STATE OF CALIFORNIA EARL WARREN. Governor DEPARTMENT OF NATURAL RESOURCES WARREN T. HANNUM. Director DIVISION OF MINES FERRY BUILDING. SAN FRANCISCO 11 OLAF P. JENKINS. Chief SAN FRANCISCO SPECIAL REPORT 24 AUGUST 1952 GEOLOGY OF THE LEBEC QUADRANGLE CALIFORNIA By JOHN C. CROWELL oCostoic Index map showing location of Lebec quadrangle and Ridge Basin. Nearly everyone who has traveled the ''Ridge Route," U. S. Highway 99, between Los Angeles and Bakersfield, has marveled at the succession of steeply dipping, well-stratified sedimentary rocks exposed in naturally eroded cuts and roadcuts in the area south of Gorman, particularly in the Piru Gorge. They are some of the beds of the tremendously thick continental Pliocene deposits that the highway transgresses. At no other place in the world is such a narrow basin occupied by such a thick continental Pliocene section. The Lebec quadrangle, which includes part of the basin, covers part of Los Angeles, Kern, and Ventura Counties; the northern two-thirds of the quadrangle is in the Tehachapi Mountains while the remainder covers the northern end of Ridge Basin. Ridge Basin was a wedge-shaped depression during the late Cenozoic era, in which a remarkable thickness of predomi- nantly non-marine rocks accumulated. Structurally the basin is a complex graben bounded on the southwest by the San Gabriel fault zone, on the northeast by the Liebre fault zone, on the north by the San Andreas fault zone, on the east by overlap onto crystalline basement and Paleoeene-Eocene sedimentary rocks, and on the southeast by gradation into the eastern Ventura Basin. Owing to Pleistocene deformation, the Ridge Basin beds have been squeezed into a northwest plunging syncline between the relatively competent walls of the depression. Older rocks are therefore exposed at the south east and younger at the northwest. GEOLOGY OF THE LEBEC QUADRANGLE, CALIFORNIA By John C. Crowell, * OUTLINE OF REPORT fault; many of the other faults have not moved recently. No new Page evidence on the total displacement of the San Andreas or on its age Abstract 3 lias come from this study. The Oarlock fault zone shows similar Introduction 3 feature's but on a much smaller scale. Descriptive geology 6 Several erosion surfaces are conspicuous in the Lebec quadrangle. Metamorphosed Paleozoic (?) sediments— (5 The Tehachapi Mountains are surmounted bv an old undulatory Jurassic (?) intrusive rocks (i surface which is 1000 feet and more above the present drainage Tertiary rocks 11 system. Lower surfaces are present in some places particularly at Miocene (?) volcanic rocks 11 the edge of Antelope Valley on the east. Principal topographic fea- Miocene series 12 tures in the area are the result of erosion of rocks of varying hard- Pliocene series 13 ness. The trough along the course of the San Andreas' fault, for Quaternary system 17 example, and the lesser one along the Oarlock fault, owe their exist Pleistocene series 17 ence to erosion of rock weakened by shattering. Kecent allUMum 17 \ n mineral resources of commercial value have yet been dis- gtructural geology 17 covered within the Lebec quadrangle. Near the contact of granite and Faults 18 limestone in the northeastern part of the quadrangle tin and other r olds 2.1 i a ] s have been sought in gossan, but the deposits found so far are Geomorphology 21 ( (lo ] ean f or production. Test holes have been drilled in search of Mineral resources 22 petroleum near the quadrangle, but none within it. Only the area Metals 22 underlain by the Santa Margarita format ion, or closely adjacent to Petroleum 23 ji, appears to warrant investigation, as the Santa Margarita forma- Limestone 2.'? tion contains the only marine rocks in the vicinity. One test hole References 23 within the formation was unproductive. Illustrations Plate 1. Geological map of Lebec quadrangle In pocket INTRODUCTION 2. Geologic section's across Lebec quadrangle In pocket Figure 1. Index map showing location of Lebec quadrangle.. fi The Lebec quadrangle, as shown on the index map (fig. 2. Diagrammatic section of Lebec quadrangle 7 1), is at the western end of the Tehachapi Mountains in 3. Photo of diorite showing gneissie banding _ 8 t i l(1 Transverse Ranges between the San Joaquin Valley 4. Photo of Liebre quartz monzonite showing shears *) , ,, ~ ,.