lenses which show sharp to grada- tional contacts with aetinolitized titanomagnetite norite and biotite gabbro or diorite. Chief minerals of the peg- matite are oligoclase, pinkish-brown perthite, white quartz, hornblende, biotite ; minor rare minerals include allanite, zircon, beryl, and uranothorite. Perthite is in very coarse subhedral crystals often in pods with quartz. Quartz veinlets cut the perthite-quartz pods. Hornblende is in black crystals of greatly different sizes, some as large as 3 feet long and 1 foot thick. Biotite crystals, some of which appear to cut across quartz, are in parallel bundles as much as 5 feet long. Apatite, in quarter-inch crystals, is abundant. The rare minerals are present in very small amounts and uranothorite was found in only one perthite-quartz pod on the hillslope about 100 feet above Pacoima Canyon road. Allanite is in thin tabular crystals a fraction of an inch to 18 inches in length. Euhedral purple zircon crystals occurring as doubly terminated square prisms range from microscopic size to 8 inches long. Very pale green beryl is extremely rare. Discontinuous sheaths of very coarse-grained hornblende- biotite-oligoclase metagabbro or metanorite commonly extend around the pegmatite pods. The titanomagnetite-rich rocks as a group were formed in a very late period of igneous activity — the deuteric or pegmatitic stage — in which crystallization of a resid- ual magma, enriched in titanium and phosphorus, and to some extent in potash and silica, took place. In this stage the orthoteetic, or early magmatic minerals such as andesine and pyroxene were partly replaced by titano- magnetite, apatite, brown and green hornblende, and chlorite. Microcline, or perthite, small crystals of brown garnet, and a small amount of quartz are common in the titanomagnetite rocks. Irregularity in grain size, great variation in proportions of the constituent minerals and in the form and occurrence of the titanomagnetite-rock bodies mentioned are other features characteristic of pegmatites. Thus, the titanomagnetite rocks as a whole may be considered pegmatites of the gabbro-norite intru- sive complex. Paragenesis of Minerals. The general order of crys- tallization of the major gradational rock types of the anorthosite-gabbro complex is, from earliest to latest, gabbroic border-zone rocks, anorthosite, and titanomag- netite rocks and pyroxenite-gabbro, with broad overlaps in time. Previous discussions of the mineralogy of the rocks of these groups have indicated the similarity of the minerals throughout the various types and have offered evidence to indicate sequence of crystallization of the constituent minerals. Moorhouse (1938) discussed paragenesis of the titano- magnetite rocks, based on microscopic study of some specimens sent him by Burt Beverly. The author (Oake- shott, 1948, p. 253-263; 1949) also discussed sequence of mineral crystallization and origin of these rocks. Higgs (1954a, p. 190-192) summarized the salient facts on sequence of crystallization in the complex as a whole. These three writers are essentially in agreement on order of crystallization of the characteristic minerals (with a few comparatively minor differences) but Moor- house and Oakeshott consider apatite, biotite, and titan- omagnetite of deuteric-pegmatitic origin while Higgs states these minerals were formed in the hydrothermal stage. Higgs (1954a, p. 190, fig. 17) shows a sharp sep- aration, without overlap, between minerals of three stages: magmatic, deuteric, hydrothermal. Magmatic minerals — those developing in the ortho- teetic stage, early in igneous activity — include andesine- labradorite, hypersthene, augite, olivine, euhedral apa- tite, and euhedral sphene. Plagioclase and pyroxene are by far the most abundant of this orthomagmatic group. Their crystallization was probably nearly simultaneous, as indicated by mutual crystal boundaries in many speci- mens and by common poikilitic inclusions of andesine in pyroxene and also of pyroxene in andesine. The greater tendency of pyroxene crystals to be euhedral sug- gests crystallization of that mineral may have begun first. Field relationships show that crystallization of andesine- labradorite to form the anorthosite proper must have continued after most pyroxene had crystallized out of the magma. Olivine is not an abinidant constituent but its occurrence in norite, gabbro, and the titanomagnetite rocks shows that it preceded all other minerals except pyroxene and andesine-labradorite. In the rare rocks in which fresh olivine, pyroxene, and andesine occur to- gether, the crystal boundaries show a mutual relation- ship. Minute, spar.se, euhedral cry.stals of apatite and small amounts of sphene as inclusions in all other min- erals indicate that very small amounts of these minerals crystallized in the orthoteetic stage. Deuteric minerals — the synantectic minerals, or those formed in the pneumotectic or pegmatitic stage of ig- neous activity — include apatite, actinolite-tremolite, ti- tanomagnetite, green spinel, albite-oligoclase, microcline- perthite, brown hornblende, biotite, chlorite, garnet, and (|uartz. The author considers that development of some of these minerals — particularly soda and potash feld- spars and the amphiboles — began during the latest part of the orthoteetic stage and continued into the deuteric stage. Contrary to this concept, Higgs (1954a, p. 192 and p. 190, fig. 17) closed the magmatic stage with "an episode of shattering, or protoclasis, that uniformly affected the whole complex." However, many of the deuteric minerals (late apatite, for example) have been IftoSl San Fernando Quadrangle — Oakeshott 45 fractiu'cd and transfrressed by later deutoric! and liydro- tlu'iMiial minerals. Amon<>: the abnndant criteria snjr^est- infr the importance of denteric reactions are: partial re- placement, internally, alonjr cleavages, and marginally, of andesine-labradorite by albite-oligoclase, perthite, and mierocliiie; reaction rims, or coronas, of aetinolite aronnd pyroxene, olivine, and plapioclase; the abun- dance of synantectic minerals, which replace and cor- rode the magmatic minerals; and close resemblance of the titanomagnetite rocks to pegmatites. Anhedral to subhedral apatite, very abundant in the titanomagnetite rocks, was one of the earlier deuterie minerals as evi- denced by crystals of apatite which are crossed, emba.ved, and replaced bv titanomagnetite, aetinolite, and chlorite. Titanomagnetite shows a similar relationship to the anipliiboles and to biotite. Chlorite replaces biotite and aetinolite in some sections. The age relationship of chlo- rite to titanomagnetite is less certain to the author than it was when first expressed (Oakeshott, 1048, p. 260, figs. 66-67). While it is true that titanomagnetite appears in some thin sections to include and to transgress older chlorite, it may well be that such chlorite is a selective complete replacement of pj-roxene which was certainly much earlier than the titanomagnetite. The author considers titanomagnetite (including mag- netite and ilmenite) and green spinel as definitely very late magmatic minerals, as expressed in previous papers (Oakeshott, 1948, 1949), because of their observed posi- tion in the sequence of crystallization, their close associa- tion in time with the other deuterie minerals (particu- larly aetinolite and chlorite) and also because of recent work bearing on their temperatures of formation. II- menite-magnetite intergrowtlis have often been regarded as the result of crystallization from eutectic solution. The widely ranging ilmenite-magnetite proportions shown by the analyses (table 5) appear to be evidence again.st a simple interpretation of the eutectic concept. Magnetite and ilmenite melts are mutuall.v soluble at high temperatures, and as temperatures are lowered, exsolution takes place to allow separate crystallization of the two minerals. The temperature at which crystal- lization would occur is iineertain as it would be influ- enced by such things as the particular mineral radicals and their proportions involved, but it would probably be below 800° C. (Ailing, 1936, p. 140, 162, discusses concepts of this type of intergrowth). In any considera- tion of the temperatures at which the two minerals crystallized, the effect of volatiles present in depressing those temperatures is important but cannot be quanti- tatively estimated. Evrard (1949) has written a very significant paper. The Differentiation of Titanifcrous Magmas, which includes 112 analyses and a bibliog- raphy of 62 papers. He discusses the "continuity in the differentiation from anorthosite to ores, passing through the gabbroic facies" and remarks that the "late character of the titaniferous magma crystallization, with regard to the magmatic associated rocks, is now admitted by all geologists." He shows that liquids that become richer and richer in TiO^ as the temperature drops may arise from a magma initially low in Ti02 ; as relative Ti02 increases ilmenite grows in importance. Magnetite, ilmenite, and titanomagnetite are mutually insoluble at low temperatures. Analyses of the western San Gabriel rocks (table 5) are consistent with Kvrard's findings in the Adirondacks. Buddington, Pahey, and Vlisidis (195.'5) utilized experimental data and more than 200 analyses, and reviewed the literature, to reach the conclusion that "The jircsent data indicate that the deposits (normal ilmenite-ilmenomagnetite deposits in gabbro and anorthosite of the Adirondacks) formed at magmatic temperatures." They demonstrated that "var- iations in the composition of the titaniferous magnetite have potentialities of becoming an important element in geologic thermometrv for temperature ranges between 550° C and 1000° C."" Hydrothermal minerals in the western San Gabriel Mountains- — those minerals formed essentially after magmatic processes, when hot water solutions be(;ame predominant — include epidote, clinozoisite, serieite, leucoxene-sphene which rims ilmenite, vein quartz, car- bonate minerals, and sulfide minerals. It is recognized that no sharp boundary can be drawn between late- deuteric and hydrothermal processes, and also that hy- drothermal processes may redistribute some earlier min- erals. The first-mentioned minerals above — epidote, clinozoisite, serieite, leucoxene-sphene — may be partly late-deuteric in formation. However, vein quartz, pyrite pyrrhotite, chalcopyrite, covellite, molybdenite, gold, vein caleite, siderite, malachite, and ferric oxides are all low-temperature hydrothermal minerals. Striictural Features. Outcrop plan of the pre-Cam- brian anorthosite-gabbro ma.ssif is that of an oval, the long axis trending N. 70° W. for 19 miles. The oval is approximately 7 miles wide in its western two-thirds and narrows to a width of 3 miles near its eastern end. It is bordered on the southwest by a narrow 10-mile-long strip of the older Mendenhall gneiss which trends N. 75° W. The San Gabriel fault, striking N. 65° W., has cut acro.ss the gneiss at its western end and is as close as half a mile to gabbro outcrops. The San Andreas fault strikes N. 70° W. in a zone approximately 10 miles NE. of the nearest anorthosite outcrop. Granitic rocks, of Cre- taceous (?) age, have irregularly and intricately in- truded the anorthosite-gabbro complex and Mendenhall gneiss; structural trend of the granitic rocks is not ap- parent. Major right-lateral movements on the San Ga- briel and San Andreas faults are known to have taken place in Quaternary and late Tertiary time (see section oil Structural Geology) ; the time of earliest movements is unknown except that they were probably post-Creta- ceous. Parallelism of these two great fault zones, the mas- sifs of Mendenhall gneiss, and anorthosite-gabbro is not fortuitous; the suggestion is strong that the courses of the San Gabriel and San Andreas faults were broadly controlled and guided by the pre-Cambrian rock massifs and pre-Cambrian structures. Late Tertiary-Quaternary diastrophism, culminating in mid-Pleistocene orogeny, had little internal effect on the anorthosite-gabbro massif except for the several steep-dipping northeast-trending faults that have sliced across it (fig. 10). The most prominent of these — Pole Canyon, Magic Mountain, Transmission Line, and Fox Creek faults — penetrate well into the massif and each has displaced marginal and internal contacts approxi- mately 1^ miles horizontally in a left lateral direction and unknown amounts vertically. Within the massif, 46 California Division of Mines fBull. 172 the faults are marked by clean, sharp planes which are difficult to follow in massive anorthosite or gabbro. Structural grain along the major faults, sometimes observable on aerial photographs, results from fractur- ing and subparallel minor faulting. The west-northwest trending San Gabriel fault and Condor Peak fault form the major part of the southwestern contact of the pre- Cambrian rocks with granodiorite. Western and north- ern margins of the anorthosite-gabbro massif are over- lapped by Tertiary and Quaternary sediments of Sole- dad Basin, a deep structural depression formed at the eastern end of the Ventura Basin in Tertiary time. Most of that contact has been faulted, particularly by the Pole Canyon and Soledad faults. Extent of the an- orthosite-gabbro body to tiie west-northwest is there- fore unknown, but two lines of reasoning suggest a westward plunge of that body: Tertiary sedimentary rocks dip consistently west-northwest at an average angle of about 30° ; and attitudes on platy flow structure in gabbroic rocks at the extreme western outcrops sug- gest a steep westward plunge. The Pole Canyon and Soledad faults were probably developed at the profound discontinuity between the downwarping Soledad Basin and the rising San Gabriel Mountain block. Cretaceous (?) granitic intrusions and their satellitic dikes produced remarkably little effect on rocks of the anorthosite-gabbro complex but they did intricately in- trude the margins, and to some extent the interior, of that massif. In many places anorthosite is literally riddled by dikes and irregular masses of granodiorite, quartz monzonite, granite, pegmatite, aplite, and lampro- phyre extending in all directions. The very complex in- trusive patterns developed can be best observed in the steep south slopes of Soledad Canyon, in the area of mixed granite and anorthosite north of Magic Mountain (pi. 1, Geologic Map), and on Angeles Forest Highway along Mill Creek (fig. 10). Granitic rocks have sharply transgressed anorthosite-gabbro in most places, but east of Mill Creek in the vicinity of the Monte Cristo mines, pegmatitie granitic rocks and associated quartz veins have been injected parallel to anorthosite platy flow structure. Between Mill Creek and upper Arrastre Can- yon there is similar evidence of concordant intrusion of granitic ro('ks: at this point, with a screen of dark gneiss and schist between granite and anorthosite. Peg- matitie, aplitic, and lamprophyric dikes, probably all related to late phases of Cretaceous (?) intrusion, are ■■■» ■ . -^ . 4a«',i-^*^2^^'-*" , .^ ^ ' " .■:^.V',.sJifc;>1l'^ If :„:,-; » '^- Photo 26. White medium-grained anorthosite out by a network (if ehloritized pyro.xenite (?) and metagabbroic stringers in fractures. Just south of Transmission Line fault, west side Tujunga quadrangle. common in all parts of the anorthosite-gabbro complex, but none is large. Man.y such dikes show sharp angular contacts with anorthosite or gabbro, suggesting their introduction into fractures and minor faults, but their irregular orientation serves to .show the lack of con- tinuous structures within the anorthosite-gabbro massif. Photo 25. Blocky fractured white anorthosite in Soledad Can- yon cut by stringers of metapyroxenite injected in late stages of crystallization of anorthosite. Photo 27. Dark metagabbroic rock or metapyroxenite injected in fractured anorthosite, Soledad Canyon. inr)8i San Fernando QuAHKANfli.E — Oakeshott 47 "*■--. ' .- •, '-'-^^^ , : Photo li^s. Dnrk iiKliisious of nictagabhi'oic nnks in ancirthosilc, Soledad Canyon west of Agiia Dulce. Photo hij Mary Hill. Extensive shattering, large and small-scale shearing, breeeiation, and granulation have been recognized by many geologists as characteristic of the anorthosite- gabbro rocks in the western San Gabriel Mountains. These effects for the most part are not continuous ; they do not appear as a structural grain on aerial photo- graphs and individual shear zones usually cannot be followed for more than a few feet. Shattering and bree- eiation in anorthosite proper are less apparent than in the gabbroic rocks because of the coarse crystallization and monomineralie composition of the anorthosite. Higgs (1954a. p. 202-207) states that the complex was "uniformly shattered before deuteric and hydrothermal alteration" by a process he calls "internal explosion shattering" during a definite epoch of protoclasis. The fact of pervasive microfracturing of plagioclase and pyroxene grains, both intragranular and intergranular, is apparent in thin-section examination of these rocks. Dating of much of the internal shattering is equally apparent as late magmatic and deuteric minerals appear in the fractures of early magmatic minerals. The late minerals are also crosscut by still later veinlets of hydro- thermal minerals. On a larger scale, one of the mo.st evident, and also puzzling, features of the anorthosite is the abundajice of irregular dark bodies of widely variant sizes and shapes in the light-colored anorthosite. They have been variously described as "dikes", "dike-like bodies", "segregations", "lenses", and "inclusions." Such bodies are of all sizes from a few inches to a hundred feet in length ; they are irregular in form but usually roughly tabular. Some are lamprophyric dikes of Cre- taceous (?) or possibly Tertiary age. Jlost of the dark tabular bodies, however, are altered gabbroic rocks, amphibolites and chlorite schists — probably metapyrox- enites — often containing ilmenite-magnetite. Their oecur- Photo 29. IrreRular block of light-colored anorthosite about 50 feet acros.s, nearly vertical, in dark gabbronorite high in ilmenite-magnetite. Coarse gabbronorite on right ; pod of dark ilmenite-magnetite pyroxenite in middle of light anorthosite. Pacoima Canyon. Photo .'{(). Irregular lenticular block of white anorthosite almul 20 feet across in dark gal)bro-norite, east of Dorothy Canyon in Pacoima Canyon. Fracture zones in anorthosite injected by similar galibroic rock. rence is similar to that of the titanomagnetite rock bodies ; that is, as irregular, in many places poorly de- fined, elongated, tabular bodies whose contacts with the enclosing anorthosite are gradational in some places but, in mo.st, are quite sharp. No large part of the anorthosite ma.ssif is lacking such bodies but the.y appear most com- mon near the borders of the massif. These mafic bodies are not inclusions of older rocks but have been formed by injection of still-fluid, residual mafic magma into the crystallized and crystallizing anorthosite, their emplace- ment guided by fracturing of the anorthosite. True inclu- sions of older rocks in anorthosite-gabbro are relatively rare. However, in Pacoima Canyon near the intrusive contact with Mendenhall gneiss, the gabbroic rocks eon- 48 California Division of Mines [Bull. 172 Photo 31. Pod of white anorthosite "wrapped" in .slightly later dark gabbroic rock ; a form of "block structure". Lower Iron Canyon. tain some inclusions of the p^neiss. No regular or orderly arrangement of the mafie tabular bodies and inclusions was noted. Inclusions of anorthosite in anorthosite, anorthosite in gabbroic rocks, or the rarer inclusion of gabbro-norite in anorthosite feature a broad border zone of the anortho- site. Good examples may be seen in Paeoima Canyon, Sand Canyon, and on the Angeles Forest Highway. The shapes of such inclusions are irregular and lenticular, and contacts with the enclosing rock are generally sharp. Sizes range from an inch or two across to a hundred feet or more. The rocks involved have the composition of the normal anorthosite, gabbro, and pyroxenite. Their recognition depends on the difference in composition, and therefore color, of the enclosing and enclosed rock. They probably represent blocks of upper marginal crys- tallizing anorthosite-gabbro which sank into the still- fluid enclosing magma. Such structures in the Adiron- dack Mountains were named "block structure" by Balk (1931) and were also discussed by Buddington (1939). In summary, the observed internal structural features of the anorthosite-gabbro massif, including bordering ■^•" ,-"i ■M.. -«;■ r'^ '■& iL' -•SuP'—^ ~-^V-^.v Photo .'i2. Dike of grayish-white anorthosite (hammer) in l)anded gabbroic rocks ; above, small patches of the same anorthosite grade into gabbro. Dagger Flat t'anyon a qnarter of a mile above Paeoima ("anvon. platy-fl'uv banding, discontinuous fractures and gi'anu- lation, mafic tabular bodies, block structure, and micro- shattering of plagioclase and pyroxene cr.ystals, are features that might be expected to develop in a body of gabbroic-anorthosite magma crystallizing slowly, under pressure, from its outer to its inner portions. The author believes that movements and readjustments during crys- tallization under such circumstances could well account for the micro-shattering, also, without invoking Higgs' "internal explosion shattering" theory. Origin and Age of Anorthosite-Gahbro. The origin of anorthosite has received a great deal of attention (Daly, 1914, 1933; Bowen, 1917; Balk, 1931; Miller, 1934; Bud- dington, 1939). Buddington (1939, p. 201-221) has ad- mirably summarized the major phases in origin and development of anorthosite-gabbro masses of the Adiron- dack type in various parts of the world. He defined the Adirondack type "as masses of small to very large areal extent without obvious strongly differentiated stratiform characters and with areal domical structure or struc- tures in the roof of large bodies, such as the Adiron- dacks — ". In addition to the defining characteristics, anorthosite bodies of the Adirondack type consist of py- roxene anorthosites with the plagioclase around An 50, have local border facies, many of which are banded and of more mafic composition, have local mafic phases as dike-like bodies which crystallized slightly later than an- orthosite and are very high in a])atite, ilmenite, and py- roxene, show block structure of anorthosite in anortho- site, and have associated satellitic sheets. Evidence is increasing of the remarkable similarity of this distinc- tive rock association in all its occurrences on earth. There remains little doubt that all known anorthosite bodies of the Adirondack type were crystallized and initially emplaccd in pre-Cambrian time and that such bodies are exposed in all large pre-Cambrian terranes. Entirely contrary to some of his earliest ideas (Oake- shott, 1937), the writer now recognizes the San Gabriel anorthosite as an example of the Adirondack type, ex- plainable along similar lines. Pre-Cambrian age of the anorthosite-gabbro group in the western San Gabriel Motuitains has been substan- tiated by Neuerburg and Gottfried (1954, p. 465) who obtained ages of 930 ±: 90 and 810 ± 80 million years from mafic border facies in Sand Canyon, and pegmatitie facies in Paeoima Canyon, respectively, by use of lead alpha activity measurements on zircon. Previous sections of the chapter on Anorthosite-Gah- bro Rocks in ihc San Fernando and Tujunga 15-Minutc Quadrangles have presented evidence which may now be summarized in the form of conclusions concerning the facts and probable sequence of events in origin and em- placement of the San Gabriel anorthosite. 1. Composition of the parent magma, based on relative areas of rock types and their mineral and chemical com- position, was that of anorthositie gabbro. 2. Differentiation of the anorthositic-gabbro magma continued over a long period of time and was relatively complete, with crystallization of an early anorthosite fraction and very late residual ilmenite-magnetite-apa- tite-pyroxenite fraction. As crystallization took place the residual magma became progressively enriched in potas- sium, phosphorous, titanium, silica, and water. 1958] San Fernando Quadrangle — Oakeshott 49 + + + + + + + + + + + + + + +^ + + + + + + + + + gobbro-norite + + + + + + f + + + + + + + +^i^ + + + + + 30 feet Intrusive contact of gobbro-norite in Mendenticll gneiss, Pacoima Canyon. FiGTBE 17. 3. Crystallization began with the development of hypersthene and andesine crystals, proceeded with crys- tallization of andesine, and all facies of the anorthosite- gabbro complex became solid with final crystallization of the titanium-rich rocks and pegmatites. Differen- tial thermal analysis of some nearly pure anorthosite specimens indicates that material would begin to crystal- lize at about 1300° C, and temperature considerations of the crystallization of titanomagnetite suggest a mini- mum of about 550° C. The presence of mineralizers and volatiles in the primary magma would allow it to remain liciuid at much lower temperatures than the 1300° C for the plagioclase. Late minerals crystallizing in the anorthosite-gabbro, such as muscovite, biotite, albite, niicrocline, epidote, and hornblende, demonstrate the actual presence of liquidus-lowering constituents. 4. Anorthosite-gabbro was intruded into the older pre- Cambrian gneisses and schists (Mendenhall gneiss and others ( ?) ) in the magmatic state ; not emplaced as solids. 150 feet Gobbro-norite intruding Mend- enhall gneiss, Santa Clara truck trail. Figure 18. Intrusive relationships cited earlier in this chapter sup- ]>ort this; dikes of pure anorthosite were noted. 5. More rapid cooling in the outer parts of the magma body caused early development of solid, bordering, gabbro-norite masses ; long, slow cooling of nearly pure anorthosite in the interior developed andesine crystals of large size and uniform composition. Crystallizing andesine anorthosite was repeatedly fractured and intri- cately intruded by the more fluid residual magma frac- tions to develop the complex of sharp-contact tabular mafic bodies so widely distributed. Movements during crystallization of the anorthosite account for granula- tion and internal "shattering" of andesine cr3'stals. 6. The late-magmatic mafic rocks, including varieties of gabbro, norite, pyroxenite, and titanium-phosphorous- rich rocks were intruded in the same stage and under circumstances similar to the rarer gabbro pegmatites. 7. Form of the anorthosite-gabbro massif is oval in plan, but the third dimension is unknown. In the limited border zones observable, flow-banding of anorthositic gabbro is very steep, suggesting steep upward move- ment of the cooling massif. Flow banding could not be observed over the interior of the massif but only in certain border areas where it appeared to dip steeply away from the central massif. Structural form of the massif is thus that of an arch ; a dome structure is unproven. 8. Contacts of the anorthosite-gabbro massif with the older gneisses are essentially concordant, but local dis- cordant relationships with Mendenhall gneiss occur. Roof pendants or inclusions of the older gneisses are rare ; they occur only very close to the contact. The inference is that the massif was emplaced by lifting and shoulder- ing aside of the older rocks; stoping operated as only a minor process. 9. Time of first exposure of the anorthosite-gabbro rocks in the San Gabriel Mountain area is unknown. No clasts of these rocks have been found in metasediraents of the Pelona schist or Placerita series. Anorthosite- gabbro may have been exposed in Upper Cretaceous time but no evidence on that point could be determined. The earliest undoubted exposure of the anorthosite group was in middle Eocene time, as Domengine conglomerate of that age contains numerous anorthosite and gabbro pebbles. All subsequent conglomerates, marine and con- tinental, contain a local abundance of such pebbles and cobbles. Pelona Schist Name and Distribution. In Febrnarv, 1902, Hershey (1902d, PI. 1) showed the "Pelona schists" on a Geo- logical Reconnaissance Sketch Map of Southern Cali- fornia. Later in the same year (1902b, p. 274-277) he named and described these rocks as the "Pelona schist series" from their outcrops over 130 square miles of the Sierra Pelona ridge which trends east-west for 20 miles just north of San Fernando quadrangle. Simpson (1934, p. 378-381) described the Pelona schist of this area. Wiese (1950, p. 12-15) described a sequence of mica schists and quartzite, identical with the Pelona schist, in the Garlock fault zone a few miles north of San Fernando quadrangle. Noble (1954) has receutlj' mapped and described the Pelona schist along the San Andreas fault zone. In San Fernando quadrangle, these rocks 50 California Division op Mines [Bull. 172 I'liOTO 83. I'eloiui siliist in Hoiuiuct Canyon, north of honndary of San Feiniin t^''.-- 'h'' ^•^- .V^-JJijO^v^, Photo 35. Faulted and brecciated migmatites of granite-injected quartz diorite gneiss on Little Tujunga Road in Buck Canyon. ship of the Plaeerita to the pre-Cambrian anorthosite i.s unknown because the two have not been recognized in contact. Goodyear (1888, p. 340-342) reported fossils near a limestone kiln in Pacoima Canyon and said that, 2 miles northwest of Paeoima Canyon "some limestone boulders were seen that were filled with fossils, but they were not very well preserved, and it was impossible to get good specimens of them, the rock being too compact and hard." The most diligent search failed to locate these boulders, and no fossils were discovered elsewhere. Extensive and thick quartzite and limestone forma- tions of Paleozoic age have been described in the San Bernardino Mountains — like the San Gabriel, part of the Transverse Ranges province — by Vaughan (1922), Woodford and Harriss (1928), Guillou (1953), and Richmond (1954). The latest and most complete collec- tion of fossils from the Furnace limestone of this section was made by Richmond and is regarded by C. W. Mer- riam (1954, p. 13) as appearing to confirm a Mississip- pian age assignment. Since Plaeerita limestone closely resembles the Furnace limestone and the two represent remnants of thick widespread sedimentary units in the same province, their correlation is suggested as a reason- able possibility, although an earlier Paleozoic or pre- Cambrian age of the Plaeerita formation cannot be excluded. Diorite Gneiss Name and Distribution. The rocks mapped as diorite gneiss comprise a variety of dark gneisses, metadiorites, massive hornblende diorite, and amphibole and biotite schists. Some are clearly coarse- to fine-grained intrusive rocks cutting the Plaeerita formation metasediinentary rocks and in.iected into them ; others may actuall.y be part of the Plaeerita. Tliese rocks are closely associated with the Plaeerita in their areal distribtition and prob- ably also in time. They occur as septa, roof pendants, and small to large inclusions intricately intriided by the Jurassic-Cretaceous (?) granitic rocks. Many of the rocks are hybrids and migmatites of uncertain origin and age. The diorite gneiss, as mapped, most closely corre- sponds to the Rubio diorite and metadiorite named and described by Miller (1934, p. 7-15), but this and several m''' 'dr I'HOTO 36. Migmatized quartz diorite gneiss (dgn), strilcing due north. Hairpin turn in Little Tugunga Road at Buck Canyon. other formations were included, in part, by Miller (p. 49-56) in his "San Gabriel formation." Miller's type locality of the Rubio diorite is in Rubio Canyon, a few miles east of San Fernando quadrangle. The diorite gneiss formation is found irregularly dis- tributed in the San Gabriel fault zone and south of it between Little Tujunga Canj^on and the overlapping Tertiary rocks at the western margin of the quadrangle. None of this formation was recognized with certainty north of the Sau Gabriel fault in San Fernando quad- rangle, but east of that quadrangle several of the rock masses mapped by Miller (1934) as Rubio diorite may be correlatives of the diorite gneiss of the present writer. Description of Typical Occurrences. The diorite gneiss formation exhibits typical characteristics and re- lationships with other rock units in the complex of crystalline rocks in and near Limerock Canyon where these rocks are thrust over the Saugus formation along the Lopez fault. Here dark gneissic dioritic rocks, high in hornblende or biotite, are in bands from a fraction of an inch to several inches in thickness interlayered with crystalline limestone, quartzite, and other metasedimen- tary rocks of the Plaeerita formation. This series has been injected lit-par-lit, and replaced along bedding planes, by pink granite pegmatite, white biotite granite. I'liuiu liT. .Migmatite produced by granitic injection of late Paleozoic ( '!) diorite gneiss (dgn) and Plaeerita metasedimeutary complex in Buck Canyon. 19581 San Fernando Qiiadranglk — Oakksiiott 53 and ■rraiHHliorite. In some places the baiuliiifi- is ([iiite rejrular for a huiulred feet or more but, locally, many eoinplex ptynii)lctely irregular anhedral crystals of orthoclase. 15iotite is late, molded against feldspar, and most Hakes are partly altered to green chlorite. Much of the granitic rock used as facing on Hansen Dam is biotite grano- diorite. These rocks closely resemble 39 sections of Miller's (1934, p. 43) Lowe granodiorite (oligoclase to andesine 46, orthoclase and mierocline 28, quartz 24, biotite 1, hornblende and magnetite 1). Quartz monzonite and granite are less common vari- ants than quartz diorite and granodiorite. A specimen of light-gray coarse, slightly gnei.ssoid hypautoinori)hic granular rock from the Hansen Dam quarry is tyjiical of the quartz monzonite. It proved to be hornblende- biotite-quartz monzonite comprised of 35 percent ortho- clase, 30 percent oligoclase-andesine, 20 percent (juartz, 6 percent biotite, 4 percent hornblende, 4 percent il- menite, and 1 percent sphene. The high percentage of ilmenite is rather unusual. One thin section of fine- grained biotite granite, hypautomorphic to porphyritic in texture, cropping out in a small area in Limekiln Canyon, consists of 34 percent orthoclase, 3 percent mierocline, 17 percent oligoclase, 38 percent quartz, 6 percent biotite, and 1 percent magnetite, apatite and sphene. Age and Correlation. Direct evidence of the age of this group of plutonic rocks is lacking, except that it is older than the Paleocene Martinez formation and younger than the late Paleozoic ( ?) Placerita formation and diorite gneiss. The granodiorite-quartz diorite group is believed to be related to and essentially correlative with similar rocks of late Jurassic to Cretaceous age in the Transverse and Peninsular Ranges, the Mojave Desert, and Sierra Nevada. Larsen, et al. (1952) ob- tained an age of 100,000,000 years for zircon in a tonalite (quartz diorite) of the Peninsular Ranges. Granite Name and Distribution. The plutonic rock mapped as granite on the Geologic Map (pi. 1) crops out over 4 square miles of the extreme northern part of the quad- rangle between upper Tick Canyon and Vasquez Canyon and along the Pelona fault. It is predominantly buff to pink, fine- to medium-grained biotite-muscovite granite, some of it porphyritic, some pegmatitic and aplitic, and much of it gneissoid. Inclusions of older gneisses and schists are common ; some are recognizable as Pelona schist. The northward extension of these outcrops in the Elizabeth Lake quadrangle was mapped by Simpson (1934, p. 384-385) as pre-Cretaceous granitic rock and granite augen gneiss. The present writer discussed them briefly in an earlier publication (Oakeshott, 1937, p. 227-229). The same light-colored granite occurs in the Soledad fault zone and has .so intricately and intimately intruded 7 square miles of white anorthosite outcrops south of that fault as to make differentiation in mapping impos- sible. Beside the writer's brief discussion cited, Iliggs (1945a, p. 193) has described this occurrence. Granite probably underlies the entire Soledad basin north and northwest of the Soledad and Pole Canyon fault zones. Petrology and Petrography. Texture of the leuco- cratic rocks mapped collectively as granite is essentially medium hypautomorphic granular, but fine-grained ap- 56 Califorxia Division of Mines [Bull. 172 Photo 39. Dikes, sills, ami irrt'Kiil.'ir iii.ii'cl i(.iis of pipik (;r:nnlir rocks in white .Tiiorthosite at ooiitact of sraiUMlii.iite (called "Lowe"' Kranodiorite by Miller). Angeles Forest Highway, TnjnnKa quadrangle. litie to very coarse pegmatitic textures are common. Por- pliyritic phases with pheiiocrysts of pinkish potash feld- spar also occur. Some of the darker pink facies are strongly gneissoid. Variants in composition include muscovite-biotite granite, alkali granite, granite aplite, granite pegmatite, biotite granite, and quartz monzonite. Leucoeratic mus- eovite granite with a small i)ercentage- of biotite is most common. Essential minerals of most specimens are mierocline, orthoclase, perthite, (piartz, oligoclase, muscovite and biotite. Microscopic examination shows anhedral to sub- hedral potash feldspars constitute from 50 to 75 percent of the rock; mierocline is usually most abundant, and 15 to 80 percent late anhedral quartz is usually present. Anhedral oligoclase averages about 5 percent but is higher in some specimens. Biotite and muscovite are both present but one or the other may be strongly predom- inant ; the micas rarely constitute over 5 percent of the rock. Minor accessories include colorless garnet, magne- tite, and apatite. The rocks are not extensively altered but in most specimens oligoclase is clouded by alteration products such as kaolinite (?), epidote, and sericite; the potash feldspars show some sericitization. Myrmekite is present. Many biotite flakes have been altered to chlorite. Hema- tite and yellowish iron oxide appear on the margins be- tween parallel growths of biotite and muscovite. Late muscovite, or sericite, was noted in fractures in garnet, as was also invading quartz. A few specimens of leucogranite precisely at the an- orthosite contacts were studied under the microscope. On the anorthosite side, the rock consists of andesine { ?) almost completely replaced by a brownish mixture of kaolinite (?), granular epidote, sericite, chlorite, and magnetite, cut by minute quartz and albite veinlets, and 1 or 2 percent of potash feldspar. All grains are frac- tured, microfaulted ; twinning lamellae of the plagio- clase are bent. At the granite side of the contact, the rock proved to be muscovite-biotite granite, with the feldspars more completely altered than in most speci- mens and veined by granular epidote and quartz. In one specimen, muscovite grains were roughly oriented to show a distinct foliation under low magnification. Age and Correlation. There is little direct evidence of the age of the granite. It is certainly older than the I'aleoccne Martinez formation which contains granite pebbles, and it is younger than the pre-Cambrian anor- thosite and the Pelona schist, both of which the granite has intruded. Contrary to his first opinion (Oakeshott, 19.37, p. 229-232), the author is now convinced of the great gap in time of origin of the anorthosite and the granitic rocks. It is probable that tlie granitic rocks of the western San Gabriel Mountains are closely related plutonic intrusions and are essentially correlatives of similar rocks of late Jurassic to Cretaceous age elsewhere in the Transverse and Peninsular Ranges, the nearby Mojave Desert, and the Sierra Nevada. As is so often the case, there is a general overlapping age gradation of the facies of the granitic rocks in San Fernando (juadrangle from the oldest quartz diorites to the youngest alkali granites, pegmatites, and aplit<^s. Granite Pegmatite and Aplite Pegmatites are associated with and related to the pre- Cambrian anorthosite-gabbro complex and to the Juras- sic (?) -Cretaceous (?) granitic complex. Data on the pegmatites of southern California have been summarized by Jahiis (1954), who also mentioned briefly pegmatites of the western San Gabriel Mountains. Distribution. Granitic pegmatites are widely scat- tered in the pre-Paleocene crystalline rocks in San Fer- nando (piadT-angle, where they have intruded rocks of all types and ages from the pre-Cambrian anorthosite com- plex to Cretaceous (?) biotite-mijscovite granite. Al- though no area of the efystalfine rocks is without intrud- ing pegmatites, they are most common in association with the pink biotite-muscovite granite, and the anor- thosite intruded by the granite, north of the San Gabriel and Transmission Line faults. Very few individual bodies or masses of pegmatite are large enough to show on the Geologic Map (pi. 1) ; the largest, shown near the junction of the Santa Clara truck trail and tlie head of Indian Creek, is about half a mile in longest dimen- sion. Composition, Texture, and Structure. Mineralogic composition of the pegmatites is very simple. Tliey are composed of widely ranging proportions of pinkish or cream-colored mierocline or orthoclase, quartz, graphic intergrowths of quartz and feldspar, albite or oligoclase, silvery muscovite, small red garnet crystals, biotite, zir- con, magnetite, and extremely rare crystals of green beryl and black allanite. Most hand specimens include only quartz and feldspar. In some places, quartz, potash feldspar, or muscovite make up such a large proportion of the rock that efforts have been made to mine one of these three minerals. Some bodies are nearly 100 percent quartz. Textures of the rocks are typically coarse pegmatitic, with individual grains of quartz, feldspar, or muscovite as large as several inches in greatest dimension. Quartz and feldspar crystals are anhedral ; quartz shows no crystal faces. Some books of muscovite are subhedral to euhedral, and the small crystals of red garnet are euhe- dral. The extremely rare crystals of allanite and beryl (one seen) are euhedral. The minerals are irregularly clistributed and the pegmatite bodies show none of the layering or zoning of some of the pegmatites of the Peninsular Ranges in San Diego County. 1!)-)81 San Fernando Quadrangle — Oakeshott 57 OccKrrriicc. Granite po!j;matites in San Fernando (luadranprle oeeur as: (1), swarms or complexes of small irrejrnlar vein- and dike-like masses in the jrranite and older roeks; (2), lit-par-lit injections in migrmatites ; and (3), individnal masses of irregular shape and widely different sizes. Examples of the first type are best seen in the area of mixed anorthosite and granite mapped alonjr the Majrie Mountain fault, and in Soledad Canyon, where pegraatitic les of various size as large as 6 inches in diameter in matri.x of dark greenish-gray sandstone ; interbeds of black shale. Field count of pebbles : Oranodiorite and quartz monzonite 41 Pink granite 17 Porph.vritic volcanic rocks, various 16 Porphyritic andesite or basalt 8 Diorite gneiss and diorite 11 Quartzite 3 Anorthosite (?) 3 Crystalline limestone, white 1 100 Analysis of the pebble counts shows about three- fourths of the rock types crop out in the San Gabriel Mountains nearby but one-fourth (chiefly hard, colored volcanic and metavolcanic rocks) did not originate locally. The foreign volcanic pebbles, however, could have been reworked from Cretaceous sediments, since removed by erosion. It is probable tliat the Martinez formation in this region was deposited in a littoral zone along a rather rugged coast, with the shoreline not far north of the Rock Creek outcrops described bv Dickersou (1!)14). Thin-section examinations of a common type of dark fine-grained sandstone showed the following minerals: 25% oligoclase-andesine ; saussuritized. (>()% quartz; shattered and veined with iron oxide. 10% hiotite; twisted and ropy, molded against quartz and feldspar grains. .")% chlorite, red garnet, sericite, epidote, and zircon. Mineral grain studies roughly confirmed this composi- tion. The samples studied are poorly sorted ; grains are angular to subangular and most range in diameter from 0.1 to 2 millimeters. The grains are, however, better •Colors compared with Rock-color chart (National Researcli Coun- cil, 1948). rounded in their size range than in any of the later Tertiary sandstones. Age and Correlation. Direct evidence of the age of the Martinez formation in San Fernando quadrangle is meager. However, Turritella pachecoensis Stanton has been found (Clements and Oakeshott, 1935, p. 310) and the distinctive lithologic assemblage makes correlation with highly fossiliferous Martinez strata of the southern Tejon quadrangle appear secure. Continental Oil Com- pany's well Phillips No. 1, drilled in the Whitney Can- yon area south of the San Gabriel fault, penetrated Eocene zones "B" and "C", and Paleocene zone "D" (Domengine, Capay, and Meganos stages, respectively) according to determinations of foraminifers by Boris Laiming and W. D. Rankin. The Meganos "D" fauna was found from depths of 5280 to 5940 feet. 1 >lo-,v that depth the well penetrated a thousand feet ol "Eocene and Cretaceous, undifferentiated" before pass- ing through the Whitney (?) fault zone into gneissic basement*. A number of other wells in the Plaeerita, Whitney Canyon, and El.smere oil fields have bottomed in "Eocene" sedimentary rocks. Domengine Formation and Subsurface Eocene Units Name and Type Locality. P. M. Anderson (1905) first applied the name Domengine formation to strata that are overlain by Kreyenhagen shale and underlain by Yokut sandstone at Domengine Ranch in the Diablo Range north of Coalinga. In current usage, Domengine is a stage name applied to rocks of middle Eocene age in California. It is also very commonly used as a forma- tion name in many parts of California for mappable units in which the middle Eocene microfauna or mega- fauna has been recognized. McMasters (1933, p. 217- 218) formally introduced the name "Llajas formation" (described in full by Cushman and McMasters, 1936, p. 497-517) for a middle Eocene unit, containing Domen- gine faunas, lying below the upper Eocene-Oligocene Sespe formation and above the lower Eocene-Paleoeene (Meganos stage) Santa Susana formation, exposed in Las Llajas Canyon, Simi Valley. "Domengine forma- tion" has been used in the present paper following Kew (Brown and Kew, 1931, p. 777-785, and Kew, 1943, p. 416). Distribution and Thickness. The Domengine forma- tion crops out over an area of about 1/10 of a square mile in Elsmere Canyon. The exposed thickness is about 650 feet but the beds are cut off by the Whitney fault on the east. Continental Oil Company's well Phillips No. 1, drilled in the Whitney Canyon area, 1.4 miles north of the Domengine outcrop in Elsmere Canyon, entered the Eocene (Domengine?) at a depth of 1,305 feet. Definite Domengine foraminifera were recognized at 1,404 feet, a continuous conglomerate zone extended from 2,787 to 3,356 feet, and from 3,520 to 5,280 feet the well penetrated lower Eocene rocks of the Capay stage. From 5,280 to 5,940 feet, lower Eocene-Paleocene rocks of the Meganos stage were recognized. Below that depth, in- determinate faunas and fault gouge were encountered • Information on Phillips No. 1 by written communication from Continental Oil Company, 1952. li)58] San Fernando Quadrangle — Oakeshott 59 until the well passed from sediincMits into weathered fiiieiss at 8,253 feet. From 5,940 feet to basement the sedimentary formations were considered as Eocene and Cretaceous undifferentiated.* A nnmber of wells in the Elsniere, Wliitney Canyon, and Plaeerita areas have encountered "Eocene" strata but the Continental well is of particular interest because of the complete test to basement and the comparatively p:ood fannal control. It is probable that Eocene and Paleoeene marine sedi- mentary rocks of Domenfrine, Capay, Me. Steeply dipping Oligocene ( ?) red Vasquez fanglomerate beds in upper Bouquet Canyon. 1958] San Fernando Quadrangle — Oakesiiott 61 logic breccias ('Oiitiiiniiig clasts several feet in (liaiucter. The general course of deposition of the Va.sque/, for- Very coarse clastic sediniejits, with marked angnlarity of mation was toward the west and in that direction the grain, and indistinct bedding, locally derived from the sediments tend to become less coarse, they thin notably, underlying crystalline rocks, make up a large part of more lake deposits appear, including borate- and gyp- the formation, aitiiough well-bedded, indurated, coarse- sum-bearing shale and sandstone, and the volcanics ap- grained sandstone and thin-bedded, lake-deposited shale pear to finger out into a series of thinner individual and siltstone are locally prominent. flows with more numerous interbeds of sediment. These rni , c ,.1 tT e t-„ „., ; + f „K^„+ westward gradational changes are generalized, as part The base of the Vasquez formation consists of about ,. ^i, tt ■ ^ ^ i ^- i • i- ^ i ,,, ,. ^ J, , ,• / . V, „i i„ „„„*„ 1., of the Vasquez is cut out, relationships are complicated 40 feet of coarse reddish-brown basal conglomerate made v ^u m- i /-i j \ir- ^ r< c ^^ i „ , , , 1 u u f *i „+ „ * „„„ bv the Tick Canyon and Mint Canyon fault zones, and up of pebbles and boulders of the quartz-augite sye- .; ^j j^ ^- ■ i j . ^i, m- i n f 1 ■ 1 ■- r uui e ■ \- 1 u;.*-t„ „„^ the Vasquez formation is overlapped by the Tick Can- nite on which it lies, pebbles of gnei.ssoid biotite niusco- ,\.. , ,, „ ,. *^'™v, i n ' J o ■, r I.U * J ™„ von and Mint Canyon formations. The following section vite granite as exposed 3 miles to the west, and numer- '• m- i /< j c ^ ^ v. ^^ ous boulders of anorthosite as exposed 3 miles to the f ^ick Canyon was measured from top to bottom south. The basal conglomerate dips 30° to 50° southwest. from^ plotted and adjusted mapping on aerial photo- It is overlain by some 400 feet of coarse reddish-brown ^ P ' sandstone with shale interbeds and minor lenses of con- TICK CANYON FORMATION glomerate of similar lithology to that at the base. This Angular unconformity is overlain by about 60 feet of very coarse fanglomer- VASQUEZ FORMATION ate \vith anorthosite boulders as large as several feet in Thickness diameter. The succeeding 3,800 feet consists of black- t. , , . . - , '" ^^'^^ and red-weathering basaltic volcanic rocks, largely flows, ^joCrllf S°"" ''' PO'Phynt.c basalt flows; dip ^^ some of which are highly vesicular, with amygdules of Thin-bedded HghT-col7r7d'and"higVl7ooTored're'd7browZ opal, chalcedony, and epidote. Textures are aphanitic i.ufE, and green sandstone, purpli.sh shale, borates, al- and fine-grained porphyritie. Thin beds of reddish- ternating varicolored shale and sandstone, minor con- purple breccia are foundnear the top of this sequence. A glomerate; average dip abont er," S 1,050 few thin sections of samples in the upper part of this Vesicular and amygdaloidal reddish ba.salt flows, red vol- d,. J i u u li ■ i- 1 1 came l)reccia and tnfr, thin interbeds of highly colored came section proved to be a basalt consisting largely sandstone and shale; near-vertical south dips 500 Ot acid labradonte (An 55), the phenocrysts showing Fine-grained red sandstone and shale lens 75 perfect zoning with the most basic feldspar about An Fine-grained black and red-weathering vesicular and 60, approximataely 5 percent ailgite which has been amygdaloidal l)asalt flows; near-vertical south dips -__ 1,300 Jiartly replaced by greenish and brownish hornblende. Approximately 800 feet of poorly sorted reddish fanglom- and a small proportion of interstitial, yellow-brown, de- '''■"'*■• "'""I'lers up to 1 foot diameter consisting of ■t -n A 1 rru it 1 ' i.- ti i gneissoid granite and darker dioritic rocks and vitrified glass. The textures are porphyritie, with great ^„^i^^^^. ,;„^„_ ^^,,_ ,,,,,, ^^.^^ ,andstone, greenish variation in the proportion of phenocrysts; phenocrysts sandstone, minor amount of shale; Imrate-bearing are less than 2 millimeters long, and feldspar microlites shales near top; near-vertical to north dips (over- in the groundmass show a pilotaxitic arrangement. turned) 1,1.50 Euhedral augite makes up a small proportion of the ... ^ , I „ „ . 1 ii • .• ii t. £ ii ■ • Prohahle fniilt (Mint Canyon) phenocrysts. A thin section near the base of this series „r? fl„ 1 i -J i' 1 -ii, iu i J 'u J Buff-weathering gneissoid granite of flows was almost identical with that described. Total thickness of volcanic rocks 2,100 On top of the volcanics in Escondido Canyon is a Total thickness of sedimentary rocks 2,275 very well-stratified 4,500-foot section of buff, yellowish- T^^^,, thickness of Vasquez formation 4,.375 gray, and coarse reddish sandstone, with conglomerate and shale interbeds^ the sandstone is continuous with ^ 100-foot section of varicolored thin-bedded alter- the prominent outcrops of Vasquez Rock. The highest „ating sandstone-shale-mudstone, newly exposed (1954) beds in the Vasquez section are dark red, coarse sand- j^ ^ Davenport Road cut half a mile east of Tick Can- stone and shale, overlain unconformably by the ex- yo^, near the top of the Vasquez formation, was checked tremely coarse fanglomerate of the Mint Canyon forma- fo,. gojor against the Rock Color Chart (National Re- tion at Agua Dulce Canyon. About 1,000 feet west of search Council, 1948). The following colors were found: Agua Dulce Canyon, and 500 feet stratigraphicallj' be- dORfi/'') low the base of the Mint Canyon formation, is found a Light'"greenish-gray (5GY 8/) bed of pink lithic tuff a few feet thick. The abundance Light gray (N 7) of large angular to slightly rounded boulders of anortho- Yellowish-gray (5Y 8/1) site, granite, gneissoid granite, and syenite in this section Morgue y'ellowL^brown (lOYR 5/4) indicates that the Vasquez sediments were derived b.y the Light brown (5YR C/4) rapid erosion of steep exposures of these rocks cropping Pale grayish-orange (10YR8/4) 1 • *i o r- u ■ 1 Tv^ t • ^x, X Dusky red (5R 3/4), on fractures out, as now, in the ban Gabriel Mountains on the south aiedium ligh. gray (N 6) and the Sierra Pelona on the north. Just a mile east of Pale red (5R 6/2) the quadrangle, basal fanglomerates of the Vasquez for- Selected shale beds of this unit are being mined by the mation contain many boulders of the quartz diorite in gie^-a Pelona Rock Company to produce four natural place on Parker Mountain. The Vasquez sediments were colors of roofing granules— " pastel green, kelly green, here deposited in a narrow basin flanked by steep moun- burgundy, and gold" (see section on Economic Geology, taiuous topography on three sides, flaring to the west. under roofing granules). 62 California Division of Mines [Bull. 172 i^*S ^4^^ ^v-^, ^H-P^i*^ -^ .<«•■ Photo 46. Loosely consolidated unsorted gray fanglomerate of Vasquez formation, eon.sisting wholly of granitic detritus, exposed in Bouquet Canyon at Texas Canyon. Vasquez fanglomerate crops out in a block about 3 miles wide between the Pelona fault zone and the pre- Tiek Canyon-formation fault in Vasquez Canyon. This block extends northeast to cover about 5 square miles in Elizabeth Lake quadrangle and has been described by KSimpson (1934, p. 392-393). Only the upper 1,000 feet of the Vasquez formation of this area is exposed in San Fernando quadrangle. It consists of unsorted fanglomerate made up of completely angular fragments ordinarily a few inches in diameter but locally, as in lower Texas Canyon, of such great size as to simulate fractured granitic rock in place. The breccia is essen- tially monolithologic, consisting almost entirely of gneiss- oid granite, porphyritic biotite granite, biotite quartz monzonite and the granitic rocks on which the breccia was deposited. Simpson (1934, p. 393) called attention to the absence of Pelona schist clasts in the fanglomerate. Although this is generally true, the upper part of the Vasquez fanglomerate north of Texas Canyon contains a few boulders of dark porphyroblastie gneiss and un- determined schist debris which may have been derived from the Pelona. A mile due west of Bouquet Canj'on the Vasquez formation, in doubtful fault contact with granitic rocks, seems to be made up exclusively of Pelona schist fragments, including ehlorite-actinolite schist, metaporphyritic rocks and dark brown and black quartz- ites. There is a possibility that this poorly exposed frag- mental Pelona schist is not detritus in the Vasquez for- mation but is a small block of Pelona in the Pelona fault zone. Stratigraphic Relationships. In most places in San Fernando (luadrangle the lower part of the Vascjuez formation is in fault contact with granitic rocks, but in several places in the northeastern corner of the quad- rangle the basal Vasquez fanglomerate lies uneonform- ably on syenite and related hornblende diorite, both of probable Tipper Jurassic or Ijower Cretaceous age. This contact is exjjosed just north of Eseondido Canyon Road 1 mile east of Elkhoi'u Lodge. The Vascpicz formation is unconformably overlain by the Tick Canyon formation and by the Mint Canyon formation. The marked angular unconformity between Tick Canyon and Vasquez forma- tions is best seen on the west side of Tick Canyon where Photo 47. Reddish-brown unconsolidated fanglomerate of Oli- gocene ( ?) Vasquez formation, consisting wholly of granitic detritus, Te.xas Canyon. basal conglomerate beds of the Tick Canyon formation overlap, from east to west, the upper volcanic member and upper sandstone-shale member to lie on the lower volcanic member of the Vasquez formation. Dips in the Vasquez beds are over 55° S. ; the overlying Tick Canyon beds dip 18° to 40° S. and W. Basal Tick Canyon beds commonly contain a noticeable amount of volcanic debris from the Vasquez formation. The angular unconformity between the Mint Canyon and Vasquez formations is well exposed in the first can- yon west of Agua Dulce Canyon where very coarse Mint Canj'on fanglomerate striking northeast and dipping 22° NW lies on well-stratified Vasquez beds striking nearly due north and dipping 35° W. The Mint Canyon fan- glomerate includes pebbles of Vasquez volcanics and sandstone. Age and Correlation. Positive evidence of the age of the Vasquez formation is lacking as no fossils have been found in it. However, the unconformably overlying Tick Canyon formation contains an abundant vertebrate fauna of Arikareean age (late lower Miocene, Durham, Jahns and Savage, 1954) which has been described by Jahns (1940). Although only the crystalline rocks are found below the Vasquez formation in San Fernando quadrangle, the Vasquez unconformably overlies the fossiliferous Paleocene Martinez formation in Tejon quadrangle on the west (Clements, 1937, map showing "Sespe, " p. 216-217). Elsewhere in the extreme eastern Ventura basin, the highest Eocene marine sediments are of mid- dle Eocene (Domengine) age, as in the Placerita oil field (see section on Domengine formation, this bul- letin), and in the Sespe Creek area where the middle Eocene Llajas formation (McMasters, 1933) is overlain unconformably by the nonmarine Sespe formation which has yielded some vertebrate fossils. Thus, the probable lower age limit of the Vasquez formation is upper Eocene. It is most likely that the Vasquez formation is essentially equivalent to the Sespe formation of the type locality and should be placed between the age limits of upper Eocene and lower Miocene. i!)r)8i San Fernando Quadrangle — Oakesiiott 63 Tick Canyon Formation Name and Type Localitji. The lowest few liuiidrcd foot of the Mellenia series of liersliey (lf)()2e) and of the Mint Canyon formation of Kew (1924b) were desig- nated the Tick Canyon formation by Jahns (1939) on tile basis of a vertebrate fauna distinctly older than the faunas of tlie overlying Mint Canyon strata. The new formation name was used (Jahns, 1939) because of good exposures in Tick Canyon but the type locality was later selected and a section measured a quarter of a mile southeast of upper Vasquez Canvon (Jahns, 1940, p. 152 and 154). Distribution and Thickness. The Tick Canyon for- mation is exposed in a narrow band 2 miles long between Texas and Mint Canyons, and in a separate area extend- ing approximately a mile both east and west of Tick Canyon. These two areas nia.v have initially been basins of Tick Canyon deposition separated by the granitic high between Mint and Vasquez Canyons. Maximum thickness measured by Jahns (1940, p. 162-163) was 593 feet. The formation thins westward and is appar- ently overlapped completely by the Mint Can.yon for- mation just before reaching lower Texas Canyon. In a late map of the Soledad basin, Jahns and Muehl- berger (1954) show an area of Tick Canyon formation approximately a mile wide, dipping 25° to 30° W., be- tween Spring and Agua Dulce Canyons. This would increase the maximum thickness of that formation to over 2,000 feet. The present author mapped this as lower Mint Canyon formation but found no fossils to substan- tiate it (see section on Mint Canyon formation).* Lithology. The Tick Canyon formation consists of fluviatile and lacustrine reddish sandstone, siltstone, and claystone, and gray, tan, and reddish conglomerates, well cemented and well stratified. In the type locality the basal fanglomerate, approximately 100 feet thick, consists of grayish to buff, poorly sorted and loosely consolidated fragments of various sizes up to a foot or more in diameter. Most of the clasts consist of the under- lying gneissoid granite and biotite granite, purplish vesicular volcanic pebbles derived from the Vasquez formation, and some anorthosite. The basal member is overlain by reddish sandstone, mudstone, and siltstone, with some interbedded yellowish and green siltstone and thin interbeds of conglomerate. Some of the volcanic pebbles in the conglomerate beds are rock types, not found in the Vasquez formation, that may have been derived from the Mojave Desert area on the north. Stratigraphic Relationships. The Tick Canyon for- mation lies unconformably on Upper Jurassic (?) or Lower Cretaceous (?) gneissoid granite across Va.squez Canyon and, west of that canyon, was deposited across the Vasquez Canyon fault and on the eroded surface of the Vasquez formation. The author believes the south- eastern half mile of this contact southeast of Vasquez Canvon to be a near-vertical fault. Angular discordance • In a letter dated August 1. 1955 Jahns indicates that he and MuehUierger now have fossil control to indicate that "at least half of it is Tick Canyon" although they have not been able to nx a Ticl< Canyon-Mint Canyon contact. Concerning the appar- ent thickness of tlie Tick Canyon formation between Spring and Agua Duke Canyons, he says that "900 feet is tlie maximum thickness of what I consider to be demonstrably Tick Canyon, whereas the thickness in that one area might be considerably greater than this ; the much greater thickness, though, remains to be demonstrated." between the Tick Canyon and Va.squez formations in upper Tick Canyon is at least 15° (see section on Vas- (|uez formation). Thus, the Vas(|uez formation was mildly folded, faulted, and eroded before the Tick Can- yon sediments were dejxjsited, a more important hiatus than that between deposition of the Tick Canyon and Mint Canyon formations. Mapping shows that the Tick Canyon formation is overlapped, both westward and eastward, by the Mint Canyon formation but without much angular discordance. On the Mint Canyon-Kscon- dido Canyon road a quarter of a mile west of Tick Canyon, coarse, gray, lower Mint Canyon conglomerate dipping 20° W. lies disconformably on lacustrine red and grayish shale and siltstone of the Tick Canyon formation. Age and Correlation. Jahns (1940) has fully de- scribed collections of vertebrate fossils from the type locality (his map op. p. 154) of the Tick Canyon forma- tion which quite definitely indicate "late lower Miocene or possibly earliest middle Miocene" age. He has listed and described the following forms (1940, p. 174) : Kodentia lleteromyid. jiroli. n. sen. and sp. Arvhueolagus (?) .sp. I'eri.ssodactyla Parahippus nin.inoiii n. sp. Artiodactyla Merychyus ciilnminthus, n. .sp. Miolahi.'i caHfornirits Max.son Savage, Downs, and Poe (1954, p. 45) have this to say about the Tick Canyon fauna: "Not far from Newhall and Sau^us, in the ea.stern part of tlie Ventura basin in Los Angelps County, lies the Tick Canyon fornia- tiim. The liones discovered in these deposits were tantaliziriKly few, liut pocket mice, rabbits, Parahippus (a moderate-sized browsiiif;- KraziuK horse), Meryrhyus (slender-limbed oreodonts), and cam- elids were there. One species of bird from the Tick Canyon forma- tion in Vasquez Canyon is Miohierax stocli Howard, a hawk. Thi.s is the earliest well-pre.served specimen of liird thus far known in the State, although an unidentitiable bird bone is known from the mid-Eocene of the Mt. Diablo district in northern California. These vertebrates are dated as late ARIKAREEAN (early Mio- cene) or early HE.MINOFOKDIAX (early mid-Miocene). The horse and the slender-limbed oreodont had teeth better adapted for grazing than their earlier relatives; this suggests that more grasslands e.xisted, perhaps as broad divides between wooded streams." Pale red, reddish-brown, and yellowish-brown, non- marine arkose, mudstone, and conglomerate, interbedded with basalt flows in the Pacoima Hills and Verdugo Mountains, lying below the Modelo formation, have been mapped as the Topanga (?) formation. This unit on the northern margin of San Fernando Valley, is a possible correlative of the Tick Canyon formation in San Fer- nando quadrangle. Topanga (?) Formation Name and Type Locality. The Topanga formation was named and defined by Kew (1924b, p. 47-48) from its oc- currence in the vicinity of Topanga Canyon in the Santa Monica Mountains. Closest occurrence to the San Fer- nando quadrangle was mapped by Kew in the Santa Susana fault zone 4 miles west of San Fernando Reser- voir. Hoots (1930) described the type Topanga in con- siderable detail. In the type locality the formation is 64 California Division of Mines [Bull. 172 predoniiiiaiitly shallow niariiic sandstono, coiif^lomerate, and slialo, witl: oxtr\isivi' and iiitnisivo basalt, but with red c-diifiltiiiicralc locally at the base. The fonnatioii ovor- lies Va(iuer()s (?) ami Scsjio ('0 i'onnations and is unconformably overlain by the Modelo formation. Distribution arid Thickness. In San Fernando quad- rangle coarse reddish and yellow nonmarine arkose, eon- glomerate, and thick interbedded flows of andesite and basalt, and coarse marine sandstone, comprise a unit questionably correlated with the Topanga formation. Topanga ( ?) sediments and basalt flows are well exposed ill the Pacoima Hills and in the Verdugo Mountains southwest of Sunland, and Topanga basaltic volcanic rocks are exposed at Tujunga and north of the Sunland fault between Little Tujunga and Big Tujunga Canyons. Thickness in the Pacoima Hills is approximately 1,000 feet, of which vesicular basalt flows constitute 450 feet. Thickness of the basalt north of the Sunland fault is 300 feet. In both areas, the basal Topanga ( ?) has been cut out by faulting. Standard Oil Company of California well Woo 1, about 4 miles west of Pacoima Hills, pene- trated 125 feet of fragmental altered basalt immediately above the middle Miocene Topanga formation, and about 4 miles wTSt of Woo 1, Richfield Oil Corporation well Mulholland 1 penetrated 400 feet of massive basalt as- signed to the middle Miocene Topanga formation (Shel- ton, 1955, Table 1, p. 50-51). Lithology. The Topanga (?) formation in San Fer- nando quadrangle consists of coarse reddish and yellow- ish arkosic sandstone, mudstone, and conglomerate and a large proportion of interbedded vesicular basaltic flows and minor reddish-purple breccia. The thin exposure of typical Topanga (?) "red" beds at Green Verdugo Reservoir in the Verdugo Mountains show the pre- dominant colors to be pale reddish-brown, pale red, and light red, with interbeds of very pale orange. Pebbles in the Topanga ( ?) conglomerate are well rounded and are commonly granitic rocks in a reddish arkosic sandstone matrix. Best section of the formation is exposed in the Pacoima Hills, where the coar.se reddish sediments ap- pear above, below, and as lenses between, beds of red- weathering dense basaltic flows and thin beds of coar.se reddish volcanic breccias. The lower 800 feet of highly colored coarse sediments and volcanics appears to be non- marine, but the top 200 feet of light yellowish-gray medium-grained sandstone carries ca.sts of poorly pre- served marine pelecypods. A few specimens of dark purplish-brown highly ve- sicular flow rock examined from the Pacoima Hills proved to be a rock on the borderline between andesite and basalt. Numerous small (less than i millimeter long) phenocrysts of acid labradorite (An 52) are roughly oriented in flow lines in a trachytic groundmass of andes- ine (about An 40) microlites with about 10 percent cloudy devitrified glass. The only ferromagnesian min- eral recognized was a small amount of biotite. North of the Sunland fault, black compact vesicular basalt with no visible phenocrysts is in a series of flows alternating with beds of coarse reddish-brown breccia. Similar ex- posures are found on Hill Rose Street in the town of Tujunga. Epidote, chalcedony, and zeolites were ob- served in some of the vesicles. None of the andesite- basalt could be priivcn intrusive. althoni;li there may be sonic thin sills. In contrast to some of 1 lie basaltic Hows in the Santa Monica Mountains, volcanics of the Topanga(?) forma- tion in San Fernando l. C.I.T. 461 — 0.7 mile ESE of the intersection of Van Xuys Boule- vard and San Fernando Road (U. S. Hwy !•!•) in I'acoinia, I>os Angele.s County : 750 ft. N74° W of B.M. 1302, I'acoima quad. (19l!7; 1 : 20.000). On the W face of the hill E of I'acoima. The jaw fragment was taken from arkosic sandstones and red inudstones that overlie the "basement" granodiorite in this district. The jaw is comparable to the Merychyua oreodonts from the Tick Canyon fm. or from the lower Caliente fm. — Caliente Mountain local fauna ( Hemingfordian = mid-Miocene). Additional work in tills district nuiy provide a tenable correlation between early to mid-Miocene marine and nonmarine formations in southern Cali- fornia. Shelton (1955, table 1, p. 50, 51) has placed the Topanga(?) volcanics in two wells in western San Fer- 19081 San Fernando Qiiadrangle — Oakesiiott 65 iiando Valley in tiie middle MidciMio. Tlireo wells (Oeeiiiiic Oil Company DeiMille 1 and DuRois 1, and Inlex Oil ("ompany Toon 1) within a radius of 2 miles north i'rom the I'aeoinia Hills ])enetraled the Mcxh'lo formation from Mohnian into Luisian (late middle Mio- cene) beds without reaching the Topanf>:a(?) volcanics. The stratigraphic and age relationships indicated in San Fernando quadrangle, as well as lithologie eharac- teristies, are quite consistent with eon-elation of the San PVrnando Toj)anga( 1) formation with the type Tojianga a few miles south in tlu' Santa IMoniea Mountains. The Topanga(?) may be an age equivalent, in part, of the lower i)art of the Mint Canyon or the Tick Canyon for- mation north of the San Gabriel fault. Mint Canyon Formation Name and Type Localifji. The name Mint Canyon formation wa.s given by Kew (1923, p. 411-420, and 1924b, p. 52-55) to a unit previously described by Her- shey (1902e, p. 356-358) as the Mellenia series, consisting of .several thou.sand feet of nonmarine sedimentary rocks unconformably overlying the Vasipiez formation (Kew's Sespe ( ?) ; Hershey's Eseondido series) and uneonforni- ably overlain by the mariiu> Modelo (Modelo (?) or Castaie) formation. Type locality is in Mint Canyon. Jahns (1939) separated the lowest few hundred feet of this unit, on the basis of an unconformity and distinctive vertebrate fauna, as the Tick Canyon formation and redefined the remaining upper part as the Mint Canyon formation. Durham, Jahns, and Savage (1954, fig. 3 on p. 62, and p. 66-67) have recently divided the formation into a "Lower variegated member" and "Upper gray member" with vertebrate faunas of ditferent ages. Distribution and Thickness. The Mint Canyon is the most widely distributed formation of the Soledad basin, covering roughly 45 scjuare miles of the northwestern and north central part of San Fernaiulo quadrangle. It lies in the southwest-plunging folded and faulted syn- eline which is bounded on the north, east, and south, respectively, by the Sierra I'elona, Parker Mountain, and San (labi'iel Mountains. Ontei'ops of the formation ex- lend about 8 miles northwest of the noi'thwest corner of San Fernando ciuadrangle, as siiown on the recent map of the Soledad basin by Jahns and Aluehlberger (1954). Thickness of the Mint Canyon formation measured by Jahns (1940) from the base of the overlying Modelo formation in Bouquet Canyon to the top of the under- lying Tick Canyon formation in Vas(|uez Canyon was 4,044 feet. This is the least faulted, most complete sec- tion, but probabljf does not represent the maximum thickne.s.s as it is apparently a short distance northwest of the center of the Mint Canyon basin. Jahns and Muehlberger (1954) show a maximum thickness of 1,900 feet for the Lower variegated member and 2,600 feet for the ITpper gray member, or a total maximum thickness of 4,500 feet for the Mint Canj-on formation. Litholo;/)/. The Mint Canyon formation is composed of a variety of fine- to coarse-grained more or less well- consolidated nonmarine sediments of fluviatile and lacus- trine origin. The sediments were chiefly derived from locally high-standing mountainous ai'cas of the Sierra Pelona and San Gabriel but a suggestion of some through drainage from the Mojave Desert block on the north is found in a small percentage of volcanic pebbles of Mo- jave types found in Mint Canyon conglomerates. The sediments were dejiosited in broad valleys, flood ]ilains, and small intermittent lakes across folded and faulted strata of the Vasquez formation and the marginal crys- talline rocks of the Soledad basin. A broad two-fold lithologie division of the Mint Canyon formation into upper and lower members has been suggested by Kew (1924b, p. 52), Maxson (1930, p. 81), and Jahns (1940, p. 154). Jahns and Muehlberger (1954), in a recent resume, made a separation into a Lower variegated member and an Upper gray member but did not dis- tinguish them on their map; Durham, Jahns, and Savage (1954, p. 66) have called attention to work in progress msS I'ilOTO 4S. Vii'w r:i,s| friini imrtli piid of Piickeft Mcsii. acm.s.s ni'iitl.v ilipiiiiiK licd.s iif the Mint Canyon fornnitidn in f(irp},'i'ouii(l, toward Vastiuez formation and granitic rock.s at crest, and Sierra IVlona in far distance. 6(5 California Division op Mines [r.nll. 172 I'UOTO 40. I,(iiisply ooiisiili(l;it('(l chniactci'istio I'cddish-hrowii I'llOTO 50. Pomly bedded, poorly sorted lias;il red lied.s of ^lie lirecciii of the hasal jiart of the upper Miocene Mint Canyon forma- tii)i)er Miocene Jlint Canyon formation. Sand Canyon road in lower tion nesir junction of Sand Canyon and Hear Canyon. I'.ear Canyon. Oil di.stiiK'tive vertebrates found in these two members. Percent The terms "lower and upper" Mint Canyon in the fol- Gai.hroic rocks 30 , . ,. . '' 1 11 !■ i-.,i 1 • \olcanic rocks (\asquez.') 19 lowiiig discussion are used very broadly for lithologie y,,,,,^^ monzonite-granodiorite 11 variations and are not meant to define members. (iranite 11 „, , , p ., -.r- . ri Q 1- -4 I'cuphyritic rhyolite (?) 10 The lower part ot the Mint (_anyon rormation consists Metavolcanic rocks 8 of hifihly colored, poorly sorted, fiiie-firained to ex- Anorthosite 7 treinely coarse sediments iiicludiii 4. '^ ' f <^ >>~ i^j) I- >-.' quo'A tormation. It has recently been described by Pat- lu Sand Canyon and its tributaries — Gorman and chick ( 1954). The author believes it is probably part of Bear Canyons — lower Mint Canyon beds consist of a the lower Mint Canyon formation, its present position maximum thickness of 1,100 feet of reddish-brown and explainable by an apparent left lateral movement of light brown poorly .sorted, but distinctly stratified, con- 1.7 miles along the Agua Dulce fault. It consists of glomerate with lenticular interbeds of coarse sandstone and mudstone, lying on Mendenhall blue quartz gneiss and locally faulted against gabbroic rocks. The dominant '■-i=Ik^?' * ;^' ..". ' . ---t. -'. conglomerate beds are made up of angular clasts from ^^p>-^-' .■*^'^-« T^r-'-^.^'?^ sand-grain size to over a foot in diameter. Crossbedding, ^a^ ^■^kl' •^- " lenticularity, and sorting are characteristic of stream ^^v - ^ J'-"'^'^!^'* deposition near a steep mountain front. Clasts consist li?^-^ ' '*^^ -'^•'''*-^''" ' entirely of the underlying gneiss and gabbro complex. ^^^A—^ ■•^y*^'** " ' ' ' ■ The coarse lower unit is overlain by thin-bedded bro-wn- -^"'8^'^%^^^'' ish and greenish siltstone, and interbeddcd tuff typical ,-»^i^w' -'^'' of njjpcr Mint Canyon beds. ^^»?« ?- ^•iA. Basal Mint Canyon beds between Sand Canyon and !|iiri?H. ^^SB I;ang, Ij'ing on and faulted against gabbroic rocks, con- . ~' — " sist of coarse reddish-brown poorh- sorted pebbly sand- stone and conglomerate, clay and mudstone, and basal ^ <>« dark brown breccia, all very lenticular and crossbedded. * — ' - " . . ^.„ _ . -,1.,^ -.. '.. '. »J In some places the basal bed is very calcareous and con- Photd .".l. Mint Canyon formation on Sand Canyon road near tains remains of minute freshwater gastropods. A pebble *'■"' Cany.m. Crayi.sh cros.s-lu'dded couKlomerate, very coarse „„, 4. • ii 11 1 4 1 n' -1 ii sandstone and thinner sandy mudstone; tvpi<':il of thick section count m the near-basal conglomerate halt a mile south- „f jii,,^ ^.„„y„„ f,„,,„„i„„ :,; ,1,1.. ,,.f;i,u,. Keddin,- does not appear west of Pole Canyon follows: except in the road cut. 18| Sax Fernando Quadrangle — Oakeshott 67 •iraiiis, iK'hblrs. ami aiifriilar boulders as large as several feet in diameter which are almost entirely white and purplish anorthosite, frabbroie rocks, granitic rocks, and ^neissoid hornblende ((uartz diorite (of Parker Moun- tain?). Pebbles of the V'asciuez volcanics appear strati- firaphically hifiher in the section. The detritus is mas- sive, ]i<)(>rly stratified, and not well sorted but is well cemented. Local derivation from hig:h-standini>' moun- tains on the south and east is indicated, with deposition on the marp-in of the Soledad basin as alluvial fans, debris flows, and stream deposits. In Agna Dulee Canyon, three-quarters of a mile north of Apna nulce fault, the basal Mint Canyon formation, lying unconformably on well-stratified reddish sandstone and shale of the Vas((uez formation, is an extremely coarse unsorted faufilomerate with boulders as large as o feet in diameter. The clasts consist of granitic rocks, anorthosite, gabbroic rocks, and fragments of volcanic and sedimentary I'ocks from the underlying Vasqnez formation. West of Mint Canyon, the lower part of the ]\Iint Can- yon formation contains none of the very coarse fanglom- erate .just described, bnt is characterized by better stratification, generally finer-grained sediments, and prominence of highly colored strata. About 100 feet of reddish-brown basal conglomerate, rich in angular slabby clasts of Pelona schist and fragments of gneissoid biotite granite, with lenses of coarse arkosic sandstone, lies on the Tick Canyon and Vasqnez formations. However, in the extreme northwest corner of the San Fernando quad- rangle, basal Mint Canyon lying unconformably on Pelona schist is composed of brown friable medium- to coarse-grained sandstone which contains grains of Pe- lona schist, and lenses of coarse calcareous sandstone. The upper part of the Mint Canyon formation con- sists of a predominance of light-gray conglomerate and greenish-gray coarse sandstone of fluviatile origin, thin- bedded lacustrine siltstone, sandstone, conglomerate, and a series of volcanic tuff beds. In contrast to the lower Jlint Canyon, upper Mint Canyon strata are character- istically gray instead of reddish-brown, contain a much higher proportion of lacustrine beds, are marked by a series of discontinuous white tuff beds, and lack the very coarse breccias of the lower part. Thin, highly colored beds are present in the upper Mint Canj'on but are not dominant. *;..V .d^^^^^r' >' tfl"^.'- riKiTo ."i2. Vifw iKiitluvfst iioross Mint (';in.v.in frcim Sand Can.von road. Puckett Me.'ia in the distance is underlain In gently west-dipping beds of the upper Miocene Mint Can.von formation. I'HOTO 'i',',. t'oarse sandstone and );ravel of ttie upper .Miocene Mint Can.von forni.ition dipping gently northwest away from the camera ; Solamint. The section of the Mint Canyon formation, from its top in BoiKiuet Canyon to its base in Vascjuez Canyon, measured by Jahns (1940, p. 155-162) indicates the lithologic differences between the upper and lower parts of the formation. If Jahns' members 1 to 9, totaling 2,055 feet in thickness, are taken as comprising the lower part of the Mint Canyon formation, then 32 percent is siltstone, clay, and shale ; 59 percent is sandstone and 9 percent is conglomerate. Considering Jahns' members 10 to 27, totaling 1,989 feet in thickness and .starting with the lowest tuif bed, as upper Mint Canyon, then 54 percent (including li percent tuff) is siltstone, clay, and shale, 29 percent is sandstone, and 17 percent is conglomerate. Thus, relatively coarse sediments make up 68 percent of the lower part and onlj- 46 percent of the upper part of the formation. Typical thin lacustrine and fluviatile beds are ex- posed on and near Sierra Highway (U. S. 6) south of Solamint. inchiding brown shale, thin-bedded light brown sandstone, white vitreous tuff, light brown pebbly sandstone and conglomerate, greenish-gray sandstone and siltstone, yellow-gray calcareous sandstone, and gray sandstone and siltstone. Several of the fine-grained and calcareous beds contain numerous small gastropods — Paludestrinu imitator Pilsbury. Artificial cuts along the Soledad Canyon Road and Southern Pacific Railroad from Solamint to Lang have exposed west-dipping beds of the upper Mint Canyon formation which cover the wide area of the central por- tion of the basin of deposition of the Mint Canyon for- mation extending from Soledad Canyon northward about 3 miles and westward from Spring Canyon across Mint Canyon. Light-gray conglomerate and coarse light-gray and greenish-gray .sandstone, crossbedded and lenticular, is the most common lithologic type. Exposures of this facies are poor, except for local areas of badland topog- raph}' and artificial cuts; elsewhere the low hill-and- valley surfaces are covered with pebbles and cobbles, but attitudes and structure are not clear. The pebbles and cobbles include large proportions of granitic rocks, anorthosite, gabbroic rocks, and locally, volcanic detritus derived from the Vascjuez formation, and fragments of Pelona schist. The sediments are loosely con.solidated to well cemented, depending on the proportion of calcare- 68 California Division' of Mines (Bull. 172 Photo r>4. View N. 20° W. from noith end of I'lickett Mesa. White sandy tuff l)efl dippiiiK southwest forms narrow rid^e in left center. ous cement in individual beds. Lentieularity of beds and rapid gradations in lithology along the strike as grada- tional changes from fluviatile to lacustrine, stream chan- nel, flood-plain, and debris-flovv or landslide sediments take place have made it impossible to follow and map continuous units. Correlations across the Mint Canyon basin, therefore, cannot be accurately made. White volcanic tuff beds occur at several horizons in the upper half of the Mint Canyon formation through a stratigraphic thickness of approximately 1,800 feet. Most of the tuff beds appear in two areas, the Bouquet Canyon region, and 5 miles to the south in the Sand Canyon area. Kew (1924, p. 53) recognized two zones of lenticu- lar tuft'aceous material southeast of Bouquet Canyon. In the Mint Canyon section, from Vasquez Canyon to Bouquet Canyon, Jahns (1940, p. 155-156) recognized 10 horizons of crystal and vitric tuff, each 1 to 4 feet thick. Wallace (1940), in a detailed unpublished study of the tuff beds of the Mint Canyon formation, recognized the presence of "at least 8 major tuff beds and as many as 5 minor ones." Only the most prominent and continuous of the tuff beds are shown on the accompanying geologic map of San Fernando quadrangle (pi. 1). The tuffaccous beds range widely in composition, in- cluding nearly pure vitric tuft' with a few grains of quartz and fcidspar, fine porcelaneous tuff, coarse sandy tuffaceous sediments, ash, crystal tuff and lithic tuff'. The tuffs show very little alteration except for the de- velopment of secondary opaline silica in some porcelane- ous beds and the development of some clay minerals. Wallace (1940, p. 43) found indices of the glass shards to be close to 1.50, corresponding to about 70 percent silica. Evidence of shallow fresh-water deposition of the tuffaceous beds and enclosing sediments is quite conclu- sive. Ripple marks, small-scale cross-bedding, lamina- tion, the fresh-water gastropod Paludestrina imitator Pilsbury, fresh-water pelecypods including Aninicola sj)., ostracods, and fossil leaves are found at various horizons. Individual tuff horizons can rarely be traced for more than a mile or two, disappearing along the strike by thinning in some places, but very commonly by grada- tion into sandstone. The tuff beds of the Bouquet Can- yon area and of the Sand Canyon area could not be cor- related across the intervening 5 miles of the synclinally folded Mint Canyon sediments; there is no evidence that any of the tuft' beds is continuous fi'om Bontpict Canyon to Sand Canyon. Wallace (1940, pp. 17-19) reported the identification of the following 15 plant species by D. I. Axelrod from collections made by J. II. Maxson, W. II. Ilolman, and R. E. Wallace, mostly from the tuff' (piarry west of Sand Canyon (localitj' va 82 on pi. 2). Ceannihus precuneaiim Axelrod Ceiinothus n. sp. Cerorarpus cunciitiis Uorf CroKsononia n. sp. Jiionftiffos n. sp. Fnij:inun ctlcnsis Axelrod FrP)iioniiii lohatii A.xelrod J/i/onnlhitmim wnhnroisis Axeinxi Mithoiiia niohitrcmiis Axelrod I'Idtiniiis pnudirintiile I>orf Quercits conrcj-a Le.squereiix Qiterrus dispersa (Tjesq.) Axelrod Querrii.i Itikevillrnsin 1 >orf Rhus ,vo/(o?'f /f«i.x Axelrod liohinia California Axelrod Quoting Axelrod (Wallace 1940, p. 19-20): "The Mint Canyon flora is an integral part of the arid north Mexican vegetation that characterized the Mo.jave area in middle Miocene time, and which, by the end of the epoch, had migrated westward into .southern and central California, northward through the Creat Basin, and eastward into the High Plains." "The flora is essentially an oak savanna community whose nearest related modern equivalent species now occur in southern California, southern Arizona, and northern Mexico. At least four habitats contributed to the flora, lake-border and riparian, savanna, woodland and chaparral. The Mint Canyon climate was largely similar to the present conditions in the region, but (littered in having a biseasonal distribution of rainfall and winter temperatures which niav have been slightly higher." The Mint Canyon rhyolitic tuffaceous sediments were deposited in small discontinuous ejihemeral .shallow lakes which developed from time to time on the Hood jilains of the Mint Canyon basin. There is no evidence of any local vents but numerous centers of Miocene rhyolitic volcanism existed in the Mojave Desert area. Stratigraphic Relationships. The Mint Can.von for- mation is overlain unconformably by the marine Modelo formation. A few feet of cobble conglomerate forms the base of the Modelo formation overlying the Mint Can- yon exposed in Bouquet Canyon near the western border of the quadrangle; angular discordance is only a few degrees but is readily observed and appears in mapping. In the Sand Canyon-Reynier Canyon area a similar relationship exists but angular discordance is much greater and a prominent tuff bed in the Mint Canyon formation is nearly overlapped by the Modelo formation. Lower Mint Canyon fanglomerate and schist breccia lie unconformably, but with slight angular discordance, on the Tick Canyon formation and overlap it to lie on the Vasquez formation with marked angluar discordance along the northern and eastern margins of the sedimen- tary basin (see sections on Vas(iuez formation and Tick Canyon formation). In two localities Mint Canyon beds lie luieonformablv on basement rocks — Pelona schist and 1 f)r»8 1 San Fernando QrAOKANOLE — Oakeshott ()!) friu'issoid ;;raiiiti' — in the nortlnvestcni ((irncr of the (|iia(iraiitrl('. and dark f:al)broic rocks abont '2 miles sonfh of Lanjj. Ayr and VdrrvUituin. Tlio first definite evidence of the atre of the Mint Canycni formation was presented by Kew (1924b. j). 54) who eaUed it npper Miocene, based on a statement on the vertebrate fossils by Dr. Chester Stock, and stratifrraphic position below late Miocene marine beds. Maxson (1030) described the Mint Canyon fanna and considered it npper Miocene. Stirton (1933, VXV^^ critically reviewed the fauna and called it Claren- donian (lower Pliocene). Jahns (l!)3n, 1940) separated the Tick Canyon formation from the lower part of Kew's Mint Canyon, discussed its middle to lower Mio- cene fauna, and reviewed the problem of a Biotitp granodiorite and quartz monzonite 66 Diorite gneiss 10 Vesicular andesite or basalt (Topanga ?) 11 Metavolcanic rocks 4 100 In the Paeoima Hills, basal beds of the Modelo forma- tion, consisting of yellowish-brown or buff sandy shale, fine sandstone and coarse sandstone, lie disconformably on light j-ellowish-gray medium-grained fossiliferous sandstone of the Topanga { ?) formation. In the road cut at the west end of Hansen Dam, the fine to coarse Modelo sandstone beds carry three beds of grayish-white volcanic tuff, each 1 foot to 2 feet thick. Four miles farther east, at the new Green Verdugo Reservoir of the Los Angeles Department of Water and Power in the Ver- dugo Mountains, the base of the Modelo formation is exposed lying directly on reddish-brown vesicular basalt and thin pale reddish-brown and pale orange sandstone beds of the Topanga ( ?) formation. The basal Modelo consists of extremely coarse poorly sorted thick-bedded conglomerate of a prevailing pale yellowish-brown color. Subrounded boulders range through all sizes, to 3 feet in diameter. A pebble count shows the following pro- portions : Biotite granodiorite and quartz monzonite 48 Red-weathered granite and quartz diorite 14 Diorite gneiss 4 Vesicular basalt 34 100 In the Bouquet Canyon area, light-brown cobble con- glomerate a few feet thick lies at the base of the 487 feet of Modelo formation described by Jahns (1940, p. 155). About three-quarters of the section consists of light-gray, buff, and yellowish-brown fine to coarse sandstone. Silty and sandy greenish-gray shale, buff shale, and thin beds of silty, diatomaceous shale are intercalated with the sandstone, especially near the top of the Modelo section. Just below the overlj-ing Saugus formation are coarse- and fine-grained yellowish-brown sandstone beds carry- ing casts of pecteus, east of Bouquet Canyon ; west of the canyon, coarse gray Saugus sandstone and the reddish- brown mudstone lie on very fine yellowish-brown sand- stone of the Modelo formation. wm» ■««*«iv*. %< IJifefe '•^^^^^mm^:^:^^ A pebble count in light-brown conglomerate beds ex- posed in road cut. Foothill Boulevard, just north of Hansen Dam is as follows : I'HOTO 56. West-dipping Modelo diatdmaceous shale at crest of anticline, east abutment of San Fernando Reservoir dam. Photo rourtesy Los Angeles Department of Wairr and Power. 1!»58] San Fernando Quadrangle — Oakeshott 71 The small areas of Modelo formation in the Sand Canyon-Reynier Canyon region have received the dose attention of geologists because they represent the most easterly outcrops of the formation north of the San Gabriel fault, because the ]\Iodelo clearly lies uncon- formably ou Mint Canyon beds and unconformably be- low Repetto beds, and because good collections of both mollusks (Durham, 1948, p. 1386; Wright, 1943; 1948. p. 1390; and 1951) and foraminifera (Daviess, 1942) have been made. Lithologically, the exposed 400 feet of Modelo formation include a basal cobble conglomerate, coarse gray sandstone, yellowish-brown very fine pebbly sandstone, fine grayish-white sandstone, and thin cal- careous and silt}' diatomaceous shale beds. Strafigraphic Relationships. South of the San Ga- briel fault the Modelo formation is generally overlain unconformably by the marine Repetto formation. This unconformity becomes progressively more marked in an eastward direction across the quadrangle. In the Mission Hills at the southeastern corner of San Fernando Reser- voir, continuous outcrops of thinly stratified very fine sandy shale grade upward into brownish siltstone of the Repetto formation with no apparent unconformity. Four miles to the east, basal Repetto. consisting of reddish- brown conglomerate 250 feet thick, lies on fine sandy shale and interbedded thin limestone of the Modelo formation. The shale surface is an irregular erosion sur- face and the contact is disconformable. In upper Schwartz Canyon, li miles east of Little Tujunga Can- yon, the basal Repetto conglomerate striking X. 70° W. and dipi)ing 40° X. lies on Modelo sandy shale with a local attitude of X. 40° W.. dip vertical." This Repetto- Modelo unconformity follows close to Foothill Boule- vard, just west of Sunland, and is perfectly exposed at the corner of Oswego and Turnbow Streets in west Sun- land where massive yellowish-brown Repetto conglom- erate lies on, and is buttressed against, an extremely irregular surface of Modelo silty and diatomaceous shale, with an angular discordance of at least 20° between the two formations. Base of the Modelo formation, south of the San Ga- briel fault, is exposed in the Paeoima Hills, the Verdugo ilountains, and east of Little Tujunga Canyon just north of the Sunland fault. In the Paeoima Hills basal Modelo sandstone and shale beds lie on Topanga ( ? 