„ • ml r. • , ■> • 5. Photo of detail of shears 11 an( * southern California. Ihe area is of interest geologi- 6. Photo of southeast corner of quadrangle-. 10 cally because two of California's great faults, the San 7. Photo of conglomeratic sandstone of Santa Margarita Andreas and the Garlock, cross the quadrangle and meet formation ________ ___ 17 about a mile to the west. The area is viewed each month by «. Photo of shale of Santa Margarita formation 17 ., , ,. . -i T t o ti- v. no. _v. <-j !). Photo of rubble of quartz monzonite dusts in Peace thousands of travelers Oil U. S. Highway 99, the Ridge Valley beds 17 Route" between Bakersfield and Los Angeles, which 10. Photo of conglomeratic sandstone anil mudstone of passes through the quadrangle. lower Hungry Valley formation 18 , , • , , ■, -,-. rru t _ j i Location and Accessibility. The Lebec quadrangle, abstract which covers (il square miles, is 7.1 miles wide in an east- „. T . . . . . . . , . ., , west direction and 8.6 miles Long in a north-south direc- lhe Lebec quadrangle, which includes (>1 square miles at the .. .... _, „ .. . ,. . , .,, western end of the Tehachapi Mountains in southern California, is tl011 - including I \ minutes ot latitude and longitude. With crossed by both the San Andreas and Garlock fault zones. the southeast corner of the quadrangle at 34° 45' north Within the quadrangle igneous and metamorphic rocks are over- latitude and 1 IS 45' west longitude. It lies astride the tain by marine and non-marine Tertiary sedimentary rocks. South boundary between Kern County and Los Angeles County of the San Andreas fault zone the oldest rock is severely sheared, • . . • T7 . , ,, quartz monzonite, which has b i folded and thrust faulted. Ridge ;|1 " 1 extends a short distance into Ventura County on the Basin non-marine clastic rocks, chiefly conglomeratic sandstones and Southwest. mudstones, overlie the quartz monzonite. m • t» e ai „ • .,:„„i i;»,u„ K~+,„^„^ „„„i„„i tw. , tu u a i i /< i i * u ._ i Teion ass. one ot the pre pal links hetween central Between the San Andreas and Garlock fault zones, the rocks •' . '. ' . , , consist of Paleozoic (?) limestone and some shale, siltstone, and and southern California, IS at tile Western edge 01 the sandstone that have been metamorphosed to marble, hornfels, schist, quadrangle at Holland Summit (elevation 4245). The and tactite by intrusive granite. Unconformable- overlying the rocks ))ass permits access from Grapevine Canvon and the San are Tertiary, probably Miocene, andesite flows and breccias, now , ■ ,, ,, ,, ,i , „„„ „ l«„.q;-,,» ;„+^ exposed just north of the San Andreas rift west of Quail Lake. They Joaquin \ alley on the north to canyons leading into in turn are overlain unconformably by at least c.ooo feet of upper southern California on the south and to Antelope valley Miocene shale, sandstone, and conglomerate, assigned to the Santa and the Mojave Desert Oil the east. From Tejon Pass the M lw r K ta o f, ; r To 0n 'p , i r h i i ♦ ■ , Tehachapi 'Mountains extend northeastward about 40 Northwest of the Garlock fault zone only plutonic and meta- ., ' ... . n . XT -, . m _„_i • r>„™ morphic rocks are exposed. They consist of gneissic hornblende miles t o merge with the Sierra Nevada at rehachapi lass, diorite, granite, and quartz monzonite containing a few masses of From the vicinity of ( irapevine ( 'reek, ill the northwestern limestone, hornfels, and schist. The diorite lies in the footwall of corner of the quadrangle the San Eltligdio Mountains qtrSinzorLuh^ingtln.^' 111 " the ^ "'""' and the -tend westward 35 miles to the Cuyama Valley (fig. 1). The San Andreas fault zone, which crosses the southern part of South of the two ranges, which are moderately Well- the quadrangle, consists of a major fault with a slightly undulatory defined topographically, is a broad mountainous region course. Associated are many subparallel faults which separate slivers •__•__ __li V ^e +i,„ rp_„_._. T[ ,. p,„„„„„ lvino- of rock. Fault scarps and sag ponds along the course of the fault zone Wlthln the rn,tral ' )art ()i the Transverse Ranges, lying indicate very recent movement, particularly along the principal between the San Gabriel Mountains on the southeast ana ' the San Rafael and Santa Ynez Mountains on the west, Assistant professor of geology, University of California, Los Angeles, T3_„_ri„ +VGc rno-inn i« rlvainorl chieflv bv Pirn Creek and California. Manuscript submitted for