1 .sandstone with little apparent angular discordance. In the Verdugo ilonntaius. there also appears to be little angular discordance between the two formations but the heavy basal Modelo conglomerate carrying boulders of Topanga ( ?) vesicular volcanic rocks emphasizes the dis- conformable contact. Southeast of Green Verdugo Reser- voir, the Modelo conglomerate overlaps Topanga (?) volcanic rocks onto granodiorite. Xorth of the Sunland fault, yellowish-brown verj- fine sandstone of the Modelo formation, carrying grains of Topanga (f) volcanic rocks, lies diseonformably on the Topanga ( ?) volcanics. Xorth of the San Gabriel fault, the Modelo formation in Bouquet Canyon is iinconformably overlain by the Saugus formation. Angular discordance amounts to only a few degrees but the Saugus formation overlaps Modelo beds and lies directly on the eroded surface of the Mint Canyon formation, on the south slope of Bouquet Can- yon, 1| miles due east of the Bouquet Canyon highway-. A similar relationship exists between the overlying Repetto formation and the Modelo in Reyuier Canyon, with the basal Repetto conglomerate overlapping the ]\lodelo section onto Mint Canyon beds. The base of the Modelo formation, in BoU(|Uet Canyon and also in the two outliers in the Sand Canyon-Reynier Canyon area, consists of a few feet of cobble conglomerate in uncon- formable relationship to the underlying Mint Canyon lake beds. On the we.st side of Sand Canyon a very prom- inent tuff bed in the Mint Canyon formation, north of the pre-Pliocene fault, is very nearly overlapped by Jlodelo beds at the south end of the half-nnle length of the tuff outcrop. Age and Correlation. The best Qollections of both foraminifera and megafossils have been made from the two outliers of the ilodelo formation in Sand Canvon- Reynier Canyon. Wright (1948, p. 1390) says that ""The upper Miocene age of the basal Modelo ( ?) beds is indi- cated by the presence of dementia ef. martini, Dosinia arnoldi, Lyropecten esfrellanus ss., Spisnla alharia, Ti- vela diahloensis and a large Ostrea." Durham (1948, p. 1386) lists among the more important fossils found in the Modelo (?) of this locality: " Astrodapsis cf. tii- midus, A. aff. fernandoensis. Aeqiiipecten discus, Ana- dara trilineata (Elsmere Canyon variety), Anadara n. sp. aflf. A. obispoana, dementia sp., Lyropecten crassi- cardo,- L. estrellanus ss., Ostrea titan s.l., CanceUaria tritonidca, Trophosycon ocoyana, and TurriteUa cooperi. He indicates that "the ]\Iodelo is approximately equiva- lent in age to parts of the Cierbo and Xeroly of middle California. Three collections by Daviess (1942) (Modelo 9. 10, 11, table 6) were called by him upper Miocene ( ?) or lower Pliocene (?). Daviess, Durham, Wright, and M. X^. Bramlette (in Daviess, 1942) all recognized some affinities of these molluscan faunas with the lower Plio- cene Elsmere member (Repetto formation) faunas. Daviess made two good collections of foraminifera (Modelo 7 and 8. table 6), in the two Modelo outliers, which Bramlette considered of Mohnian age. Mr. C. C. Church examined lists of Daviess' foraminiferal collec- tions (Modelo 7 and 8, table 6) which "appear to be ^lohnian" in his judgment, and Dr. L. G. Hertlein is of the opinion that the lists of megafossils given by Daviess (Modelo 9. 10, 11. table 6) are indicative of upper Mio- cene age (written comment C. C. Church. April 4, 1955). Jahns (1940, p. 167) quotes other collections and deter- minations by J. H. Maxson, U. S. Grant IV, D. D. Hughes, and R. M. Kleinpell, which Jahns believes strengthen a "Xeroly age assignment." Xo really complete collection of mollusks or forami- nifera has been made from the Modelo formation south of the San Gabriel fault. However, several meager collections of mollu.sks identified bv A. J. Tieje (Modelo 1 and 2, table 6) and W. P. Popenoe (Modelo 3, table 6) are considered upper Miocene. A number of meager collections of foraminifera (including ilodelo 4, 5, and fi. table 6) from outcrops and from wells rather well spaced from San Fernando Reservoir to Sunland, and from the top to bottom, stratigraphically. of the forma- tion, have been kindly identified by several oil company micropaleonotologists as characteristic of the Mohnian stage of the upper Miocene epoch. There is little doubt, therefore, that the outcropping Modelo on the northern margin of San Fernando Valley is Mohnian in age. California Division of Mines [Bull. 172 SCALE KlOUKE 19. Fossil localities in San Fernando quadrangle. 1958] San Fernando Quadrangle — Oakeshott 73 Lociilit.v Xo. M<)4) Location : Three localities in same area and litholofty as Locality Xo. Modelo 2. Fossils (determined by AV. 1'. Popenoe) : Dosinia sp. yiiculana sp. Pecten cf. andeisoni Chione ? sp. Ostrea sp. (large, thick-shelled) Age: Probable upper Miocene Locality Xo. Modelo 4 (Collected by G B. Oakeshott) Location : T. 2 X'., R. 15 W., east side of Pacjima Hills at junctii>n Osborne and Glenoaks Avenues. Lithology : Firm light-brown to nearly white, platy, calcareous, siliceous shale : mapped as Modelo formation. Fossils (determined by C M. Carson) : Fish remains Pancaked forams I'rigerina hoot»i Glohigerina huUoidex BuliinineUd rurtn PnlvinulineUn '! riipHiinensis CI) BoHrina sp. Eponides keenani ? Piilvinulinella ? gyroidinaformis ? Bagginn ? cnlijorniin ? Age: Poorly preserved fanua "suggestive of a lower lower Mohnian age." Locality Xo. Modelo ."> ( Collecte.l by C. P>. Oakeshott 1 Location : Sepnlveda Boulevard 0.3 miles north of Rinaldi Street. Lithology : Diatomaceous siltstone and shale of Modelo formation. Fossils (determined by G. B. Oakeshott and checked by H. R. Gale) : l^oraminifera Holivinn ndvenn Cnshman riolirinn pseiidospinxn Kleinpell Holivinn tiunidn Cushman var. cunenla Kleinpell liuliminelhl sp. Caasidulinn cf. pamana Kleinpell Discorhinelln vnlnionteeniiis Kleinpell Eponides niiiltirainerotits Kleinpell T.ngenn sulcata var. (riobigerina bulloides d'Orbigny Orbulina univeraa d'Orbigny Table 6. Fossil localities of the Modelo formation. Piilvinulinella cf. pontoni Cushman I'rigerina segundoensis C\i.shman and Galliher I rigerinella ralifornia Cu.sliman cf. var. parva Kleinpell I'vigerinella obesa Cushni:iu \'alvuliueria sp. Mohnian stage of upper Miocene Age: Locality Xo. Jlodelo 6 (Collected by G. B. Oakeshott) Location: Margin Big Tnjunga Valley due north of McVine Avenue. Sunland Lithology : Diatomaceous siltstone and shale of Modelo formation. Fossils (Determined by G. P.. Oakeshott and checked by H. R. Gale) : Foraminifera Bolivina pseudospissa Kleinpell Eponides multicameratus Kleinpell Globigerina bulloides d'Orbigny Xonion sp. Siphogenerina cf. nucifonnis Kleinpell Z'vigerina hannai Kleinpell Age: Mohnian stage of upper Miocene, probably correlating with Locality Xo. Modelo 5. Locality Xo. Modelo 7 (Collected by S. X. Daviess, Xo. L 2002) Reference : Daviess ( 1942 ) Location: SEJ section 2, T. 3 X.. R. 15 W. ; Gorman Canyon Lithology : Diatomaceous shale, fine white sandstone, and cal- careous shale of Modelo (?) formation, l.">0 feet above Mint Canyon contact. Foraminifera (Determined by M. X. Bramlette) : Buliminella siihfusiformis Cushman Globubulimina pacific Cushman Bolivina aff. hrcvoir Cushman Bolivina aff. decurtata Cushman Bolivina iroodringi Xatland Sugrunda sp. I'vigerina hootsi Rankin I'rigerina sp. ]'alrulerineria si>. Oyroidina soldanii d'Orbigny var. rotundimnrgo Baggina .' sp. Pulvinulinella aff. bradyana Cushman Globigerina bulloides d'Orbigny Orbulina unirersa d'Orbigny Discorbinella valmonteensis Kleinpell Age: "Mohnian stage of upper Miocene" (Bramlette; Church) Locality Xo. Modelo 8 (collected by S. X. Daviess. Xo. L 2051) Reference: Daviess (1942) Location : Xear center north boundary section 2, T. 3 X., R. 15 AV. ; north side Reynier Canyon. Lithology : Within few feet of bottom of Modelo beds lying un- conformably on Mint Canyon formation Foraminifera ( Determined by M. X. Bramlette » : Soniun aff. srhenki Kleinpell Xonionclla aff. miocenia Cushman Biiliniinelitt subfusiformis Cushman Bolivina bramletti Kleinpell Bolivina decurtata Cushman Virgulina californica Cushman ]'irgulinella pertusa (Reuss) Sugrunda californica Kleinpell I'viyerina sp. Ellipsoglandulina sp. Gyroidina muiticameratus (Kleinpell) Baggina californica Cushman Baggina cf. capitanensis Cushman and Kleinpell Cassidulina sp. Cassidulinoides cornuia (Cushman) Chilostomella cf. oroidea Reuss Globigerina bulloides d'Orbigny Age: "Mohnian stage of upper Miocene" (Bramlette; Church) I-ocality Xo. Modelo 9 (Collected by S. X. Daviess, Xo. L 2010 ) Reference: Daviess (1942) Location: SE. i section ,35, T. 4 X., R. 15 W. ; 1,000 feet due west of B. M. 1808. Lithology : Sandstone in basal conglomerate of Modelo formation. Close stratigraphic association with foraminifera of Locality Xo. Modelo 8. 74 California Division of Mines [Bull. 172 I''(issils : Ijjirnpecten entrellnnini (Coinjid) Ijiiritm sp. Neniortirtliuni rf. renfifitosuni ( Carpenttr) Pauopc ffcnf'rosti (loiild BtiiKii sp. Turrilflln frei/a Xomlnnil Calyptrea filosa (Gabh) Trochita sp. PoJi/nices sp. Astrea layiiiondi (Clark) A^e : "Upper Miocene (?) — lower I'lioceiie ('!)' "Upper Miocene" (Hertlein) .Vsie "I'ppcr Miocene (V) — lower I'liocetie "Upper Pliocene" (Hertlein) I '.'I" (l);ivie,w) T. :i X.. R. !.-> W., of Modeio forina- ( Daviess I Localit.v No. Modelo 10 (Collected by S. X. Daviess, Xo. L 2017) Keferences : Daviess (19421, (irant an4) Location: We.st of center of .section 27, T. 4 X., U. 1") \V., on east side X'adeau Canyon near top first ridge south of Santa Clara River. Litholosy : White sands of ui)per miocene ( '!) marine ImmIs of Daviess; mapped as lower Repetto formation liy Oakeshutf Fossils : Lyropecten estrellanus (Conrad) Mytilus ketci Nomland Tliracia cf. trape:odies Conrad l.ui'ina .sp. Chione sp. Tunilella jreyn Xomland I-ocality Xo. Modelo 11 (Collected by S. X. Daviess, Xo. I, 201S) Reference : Daviess ( 1942 ) Location : Xear center east boundary section 2. west side of Gorman Can.von Lithology : Sand.stone and basal conglomerate iton. Fossils : Ostrea IHnn Conrad Lyropecten estrelliinus Conrad Chione cf. teiiihlorensis (Anderson) Terehra cooperi Anderson ('(inevUnriii cf. altaspirn (!abb Catit'eUtiria roiitloni Anderson CitnceUaria (hilliana Anetto formation type localitj', Elsmere Can- yon (Oakeshott, 1950a, p. 55). Winterer and Durham (1954) recently proposed the new name "Towsley" for a formation of late Miocene and earl.v Pliocene age they had previously described without name (Winterer and Durham, 1951, p. 2631). "Towsley formation" (Win- 1 !ir)8 1 San P'icrnando Quadkanoi-e — Oakksiiott 75 tt'i'or and DiirliaiiO includes "' Elsiucrc iiicinhcr" (OaUc- shotn. Tlic tiTiii "Sniishiiic Kaiicli nuMiibcr" of tliu Pico t'or- iiiation was iutroiliiced by the wi-itcr lor the distinctive noninai-inc unit uucont'oi'niably below the lower Pleisto- cene Sauuiis format ion, lyiiifj: above and intertini-'eriuf:' with marine I'pper Pico. He (luoted a deserii)tion of the Sunshine Ranch by John C. Ilazzard (in Oakeshott, l!)50a, p. 5!)-()0). As orifiinally mapped by Kew, these rocks were {grouped with the Saiigus formation. The name Saup:us was introduced by Hershey (1902c) for a series of alluvial deposits he referred to the "Sau- gus division of the upjier Pliocene series" in Soledad Canyon near Saugus. Strata of the upper Miocene Mint Canyon formation in this locality were included in Hershey 's "Sangus. " Kew retained the name Saugus in defining the "Saugus formation, of upper Pliocene and lower Pleistocene age, . . . well developed in the vicinity of the town of Saugus . . ."; ". . . nonmarine in eastern jiart of Santa Clara Valley but grades west- ward into strata deposited under marine conditions." In 1924 (p. 82 and 89), Kew called the greater part of the formation of marine origin and correlated it "tentatively with the late Pliocene deposits at Santa Barbara and with the San Diego formation exposed at Pacific Beach." In 1932, Brown and. Kew noted that "recent work has shown Saugus to be entirelj' of Pleistocene age." In 1937, the writer (Oakeshott, p. 219 and pi. 3) mapped the Saugus as lower Pleistocene, and later ( 1950a, p. 61-63) restricted the name Saugus formation to those lower Pleistocene continental beds unconformably above the upper Pliocene Sunshine Ranch and lying with a great angular unconformity below upper Pleistocene terrace deposits. Repetto Formation The name and type localities of the Repetto formation and Elsmere member of that formation have been dis- cussed in the section above on Pliocene and lower Pleis- tocene geologic units. On the Geologic Map, plate 1, the Elsmere, basal member of the lower Pliocene Repetto formation at the southwestern end of the San Gabriel Mountains, has been separately shown ; the rest of the lower Pliocene rocks have been mapped as Repetto for- mation (undifferentiated). Distrihutiini and Thichncxa. The Repetto formation is distributed in a discontinuous belt along the western and southern margin of the San (Jabriel Mountains for \Zh miles, as far east as Sunland and Tujunga. The most continuous outcrop is on the southern limb of the Little Tujunga sj'ncline, from Pacoima Wash to Big Tujunga Canyon. Maximum thickness of the formation is 3,000 feet, as measured in Lopez Canyon from the top of the underlying Modelo contact to the base of the overlying Saugus formation. The formation thins rapidly eastward to a thickness of 2,400 feet half a mile east of Lopez Canyon, approximately 1,400 feet at Little Tujunga Canyon and 6r)0 feet at Schwartz Canyon. Isolated small fault-bounded remnants of Repetto ( ?) are found in the Rowley fault zone in the town of Tujunga, and in the San Gabriel fault zone near the head of Gold Canyon \\ miles northwest of Big Tujunga Canj'on. At the south end of San Fernando Reservoir, the Repetto formation appears to be about 400 feet thick. v#j ..jmk Photo 57. Detail of uiiper part of lower I'liocene Hepetto formation, on Little Tujnn;;a Road at Merrick Canyon. The Elsmere member of the formation reaches its maximum thickness of 1,400 feet, from its contact on pre-Tertiary crystalline rocks to the overlying base of the Pico formation, in up]ier Elsmere Canyon. The Elsmere thins rapidly northward and is overlapped by the Pico formation before reaching upper Whitney Can- yon. Southeastward the Elsmere member becomes folded and faulted in the complexities of the Santa Susaiia fault zone and is overlapped by the middle to upper Pleistocene Pacoima formation near Olive View. North of the San Gabriel fault, remnants of the Re- petto formation have been preserved i)i the Humphreys syncline between Sand and Placerita Canyons, a second small area on the railroad 1-} miles southeast of Honby, and a spot just north of the San Gabriel fault a mile southeast of Sierra Highway. Thickness, from top of the Modelo to base of the Saugus formation, in Humphreys syncline, is approximately 500 feet. LHhology. Natland and Rothwell (1954, p. 40-41) found the sediments of the Repetto formation in the more central parts of the Los Angeles and Ventura basins to be characterized by foraminifera indicating deposition in sea water 3,000 to 4,000 feet deep. In San Fernaiulo quadrangle, sediments of the Repetto forma- tion were deposited from the shoreline to maximum depths of a few hundred feet at the extreme eastern end of the Ventura basin (Corey, 1954, map, p. 81). Con- sequently great lithologic variation of locally derived clastic sediments, lenticularity, and a greater i)roi)ortioii of conglomerate than in the central part of the basin, are characteristic. At the south end of San Fernando Reservoir the ex- posed Repetto formation (undifferentiated) includes coarse sandstone and conglomerate with lenses and thin beds of very fine sandstone, cobbles of sandy shale (Modelo?), browir and gray thinly stratified fine sandy shale with spots of yellow jarosite (?) and carbon, and thin beds black with petroleum. Checked under a micro- scope, the sandy shale was found to carry arenaceous foraminifera, diatoms, sponge spicules, and small frag- ments of calcareous shells. On the southeast shore of the reservoir, this rock grades downward into silty shale, diatomite, and siltstone of the Modelo formation, in apparent conformity. 7f) California Division of Mines [Bull. 172 ^- . ^ I'liOTO 58. S.'iml.'itono .'iml thin sand.v .shale intcrbeds of lower riiocene Repetto formation, Sepnlveda Koulevard east of San Fernando Reservoir. At Lopez Caii.von the base of the Repetto formation is a massive boulder and eobble eoufjlomerate 250 feet thick, of a prevailing pale yellowish-brown to lijrht-brown color. The contrlomerate carries small sandstone lenses, and thin coarse sandstone beds; and in places, boulders a foot or more in diameter in a matrix of coarse sandstone and pebble conglomerate. The basal conglomerate thickens and thins in short distances along the strike but persists across Ijittle Tujunga Canyon to Tu.iunga Valley; its maximum thickness of approximately 700 feet was meas- ured along a ridge 4,000 feet east of Little Tujunga Can- yon. A count of cobbles from the conglomerate at Tjopez Canyon is as follows : Cranite and granodiorite 80 Diorite 4 Cahliro-norite *! Anorthosite 1 Aplite 1 Uh.volite (?) 3 Dialiase - White (piartzite 3 DarU biotile san2 (Jra.v andium-grained sandstone was found to be 25 percent (|uartz and 75 percent feldspar (chieflj- andesine). Chief minerals in the heavy separate in order of abundance were found to be hornblende, bio- tite, magnetite-ilmenite, garnet, muscovite, and zircon. The sandstone is a locally derived arkose, made up of angular grains, little weathered, and poorly sorted. At Schwartz Canyon, the entire (ioO feet of the Re- petto formation consists of cobble and boulder conglom- erate with minor lenses of coar.se arkose. Near the eastern end of Repetto outcrops at Tujunga Canyon, the formation consi.sts of dark brown, poorly- sorted, irregularly bedded, coarse arkosic sandstone, with strings of pebbles and well-rounded cobbles lying on con- torted Modelo shale. A count of pebbles in a cut on Mt. Gleason Avenue at the meridian 118 18' shows the local origin of the sediments, possibly from both the San Ga- briel and the Verdugo Mountains: Ciranite !) Cneissio granite 8 (Iranodiorite and quartz monzonite 52 Hlue quartz gnei.ss 1 I'orph.vritie rh.volite (?) 4 Tertiar.v andesite or basalt 20 Diorite gnei.ss 4 I>arli (luartzite 3 lUack shale 1 Dark metavolcanic rocks 3 100 The lower i)art of the Rejietto formation is well ex- jxiscd directly west of Sunland. Rase of the formation at the bend in Koothill F>()ulevard on the south side of Tu- junga Valley is a coarse white arkose bed about 20 feet thick, with light-brown conglomerate beds and thiinier arkosic sandstone beds above. A half mile east, at the 1958] San Fernando Quadrangle — Oakesiiott 77 corner of Oswepro and Turnbovv Streets, massive yellow- ^5?^-' ' "^' '^ ■ ■* '' • J^'^'S ' v^ '3^«S'^^kSB ish-brown eobble iind pebble eonprlomerate lies uiicoii- ■, . .i^^^v-tr^; "•&*•* T'--; •«Vi '^^'" ^k2 'i* -3^Kfi forinably on iModelo shale. . ^ .^tJi ,-? ;^^j - ■.\'>^S'^^-^,W ■f'^ ' " The most easterh' exjiosure of llie Heiietto f(ii-ni:it ion ■ ' v"! 'V^'ti* ' •'*^'"^ T' ' '9li^■k^^ ' ' is in the Rowley fault zone at the town of Tujun-a. It >i; '''4j''''-^/'^r^'--'''^'^'i'k^ consists of very poorly sorted pebble to boulder eon^lom- & .^ "v ►"'■ '' '"', ;\."^ :• gLv^^^j^-v . .'."./^.-i.." ' ' ^i': j' erate, and lenses of very coarse arkose, with the boulders S, - - "^^''v^'' ' •*^'^ ■"'■^-r* '•* -^ »■' consisting almost entirely of the adjacent biotite grano- p'> .; j*-"' ' *o^_:^^-' ^"^^*nor.-,t,. mu,! c.arse s.ywlstone ,,f , .... ., , ^, , , . , I. ,1 ^^/^ 1 1 lOIsniprp mpmlier of the Repetto foi-ination l.\ iiif; on I'iileozoic ( .') bdity that these beds represent part of the upper Modelo ,j„^j,j^ ji„^ijp j,„^i^^ i,,^,,, p^,,„^,.,, i„ ,„„.,., ..j^i.t. formation. The Elsmere member of the Repetto formation com- Santa Susana fault and just north of it, basal beds are prises clastic marine sediments of widely varying litho- chocolate-brown sandy shale with interbeds of highly logic types including pebble and cobble conglomerate, fossiliferous and i)etroliferous coarse .sandstone and con- fine to coarse gray and light-brown sandstone, very fine glomerate. A few inches of fine-grained brown sandstone brown sandstone, massive gray and chocolate-brown silt- is actually at the base, lying on the irregular surface of stone and silty shale containing carbon fragments and diorite. gneiss. Oil saturation has aided in preservation gypsum and yellow jarosite ( ?) in fractures, and well- of the mollusks in the .sandstone. Coarse moUusk-bearing stratified white arkose. The lower part of the formation oil-saturated sandstone is found at and near the contact contains a higher percentage of coarse elastics than the north of the Santa Susana fault for about 6 miles to upper, but conglomerate beds several feet thick and the center of section 8, T. 3 N., R. 15 W. Beyond this coarse sandstone lenses are common in the upper part. point the basal sediments become rapidly coarser, are A pebble count from a conglomerate bed several hundred no longer fossiliferous or petroliferous, and one mile feet above the base shows the following composition : north the Lower Pico member of the Pico formation Q.iartz monzonite and granodiorite 41 overlaps the Elsmere and lies on the crystalline rocks. Quartz and white qiiartzite 20 In the northern part of section 8, the basal few feet of Rhyolite ( ?) 9 the Elsmere consists of dark-brown sandstone and Granite aplite _ 5 pebble-to-boulder conglomerate, very poorly sorted, Iving Blue quartz gneiss 5 ',. ., ., .f , i • •" i j ' c i' i Carnetiferous quartzite 1 directly ou the weathered and jointed surface and de- Andesite or basalt 1 posited several feet down into joints and fractures in Metasedimentary rocks (I'lacerita) 18 the granodiorite. The contact is well exposed on the ~" truck trail from Whitney Canyon. This basal few feet of sedimentary rock is probably land-laid; it is overlain A count just north of the Santa Susana fault shows: by marine fine-grained brown sandstone with conglom- Granlte 4 erate interbeds. Cranodiorite and quartz monzonite 60 East of the Santa Susaiia fault proper, the Elsmere Diorite gneis.s 10 member is ill fault contact with the underlj-ing crystal- Quartzite . 4 jjug rocks ill many places. The member is lithologically Metavolcanic rocks 22 • •, ^ ^i . .n t .i f i^ i ^ • • i Similar to that north of the tault, but is progressively 100 les*< petroliferous in an eastward direction and fossils , ,, ^, , •,-,,,-, ,V "1 the basal sandstone are less numerous and less well All these rock types crop out in the San (xabriel Moun- preserved. Grayish-brown very fine gypsiferous sand- tains within 3 or 4 miles of the conglomerates; the .jone, with iiite'rbedded brown conglomerate and coarse metavolcanic pebble.s^may have been reworked from the .sandstone are the principal sedimentary types. Coarse nearby Martinez or pomengiiie formations. calcareous sandstone beds carry most of th^ fossils. A large part of the Elsmere sandstone has been oil- The unditTerentiated Reiietto formation north of the saturated; most of it is dry, but live seeps are numerous y^„ Gabriel fault in the Humphreys syncline, between in the area between Grapevine and Whitney Canyons. ^.^,,^] a^^l Phu^crita Canyons, is largely gray and brown- Saturation by od has been highly irregular, affecting i.sh-grav fine-grained sandstone and siltstone, with nii- both hue and coarse sediments, m many places cutting merous pebble and boulder beds. A brownish-gray bed across bedding planes, and greatly affected, in distribu- of calcareous eoueretionary sandstone, carrying casts of tion, by minor faults, joints, and fractures. mollusks, or brown sandstone and conglomerate marks The basal sediments of the Elsmere member and its the base of the unit in many places, contact with the underlying complex of pre-Tertiary The narrow outcrop of Repetto rocks north of the San crystalline rocks are very well exposed. Adjacent to the Gabriel fault and a mile east of Sierra Highway consists 78 California Division of Mines [Bull. 172 rilOTO (!1. r.llff Ul^lllllM ( iMi-l.iHjrl :ilr iif loWlT I'liocCllc Kl'pi'tto f(irni;itinii l.viiif; uiK'iMiI'diiiKilil.v mi iippt'r Miocene .Mmlelo shale niul tine snnilstone. of very fme-gTaiiu>(l lirowu s;ui(lst()i)(> with beds of brown eoiitrloinerate, carrying fossil moUiisks. The ontiTop on the railroad 1] miles southeast of Honby is composed of gray and ehocolate-browu gypsi- ferous silty shale with spots of yellow jarosite (?), silt- stone, and nindstone, carrying carbonaceous fragments. It is lithologically identical with Repetto siltstone ex- posed at the southeastern shoreline of San Fernando Reservoir. Stratigraphic Hclafioiisliips. The gradational contact between the Repetto and Modelo formations at the south- eastern shoreline of Han Fernando Reservoir, and the increasing angular unconformity between the two for- mations eastward across the northern margin of Tujunga Valley to Snidand were discussed in the section on the Modelo formation, above. The Elsmere member lies with great angular uncon- formity on pre-Tertiary crystalline rocks from near Olive View westward and northward to Whitney Canyon. In njipcr Elsmere Canyon brown, very fine-grained Elsmere sandstone lies unconformably on the irregular eroded surface of hard gray calcareous pebbly middle Eocene Domengine sandstone. Locally the Elsmere beds strike N 70° W., and dip 10^ N. ; the Domengine sandstone strikes N. 20° W., and dips 35° SW. North of the San Gabriel fault, the Repetto formation shows no great angular discordance with the underlying Modelo formation in the Humphreys syncline but does overlap it onto Mint Canyon beds. In the .syncline, the Repetto formation is overlain disconformably (?) by gravels of the Sangus formation. At the Repetto outcrop 1\ nules southeast of Honby, the Ri'petto formation lies with a marked unconformity on the Mint Canyon formation, and is overlain by the upper Pliocene Sunshine Ranch member of the Pico for- mation with an even greater angular discordance. The Sunshine Ranch member dijis at angles of 8° to 10° northward and westward off Reix-lto beds which dip 25° to 50°. Age and Correlaliun. The abundant fauna of the Els- mere member of the Repetto formation has been collected and its age discussed by numerous workers. English (11)14, pp. 209-211) referred to the unit as the "lower Fernando hoi'izon" and regarded it as lower Pliocene; his fossil list is rei)rodnced below (table 7, localitv Re- IH'tto 8). Kew (1!)24, pp. 77-80) repeated Engli.sh'.s fau- nal lists and added others from the Elsmere strata which he used as evidence of the lower Pliocene age of his "Pico" formation. Grant and Gale (1!)31) made many collections and studied the Elsmere fauna and the over- lying middle Pliocene faunas wliich they called "San Diego." Some of the lists below have been compiled from the catalogue of Grant and Gale (table 7, localities Re- petto 9, 10, 11, 12, 13, 14) and others collected by the writer were identified by H. R. Gale (table 7, localities Repetto 6 and 7). Gale (oral communication) regarded the collections as lower Pliocene, with some forms sug- gesting late Miocene. Woodriug, Stewart, and Richards (1940, pp. 111-113, and correlation chart) discussed ;be age and correlation of the Elsmere Canyon fauna and said that "the fauna at this locality is strongly sugges- tive of the Jacalitos formation, and a correlation with the Jacalitos is generally accepted." In later di.scussions Durham (1948, p. 1386), Wright (1948, p. 1390), and others have called attention to the presence of many species in the upper Modelo (?) of the IIum]ihrcys symdine area which are characteristic of the Elsmere fauna. Winterer and Durham (1954) regard their "Tow.sley" formation (majijied as including the Elsmere Canyon beds) as upjier Miocene-lower Pliocene in age. Gale (1948, pp. 1386-1387), in discussing the re- lation of marine cycles to the faunal evidence, makes the summary suggestion that "... the logical position of the Miocene-Pliocene boundary in California is the point of maximum withdrawal between the Delmontian upper Modelo-Ncroly regression and the Jacalitos-Elsmere-Re- petto transgression." This withdrawal was very brief, if any such occurred, in the Humphreys syncline area north of the San Gabriel fault. Less complete and less satisfactory faunal collections in the unditferentiated Repetto formation as mapped near Honby station (table 7, locality Re])etto 20), south of the San Gabriel fault (table 7, localities Repetto 1, 2, 3, 4, 5, 6, 15) and elsewhere in the quadrangle, suggest that at least the lower part of all areas of the Repetto formation mapped in the quadrangle probably correlates with the Elsmere member. Pico Formation The term "Pico formation," iu accordance with pres- ent common usage, is here applied to members of middle and upper Pliocene age. Three members are recognized : marine middle Pliocene Lower Pico, marine upper Plio- cene Upper Pico, and the continental upper Pliocene Sunshine Ranch member. The Lower Pico member (Oakeshott, 1950a, p. 56-57), which reaches a maximum thickness of 700 feet, appears south of the Placerita fault (iu the San Gabriel fault zone) where it dips generally northwest off the pre- Tertiary crystalline rocks.' It also crops out near the south end of San Fernando Reservoir. A sliver of steeply dipping brownish sandstone and conglomerate in the San Gabriel faiilt zone is tentatively correlated with it; no middle Pliocene has been recognized north of that fault. The middle Pliocene beds include white jiebble conglomerate, coarse sandstone with tine sandstone lenses, and thin brown siltstone beds, very much cross- bedded and irregularly impregnated with i)etroleuin. I 1058] Sax Fernando Quadrangle — Oakeshott 79 Tahle 7. Fossil locntitici of the Rrprlto foininlioii. T.orality Xo. Repetto 1 (Collected by M. I,. Hill and C. 15. Oake- sliutt) Reference: Hill (la-JO, p. 143) Location : Xoith center boundary section 5, T. 2 X.. K. 14 W. liitliolosy : Brown and gray sandstone with stringers of pebbles and interbedded conglomerate of Repetto formation. Fossils (Itetermined by A. J. Tieje) : Three gastropods Dosinid sp. Jteiniftisis sp. /.erfo tuphria I'ecten cf. crassicoido Cariliinn iiuadrigennrium Conrad Cliione sp. Dosinia cf. ponderosa (Jray Paphia c(. piiciititoensis Arnold Pecten cf. cerrosensis (Jabb Perten cf. healei/i Arnold Trophostjcon iiodifeniiii (5abb Age : Lower I'liocene Locality Xo. Kepetto 2. (Collected bv B. F. Howell. .Tr.) References: Howell ( l<)4i». lil.>4) Location : XW } section 4. T. 2 X., R. 14 W. Lithology : l"pper part of brown sandstone and conglomenite of Repetto formation. Fossils I Determined by W. P. Popenoe) : Dosinia sp. Ttirritella sp. Pecten cf. henleyi Arnold Age : Pliocene Locality Xo. Repetto 3 (Collected by B. F. Howell. .Ir.) References: Howell (1940, 19.-)4) Location : SE. i .section 31. T. 3 X.. R. 14 \V. ; cliff east side Bar- tholoniaus Canyon. Lithology : Brown sandstone and conglomerate of Repetto forma- tion. KM) feet i-outh of Sangns contact. Fiissils (Determined by W. P. Popenoe) : Pol !/n ices sp. Cliione sp. cf. fernandoensis Lncina acutilineata Peel en sp. Trophosycon ocoi/nna ? var. Age: Probably lower I'liocene "approximately equal to English's Elsmere Canyon fauna." I>ocality Xo. Repetto 4 (Collected by G. B. Oakeshott) Location : Section 21. T. 3 X'., R. 1.") W., about i mile north of Olive View Sanatorium. Lithology : Fossiliferons calcaremis sandstone beds-, interbedded with brown coarse sandstone and conglomerate carrying well- rounded pebbles. Basal beds of Repetto formation, lying uncon- forniably on diorite gneiss. Fossils (Determined by H. R. Gale) : Liicinn (Here) ejcnvata Lucinn (Miltha) j-anihusi Cnjptoniya californiea Mnctra fSpisnIn) sp. ? Veneriipis or Chione ? Kchinoid sp. Age : Lower Pliocene Ix)cality Xo. Repetto 5 (collected by G. B. Oakeshott) Location : Xorth border section 21, T. 3 X'., R. lo W., west side of Schoolhouse (^anyon. Lithology : Basal calcareous sandstone and conglomerate of Re- petto formation, lying on diorite gneiss. Fossils : ( Determined by H. R. Gale) Pecten ( Piitinopecten ) healeyi (var. lohrif) Polynices rcclusinnus Age : Lower Pliocene Locality Xo. Repetto 6 (Collected by G. B. Oakeshott) Location : Section 20, T. 3 X., R. 15 W. ; ridge i mile northwest of Ranchi* Sombrero. Lithology : Coarse basal Repetto sandstone. Fossils (Determined by H. R. Gale) : Pecten ( Patinopecten) healeyi var. lohri Cancellaria ? or yassarius 'i sp. Chione sp. ? Age : Lower Pliocene I>ocality Xo. Repetto 7 (Collected by G. B. Oakeshott) Location : Section 1!), T. 3 X., R.' 1." \V., in upper Grapevine Canyon. Lithology : Chocolate-brown sandy shale with thin beds fossili- ferons petroliferous coarse sandstone and conglomerate, lying unconformably on diorite gneiss. Ba.-sal beds of Elsmere member of Repetto formation. Fossils: (Determined by IL R. Gale) .4ci7n sp. Liicina (Here) excavata Carpenter Lucinn nuttalli Pecten (Patinopecten) healeyi var. lohri ? Pecten stearnsi '! Pectin sp. Chione fernandoensis Turritella cooperi yeptunea humerosa Gabb Cryptoconus sp. Calyiis (Claiheodrillia elsmerensis) Polynices (yeverita ) recliisianus Conns sp. yassnrius sp. Mitrella sp. Astraea sp. Age: Lower Pliocene to upper Miocene (?) I^ocality Xo. Repetto S (W. A. EInglish) Reference: English ( 1!)14, p. 2()!)-211 ) Location : Elsmere Canyon Lithology : Basal .sandstone of Elsmere member of Repetto forma- tion. "Lower Fernando horizon" of English. Fossils (listed by English) : Aslrodapsis fernandoensis Pack Echinarachniii.i excentricns Esch. Amiantis cf. callosa Cpr. .4)cn trilineata Conrad Cardiuni qnadrigenarium Conrad var. fernandoensis Arnold Cardiuin sp. ? Chione elsmerensis n. sp. Ckione fernandoensis, n. sp. Cryptoniya, cf. oralis Conrad Dosinia ponderosa Gray (n. var. ?) Lcda taphria Dall Macoina indentata Cpr. Marcia suhdiaphana Cpr. Metis Alta Conrad Modiolus sp. ? Mytilus sp.? yucula castrensis Hinds Pnnopaea generosa Gould Pecten ashleyi Arnold Pecten cerrosensis G;ibb Pecten heaiyi Arnold Pecten oiceni Arnold Pecten .sp.? small Phucoides acutilineatus Conr;id Phncoides nuttali Conrad Phacoides richthofeni (Jabb Phacoides santnecrucis Arnold Solen sicnrius Gould Tellina idae Dall Venericardia californiea Dall A niphissa sp. ? Astraliuin sp.? Hathytonm carpenteriana Gabb. var. fernandoana, Arnold Jiittium cf. asperuni (Jabb Calyptraea filoso Gabb Cancellaria elsmerensis n. sp. Cancellaria fernandoensis Arnold Cancellaria triionidae Gabb Chrysodomus arnoldi Rivers? Chrysodonius sp.? Conns californicus Hinds Crepidula princeps Conrad Cypraea fernandoensis Arnold Fusus barharensis Tr:isk Gyrineuni elsmerense n. sp. Manyilia sp. ? 80 California Division of Mines [Bull. 172 Mihii iiliii l);ill A'f/.vxf( inilitoffcimitt Aniiiltl \rrrrifii rcrhuianti I'clil J'oh/nifCii sp.V Siithontiliti krUctti Forltt's Tfophon sp.V Truiihosiivoii noriifriiiJii (lal)!) TuniivUii coopvri ("pr. Tunis ehnierciisiH n. sp. Tiirfis fenianiloensis 11. sp. ("I'ttu'eaii Ixme.^i Camel bones, cf. Procnm>lii.i Age : Lower I'lioceiie Locality No. Repetto 9 (Collected by H. R. Gale, Xo. 21(i) Reference: Grant and Gale (lO.'i], p. 103) Location : XWjSWJ .section 17, T. .3 N., R. 15 W. Lithology : Coarse sand.stone bed about 12 feet above diorite gneiss in basal beds of Elsniere member of Repetto formation. Fossils (Determined by II. R. Gale) : I'lirpiirn (Juton) ehhidyri Thais (Niicella) elsiiiereiisis Tigiihi (Chloiosloiiia) galliiia Liiiiiiu (Mijrira) nuttnUii Sityruliti's ( Meijnsurcitin ) mnondii Cancellnrid tritoniflea var. frrndndocusis (Utucellarin triloniiipti var. ftltaspira ('ancellarin ciilratiita ('ancelliiria obrsa \'ar. planospira Age : Lower Pliocene Locality Xo. Repetto 10 (Collected by H. R. Gale, Xo. 207) Reference: Grant and Gale (liWl, p. 102) Location : Xear iiortbern boundary XWJSWi section H, T. H X., R. 15 W. Litbology : Coarse petroliferous sandstone of Elsmere member of Repetto formation. Fossils (Determined liy H. R. Gale) : .■Ilea (Naviciila) terniinunibonis, new sp. A mid litis cailosa C/firj/s (Clathrodrillia ) roaUiigeiisis t^piiotropis ( Antipinnes) cf. huliiiioides Moniliopsis inrisa var. qiiiniiueciiictd Age : Lower Pliocene Locality Xo. Repetto 11 (Collected by H. R. (iale. No. 202) Reference: Grant and Gale (liWl, p. 102) Location: Xear center of northern bonndarv of X'WJSWi, .section 8, T. 3 N., R. ir, W. Lithology : Oil-stained coarse sandstone of Pvlsmere member of Repetto formation, just above diorite-gneiss contact. Fossils: (Determined by H. R. (Sale) Area (Nariculd } teniiiiiiiiiilwiiis, new sp. I'ciiiis fChiotieJ elsiiifi-riisis Age : Lower Pliocene Locality No. Repetto 12 (Collected by H. R. Gale, Xo. 203) Reference: Grant and Gale (1931, p. 102) Location : SEiXWi section 8, T. 3 X., R. 15 W. Litbology : Petroliferous sandstone of Elsmere member of Repetto formation. Fossils (Determined by H. R. Gale) : Forreria iiiagistcr Kelletia (Kelletia) keUciii Ficiis (Trophosycon) uroyana var. coiiiiyiuila Age : Lower I'liocene liocality No. Repetto 13 (Collected by II. R. (Jale, Xo. 204) Reference: (irant and Gale (1931, p. 102) Location: SEiXW} .section 8, T. 3 X., R. 15 W. Lithology: Sandstone of Elsmere member of Rejietto formation. Fossils (Determined by H. R. (Jale) : Clams (Cldlhrodillia ) codiiiigciisis Xassariiis (Triiid) califoriiianits Jidssariiis (Tritia) mendicus Age : Lower I'liocene Locality Xo. Repetto 14 (Collected by II. I{, Gale. X.i. 209) Reference: Grant and (Jale (1931, p. 102) Location : SWJXWl .section 8, T. 3 X., R. 15 W. Lithology : Sandy shale and concretions of Elsmere member of Repetto formation. Fo.ssils (Determined by H. R. Gale) : I'ecteii ( I'atinopectrn) heaUyi var. lohri I'ecteii ( Lyropecten) esiieUanus, typical var. yptiiis (Chioiii-} srrtfris \;ir. fmiaiidoriisis Finis (Ti'iiphosijroii ) ornyitnti \ .-ii". rui/iitoditsii Age: Lower Pliocene Locality Xo. Repetto 15 (Collected by W. E. Ford, U.C.L.A. No. L 2094) References: Ford (1941) Locations: SJXEi section 18, T. 3 X., U. 15 W., elevation 2100 on south side Elsmere C.'inyon. Tjithology : Hitnminous sandstone about middle of exposed section of Elsmere member of Reiietto formation. Fossils : .4)ca fArra) triliiicala Conr;id Vrepidula piiiireps Conrad Dosiiiid pondcrosd ((Jray) Jjiiciiid ( Liicinoiiid ) ariililincaia Conrad Neptinied huiiiiiosiis (Gabb) Pectcri ( l*atiiiopcrtrii) healfyi .\rnold Poiyiiiccs (Xrrrritd ) reel iisia mis (Deshayes) inimunication, 19.54, locality Los Angeles County Museum L ACM IP 291) I.,<)cation: Xear center section 27, T. 4 N., R. 15 W.. approxi- mately ^ mile south of Humphreys; J mile northeast of Locality No. Repel I o 18. Lithology : Highly fossiliferous "gray silt," overlain by 10 feet of coarser rust-colored silt." Mai)ped by Oakeshott (19.54) as basal Repetto formation. Fossils (Determined by Kanakoff) : Kelletia vladiiiiiri sp. nov. Age : Lower Pliocene 1058] Sax Fernando Quadrangle — Oakeshott 81 I,i>c;ilit.v No. Ri'pclti" L'O I .MeKii fossils collected by (!. B. Oakesliott ; fciniiniiiifcni liy Il.-ickel, Otti), written (■(iminviiiic.it imi. 1114!)). I,.ic:iti(in : Scclidii liO. A. IH W.. T, 4 N.. ;ili(.iit i mile southeast of Ilonhj School, in railroad cut. Lithology : fJray and chocolate lirown shale, siltslone, and iiind- stoue ; nliniidant carlionaccoiis particles; jjyi'snm and snifnr in fractures. Mapped liy Oakeshott (10r)4) as Repetto formation. Fossils ( niesafossils determined hv G. I). Ilaniia ; foraminifera hv R. S. Beck ) : I'ectcii sp. I:tiirits hdstaliiit { .V;;assiz i yiiticfi riniisn (H & S) Xassaritiin fosHatiis ((Joiild) liittiuni cf. iiiitiftri/ilatHtii ( (Carpenter) Tcgiila bniiiiu'd iriiillipi) Foraminifera X onion helridf/cnaix Cihicides .sp. Eponides exiijua Age: Megafossils, "lower Pliocene (?)" ; very meager collection of foraminifera suggestive of a stage "high in the iliocene." Live tar seeps are present just west of tlie Whitney fault 4,000 feet due south of "Whitney Can.yon at the base of a boulder conglomerate which lies on Repetto siltstone and fine brown sandstone. Ijower Pico shows no marked angular discordance with the underlying Elsmere member but graduallj- over- laps the latter and lies directly on the crystalline rocks at \Vhitney Catiyon and north. The Lower Pico is over- lain by Upper Pico at Placerita Canyon and by Saugus and Sunshine Ranch beds south of Placerita Canyon, but mapping from the south strongly suggests the I^ower Pico member never extended much farther north but probably thinned to a shoreline not far from the San Gabriel fault zone. Lower Pico in the vicinity of Pla- cerita Canyon and north may well be partly continental i)i origin. A fossil locality (Pico 1, table 9) is not far from the base of the Lower Pico member 2.800 feet south of Whitney Canyon. Grant a)id Gale (1931, p. 33 and dia- gram B) say of that locality: The most easterl.v occurrence of the middle Pliocene faunal zone may he at this locality in the upper horiz(Mi at Elsmere Canyon. Here the section is very thin, probably near the apex of the marine PIi(wene wedge, and tlie njiper and lower littoral zones are .separated by only 200 ot .'i(M) feet of oil-stained shaly sand- stone. . . . The fauna is poorly preserved and fragmentary ; liut it contains several fragments of Pecten estrellnnus variety cerrosensis, and as its stratigraphic iiosition corresponds to that of other occun-ences of the middle Pliocene fossiliferous horizon, it is here assigned tentatively to the upper littoral zone. A small Ficus also occurs at this locality ; but it is not well enough preserved to show whether it is a typical Ficus or a Trophosijcon that had survived a short time after the sea had begun to retreat, living (111 there into the middle Pliocene as other individuals of the .same species did at San Diego. The Lower Pico member at the south end of San Fer- tiando Reservoir consists of massive friable coarse graj'- white sandstone, buff very fine-grained sandstone, and lenses of coarse calcareous sandstone and conglomerate. The calcareous lenses carry a middle Pliocene fauna (Locality Pico 2, table 8). " The term "L'pper Pico member" (Oakeshott, 1950a, p. 57) of the Pico formation is here applied to marine upper Pliocene beds which overlie, with apparent con- formity, the Lower Pico just north of Placerita Canyon. Here the Upper Pico member is unconformably overlain by the Saugus formation. Upper Pico is best exposed in the anticline north of Placerita Canyon. In that region it consists of about 300 feet of well-stratified coar.se brown and buff sandstone, medium-grained sandstone and conglomerate, coarse- to fine-grained dry tar sandstone and yellowish-green sand- stone. Lt the field it was judged to be largely marine, although it may be gradational into nonmarine upper Pliocene beds of the Sunshine Ranch member ; no fossils were found in the outcrops. Two branches of a dome on the anticline north of Placerita Canyon appear, with a reverse fault along the south limb of the south branch. At the northeast end of the south branch of the structure, basal Saugus beds of coarse sulfur-yellow and white sandstone and poorlj- sorted gravel, dipping 20° XXE, lie unconformably on fine to coarse oil sand.stone of the Upper Pico member, which dips 30° NXE. Fragments of cores examined from Xelson-Phillips Kraft 1, the discovery well of Placerita oil field, indicate that that well penetrated continental gravels (Saugus and Sunshine Ranch) to abotit 420 feet and then en- tered the Upper Pico zone consisting of alternating beds of fine gray sand.stone, gra.y fossiliferous siltstone and shale, and eoar.se oil sand. Dr. Leo Hertlein (Oakeshott, 1950a, p. 57) recognized ostraeods and a "species of Criiptomaya resembling upper Pliocene forms in San .Toa(|uin Valley" in the siltstone, and the presence of uppermost Pliocene foraminifera was reported in these beds. The I'pper Pico member between the Placerita and San Gabriel faults includes light brownish poorly sorted fanglomerate, conglomerate, and beds of coarse greenish sandstone. Although mapped as Upper Pico, it is quite likely these beds are continental, in part, and that the region is one of gradation and intercalation of marine Upper Pico and continental brackish-water Sunshine Ranch members of the upper Pliocene. Tahle 8. Fossil Jortilities of the Lower Pico member. Locality Xo. Pico 1 (Collected by H. R. Gale. Xo. 201) Reference: Grant and Gale (31, pp. .'« and 102) Location : Middle of .south boundary of SEiXEi .section 7, T. 8 X.. R. 3 W., elevation 2,02.'> Lithology: Conglomerate in lower part of Lower Pico member of Pico formation. Fossils (Determined by H. R. Gale:) Pecten esirellenus var. cerrosensis Ficus sp. Age: Middle Pliocene Locality Xo. Pico 2 (Collected by G. B. Oakeshott) Location : T. 2 X., R. 1.5 W., .southwest corner San Fernando Reservoir. Lithology : Calcareous sandstone. M.ipped as mi(hlle Pliocene "Lower Pico" (Oakeshott, ]9.")4) member of the Pico formation. Fossils (Determined by H. R. Gale) : • Pecten ( Aequipecten) purpxiratus Lamarck varieties between -■suhilolus Hertlein and caUiilus Hertlein Pecten (Pecten or Chhimys) hastalus var. Area cf. perlahiatn Grant and Gale Lucina (ililtha) j-antusi (Dall) or Lucinii (ilyrtettj acnli- lineata Conrad Fiisinus liarhaiensis (Trask) Polinices sp. Ostrea vespertina Area camuloensis Xeptunea humerosa Gabb Age: "These are all represented in the San Diego zone (middle Pliocene) of the San Fernando Pass tunnel area, except the Area ; the Pecten (Aequipecten) is particularly characteristic of that zone." (H. R. Gale, written comm.) 82 California Division of Mines [Bull. 172 mm m^^mi^-^ Si3^'"' 'V?i ^mi^^i Photo t>2. View west tmvard .'{00-foot spillw.ny of San Fernando Re.servoir. showins north-diiipinK conslomeriite and coarse sand- stone beds of the Snnsliine Ranch memlier of the I'ico formation. Photo courtesy Los .liif/c/rs Uepurtmeut of Wiitcr niid Pourr. Marine iiieiiibers of the Pieo formation have not been recognized north of the San Gabriel fault. The Sunshine Ranch member of the Pico formation was named and defined by Oakeshott from a complete description by Hazzard (in Oakeshott, 1950a, pp. 59-60). Type locality, desio-nated by Ilazzard, was the area north of Suu.shine Ranch between the a.xial region of the (San Fernando) Reservoir anticliiie and Balboa Avenue (one- tenth of a mile west of the western border of San Fer- nando quadrangle). The Sunshine Ranch member crops out in the Mission Hills at San P^rnando Reservoir where a steeply north- tiipiiing section, well exposed along the overflow canal on the west side of the Reservoir, is :?,000 feet thick. It is also expo.sed in the vicinity of the Placerita oil field, north aiul south of the San Gabriel fault. A section just north of that fault, on Sierra Highway, is approximately 1,300 feet thick. It is possible that the lower part of the Saugus formation as mapped in the Little Tujunga syn- cline is Siuishine Ranch but this was not certainly de- termined. Ilazzai'd (Oakeshott, ]95()a, ]). 59) in mapping the Sunshine Ranch eastward from the type locality noted that "The change from shallow marine to fre.sh-water de- posits is believed to occur in the general region between Balboa Avenue and lower San Fernaiulo Reservoir for within those limits the basal coquina reef, as well as nui- rine fossils higliei- in the formation, disappear." In San Fernando quadrangle the Sunshine Ranch member con- sists of nonmarine fluviatile, brackish-water, and lacus- trine gray gravel, brown and greenish sandstone, sandy mudstone, alternating reddi.sh and greeni.sh mudstone, sandstone, and conglomerate, and thin white concretion- ary freshwater limestone beds. Ilazzard describes the Sunshine Ranch of the tyjie locality as follows (reprinted from Oakeshott, 1950a, p. 59)": In the type area Ihe hasal portion of tlie Sunsliine Uanch forma ti(Hi consists of about 20 feel of cross-ltedded pebld.\" Itt coi)l)l.\' sand- stone which at its base locali.v includes boulders of tile nnderl.vinjj I'ico sandstones and shows irr<'fj"lar "cut and fill" contact rela- tions with the older beds. Above the basal sandstone is a co(inina "reef bed" which varies in thickness alonj; the strike but averages about 35 feet. Following is an interbedded series of Kray, coar.se- PirOTO 63. Nonmarine light-gray sandstone and pebbly sand- stone of the lower part of the upper Pliocene Sunshine Ranch member of the Pico formation, southwest abutment San Fernando dam. Photo courtexi/ Los Aitgeles Deptirtment of ^yatel^ mid Power. grained to pebbly, friable sandstone and gra.\' to greenisli-gra.v ver.v tine-grained sandstone, silty sandstone or sandy silt.stone. These fine-grained greenish gray beds are the most characteristic lith- ologic t.\pe of the formation. As a rule, their mere presence, even in thin beds, is indicative of their stratigraphic position. Some of the fine-grained material is in massive beds I to 2 feet thick ; other portions show a poorly devel(}ped shaly parting which is in part controlled by a fine lamination within the rock. The greenish-gray color is due at least in part to an abundance of un- altered biotitic mica. Most of the finer-grained material is angular to subangular in outline. (!ood rounding occurs only in the coarser component of the pebbly gray sandstones. At various horizons throughout the formation the silty sandstones or siltstones are limy .lud at some places soft, white limestone and impure hentonitic ( ''.) lv south of the Santa Clara River. lOoSl San Fernando Quadrangle — Oakeshott 83 Litholot^ic siiuilurity betwcLMi the yaut;us t'orinatioii and Sunshine Ranch member is strong but several dis- tinc-tions, in addition to stratiprraphic position, were used in field niappiuf;. There is a s^'iT'il color difference, the Sunshine Kanch bein. I'ebhic counts in Saiigiis jormalion ; localities * Photo 65. \u\v wisr tnwaid unconformable contact lietweeu ?ray sandstone and conglomerate of lower Pleistocene Saugus formation (right) and brownish fine sandstone of lower Pliocene Repetto formation. Darker pebbles and cobbles in lower S.iugus bed are Repetto. Little Tujunga road. Age and Correlation. The age of the Saugus forma- tion has been discussed bv numerous writers (Kew, 1924b; Waterfall, 1929; Brown and Kew, 1932; Putnam and Bailey, 1942; Bailey, 1943) and was summarized by the present writer (Oakeshott, 1950a, p. 61-62) for its occurrence in San Fernando quadrangle. The work of Putnam and Bailey has well dated the principal orogeny in the Ventura basin as post-lower Pleistocene and pre- upper Pleistocene. Their Pleistocene succession, based on the evidence of marine fossils, is : Upper Plei.stocene — Terrace deposits Upper Pleistocene — Terrace deposits dipping 8°-20° (probabl.v equivalent to Pacoima formation in San Fernando quail- rangle: G.B.O.) Ma.jor unconformit.v Lower Pleistocene — San Pedro = Las Posas= Waterfall's Sau- gus in Hall Can.vou = Kew's Saugus on south side of South Mountain I probabl.v equivalent to Saugus formation in San Fernando quadrangle: G.B.O.) The writer (Oakeshott, ID.lOa, p. 62) has reported the finding of a horse tooth 800 feet stratigraphically above the base of a 3,()00-foot section of the Saugus formation on the east side of San Fernando Reservoir. Dr. Chester Stock identified it as a "more primitive type of Equitx than that fovuul in the later Pleistocene deposits, but still definitely Pleistocene in age." Here the Saugus lies on a 3,000-foot-thick section of upper Pliocene Sunshine Ranch beds which can be traced westward, without a break, into marine fossiliferous upper Pliocene beds. It is therefore believed most probable that the Saugus for- mation in San Fernando (piadrangle is lower Pleistocene in age. but it is not at all out of the question that some of the lower Saugus beds in the Little Tujunga .syncline may be upper Pliocene. Pacoima Formation * The name Pacoima formation is proposed for the fan- glomerate lying on Saugus gravels and below Quaternary terrace deposits in discontinuous remnants around the western margin of the San Gabriel Mountains. Type lo- cality is at the mouth of Pacoima Canyon half a mile below Pacoima Dam near the eastern border of the Syl- mar 6-minute quadrangle. * New name: first published usage by Oakeshott (19.")2). Photo 66. South-dipping coar.se reddish-brown breccia of the mid-Pleistocene Pacoima formation lying nneon- formably on lower Pleistocene Saugus formation, north of Veterans Hospital. 86 California Division of Mines [Bull. 172 .•i:r./' Photo 67. View north toward gently north-dipping brown gravel of the middle ( ?) Pleistocene Pacoima formation lying unconformahly on middle Pliocene marine sandstone of the Lower Pico member of the Pico formation. Borrow pit at southwest corner of reservoir used as a source of material in building San Fernando dam. Photo cuurteny Los Angeles Department of Water and Power. Disirihution and Stratigraphic Position. The Pa- coima formation is exposed in the foothills of the San Gabriel Mountains, south of the Hospital fault, continu- ously westward for 3 miles from Pacoima Canyon to Olive View. Distinctly folded older alluvium in the Mis- sion Hills at San Fernando Reservoir, deposits in an area just south of the San Gabriel fault at the west border of San Fernando quadrangle, and also north of the San Gabriel fault near the junction of Sand and Bear Can- yons, are tentatively correlated with the sediments at the type locality. Stratigraphic and structural position of the formation is best seen in the area between Pacoima Canyon and Olive View Sanatorium. The sediments lie in a trough representing a westward continuation of the tightly folded Little Tujunga syiidine which has a steep north- limb sharply cut off by thrust faults (locally the 45- degree north-dipping Hospital fault) with granitic rocks- thrust over the Saugus and Pacoima formations. Sedi- ments of the Pacoima formation lie with a distinct angu- lar unconformity on Saugus beds, a relationship well exposed on the May Canyon truck trail half a mile north of the Veterans' Hospital. There Saugus gravels dip 60° I'lioTii r,s. !i 1! ^lini.l Quaternary gravel lying on massive lower Pliocene sandstone of the Elsmere member of the Repetto formation on upper Wilson Canyon truck trail north of Olive View. S. with the unsorted imperfectly bedded Pacoima fan- glomerate dipping off to the .south at an angle several degrees lower; a similar relationship may be seen on the east and west sides of Pacoima Canyon. At the head of Pacoima Wash, half a mile east of Veterans Hospital, a ridge extends over half a mile southeast between Pacoima Wash and the wash of Loop Canyon next west. This ridge is capped by a succession of nearly flat-lying Quaternary terrace deposits at five distinct levels; the oldest deposits lie on Pacoima breccia which dips roughly 25° NE. Sau- gus beds in the immediate vicinity, underlying the oldest terrace, dip 45" X. In lower May Canyon, dip of the Pacoima formation ranges from 20° to 50° N. Between Loop Canyon and Wilson Canyon, the basement crj's- talline rocks have been thrust southward over the Pa- coima formation at angles varying from 45° to 60°, cut- ting out the north limb of Little Tujunga syncline. At the western margin of San Fernando quadrangle, the formation is cut off on the north by the San Gabriel fault. Thickness of the Pacoima formation is difficult to meas- ure because of indi.stinct bedding, indistinct attitudes<- aiul poor outcrops; but consideration of topographic re- lief and average dips in the May Canj^on area indicates maximum thickness is probably between 500 and 1,000 feet. Lithology and Suurce. The Pacoima formation is a fanglomerate or sedimentary breccia derived from rapid erosion of the high-standing rugged San Gabriel Moun- tains. It is very poorly sorted, consisting of sharply an- gular pebbles and botdders of a wide size range all deposited together with a dark brown or reddish-brown mudstone-soil matrix. [Many boulders are as large as 2 feet in diameter. All fragments were locally derived from the crystalline rocks, chiefly granodiorite, quartz diorite, diorite gneiss, quartz, and metasediments of the Placerita formation, including cry.stalline limestone. Surprisingly few pebbles which might have been reworked from the underlying Saugus formation eoidd be found ; the Sau- gus gravels were probably soon covered by Pacoima fan- glomerate which overlapped onto the crj'stalline rocks. Bedding is crude to lacking, but examination of large cuts, natural and man-made, disclo.ses unmistakable atti- tudes. Color of the formation is predominantly dark brown but the detritus near the base, due west of Vet- erans' Hospital and at Olive View Sanatorium, is deep red. In the field the Pacoima formation was distinguished from the overlying Quaternary terrace deposits by bet- ter stratification, deeper weathering, more extensive modification by erosion, and by the effects of mild to strong folding and faulting. The Pacoima formation was distinguished from the older Saugus formation bj- poorer bedding, extreme angularity of fragments, almost com- plete lack of sorting, very local source of fragments, and the effects of less folding. Age and Correlation. Stratigraphic position and re- lation to the mid-Pleistocene orogeny that affected the eastern Ventura basin are the principal evidences of the age of the Pacoima formation. It lies unconformablj^ on the lower Pleistocene Saugus formation and unconform- ahly below near-flat late Quarternary terrace deposits and older alluvium. Although the Pacoima beds are locally in.'iSl Sak Fernando QuADRANr.LK — Oakeshott 87 I'HOTO (i!t. Quaternary stream terraces northwest of Solamint as seen from I". S. Highway 0. I'nderlyiiij; nonniarine Mint Canyon I. Miocene) l)e(ls have been snlijected to several epochs of planation by the Santa Clara River dnrinj; Quaternary time. I'art of the Sierra I'elona rises in the liaclvj^ronnd. Photo hy C ^V. Jcuiii»(js. strongly folded and have been cut by late fault move- ments, they were not involved in the orogeny to as great an extent as the Saugus and older formations. It is most likely, therefore, that the Paeoima formation was dej)osited in middle to early upper Pleistocene time. Correlation with other remnants of tilted and folded older alluvium, well awaj' from the type locality, cannot be precise. Terrace Deposits Remnants of older alluvial deposits, uplifted and eroded to form terraces, are widely distributed in San Fernando quadrangle. Such remnants represent stream- channel and flood-j)lain deposits, alluvial fans, and talus accunudations. Thicknesses vary from a few feet to as much as 200 feet. A few small thin patches of fanglom- erate are found at elevations as high as 3.000 feet in the areas of exposed crystalline rocks, but the most ex- tensive terraces are at the low western margin of the mountains in the drainage area of the Santa Clara River and along the margin of the San Fernando Valley. With few exceptions the terraces pai-allel present drainage courses and quite apparently are deposits left by modern streams in earlier cycles of erosion when their courses differed slightly from those of the present .streams. Lithologically, the materials in all terraces are broadly similar, consisting of brownish and grayish dirty un- sorted angular to subangtilar detritus entirely of local origin. Consolidation is ])oor and the deposits are only locally cemented. Many fragments as large as several feet in diameter are present. Deposition of alluvial ma- terials now taking place in the western San Gabriel Mountains and margins indicates closely similar topog- raphy and drainage when the terrace deposits were being laid down. However, the belts of terrace deposits are broader than present stream deposits, in some places, and were probably formed by streams at slightly lower grades in broader valleys than the present. Where de- posits of two distinctly different ages were observed, the older appear more deeply weathered and are brown to reddish-brown in color. The terrace gravels and breccias are not absolutely flat but dip at low angles, essentially in the same direction and with nearly the same dip as Recent stream gravels. Dip of the terrace deposits increases as the crest of the range is approached; dips are gentlest on the margins of the present br(ja(lest valleys. For example, terrace gravels near the junction of Mint Canyon and the Santa Clara River are nearly horizontal, those in Kagel and Lopez Canyons dip about 3° S.. and the prominent de- posit between Buck and Little Tujuuga Canyons dips about 10° S. It is probable that initial dips of the terrace dejKisits were slightly increased by the latest tectonic elevations of the western San Gabriel ilountaius. In most places, where it was possible to observe relation- ships closely, the terrace deposits are later than the faults and lie acro.ss them without displacement. Excep- tions are a faulted terrace deposit on the west side of Oliver Cauj'on on the northern margin of Tujuuga Valley, and the broad area of terrace and Recent allu- vium which has been slightlj' displaced by verj' late movenu'ut on a branch of the Elkhorn fault. In many i)laces terrace gravels only a few feet in thickness lie on nearly flat or very gently sloping nearly I)lane surfaces of erosion. In some places topographic terraces, readily recognized on the 1 :24,000 topographic maps and on aerial photographs, are devoid of deposits. Most ]n-ominent of these erosional terraces is Puckett Mesa, a mile long and a quarter to half a mile wide, just beginning to be dissected by headward erosion from Plum Canyon and tributaries of Mint and Boutiuet Can- yons; others api)ear in Bou(|uet Canyon and just north of Santa Clara River. An area of 10 or 12 square miles bounded by Bouquet Canyon, Mint Canyon, Santa Clara River, and lower Vasqnez Canyon, f)robabiy covered by stream and alluvial-fan deposits in late Plei.stocene time, has subse(|uently been elevated and slightl.v tilted toward the southwest, resulting in di.s.seetion of the old alluvium and its more or less incomplete removal. Terrace deposits of several slightly different ages are recognizable in San Fernando quadrangle. Five distinct 88 California Division of Mines [Bull. 172 ^■:^ 'V^. •■.V\»' « ^■^•«*^ ■■■■'■. ■'J •■*.# y ^ J ■ .i-€.. Photo 70. Quaternar.v .strfam-chiuiiiel .sand and ^-ravcl deposits .Tsainst white Cretaeeoius (?) granodiorite in the San Gabriel Mountains. Little Tujunsa road in I'aooima Can.von. Photo by C. W. Jennings. steps, easilj- seen on the west side of Pacoima Wa.sh and well marked on the 1 :24,000 Sj'lmar topographic map. actually represent five stages of deposition, although the oldest and youngest are separated only 250 feet in ele- vation. Elsewhere two distinct levels of terrace or bench gravels are connuon as. for example, in the Lopez-Kagel Canyon district, Placcrita Canyon, and Soledad Canyon. In the first area Hill (1930, p. 144) distinguished the older and higher "Lopez formation" from the "Kagel formation." The older is predominantly brownish in contrast to the grayish color of the Kagel fanglomerate. Because of variations in local conditions of deposition, contemporaneous deposition at quite ditferent elevations, and the scattered fragmentary deposits of older allu- vium, no criteria were found to correlate any but adja- cent terraces and no correlations could be made with late Quaternary events elsewhere in southern California. The terrace deposits lie with marked angular uncon- formity on the middle ( "?) Pleistocene Pacoima forma- tion, best seen west of Pacoima Wash in back of the Veterans Hospital, aiul with great angular unconformity on the lower Pleistocene Saugus formation. All older alluvium at higher levels than adjacent Recent alluvium, or disconformahly below it. was mapped as terrace de- posits. Jlost likely age of the terrace deposits is upper Pleistocene. Landslides In spite of high relief and rugged topography there are few landslides of consequence in San Fernando (|uadrangle. Three on the south slopes of the mountains were developed by local sliding of granitic debris from the oversteepened granitic slopes across fault contacts to come to rest on the more gently sloping eroded sur- faces of the Saugus formation. These small slides obscure the northwest termination of the Sunland fault zone, east of Little Tujunga Canyon, and cross the Lopez fault in upper ilarek Canyon. The sharp bends and abnormally low dips of the Buck Canyon fault may be due to mass slumping of the granodiorite which has been thrust over the Saugus formation in upper Buck Canyon. The relativel.v large landslide area shown on tlie Geo- logic Map, plate 1, just north of the San Gabriel fault and east of the Sierra Highway is not a single slide but is an area of no outcrops and of slumping and numerous minor slides in fine-grained lake beds of the Jlint Can- yon formation ; Saugus conglomerate in the fault zone forms a steep ridge immediately to the south. Recent Alluvium The largest area of alluvium in San Fernando fjuad- rangle is in the San Fernaiulo and Tujunga Valleys which extend almost entirely across the quadrangle. Re- cent deposits in this area consist of predominantly coarse, very rapidly deposited thick accumulations of boulders, gravels, and sands in coalescing alluvial fans along the steep front of the San Gabriel Mountains. The principal streams, including Big Tujtiuga River, Little Tujunga Creek, and Pacoima Creek, run over steep gradients in the mountains and carry large volumes of water to the Los Angeles River at times of heavy rainfall in winter and spring. They deposit their loads when gradients abruptly decrea.se and water is spread on reaching the vallev. All arc normally dry in summer and early fall 1058] San Fernaxdo Quadrangle — Oakesiiott 89 hiif records of maxiniuin (lisc]iari;p are as liigli as 50, 000 <'nbi(' feet per spcoiul ( liijr Tujiinfra River on l\Iarch 2. 11188: r. S. Geol. Survey 19r)4. p. 114-1]!!, 1:34). The constrnctioii of dams, siieli as Paeoima, Hansen, and Bip Tujunfra, is chanfrinir stream regimen and the natural distribution of {Travels, On the north side of the ranetween Cretaceous (?l grano\ver Pliocene Klsniere nieniher of the Repetto formation. The Somlirero fault separates the latter from white heds of the lower Pleistocene Sau^ns formation in roadcut. The higher hills had; of the Ulippe consists of the I'aleozoic (?) complex thrust over Klsmere on the (Jrapevine fault. The Sierra Madre faidt zone is a series of arcuate, convex-southward reverse faults which separates the pre- Tertiary crystalline rocks on the north from the Ceno- zoic sedimentary formations on the south. The faults are discontinuous and with most dips ranging from 15° to \-crtical ; all dip northward with the crystalline rocks tlirust upward toward the south over sediments as late as the mid-Pleistocene Pacoima formation. Displacement has been essentially of the dip-slip type, and is as great as 2,000 feet on one of the faults. Displacement rapidly dies out as the strike of each of the.se reverse faults changes from the general east-west trend to a more northerly trend. The Grapevine and Sombrero faults, and subsidiary lesser faults, represent continuing faidts from the north- east end of the Santa Susana thrust fault zone. The Grapevine fault is exposed on a very steep, high, topo- grai)hic slope w-here the Placerita formation-diorite gneiss complex has been thrust, at angles of 40'^ to 50°, over folded and disturbed beds of the Elsmere member Plioio T;?. View east alons south front of San (Jabriel Moun- tains fnun Olive View. Sharp hreak in slope is Hospital-Lopez fault zones ah)ns whii'h jire-fretaceous crystalline rocks are thrust over l*Ieistocene nonniarine sediments. Photo hy T. E. (iiii/, Jr. 1958] San FiiKNANDO Quabrangle — Oakeshott 93 of the Kepotto formation. Type loenlity of tlie (irapeviiie is at the liead of the east braiieh of (tfapeviiie (jaiiyoii. The iiortli-ti'eiuliiii;' Soiiihrero fault shows the same rebi- tioiiships hut has a lu'ar-vertieal (li|) at its type hx-ality in Sombrero Canyon. Hill 1876 is an interestinfr klippe of the erystalline-roek eomplex lyin8i San Fernando Quadrangle — Oakesiiott 97 «w^' Photo so. I^ookiuR soiitliwcst rmiu Scilcil^id C'jin.von at Pole Canyon fault. Linht-coldifd anortlio.'^itf on right against dark gabbroic rocks. I'hoto hy T. E. (lay, -Ir. rocks, Vasqiiez volcanic rocks, and syenite-hornblende diorite. None affect Quaternary deposits. The fault planes can rarely be pin-pointed because of rather poor exjiosures. The Little Escondido fault has apparently displaced Vasquez rocks left laterally about half a mile. The Pole Canj'on fault is one of the major northeast- trending faults of the western San Gabriel Mountains. It was mapped as an unnamed fault separating crystal- line rocks from basin sediments by Kew (1924b) and by Miller (1928a). The writer (Oakeshott, 1936, 1937) remapped, named and described the fault and designated the type localitj- on the east side of Pole Can.yon. At that point the Pole Canyon fault is a well-defined single plane exposed for several hundred feet in dark gabbroic rocks; strike of the fault is N. 55° E. and dip 70° SE. About 2,200 feet northeast of Pole Canyon, dip is 72° SE. and the fault forms the contact between white anor- thosite on the northwest and dark gabbro on the south- east ; it is this contact which makes such a striking view from the Soledad Canyon highway. Good exposures of the fault continue another mile to the northeast, main- taining .southward dips of 65° to 68° ; thence the fault zone has apparently been followed by Soledad Canyon for 2| miles. Northeast of the canyon the Pole Canyon fault has offset the Soledad fault 1.4 miles in a left lateral direction and forms the contact between anor- thosite on the southeast and the Vastiuez formation on the northwest. Southwest of its type locality the Pole Canyon fault can be traced for .slightly over a mile where it dies out or is buried by Mint Canyon sediments. A quarter of a m.ile south of Pole Canyon a well-exposed branch of the Pole Canyon fault dips 50° SE. and an associated north- striking west-dipping fault marks the contact between gabbro and Mint Canyon beds. The relationships be- tween this latter fault, the Soledad fault, and the Agua Dulee fault are obscured by alluvium deposited by the Santa Clara River. For over 3,300 feet north and 4,000 feet south of Oak Spring Canyon, the Mint Canyon formation lies unconformably on dark coarse-grained gabbroic rocks; the two units are not in fault contact. The west-dipping basal Mint Canyon beds are dark grit and pel)bl.\' sandstone made up wholly of tlie undcrl.ving gabbro. Tlic tuiconformity is best exposed at a point 3,300 feet north of Oak Si)ring Canyon. South of Rabbit Canyon the Mint Canyon-gabbro con- tact is again faulted; the best exposure, a quarter of a mile north of Iron Canyon, shows the fault striking N. 10° E. and dipping vertically; it is marked by 8 inches of gouge. This is evidently a normal faidt. It has dis- placed beds of the iipper Miocene Mint Canyon forma- tion but not the overlying mid-Pleistocene Pacoima for- mation gravels. The Magic Mountain fault was originally called the "Iron Mountain'' fault (Oakeshott, 1937) and the type locality was selected 6,200 feet N. 71° W. of "Iron iMountain" in a narrow canyon at elevation 3,600 feet. Higgs (1954a) called it the "Bear Canyon fault." The name of the fault was changed to Magic Mountain (Oakesiiott, 1954b) after the U. S. Geological Survey changed the name of the mountain on the new topo- graphic maps. At the type localit.v about a foot of brec- ciated rock and gouge separates white anorthosite on the north from dark gabbroic rocks on the south. Strike is N. 60° B. and dip 75° N. Like the other faults that cut anorthosite, the Magic Mouiitain fault shows up in a striking way on aerial photographs where white anortho- site has been brought into contact with the darker rocks. The Magic Mountain fault is confined to the anorthosite- gabbro-granite complex but has produced an apparent left lateral offset of the anorthosite-gabbro contact of about IV2 miles on the northwest slope of Magic Moun- tain. The Transmission Line fault (Oakeshott, 1954b) is another major northeast-trending left-lateral shear con- fined to the crystalline rocks. This is, in part, the "Pa- coima fault" of Miller (1928a) but this name was dis- carded because of possible confusion with a fault in Pacoima Wash suggested by Miller (1928a), and later discounted by Hill (1930, p. 153, A Pacoima fault?). Type locality of the Transmission Line fault is taken on the transmission line road in the North Fork of Pacoima Canyon near the mouth of Lonetree Canvon. There the strike is N. 40° B. and the dip 80° S. Straightness of the fault across terrain of high relief shows that the fault dip is nearly vertical. Where the fault forms the contact between white anorthosite and dark gabbroic rocks, as it does at the type locality, it appears with startling clarity on aerial photographs; elsewhere it is more difficult to follow. Outcrops in the area are gen- erally good but alteration and weathering of the crystal- line rocks and a thick brush cover make actual exposures of the fault plane rare. The fault continues to the north- east at least 6 miles into Tujunga (piadrangle (Fig. 10, Geologic map of anorthosite-gabbro) and splits into three planes crossing Arrastre Canyon. Followed to the southwest from the type locality, the Transmission Line fault appears to split into two or more branches, one of which may continue as the west-trending fault (who.se exact trace is undetermined) which forms 3 miles of the contact between gabbroic rocks and the Mendenhall gneiss. This west-trending branch fault does not continue west of Whitewater Canyon. Ap])arent left-lateral move- ment on the Transmission Line fault has been at least 98 California Division of Mines [Bull. 172 1 - .■■■' 1' :■>:» ^. 14 = "^^ W ^ /'^ ^-' % \ i '^'" ^ /' t be a o o Si o. 19581 Ran Fernando QrADKANOi-?: — Oakeshott 99 100 California Division of Mines [Bull. 172 1.7 miles, as sugrg;ested by displacement of the anortho- site-gabbro contact at the junction of San Fernando and Tujunga quadranfrles and the anorthosite-granite con- tact in the Arrastre Canyon area. The Lonetree fault (Oakeshott, 19o4b) is a west -trend- ing branch of the Transmission Line fault with the same apparent characteristics. Type locality is taken where the fault crosses Lonetree Canyon ; at that point dip is vertical and the fault forms the contact between dark gabbroie rocks on the south and white anorthosite on the north. Near the junction of the Lonetree and Trans- mission Line faults, banding in gabbroie anorthosite is roughly parallel to the two faults. Iliggs (1954a) pro- jected the Lonetree fault about 3 miles farther west into Sand Canyon and called it the ' ' Sand Canyon fault ' ' but the writer could not follow it with certainty west of Dorothy Canyon. No direct evidence of the nature of movement on the Lonetree fault could be found, al- though it probably has been similar to that of the parent Transmission Line fault. A north-trending fault, near the junction of Gorman and Sand Canj-ons, brings west-dipping Mint Canyon beds into contact with the Modelo formation. The fault appears to be normal and the upthrown side is on the east. A continuation of this fault northward for 3 miles along Sand Canyon is postulated to account for the failure of beds and structures to match across the quarter-mile band of alluvium in the canyon. Particu- larly, a well-exposed tuff bed on the west side could not be matched on the east side of the canyon. In summary, the elements of the fault pattern des- cribed in the western San Gabriel Mountains include : (1) the dominating northwest-trending, right-lateral San Gabriel fault cutting obliquely across crystalline and sedimentary rock formations of all ages; (2) a north- east-trending group of en echelon left-lateral faults in the block north of the San Gabriel fault; and (3) the Sierra Madre zone of discontinuous east-trending re- verse faults in the block south of the San Gabriel fault. This fault pattern, and the associated folding described below, are consistent with development of a stress-strain system involving crustal shortening in a north-south direction, combined with action of a force couple along the San Gabriel fault. Folding In San Fernando quadrangle, unconformities between the successive Tertiary and Quaternary formations show that orogenic movements took place locally at various times during the Cenozoic era, but the mid- Pleistocene orogenic epoch overshadowed all of the others in intensity. During the faulting, and the ac- companying folding, the massif of pre-Tertiary crystal- line rocks behaved essentially as a competent block undergoing intermittent elevation, with adjustments within that block accomplished by faulting, shearing, and fracturing. Around the margins of the crystalline block the sedimentary strata reacted, according to their competence and the local intensity of stresses applied, by develoiiing a series of discontinuous folds closely related to the faults. Many local synclines developed on the downdropped fault blocks and anticlines ou the upthrown blocks. The dominant fold-structure of the northern sedi- mentary area is the Soledad basin syncline, a northeast- trending trough lying between the San Gabriel massif on the south and the Sierra Pelona ridge of Pelona schist just north of the quadrangle boundary. Topo- graphic and structural plunge of the Soledad basin are to the southwest. Axes of complicating minor folds in the area trend generally northeast, broadly parallel to the northeast-trending fault system, and flanks of the folds steepen only adjacent to the faults. Stratified rocks, as late as the mid-Pleistocene Pacoima formation, within the San Gabriel and Sierra Madre fault zones have generally been compressed into tight, very steeply dipping complex folds. The dominant fold-structure of the southern sedi- mentary area, or San Fernando basin, is the asym- metrical Little Tujunga syncline which trends (west to east) N. 60° E. through "due east to S. 60° E. across the quadrangle, closely following the Sierra Madre fault zone. The axis of the San Fernando basin lies between the San Gabriel massif on the north and the high repre- sented by the Mission Ilills-Pacoima Ilills-Verdugo Mountains, on the south. Soledad Basin Folds The Soledad basin syncline trends approximately N. 60° E. and involves the terrestrial sedimentary and volcanic rocks of the late Eocene ( ?)-01igocene Vasquez formation, the lower to middle Miocene Tick Canyon formation, and the upper Miocene Mint Canyon forma- tion. At its northeastern end, a well-defined axis crosses upper Agua Dulce Canyon half a mile north of the Escondido Canyon junction. Here the syncline plunges 25° SW. ; plunge is 40° at Vasquez Rock. To the north- east, great exposed sandstone and conglomerate beds of the Vasquez formation, up to 150 feet high, form a quarter-circle of outcrops dipping south to west. The Vasquez formation lies unconformably on Cretaceous ( ? ) syenite a mile northeast of Vasquez Rock. This particular synclinal axis can be followed only a mile or two, southwest of Agua Dulce Canyon. It is prob- able that extensions of the converging Elkhorn-Tick Canyon fault systems cut off the structure in the Spring Canyon-Tick Canyon region. Limbs of the syncline are sheared on the north, east, and south by the fault sys- tems discussed in the previous section. The northeast trend of folding of the Soledad basin syncline is represented farther west in a series of two en echelon synclines and an anticline through the Mint Canyon-Plum Canyon area. These are rather gentle folds whose flanks dip 10° to 30° and which plunge from 5° to 30° SW. Horizontal beds of the Saugus formation occupy the lowest part of the trough area of tlie .syn- cline that parallels Plum Canyon. A group of very tight, steep-flanked east-trending syn- clines and anticlines characterizes the complexly-folded area of the Tick Canyon and Vasquez formations be- tween upper Agua Dulce and Mint Canyons. Major unconformities between the Vasquez and Tick Canyon formations and between Tick Canyon aud Mint Canyon formations show that rocks in this area were strongly folded (also faulted) and eroded in the Vasquez-Tick Can.yon interval, and that folding was renewed in the interval between Tick Canyon and Mint Canyon deposi- 1958] San Fernando Quadrangle — Oakeshott 101 tion. The easterly trend of foldiiifr continues westward across Vasquez and Bouquet Canyons, although folds in tlie ^lint Canyon formation are more open tlian those in tlie Vasquez and Tick Canyon formations of tlie Mint Canyoii-A>rua Dulee Canyon area. Many local east- trendinij and west-northwest-trendinp; minor folds cross Bouquet Canyon and lower Vasquez Canyon; they can be followed closely because of the tuff marker beds in the Mint Canyon formation. .Several faults of small dis- placement have cut these folds. Folds of the San Gabriel Fault Zone and Placerita Area The area of the Placerita oil field and the zone north of the San Gabriel fault within 1 J miles have been dis- cussed and 1 :24,00()-scale geolo<^ic and tectonic maps have been published (Oakeshott, 1950a, 1954a). This is a region of complex faulting and associated tight folding, all closel.v related to movements within the San Gabriel fault zone (see section in this bulletin on the San Gabriel faidt zone). Between the west bo\indary of San Fernando quad- rangle and Sand Canyon the San Gabriel fault zone is at least 1^ miles wide and comprises four major faults and a large number of complex tight folds involving formations as late as the mid-Pleistocene Pacoima. Steep- sided narrow synclines and anticlines between the faults closely parallel the San Gabriel fault zone ; dips in the Saugus formation are as steep as 80°. A short distance away from the fault planes, folds become a little more open and their axes all swing toward the south as they are followed eastward (Highway anticline south, High- way anticline north, and Humphreys syncline, as shown in fig. 20. These are drag effects resulting from right- lateral strike-slip movement along the San Gabriel fault. Highway anticline north shows very steep dips in the Mint Canyon formation on both limbs, and a 25° W. plunge, bringing down Repetto siltstone, Sunshine Ranch, Saugus strata, in turn, around the west end. The anticlinal axis curves southeast into a pre-Pliocene fault. Angular unconformities between the formations named and decreasing di])s with decreasing age show that this fold developed at the close of the upper Miocene (Mint Canyon), was renewed after lower Pliocene deposition (Repetto), again after upper Pliocene deposition (Sun- shine Ranch) and again in the late Quaternary (post- Saugus). Highway anticline south is an asymmetrical structure of similar history to Highway anticline north, involving Mnit Canyon. Sunshine l?ancli. and Saugus beds. On its .south limb, Saugus and Sunshine Ranch beds are turned steeply down against the San Gabriel fault, but on the north limb gentl.y dipping Sunshine Ranch strata lie on steeply dipping locall.v contorted beds of the Mint Can- yon formation. This structure appears open to the west, and dies out across Sierra Highway to the southeast. An en echelon anticline appears 0.4 mile northea.st of Highway anticline south and can be followed about 3 miles southeast of the highway across a slumped area ("Qls" on, pi. 1) of fine-grained j\Iint Canyon lake beds. This structure plunges about 10° NW. and at its south- east end passes into a zone of faulting. At least five wells (pi. 2, nos. 94, 95, 97, 98, 99) have been drilled for oil on the axis of this anticline; all bottomed as dry lioles in the Mint Canvon formation. I'liOTo SI. North end nf Huniphre.v.s syncline at Reynier Canyon. Ipper Miocene Mint Canyon formation in the foreKrcnind, overlain liy thin npper Miocene Modelo sandstone in lirush-covered middle ground ; lower Pliocene Repetto conglomerate and sandstone exposed in the cliff face. One of the most interesting small folds in this area is the Humphreys syncline whose axis trends north- northwest from Reynier Canyon to Hinni)hreys. about 2| miles. The fold involves nonmarine Mint Canyon strata, marine Modelo and Repetto formations, and non- marine Saugus beds. Dips in the Mint Canyon beds are on the order of about 40° and show a trougli fold, closed on the southeast, that flares broadly north-northwest to the Santa Clara River where the structure can no longer be followed ; this was the type of structure formed in closing Mint Canyon time. Remnants of the Modelo for- mation, average dip 30°, lie nnconformably on the Mint Canyon formation in the Reynier Canyon area. The Modelo formation was affected bv minor faulting and erosion and then overlain b.v the marine Repetto forma- tion. Repetto beds dip an average of 15°-20° and form a closed structure whose north-northwest extent is about three times its east-northeast width. Trougli of the syn- cline is occupied by the more gently, more symmetricallx' folded beds of the Saugus formation. In the Placerita oil field area, structural contours (Barton and Sampson, 1949; Oakeshott, 1954a) show that Pliocene beds dip essentially homoclinally 15° to 20° WNW. South of Placerita Canyon, the Elsmere, Tjower Pico, and Sunshine Ranch members and the Saugus formation dip homoclinall.v northwest off the crvstalline rocks. Many minor faults and anomalous local dips, on too small a scale to show on the map, show that tectonic ad.iustments have taken place. Folds of the San Fernando Basin and Margins The principal structural feature of the San Fernando basin is the asymmetrical Little Tujunga syncline whose axis lies close to the northern margin of the Cenozoic sedimentary rocks. The axis of this fold closely parallels the trace of the Sierra Madre fault zone, following it with a west-northwest trend in the area from Tujunga to the Veterans Hospital at Loop Canyon where it may have been overridden by the crystalline rocks along the Hospital fault. Continuing westward, the axis changes to a southwest trend, paralleling the northeastern end of the Santa Susana fault zone. Formations along the 102 California Division of Mines [Bull. 172 ;,»'!'^iI«P:i, r ; ■.*■ . <^---, >■ «.iM^ I'liojo 82. Crest of anticline in npper Miocene Jlodelo diii- tdniacemis shale, west side Sepiilveda Boulevard. San Fernando Reservoir. Photo vourlesij Los Angeles Drpnrlment of Water iiiiil Poller. south limb dip 25° to 80° N. ; the north limb is very steep to overturned and has minor folds superimposed on it. Saugus beds are overturned in several places along the Lopez fault, particularly in upper Lopez Canyon. Overturning of the Saugus formation is general along the Suidand fault where the north limb of the syncline has been almost completely cut out by the fault (pi. 3, geologic sections BB' and CC')- North of the Lopez and Sunland faults, pre-Tertiary crystalline rocks are exposed, flanked by Saugus strata, in the central part of an anticlinal structure called the Little Tujunga anticline. Elevation of the crystalline block along the Sierra Madre fault zone formed this west-plunging structure. It is complicated on the south limb and down the plunge by faulting and numerous minor subordinate folds. On the anticlinal axis rem- nants of flat-lying Saugus gravels are present east and west of Little Tujunga Canyon. On the north limb the Saugus formation dips ofl' granodiorite at about 25° in the Gold Creek region, the dip steepening northward until the formation is cut out by Buck Canyon-Watt fatilt. West of Little Tujunga Canyon the northwest flank of the structure has been complicated by a series of small folds and three important faults. Strikes and dips of the reverse faults on the north, west, and south approximate attitudes of the subjacent Saugus strata. The south limb of Little Tujunga syncline exposes north-dipping beds of the Modelo formation and the unconformably overlying Repetto formation in a strip north of Tujunga Valley between Pacoima Wash and Big Tujunga Canyon. A small outlier of Repetto beds ai)i)ears in a minor syncline half a mile north of Sun- land. The axis of this minor syncline, and strikes of Rei)etto and Saugus beds to the north, swing northeast to form closure of the eastern end of the Little Tujunga syncline against the Sunland fault. The alluvium of Tujunga Valley is probably underlain by a minor anti- cline involving the Modelo formation {p\. 3, geologic section CC')- The Verdugo Mountains, Pacoima Hills, and Mission Hills comprise au elevated, faulted, anticlinal block trending N. 75" W. across the ([uadrangle. The struc- turally (and topographically) highest part of this block is in the central part of the Verdugo Mountains where granitic rocks are exposed. This structural feature, flanked by the Topanga (?) and Modelo formations, plunges westward to the vicinity of Hansen Flood Con- trol Basin. Uplift on the Pacoima fault exposes granitic rocks and the Topanga ( ?) formation in the Pacoima Hills ; then the anticlinal structure plunges westward an estimated 8,600 feet in the next 4 miles (pi. 2, and Tabulated list, well location 123. depth of Topanga (?) formation). In the Verdugo Mountains, the Modelo formation, overlapping Topanga (?) volcanic rocks onto granodiorite, has been folded into a group of small folds with rather gently dipping flanks. The dominant fold of the Mission Hills is the east- trending Mi-ssion Hills anticline which exposes diatoraa- ceous shale of the Modelo formation at the southeast end of San Fernando Reservoir. The strong westward plunge of this anticline is indicated by Repetto, Lower Pico, and Sunshine Ranch beds which successively overlie ex- posures of the Modelo formation on north, west, and south limbs of the anticline. North and south limbs are faulted and complicated by numerous minor folds in the incompetent Modelo shale (pi. 3, geologic section AA'). For 2 miles northwest of the Mission Hills anticline, Sunshine Ranch and Saugus beds dip continuously northward on the south limb of the western extension of the Little Tujunga syncline. In the Little Tujunga area, .steeply folded and faulted beds of the lower Pleistocene Saugus formation are well exposed, lying on the pre-Tertiary crystalline complex. The pre-Saugus surface is exposed and obviously has been deformed by post-Saugus warping. The area there- fore offers an exceptionally good opportunity to examine the mode of deformation of massive and foliated crj'stal- line rocks under a relatively thin cover of much later unmetamorphosed strata. Hill (1930, pj). 158-161) con- cluded that "massive crystalline rocks may fold in an environment (zone') of fracture" and suggested the development of many closely spaced minor faults or Photo 83. Intricate folding of fine sandstone and shale beds of Modelo formation, Wentworth and Foothill Boulevard. Photo by Mary Hill. li).')81 San Fernando Qi'ADRANr.LE — Oakesiiott 103 frat-turcs as the "foklinfr" mechanism. Ihulson (1955, pp. 2();38 and 204()-204fl) used the Little Tn.junfra area as an example of folding- of unmetaniori)liosed strata superjaeeiit to massive basement roeks and stated that the "prime re(|iiisite for such folding is the weakeninij; of the basement roeks, prior to the deposition of the strata, tliroujrh the formation of zones of crushinp:, sys- tems of fractures or minor faults or a combination of two or more of these." Hudson differs from Ilill in em- phasizinfT that the basement in the Tujunn;a region is not massive but is a complex of gneisses and schists intrudetl by ma.ssive granitic and dioritic rocks. The writer would like to go back to his earlier state- ments concerning the "Little Tujunga anticline" (Oake- .shott, 1937. pp. 241-242) and the "very close relation- ship, in origin as well as in time, of the south-side folding and faulting." The body of crystalline rock underlying the Saugus strata should behave essentially as a competent mass with sufficient strength to lift the superincumbent load under an upward thrust provided by north-south forces. Over the axes of the folds stress would be at a minimum and the superjacent strata would be little disturbed (e.g., remnants of horizontal Saugus beds at crest of Little Tujunga anticline). On the flanks of the folds shearing stresses would be local- ized, reach a maximum at which high-angle thrust faults would develop (e.g., Lopez and Sunland faults and other faults of the Sierra Madre fault zone). Just how basement rock yielded when superjacent younger stratified rocks were folded is still a question. Basement rock of the Little Tujunga area is not by any means all foliated (pi. 1). East of Little Tujunga Canyon it is predominantly massive granodiorite con- taining a very minor amount of gneissic rock ; west of the canyon (down the plunge of the Little Tujunga anticline) much more of the gneissic and schistose roof- pendant rocks have been preserved. There is little to suggest any difference in reaction to stresses by the Saugus strata overlying these different types of crystal- line rock. SUMMARY OF HISTORICAL GEOLOGY AND GEOMORPHOGENY Pre-Cambrian Dating of the anorthosite-gabbro group of rocks in San Fernando quadrangle as Late pre-Cambrian has provided the western San Gabriel Mountains with a definite pre-Cambrian history. The only other dated pre- Cambrian unit is the Mendenhall gneiss which Was intruded by the anorthosite group. The Mendenhall gneiss is a granulite of obscure origin whose blue-quartz- feldspar gneisses, amphibolites, and biotite-hornblende gneisses may represent roeks of sedimentary, volcanic, and plutonie origin. Rocks comprising the Mendenhall gneiss were deposited or emplaced, subjected to deep- seated regional metamorphism, and then intruded by anorthosite-gabbro in pre-Cambrian time. Mvich later unloading and lowering of pressures and temperatures resulted in j)artial replacement of all the older minerals by quartz, biotite, and chlorite. Later Pre-Tertiary The very long period of time from Late pre-Cambrian to Lower Cretaceous is almost unknown in the western San Gabriel Mountains. At least three major groups of rocks probably represent parts of that interval : the Pelona schist, Piacerita formation, and "diorite gneiss." The mica-chlorite-albite schist, actinolite-albite schist, quartz-biotite schist, (luartzite. and actinolite-talc schist of the Pelona are regionally metamorphosed fine-grained sedimentary and volcanic rocks. They were probably deposited in seas, as suggested by their uniformity and widespread distribution around the western margins of the Mojave Desert. Competent workers have placed the age of the Pelona schist at various periods from pre- Cambrian to Mesozoic ; it- is known only that the.v ante- date the Cretaceous (?) granitic rocks. In late Paleozoic (?) time (Mississippian ?) wide- spread seas covered the San Gabriel Mountains area. Crystalline limestone and dolomite, quartzite, and gra- phitic schists, preserved as roof pendants of the Piacerita formation, are evidence of the marine invasion. The dio- rite gneis.s is a group of dark gneisses, metadiorites, amphibolite and biotite schists, and hornblende diorite which are intimately associated with the Piacerita rocks. Many are hybrids and migmatites of undetermined ori- gin and age but some were probably quartz diorite that intruded the Piacerita and older rocks. Northwest-trend- ing structures and the deep-intrusive character of .some of these rocks are suggestive of a possible northwest- trending orogenic belt developed in late Paleozoic ( ? ) time. Extensive exposures of granodiorite, quartz monzo- nite, and other granitic rocks, probably correlative with similar plutonie rocks in the Transverse and Peninsular Ranges, the Mojave Desert, and southern Sierra Nevada, show that the San Gabriel Mountains area was also in- vaded b}' plutonie rocks in Lower Cretaceous (?) time. No Lower Cretaceous sedimentary rocks are known in these areas; Upper Cretaceous sedimentary rocks form thick sections in other parts of the Transverse and Pen- insular Ranges but do not occur in the San Gabriel Mountains. It is probable that an ancestral San Gabriel mountain range was formed in late Jurassic-Lower Cre- taceous (?) time at which time the granitic invasions took place. It may have been chiefly a folded range but possibly an ancestral San Gabriel fault zone was initi- ated along the contact between the Mesozoic granitic rocks and pre-Cambrian Mendenhall gneiss. The ances- tral San Gabriel Mountains were certainly eroded to low level by the close of Cretaceous time as Paleoeene seas seem to have transgressed the area ; no record of the pre-Paleocene surface remains, however. Tertiary The presence of marine sandstone, shale, and conglom- erate of the Martinez formation as slivers in the San Gabriel fault zone for several miles across San Fernando quadrangle, thick sections of similar rocks on the north side of the San Gabriel Mountains at Rock Creek, and in the Tejon area northwest of San Fernando quad- rangle suggest that Paleoeene seas covered at least the western part of the San Gabriel Mountains. The nature of the sediments and pebble counts are consistent with deposition in a littorial zone along a more or less rugged coast with the shoreline not far north of the present San Andreas fault. Sources of the sediments may have been, in part, a higher-standing Mojave block. 