publication March 1952. liecduse tills region IS (trained cnieu> V} l nu W' ck mici (3) Special Report 24 its tributaries, Axelrod 1 called them the Piru Mountains. Several prominent ridges and mountains within this region stand above the dissected, rugged upland. Just west of Tejon Pass, Frazier Mountain reaches an elevation of 8013 feet. Alamo Mountain, on the southwest, has an elevation of 7450 feet, and Liebre Mountain on the south- east, one of 5771 feet. Hungry Valley and Peace Valley, with the nearby low hills, lie between Frazier Mountain and Alamo Mountain on the west and Liebre Mountain on the cast, and just south of the westernmost dip of the Tehachapi Mountains. This relatively low-lying area pro- vides an easy route for highways, pipelines, electric lines, and telephone cables between Tejon Pass and San Joaquin Valley on the north and the valleys of southern California. The Lebec quadrangle is easily reached by U. S. High- way 99, the four-lane trunk freeway connecting Bakers- field and Los Angeles. A mile east of Gorman, California State Highway 138 leads eastward from Highway 99 to Lancaster and Palmdale in Antelope Valley. Dirt and gravel roads, maintained by ranchers and utility com- panies, reach into all sections of the quadrangle. Most of these are kept in good condition and are passable throughout the year except for a few days following win- ter storms. In addition to these there are many minor roads, some little-used or abandoned, which are passable only in good weather. From the network of roads, any point in the quadrangle can be reached on foot in about 2 hours. Lebec and Gorman, the two towns in the area, have grown up chiefly as wayside stops for travelers on High- way 99. In addition, several service stations, some with associated restaurants and garages, are along the highway. The larger ranches, which own or lease most of the prop- erty in the quadrangle, are the Tejon Ranch, Harry Hol- land Ranch, Lloyd Ralph Ranch, O. Hovden Ranch, and G. E. Kinsey Ranch. Cattle and a few sheep and goats graze over most of the region with the exception of the low flat areas of Castaic, Peace, and Hungry Valley, where wheat and potatoes are grown. Most of the crops are raised by dry farming except locally where well-water is used for irrigation. Topography. The quadrangle is divided into two topo- graphic units by the San Andreas fault zone. To the north the terrane is characterized by steep slopes, little dis- sected, which rise abruptly from the canyons to a gently rolling upland surface. Relief in this sector extends from a low of 3325 feet above sea level in Grapevine Creek to a high of 5430 feet stop the Tehachapi Mountains. Locally the topography rises over 1000 feet in 1 mile, as in Grape- vine Canyon and east of Gorman. This terrane, underlain principally by homogeneous plutonic rocks, is so deeply weathered that outcrops and cliffs are uncommon. In the southeast corner of the quadrangle however, where lime- stone beds crop out, the slopes are rugged and jagged out- crops frequent. The topography south of the San Andreas rift presents a distinctly different aspect. For the first mile and a half south of the rift there are gently rolling hills of only a few hundred feet relief underlain chiefly by sandstone and shales of the Hungry Valley formation. Farther south, in the vicinity of Freeman Canyon, precipitous 1 Axelrod, D. I., The Piru Gorge flora of southern California : Carnegie Inst. Washington Pub. 590, V, pp. 159-214, 1950. amphitheaters have been cut into thick consolidated con- glomerates. Much of this terrane is badlands, with here and there near-vertical cliffs up to 300 feet high. The low- est elevation in the quadrangle, 3142 feet, is found at the southern boundary in Peace Valley. Unusual topography is found along the San Andreas rift. At several places the alluvium and terrace deposits have been broken by recent fault movement, and narrow wedge-shaped units, up to a half mile in length, are sepa- rated by fault scarps. Drainage impounded behind some of these scarps, and in down-dropped segments, has accumu- lated to form sag ponds. Other depressions, somewhat older, have been filled with fine sediment and now form swampy or flat areas. South of Quail Lake many landslides in unconsolidated sandstone, conglomerate, and brecciated quartz monzonite are associated with elongate fault slivers and were