104 California Division of Mines [Bull. 172 The presence of foraminifera of the Meganos, Capay, and Domengfine stag:es in a deep well in the ^Yhitney Canyon area, the ocenrrence of Domenfrine sandstone in outcrop in Elsmere Canyon, and so-called Eocene rocks in several Whitney Canyon area wells establishes the existence of Paleocene to middle Eocene seas at the ex- treme western margrin of the San Gabriel Jlountains. There is no evidence, however, that lower or middle Eo- cene seas extended north of the San Gabriel fault or more than a fraction of a mile east of the Whitne.v fault. Pebbles in the Domengiiie outcrop consist of rock types, including gneisses, granitic rocks, gabbro. and anortho- site, which could have been derived from the San Gabriel Mountains to the east. The topographic and structural high of the western San Gabriel Mountains has probably been continuously in existence during post-Paleocene time because Paleo- cene sediments were the last to be deposited completely across the area of the present mountain range. Middle Eocene seas at the extreme western end of the San Ga- briel Mountain area received sedimeiit.s which were prob- abl.v derived from the first uplift of the San Gabriel Mountains which began to take place east of the Whitney fault area. During late Eocene or early Oligocene time major movements took place in the San Gabriel fault zone to divide the developing eastern Ventura basin into two local provinces whose subsequent history was cjuite different. North of the San Gabriel fault, the synclinal Soledad basin was formed which received thousands of feet of fluviatile and lacustrine sediments and inter- bedded volcanic rocks. The highly colored fanglomerate and thin lake beds of the late Eocene (?) to early Miocene ( ?) Vasquez formation show that at this time the Soledad basin was a westward-draining semi-arid basin receiving sediments mostly from the San Gabriel Mountains on the south but some also from the Sierra Pelona on the north and east. First movements on the normal Soledad fault probably took place during early Vasquez time. Local beds of gypsum and borates suggest times of considerable aridity. Intermittent volcanism de- posited flows of vesicular andesite and basalt, breccia, and beds of ash. At the close of Vasquez deposition, local uplift, folding, and faulting took place along the north- ern and eastern margins of the Soledad basin, erosion followed, and nonmarine sediments of the Tick Canyon formation were laid down in late-lower to middle Plio- cene time. Topography and climate during Tick Canyon time were similar to the epoch of Vasquez deposition but probably less arid, as shown by the fossil remains of grazing animals. Tick Canyon deposition was closed bv local uplift and folding, followed in upper Miocene time bv a broadening of the Soledad basin and the exten- sive deposition of fluviatile, flood-plain, and lacustrine sediments of the Mint Canyon formation. Fossil flora show that lake-border, riparian, savanna, woodland, and chaparral habitats characterized Mint Canyon time. Climate was similar to the present, except that the region probabl.v had the savanna type of biseasonal rain- fall instead of Mediterranean. Numerous small lakes were formed from time to time and in some of them tuffaceous sediments were deposited ; the ash may have been carried in by winds from the Mojave Desert area. Mint Canyon time was closed by slight uplift and gentle folding and in the late Miocene (late Mohnian- Delmontian) the western part of the Soledad basin was invaded by shallow seas from the west. During the time of Vasquez deposition the central part of the western San Gabriel Mountains was being elevated as a mountainous area. No sedimentary record has been found in San Fernando quadrangle for this interval south of the San Gabriel fault ; it is quite probable that the area was above sea level and w^as undergoing erosion. Lower (?) to middle (?) Miocene time on the south side is represented b}- continental red and yellow arkose, conglomerate, and interbedded flows of andesite and basalt. These beds appear to grade west- ward (also southward ?) into shallow marine deposits of the Topanga formation. These continental beds may be in part equivalent to the Tick Canyon formation. In middle Miocene time (Luisian), seas of the Ventura basin advanced from the west and south into the San Fernando basin and by upper Miocene time (Mohnian) had extended to a shoreline on the foothills of the western San Gabriel Mountains approximately as far north as the Sierra ]Madre fault zone. In these sea.s were deposited the sediments of the Modelo formation. At this time the Verdugo Mountains were largely above sea level ; at their western end basal Modelo conglomerate of Mohnian age is exposed on granodiorite and beds of the Topanga (?) formation. At the close of the Miocene epoch some movements took place on the San Gabriel and related faults and the Modelo seas receded to a minor extent. Activity on the San Gabriel fault must have been very minor during lower Pliocene time, for sediments deposited in shallow seas of that epoch extend completely around the margin of the mountains from Sunland on the southeast through the Whitney Canyon area to Humphreys syncline on the northeast. At the extreme western end of the moun- tains, lower Pliocene seas extended farther into the crystalline-rock margins of the San Gabriel Mountains than did the late Miocene seas, but through the area of the Little Tu.iunga syncline the reverse is true. North of the San Gabriel fault, lower Pliocene closed with strong local folding and uplift. The mid-Pleistocene orogeny was forecast during middle and upper Pliocene time by significant uplift, accompanied by some faulting and folding, which sharply changed environments of sedimentation. Middle Pliocene seas extended eastward from the Ventura basin only as far as the Mission Hills area and a small embayment in Placerita Canyon ; they did not enter the Soledad basin. The mid-Pliocene seas persisted into upper Pliocene time only in Placerita Canyon. In that area were marginal seas which alternated with brackish- water, flood-plain, lacustrine conditions during upper Pliocene time. Throughout the western part of San Fer- nando basin and in Soledad basin, just north of the San Gabriel fault, brackish-water, lacustrine, and fluvia- tile environments prevailed during upper Pliocene time. Rapid erosion of a rising San Gabriel mountain range (still much lower and less rugged than that of the present day) furnished the clastic sediments of the Sun- shine Ranch member of the Pico formation. 19581 San Fernando Quadrangle — Oakeshott 105 Quaternary Rise of the western San Oabriel Mountains, which had furnished clastic sediments of the upper Pliocene Sunshine Ranch member (maximum thickness in the western San Fernando basin) was accelerated duriiifr lower Pleistocene time. The Saujrus formation, repre- senting fluviatile and ali\ivial-fan sediments derived from the lower Pleistocene San Gabriel Mountains, is spread over 17 square miles of San Fernando (luad- ranjrle on the western slopes of the mountains and over much lar^rer areas to the west where it merg:es into marine sediments. Maximum thickness of the formation is in the re-entrant formed by the change in strike of the Little Tu.iunpa syneline and Sierra Madre fault zone, between Lopez Canvon and upper San Fernando Reservoir. There the Saugus formation is at least 10 times as thick as it is in the Soledad basin. Remnants of Saugus beds as high as an elevation of 3.000 feet east of Little Tu,iunga Canyon reflect greater original extent of the formation and the effects of post-Saugus orogeny. Certainlv the San Cxabriel Mountains in San Fernando quadrangle were lower and liad less relief than at pres- ent, for the Saugus alluvial basins were much more extensive than alluvial basins of Recent time. Saugus drainage patterns and depositional basins need not have been much different from the present, but rainfall and run-off in Saugus time may have been greater. The existence of streams in Saugus time which headed at least as far back in the San Gabriel Jlountains as at present is indicated b.v the abundance of anorthosite pebbles in the Saugus formation. For example, the preponderance of anorthosite pebbles in the upper Little Tujunga-Watts Ranch area suggests a big alluvial fan and flood plain, possibl.^- of a larger ancestral Gold Creek. The pre-Saugus surface, where exposed, is one of low relief. It seems likel.v that the subdued surface at the crest of the San Gabriel ]\Iountains, most notice- able east of San Fernando quadrangle, is to be cor- related with the late Pliocene pre-Saugus erosional sur- face. The ma.ior drainage courses, such as the Santa Clara River, Big Tujunga River, and Pacoima Canyon had probabl.\- become well established b.v late Pliocene- early Pleistocene time. The mid-Pleistocene orogen.v was the major event in building of the modern San Gabriel Mountains. At that time, the Saugus and all older formations were intensely folded bv north - south - acting forces, large movements took place in the San Gabriel fault zone, the Sierra Madre fault zone was developed, initial movements on some, and renewed movements on others, took place along a s.vstem of northeast-trending faults in the north block of the San Gabriel fault zone, and the central cr.vstalline-rock ma.ssif was elevated thou- sands of feet. Elevation renewed erosion and also in- itiated changes in local climate ; the Soledad basin and north slopes of the range became more arid than the crest and southern (windward) slopes. Some of the first products of post-Saugus erosion are repre.sented in the dark-brown and reddish fanglomerate of the Pacoima formation. Strata of this formation have been locally folded, in and near fault zones, particularly in the Sierra Madre fault zone west of the Veterans Hos- pital. Post-Saugus erosion of the higher lands has continued through upper Pleistocene to the present time. Erosion during this time has been modified, accelerated, or in- terupted by repeated almost vertical elevations. Major streams, like Big Tujunga, Pacoima, and Santa Clara Rivers, have developed very steep-sided can.vons, as much as .3,000 feet deep, which have cut headward into the pre-Saugus surface of erosion but have not yet destroyed it. Their tributaries, in their middle courses, are almost impassable in many places, because of falls and extremely steep gradients. Pre-Saugus drainage courses, like Pacoima Canyon, have become deeply in- cised and in part superimposed on older rocks. A suc- cession of terraces produced bv stream erosion has been developed, and numerous terraces, which represent stream-channel and flood-plain deposits, alluvial fans, and talus accumulations, are found at many different elevations. Most of the terraces parallel present drainage courses and were therefore quite evidentl.v left by these streams in earlier cycles of erosion. There is evidence in the greater-than-present width of some of the upper Pleistocene erosional and depositional terraces that the streams responsible for their development were operat- ing in somewhat broader channels and at lower gra- dients than at present. This is true, for pxami>le, in the Bouquet Can.yon-Plum Canvon-Santa Clara River area. The terraces are discontinuous, were formed at different times and at man.v different levels. It is not possible to suggest an.v correlations between the non- marine terraces in San Fernando quadrangle and ma- rine terraces of the Ventura coast, or to get any idea of their relationship to late Pleistocene history elsewhere. The best that can be done is to recognize some very local relationships between individual terraces within a very limited drainage area. Such comparisons show a.s many as five late Quaternary epochs of deposition and uplift. Tlie San Gabriel Mountains in San Fernando quad- rangle today are, in general, in the early mature stage of the erosion cycle. They have high relief and are steep and rugged. Their draina^re is into the Santa Clara River from the north side, and on the south side via Big Tu- junga, Little Tujunga. and Pacoima Rivers to the Los Angeles River. The semi-arid Mediterranean climate, with its intermittent winter rainfall, causes these streams to carry tremendous loads of sediment at times of high rainfall and to perform little or no work during the dry seasons. Consequently, broader alluvial fans and plains have developed in the valley of the Santa Clara River and in the San Fernando basin. The greater discharge of the south-side streams has caused the deepest and broadest fans to develop in San Fernando Valley. Depth of Recent alluvium in some quite narrow valleys, like those of Sand Canyon at Bear Canyon and Pacoima Canyon at Dagger Flat, suggests that some streams which were only ver,v recently degrading their channels are currently aggrading. ECONOMIC GEOLOGY Geologic Occurrence of Mineral Deposits The complexity of geologic historv of San Fernando ([uadrangle is reflected in the large number of mineral commodities found there. Of California's 75 mineral commodities, 25 have been found in San Fernajulo quad- 106 California Division op Mines Table 10. Cum illative mineral production in San Fernando quadrangle to December 31, 1953. [Bull. 172 Commodity Mines or areas Years of production Estimated amount produced Estimated value (in dollars) METALS No production No production No production Mid-1930s and earlier Cobalt Pacoima Canyon and Slaughter Canyon Gold --- 435,000 (?) Spanish mine (lode), Tick Canyon area Utopia {Champion, lode), Tick Canyon area.. Placers in and near Bouquet Canyon Placers in Gold Creek 1920-38 Before World War I 18808. 1890s. 1930s 1918-47 Walker Ranch placers, Placerita Canyon Early 1800s to 1949 •> No production No production 1944-52 1927-28-- 150.195 Uranium and thorium Limerock Canyon (?) and upper Pacoima Canyon No production Total metals (approximate) 600,000 MISCELLANEOUS NONME- TALLIC MINERALS 1929 Pliocene sedimentary rocks in west part of No production No production 1908-22 100.000 tons ... 3.000,000 McAnany & Rice, et al. in upper Limerock 1918-27 Several hundred thousand Under 76,000 Mint Canyon __ No production Prior to 1937 Mica ? over 3.000,000 ROCK PRODUCTS Before 1937 Few tons for cleanser 40 tons for ceramic use 5-10 tons per month for poul try grita Unknown 1.000.000 tons ? 1939 9 1950 and later 1920 Diatomite (see shale) Feldspar (see Anorthosite) 1912-27..- 350,000 1938-40 962,500 1800s (lime).. Unknown 1940s (poultry grit).- 1944 52 60.000 Sand and gravel .- 1925-29 400 000 tons 200 000 Santa Clara River 1948-53 Over 60 000 tons 36 000 Tujunga Wash _ _ 1925-53 Over 5,500,000 tons 4.000 tons 3.300.000 Shale 1950-53.- 20.000 1950-53 Over 600 tons ? 1937-40 Several thousand tons Total rock products Over 4,928,000 PETROLEUM Placerita oil field . _. _. 1920-47 (Minor) 21 291,780 bbls. 1948-53 42 748 600* 1893-1937 Few thousand bbls 285 000 bbls. Approx. 10.000 1891-1929 Approx. 400,000 1899-1901 Few bbls Total petroleum (approximate) 43,000.000 TOTAL MINERAL PRODUCTION 51.500,000 • Computed by multiplying posted prices of oil l)y annual totals of production. raiijrlp and 11 have been produced in significant amounts, (iimulative mineral production to the end of 1!)53 (table 10) has amounted to an estimated value of over $51,000,- 000. Petroleum (principally from Placerita oil field) accounts for $43,000,000, or approximately 84 percent of thi.s; rock products nearly $5,()00.()0(), or 9 percent; bo- rates (from the Lan;^ or Sterlinjj mine) $3,00(),0()(), or 6 percent; and the metals (gold and minor amounts of titanium ore) ajjproximately 1 percent. Geologic occurrence of mineral commodities of actual or potential commercial importance is summarized in the accompanying table (table 11) which shows the host rock for each deposit. Pre-Cambrian rock formations comprise a series of ancient gneisses and schists, intruded by the anorthosite- gabbro family of rocks. Anorthosite, nearly pure soda- lime feldspar about 27 percent alumina, is a potential source of aluminum, has been quarried as an abrasive and for poultry grits, and has been successfully tested for use as aggregate for pozzolanic concrete. Titanifer- ous magnetite (intergrowth of ilmenite and magnetite) is a late product of the magmatie processes that formed the anorthosite, gabbro, and related rocks. The high phosphate content of some of the apatite-rich pyroxenites and norites may eventually be of economic interest. Ti- taniferous magnetite is the major potential source of 1958 1 San Fernando Quadrangle — Oakeshott 107 ilmenite in California. Some of tlie later pre-C"anibrian jH'^'inatites carry small proportions of rare minerals, in- cludinfr uranium and thorium. In addition to the eco- nomic minerals formed in itre-Cambrian time, the pre- Cambrian rocks liave been atfected by much later miner- alization and act as host rocks for quartz veins carrying; frold and sulfides, probably formed by hydrothermal action in connection with {.^ranitic intrusions of late Jurassic or Cretaceous age. Crystalline limestone, dolomite, and frraphite schist of the Paleozoic Placerita formation have all yielded ma- terials of commercial value; these old fractured schists and gneisses are the reservoir for light oil in the Schist Area in Placerita Canyon. Granitic rocks of early Cretaceous (?) age have been utilized for granite blocks and facing, crushed stone for roads, and decomposed granite for road-base material. Mineralization in the late pegmatitic and hydrothermal stages connected with the period of granitic intrusion has developed the pegmatites which have been explored for quartz, feldspar, and mica, and the quartz veins, some of which carry sulfides and gold. The Tertiary sedimentary formations include rock units or strata of value in themselves and also act as reservoir rocks for petroleum. Some of the nonmarine strata of the Oligocene ( ?) Vasquez formation have interbedded gj'psum or borates, probably both formed in lakes in an arid climate. Glassy tuff beds of the non- marine upper Miocene Mint Canyon formation and dia- tomaceous shale beds in the marine upper Miocene Modelo formation have been mined. Sandstone of the marine lower Pliocene Repetto formation is the principal reservoir rock for petroleum in the Placerita oil field and nearby areas; marine upper Pliocene Pico sandstone and some of the nonmarine upper Pliocene Sunshine Ranch sandstone are also oil-saturated. Source of the petroleum is unknown but likely possibilities are organic marine sediments of upper Miocene and Eocene age. Quaternary alluvial sand and gravel have been mined for placer gold and titaniferous magnetite, but by far Table 11. Summary of economic geology. Geologic age Rock units Mineral deposits E 3 o c c Stream sand and gravel Sand, gravel, crushed rock, placer gold, placer ilmenite- magnetite 2. 'I £ Cm Terrace deposits Placer gold o N O K H .s k, V H 0) c o Chiefly marine sandstones of Repetto fm.; also Pico fm. Oil and gas; outcropping bituminous sandstone c o Marine diatomaceous shale of Modelo fm. Shale (carrier for insecticide) Volcanic tuff beds in continental Mint Canyon fm. Tuff (chinchilla dust; burnt for roofing granules) .1? Nonmarine conglomerate, sandstone, and siltstone with g>"psiferous and borate-bearing beds, of \'as- quez fm. Borates Gypsum y »-^ o N o 0) s Cretaceous or Jurassic Granite pegmatite Muscovite mica, quartz (silica), potash feldspar, moK'b- denite Granite, granodiorite, quartz monzonite Crushed rock, decomposed granite, dam facing, gold- and sulfide-bearing quartz veins. 6£ 2g Crjstalline limestone and dolomite, and other meta- sedimentarj- rocks of Placerita fm.: dark gneisses and schists of undetermined age. Limestone (lime, poultry grits), small amount of lipht oil, graphite. z, < Anorthosite, gabbro, norite. metapyroxenite, titano- magnetite group of rocks. Anorthosite (abrasive for cleanser. poultr>- grits, pozzo- lanic cement), titaniferous magnetite (pigment, roofing granules, weight for rollers), quartz veins bearing gold and sulfides of antimony, cobalt, copper, lead, silver, zinc, pegmatites carrying uranium and thorium minerals. 108 California Division of Mines [Bull. 172 the greatest value of the Recent stream gravels is as a source of sand, gravel, and crushed stone for concrete aggregate ; this mineral production is second in value only to petroleum, in the quadrangle. Metals Antimony In some places small crystals of stibnite (antimony sulfide) are asssociated with the complex sulfide ores on the Indicator and Ore Hills groups of claims in Pacoima Canyon (see Tabulafion of Mineral Deposits, under Lead-Silver-Zinc). The occurrence is not an economic source of antimony. Chromium Chromite has been reported in the western San Gabriel Mountains but Murdoch and Webb (1948. p. 104) are probably correct in ascribing such reports to mis- identification of titaniferous magnetite, so abundant in the area and so similar in appearance to chromite. Ultra- basic gabbroic rocks in the Pacoima Canyon area, high in ilmenite-magnetite, were observed in thin section to carry a small percentage of green chrome spinel in some specimens (Oakeshott, 1937, p. 243). Cobalt Cobalt occurs in the complex sulfide ores on the Indi- cator and Ore Hill groups of claims in Pacoima Canyon. The element may be in nickeliferous pyrrhotite at this lo- cality, but also occurs sparingly as nickel bloom coatings (annabergite, NisAsgOs-SIIoO) as reported by D'Arcy (1939, p. 269), and Murdoch and Webb (1948, p. 50). (See Tabulation of Mineral Deposits, under Lead-Silver- Zinc, herein). Copper Traces of copper sulfides and carbonates are found in a number of localities in the western San Gabriel Moun- tains but there has been no copper production. Chalco- pyrite occurs in the complex sidfide ores on the Indicator and Ore Hill groups of claims in Pacoima Canvon (Tucker, 1920, p. 318, Murdoch and Webb, 1948, p." 95, and Tabulation of Mineral Deposits, herein). Chalco- pyrite, in very small amounts, is associated with molyb- denite and pyrite in granite pegmatite which intrudes gabbro-anorthosite in Slaughter Canyon (Oakeshott, 1948, p. 258, locality Trail Canyon 4). Gold The date and circumstances of the discovery of gold iji southern California remain somewhat uncertain but there is no doubt that the discovery was made at least several years before Marshall's more famous discovery at Sutter's Mill in 1848. It is likely that the mission fathers from San Fernando and San Btu'na Ventura missions worked placers in the area in the 1830s. Cutter (1948), in summarizing accounts of the discovery of gold, notes that the first shipment of California gold dust reached the U. S. Mint on July 8, 1843 from a resident of Los Angeles. In 1930, the Native Sons of the Golden West erected a monument under a big oak tree on the north side of Placcrita Canyon, 1.3 miles cast of Sierra Highwaj' (U.S. G), connnemorating tlie discovery of gold by Francisco Lopez, while digging wild onions on March 9, 1842. In 1955, the State of California acquired the discovery site for a state park, to be administered by the Department of Natural Resources, Division of Beaches and Parks. Access is by a new road 1.3 miles long from Sierra Highway, where a plaque directs visitors to the "Oak of the Golden Dream." Geology. Gold-bearing quartz veins in San Fernando quadrangle are quite widely distributed, both geograph- ically and geologically. They cut crystalline rocks of all types and all ages, from Pre-Cambrian to lower Creta- ceous ( ?), but are probably related to the granitic rocks of the later age. Jlany of the veins have been explored and mined for brief periods but they are generally thin and discontinuous. Erosion of the veins has resulted in concentrations of gold in older alluvium in some of the stream valleys, but principally in Recent sands and gravels of most of the larger streams. Localities and Production. The first period of gold mining in San Fernando quadrangle was in the mid- 1800s when several placer mines in Placerita Canyon, and other stream valleys, were in operation. This was followed by lode mining, beginning at an unknown date, at such j)roperties as the old Spanish mine in the Tick Canyon area. There was renewed activity in gold mining ill the early l!)00s, and in the depression years of the 1930s when hundreds of people were placer mining in the Bouquet Canyon area, Placerita Canyon, Pacoima Canyon, and the Little Tujunga drainage area. Gold milling in the San Fernando area has been se- verely handicapped by the scarcity of water; most of the streams dry for a large part of the year, and the more distant sources of water generally are not econom- ically practical. Dry placering methods have been used but recovery by such methods is inefficient and not prof- itable for low-grade deposits. Estimates of the value of early-day production are diffieidt to make as there were many miners and production was often unreported. How- ever, there is little question that several hundred thou- sand dollars in gold has been mined in the quadrangle. Placer Mining. Placer mining in Placerita Canyon has been carried on intermittently for well over 100 years. There is evidence that the older brownish coarse bench or terrace gravels on the north side of the canyon, 50 feet or more above present stream level, were thor- oughly turned over in mining for a mile downstream from the Lopez di.scovery site. Frank E. Walker and sons have recovered coarse gold from similar bench gravels in the Placerita fault zone on the south side of the canyon about a mile farther upstream. A number of old buildings at the Walker mine indicate a more or less continuous operation many years ago. Above the mine on the South Fork of Placerita Canyon, thin irregular quartz veins cutting crystalline rocks of the Placerita inetasedinientary formation, quartz diorite gneiss, and granodiorite suggest the lode source of the placer gold. Gravels of Bouquet Canyon and its tributaries — Coarse Gold, Texas, and Vasquez Canyons — yielded sev- eral thousand dollars in gold in the 1880s and 1890s, were worked intensively in the 1930s, and Sporadically since 1948. Coarse Gold Creek (not named on map but running southeast across section 29 into Bouquet Can- yon) shows evidence of intensive placer operations and jiroduced several thousand dollars worth of gold between 10.")81 San Fernanpo QrADKANOLE — Oakeshott 109 1931! aiiti 1!I35. accordiiif; to .loliii Kaspcr in lioiKiuct Canyon. Pat-oima Canyon, from Dutch Louie Camp to Dafrger Flat, in an area wliere tlie stream jrravels are deep and rich ill titaniferous magnetite sand.s, has been intermit- tentl.v worked for grold. At one spot tlie stream has been bypassed through a rock si)ur by way of a shaft and tunnel. The Little Nugget Placers in Gold Creek produced several thousand dollars in gold, at times, between 1918 and 1947. Lode Mines. Lode gold prospects are distributed widely through the crystalline rock formations of the cjuadrangle but in only two localities — upper Tick Can- yon (Spanish. Toney, and Champion or Utopia mines) and Bear Canyon (Acme mine) — has there been any significant production. Other lode prospects are in Oak Spring Canyon, Xehr Canyon. Pole Canyon, and Pa- coima Canyon. The Spanish mine is a very old property with several hundred feet of workings, including four adits and two shafts. It is not known when it was first worked, but several thousand dollars in gold, and some silver, was produced between 1920 and 1938 ; latest development work was in 1948. Gold- and sulfide-bearing quartz veins in gneissoid granitic rocks have yielded free-milling gold. The Champion, or Utopia, mine produced several thousand dollars in gold before World "War I. About 1000 feet of tunnels and several hundred feet of shafts have developed four parallel quartz veins 2 to 4 feet wide which cut Upper Jurassic (?) or Cretaceous (?) gneissoid granitic rocks. Assays of 0.55 ounces of gold per ton have been reported. The mine was under lea.se in 1953 for production of graphite (Gav and Hoffman. 1954, p. 619). The Acme mine, on the west side of Bear Canyon tributary to Sand Canyon, has been inactive since the mid-1 930s. Prior to that time, the mine produced $435,000 in gold, according to Challoner Thompson in Sand Canyon. Underground workings of unknown ex- tent, now inaccessible, developed quartz veins cutting gabbro-norite in the area. Lead-Silver-Zinc A series of parallel discontinuous quartz veins is exposed on the north side of Pacoima Canyon between Tjaurel and Gooseberrv Canvons in sections 10 and 11, T. 3 X., R. 14 W. The vein system strikes N. 80° E., along Pacoima Canyon, and dips steeply south. The ore consists of complex sulfides of antimony, cobalt, copper, iron. lead, nickel, and zinc, and carries gold and silver. Recognizable minerals are stibnite. nickel bloom (an- nabergite. Xi:(As:.Os'8H20), ehalcopyrite, niekeliferous pyrrhotite, galena, and sphalerite (Tucker, 1920. p. 318; D'Arcy 1939. p. 269. Murdoch and Webb 1948, p. 50). The veins are 2 to 4 feet wide, but locally the vein system is 50 feet in width. The quartz veins are probably hydrothermal in origin and probably related to the end-stage of the Lower Cretaceous ( ?) granitic intrusion. They cut a thoroughly jointed and fractured complex of the more basic facies of the pre-Cambrian gabbro-norite-metapyroxenite group ; the rocks include gabbro-norite gneiss and chloritized and tremolitized titanomagnetite pyroxenite. The vein s.vstem is parallel to and 1/10 of a mile north of the Mendenhall gnei.ss. The contact is quite probably a fault here, but about 2 miles to the west the gabbro-norite clearly intrutlcs the Mendenhall gneiss. Development work has been carried on at intervals, from the time of World War I to the present — there are a number of old shallow shafts and adits. Although there is no record of any production, in 1951 another shaft was sunk on the Ore Hill group. Molybdenum A few flakes of molybdenite have been found in granite pegmatite which intrudes gabbro-anorthosite in Slaugh- ter Canyon (Oakeshott, 1948, p. 258. locality Trail Canyon 4). Titanium * Numerous bodies of titaniferous magnetite (ilmenite- magnetite) occur in the San Fernando quadrangle and ad.iacent Tujunga lo-minute quadrangle, on the east, in association with the anorthosite-gabbro-norite group of rocks. Thirty -six deposits were located and described in an earlier report (Oakeshott, 1948); 19 of these, which occur in San Fernando quadrangle, are listed in the Tabulation of mineral deposits herein. These deposits represent the largest known reserves of tita- nium in California but none were being exploited as late as 1954. The ore in single deposits ranges from a few tons to several hundred thousand tons, and in grade from less than 3 to 25 percent TiO^. Geology. Titanium-rich rocks in San Fernando quad- rangle consist of the pre-Cambrian anorthosite group — anorthosite, gabbro, norite. and pyroxenite — sufficiently high in ilmenite-magnetite to be of possible value as a source of titanium. Titanomagnetite, or ilmenite-mag- netite, is an intergrowth of the two minerals ilmenite (FeO-Ti02) and magnetite (FeO-FeoOs) in various proportions. These minerals are in many places .so finely intergrown as to make their separation by magnetic, or other mechnical means, extremely diflfieult ; this is one of the major problems in utilizing the titanomagnetite ore. Ilmenite-magnetite is associated with augite, hyper- sthene, and apatite ; the pyroxenes are nearly completely replaced by chlorite and actinolite. The ilmenite-mag- netite-bearing rocks occur as irregular, poorly defined masses that grade into anorthosite. gabbro-norite. and metapyroxenite ; as more sharply defined dike-like bodies in such rocks; and as elongated bodies whose emplace- ment was apparently guided by fracturing of the an- orthosite group of rocks. Ilmenite-magnetite is also an accessory in the anorthosite-gabbro-norite rocks. The ilmenite-magnetite intergrowth was formed by very late igneous processes in connection with the in- trusion of gabbro-norite and anorthosite. It commonly makes up a few percent of the basic facies of the gabbro- norite. the intergrowth partially replacing the original magmatic minerals of the rock and occurring late in the series of deuteric or pegmatitie minerals. The process of late-magmatic replacement to form ilmenite- magnetite began before final consolidation of gabbro- • See ilmenite-magnetite in Tabulation of mineral deposits. Modified from Oalteshott (1948 and 1949). no California Division of Mines [Bull. 172 norite and anorthosite and continued after the magma had consolidated sufficiently to fracture. Umenite-mapr- netite is most abundant in the metapyroxenite fades in San Fernando quadrangle. Erosion of the ilmenite-magnetite-bearing rocks has developed sands quite high in ilmenite-magnetite in the stream valleys, particularly in Sand Canyon and in Pacoima Canyon. Nearly pure ilmenite-magnetite rock is very resistant to weathering, but the alterated gabbro- norite and metapyroxenite break down readily to yield sands which are concentrated by stream action to form 2 to 31 percent titanium oxide (TiOa). History of Development and Production. The first attempt on record to utilize the ilmenite-magnetite ore of the western San Gabriel Mountains was at Russ Siding in Soledad Canyon in 1906 (pi. 2, locality 45). An oil furnace was built within a few feet of the South- ern Pacific railroad tracks and the ore was brought from a small, rich ilmenite-magnetite body nearby. Apparently the project was initiated with the idea of using the iron, and without recognition of the high titanium content. It was abandoned when the refractory nature of the ore was recognized. Remains of the operation were still evident in 1954. The largest mining operation, now idle, was the Iron Blossom mine of the Mineral Increment Company, 2.4 miles in an airline southeast of Lang Station on the ridge between Pole and Bear Canyons. Several irregular ore bodies a few feet across, roughly lenticular, occur with irregular masses of white anorthosite ;' but the principal country rock is gabbro-diorite. A road was built to the property and 10,013 tons of ore valued at $150,195 was mined in 1927-28 and carried to a bin in Soledad Canyon for shipment to El Segundo for the manufacture of paint base. The DuPont Company made experiments to separate the titanium from the iron without economic success.* Development work con- sisted of several adits, one at least 300 feet long; aban- doned equipment includes a small crusher, engine, a large ore bin, 100 feet of track, and several houses. Numerous evidences of prospecting activity in connec- tion with the titaniferous deposits were found by the writer, and supported by oral reports from miners and prospectors of the region. Nearly all these localities have iiad claims filed on them, but most claims have lapsed or changed hands and present ownership is unknown. The most extensive and systematic prospecting was done by E. I. du Pont de Nemours and Company, reportedly beginning in 1927 and continuing until 1938. Since that year the company has abandoned all claims. ** A pro- jected diamond-drilling campaign for the spring of 1938 was not carried out. The company is said to have (iroi)ped its interest because of more inunediately attrac- tive deposits ami more easily mined sources of raw nui- tcrials elsewhere. A small tonnage of ilmenite and magnetite concen- trates was i)roduced between 1944 and li)52 by Challoner Thoiui)son from placer sands at the Live Oak mine (pi. 2, locality 41) in Sand Canyon. At that mine, natural sand averaging about ly^ percent TiOj was .screened to • Spangler Ricker, unpublished report, V. S. Bureau of Mines. •• Written communication, April 2, 1955, from J. L. Gillson, E. I. du Pont de Nemours and Company. minus 40 mesh and run over electromagnets. An ilmenite concentrate containing 59.3 percent ilmenite and 16.2 percent magnetite, and a magnetite concentrate of 61.0 percent magnetite and 18.5 percent ilmenite were ob- tained. Some of the magnetite concentrates were sold for roofing granules and for weight in heavy rollers; the ilmenite concentrates were sold for a short time to San Gabriel Pigment Company at Roscoe, Los Angeles Count.v, for the manufacture of an opaque pigment. Shafts in the alluvium, .sampling, and a magnetometer surve.v (Dehlinger, 1943) suggest that several million tons of titaniferous sand are available at this locality in Sand Canyon. The Pacoima Canyon titaniferous sand deposits (pi. 2, localities 58 and 59) from Dutch Louie Camp to Dagger Flat were panned for gold but have not been wo"-! cd for titanium. Several million tons of workable .saiui aiin gravel containing from 2.4 to 30.8 percent TiOj arc present but the area is much less accessible to transpor- tation than Sand Canyon. Holes dug in the Pacoima Canyon alluvium indicate that average thickness of the sand and gravel is about 40 feet. Uranium and Thorium Neuerburg (1954, p. 831-834) has reported a pegma- tite in the noritic facies of the anorthosite mass in upper Pacoima Canyon which contains crystals of allanite (complex silicate containing cerium, lanthanum, and probably thorium), apatite, beryl, uranothorite (ura- nium thorium .silicate), and purplish zircon. The allanite, uranothorite, and zircon are all radioactive but do not provide a commercial source of uranium. In late 1954, a flurry of excitement occurred when a prospector reported uranium in Limerock Canyon, west of Little Tujunga Canyon. A large number of claims was staked, most of them illegally on private land, pat- ented claims, and withdrawn land of Angeles National Forest. The rock reported as ore is qiiartzite of the Plac- erita series ; specimens from the locality were cheeked by Geiger counter, in the Division of Mines laboratory, with negative results. Miscellaneous Nonmetalllc Minerals Asbestos About 50 tons of asbestos was mined in 1929 from the Fiber Queen mine in Sehoolhouse Canyon 1.3 miles north of F'ootliill Boulevard in the San Gabriel Mountains near San Fernando (Ga.v and Hoffman, 1954). Herman Mangold of Olive View mined and shipped the material to Portland, Oregan, for use as pipe insulation. Salem Rice * visited the propert.v in 1952 and described the material as "short-fiber tremolite asbestos of fair grade" in veinlets in the Placerita metasedimeiitary rock com- plex. This is an area in which roof pendants of the Plac- erita formation are intricately intruded by granitic rocks. The asbestos is in sheared rocks a few feet north of reverse fault that dips 60° N. An 80-foot shaft reported by Mangold could not be located, but two old adits cutting across the fault from the Elsmere sandstone into the Placerita rocks were still open in 1952. Evidence of some recent prospecting and location of claims was found. • Mining Geologist, California State Division of Mines. inrisi Sak Fernando Quadrangle — Oakesiiott 111 Bituminous Sandstone Bituminous sandstone is extensively exposed in out- crops near the western niarfrin of the quadraiifrle from the Santa Susana fault zone to the San (labriel fault, both east and west of the Wliitney fault. Fossiliferous coarse sandstone, conglomerate, fine sandstone and inter- bedded siltstone of the Elsmere member of the Repetto formation, Repetto siltstone and sandstone, and Lower Pico sandstone and siltstone are, in many places, oil- saturated, althoup-li most of the sandstone in outcrop is quite dry. Locally, the Sunshine Ranch ( ?) sandstone in Wliitney Canyon is oil-saturated. Most of the oil- saturated sandstone crops out in the drainage areas of Whitney, Elsmere, and Grapevine Canyons. Where bodies of oil-impregnated sandstone several hundred feet across can be observed, it can be seen that impregnation by oil is ver}' irregular, cutting across bedding planes and occurring in very fine to very coarse beds. Live oil seeps are numerous in this area, particularly in Whitney and Elsmere Canyons, where they were responsible, of course, for early well locations in those oil fields. Oil seeps are most common in the Pliocene formations, but some are found also in sandstone of the Eocene Domengine formation in Elsmere Canyon. No oil seeps have been found north of the San Gabriel fault. Very close to the northeast end of the Santa Susana fault, a live heavy oil seep was found in fractured diorite gneiss. Eastward from the Santa Susana fault, oil sand in outcrop is less extensive and oil seeps are less com- mon ; east of Lopez Canyon no seeps have been found. Borates One of the most important mineral commodities mined in San Fernando quadrangle was eolemanite, {CaaBeOn-SHoO), of which about 100,000 tons, valued at $'3,000,000, were produced from 1908 to 1922 from Tick Canyon, 3i airline miles north of Lang station (Gay and Hoffman, 1954). During this time the mine was operated chiefly by the Sterling Borax Company. After processing at the mine, a 50 percent boric oxide (B2O3) product was shipped to eastern refineries for the manu- facture of commercial borax (Na2B407- 101120). The borate minerals in the Tick Canyon area are found in the continental Oligocene (?) Vasquez forma- tion. The Vasquez formation consists of coarse red, green, and yellowish sandstone, mudstone. and con- glomerate, with interbedded andesite and basalt. The beds carrying commercial eolemanite are among the finer grained in the formation and consist of thinly bedded fine red and brown sandstone, mudstone, and purple silty shale, close to the top of the Vasquez forma- tion and between vesicular flows of basalt. The principal colemanite-bearing beds at the mine strike N. 75° W. and dip 70° S. A quarter of a mile west of the mine these beds are overlapped by the more gently dipping Tick Canyon formation which lies unconformably on the Vasfjuez formation. Less than a quarter of a mile east of the Sterling mine, the beds are offset approxi- mately 1,000 feet to the northeast by left -lateral move- ment on the Tick Canyon fault. East of the fault, the borate beds can be traced for about 2 miles (Birman, 1950) ; strike of the beds changes to due west but the steep dips are maintained. Geologic occurrence and origin of the borates have been discussed bv Eakle (1912), Poshag (1921), Gale (1914), Irwin" (1950), Jahns (1940), Jahns and Muehlberger (1954), and Ver Planck (1954). eolemanite (Eakle, 1912; Foshag, 1921; Gale. 1914) was the commercial mineral in the Sterling mine but other boron minerals found include howlite (H.r,Ca2B.-,SiO,4) in cauliflower-like growths, probertite (NaCaB-.Oa -51120) in flattened aggregates of irregularly radiating prisms found on the dumps, ulexite (NaCaB.-,b9-8H.,0) (Foshag, 1918), and veatchite (3Sr()-8B20:r5H20) in thin sil- very plates on fracture surfaces of gray shale and as nodular aggregates of plat.v grains. Veatchite was first found at the Tick Canyon locality and was described by Switzer (1938) as a new calcium borate; later Switzer and Brannock (1950) corrected the composition origi- nally given. Luce (1935) has made an interesting sum- mary of the occurrence of the borate minerals at Tick Canyon ; he also mentions analcite and natrolite, of interest to collectors, in vesicles of the Vasquez basalt. Colemanite is not found in playas as it is relatively insoluble in water. Eakle and Gale believed the site of the deposit was originally a marshy area with mud, marl, calcareous tufa and abundant organic matter, and that waters charged with boric acid converted calcium carbonate into calcium borate. Murdoch and Webb (1954) consider it likely that the area was a borax- ulexite playa, similar to the present floor of Death Valley, and that, after iiplift and tilting of the Vasquez beds, sodium was removed in .solution and the boron combined with calcium from calcareous sediments to form eolemanite. At least, geologists agree that the boron originated in the associated Vasquez volcanic rocks. Gay and Hoffman (1954) have investigated mining methods and the history of operation of the mine and give the following account : The eolemanite was mined through two vertical shafts, each H.'iO feet deep, from workings on the 100- 200- and 3()0-£oot levels and from numerous au.xiliary openings. The deposit was mined along a strike distance of 800 to 1,000 feet, one segment about fiOO feet long being mined on all three levels. Mining methods included the use of square-set stopes in some places and shrinkage stopes in others. The shrinkage stopes were about 70 feet long, 60 feet high, and 20 feet wide above the ore chutes. The square- set stopes were about 40 to 60 feet wide, 70 feet long, and 60 feet high. Pumping was required to keep the lower levels free of water. . . . In November 1907 eolemanite was discovered on the property, but production did not commence until 1908. The deposit was acquired by the Sterling Borax Company, a consolidation of borax interests including Stauffer Chemical Company's Frazier Borate Mining Company, American Borax Company (boric acid works at Daggett), Brighton Chemical Company (refinery in Penn- sylvania) and Thomas Thorkildsen and Company (refinery in Chicago) . During the earliest operations of the mine the eolemanite was sacked for shipment, but four oil-burning calcining furnaces were later installed. Two were wedge furnaces with a capacity of about 40 tons each per 24 hours ; the other two were horizontal furnaces 50 feet long with a capacity of 60 tons each. After the water of crystallization was driven out by roasting, the bulk of the admixed shale impurity was removed by means of an air current passing through a cone screen. A refined ore containing 48 to 50 percent boric oxide (B2O3) was produced in this way and shipped via a standard-gauge railroad built from the mine to I.ang siding of the Southern Pacific Railroad. The bulk of the refined ore was shipped to the several eastern refineries of the company for con- version to commercial borax. 112 California Division of Mines [Bull. 172 About SO mefl were pmi)lo,ved at the mine. The maximum dail.v production was about -MIO tons, and an output of nearly $500,000 worth of calcium l)orate was credited to the mine for the .vear ]!tl4 (Tucker. 1927, pp. :ilS-.'!l!l) . During World War I mine production was limited l).v a shortage of railroad cars available lor shipping the ore. T'npublished records of the California Divi- sion of Mines indicate that total production during the 16-.vear life of the mine was about 1(X),00() tons of ore valued at about :i million dollars. The mine .vielded a substantial share of the cole- niauite mined in the Vnited States from 1908 to 1920. During the latter portion. of the period 1911-18. during which the deposit was nearly mined out, the Pacific Coast Borax Com- pany entered into a sales agreement with the Sterling Borax Company, but did not own or operate the property. Faced with .in ever-declining price for borax and, as the mine grew deeper, with rising mining costs, the property was sold to Pacific Coast Borax Company in 1921. The new owners conducted a scavenging operation in which nearly all remaining colemanite was removed. The depletion of the known reserves of colemanite led to the final closing of the Lang mine in 1922. and dismantling of the plant in 1926. The development of a rich deposit of the sodium borate, kernite, at Boron in 1926 marked the cessation of the extensive mining of colemanite in the state. The Lang mine workings are now caved to an unknown extent and are flooded below the 150- foot level. The thin seams of colemanite remaining at the property are now sub-commercial and the siliceous borate, howlite, is not marketable. Chalcedony and Opal Chalcedony and opal are found in vesicles in Vasquez basalt in the northeast corner of the quadrangle in upper Santa Margarita Canyon. It is not high-quality gem material but has been frequently collected by amateur lapidarists. The rock is dark, fine-grained, brown-weath- ering vesicular and amygdaloidal basalt. Under the mi- croscope beautifully zoned plagioelase feldspar pheno- crysts, under 2 millimeters in length, averaging acid labradorite (An 60) in composition, appear in a fine groundmass. Small euhedral augite phenocrysts make up about 5 percent of the rock. The groundmass is hyalo- pilitic — made up of small feldspar laths with intersti- tial yellow-brown devitrified glass. Graphite Graphite occurs in three widely separated places in San Fernando quadrangle: (1) The area of Placerita metasedimentary rocks south of the San Gabriel fault between Pacoima and Little Tujunga Canyons; (2) In inclusions of schistose rocks in granite in the upper Tick Canyon area; and (3) In an inclusion of schistose rock in gabbro-diorite in the North Fork of Pacoima Canyon. The only production was from the McAnany & Rice (Kagel Canyon) deposit in upper Limerock Can- yon, where several hundred thousand pounds of small- Hake graphite were mined, and milled at the deposit, between 1918 and 1927. In the area south of the San Gabriel fault, graphite is one of the constituent minerals of the rocks of the Placerita metasedimentary formation, which includes crystalline limestone and dolomite, quartzite, biotite schist, graphite-albite schist, feldspar-tremolite schist, and graphite-biotite schist. In these rocks graphite ranges from scattered flakes to 25 percent. The Placerita formation has been injected by quartz diorite gneiss of late Paleozoic (?) age and also intricately intruded and metamorphosed by Jurassic or Cretaceous granitic rocks. Graphitic veinlets occur in dark gneissic inclusions in buff-colored, fractured, gneissoid biotite-museovite granite in the upper Tick Canyon area north of the Mint Canyon fault, in the workings of the old Champion gold mine and at the East Graceful mine. Graphite is found in a vertical shear zone in a dark gabbro-diorite facies of anorthosite in the North Fork of Pacoima Canyon. The dissemination of graphite in the metasedimentary rocks of the Placerita formation, south of the San Gab- riel fault, the interbedding of graphitic schists with the contact-metamorphosed sediments, and the association of graphite with contact-zone minerals such as garnet, epi- dote, diopside, tremolite, sillimanite, and albite-oligo- clase. are evidence of development of the graphite by crystallization of original organic matter in the sedi- ments. A more detailed account of the occurrence was given by Oakeshott (1937) ; somewhat divergent views concerning the origin of the graphite were expressed by Beverly (1934), who emphasized the importance of hydrothermal action. No rocks recognized as correlative to the Placerita formation were found north of the San Gabriel fault. Origin of the graphite found in sporadic occurrences in crystalline rocks north of that fault is unknown ; it may bear no relation in origin or age to the occurrence in the Placerita formation. McAuany and Rice (Kagel Canyon) Deposit. Graph- ite was mined in upper Limerock Canyon; near the Kagel Canyon divide, between 1918 and 1927. The graphite body mined is a graphite-quartz-feldspar (al- bite) schist interbedded with the Placerita metasedimen- tary formation ; it strikes N. 30° W., and dips nearly vertically. The ore mined carried about 7 to 15 percent graphite in small flakes, less than 0.25 millimeters in diameter. In 1920 the American Graphite Company was work- ing five claims in upper Limerock Canyon and had driven an adit 60 feet long into the deposit at an eleva- tion of 2,400 feet. A 50-ton concentration mill was built that year ; it included crusher, rolls, Marks pulverizer, tube mill, two Allingham flotation machines, and Oliver filter (Tucker, 1920, p. 3181. After producing several hundred thousand pounds (exact amount not known) of small-flake graphite (called "amorphous" graphite), the property was idled in 1927 and the mill was dis- mantled and razed in the mid-thirties. Considerable diffi- culty was found in separating the fine-flake graphite from the gangue minerals. That fact, and the difficulty in securing a profitable market for amorphous graphite, contributed to abandonment of the mine. Amorphous graphite produced in Los Angeles County in the 1920s was used largely for paint stock, foundrj- facings, and lubricants. Gypsum The Mint Canyon (Lang), deposit in upper Mint Can- yon in sections 29 and 30, T. 5 N., R. 14 W., is the only gypsum deposit in San Fernando (juadrangle which has been mined. It was explored in the 1920s, and in 1948 by open cuts about 150 yards along the strike of the outcrop (Gay and Hoffman, 1954). Steeply dipping contorted gypsiferous beds of gray sandstone and mudstone of the Oligocene (?) Vasquez formation strike approximately N. 70° E. and lie on coarse greenish sandstone, interbedded with thin beds 19581 San Fernando Quadrangle — Oakeshott 113 of purplish and greenish shale, a few feet above basaltic Vasquez volcanic flows. The gj'psiferous zone is about 15 feet thick but many individual layers of gypsum are a quarter of an inch or less in thickness, although a few are as thick as 6 inches. The gypsum occurs as fibrous satin spar and as massive rock gypsum, or alabaster. About 200 feet north of the deposits, the Vasquez forma- tion is cut off by the Mint Canyon fault. The gypsum at this locality is believed to have been deposited as lake beds at the time of deposition of the Vasquez sediments. The presence of numerous veinlets of satin spar indicates a redistribution of some of the gypsum by later percolating ground water. The deposit is readily accessible by dirt road connect- ing with Sierra Highway (U.S. 6). A loading platform was built at the outcrop, but there is no record of pro- duction. Mica Muscovite and biotite mica occur in granite pegmatite and in included older schists in several places in San Fernando quadrangle, but only a few tons of ground mica have been produced. Alkali granite pegmatite, composed of quartz, micro- eline feldspar and a small proportion of muscovite has yielded a small amount of mica from Santa Clara ridge near the junction of Santa Clara and Indian Creek truck trails (pi. 2, localities 69, 70, 72). About half a ton of muscovite was removed from the Apex claim (pi. 2, locality 69) for testing in 1939; no production fol- lowed (Gay and Hoffman 1954, p. 676). Prior to 1937 a plant was built in Little Tujunga Can- yon (pi. 2, locality 71), including a small hammer mill and two oil-burner furnaces (Sampson 1937, p. 199) to grind mica schist occurring as inclusions in granitic rocks on the east side of the canj'on. Two tons of musco- vite, ground to 40 to 80 mesh was sold to paint manufacturers. "Vermiculite, " on the Nora-Evelyn claims, was re- ported by Sampson (1937, p. 199-200) north of the Indian Creek road, but the deposit could not be located by the writer. Rock Products Anorthosite Pre-Cambrian gray to white anorthosite is exposed along the precipitous walls of Soledad Canyon for 7 miles in San Fernando quadrangle. The canyon is traversed by a two-lane, paved highway and by the mainline of the Southern Pacific railroad. Most of the outcropping anorthosite is about 95 percent basic andesine feldspar (sodium-calcium aluminum silicate). The average of eight analyses of specimens in and south of Soledad Canyon shows 55 percent SiOn, 27 percent AI2O3, 9 per- cent CaO, 5 percent NaoO, 0.6 percent K2O, 0.3 percent MgO, 1.3 percent iron oxides, and 1.7 percent water. Numerous attempts at commercial utilization of this nearly pure plagioclase feldspar rock have been made. Prior to 1937, the Gates Chemical Company quarried white anorthosite near Alpine station in Soledad Can- yon, ground it, and marketed it under the name of "Gates Cleanser" (Sampson 37:204, Oakeshott 37: 244-245). For a few years, poultry grits were marketed in the Los Angeles area obtained from gray anorthosite (juarried in Soledad Canyon about 1^ miles east of Lang station. The rock was crushed at the quarry site to several sizes, sacked, and sold under the name of "gray granite grits." The small quarry and mill were operated intermittently as the product was marketed. This is the most recent attempt to utilize anorthosite in the San Gabriel Mountains. The quarry has been inactive since 1951. Karl V. Vail, a Los Angeles engineer, has been con- ducting an exhaustive series of tests for the past 6 vears* on the use of altered white anorthosite in the manufac- ture of a Portland pozzolan cement. The anorthosite used was obtained from the Vail claims on the south side of Soledad Canyon about half a mile southeast of Russ Siding. His experiments have resulted in the develop- ment of a material called "Dura Portland-Pozzolan cement" composed of Type II portland cement, as made by Southwest Portland Cement Company, 82.5 percent, altered anorthosite 14.9 percent, and calcium carbonate 2.9 percent. Mr. Irving Sherman, in the same communi- cation, reporting on tests made for Mr. Vail, indicates that the pozzolanic material (altered anorthosite and 16§ percent limestone) "can improve the durability of concrete subjected to freezing and thawing ..." show- ing "durabilities which are 200 to 400 percent greater" than other pozzolans. Mortar bars in which a mixture of altered anorthosite and calcite was substituted for high alkali cement gave the following results in one year : 15 percent substitution, expansion reduced 30 percent of expansion of control bar ; 25 percent, 57 percent reduc- tion; 40 percent, 72 percent reduction (Merriam, 1953). Because the anorthosite is a nearl.y monomineralic rock, composed of the single mineral plagioclase feldspar, it is non-reactive in itself, "not subject to thermal incom- patibility," and "can contribute no deleterious effects" to show up in later years. This material is not yet in commercial production but tests are encouragiiig. Anorthosite is one of the high-alumina rocks which received attention prior to and during World War II as a possible source of metallurgical-grade alumina for making metallic aluminum (Hagner, 1951). Because the rock is high in alumina, lime, and soda, the possibility was considered of producing soda and lime as by- products of an anorthosite-alumina plant. In 1947 the U. S. Bureau of Mines conducted extensive laboratory and pilot-plant tests on Laramie, Wyoming, anorthosite (Brown, R. A., et al., 1947) on the application of the lime-soda-sinter process. The conclusion was that ' ' Small- scale laboratory tests supplemented by pilot-plant runs have demonstrated that the alumina and soda occurring in the Wj'oming anorthosite from the Laramie Range can be extracted and recovered satisfactorily by the lime-soda process." Later a full-scale plant was con- structed at Laramie for this purpose. Early in 1954, news accounts told of the interest of a large cement company in purchase of the plant to produce alumina and use the residue for cement. Later in the year the government sold the plant to Ideal Cement Company of Denver for use in that company's aggregate operations. Average anal.yses of the Laramie anorthosite published by Fowler (1930) show 53 percent SiOa, 28 percent AI2O3, 11 percent CaO, 4 percent Na20, 0.8 percent K2O, • Written communication, October 15, 1954. 114 California Division op Mines [Bull. 172 0.3 percent MgrO and 1.5 percent iron oxides. The San Oabriel aiiorthosite is strikingly similar but production of alumina from anorthosite does not appear econom- ically feasible at present. Diatomite Thill beds of impure diatomite and diatoniaceous shale are characteristic of the upper part of the upper Mio- cene Modelo formation along the south side of the San Gabriel Mountains in the Little Tujunga area, Verdugo Mountains, Pacoima Hills, and Mission Hills; they are also found north of the San Gabriel fault just west of Sand Canyon. Some of the best quality diatomite is that exposed at the west end of the prominent anticline south of San Fernando Reservoir. None appears in sufficient quantity or of high enough grade to compete with com- mercial diatomite deposits elsewhere in Los Angeles County. The Katz diatomaceous shale deposit in Schwartz Canyon (see section on Shale) is carbonaceous silty sili- cious grayish-black Modelo shale, carrying diatoms, which weathers to a light yellowish-brown color. It is milled in Los Angeles and sold for insecticide carrier. Feldspar Potash feldspar has not been mined in San Fernando quadrangle but anorthosite has been mined for use, or possible use, as an abrasive in cleansers, for ceramic glaze, poultry grits, and for pozzolanic concrete (see .section on Anorthosite). Granite Granitic rocks of Lower Cretaceous (?) age crop out widely in San Fernando quadrangle but have been quar- ried in only two places on the south side of the San Gabriel Mountains. Pacoima Hills Quarry. A large quarry on the south side of the Pacoima Hills, less than half a mile northeast of San Fernando Road and the Southern Pacific rail- road, was operated from 1912 to 1927 by the Los Angeles County road department for decomposed granite for base material for county roads (Gay and Hoffman, 1954). During that period from 50,000 to 75,000 tons of rock were removed annually, an estimated total produc- tion of about one million tons, valued at approximately $850,000. A railroad spur ran directly to the quarry and cars were loaded by steam shovel. The material was then shipped to all parts of the county. The property is still owned by the county. The rock is exposed immediately south of the Pacoima Hills fault and is jointed, brecciated, and quite deeply weathered. The least-altered specimens are a fine-grained biotite granodiorite with oligoclase to microcline feld- spar in the proportion of roughly 2:1; many of the microcline phenocrysts are three or four times the aver- age diameter of feldspar grains in the rock. Much of the exposed rock is a darker, deeply weathered and altered gneissoid biotite-hornblende quartz diorite, which may be included older rock ; the chief feldspar is andesine. I'nuu) 84. View east across Hansen i'lim. ■*» t-.-si uliuuinul is in lim- niann<- ^amlsiiinr iiml shall- ni lin- niipii Miocene Modelo formation in the Pacoima Hills; east abutment is in Modelo shale at the west end of the Verdngo Hills. Spence Air Photos. San Fernando Quadrangle — Oakeshott 115 View north toward Hansen Dam across low ga. Wash. Photo by Mary Hill, November 1956. abandoned granite quarry, known as the "Mitch- quarry on the west side of Sierra Highway (U.S. b) in upper Mint Canyon was worked in 1920 to provide rock for paving this highway between Solamint and Oaks. The rock is jointed and fractured buff to pale pinkish gneissoid biotite-muscovite granite. The amount of rock removed is unknown. Hansen Dam Quarry. A large granite quarry was operated on the south side of upper Gold Creek in sec- tion 26, T. 3 N., R. 14 W. from 1938 to 1940, solely for the purpose of providing rock for facing, toe filling, and crib material for the Hansen Dam. The granitic rock quarried is unaltered biotite granodiorite and horn- blende-biotite quartz monzonite. The quarry is located on Government land but part of the dump is on private land. It was operated by Guy F. Atkinson Construction Company on contract for the U. S. Army, Corps of En- gineers. The rock was drilled, blasted, passed over griz- zlies to separate material less than 2 inches in diameter, and loaded by power shovels into trucks. Blocks of gran- ite were transported by truck approximately 6 miles down Little Tujunga Road to the dam site. Hansen dam is an earth-fill dam, 10,475 feet long, completed at a cost of $11,000,000 in 1940 across Tu- junga Wash (U. S. Army, Corps of Engineers, 1954). Drainage area behind the dam is 147 square miles, largely that part of the western San Gabriel Mountains drained by Big Tujunga River and Little Tujunga Creek. Height of the dam above the stream is 97 feet, reservoir area is 790 acres at the spillway crest, and capacity at spillway crest is 33,100 acre-feet. Major pur- pose of the dam is flood control during periods of heavy winter rainfall ; in the summer season run-off of the two principal streams drops to a minimum but is sufficient to maintain a lake of .several acres ; area at maximum water surface is 1,090 acres. The lake has been developed by Los Angeles City as an attractive recreational area, with facilities for swimming, boating, and picnicking. Geologic formations underlying the foundation of the dam are Recent and terrace deposits, which form the overburden, and beneath them, coarse arkosic sandstone, with fine-grained interbeds of sandstone and shale, of the upper Miocene Modelo formation. The Modelo for- mation dips 25° N. at the west abutment of the dam, and is folded into a gentle anticline and syncline within 2,000 feet of the east abutment. Material for the compacted earth fill of the dam was taken from the necessary excavation and from borrow pits upstream within the reservoir area. Aggregates for concrete were obtained from commercial sources in the San Fernando Valley. (U. S. Army, Corps of Engineers, 1947. See also section below on Sand and gravel for properties of these aggregates.) A total of about 330,- 000 cubic yards (770,000 tons) of granitic rock, with an estimated value of $962,500, was used on the dam, in the following amounts: Rock fill in the toe (trench on both sides of the dam running parallel to its length), 95,000 cubic yards; Rock paving — 29,000 squares (equal to 160,000 cubic yards), 10 feet on a side, in which there are 12 inches of one-man stone (75 pounds) on top of 6 inches of spalls (fines under 2 inches) ; thus the paving is 18 inches in total thickness on the uphill face of the dam ; Rock fill in the cut-off crib (the portion of the dam at its broadest part at the center where the spillway is located), 9,000 cubic yards; Rock fill below cut-off crib, 70,000 cubic yards. Limestone and Dolomite Limestone and dolomite are found in San Fernando quadrangle only in the area south of the San Gabriel fault and from Little Tujunga Canyon nearly to the western margin of the quadrangle. The crystalline lime- stone and dolomite are interbedded with quartzite, biotite schist, graphite schist, and other metasedimen- tary rocks of the Late Paleozoic ( ?) Placerita formation. Nothing but widely distributed small roof pendants and fragmented inclusions remain of the Placerita formation, which was intruded by Late Paleozoic ( ?) quartz diorite gnei.ss and Lower Cretaceous ( ? ) granitic rocks. The most prominent rock is white crystalline limestone and dolomite, medium to coarse grained, and in outcrops from a few inches to a few hundred yards in length. Chemical analyses of seven samples show magnesia (MgO) ranging from 0.4 percent to 20.3 percent, with an average of 11 percent, indicating that limestone, dolomite, and dolomitic limestone are all present (Oake- shott 1937, p. 221, and Logan 1947, pp. 49-50). Limerock Canyon Deposits. A belt of crystalline dolomitic limestone on both sides of steep-sided Lime- rock Canyon northwest of Little Tujunga Canyon in sections 28 and 21, T. 3 N., R. 14 W., has been worked intermittently for many years and has yielded an un- determined, but small, tonnage. The lenses of limestone strike northwest and dip very steeply ; they are a few to 200 feet in apparent thickness and up to 1,000 feet in length. The properties have been developed by open cuts. The Haskins dolomite deposit (pi. 2, locality 64) was first worked in the 1880s when lime was burned in three kilns on the property; about 5000 tons was produced in 1921-24 (Gay and Hoffman 1954, p. 672-673). The deposit was again being worked when visited in 1936 (Oakeshott 1937, p. 244) but has been idle since 1948. The Goodan deposit (not on pi. 2), close to the Haskins dolomite, produced a small tonnage for poultry grits, between 1945 and 1947. The Hilltop Lime deposit (pi. 2, locality 65) was developed by open cut in the 1940s but has been idle since. 116 California Division of Mines [Bull. 172 Pacoima Canyon Deposits. A number of small lenses of white crystalline dolomitic limestone are exposed in Pacoima Canyon and its tributaries. Some of these yielded lime in the 1800s. The Turner deposit in Pacoima Canyon about 3^ miles northeast of Foothill P>()ulevard was reported by Good- year (1888, p. 340-341) as active prior to 1872. The San Fernando deposit (pi. 2, locality 66) in Limekiln Canyon is another deposit worked for an unknown period in tlie 1800s ; evidence of ancient lime kilns may still be seen. The Wragg Ranch (pi. 2, locality 68) and White Crystal (pi. 2, locality 67) deposits were operated by Leo Gordon for chicken grit in 1940-43. The Wragg; Ranch property yielded about 300 or 400 tons and White Cry.stal 1,000 tons (Gay and Hoffman 1954, p. 674-675). The Baughman dolomite deposit (pi. 2, locality 63) is a lens of crystalline dolomitic limestone about 800 feet long and 100 feet wide on a tributary to Pacoima Can- yon, sections 7 and 18, T. 3 N., R. 14 W. Strike of the lens is west-northwest and dip is steeply north. There is no record of production. Roofing Granules * Ilmenitc-Magncttte. Ilmenite-magnetite has been re- covered from Recent alluvium in San Fernando quad- rangle at two localities for use as granules in rooting paper. Challoner Thompson produced a small tonnage of magnetite-ilmenite concentrates between 1944 and 19o2 from the Live Oak placer mine in Sand Canyon (pi. 2, locality 41). Asphalt Products Company operated a pilot plant to recover a similar heavy concentrate in 1947 in alluvium at the mouth of Pole Canyon, near Lang sta- tion. There has been no production from either deposit in the past few years. Sierra Pelona Rock Company.** Sierra Pelona Rock Company, Inc., Route 1, Box 33-D, Saugus, set up its plant 1,500 feet north and 1,100 feet west of the south- east corner of section 28, T. 5 N.. R. 14 W., S.B.. and has been producing roofing granules of naturally colored rocks since July 1, 1954. The "Pastel Green pit" is 1,000 feet north of the plant. * See also sections on Titanium and Vnlrtinic asli. •• Data received too late to be included on economic map and taliu- lated list. Reported in written communication by T. E. Gay Jr., April 1955. Photo 86. View iKirtlnvist toward plant of Sierra I'elona Rock Company. Photo hy T. E. Gay, Jr., April 1955. I'HOTO 87. View north toward plant of Sierra IVloua Uook Company, producers of colored roofing granules from shales of the Oligocene (?) Vasquez formation in upper Tick Canyon area. Photo bu T. E. Gay. Jr.. April 1955. The plant, which has a capacity of about 400 tons per 6-day week, active one shift, is operated by about five men ; three additional quarr.v men and two truck drivers are also employed. The mill is a Pioneer portable model, run by diesel engine and auxiliary gasoline engines. From the quarries rock is trucked to the plant and dumped in a bin through a grizzly with about 8-inch spaces between rails. A reciprocating feeder places the bin rock on a conveyor belt which goes to the primary crusher, a 36-inch by 24-inch jaw crusher set to crush to about 2 inches. A bucket elevator carries the crushed rock to a single-deck 12-foot Symons vibrating screen, with |-inch and f-inch screens placed end to end. Ma- terial finer than J-inch is discarded as fines; material between |- and |-inch is belt-conveyed to a storage bin where it is again screened on a ^-inch screen to remove more fines before being sacked for sale as the standard size roof granule. Material larger than f-ineh is crushed in the secondary crusher (rolls, 18 inches wide) and rescreened, except for a small percentage which is sacked and sold as large-size granules. Four main colors of granule are produced ; one from a pit at the mill, the others within about a 20-mile radius. To avoid mixing colors, about 2 hours are re- quired to clean the entire plant between runs of different colors; 150 to 200 tons are milled before colors are changed. Granules are sold in paper 100-pound sacks for $13.00 per ton, f.o.b., plant, mostly to dealers in roofing material. Most of the output is marketed in the IjOS Angeles area; some goes as far as Bakersfield. This operation has a transportation advantage over other pro- ducers of natural colored granules, as it is about 45 miles closer to the Los Angeles market area than the nearest similar operation, at Rosamond. Pastel Green granules are made from pale green- colored silicified siltstone locality present in the Oligo- cene (?) Vasquez formation, obtained about a quarter of a mile northeast of the mill. Beds strike about N. 80° E., and dip 85° S. to vertical. Soil and iron oxide stains have discolored much of the rock, especially where it is 1958] San Fernando Quadrangle — Oakeshott 117 abimdantly fractured near the surface. lu April 1955 two sidi'liill quarries about 150 feet apart had beeu opened ; each was about 25 feet h)nfr, 2 feet wide, and 20 feet in maximum heijrlit at the face. Roek is drilled, blasted, and loaded by skiploatler on trucks for the haul to the mill. Kelly Green {rranules are nuule from massive fzreen tuflfaeeous volcanic sediments obtained at the east end of the Sierra Pelona, about 2 miles northeast of Vincent. Truck haul is about 21 miles to the mill. Burgundy fjranules are made from hard, clialcedonic, massive volcanic sediments (Vas(|uez formation?) of violet color obtained about 2 miles northeast of Acton. The pit is about 14 miles by road from the mill. Gold g:ranules are made from iron-stained granitic rock obtained on the south side of Highway 6, about three-quarters of a mile southwest of the Oaks. This rock is hauled about 9 miles to the mill. Sand and Gravel Material for the sand and gravel industry is the second most valuable group of mineral commodities currently being produced within the limits of San Fernando quadrangle. Petroleum production is now valued at apju-oximately 5| million dollars per year, while sand and gravel production is valued at over $300,000 per year. In some recent years, the total value of rock products has probably considerably exceeded the latter figure, at times when rock was being quarried for special structures. Gay and Hoffman (1954, pp. 553- 561) have given a useful summary of sand, gravel, and crushed rock, including geology, mining operations and processing, specifications, reserves, and citj' and county zoning regulations. Their remarks apply well to the industry in San Fernando Valley, as that valley is the site of some of the major operations in the county. Geology. The greatest sand and gravel resources in the quadrangle are the late Quaternary alluvial deposits of Big Tujunga River and Pacoima Creek, on the south side of the western San Gabriel Mountains, and of the Santa Clara River, in the northwestern part of the mountains. Streams of the area are subject to extreme seasonal variation in runoff, and sand, gravel, and boulders are deposited as flood volume of water drops, as well as in the lower parts of the mountains where stream gradients flatten. Renewed elevation of the mountains in late Quaternary time has resulted in ex- tremely thick coarse alluvial deposits in San Fernando Valley. Boulders, which handicap operations, become less numerous away from the source and coarseness of gravel tends to decrease. Gay and Hoffman (1954, p. 553) note that in Big Tujunga Wash sand predomi- nates in the uppermost 40 to 60 feet of mo.st pits but gravel and boulders are most abundant below those depths. About one percent of the material passes a 200- mesh screen. The most common rock types present are granitic rocks, such as granodiorite, quartz monzonite, granite, varieties of quartz diorite, gabbro, hornblende and biotite quartz diorite gneisses, and minor anorthosite, all exposed widely in the highest source areas of this part of the San Gabriel Mountains. The darker gneisses, both because of their foliation and content of ferro- magnesian minerals, such as hornblende and biotite, disintegrate and decompose more readily than the light- colored granitic types. The upper Miocene Modelo silicious shale is the chief source of deleterious reactive material in the deposits. Distribution of this formation along the north side of San Fernando Valley means that some reactive pebbles are present in aggregates of Tujunga and San Fernando Valleys which are not present in aggregates of the Santa Clara River valley above Solamint. The U. S. Army Corps of Engineers (1947) made a petrographic examination of concrete popouts from Sepulveda Dam, Hansen Dam (near southern margin of San Fernando quadrangle) and the channel wall of the Los Angeles River. These three structures were built with aggregates from four sources in San Fernando Valley. The materials were derived from erosion of rock formations cropping out in the western San Gabriel and Verdugo Mountains as shown on plate 1. Results of the examination show that materials of the four companies were similar in the proportions of the various constituents. The reactive material was found to be silicious shale, composed largely of amorphous silica, and containing fossil diatoms and foraminifera. The only large source of this type of rock is the siliceous and diatomaceous shale of the upper Miocene Modelo forma- tion which crops out along the front of the western San Gabriel Mountains from Sunland to San Fernando Reservoir and in the nearby Verdugo Mountains. The Corps of Engineers found that siliceous shale was pres- ent "in about the order of 3 to 6 pieces — | to 1 inch in diameter — per 50 pounds of material passing the 2- inch sieve and retained on the f-inch sieve," and in the fine aggregate "it was estimated that probably not more than 1 to 6 recognizable particles of silicious shale were present in 5000 sand grains. ' ' They noted that : " It is known that relatively little of this type of material is necessary to cause distress in concrete and the amount found in the coarse aggregate is probably sufficient to account for the popouts. However, the amount in the fine aggregate does not appear to be sufficient to account for all of the pattern cracking observed." ^:-"^tl^.W'^..,,/;^_ Photo 88. MacArthiir ready-mix plant, which uses Santa Clara River gravels in Soledad Canyon. Photo by Mart/ Hill, Noveitiher 1956. 118 California Division of Mines [Bull. 172 I'liOTO 80. Gravel deposits in Tujunga Wash at City Rock Company gravel plant. Operations. Four large gravel pits, now abandoned, have operated in Pacoima Wash. Three of them, in southeastern San Fernando (pi. 2, localities 77, 78, 79), discontinued operations in the 1920s. The Pacoima Dam gravel pit (pi. 2, locality 76) in Pacoima Wash about half a mile below Pacoima Dam produced about 400,000 tons of aggregate, valued at approximately $240,000, between 1925 and 1929, which was used in concrete for construction of the dam. The MacArthur and Son pit (pi. 2, locality 75) in Soledad Canyon half a mile west of Lang station has produced about 10,000 tons per year since 1948 and has a current capacity of about 50 tons per hour. Five men were employed in 1952 in producing various grades of sand, gravel, ready-mix, and plaster sand (Gay and Hoif- man 1954, p. 540-541 ) . A pit about 30 feet deep covering several acres, has been developed in the bed of the Santa Clara River. The pebbles are chiefly granitic rocks, gabbro, anorthosite, basic volcanic rocks, and metamorphic types, derived from the crystalline com- plex of the high San Gabriel Mountains, and from the Tertiary nonmarine Mint Canyon and Vasquez formations. The largest rock products operation in San Fernando (juadrangle is the gravel pit of City Rock Company in the deposits of the Big Tujunga River in Tujunga Val- ley, about 2 miles west of Sunland. This was first opened in 1925 and operated intermittently until 1943 ; since then it has had a steady production of about 500,000 tons, valued at approximately $300,000 per year. About 70 men were employed in 1952 producing as much as 250 tons per hour of standard sizes of sand, gravel, and crushed rock. Rock types are those characteristic of the San Fernando deposits as discussed in the section on (ieoloyy above. '*..- ^,^^*- lilwM* I'HOTO 90. View north from Foothill Boulevard at Tujunga Wash, across gravel plant of City Rock Company. Photo by T. E. Oay, Jr. Photo 91. C'it.y Uock ('niiiii:iM.v t;i;ivel iilaiit in Tujunga Wii.sh. Photo hy Mary Hill, Xovember lO.^li. Shale About 1,000 tons of shale per year has been produced from an open pit on the '" ' '^" '-* "^fhwartz Canyon, since 1950. Dr. Leon Ki the material for use as rock is silty carbonaceous diatoms and numerous sn cretionary limonitic limes grayish black but weather yellowish brown. The thin irregularly crumpled, bu 40° W., the dip 30° N. 1 the exposed section of formation. Volcanic Ash (Tuff) Volcanic tuff beds in tl formation have been qu^ northwestern part of the and for use in roofing. Tuff (volcanic ash) horizons in the upper ht Canyon formation. The b white friable vitric tuff, mane up anuost euLireiy oi glass, to fine- to coarse-grained crystal and lithic tuffs and tuffaceous sandstone. Some tuff beds have been opalized and some have undergone partial alteration to clay minerals. The beds are discontinuous, and occur at various horizons through at least 2,000 feet, strati- graphically, of the upper part of the Mint Canyon for- mation. Many lens out within a mile. Wallace (1940) has mapped and described the tuff beds in detail. Blue Cloud Chinchilla Dust. Gay and Hoffman (1954, p. 552) have described the unique rock products industry in which tuff from a deposit in Bouquet Canyon 19581 San Fernando Quadrangle — Oakeshott 119 (pi. 2, locality 81) has been mined since 1950 for use in bathing: chinchillas. The Blue Cloud deposit is in a bed of slightly altered, somewhat friable vitric tuff that has a blue-grray color favorable to its use. The stratum is about 6 feet thick and can be traced in a northwesterly direction for nearly a mile from Bouquet Canyon. Strike of the bed is "between N. 60° W. and N. 80°" E. ; dip ranges from 22° to 35° S. The bed being mined is one of a pair of such strata on the south limb of an anticline, with brown and gray sandstone above and below, and is the equivalent of the upper vitric tuff of Jahns' member 23 (Jahns 1940, p. 156 and map, fig. 4), high in the upper Miocene Mint Canyon formation, and the equivalent of Wallace's L and M tuff beds (Wallace 1940, p. 35-36). The tuff is mined by open-pit methods ; the quarry face was 25 feet high and 40 feet long in 1952. The material is sufficiently indurated so that blasting is necessary. It is removed with hand tools, carefully sorted, and carried by wheelbarrow to the mill where it is ground to 20 to 200 mesh and kiln dried and sterilized at 600° F. Early in 1953 the rate of production was about 50 tons per month. The market is not large, as a pen of one to four chinchillas requires less than 25 pounds of dust a year. The sacked dust is distributed in tlie United States and to foreign markets. A number of L-hinchilla farms are located in San Fernando Valley; at least two are on Foothill Boulevard near the southern margin of San Fernando quadrangle. Reynier Ranch. Several thousand tons of tuff was mined from the Reynier Ranch beds (pi. 2, locality 82) from open pits, between 1937 and 1940. The material was sold to the Pioneer Division of the Flintkote Com- pany. It was calcined at 1800° to 1900° F., ground and classified, and u.sed as a surfacing on asphalt shingles and roofing. A stratum of well-indurated, slightly kaolinized partlv porcelaneous fine-grained white crystal tuff several feet thick (Wallace 1940, p. 38-39, "tuff bed I") may be followed for about a mile S. 25° W. from the west side of Sand Canyon to Reynier Can- yon; dip is 30° to 40° NW. There is evidence of mining for several hundred feet along the strike of the bed. Petroleum Placerita Oil Field * The Placerita oil field extends over section 31, T. 4 N., R. 15 W., and the borders of adjoining sections on the north, west, and south at the western end of the San Gabriel Mountains about 2 miles east of Newhall ; a small part of the field extends west of the western boundary of San Fernando quadrangle. It is 1 mile north of the Whitney Canyon area, abandoned in 1937, 1| miles north of Elsmere area, which has produced a very small amount of low-gravity oil in the past few years, and 2| miles due west of the Placerita schist area, which produced a little high-gravity oil from basement rocks several years ago. Placerita oil field is divided into the Juanita area on the north and the Kraft-York area on the south by the northwest-trending Orwig fault. The Juanita area produced 1,887,000 barrels of 21.0° gravity oil in 1952 while the Kraft-York area •Barton and Sampson (49), Kew (24b. 43), Oakeshott (50, 54a). Waning (34), WiUis (52). produced 1,571,000 barrels 12.7° gravity oil. In 1953 Placerita produced 2,757,651 barrels of oil valued at $5,598,031**. Cumulative production to December 31, 1953 has been 21.291,780 barrels with an estimated value of $42,748,600»*. In June 1953 there were 383 actual and potential producing wells t with production from 660 proved acres ; 95 percent of these wells were within San Fernando quadrangle. The Kraft-York area was discovered in 1920 b.v the Equity Oil Compan.v which completed Daisy 1 (now Guiberson Oil Company York 1) for a few barrels of 14° gravity oil at a depth of 975 feet. Four wells were drilled between 1920 and 1933, producing from 6 to 19 barrels per day. In April 1948, Nelson-Phillips Oil Com- pany rediscovered the area when it brought in Kraft 1 in Placerita Canyon flowing 70 to 100 barrels per day of 15.6° oil from the interval 580-717 feet. In January 1949, Ramon Somavia brought in Juanita 1 flowing 340 barrels per day of 22.4° gravitj^ oil, about a mile north of Nelson-Phillips' Kraft 1, to discover the Juanita high-gravity area. Bottom of the producing zone was at 1830 feet. There followed a period of unrestricted production as the State Spacing Act was declared un- constitutional by the California Superior Court. A town-lot drilling campaign in the Juanita area sent production skyrocketing to over 860,000 barrels per month in September 1949. Production in the area fell very rapidly to a July 1951 figure of slightly over 200,000 barrels; there has since been a gradual (iecline. Placerita is the most easterly of the Ventura basin oil fields. Rock formations consist of a series of Tertiary- Quaternary marine and continental sediments dipping northwestward off the much older crj'stalline rock com- plex of the San Gabriel Mountains exposed only a mile southeast of producing wells. In the area of the oil field the only formations exposed are the continental sand and gravel of the Saugus formation, overlain unconformably and largely obscured b.v gently folded gravels of the late Quaternary Pacoima formation. Most of the wells in the field have penetrated Sunshine Ranch, Upper Pico, and Lower Pico members of the Pico formation, and the Repetto formation. The upper Miocene Modelo formation has been encountered in wells in the western part of the field, and a few wells have bottomed in Eocene formations. Unconformities separate most formations. Interfingering and gradation of marine and continental beds is common. Structure of the area is dominated bj- the San Gabriel fault zone, a major series of steep north-dipping (70°- 80°) shear planes trending N. 65° W. and .showing right lateral strike-slip movement. This fault separates two quite different geologic provinces and abruptly terminates the northward extension of the Placerita oil field. Eastward extension of the field is as sharply bounded by the north-trending Whitney fault. Well data .suggest that the Whitney fault dips about 70° W. north of Whitney Canyon. A number of minor faults in the oil field have been discovered through well records but cannot be recognized on the surface. One of these, the Orwig normal fault, trends northwest •* Computed by H. H. Symons, Division of Mines, from figures sup- plied by the State Division of Oil and Gas. t PI. 5, Map of Placerita oil fields, Los Angeles County, California. ]20 California Division op Mines fBiill. 172 across the center of the field and separates the Jiianita area of hiph-gravity oil from the Kraft-York area of low-gravity oil. Another, similar in trend and character to the Orwig fault and a quarter-mile southwest of it, forms a local gravity barrier between two different low- gravity oils of the Kraft-York area. The area as a whole is quite complexly folded and faulted but structural contours (Barton and Sampson 49; Willis 52) on top of the Lower Kraft zone in the oil field show that the Pliocene beds dip essentially honioelinally 15°-20° WNW. In the southern part of the Kraft-York area the dip is due west, while in the northern part of the Jua- nita area the dip is northwest. Surface attitudes in the Saugus and Pacoima gravels which cover the oil field are difificult to evaluate as these formations obscure the subsurface structure. Faulting has been of prime importance in the accumu- lation of oil in the Placerita field. The San Gabriel and Whitney fault zones form the north and east limits of accumulation of oil in the northwest-dipping Pliocene beds of the field. Faults of small displacement and no surface expression have separated the field into pools of three different gravities. Folding and faulting trending roughly N. 70° E. in the southern part of the field are probably responsible for the southern boundary ; bottom- water determines the western limits of the field. Up-dip lensing in the members of the Pico formation and uncon- formities at the base of the Saugus and Pico formations have probably also influenced accumulation. Wells drilled into Eocene and Paleocene formations in the field have been dry. The two producing zones in the Placerita field have been designated the Upper Kraft and the Lower Kraft. The Upper Kraft zone, in the middle to upper Pliocene Pico formation, ranges from 170 to 250 feet in thickness and produces 11° to 17° gravity oil from the Kraft- York area only. The zone is terminated at the west edge of the field b.v a bottom-water interface. Initial production was 25 to 175 barrels per day. The Lower Kraft zone, in the lower Pliocene Repetto formation, ranges from 300 to 450 feet in thickness and produces 20° to 25° gravity oil northeast of the Orwig fault in the Juanita area, and 12° to 16° oil in the Kraft-York area. Initial production of wells in the Lower Kraft zone in the Juanita area was as high as 3,000 barrels per day, but declined rapidly. Whitney Canyon Area * The Whitney Canyon area extends over small fractions of sections 6 and 7, T. 3 N., R. 15 W., one mile south of Placerita oil field at the western end of the San Gabriel Mountains. Production has been included with the New- hall oil field and no figures on cumulative production for the Whitney Canyon area are available. However, the area produced a "few thousand barrels" t of 14° to 27° gravit.v oil from 1893 to its abandonment in 1937. In ,Iuly 1935, four wells produced a daily average per well of 3.9 barrels of average 20° oil, cutting 40 percent water, and one well produced 3.7 barrels per day of 27° oil and 2.5 barrels of water (Walling, 34). Whitney Canyon area wells are shown on pi. 5, Map of Placerita Oil Field. Whitney Canyon area was discovered in 1893 by Banner Oil Company well number 1, since 1920 known as Republic Petroleum Company Banner 3. The well produced about 100 barrels per day for a short time, but was abandoned when water broke in. In 1921, Republi- can Petroleum Company, Ltd., redrilled and deepened the well to 1,185 feet but failed to find the oil sands which had previously produced. The well was completed for a few barrels per month of 33° gravity oil. Republic Petroleum Company Banner 1, drilled in 1917-18, was producing a few barrels per day of 15° gravity oil in 1935; Price 3 was also producing. Price 4, first drilled in 1930, was cleaned out and placed on production in 1933 by Republic for two barrels per day of 26° gravity oil and five barrels of water from Eocene sandstone. Live oil seeps in Sunshine Ranch beds in Whitney Canyon and in Lower Pico sandstone and conglomerate on the slopes south of the canyon attracted early drilling. In the past few j'ears three wells have been drilled in the Whitney area, all unproductive. The most interesting, geologicall}', was Continental Oil Company Phillips 1, drilled to a depth of 8,253 feet in 1952.* This well topped the Kraft sands (productive at Placerita) at 435 feet and reached basement gneiss at 7,120 feet, after passing through 150 feet of fault gouge. Formations exposed in the Whitney Canyon area proper include the Saugus formation and the Sunshine Ranch and Lower Pico members of the Pico formation, all dipping in a northwesterly direction at angles be- tween 15° and 25°. The light-colored, poorly consolidated conglomerate and sandstone of the Saugus formation overlap the Sunshine Ranch brown sandstone, greenish mudstone and conglomerate toward the northeast and lie directly on massive very fine-grained Lower Pico sandstone. Marine Upper Pico seems to be absent, the upper Pliocene being here represented entirel}' by the continental brackish-water Sunshine Raueh. The Lower Pico member west of the Whitney fault consists of fine to coarse sandstone, with abundant carbon fragments and spots of sulfur, and lenses of pebble conglomerate ; much of the sandstone has been saturated with oil, but outcrops are dry. East of the Whitney fault the massive very fine-grained Lower Pico sandstone is diy-oil sat- urated in many places. The Lower Pico is characterized by the middle Pliocene "San Diego" fauna described by Grant and Gale (31). Major structural feature of the Whitney Canyon area is the Whitney fault (known also as "Swall-Ferrier" fault) which has been traced slightly east of north from upper Elsmere Canyon to the San Gabriel fault. As at Placerita, this fault is the eastern limit of oil produc- tion. East of the Whitney fault, from Placerita to Els- mere, sandstones and conglomerates of the basal Sun- shine Ranch (?), Upper Pico and Lower Pico members of the Pico formation, and the Elsmere member of the Repetto formation, are oil saturated in many places but all are dry in outcrop, except for heavy oil seeps in a number of places. Surface dips of 15° to 25° NW. in the Pliocene sediments continued at depth in the Con- tinental well. Dipmeter results showed average dips in the Eocene were 15° to 25° with the dip component oriented S. 30° to 70° W. At the uneonformitv at the • Kew (24b. 43), Walling (34). t Graham B. Moody, oral communication. • Geological information on this well from Continental Oil Company written communication, April 1952). i!ir)Si San Fernando Quadrangle — Oakesiiott 121 base of the Pliocene, dips changed from 10° or 15° in the Pliocene to 20° or 25° in the Eocene Domen<;ine formation. This unconformity is well exposed in Elsmere Canyon 1.4 miles south of the Continental well. There were evidently three producing zones in the Whitney Canyon area : two Pliocene zones, probably near-equivalents of the Upper Kraft and Lower Kraft at Placerita, and one in the Eocene (probably Domengine) sandstone. The heavier oil (gravity as low as 14°) came from basal Snnshine Ranch (?) and marine Pico forma- tions and from the Repetto formation (Elsmere mem- ber?), the higher gravity (as high as 40°) from the Eocene. Wide differences in gravity of oil between wells suggests that minor barrier faults, not recognized at the surface, are present in the Whitney area as well as at Placerita. Elsmere Area * The Elsmere area extends over about 60 acres of the western part of section 7, T. 3 N., R. 15 W. A few wells in the field are just west of the western boundary of San Fernando quadrangle. It is about half a mile south of the Whitney Canyon area and IJ miles south of Place- rita oil field. According to Graham B. Moody t the Elsmere area produced an estimated 285,000 barrels of oil from 1891 to 1929. Nine wells were producing a quarter of a barrel to four barrels per day of 14° to 16° gravity oil in 1929 when the field was shut in. Elsmere area wells are shown on plate 5, Map of Placerita Oil Field, Los Avgeles County. Pacific Coast Oil Company drilled 20 wells on its property before the area was acquired by Standard Oil Company (of California) in 1902. Elsmere 1, the first well drilled, had green-oil showings at 1,020 feet but was abandoned in 1890 after reaching a depth of 1,376 feet. Elsmere 2, the first productive well, was completed in 1891 and produced 229 barrels of oil in the first four days; in 1894 it produced six barrels per day. Although drilled to 1,226 feet, this well probably produced from a depth of less than 485 feet. In 1950 the well produced a quarter of a barrel of oil and three-fifths of a barrel of water per day; this was the last production from the Elsmere area. After Standard Oil Company of Califor- nia shut in its Elsmere wells in 1929, E. A. Clampitt continued a few wells in production in the area just west of the west line of section 7; in 1942 this operator had six wells yielding about two barrels per day of 14° to 16° oil each, with 75 percent water. All wells in the Elsmere area were spudded in the middle Pliocene Lower Pico member of the Pico forma- tion. This member includes white pebble conglomerate, coarse sandstone with fine sandstone lenses, and thin brown siltstone beds, very much cross-bedded and irregu- larly impregnated with petroleum. Live tar seeps occur west of the Whitney fault and in Elsmere Canyon. Southeast of the wells, in upper Elsmere Canyon, the lower Pliocene Elsmere member of the Repetto forma- tion, consisting of coarse marine sandstone, conglomer- ate, siltstone, and mudstone, commonly oil-saturated, is exposed conformably ( ? ) underlying the Lower Pico and lying with a well-exposed angular unconformity on mid- dle Eocene hard greenish-gray pebbly Domengine sand- stone. The Pliocene beds dip generally 15° to 25° NW., and the Domengine sandstone strikes northwest and dips 35° SW. Eocene rocks do not crop out cast of the Whit- ney fault. A fault, apparently of small displacement, trends northwest along Elsmere Canyon and has off^set the Elsmere-Domengine contact. Although not promi- nent in outcrop, this fault apparently forms the north- eastern limit of production in the Elsmere area. Records of the Elsmere wells are very poor and inter- pretation of the fragmentary drillers' logs is difficult, but there is little doubt that low-gravity production came from Lower Pico and Elsmere members of the Pliocene, and that the small amounts of lighter green oil came from the Eocene beds. Schist Area * The Schist area in upper Placerita Canyon, about 2\ miles east of Placerita oil field, includes 12 wells in sec- tions 3 and 4, T. 3 N., R. 15 W. Most of the wells were drilled from 1899 to 1901 to shallow depths, and for a time produced about a barrel per day of 26° to 38° gravity white oil; some of the oil tested as high as 50°. The last well, drilled in 1949 to a depth of 2,325 feet, was abandoned. One well, never plugged, still yields a little gas and light greenish oil. The wells are bunched closely in the San Gabriel fault zone, particularly along the Placerita fault in that zone, and were drilled entirely in the complex of Placerita metasedimentary rocks, dio- rite gneiss, and granodiorite which has intricately in- truded the first two units. Wells in the Schist area are within the area shown on plate 2, but individual well locations are not shown. Brown and Kew (32) mapped the area in detail and discussed the occurrence. They suggested that the oil migrated from Eocene strata, underlying the Saugus formation in the San Gabriel fault zone, along faults to its present position in fractured crystalline rocks; and that filtration during this migration accounts for the high-gravity oil. Exposures of middle Eocene rocks in Elsmere Canyon, Eocene and Paleocene formations en- countered in wells in the Placerita-Whitney Canyon areas, and Paleocene exposed in slivers along the San Gabriel fault to the southeast show that Eocene and Paleocene formations which may have been source rocks are present. However, marine upper Miocene organic shales of the Modelo formation, a few miles to the north- west, or lower Pliocene formations of the Placerita- Whitney Canyon-Elsmere areas may have been the source rocks. Exploratory Holes on the Northern Margin of San Fernando Valley ** Thirty -six exploratory wells (pi. 2) have been drilled along the northern margin of San Fernando Valley in the San Fernando quadrangle; 18 of these were drilled between 1940 and 1953. Two of the modern wells en- countered a little oil and two of the old wells are re- ported to have produced a small amount of heavy oil. Two of the 36 wells were drilled to basement granitic •Kew, (24b, 43), Brown and Kew (32). \Valline (34). t Oral communication, 1954. • Brown and Kew (32), Kew (24b), Waning (34). ••Hill, M. L. (30); Howell (49); Kew (24b); Oakeshott (51a. 51c, 52). 122 California Division of Mines [Bull. 172 rocks (pi. 2, No. 117, Russian Oil Co. No. 1, and No. 141, Intex Oil Co. Cleeves 2). The marginal foothill belt on the north side of San Fernando Valley extends from west to east across San Fernando quadrangle from the San Fernando Reservoir to Tujunga, and northward from the Verdugo Moun- tains-Pacoima Hills to the ])re-Tertiary crystalline rocks of the San Gabriel Mountains, an area of more than 50 square miles of Tertiary-Quatenary sedimentary forma- tions, partly marine, with abundant tar seeps and lower Pliocene bituminous sandstone in the northwestern part. This sedimentary section is essentially an eastward ex- tension of the late-Tertiary Ventura basin and is mar- ginal to the Los Angeles basin. Geology and petroleum possibilities of the area were summarized by Oakeshott (52) and two unexplored areas were mentioned as offer- ing posibilities for structural and stratigraphic traps in this region where source rocks, po.s.sible reservoir rocks, bituminous outcrops, and oil seeps are known. First, along the North limb of the Little Tujunga syn- cline under the Lopez and Hospital thrust faults, both Repetto and Model o formations may be cut oif by the faults at depth, may pinch out, or be overlapped before reaching the faults — in any case, a condition favorable to petroleum accumulation. Bell Petroleum Company Bartholomaus Canyon Bush Bar 1 (pi. 2, No. 134), drilled to 2,988 feet, produced a few barrels of 11° grav- ity oil per day. This is the most easterly known occur- rence of oil in the foothill belt. The well was drilled on the south limb of the Little Tujunga syncline but proved the presence of two oil sands in the upper Miocene (prob- ably Mohnian stage) Modelo formation. If a well were drilled due north of this, on the north limb of the syn- cline, it might be in a more favorable position. Intex Oil Company drilled two wells (pi. 2, locality 140, Cleeves 1, and locality 141, Cleeves 2) on the north limb of the syncline east of Little Tujunga Canyon and east of the Lopez fault. The more northerly, Cleeves 2, penetrated continental terrace and Saugus gravels to granitic rock at a depth of 1,505 feet. Cleeves 1 drilled through con- tinental Saugus and Sunshine Ranch ( ?) beds into upper Mohnian Modelo shale and sandstone and bot- tomed in Modelo arkose at 4,250 feet. Both holes were dry. The second favorable area is the possible westward extension of the Verdugo Mountains-Pacoima Hills structural high. This major structure has a general east- west trend and a westward plunge. In the west end of the Verdugo Mountains at Green Verdugo Reservoir, middle Miocene (?) Topanga (?) red beds and basalt are exposed lying disconformably below Modelo con- glomerate and unconformably on granodiorite. Four miles west, in the Pacoima Hills, similar rocks of the Topanga (?) formation are faulted against granodiorite on the south and lie below Modelo shale which contains lower Mohnian foraminifcra. Standard Oil Company of California Woo 1 (pi. 2, locality 123), about 4 miles west of Pacoima Hills, encountered altered basalt at a depth of 8,694 feet and bottomed in the Topanga forma- tion at 9,739. Top of the basalt in the Pacoima Hills is at elevation 1,100 feet and at elevation — 7,799 in the Woo well (Shelton, 54). Assuming no structural or strat- igraphic complications, this would give a westward plunge of about 20°. This part of San Fernando Valley, just west of the Pacoima Hills, has not been thoroughly tested. Prior to drilling the non-productive Woo well, Standard Oil Company drilled University 1 (pi. 2, locality 124) in 1927, a dry hole which bottomed in cherty shale (Modelo ?) at 5,938 feet. Intex Oil Company "drilled Toon 1, in 1953, on the margin of the valley about a mile north of Pacoima Hills. The well was continuously in north-dipping Modelo formation of Mohnian to Luisian ( ?) age and bottomed at 4,553 feet in steep- dipping beds after passing into a possible fault zone below 3,200 feet. Three deep wells were drilled in the extreme north- western part of San Fernando Valley in an area of very complex structure and stratigraphy in the Santa Susana fault zone. Barnsdall Oil Company (now Sunray Oil Company) T.I. & T. 1, was drilled to a depth of 8,035 feet through a section of Saugus, Sunshine Ranch, Pico, and Repetto formations more or less consistent with sur- face geology in the San Fernando Reservoir area. Rich- field Oil Corporation T.I. & T. 1, drilled practically on the Santa Susana fault, is believed to have encountered only continental sediments to a depth of 8,207 feet. Sun- ray Oil Company Stetson-Sombrero 1 was drilled to a depth of 12,027 feet, probably in the syncline whose axis appears at Upper San Fernando Reservoir, and en- countered only nonmarine sediments, according to the incomplete information available. Exploratory Holes North of the San Gabriel Fault* Twenty-four exploratory wells have been drilled north of the San Gabriel fault in San Fernando quadrangle; 17 of these were drilled from 1948 to 1952. None en- countered showings of oil and all were drilled wholly in continental formations, with the exception of Conti- nental Oil Company Wallace USL 1 which probably penetrated a small thickness of marine lower Pliocene (Repetto formation) before drilling through continental Mint Canyon beds to bottom at a depth of 6,151 feet. At least two of these wells reached crystalline basement rocks (pi. 2, locality 83, Carl R. Pohl and Associates Pohl-Green 1, and pi. 2, locality 104, Turner and Trick- ett No. 1). The thick Tertiary sedimentary section north of the San Gabriel fault in San Fernando quadrangle com- prises the continental beds of the Soledad basin (eastern Ventura basin), including Vasquez, Tick Canyon, Mint Canyon, Sunshine Ranch, Saugus, and Terrace forma- tions, plus a few scattered thin remnants of marine beds of the upper Miocene Modelo formation and lower Plio- cene Repetto formation exposed in the western part of the basin. No oil seeps or bituminous sediments are known in these formations north of San Gabriel fault. Drilling has proven that northern extension of the Plac- erita oil field is sharply limited by the San Gabriel fault. Because source beds for petroleum are lacking, it ap- pears unlikely that any petroleum will be obtained north of San Gabriel fault in San Fernando quadrangle. The rather thorough testing of the area by 24 recently drilled exploratory holes tends to confirm this conclusion. • Numbers 83-104 on List of wells drilled outside of Placerita oil field in San Fernando quadrangle to April 1, 195S, accompany- ing this report, and on pi. 2. Econonric map. Numbers (144) and (146) are on the above list but are not shown on pi. 2. 19581 San Fernando Quadrangle — Oakesiiott 123 BIBLIOGRAPHY Agnew, HiuUlon W.. 1948, The Kt'dldRV of a i)iirt of the Riivcnnn quadriinKle, ("nlifornia : California Inst. Tpohnolocy M.S. thesis ( unpiih. ) . Alf, K. M., 1943, M.vlonites in the ea.stern San Gabriel Moun- tains: ("alifornia Div. Mines Rept. 3!t, pp. 14ri-l."il. Ailing. H. li., 1936, Interpretative petrology of the igneous rocks, Mv(;raw-Hill, 3.").3 pp. Anderson, F. M., 19()5, A stratiKrai>hir study in the Mount Diahio Range of California : California Acad. Sci. I'roc. .3, (ieol. 2, pp. 155-248. [Names Domengine formation.] Arnold, Ralph, and Strong, A. M., 190.5, Some crystalline rocks of the San (Jabriel Mountains: Geol. Soc. America Bull., vol. 16, pp. 183-204. Anbury, Lewis E., 1906, The structural and industrial materials of California : California Min. Bur. Bull. 38. [Granite p. 364, graphite p. 280, magnetite p. 297.] Bailey, T. L., 1943, Late Pleistocene Coast Range orogensis in .southern California : Geol. Soc. America Bull., pp. 1.549-1.568. Balk, R., 1931, Structural geology of the Adirondack anortho- site: Mineral und petrog. Mitteil., Bd. 45, pp. 308-432. Balk, R., 19.37, Structural behavior of igneous rocks : Geol. Soc. America Mem. 5, 170 pp. Ball, S. H., 1907, Titaniferous iron ore of Iron Mt., Wvo. : U. S. Geol. Survey Bull. 315, pp. 206-212. Bailey, Thomas L., and .Tnhns. Richard H.. 19.54, Geology of the Transverse Range province, southern California : California Div. Mines Bull. 170, ch. 2, contrib. 6, and geologic map (pi. 4). Barton, Cecil L., and Sampson, Norman N., 19.50, Placerita oil field: California Div. Oil and (ias, Summarv of operations, pp. 5-14. Beverly, Burt .Jr., 19.34, Graphite deposits in Los Angeles County, California : Econ. Geology, vol. 29, iip. 346-3.55. Birman, Joseph H., 1950, Geology of the upper Tick Canyon area, California: California Inst. Technology M.S. thesis (unpub.). Blake, W. P., 1857, Geological report : II. S. Pacific R.R. Expl., U. S. 33 Cong. Senate Ex. Doc. 78, vol. 5, 310 pp. Boalich, E. S., 1923, Notes on iron ore occurrences in Cali- fornia : California Min. Bur. Rept. 18, pp. 110-113. Bowen, N. L., 1917, The problem of the anorthosites : Jour. Geology, vol. 25, pp. 209-243. ^^,JJrown, Arthur B., and Kew, \V. S. W., 1932, Occurrence of ''t)!! in metamorphic rocks of the San Gabriel Mountains, Los Angeles County, California : Am. Assoc. Petroleum Geologists Bull., vol. 16, pp. 777-785. Brown, R. A., Cservenyak, F. .1., Anderberg, R. G., Kandiner, H. J., and Frattala, F. J., 1947, Recovery of alumina from Wyo- ming anorthosite by the lime-soda-sinter process: I'. S. Bur. Mines, Rept. Inv. 4132, 127 pp. Buddington, A. F., 19.39, Adirondack igneous rocks and their metamorphism : Geol. Soc. America, Mem. 7, 3.54 pp. Buddington, A. F., 1943, Some petrological concepts and the interior of the earth ; Am. Mineralogist, vol. 28, pp. 119-140. Buddington, A. F., Fahey, .Joseph, and Vlisidis, Angelina, 1955, Thermometric and petrogenetic significance of titaniferous magne- tite : Am. Jour. Sci., vol. 2,53, pp. 497.5,32. Burris, Milton D., Geology of east and west abutments of upper San Fernando Dam, 1942, and Geological observations at lower San Fernando Dam, 1943: Repts. Dept. Water and Power, City of Los Angeles (unpuli.). California Div. Oil and Gas, 19.5.3, Summary of Operations, January-.Iune. [Production statistics, pp. 27-40.] Clark, B. L., 1921, The marine Tertiary of the west coast of the T'nited States; its sequence, paleogeography, and the problems of correlation : Jour. Geology, vol. 29, pp. 583-614. Claypole, E. W., 1901, Sierra Madre near Pasadena, California : Geol. Soc. America Bull., vol. 12, p. 494. Clements, Thomas, 1937, Structure of southeastern part of Tejon quadrangle, California : Am. Assoc. Petroleum Geologists Bull., pp. 212-232. Clements, Thomas, and Oakeshott, Gordon B., 1935, Lower Eocene (Martinez) of San Gabriel Mountains (absts.): Pan-Am. Geologist, vol. 61, no. 4, pp. .307-08, May 1934 . . . Geol. Soc. America Proc. 19.34, p. 310, June 1935. Coats, Robert R., 1936, Primary banding in basic plutonic rocks: .I2(! 2035. Crowell. John C., 1954, Strike-slip displacement of the San Gabriel fault, southern California : California Div. Mines Bull. 170, ch. 4, contrib. 6. Crowell, John ('., 1957, Geology of the Orocopia Mountains, southeastern California (abst.) : Am. Assoc. Petroleum (ieologists, 34th Ann. Meeting Pacific Section, Los Angeles. Cushman, J. A., anos Angeles, M.A. thesis (unpub.). Davis, William M., 1927, The rifts of southern California : Am. Jour. Sci., vol. 13, pp. 57-72. Dawson, Chas. A. Jr., 1937, Petrology of the igneous complex near Lang, California : California Inst. Technology M.S. thesis (unpub.). deChardin, P. Teilhard, and Stirton, R. A., 19.34, A correlation of some Miocene and Pliocene mammalian assemblages in North America and Asia with a discussion of the Miocene-Pliocene boundary : Univ. California Publ. Geol. Sci., vol. 23, pp. 277-290. Dehlinger, Peter, 1943, A magnetic survey of Sand Canyon for placer deposits, San Gabriel Mountains, California : California Inst. Technology M.S. thesis (unpub.). Dibblee, T. W. Jr., 1952, Geology of the Saltdale quadrangle, California : California Div. Mines Bull. 160. Dickerson, R. E., 1914, The Martinez Eocene and associated formations at Rock Creek (California) : Univ. California Dept. Geol. Sci. Bull., vol. 8, pp. 289-298. Dort, Wakefield Jr., 1948, The geology of a portion of the eastern Ventura Basin, California : California Inst. Technology M.S. thesis (unpub.). Durham, J. Wyatt, 1948, Age of post Mint Canyon marine beds: Geol. Soc. America Bull., vol. 59, p. 1386. Durham, J. Wyatt, 1949, "Dendrasler elmiierensis Durham, n. sp." ; Am. Jour. Sci., pp. 49-62. Durham, J. Wyatt. 19.54. The marine Cenozoic of southern Cali- fornia : California Div. Mines Bull. 170, ch. 3, contrib. 4. Durham, J. AVyatt, Jahns, Richard H., and Savage, Donald E., 19.54, Marine-nonmarine relationships in the Cenozoic section of California : California Div. Mines Bull. 170, ch. 3, contrib. 7. Eakle, Arthur S., 1912, Neoeolemanite, a variety of colemanite, and howlite from Lang, Los Angeles County, California (abst.) : Univ. California Dept. Geol. Sci. Bull., pp. 179-189, 1911. Eaton, J. E., 1939, Ridge basin, California : Am. Assoc. Petro- leum Geologists, pp. 5,33.534. [Age of Mint Canyon formation.] Edwards, Everett C, 19.33. Pliocene conglomerates of the Los Angeles Basin and their paleogeographic significance : California Inst. Technology Ph.D. thesis (unpub.). Ehlig, Perry, 1956, (Jeology of the Mt. Baldy region : Pacific Petroleum Geologist, May 19.56 (Talk of April 5 to Los Angeles luncheon meeting, Am. Assoc. Petroleum Geologists). Eldridge, George II. , and Arnold, Ralph, 1907, The Santa Clara Valley, Puente Hills, and Los Angeles oil district.s. southern Cali- fornia : U. S. Geol. Survey Bull. 309, pp. 22, 96-98. [Elsmere Canyon.] English, W. A., 1926, Geology and oil resources of the Puente Hills region, southern California : U. S. Geol. Survey Bull. 768. English, Walter A.. 1914a, The Fernando group near Newhall, California : Univ. California Dept. Geol. Sci. Bull., pp. 20.3-218. [Historical review of Elsmere Canyon area.] English, Walter A.. 1914b, The Agasoma-like gastropods of the California Tertiary : Univ. California Dept. Geol. Sci. Bull., pp. 243-2.56. [Some Elsmere Canyon forms.] 124 California Division of Mines [Bull. 172 Eric, John H.. 1048, Tabulated list of copper deposits in Cali- fornia : California Div. Mines Bull. 144. [Pacoima Canyon com- ple.x sulfide oi-e, p. 259.] Eskola. P., 10r)2, On the granulites of Lapland : Am. Jour. Sci., Bowen vol., pt. 1, pp. 133-171. Evrard, Pierre, 1940, The differentiation of titaniferous magmas: Econ. Ceolog.v, pp. 210-232. Ford, Waldo E., 1941, Geolog.v and oil re.serves of a portion of the Xewhall district, Los Angeles Count.v, California : University of California, Los Angeles SI. A. thesis (unpuh.). Foshag, William F., 1918, Ulexite from Lang, California : Am. Jlineralogist, p. .35. Foshag, 'William F., 1921, The origin of the colemanite deposits of California : Econ. Geology, pp. 199-214. Fowler, Katharine S., 1930, The anorthosite area of the Lara- mie Mountains, Wyoming: Am. Jour. Sci., vol. 19, pp. 305-31.5, 373-403. Frey, Eugene, 1946, Exploration of Iron Mt. titaniferous mag- netite deposits, Albany Co., Wye: U. S. Bur. Mines Rept. Inv. 3968. Gabb, W. M.. 1869, Paleontology II, Geological Survey of Cali- fornia. Gale, H. S., 1914, The origin of colemanite deposits : IJ. S. Geol. Survey Prof. Paper 85, pp. 3-9, 1913 (abst.) and Washington Acad. Sci. Jour., vol. 4, pp. 165-166. Gale, H. S., and others, 1933, Southern California : 16th Inter- nat. Geol. Cong. Guidebook 15, excursion CI, 68 p. [W. S. W. Kew, Los Angeles to Santa Barbara, pp. 48-49, and pi. 11, geologic map.] Gay, Thomas E. Jr., and Hoffman, Samuel R., 1954, Mines and mineral deposits of I^os Angeles County. California: California Jour. Jlines and Geology, vol. .")4, pp. 467-709. Gillson, Joseph L., 1932, Genesis of the ilmenite deposits of St. Iirbain County, Charlevoix, Quebec: Econ. Geology, pp. 5.54-577. Goodyear, W. A., 1888, Los Angeles County : California Min. Bur. Rept. 8, pp. .33.5-342. Grant, U. S. IV, and Gale, H. R., 1931, Catalogue of the marine Pliocene and Pleistocene nioUusca of California ; San Diego Soc. Nat. History Mem., vol. 1, 1036 p. Grout, F. F., 1928, Anorthosite and granite as differentiates of a diabase sill on Pigeon Point, Minnesota : Geol. Soc. America Bull., vol. 39, pp. 555-578. Guillou, R. B., 1953, Geology of the Johnston grade area, San Bernardino County, California : California Div. Mines, Special Rept. 31. Hagner, Arthur F., 1951, Anorthosite of the Laramie Range, All)any County, Wyoming, as a possible source of alumina : Wyo- ming (ieol. Survey Bull. 43, March. 15 pp. Hedden, A. H. Jr., 1948, The geology of the upper Tick Canyon area, Los Angeles County, California : California Inst. Technology M.S. thesis (unpnb.). Hershey, O. H., 1902a, The Qnaternary of southern California : rniv. California Dept. Geol. Sci. Bull., vol. 3. pp. 1-29. Hershey, O. H., 1902b, Some crystalline rocks of southern Cali- fornia : Am. Geologist, vol. 29, pp. 273-290. Hershey, O. H., 1902c, Some Tertiary formations of southern California : Am. Geologist, vol. 20, pp. 340-372. Hershey, O. H., 1902d, The Quaternary of southern California : I'niv. California Dept. Geol. Sci. Bull., vol. 3, no. 1, pp. 1-29. [Includes reconnaissance geologic map of southern California showing units covering San Fernando (|u,-i(lnuigle. | Hershey, O. H., 1912, The Belt and Pelona series : Am. Jour. Sci., (4),' vol. 34, pp. 26.3-273. Hietanen, Anna, 1947, Archean geology of the Turku district in southwestern Finland : Geol. Soc. America Bull., vol. .58, pj). 1019- 1084. [Charnockite series, p. 1035.] Higgs, Donald V., 10.50, Anorthosite and related rocks of the western San Gabriel Mountains, southern California: I'luv. Cali fornia, Los Angeles, Ph.D thesis (.see page 19.54a). Higgs, Donald V., 19.54a, Anorthosite and related rocks of the western San Gabriel Mountains, southern California: Univ. Cali- fornia Dept. Geol. Sci. Bull., vol. 30, pp. 171-222. Higgs, Donald \'., 1954b, Anorthosite complex of (he western San Gabriel Mountains, southern California : California Div. Mines Bull. 170, ch. 7, contrib. 8. Hill, II. S., 19.39, Petrography of the Pelona schist of .southern California: Pomona College, M.A. thesis (19.39). Hill, M. L., 1930, Structure of the San Gal>riel Mountains north of I^os Angeles, California: I'niv. ("alifornia Dept. (!eol. Sci. Bull., vol. 19, pp. 137-170. Hill, M. L., 1954, Tectonics of faulting in southern California : California Div. Mines Bull. 170, ch. 4, contrib. 1. Hill, R. T., 1920, The rifts of southern California : Seismol. Soc. America Bull., vol. 10, pp. 146-149. Hill, R. T., 1928, Southern California geology and Los Angeles earthquakes : Southern California Acad. Sci., Los Angeles, 227 p. Hill, R. T., 1930, Some new data on the major fault blocks of southern California (abst. I : Geol. Soc. America Bull., vol. 41. pp. 53-54. Holland, T. H., 1893, The petrology of Job Charnoek's tomb- stone : Jour. As. Soc. Bengal, vol. 62, pt. 2. Holloway, John N., 1940, Areal geology and contact relations of the ba.sement complex and later sediments, westend of the San Gabriel Mountains, California : California Inst. Technology M.S. thesis (unpub, ). Holmes, L. C, and others, 1917, Soil survey of the San Fernando Valley area, California, U. S. Dept. of Agriculture, 61 pp., map. Holser, William T., 1946, Geology of the Mint Canyon area, I>os Angeles County, California : California Inst. Technology M.S. thesis (unpub.). Hoots, H. W., 1930, Geology of the eastern part of the Santa Monica Mountains, Los Angeles County, California : U. S. Geol. Survey Prof. Paper 165, pp. 83-134. Howell, B. F. Jr., 1949, Structural geology of the region between Pacoima and Little Tujunga Canyons, San Gabriel Mountains, California : California Inst. Technology Ph.D. Minor thesis (unpub.) . Howell, Ben F. Jr., 1954, Geology of the Little Tujunga area, Los Angeles County : California Div. Mines Bull. 170, ch. 1, map sheet 10. Hud.son, Frank S., 1955, Folding of unmetamorphosed strata superadjacent to massive basement rocks : Am. Assoc. Petroleum Geologists Bull., vol. 39, pp. 2038-2052. Little Tujunga area as example. Hutchinson, A., 1912, On the identity of neocolemanite with colemanite: Miueralog. Mag., vol. 16, pp. 2.39-240. Irwin, William P., 19.50, The Vasquez series in the upper Tick Canyon area, Los Angeles County, California : California Inst. Technology M.S. thesis (unpub.). .lahns, Richard H., 1939, Miocene stratigraphy of the eastern- most Ventura basin, California ; A preliminary statement : Am. Jour. Sci., vol. 237, pp. 818-825. Jahns, Richard H., 1040, Stratigraphy of the easternmost Ven- tura basin, California, with a description of a new lower Miocene mammalian f:iuna from the Tick Canyon formation: Carnegie Inst. Washington, Bull. 514, pp. 147-194. Jahns, Richard H., 19.54, Pegmatites of southern California : California Div. Mines, Bull. 170, ch. 7, contrib. 5 Jahns, Richard H., and Muehlberger, William R., 19.54, Geology of the Soledad basin, Los Angeles County : California Div. Mines Bull. 170, ch. 1, map sheet 6. Jennings, Charles W., and Troxel, Bennie W., 1954, Ventura basin and adjacent areas: California Div. Mines Bull. 170, ch. 10, geol. guide 2. Johannsen, Albert, 1932, A descriptive petrography of the igne- ous rocks, vol. 3. Johu.son, H. R., and Warren, V. C, 1927, San Gabriel investi- gation: California Div. Water Rights Bull., vol. 5, pp. 73-101. Johnston, Robert L., 1938, Geology of a portion of the western Verdugo Mountains: Univ. California, Los Angeles, M.A. thesis (unpub.) . Judson, Jack, 1935, Geology of the LeBrun and Mint Canyon quadrangles, Los Angeles (bounty, California : California Inst. Technology M.S. thesis (unpub.). Kanakoff, George P., 19,54, A new Kelletia from the Pliocene of California : Southern California Acad. Sci. Bull., vol. 53, pt. 2, pp. 114-117. Kew, W. S. W., 1923, (Jeologic formations of a part of southern California and their correlation: Am. Assoc. I'etroleum Geologists Bull., vol. 7, pp. 411-420. Kew, W. S. W., 1924a, Faulting in the western part of the San Gabriel Mountains : Geol. Soc. America Bull., vol. 35, pp. 165-166 ( abst. ) . Kew, W. S. W., 1924b, (Jeology and oil resources of part of Los Angeles and Ventura Counties, California : U. S. Geol. Survey Bull. 7.53, 197 pp. Kew, W. S. W., 1032, Southern California (I>os Angeles to Santa Barbara): Interuat. Geol. Cong. Guiclcbonk 15. [Pliocene, p. 49] \97)S\ San Fernando Quadkanole — Oakeshott 125 Kfw. \V. S. \V., 1!M8, Ncwliiill nil lirlil : ("alifoniia I>iv. Mines Hull. IIS, pp. 412-41(i. Kli'iiipcll. K. M.. llK'iS, Miocene strntiKriiphy of California: Am. Assoc. I'etrolenm Geologists Bull. [Arc of Sand Canyon Modelo, p. 71.] Kramer. Henry, and Allen, Iloliert P., 1056, A restudy of baker- ite. priceite and veatchite : Am. MiiieialoKist, Sept. -Oct. [Veatchite specimen from LanK.] Larsen, K. S. .Jr., Keevil, X. H., and Harrison, H. C, 1!>52. Method for determininc the age of igneous roclimestone in (California: California Jour. Mines and Geology, vol. 43, pp. 249-250. (Uolomitic lime- stone. ) Loughlin, G. F., 1923, An interesting case of a dangerous aggre- gate : Am. Concrete Inst. Proc, vol. 19, pp. 142-155. Luce, John W., 1935, A field trip to Tick and Red Rock Can- yons : Pacific Mineralogist, pp. 14-17. MacNeill, Robert J., 1948, The geology of the Humphreys Sta- tion area, Los Angeles County, California : California Inst. Tech- nology M.S. thesis (unpub.). Marcou, Jules, 1855, Report of explorations near the 35th paral- lel : U. S. Pacific R. R. Expl., V. S. 33 Cong., H. Ex. Doc. 129, vol. 18, pt. 2, pp. 40-48. Maxson, John H.. 1930, A Tertiary mammalian fauna from the Mint Canyon formation of .southern California : Carnegie Inst. Washington Pub. 404. Maxson, John H., 1938a, Miocene-Pliocene boundary (abst.): Am. Assoc. Petroleum Geologists Bull., pp. 1716-1717. Maxson. John H.. 19381), Geologic age of earliest North American Ilipparwn faunas (abst.) : Geol. Soc. America Bull., p. 1916. McGrew, P. O., and Meade, G. E., 1938, The bearing of the Val- entine area in Miocene-Pliocene correlation : Am. Jour. Sci., 5th ser., vol. 36, p. 197. McLaughlin, R. P., and Waring, C. A., 1914, Petroleum indu.stry of California : California INIin. Bur. Bull. 69, 519 pp. McMasters, J. H., 1933, Eocene Llajas formation, Ventura County, California (abst.) : Geol. Soc. America Bull. 44, pp. 217- 218. Menard. H. W., 1947, The geology of the Agua Dulce Canyon area: California Inst. Technology M.S. thesis (unpub.). Mendenhall, W. C, 1908a, Foothill belt, southern California : U. S. Geol. Survey Water-Supply Paper 219. Mendenhall, W. C, 1908b, Two mountain ranges of southern California (San Bernardino and San Gabriel) (abst.) : Geol. Soc. America Bidl., vol. 18. pp. 660-661. Merriam, Charles W., 1954, Rocks of Paleozoic age in southern California : California Div. Mines Bull. 170, ch. 3, contrib. 2. Merriam, Richard. 1953, Alkali-aggregate reaction in California concrete aggregates: California Div. Mines, Special Rept. 27 [An- orthosite from the western San Gabriel Jlountains, p. 8, 10]. Merrill, Frederick J. H., 1915-16, Iron (Los Angeles County I : California Miu. Bur. Rept. 15, p. 478. Miller, W. J., 1926, Crystalline rocks of the middle-southern San Gabriel Mountains. California (abst.) : Geol. Soc. America Bull., vol. 37, p. 149. Miller, W. J., 1928a, (jeomorphology of the southwestern San Gabriel Mountains of California : Univ. (California Dept. Geol. Sci. Bull., vol. 17. pp. 193-240. Miller, AV. J., 1928b. Anorthosite in Los Angeles County, Cali- fornia : Geol. Soc. America Bull., vol. 39, pp. 164-165 . . . Pan. Am. Geologist, vol. 49, pp. 73-74. Miller, W. J., 1929. Rocks of the southwestern San Gabriel Mountains (summary statement): Pan. Am. Geologist, vol. 51, pp. 369-370. Miller, W. J., 1930. Rocks of the southwestern San Gabriel Mountains, California (al)st.) : Geol. Soc. America Bull., vol. 41, p. 149. Miller, W. J.. 1931. Anorthosite in Los Angeles County, Califor- nia : Jour. Geology, vol. 39, pp. 331-344. ---- -Miller, AV. J., 1934, Geology of the western San Gabriel Moun- tains of California : Univ. California at I>os Angeles Pub. in Math. & Phys. Sci., vol. 1. pp. 1-114. Moodv, J. D., and Hill, M. J., 19.56. Wrench-fault tectonics : Geol. Soc. America Bull., vol. 67, pp. 1207-1246. Jloore. (^harles H. Jr.. 1940. Origin of the nelsonite dikes of Amherst County, Virginia: Ecou. Geoln^-v. vol. 35, pp. 629-645. Moorhousc, W. \\ ., 1938, Some titaniferous magnetites of the San (labriel Mountains, Los Angeles County, California: Econ. (jeology, pp. 737-748. Muehlberger, W. K., 1954, Deposition and deformation in the northern Soledad basin, Los Angeles County, California: California Inst. Technology Ph.D. thesis (unpub.). Murdoch, Joseph, 1945, Probertite from Los Angeles County, California : Am. Mineralogist, pp. 719-721. Murdoch, Joseph, and Webb, Robert W., 1948, Minerals of Cali- fornia : California Div. Mines Bull. 136, and Supp., Nov. 1952. Murdoch, Joseph, and Webb, Robert W., 1954, Minerals in southern California : California Div. Mines Bull. 170, ch. 7, ct)ntrib. 1. Murdoch, Jo.seph, and Webb, Robert W., 1956, Minerals in Cali- fornia : California Div. Mines, Bull. 173. National Research Council, 1948, Rock-color chart (distributed by Geol. Soc. America). Natland, M. L., 1953, Correlation of Pleistocene and Pliocene stages : Pacific Petroleum Geologist, vol. 7, no. 2, p. 2. Natland, M. L., and Rothwell, W. T., Jr., 1954, Fo.ssil fora- minifera of the Los Angeles and Ventura regions, California : Cali- fornia Div. Mines Bull. 170, ch. 3, contrib. 5. Neuerburg, George J., 1954, AUanite pegmatite, San Gabriel Mountains, Los Angeles County, California : Am. Mineralogist, Sept.-Oct., pp. 831-834. Neuerburg, George J., and Gottfried, David, 1954, Age deter- minations of the San (labriel anorthosite massif, California : Geol. Soc. America Bull., pp. 465-466. Noble, L. F.. 19.54, Geology of the Valyermo quadrangle and vicinity. California: V. S. Geol. Survey, GQ 50. Nociiolds, S. R., 19,54, Average chemical composition of some igneous rocks : Geol. Soc. America Bull., vol. 65, pp. 1007-1032. OaUeshott, Gordon B., 1936. A detailed geologic section across the western San Gabriel Mountains of California : Univ. Southern California Ph.D. thesis. ^^Oakeshott, Gordon B., 1937, Geology and mineral deposits of the western San Galiriel Mountains, Los Angeles County: California Jour. Mines and Geology, vol. 33. pp. 215-249. Oakeshott, Gordon H.. 1938. Geomorphology from detailed geo- logic mapping, western San Gabriel Mountains : Assoc. Pacific Coast Geographers. Yearl)ook. vol. 4. pp. 30-31. Oakeshott, Gordon B., 1948, Titaniferous iron-ore deposits of the western San Gal)riel Mountains. Los Angeles County, Califor- nia : California Div. Mines, Bull. 129, pt. P, p. 245-266. Oakeshott, Gordon B., 1949. Titanoniagnetite rocks of the west- ern San Gabriel Mountains. California (alist.) : Geol. Soc. Amer- ica Bull., vol. 60, pt. 2, pp. 1942-1943. Oakeshott, Gordon B.. 1950a, Geology of the Placerita oil field, Los Angeles County. California: California Jour. Mines and Geology, vol. 46. pp. 43-S(). Oakeshott, Gordon B., 19.50b. (Jraphite: California Div. Mines Bull. 1.56, pp. 169-171 . . . Titanium : pp. 352-355. Oakeshott, Gordon B., 1951a, Southern mountain region, in Pos- sible future petroleum provinces of North America : Am. As.soc. Petroleum Geologists Bull., pp. 256-2,59. Oakeshott, Gordon B., 1951b, San Gal>riel and related faults in the western San Gabriel Mountains, California (abst.) : Geol. Soc. America Bull., vol. 62, pt. 2. p. 1509. Oakeshott, Gordon R., 1951c, Geology of the northern margin of the San Fernando Valley, Los Angeles County (abst.) : Am. Assoc. Petroleum Geologists Bull., vol. 35, pp. 2631-32. Oakeshott, Gordon B.. 19,52, Geology of the northern margin of San Fernando Valley : Petroleum World, pp. 20-24. Oakeshott, Gordon B., 1954a, Geology of the Placerita oil field, Los Angeles County: California Div. Mines Bull. 170, ch. 9, map sheet 31. Oakeshott, Gordon B.. 1954b. Geology of the western San Gabnel Mountains, Los Angeles County: California Div. Mines Bull. 170. ch. 1, map sheet 9. Oakeshott, Gordon R., 19.57, Precambrian granulite in the west- ern San Gabriel Mountains. Los Angeles County, California (abst.) : Geol. Soc. America Bull., vol. 68, p. 1839. Oakeshot^ Gordon B., Jennings, Charles AV., and Turner, Mort D.. 1954, Correlation of sedimentary formations in southern Cali- fornia: California Div. Mines Bull. 170. ch. 3, contrib. 1. (Office of Naval Research, Mar. 1949, Titanium, 157 p. Orr, James M., 1938, Investigation of the geological occurrence and use of titanium with special reference to the San Gabriel titanium deposits, California : California Inst. Technology M.S. thesis (unpub.). 126 Cai.ifornia Division of Mines [Bull. 172 Osbonir, ]■". !•".. 1!>2N, CiMtain ni;is;m:ili<' tit:inifiTi)iis iron ores and their origin: lOoon. (ieoloR.v, p. 724-7f the Tpiior Tick Canyon area. IjOS Angeles Count.v, Californi.-i : California Inst. TeohnoloRv M.S. thesis (unpub. ). Patchick, Paul F., l!)r)4. Environment and provenances of the Agua Puloe anorthosite-rich fanglomerate, I,os Angeles Connt.v, California : The Compass, Ma.v ]!t.")4. Patchick, Paul F., l!).'').'j, A remarkal>le occurrence of allanite and zircon er.vstals from a southern California pegmatite: Hocks and Minerals, Ma.v-June, pp. 237-246. Pfaffman, George A., ]!>41. The geolog.v of the Martinez forma- tion of the Tejou and Klizaheth Lake quadrangles, California : Univ. Southern California M.S. thesis (unpuh. ). Pichamuthu, ('. S., 1!».").S, The charnockite problem : My.sore Geologists' Assoc, Bangalore. India, 17H pp. Preston, E. H., 18!H), I>os Angeles County: California Min. Hur. Kept. 9, pp. 18!l-210. Putnam, W. C, and Bailey, T. L., 1!)42, Geomorphology of the Ventura region, California : C.eol. Soc. America Bull., pp. 691-754. Ramberg, Hans, 194S, Titanic iron ore formed by di.ssociation of silicates in granulite facies : P'con. Geology, pp. 5r>;{-570. Ransome, F. L., 192S, Geology of the St. Francis dam site: Econ. Geology, vol. 23, pp. .'■m3-.")0.S. Reed, Ralph D., 1932, Southern California (section from the Repetto Hills to the Long Beach oil field) : Internat. Geol. Cong. Guidebook 15. [P. 31, Repetto formation named. 1 Reed, R. D., and Hollister, .1. S., 193(>, Structural evolution of southern (California : Am. Assoc. Petroleum Geologists, pp. 40-43. [Age Mint Canyon formation.] Rice, H. M. Anthony, 1934, A San Diego fauna in the Newhall quadrangle, California : California Inst. Tech. Ph.D. minor thesis (unpuh.). Richmond, James F., 1954, Petrology and structure of the San Bernardino Mountains north of Rig Bear Lake, California : Stan- ford Univ. Ph.D. thesis (unpuh.). Ross, Clarence S., 1933, Titanium deposits of the Roseland dis- trict, Internat. Geol. Cong. Guidebook 11, northern Virginia. Ross, Clarence S., 1936, Mineralization of the Virginia titanium deposits: Am. Mineralogist, vol. 21. Ross, Clarence S., 1941, Occurrence and origin of the titanium deposits of Nelson and Amherst Counties, Virginia : U. S. Geol. Survey Prof. Paper 19S. 38 p. Ryan, C. W., 1933, The ilmenite apatite deposits of west-central Virginia : Econ. Oology, vol. 28, pp. 266-275. Sampson, R. J., 1937, Mineral resources of Los Angeles County : California jour. Mines and Geology, vol. 33, pp. 173-213. Sampson, R. J., 1949, I>os Angeles County : California Div. Mines Bull. 142, pp. 62-65. Savage, Donald E., and Downs, Theodore, 19.54, Cenozoic land life of .southern California [illustrations by Owen J. Poe] : Cali- fornia Div. Mines Bull. 170, ch. 3. contrib. 6. Sharp, R. P., 19.30, Geology of the Ravenna quadrangle, Los Angeles County, California : California Inst. Technology M.S. thesis (unpub.) . . . (abst.) Pan. Am. Geologist 63:314, May 1935 . . . Geol. Soc. America, Proc. 1935. p. .3.36. Sheller, J. W., and others, 1952, Cenozoic correlation section across eastern Ventura basin (chart), sheet 2, Am. Assoc. Petro- leum Geologists. Shelton, J. S., 19.54, Miocene volcanism in coastal southern Cali- fornia : California Div. Mines Bull. 170, ch. 7, contrib. 4, p. 35. Simpson, E. C., 1934, Geology and mineral deposits of the p]liza- bfth Lake quadrangle. California : California Jour. Mines and Geol., Rept. .30, pp. 371-415. Sinclair. .1. D., 19.54, Erosion in the San Gabriel Mountains of California : .\m. (ieophysical Union. Trans. Apr. 1954, pp. 264-268. Singewald, J. T. Jr., 1913, The titaniferous iron ores in the United States; U. S. Bur. Mines Bull. 64, 145 pp. Smith, R. J., 1948, Ge(dogy of the Humphreys and Sylniar quadrangles: C.ilifornia Inst. Technology M.S. thesis (unpub.). Stirton, R. .V., 1933, Critical review of the Mint Canyon mam- malian fauna and its correlative significance: Am. Jour. Sci., 5th ser., vol. 26, p. .569. Stirton, R. A., 19.39, Significance of Tertiary mammalian faunas in Holarctic correlation with especial reference to the Pliocene of California : Jour. Paleontology, pp. 130-137. Storey, H. E., 1948, Geology of the San Gabriel Mountains. California, and its relation to water distribution, California Div. Forestry, 19 pp. Storms, W. H., 1893, Los Angeles County: California Min. Bur. Rept. 11, pp. 243-248. Switzer, George, 1938, Veatchite, a new calcium borate from L.ing, California : Am. Mineralogist, vol. 23, pp. 409-411. Switzer, George, and Brannock, W. W., 1950, Composition of veatchite : Am. Mineralogist, vol. 35, pp. 90-92. [Corrects composi- tion to strontium borate.] Thomas, R. G., Marliave, E. C, James, L. B., and Bean, R. T., Geology and hydrology of Ventura County : California Div. Mines Bull. 170, ch. 6, contrib. 3, pi. 2. [Areal geology.] Trask, J. B., 1855, Report on geology of the coast mountains : California Sen. Doc. 14, 95 p. Troxell, Harold C, and others, 1942, Floods of March 19.38 in southern California : U. S. Geol. Survey, Water-Supply Paper 844, .399 p. [Includes runoff and rainfall data in western San Gabriel .Mountains.] Troxell, Harold C, and Hofmann, Walter, 1954, Hydrology of the I>os Angeles region: California Div. Mines Bull. 170, ch. 6, contrib. 1. Tucker, W. B., 1920, Los Angeles County : California Min. Bur. Rept. 17, pp. 317-322. Tucker, W. B., 1923, Los Angeles County : California Min. Bur. Rept. 19, p. 164. Tucker, W. B., 1924, Los Angeles County : California Min. Bur. Rept. 20, pp. 42-43. Tucker, W. B., 1927, Iron ; Titaniferous iron deposits ; the utilization and metallurgy of titanium: California Min. Bur. Rept. 23, pp. 295-313. [Complex sulfide ore, pp. 288 and 315.] Tucker, W. B., 1934, Los Angeles County : California Min. Bur. Rept. 30. pp. 318-319. Tucker, W. B., 1938, Mineral development and mining activity in southern California during the year 1937: California Div. Mines Rept. 34, pp. 8-19. Tucker, W. B., and Sampson, R. J., 1940, Current mining activity in southern California : California Div. Mines Rept. 36, pp. 9-82. Turner, Francis J., 1948, Mineralogical and structural evolution of the metamorphic rocks : Geol. Soc. America, Mem. 30, 342 pp. Turner, F. J., and Verhoogen, Jean, 1951, Igneous and meta- morphic petrology, Mc(Jraw-Hill. [pp. 252-257, the Pre-Cambrian anorthosite association.] Uhrig, L. F., 1936, Structural study of a portion of the Lang and Humphreys quadrangles, Los Angeles County, California : California Inst. Technology M.S. thesis (unpub.). U. S. Army, Corps of Engineers, South Pacific Division, 1947, Report on petrographic examination of concrete pop-outs from Sepulveda and Hansen dams, and the I>os Angeles River channel, pp. 1-8, 8 pis., 2 tables (unpub.). U. S'. Army, Corps of Engineers, Los Angeles District, 1954, Brief descriptions of three flood-control dams in southern Califor- nia : Engineering Geology Packet, Geol. Soc. America meetings, Nov. 1954, assembled by John F. Mann, Jr. et al., Univ. Southern California [Hansen Dam. 2 pp. 2 plates.] U. S. Forest Service, 1936, Vegetation types of California : San Fernando quadrangle. [Scale 1 :62,500, topographic base, one sheet map and text.] U. S. Geological Survey, 19.54, Surfac-e water supply of the United States, 1952, Part 11 Pacific slope basins in California: U. S. Geol. Survey Water-Supply Paper 1245, pp. 114-119, 134. [Discharge Pacoima Creek, Tujunga Creek, Little Tujunga Creek, and Santa Clara River near Saugus. ] Vaughan, K. E., 1922, Oology of the San Bernardino Mountains north of San Gorgonio Pass: Univ. California Dept. (!eol. Sci. Bull., vol. 13, pp. 319-411. Ver Planck, William E., 1952, Gypsum in California : California Div. Mines Bull. 163. [Mint Canyon gypsum, p. 40.] Ver Planck, William E., 1954, Salines in southern California : California Div. Mines Bull. 170, ch. 8. contrib. 1. Wallace, Robert E., 1940. Vidcanic tuff beds of the Mint Canyon formation: California Inst. Technology M.S. thesis (unpub.). Walling, R. W., 1934, Report on Newhall oil field : California Div. Oil and Gas, Summary of operations, California oil fields, pp. 38-57. [Elsmere area, pp. 38-43; Whitney Canyon area, pp. 43-46; Placerita Canyon area, pp. 46-50.] Waterfall, L. N., 1929, .\ contribution to the paleontology of the Fernando group, Ventura County, California : Univ. California Dept. Geol. Sci. Bull., vol. 18, pp. 71-92. 1!).')81 Han Fkrnando Qttadrangle — Oakeshott 127 Wiitsiin. T. 1... !iii.">, Geological Survey of California, Geology, vol. 1, 498 pp. [San (Jaliriel Range, pp. ITl-lT.'i.] Wiese, John H., 19."iO, Geology and mineral resources of the Neenach quadrangle. California: California Div. Mines Bull. l.">3, 53 pp. Williams, Howel, Turner. Francis J., and Gilbert, Charles M., 19."i4, Petrography, W. H. Freeman, 406 pp. Willis, Bailey, & Willis, Roliin, 19.34, Geologic structures, McGraw-Hill, pp. 8;}. 2.31-234. [Folding above a competent forma- tion in an anticline.] Willis. Robin. 19.">2 (March). Placerita oil field: Am. Assoc. Petroleum Geologists field trip guidebook for joint annual meeting, Los Angeles, pp. 32-41. Winterer, Edward L.. 19."i2 (Marcn), Burliank to Placerita road log (pp. 29-31) and Placerita to Pirn road log (pp. 4145) : Am. A.ssoc. Petroleum Geologists field trip guidebook for joint annual meeting, Los Angeles. Winterer, E. L., and Durham, David L., 1951, A formation of late Miocene and early Pliocene age on the north slope of the Santa Su.sjina mountains;, California : Am. Assoc. Petroleum Geol- ogists Bull., vol. 35, p. 2631. Winterer, Edward L.. and Durham, David L., 1954, Geology of a part of the eastern Ventura basin, Los Angeles County : Cali- fornia Div. Mines Bull. 170, ch. 1, map sheet 5. Wissler, Stanley G.. 1948, and Crawford, F. L>., The Miocene- Pliocene boundary in the Los Angeles Basin from the viewpoint of the microstratigrapher (abst.) : California Oil World, vol. 41, no. 21, p. 11. Woodford, A. O., and Harriss, T. F., 1928, Geology of Black- hawk Canyon, San Bernardino Mountains, California : Univ. Cali- fornia, Dept. Geol. Sci. Bull., vol. 17, pp. 265.304. Woodford, A. O., Schoelhamer, J. E., Vedder, J. G., and Yerkes, R. F., 19.54, Geology of the I^s Angeles basin : California Div. Mines Bull. 170. ch. 2, contrib. 5. Wdcidriug. W. P.. 1929, Age of the Modelo formation of the Santa Monica Mountains, California : Geol. Soc. American Bull., p. 1.5.5. I Haskell Can>ou Modelo beds appro.x. e<|uivalent of Cierbo.] Woodring. W. P., Stewart, Ralph, and Richards, R. W., 1940, (Geology of the Kettli'inan Hills oil fiehl. California : U. S. Geol. Survey, Prof. Paper 195. 170 pp. Wozal). David H., 1952, The chemical characteristics of the ground water in San Fernando Valley. California : I'niv. Southern California .M.A. thesis (unpub.). Wright, Lauren A., 1943, (Jeology of the .Mint Canyon series and its relation to the M.i. [Bull. 172 Map no. Operator S-T-R Year completed or abandoned Depth (feet) Geology Production Statu 83 84 85 86 87 88 89 90 91 92 93 94 Carl R. Pohl & .\8aociates. Tick Canyon Oil Syndi- cate Mojave Petroleum Co. .- Sun Valley Oil Co., Inc. (E. T. Wix) C. M. Hood (J. M. But- ler) S.D.M. Oil Co --- Fairview Exploration Co. Redwood Oil Co. Pohl-Green 1 Well No. 1 . Jennings Lease 1 Benz Anita 1. Lathrop 1 . HCL 1 Mitchell 1. Archie C. Myers - Nadeau 2. B. V. DeLanty..- Contratto Oil Co. Nadeau 1 . Jill 1 96 97 98 99 100 101 103 104 105 106 107 108 Lomita Oil Well Service Co. Solemint Petroleum Corp. Continental Oil Co Tarver 1- Firedart Oil Co.. Kenneth Oil Co.. Anne .\rnold Lyle A. Garner,. Carlisle 1 Wallace USL I Mitchell 1 Shepherd Roy 1 Hanson 2. Brooks 1 - - Fislier Lease Co.. Fisher 1. Sandee Oil Co Turner and Trickett- Carter. W. J Brooks 1 - No. 1 Carter-Earl 1 Walker, Pierson & Mc- Gregor California Newhall Oil Co, H. C. Hicks No. I- LUlie 1 29-5N-15W 35-5N-15W 33-5N-14W 8-4N-15W 14-4N-15W 13 4N-15W 24-4N-1SW 22-4N-15W 28-JN-15W 28-4N-15W 28-4N-15W 29-4N-15W 29-4N-15W 27-4N-15W 33-4N-15W 33-4N-15W 34-4N.15W 36-4N-15W 1-3N-15W 2-3N-15W 2-3N-15W 4-3N-I5W 5-3N-15W 32-4N-15W 8-3N-15W 8-3N-I5W 1923 1949 1941 old well 1950 1950 1948 1949 1950 1949 1948 1950 1950 1950 1951 pre-1925 1948 pre-1925 pre- 1925 1930 TD 2331 TD 4391 TD 2543 TD 3470 TD 2497 TD 1088 TD 2733 TD 1390 ? TD 3427 TD 1529 TD 1680 TD 743 TD 1400 TD 6151 TD 2841 TD 2202 TD 1602 TD 1720 TD 3244 TD 4305 TD 965 TD 205 TD 320 TD 1865 Spudded in Mint Canyon; ss and sh 0-14 10; eg, ss and sh 1410-1732, eg 1732-2298. schist 2298-2331 Spudded in Mint Canyon fm. Spudded in Tick Canyon fm. . Spudded in Saugus. Mint Can- yon 1210 (?) to 3470. Blue sh 2900, brown sh 3010, sandy sh at bottom. Bottomed in hard sh Drilled in W. -dipping Mint Canyon beds. Drilled in W. -dipping Mint Canyon beds. Spudded in basal Mint Can- yon. Mint Canyon to bottom. Mint Canyon fm Mint Canyon fm Abandoned Abandoned No oil showings. Slight gas showings at 1700 and minor showings at var- ious points from 600 to bottom Spudded in alluvium above Mint Canyon fm. Spudded in Sunshine Ranch overlying Mint Canyon; bottomed in gray Mint Can- yon (?) shale, 45° dips Spudded in anticline in Mint Canyon fm.; bottom in **U. Mio." Spudded in Mint Canyon fm.. Spudded in Repetto (?) ; Mint Canyon to bottom; sh & Is. to 6080, eg to bottom Spudded in Mint Canyon fm.. Mint Canyon to bottom Gas shows at 2160. Spudded in Mint Canyon fm.. Top brown ah. 1476; non- marine Mint Canyon 0-1720 Non-marine Mint Canyon "sh" 0-3244 Mint Canyon fm Spudded in Saugus or Upper Pico (?) in San Gabriel fault zone; bottomed in "base- ment." Bottomed in "granite".. Bottomed in "Pico (?)"_ Bottomed in "Pico" Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned Abandoned No records I'lriHi San Fernando Quadrangle — Oakeshott 135 Lint of uelli drilled outside areas of production ( Plncerita oil field, Whitney Canyon area, and Schist area) in San Fernando quadrangle to April J, 19.53. — Continued Map no. Operator Well S-T-R Year completed or abandoned Depth (feet) Geology Production Status loe Barton Transportation Co. & Assoc. Buick Oil Co Brown 1 Well No. 1 ... Well No. 2... Newhall 1 T.I. & T. 1... T.I. & T. 1... Stetson-Som- brero 1 18JN-15W 18-3N-15W 18-3N-15W 19-3N 15W 19-3N-15W 30-3N-15W 21-3N-15W 26-3N-14W 22-3N-14W 32-3N-15W 6-2N-15W 5.2N-15W 4-2N-15W 4-2N-15W 19-2N-15W 15-2N-I5W 11-2N-15W 36-3N-15W 36-3N-15W 1-2N-15W 1.2N-15W 1-2N-15W 1.2N-15W 6-2N-14W 6-2N-14W 6-2N-14W 1950 1918 1918-19 1899-1900 1944 1942 1950 1902 pre-1925 pre-1925 1949 pre-1925 1929 1928 1950 1927 9 pre-1925 1951 1942 1951 old well pre-1925 1940 1952 1951 TD TD TD TD TD TD TD TD TD TD TD TD TD TD TD Pgd TD TD TD TD TD TD TD TD TD TD 755 1126 1485 700 8207 8035 12027 420 1874 1953 9614 1421 5687 4953 9739 9450 5938 2700 1646 3470 3782 4580 ? 2880 4216 5000 2988 Bottomed in ss and sh 110 Some tar and oil ehowinps re- ported; excessive water 111 Buick OU Co 112 Standard Oil Co Water; running sd and gravel in bottom Continental sediments 0-8207 (?) Spudded in Saugus; base Sau- gus 2050; base Sunshire Ranch 4200; top Lower Pico silts 4850; top Repetto (?) 7280; bottom in basal Pliocene Non-marine sediments (to bottom?) 113 Richfield Oil Corp Barnsdall Oil Co. (Sunray) Sunray Oil Co 114 115 116 117 Russian Oil Co No. 1. No. 1 Panorama No. 1 Mission 2 Mission 1 Woo 1 University 1 . , No. 1. No. 1 Lloyd 1. Lopez-Lundy 1 Reeves 1 Crafton (Krof- ton?) No. 1. Maynier- Parry 1 Bartholomaus 74-6 Bartholomaus Canyon- Bush Bar 1 118 San Fernando Oil & Gas Co. Universal Consolidated OUCo. Mission Hills Oil Co Shell Oil Co Bottomed in Modelo (?) 119 Repetto 5500 Miocene (?) 7740-9614 Abandoned 120 121 122 Shell Oil Co 123 124 Standard Oil Co Standard Oil Co Pacoima Petroleum & He- lium Gas Corp. Ltd. D. W. Griffith Top altered basalt 8694; middle Mio. 8819; bottomed in Topanga fm. Bottomed in cherty shale On test of interval 9330-9450 open 1 hr. 20 min. recov, 743' net. all watery drilling fluid. Abandoned Abandoned 125 126 127 128 Terminal Drilling Co Casa Grande Oil Co E L. Doheney Streaks ot gray ss and sh with dips of 70° at 2500-2520; gray ss 3450-3470. Ran J.F.T. 2550-2653; recov. 296' oily g£is-cut mud with spots of oil. Abandoned 129 Spudded in basal Repetto eg; Modelo 1290 (?) to bottom. 5-ft. oil sd 1170-1230. Steep Ndips. Mohnian 1794-1813. 130 Locally reported to have pro- duced heavy oil many years ago. 131 Geo. G. Parry Bottomed in Modelo .. . _ Abandoned 132 Bottomed in Miocene (?) Abandoned 133 Bell Petroleum Co Bell Petroleum Co Spudded in Modelo (upper Mohnian); lower Mohnian 2340; Luisian 3340. Spudded in basal Repetto eg. Modelo sh at 900; Modelo to bottom. Top oil sand 1600, cored oil sand 2440 to 2510. Abandoned 134 On boiling test made 5-6 B/D IP gravity oil. Too heavy and viscous to produce, low gas pressure Abandoned 136 California Division of Mines List of iielh drilled outside areas of production (Placerita oil field. Whitney Canyon area, and tlii'() in. 4.'^; liliicl; sfnictiircs in. 4S ; charnookitc from. L'il ; litanit'crons niaKni'lito in. 4."> Agna Diiko Canyon. I'J. 47. (10. 01. 62. «;',. 07. 'X,. !)0. 100. 101 : photo sliowin;; Vasiinez formation in, .">!) Ai,'ua Ilnke fault. G6. 07. 00. D" Alder. IS. 1!) Aider Creek, contact in. 21 Alfileria, 1!) Aliso Canyon, anortliosite in. .32 Allanite, 110 Alluvium. ,S7 : as soil. IS; ground water in. 17 Ahius rhomhifolUi. IS Alpine Station. ll.S Altadena. 92 Alumina, fmm anortliosite. 11:? Aluminum, from anortliosite, 10(? American Borax Company. Ill American Graphite Company. 112 Amphibolite. .38. 40. 47 Andesite. in Topanga form.ation. 04: in Vascpiez formation. ."i!l. (iO Anseles Forest Highway. .SO. 4:',. 40. 48. .-.4. .">lnte in, 112: inclusions in. 48; origin of. 4S ; |ilioto showing. 29, 31, 35. 36. 37. .38. .39, 44, 40, 47. 48. .",4. 56. 05. 07. 98; source of alumina. 113; source of titanium, 100, 1111; talm- lation of deposits, 12S ; uranium and thorium in, 110 Anorthosite-gahhro group, 19, 21, 24, 29-52. .56. 02. 103. 100; age of, 48-49 ; photo showing. .36. 3S Antarctica, charnocUite from. 29 Antimony. 108, 109 Apatite, 110 Apex claim, mica, 113 Aplite, 46, .54, 56-57 Arctic, charnockite from. 29 Aictostnpln/Ios uliiiira, 1.8 Arikareean vertebrate fauna. 62. 63 Arkose, 50; in Repetto formation. 77; in Topanga formation, (>:'.. («4 Arrastre Canyon. 97, 100; anorthosite in, 32; intrusive rocks in, 40 Arteinesia ratifoniica, 18 Asbesto.s, 110 ; tabulation of deposits, 128 Asphalt Products Company, 116 Atkin.son Construction Company, Guy F., 115 Augen gneiss, 55 Australia, charnockite from, 29 Avena, 19 B Badlands, 67 Barstovian fauna, 69 Basalt, 77; in Topanga formation, 63, 04, 70; in Vasquez forma- tion. 59, 60, 61 Baughman dolomite deposit, 116 Bear Canyon, 12, 66, 86. 105, 110; gabbro-norite rocks in, 35; gold in, 109; Mendenhall gneiss in, 21; Mint Canyon formation in. 66; photo of, 15, 21 ; photo showing gabbro-norite in. 35 Bear Canyon fault. 97 Bee Canyon, 96 Beryl, 110 Big Pine fault, 89 Big Tnjunga Canyon, 12. 15, 64, 75, 77, 84, 91 Big Tujunga Dam. 89 Big Tujunga River, 15. 88, 89. 105. 115; runoff, 16; sand and gravel from, 117, 118 Big Tujunga Valley, 102 Big Tujunga Wash, sand and gravel in, 117 Biotite, 113 Biotite granndiorile, 77 Bituminous sandstone. 111 Blue Cloud chincliilla dust deixisit, 118-119 Borates, 61, 104, 107. 111112; production of. 106: tabulation of deposits. 128 P.oron. 112 l!oU(nicl Canycui. 12, 62, 87, 89. 9G, 105; chinchilla dust from. 118, 119; folding in. 101 ; gold in. 108. 109; .Mint Canyon formation in. 07. OS, 71 ; Modelo formation in, 65. 68, 70. 71 ; pholo show- ing rocks in. .50; Saugus formation in. 70. 71. 84. .S5 ; ^■as(|Ul•z fanglonicrate in. photo showing. 00. 62 P.owen. Oliver E.. .Ir.. 11 ; data from. 42 I'.ieccia. in Jlint Canyon formation. 66. tis ; in Pacoima formation. .S6 ; in Topanga formation. 64; in Vas(piez formation. 60. 61, 62; photo showing. 60 I'.reccialed migmatite. photetto formation, photo showing, 78; in Saugus formation. S4 ; in Saugus formation, photo showing. 85 ; in Sunshine Ranch member. ,82 ; in Tick Canyon formation, 62, 63 ; in Tojianga formation, 6.3, 64; in Vasquez formation, .59, 60, 61; in Vasquez formation, photo showing, 60 Copper, lOS, 109 Coquina reef, in Sunshine Ranch formation, 82 ( 141 ) 142 California Division of Mines fBull. 172 Cottoinvoixl, IS, 19 Cretacpinis. mineral deposits of the, 107; mountains of the, 103; orogeny dnrinK the, HI ; roolis of tlie, 21, 31, 45, 4fi, 47, 50, 51. 52. .".H. 54. 55, .->«, 57, 58. .5<.t, 01, !«, 06, 100, W.i, 108, 109, 112, 11.5; rocks of the, photo showing, 54, S.S, 88, 91, 96; see also liower Cretaceous, I'pper (^retnceous Crippeii, liichnnl A., .Jr., 11 Cru.^hed rock, tabulation of plants, 128 Crushed stone. 107-108 DngKer Flat, 24, 89, 105, 109, 110; photo showing, 30; titanomag- netite rock at, 39 Pagcer Flat Can.von, photo .showing rocks in, 48; titanomagnetite rocks in, 40 Daggett. Ill Davenport Road, 61 De Oro fault, 93 Death Valley, borates in. 111 Delmontian stage, 20, 57, 78, 104 DeMille fault, 93; photo showing, 91 Diablo Range, tyi)e locality of Domengine formation, 58 Diastrophism, Tertiary -Quaternary, 45 Diatomaceous shale, 102, 107, 114; in Pico formation, 74; in Modelo formation, 69, 70, 71 ; in Modelo formation, photo show- ing, 69, 70, 71 ; photo showing, 102 Diatomite, 114; in Repetto formation, 7.5 Differential thermal analysis of anorthosite, 33, .34, 35 Dikes, anorthosite, 49; granitic, photo showing, .56; in anorthosite. 35, 40, 46, 47 ; in diorite, 54 ; in gabbro-norite, 40 ; in Menden- hall gneiss, 21 ; in Paeoima Can.von, 39 ; pegmatite, 57 Dillon fault. 91 Diorite, 21, 29, 37, 44, 51. .53; photo showing, .38; see also Gabbro- diorite, hornblende diorite Diorite gneiss, 19, 21, 50, 51, 52-53, .55, 77. 92, 103; photo showing. 52, 92 Diorite gneiss migmatites, 57 Displacement, fnmi faulting, 20 Dolomite, 107, 115-116; in Placerita formation, 19, 50, 51; tabula- tion of deposits, 1.32 Domengine formation, 20, 49, 57, 58-59, 62, 77, 92, 94, 121 ; oil in, 111 Domengine Ranch, type locality for Domengine formation, .58 Domengine stage, 20, .57, 59, 74, 78, 104 Dorothy Canyon, 47, 100 (hi Pont de Nemours & Company, E. I.. 110 Duluth. analysis of titaniferous ores from, 41 Dura Portland-Pozzolan cement, 11.3 Dutch r.ouie Camp, 109, 110 Dutch Louis Camp, 24, .39 East Africa, charnockite from. 29 East (Jraceful mine. 112 Ebey Canyon, 93 Economic geology of San Fernando fpiadrangle. 105-122, 127-1.39; table summarizing. 107 Edison truck trail, anorthosite on, 32 El Segundo, 110 ?^lizHl>etb Lake quadrangle, 53, .5.5; Esrondido form:ition in, 59; \'as(juez formation in, 62 Elkhorn fault. 87. 96, 100 Elkhorn Ixidge. 62, 96 Ellesmere Land, charnockite from, 29 Elsmere area, 119; petroleum in, 121 ; wells drilled in, 138, 1.39 Elsmere Canyon, 75, 78, 81, 94, 104. 120; fauna of. 78; oil in. Ill ; rocks in 20, .57. .58. 59, 74 ; unconformity exposed in, 121 Elsmere member. 20. 57, .59, 71, 74, 75, 77. 78, si, 92, 93, 94, 101, 110, 111, 121 ; photo showing. 77, 86, 92 Elsmere oil field. .58, .59 Enderby l6, 97, 114- 115; photo showiiiB, 52, 96; tabulation of deposits, 1,'itl ; s»'c also (Jranitic rocks Granitic rocks. 19, 21, 45, 50, 51, 52, 5.S, .^4, 55, 56, 62, 63, 64, 66, 67, 86, 93, 96, 102, 103, 107, 108, 109, 110; photo showinR, 65, 8.'< • see also (iranite. Granodiorite. Quartz monzonite Graiio.liorite. 19. 21, 24, 46. 51, 53, 54-.56. 64. 71. 77. 88, 91, 93, 94, 102, 103, 122 ; photo of, 12, 15, 54, 88, 91 ; soil derived from, 18; source of Rold, 108; see also Granitic rocks, Ix)we granodio- rate Granulite, 21, 24-25, 28, 29, 50 ^ sketch of, 25 Grapevine Canyon. 12. 77. 93; oil in, 111 (irai>evine fault, 92, 93; photo showing, 92 (Jrnphite, 107, 109, 112; in Placerita formation, 51; photo of mill- site, 15 ; tabulation of deposits, 130 (Jraphite schist, photo showing, 51 Gravel, 89, 117-118; in Mint Canyon formation, photo showing. (57 ; in Pacoima formation, photo showing, 86 ; in Saugus forma- tion, 84, 85 ; in Sunshine Ranch member, 82 ; photo showing, 86, 88 Graywacke, 50 Great Basin, Miocene flora of the, 68 Green Ranch fault, 96 Green Verdugo Reservoir, 64. 70. 71, 122 Greenland, charnockite from, 29 Greenschist, 50 Groundwater, 17 Gypsum, 61, 104, 107, 112-113; in Repetto formation, 77; tabula- tion of deposits, 130 H Hackel, Otto, 11 Hansen Dam, 15, 17, 70, 89, 117; photo showing, 114, 115; rock used in, 55 Hansen Dam quarry, 55, 115 Hansen Flood Control Basin, 102 Haskins dolomite deposit, 115 Hemingfordian vertebrate fauna, 63. 64 Herdsman, W. H., analyses of anorthosite by, 32 Herreres Ranch, 93, 94 Hertlein. Leo. 11 Highway anticline, 91. 101 Hill, Mary [R.], photo by, 1.5, 31, 35, 43, 44, 47, 50, 51, 59, 102, 11.5. 117. 118 Hilltop lime deposit. 115 Historical geology, San Fernando quadrangle, 103-105 Honby, 75. 78, m Hornblende diorite, 53-54, 62, 97, 103 Hornblendite, 53 Hornfels, in Placerita formation, 51 Horse tooth. 83. 85 Hospital fault. 86, 92, 93, 101, 122 ; photo showing, 92 Howlite, 111, 112 Humphreys station, 8.3 Humphreys syncline, 75, 77, 78, 101, 104 ; photo showing, 101 I Ideal Cement Company, 113 Ilmenite, 106, 107 Ilmenite-magnetite, tabulation of deposits, 130-131 ; used as roofing granules, 116 ; see also Titanium, Titaniferous magnetite India, charnockite in, 28, 29 Indian Creek, 12 ; pegmatite on, 56 Indian Creek truck trail, 113 Indicator claims, 108 Insecticide, shale used as carrier for, 114, 118 Intrusive rocks, 21-57 Iron, 109 Iron Blossom mine, 110 Iron Canyon, 97 ; photo showing rocks in, 48 Iron Jlountain, 97 ; titanomagnetite rocks from, 40, 41 Ivory Coast, charnockite from, 29 Jacalitos formation, 78 Jahns, Richard H., 11 Jenkins, Olaf P., 11 Jennings, Charles \V., 11 ; photo by, frontispiece, 87, 88 Jointing, in anorthosite, photo showing, 43; in Mendenhall gneiss, 24 Juanita area. 119, 120 Juniper, IS, 19 •luniperua cnlifoniica, 18 Jurassic, mountains of the, 103; rocks of the, .50, 51, 52, 53, 54, 55, 56, 112 ; see also I'pper Jurassic Kagel Canyon, 12, 83, 87. 88, 93 ; faulting in, 92 ; graphite deposits in, 112 ; hornblendite in, 53 Kagel formation, 88 Kashmere fault. .54. 96 Kasper, John, 109 Katz, Dr. Leon, 118 Katz diatomaceous shale deposit, 114 Kiln, limestone, 52 Kraft-York area, 119, 120 Kernite, 112 Klippe, 92, 93 Kreyehagen shale, 58 La Crescenta, 17 Lamprophyre, 46, 47 Lamprophyre dike, near Monte Cristo mine, 40 Landslides, 88 Lang, 66, 67, 89, 96 Lang Borax mine, 106, 112 Lang gypsum deposits, 112 Lang quadrangle, anorthosite in, 32 ; photo showing anorthosite from, 31 Lang Station, 31, 41, 110, 111, 113, 116, 118 Lapland, analysis of rocks from, 41 Laramie Range, anorthosite from, 113 Las Llajas Canyon, Llajas formation in, 58 Laurel Canyon, lead-silver-zinc in, 109 Lead, 109; tabulation of deposits, 131 Lead-alpha measurements, age of anorthosite determined by, 21, 48 Lepidospnrtiim squamatum, 18 Leucogranite, 56 Lime, from Pacoima Canyon deposits, 116 Limekiln Canyon, 93, 116; dolomitic limestone in, 116; granite iu, 55 Limerock Canyon, 51, 53, 91 ; diorite gneiss in, 52, 57 ; dolomitic limestone, 115; graphite in, 112; photo of, 15; Placerita forma- tion in, .50, 51 ; uranium reported from, 110 Limestone, fossils in, 52 ; in Modelo formation, 71 ; in Placerita formation, 19, 50, 51, 103; in Sunshine Ranch member, 82; tabulation of deposits, 132 Lit-par-lit injection, 36 Little Escondido fault, 96, 97 Little Nugget Placers, 109 Little Tujunga anticline, 102, 103 Little Tujunga area, 93 ; diatomite in. 114 ; folding in, 103 Little Tujunga Canyon, 12, 15, 50, .55. 64. 69. 71, 76, 83, 84, 87, 88, 93, 102, 103, 105, 110, 112, 115, 122; gold in, 108; mica plant in, 113; Modelo section in, 70; Repetto formation in, 75 Little Tujunga Creek, 88, 115 ; runoff of, 16 Little Tujunga River, 105 Little Tujunga Road, 16, 52, 85, 88, 91, 93 ; gabbro-norite rocks on. 35; Mendenhall gneiss on, 21; photo showing, 21, 24; photo showing migmatitc on, 52 ; photo showing gabbro-norite on, 35 Little Tujunga syncline, 21, 69, 75, 76, 82, S3, 86, 100, 101, 102, 104, 105, 122 ; Saugus formation in, 85 Live Oak mine, 110 ; ilmenite-magnetite from, 116 Llajas formation, ,58. .59. 62 Loam. 18 Lone Tree Canyon, 97. 100 ; anorthosite in. ,32 Lonetree fault. 100 Long. 95 Loop Canyon. 86. 101 Lopez, Francisco, discoverer of gold, 108 Lopez Canyon, 12, 69, 87, 88, 93, 102. 105, 111 ; Repetto formatu.n in 75, 76; Saugus formation in, 83 Lopez fault, 52, 88, 92, 93, 102, 103, 122 ; photo showing, 92 Lopez formation, 88 Los Angeles, 74 144 California Division of Mines [Bull. 172 Los AiiKt'les Iwsiii, 2U. 74, SO, 122; Rppclto foi-m:iti()ii in. 7."> ; rocUs of the, «l IxKS Angeles DciLiitment of Wafer and r<>\vci-. photo from. (ii). 711, 82. S!. (>•'. 74. 104. 122 M M.icArthur & Son sand and gravel pit. 118 MaiArthnr Head.v-niix plant, photo showing. 117 .Magic Monntain, 12. :51, 4S. 46. ."7 ; rainfall on. Ki Magic Monntain fault. 4."i. ."7. '.17 Magnetite. 10(> Mang(dil. Ilerniaii. 110 Manzanita. IS Map. showing anorthosite-gahliro rocUs in San Fernan, 28; sketch of thin-section of, 2.~> ; sketch showing contact with gahhro-norite. 40 Memlenhall Teak, 12. 24; photo of. 12. 01 ; type locality of Menilen- hall gni'iss. 21 Merrick Canyon, 7."> Mesozoic. rocks of the. .".0, ICS Metadiorite, 20, ."i2, .".:!, lO.S Metagahhro. 20. .'il, :i7, 41, 44; photo showing, .37, 46, 47 Metainoriihic rocks. 21 -."17 ; see also Gneiss, Schist Jletamirite. 20. 44 Metapyroxenite. 20. .'il. :«, 40. 41, 42, 47, 100; photo showing, 3(!, 46 Mica, li:!; tribulation of deposits. i:'.2 Microcline hodies, in .-inortlKisite. 7>~ Migmatite. 5(1. ."i2. .")o, ."7 ; ph(}to showing, .')2 Mill Creek, 46; jihoto of schist from North Fork of, 4;i Mineral deposits, talinlation of, 127-loO Mineral Increment Company, 110 Mineral production, tahle showing, 106 Mint Can.von, 12. 6:!, 66, 67, S7, SO. 06. 100. 101 ; granite in, 11.".; gypsnin in, 112; photo of, 13, 14; rocks in, 50, 54; temperature. 16; type locality of Mint Canyon fornnition, 65. (!S Mint Canyon hasin. 6S Mint Canvon fanlt. 60. 61. 06, 112, 113 Mint Canyon formation, 11, It), 20. 21. .57. 60. 61. 62, 63, 6.5-60, 70. 71. 74. S3. S5. SS. 01. 02, 05. 06, 07. 100. 104. 107, IIS. 110. 122; flora of the, 104; fidding of. 101 ; photo of. 13, 14, 65, 66, 67, 68, 78, 87, 05. 101 ; vegetation on. 10 .Mint Canyon highw:iy. 16 Miocene, diatomite in rocks of the, 114; flora of the, 68; fossils of the, (>2, (i4, 60, 71, 74, 78; pelndenin in rocks of the, 122; rocks of the, 20, 21, 57, 6.3, 64. 65, 68, 60, 75, 83, 87, 03, 04, 05, 07, 100, 101. 104. 107, 115. 117. 118, no, 122; rocks of the, jihoto showing, 66. 67. 04. 101. 102 Mission Hills. 12. 15, 70, 71, 86. 100, 102, 104; diatomite in, 114; fanning in, 01 ; residn.al soil in. 18; Sunshine Ranch memher in, 82 Missicni Hills .inticline, 70. 04. 102 Mission Hills thrnst fanlt. 04 Mississippian. rocks of the. 10, .52, 103 .Mitchell granite (piarry, 115 Modelo Canyon, type locality of .Modelo formation. liO .Mosite by, 32, 34. .35 Xora-Kvelyn verniiculite claims. 113 Xorite, 28. 20, .37. 38, 4:'., 44, 40, 106; see al.so (Jabbro-norit.' rocks Xorman, L. A., 11 X'orth Fork of I'acoima Canyon, graphite in. 112 N'orway. charnockite from, 20 O O.ak. 18. 10 Oak of the (Jolden Dream. 108 Oak Spring Can.\on. 07; golil in. 100 Oat, 10 Oil, .50, 78, 107, 111 ; in I'ico fornnition. SI ; in Repetto fornnition. 77; see also Fetroleuni Oil wells, beds penetrated by, 20, 57, .58, .50, 64, 65, 70 Oligocene, borate in rocks of the. 111; faulting during the. 104; gypsum in rocks of the. 112; rocks of the. 20. 54. .58. 100, 107, 116; photo showing rocks of the, .50. 60. 62. 05. 0(i Olive View. 15. 75, 78, ,S6, 02, 110 ( )liver Canyon, 87 Opal, 112; tabulation of deposits, 12S Ore Hills claims, 108, 100 Orocopia Mountains, anorthosite-gabbro rocks in. 20 Orogenies. 20. 21, 45, 86, 100. 105 Orwig fault. 110. 12(1 P I'acitic Coast Itorax Company, 112 I'acitica Reach, San Diego formation at, 75 I'acoima, 15, 64 I'acoima Canyon, 48, 53, 86, 88, 80, 03, 105, 112; dolomitic lime- stone deiiosits in, 116; fossils in, 52; gabbro pegmatites in, 4.3, 44; gahbroic rocks in. 47; gold in. lOS, 100; lead-silver-zinc in, 100; limestone kiln in, 52; Mendenhall gneiss in, 21, 24, .30; metagahhro in, 41 : metapyroxenite in, 41 ; mineral deposits of, 108; photo showing dikes in North Fork of, .35; photo showing rocks in, 36, 47; photo showing rocks in Xorth Fork of, 36; I'hotomicrograph of gabbro from, 43; rocks in, 48; San Cabriel fanlt in, 01 ; sketch showing contact in, 40; titanomagnetite rock in, 30, 40, 42, 110; tyi>e locality of Pacoima formation, 85 1!»58| Sax Fernando Qi'adrangi.e — Oakeshott 145 Paniiniii ("reck. 12. SS, !)1 ; runoff, IB; sanil niul snivp] fruni, 117 r.Ki>iiii.i Diim. 12. r>:!. s.-,. Si), ns rjicoiiiiii I);nii !;r:iv<'I iiit. ^'\S V:\co\mn fniilt. !I7. 1(12 PaooiiiKi f..nn.-iti..ii, 2(1. 57. 7.-.. «.■?. S5-S7. SS, ;. 12. niilp ill, 114; Mii- (Iflo forma tiiiii in, (iO, 70. 71; residual soil in, IS; Topanea formation in. K!. 64. («!1 I'acoima Hills fault. 114 rafoinni Mills ^-rauitf ([uarry. 114-11") I'aniini.-i iinadrangle. (i4 I'acoima Koscrvoir. -".X l'a<'oima JJivcr. I'l Pacoima Wasli. 12. 7."). S4. S(!. SS. !»7. 102; -ravel in, SO, US P,ileocpnp, fossils of the, (52: rocks of the, ri.l, ,">(>, ,"i7. .">S. ."lO, !)]. !I3. 104. 120: seas of the. 20. lO.I. 104; rocks of the, 10, ',2. .>{, ,"., lOS, 107. 112. ll.T Pnrafrenesis of minerals. ;iuiirtliiisite-gahhro complex. 44-45 Parker Mountain. ."4, (>1, (io. 07; type locality for Parker (pmrtz fliorite. .">;? Parker quartz diorite. o.^. .54 Pask, .losejjh A., differentia! thermal analyses of anorthosite hy, :«, 34 Pegmatites, 40, 4.H-44, 40. 40, ,52, 54, o6-.57 ; mica in, 11,S: minerals of, 109; Pre-Camhrinn, 107 Pelona fault, 55, 02, 00 ; photo showing, 06 Pelona schist, 10, 21, 40-50, ,55, .56, 62, 66, 67, 6S, 84, 92, 96, 100, 103 ; photo slniwing, .50 Peninsular Ranges, rocks of the. 20. .55. 56. 103 I'etroleum, 110-122; in Pico formation, 7S ; in Repetto formation, 75 ; iJi'oduction of, 106 ; see also Oil Phase-rule diagram, for plagiochuses, 34 Photomicrograph, of hornhleude titanomagnetite gahhro. 43; of titanomagnetite (divine galihro. 42; of antiperthitic feldsjiar. 25. 28 Pico Oanvon. tvpe locality of Pico formation. 74 Pico formation, 20. 57, .59, 74, 75, 77, 78-S3, S5. 91. 94. 101. 102. 104. 107, 111, 119, 120, 121, 122; fossil localitie.s in. SI ; oil iu, 111 ; photo showing, 82, 86, 94 Pioneer Division Flintkote Company, 119 Placerita area, folding in the, 101 Placerita Canyon, 75, 77, SI. 88. 101. 104; gold in. 108; petroleum in. 107. 121 ; photo of. 13 ; Pico formation in, 81 ; San Gahriel fault in, 91 ; Saugus formation in, 84 ; type locality of Placerit,i fornmtion, 50 Placerita fault. 78, 81, 91, 108, 121 Placerita formation [series], 19, 49, 50-52, 53, .55, ,86, 92, 103, 10.8. 115; ashestos in. 110; economic mineral deposits in. 107; graphite in. 112; photo showing. 92; soil derived from, 18; uranium reported in, 110 Placerita oil field, .58, .59, 62, 81. 82. S3. 94. 101, 106. 107, 119-120, 121, 122 Placerita schist area, 119 Plagiiiclases, phase-rule diagram for. 34 PUifiiniis rnrpiiiosil. 18 Pleistocene. fauItiufT during the. 94 ; fos.sils of the. 85 ; orogeny during the. 21. 45. SO. KHI. 104, 105; rivers of the, 105; rocks of the 20, 57, 74-75, S3, 87, SS. 93. 97. 100. 101. 102; rocks of the. photo showing. 85. 86. 91. 92. 03; San Gabriel Mountains during the. 105 Pliocene, faulting during the. 20. 92. 94 ; fauna of the. 120 ; fossils of the. 69. 71. 78. 81. 83; oil in rooks of the. Ill ; rivers of the, 105 ; rocks of the, 20, .57. 69. 74-75. 78, 83, 91, 93, 94, 101, 105, 107, 120, 121. 122; rocks of the. photo showing, 76, 78, 82, 85. 86, 92, 94, 101 ; seas of the, 77, 104 Plum Canvon, 87, 100, 105 Pole Canyon. 12. 66, 97, 110, 116; gold in. 109 Pole Canyon fault. 35, 45, 46, .55, 60, 95, 97 ; photo showing, 97 PopitlitK fre)iioitfii, 18 Portland cement, anorthosite used in, 113 Poultry grits, ,inorthosite used as, 106, 114; limestone and dolo- mite used as, 11.5 Pozzolanic concrete, anorthosite used in, 106 I"re-Camhrian, 91; anorthosite of the, 4.8; charnockite in rocks of the, 29; rocks of the, 19, 20, 21-29, 39, 45, 46, 49, 50, 51, 52, 53, 56, .57, 92, 95, 103, 106, 107, lOS, 109, 113; rooks of the, photo showing, 24, .54, 91 Pre-Cretaceous, faulting during the, 24; rocks of the, 21, 31, 55, 89 ; rocks of the, photo showing, 92 l're-,Turassio, rocks of the, .55 I'reP.ileocene. rocks of the, .5(! Pre-Terliary, rooks of the, .59 Proliertite. Ill Pst'udotttUf/ii liiiirrofdrpa, 18 Puckett jiesa, 65, 67, 68, 87 Puente shale, 74 Pvrite, lOS Pyroxeuite. 28, 4S. 49, 106. 109 ; photo showing. .36. .39. 46, 47 Quartz hodies, in anorthosite, 57 Quartz diorite, 51, .53. 54. ,55, 56, 61, 67 Quartz diorite gneiss, source of gold, lO.S ; photo showing, ,52, 77 Quart/, nionzonite, 19, 46, 51, .55. 62, 103; see also Granitic rocks (iuartzite, 19, .52, 84; in Placerita formation, 51 ; in Vasipiez for mation, 62 Quaternary, climate during the, 10,5; diastrophism during the, 45; erosion during the, 105; faulting during the, 20, 21, 45, 92, 96; orogeny during the, 31 ; rocks of the, 20, 46, 85, .S6, 94, 97, 101, 105, 119, 122; rocks of the, photo showing, 80, 87, 88 Quaternary and Tertiary sedimentary and volcanic rooks, 57-S9 Quaternary deposits, .sand and gravel from, 117 Quaternary gravel, photo showing, 93, 95 Quaternary terrace deposits, 86, 87, 92, 93; ground watei- in. 17: photo of. 13: soil on. 18 Qiierrux affiifolia. Q. chrynolepis, Q. diimonn. 18 Rabhit Canyon, 97 Radioactive minerals, 110 Rand schist, 50 Ravenna quadrangle, anorthosite in, 32 : Vasquez series in, 59, 00 Recent, alluvial hasins of the, 105 ; rocks of the, 87, 108 Recent alluvium, 87, 88-89, 105; gold in, 108; ilmenite-magnetite from, 116 Recent deposits, under Hansen Dam, 115 Red beds, photo showing, 96 Repetto formation. 20. 57. 69. 70, 71, 74, 75-77, 81, 83, 84, 85, 91, 92, 93, 94, 107, 111, 119, 121, 122; folding of the, 101, 102; fossil localities of the, table showing, 79-81 ; oil in the. 111 ; photo showing, 75, 76, 77, 78, 85, 86, 92, 94, 101 Repetto Hills, type locality of Repetto formation, 74 Reservoir anticline, 82 Reynier Canyon. 68. 70. 92. 101. 110; Modelo formation in, 71; San Gabriel fault in, 89 Reynier Ranch tuff deposit, 119 Rhus Inuriiia, IS Rice. Salem ,1., 11, 110 Ripgut, 19 Rock Creek, 103 Rock Creek quadrangle, Martinez formation in, 58 Rock products, 113-114 ; production of, 106 Roofing granules, 61, 110, 116-117; tabulation of deposits used for. 132 Roscoe, 110 Rowley fault, 75, 77, 92, 04 Rubio Canyon, 52 Rubio diorite, 52 Runoff, table .showing, 16 Rnss Siding, .32, 110, 113 Sage, 18 .S"n?tj-. 18 Salton Sea, 29 Salvia apiana. l^. melHfera, 18 San Andreas fault, 45, 49, 89. 96, 103 San Andreas fault zone, Martinez formation in, ,5,8 San Bernardino Mountains, Furnace limestone in, 19; Paleozoic rocks in, 52 San Buena Ventura Mission, gold placers of, 108 San Diego County, pegmatites in, ,56 San Diego fauna, 78, 120 San Diego formation, 75 San Fernando, 15, 110, 118; rainfall, 16 San Fernando basin, 20, 21, .57, 89, 100, 105; folding in, 101-103 San Fernando Dam, .86 San Fernando dolomitic limestone deposits, 116 San Fernando Mission, gold placers of, 108 146 California Division of Mines [Bull. 172 San Fei-nniulo Reservoir, 15, 20, 63, 69, 70, 71, 74, IV,, 76, 78, 81, K% 8."., 86, 04. 102, 10."), 114, 117, 122; anticline at, photo show- ing, 102; S;iiiKiis formation at, 84 .San Fernando Valley, 11, 12. In, 19, 69, 71, 74, 10.'); alluvial (le- [losit.s in, 84, 88; explorator.v holes drilled in, 121-122; .xand and gravel in, 117; terraces in, 87 San Franci.sco Bay, ."i7 San Gahriel anorthosite-gabbro comples, 19, 29-ij2 San Gabriel fault. 12. 19, 20, 21, 24, 31, 45. 46, .50, 52, .53, .54, .56, 57, .58. .59. 05. C!!, 71, 75, 77, 78, 81, 82, 83, 84, 85, 86, 88, 89, 91-92, 93, 94, 100. 101, 103, 104, 105, 111, 112. 114, 115, 119, 120, 121. 122; photo showing, frontispiece, 14, 91 San (iabriel fault, ancestral, 10.'! .San (iabriel fault zone, folding in the, 101 San CJabriel formation, 21, .52, 55 San Gabriel massif, 20, 21, 100 San (iabriel Mountain block, 46 San (iabriel Mountains, 11, 12, 15, 16, 17, 20, 33, .34, 52, 57, .58. 59. 61, 65, 70, 77, 84, 85, 87, .88, 94, 95, 103. 104, 105, 117. 118, 120, 122; ancestral, 20, 103; anorthosite in, 31; anorthosite- galibro rocks in, 20. 47, 48, 49; aplite in, 57; asbestos in. 110; diatomite in, 114; faulting in, 97. 100; gabbroic rocks in. 43; granite in. .56, 114; granodiorite in. .5.5; hydrothernial minerals in, 45; Martinez formation in, .58; metanuirpbisni in. .50; Modelo formation in, 69; oil in, 119; once called Sierra Madre, 92; Pacoima formation in, 8(5; pegmatites in, .56; photo showing. 13, 14, 15, 92 ; Plutonic rocks in, 103 ; Pre-Cambrian history of, 103 ; pre-Tertiary history of, 103; Repetto formation in, 75; residual soil in, 18; source of Repetto formation, 76; titanium in, 110 San Gabriel Mountains geologic province, 89 San Gabriel Pigment Company, 110 San Gabriel River, 89 San .Toa<|uiu Valley, fossils from, 81 .San Pablo formation. 69 Sand, Quaternary, photo showing, 88 Sand and gravel, 88-89, 107, 108, 117-118; tabulation of deposits, 1.33 Sand Canyon, 12, 66, 68, 75, 77, 86, 80, 92, 100, 105, 109, 114. 119; gabbro-norite nx'ks in, 3.5 ; ilmenite-magnetite from, IK) ; mining operations in, 89; Mint Canyon formation in, 68; Modelo forma- tion in, 71 ; rocks in, 48, 66, 70; titanium in, 110; titanomagne- tite rocks in, 42, 43 Sand Canyon fault, 100, 101 Sand Canyon road. ()7 Sandstone. 20, 107; bituminous, 111; in Domengine formation, .59; in Klsniere member, photo showing, 86 ; in Martinez formation, .58, 103; in Mint Canyon formation. 66, 67, 97; in Mint Canyon formation, photo showing, 66, 67 ; in Modelo formation, 69, 70, 71 ; in Modelo formation, photo showing, 94, 102 ; in Pico forma- tion, 74, 78, 81 ; in Pico formation, photo showing, 82, 86, 94 ; in Placerita formation, 51 ; in Repetto formation, 75, 76, 77, 78; in Rrpeffo fr('ro fault, 92, 93 ; photo .showing, 92 .Southern Pacific Company, photo from, 29, .31, 95 Soutliern Pacific Railroad. 67 Southwest Portland Cement Company, 11.3 Spanish gold mine, 108, 109 Spence Air Photo, 13, 14, 114 Sphalerite, 109 Spring Canyon, 6.3, 67, 1(K) Spruce, 18, 19 Stauffer Chemical Company, 111 Sterling Borax Company, 111, 112 Sterling borax mine, 106, 111 Stibnite, 108, 109 Stock, Chester, 11 Strem, C. E. S., chemical analyses of titanomagnetite rocks by, 41 Structural history, Cenozoic era, 89-103 Sulphur Springs, 37, 95 Sumac, 18 1958J San Fernando Quadrangle — Oakeshott 147 Siinliiiid. 1.1. (U, («), 70. 71. 7.'.. 7f>. 78, 102. 101, 117. 118 Snnhinil fault, (i.".. 71. 88. 02. Ki, 04. 102. 10:{ Siiushiiie Rniu'h, type locality nf Sunshino Ranch member, 82 Sun.shine Ranch memhcr, 20. 57, 75, 78. 81. 82, 8.S, 85, 01, 04, 102, 104, 105, 107, 119. 120, 121. 122; foldinK in, 101; oil in. 111; photo sho\yinK, 82 Swall-Fcrrier fault, 120 Sycamore, 18, 10 Syenite, 20, .5;{.54, 60, 61, 62, 02, 96, 97, 100 Sylmar. 15. 92 Sylniar s, 122; in Repetto formation, 81 Tehachapi Mountains, photo showing, 12 Tejon area, lO.f Tejon formation, .57 Tejon quadrangle, >Iartinez formation in. 57, 58, 62 Temblor formation, 69 Terrace deposits. 20. 83. 84, 85. 86, 87-88. 105, 115; photo showing, 87. 91; Pleistocene, 75; see also Pacoima formation. Quaternary terrace deposits Terrace formation, 122 Tertiary, climate of the, 104; diastrophism during the, 4.5; fault- ing during the, 21, 45; orogeny during the, 31; petroleum from rocks of the. 107 ; rocks of the, 20, 46, 47, 50, 52, 95, 103-104, 118, 119. 122 Tertiary and Qnaternar.v sedimentary and yolcanic rocks, 57-89 Tertiary section, San Fernando quadrangle, 122 Texas Canyon, 63, 96 ; Vasquez formation in, 59. 62 ; Vasqnez for- mation in, photo showing, 62 Thompson, Challoner. 109. 110, 116 Thorium, 107, 110 Thorkildsen and Company, Thoma.s. Ill Tick Canyon. 55. 59. 62, 63. 100. 116; borates in. Ill; geologic section in. 61 ; gold in, 108, 109; graphite in, 112; tj'pe locality for Escondido series. .59 Tick Canyon fault, 61, 96, 100, 111 Tick Canyon formation, 20, 57. 59. 61, 62, 64, 65, 67, 68. 69, 92. 96. KKI. 104. Ill; description of the, 63; fauna in, 63; folding of, 101 Titanium. 109-110; see also Titaniferous magnetite Titanium ore, production of, 106 Titaniferous magnetite, 106, 107; misidentified as chromite, 108; see al.so Titanium Titanomagnetite gabbro, 42-43 Titanomagnetite rock, 29, 38-41, 42, 43, 44. 46, 47; photo showing, 39; sketch of thin-section of, 40; sketch showing polished surface of, 38 Tonalite, 28, 55 Toney gold mine, 109 Topanga Canyon, type locality of Topanga formation, 63 Topanga formation, 20, 57, 63-65, 69, 70, 71, 76, 77, 93, 94, 104, 122 ; folding of the. 102 Towsley formation, 74, 78 Trail Canyon, anorthosite in. 32 ; pyroxenite in, 40 Train Canyon quadrangle, metapyroxenite in, 40 Transmission I.ine Fault, 21. 31. 32, 35. .38. 45. 4<>, .56. 92. 97. 10(1 Transverse Ranges, rocks of the, 19, 55, 56, 103 Transverse Ranges province, 52 Tremolite asbestos, 110 Triassic, rocks of the, 51 Tuff, 50, 61, 107, 118-119; in Mint Canyon formation, 67, 68; in Mint Canyon formation, photo showing, 68 ; in Modelo forma- tion, 70 ; in Vasqnez formation, 60 Tujunga, 15, 64, 75, 77, 94, 101, 122 Tujunga Canyon, 89, 93; Modelo shale in, 76; Repetto formation in. 76 Tujunga quadrangle, 19, .38, 39, 40, 41, 46, .53, .54, 56, 97, 100, 109 ; anorthosite in, 33 ; anorthosite-gabbro rocks in, 29, .35 Tujunga Valley, 76, 78, 87, 95, 102; gravel pit in, 118; Recent alluvium in, 88 Tujunga Wash, gravel deposits in. 89; gravel deposits in. photo showing. 118 ; photo showing, 115 Turner dolomitic limestone deposits, 116 Ulexite, 111 I'nconformities, 20. 71, 75 T'. S. Bureau of Mines, tests on anorthosite, 113 r. S. Highway 6, 87 Cniversity of California, differential thermal analvses of anortho- site by, ,33, 34 Fpper Cretaceous, ,57; rocks of the, 49 Fpper .lurassic, rocks of the, 20, 50, 55, 62, 63 Fpper Pico member, 20 Fpper Sonoran life zone, 18-19 Franium, 107, 110 Franothorite, 110 I'topia gold mine, 109 Vail. Karl V., 113 Vnil anorthosite claims, 113 Vacpieros formation, 64, 69 Vasquez Canyon, ,55, 59, 60, 62, 63, 87, 96 ; folding in, 101 ; fossils of, 63 ; gold in, 108 ; Mint Canyon formation in, 67 Vasquez Canyon fault, 63, 96 Vasquez fault, 89 Vasquez formation [series], 20, 53, 54, 57, 59-62, 63, 65, 66, 67, 68 92, 95, 96, 97. 100, 104, 107, 116, 118, 122; borates in. 111; chalcedony and opal in, 112 ; folding of, 101 ; gypsum in, 112 113 ; photo showing, 59, 60, 62, 65, 95, 96 Vasquez Rock, 59, 60, 61, 100; photo showing, 59 Veatchite, 111 Vegetation, 18-19 Ventura Basin, 85, 89, 94, 104, 122; oil in, 119; fossils of the. 63 ; Repetto formation in, 75 ; relation to San Fernando and Soledad basins, 20 ; rocks of the, 20, 46, 57, 59, 62, 69 70 74 77 Verdugo Hills, 94, 114 Verdugo Mountains, 12, 100, 102, 104, 117, 122 ; diatomite in, 114 ; granodiorite in, 69; Modelo formation in, 69, 70, 71; residual soil in, 18 ; source of Repetto formation, 76 ; Topanga forma- tion in, 63, 64 Vermiculite, 113 Vertebrate fauna, in Mint Canyon formation, 66; in Sespe forma- tion, 62 ; in Tick Canyon formation, 62, 63 ; in Topanga forma- tion, 64 Virginia, analysis of nelsonite from, 41 Volcanic ash, 118-119; tabulation of deposits, 133 Volcanic rocks, 20. .50, 57-89 W Walker, Frank E., & Sons, 108 Walker mine, 108 Water, San Fernando quadrangle, 89 ; see also Groundwater Watt fault, 93 White Crystal dolomitic limestone deposits, 116 Whitewater Canyon, 97 Whitney Canyon, 75, 77, 78, 81, 94, 119, 120; Saugus formation, 84, 85 Whitney Canyon area, 104, 119; beds penetrated bv well in, 58, 59 ; petroleum in. 120-121 ; wells drilled in. 137 Whitney Canyon oil field, 58, 94, 111 Whitney fault, .58, 81, 92, 94, 104, 111, 119, 120 Willow, 18 Wilson Canyon, 86 Wilson Can.von truck trail, 86 Wilson diorite, 55 Woodford, A. O., 11 Wragg Ranch dolomitic limestone deposits, 116 Wright, Lauren A., 11 Wyoming, anorthosite from, 113 Yerba Buena trail, contact on, 21 Y.ikut sandstone, 58 Yiircn irhipplei. 18 Zinc, 109 ; tabulation of deposits, 131 Zircon, 110 ; age-dating by, ,55 A 79404 -58 3500 prinled in California state printing officf DIVISION OF MINES STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES Bouir"t Rettrt'oir e'l -J-- — -q34'30' LEGEND SEDIMENTARY AND VOLCANIC ROCKS Qal Terrace deposits (fanglomerate and terrace gravele) UNOONFORMITY Qp Pacoima formation (dark brown breccia and fanglor erate, locally folded) MAJOR UNOONFORMITY Qs SauguB formation (continental light-colored coTiglome- rate and sandstone) LOGAL UNCONFORMITY 3 Sunshine Ranch member (contiTiental a/id brackisk-water greenish sandstone, mudstone, con- glomerate, red beds and thin lime- stone beds (Is) Tpu Upper Pico member (marine sandstone and mudstone, conglomerate; fossiliferoua) Tpl Lower Pico member (marine conglomerate, sandstone, ailtstone, fosailiferous calcareous sandstone) Repetto formation (undifferentiated^ (marine siltstone and -mudstoTie. ark- oae, sandstone and conglomerate) Elsmere member t (marine fossiliferous coarse sand- stone and conglomerate, often pet- roliferous, interbedded sandstone ana silt stone) Tm Modelo formation (marine arlcoae, conglomerate, sand- atone, ailicious and diatomaceous shale) UNOONFORMITY INTRUSIVE AND METAMORPHIC ROCKS Pegmatite (chiefly alkali graniu pegmatites) Granite • (buff to pink; includes some quartz momonite. Pegmatoxd and gneiss- oid facies. Inclusions of older rocks) gd Granodiorite (includes some quartz diorite and quartz momonite; also pink granite) sy Syenite • (dark, red-weathering augite and quarlx-augite syenite. High mpink microperthite) Hornblende diorite • (dark, brown-weathering; high in white andesine, minor pi^ mi- crocUne; probably fades of the syenite) dgfi Diorite gneiss (dark gneisses; includes some biotite schist. Where injected by granodior- ile (cjgn+gd); including Placenta /or»ia(io«rocA;«(dgn+gd-fpl)Hom- blende-rich fi^ies (h) Piacerita formation t (graphite, sillimanHe. biotite schists; quartzite. Limestone, dolomite (pi) Pelona schist * (chlorite and acttnolite schists, quart- zite. Many quartz veinlets) /+gf Anorthosite " imedium to very coarse-grained, largely basic andesine. Anorthosite and granite (sn+gr) Gabbroic and noritic rocks • (altered rocks bordering anorthosite. llmenite-magnetite gabbro (gbm), includes massive ilmenite-magnet- He) T3N i «=^ =£SH '"13 1 '^» : ■^ , *■'■■■■/ ^ WtCTNE^CttJ wofr ARFjE , 3 -^::^ ~ ^ '»' 3 AP^fl. IVv "^ J ^W Base Irom U.S. Geological SiAey 6' 1:24,00 topographic macs. lology surveyed 1933-36, 39-41. - 4&'52 ECONOMIC MAP OF THE SAN FERNANDO QUADRANGLE, CALIFORNIA By Gordon B. Oakeshott SCALE 1^62500 Cnntoui- intoi'vat 2m left. 1 Contours from 1 : 24000 mup. Geology in part after 1. Hilt. 1930 2. Jahns 1940 Elsmere member t (marine fossiliferous coarse aand- stone and conglomerate, often pet- roliferous; interbedded sandstone ana sUtstone) Tm Modelo formation (marine arkose, conglomerate, sand- stone, silicious and diatomaceous shale) UNCONFORMITY Tmc Mint Canyon formation • (continental sandstone and conglom- erate, mudstone, claystone, tuff, lake beds) UNCONFORMITY UJUI i?i Iguj I lU- y Ttc Tick Canyon formation • (continental sandstone and conglom- erate, siltstone, clay stone, lake beds) Tt Ttv Topanga (?) formation t (continental arkose, conglomerate, red and yellow beds. Interbedded andesite and basalt flows (Ttv) UNCONFORMITY Tv 'Tw Vasquez formation * (continental red beds, sandstone and conglomerate, green and yellow sandstone. Interbedded volcanics (Tw) UNCONFORMITY I- g OS Domengine formation t (marine gray togreenish kardcqlcar- eou3 sandstone and conglomerate) an /an /+er Anorthosite • (medium to very coarse-grained largely basTC andesine. Anortkosite and granite (an+gr) 2 ^ Gabbroic and noritic rocks * (altered rocks bordering anortkosite. Ilmenite -magnetite gabbro (gbm), includes massive ilmenite-magnet- ite) pern Mendenhall gneiss, • (blue quartz-plagioclase gneisses with variable amounts of ferromagnesian minerals) Well defined Inferred AUavium and terrace i{ Martinez formation t imarine greenish-black sandstone, dark shale, coarse conglomerate) an 3 anorthosite; as = asbestos; B = borax; co = chalcedony-opal; cr = crushed rock; feldspar-silica (see anorthosite); Au = gold; gr = granite; g = graphite; gyp = gypsum; Ti = Ilmenite- magnetite; Pb. Ag, Zn = lead, silver, zinc; Is = limestone-dolomite; m=: mica; rg = roofing granules; s g = sand and gravel; sh= shale; vermiculite (see mica); va= volcanic ash. Mine Placer X Prospect Well drilled for oil-dry (outside of designated fields and areas) UBRARY UNIVERSITY Or CAUPOmitA UAVIS Well defined Inferred Concealed Anticline S3mcyne Strike and dip Vertical Horizontal Foliation Vertical foliation Conglomerate bed Tuff bed Limestone bed Occurs north of San Gabriel fault Occurs south of San Gabriel fault DIVISION OF MINES STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES (Bou TN-24 ,D J D ^yW^-ETIN 172 PLATE 1 (Red Raver el LEGEND SEDIMENTARY AND VOLCANIC ROCKS t- Qal Terrace deposits (fangiomerate and terrace gravels) UNOONFORMI T Y Pacoima formation (dark brown breccia and fangiom- erate, locally folded) MAJOR UNOONFORMITY Qs SauRus formation (continental light-colored conglome- rate and sandstone) LOCAL UNCONFORMITY Tpu Upper Pico member (marine sandstone and mudstone, conglomerate; fossiliferous) Tpl Te Sunshine Ranch member (continejital and brackish-water greenish aandstone. mudstone, con- glomerate, red beds and thin lime- atone beds (Is) Lower Pico member (marine conglomerate, sandstone, siltstone. fossiliferous calcareous sandstone) Repetto formation (undifferentiated) (marine siltstone and mudstone, ark- ose, sandstone and conglomerate) Etsmere member t (marine fossiliferous coarse sand- stone and conglomerate, often pet- roliferous; interbedded sandstone ana siltstone) Modelo formation (marine arkose, conglomerate, sand- stone, silicious and diatomaceous shale) UNOONFORMITY INTRUSIVE AND METAMORPHIC ROCKS Pegmatite (chiefly alkali gramte pegmatites) Granite * (buff to pink; includes some quartz monzonite. Pegmatoid and gneiss- aid factes. Inclusions of older rocks) LU id IT Granodiorite (includes some quartz quartz monzonite; granite) diorite and also pink (0 3 -I UJ a. Syenite * (dark, red-weathering quartz-auqite syenite, mtcroperihite) augite and High m pink D hd Hornblende diorite • (dark, brown-weathering; high in white andes\ne, minor pink mi- crocliTie; probably fades of the syenite) dgn Diorite gneiss (dark gneisses; includes some biotite schist. Where injected by granodior- ite (dg.i + gd); including Placenta formatwn rocks {dgn-{-gd-\-p\). Horn- blende-rich fades (h) Placerita formation t (graphite, sillimarute, biotite schists; quartzite. Limestone, dolomite (pi) Pelona schist * (chlorite and acttnolite schists, quart- zite. Many quartz veinlets) Anorthosite * (medium to very coarse-grained, laraely basic andesiTie. Anorthosite ana granite lan+gr) gb Gabbroic and noritic rocks * (altered rocks bordering anorthosite, Ilmenite-magnetite gabbro (gbm), includes jnassive ilmenite-magnet- ite) -) 2 1 ^ Elsmere member t (marine foasilijerous coarse sand- stone and conglomerate, often pet- roliferous, interbedded sandstone and siltstone) Modelo formation (jnarine arkose, conglomerate, sand- stone, silicious and diatomaceo%ts shale) UNCONFORMI T Y -Tmc Mint Canyon formation • (contintnlat sandstone and conglom- erate, mudstone, claystone. tuff, lake beds) UNCONFORMITY So £5 Jill , n > Tick Canyon formation • (continental sandstone and conglom- erate, siltstone, claystone, lake beds) Tt/rtv' Topanga (?) formation t (continental arkose, conglomerate, red and yellow beds. Interbedded andesite and basalt Jiou<8 (Ttv) UNCONFORMITY m Vasquez formation • (continental red beds, sandstone and conglomerate, green and yelUni' sandstone. Interbedded voUanica (Tw) UNCONFORMITY Domengme formation t (marine gray fo greenish hard calcar- eous sandftortc and conglomerate) ^ ■g Martinez formation T 15 (Tnarine greenish-black sandstone. "■ — ■ dark shale, coarse conglomerate) an /« AnorthoEite ♦ 'medium to very coarse-grained largely baste andesine. AnorthoaiU and granite (an-t-gr) Gabbroic and noritic rocks * (altered rocks bordering anorthosite. Ilmenile-magnetite gabbro (gbm), includes massive ilmenite-magnet- ite) Men.ienhall trneiss. ' (blue (Quartz- fl,iiiii,cta3e gneisses ivitk variable amounts oj'/erromagnesian minerata) Well defined Inferred Alluvium and terrace i{ e Well defined Inferred . Concealed Anticline Syncline Strike and dip Vertical Horizontal Foliation Vertical foliation Conglomerate bed Tuff bed Limeatone bed Occurs north of San Gabriel fault Occurs south of San Gabriel fault LIBRARY UNIVEHSiTY OF CAUFOHNIA Base from U.S. Geological Survey 6' 1 :24.00 topofiraphic maps. Geology surveyed 1933-36, 39-41. - 45-52 t^Wt lUfaMlM GEOLOGIC MAP OF THE SAN FERNANDO QUADRANGLE, CALIFORNIA By Gordon B. Oakeshntt SCALE 1-62500 Cnntoiii- intervnl 2(K) feot. (CrintourM fram I : 24000 miipHi 1858 Geology m part after 1. Hill. 1930 2, Jahns 1940 DIVISION OF MINES OLAF P. JENKINS, CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES 6EOL0G1 piotls Bull 172 MISSION HILLS-VASQUEZ CANYON 5000- N ie°E 2000' PACOlMA HILLS-ESCONDIDO CANYON Ols-londslide Ot'terrace deposits Qp-PocOimo fm. Os-Sougus fm Tsf'Sunshme Ronch men Tpu-uppef Pico member Tpl-lo«er Pico member '-Repetto fm. undifferentiated ^-Elsmere member Repetto tm. EXPLANATION Sedimenlory ond volconic rocks Tm-Mode1o (m. Tmc-Mtnt Conyon Im Ttc-Tich Conjon rm T1-Topongo I'l tm Tiv-TopongoCl tm volconic rocfis lember of Pico tm. Tv-Vosguei tm T««-Vosquei (m volcomc tOcKs Td-Domeng.ne fm Tmi-Morl.ne? Im VERDUGO IVIOUNTAINS-MT GLEASON TRAIL Intrusive and metomorphic rocks grp-pegmatile gr -granite gd-gronodiorite sy-syenile nd-horriblend dionte dgn-dionle gneiss pm-Ploce'ilo lormolion on-onorlhosile gb-gabb'aic rocks gbm-ilmenile magnetite pCm-MendentioH gneis TEXAS CANYON-PACOIMfl CANYON J.", '_" '.-T^ A SAN GABRIEL FAULT ZONE-NORTH BLOCK * +g(t+ +/«+ + + + + + + > + + + + + + + + + + + +^/^ + + +oa+ + +tt+ ■^ + * + ^ + '\* + "^ + * * * SAN GABRIEL FAULT ZONE-SOUTH BLOCK Gordon B Ooi MriKAHy UNIVERSITY OF CALlFORinA DAVIS GEOLOGIC STRUCTURE SECTIONS ACROSS SAN FERNANDO QUADRANGLE, CALIFORNIA U2P '5RY OLAF P. JENKINS. CHIEF 5 ulU^^s \r -^