formed probably when fault movement over- 1 steepened the hill side. All streams within the quadrangle are either intermit- tent or ephemeral. Grapevine Creek, which flows north- ward to the San Joaquin Valley from Castaic Lake, has the largest volume of any of the creeks in the quadrangle, but during the late summer and early fall, it, too, is dry. Oso Creek, and a few other streams on the flanks of the Tehachapi Mountains, flow weakly for several months in the spring following the rainy season, but by midsummer are reduced to a chain of unconnected pools. All other stream courses in the area are dry throughout the year ex- cept for a few hours or days immediately following rain- storms or sudden snow melts. Castaic Lake, fed chiefly by water from the southwest, is now a permanent lake, although its level fluctuates markedly from season to season and year to year. Several years ago water withdrawals from Castaic Valley and Grapevine Creek caused the lake to dry up, but in recent years this has not been allowed. Quail Lake, on the other hand, has been diminishing in size over the past few years, and now contains only a few feet of water in its western tip. The remainder of the lake basin, extending out of the quadrangle toward the east, is blanketed with white alka- line salts. One sag pond, shown on the map about midway across the quadrangle in the San Andreas rift, contains water permanently. Previous Work. Only a little detailed geologic work has previously been done in the Lebec quadrangle. Pub- lished notes by early geologists who visited the area are very brief. Recently Wiese and Page 2 mapped and de- scribed the tin prospects at the eastern edge of the quad- rangle, and Loel 3 prepared a generalized map and cross- section along II. S. Highway 99 southward from Lebec tc; Castaic. Crowell 4 described the Hungry Valley area to the south which extends a short distance into the Lebec quad- rangle. Fine 5 and Wiese and Fine G described the geology of the western part of Antelope Valley in the vicinity of 2 Wiese, J. H., and Page, L. R., Tin deposits of the Gorman district, Kern County, California: California Div. Mines Rept. 42, pp. 31-52, 1946. 3 Loel, Wayne, Geology of the Ridge Route with road log from Lebec to Castaic Junction : Am. Assoc. Petroleum Geologists Field Trip Guidebook, Los Angeles, California, pp. 128-132, 1947. * Crowell, J. C., Geology of Hungry Valley area, southern California: Am. Assoc. Petroleum Geologists Bull., vol. 34, pp. 1623-1646. 1950. D Pine, S. F., Geology of part of the western end of Antelope Valley, California: Unpublished M.A. thesis, California Univ. Los Angeles, pp. 1-36, 1947. 6 Wiese, J. H., and Fine, S. F., Structural features of western Antelope Valley, California: Am. Assoc. Petroleum Geologists Bull., vol. 34 pp. 1647-1658, 1950. Geology of the Lebec Quadrangle 120- i".,^ '-, L H£P.N CO SAN LUIS n OBISPO CO. BAKERJ-FICLD \\9'\ i"Z'--- 5/^««A N € V A D A 118" SAN 'H J O A Q U I N L £ V : **«, s ''"I -35" "^5s" *'t "V S \ 1 .■'/,., ,%•% /"^ > ,!»"( ,.'"-. \ ''I 1* vC '-•• ' 1 '" "-, '.. "'. ': / .->., \ '"'' 'i^** ^sT *> : ""'--...-'"'\,''""'' '"'- ,." * - - (\ '' ' z f \»* \**, „- v '~ + * o" ->M0JAV-E -35 H SAN £ M I D I O M T N } . fRAZIER ,-;-\L4BEC i-v PARK r raz. I « r Attn GORMAN A N T £ L O P £ V A L L £ Y A£7 W C O L05 ANG£.L£} CO. < 3 - S' 3 ■; - ■"• -; tO.k f A A/ T A Y A/ £ Z t'^/U r A/ J \ \ MCA5TER, Li t br m Mtn r O P A T O P A M T N S .»*"°5 L .-'"', .."< A C I f I C OCEAN V£NTURA\ -34- >CAL£ IN MILE$ 5 10 15 20 25 M M M I -I I- C CA5TAIC /j-. *V / ' ' A/ _IV rf^OLLY- W00DJ (RA5ADCNA fL05 ANGELA -34- 15" _l Figure 1. Index map showing location of Lebec quadrangle and neighboring geographic features. Special Report 24 Quail Lake. These papers, and one by Wiese 7 which covers the Neenach quadrangle adjoining on the east, were very helpful in the preparation of this report. Field Work and Acknowledgments. The field work upon which this report is based was carried out intermit- tently from 1047 to 19f>l ; altogether about 3 months were spent. Mapping was done on aerial photographs with a scale of 4 inches to the mile, flown by the U. S. Forest Service in 1942. Data from the photographs were trans- ferred to the Lebec quadrangle, prepared by the U. S. Army Map Service in 1943. It is a pleasure to acknowledge the help from discus- sions with Corded Durrell and James Gilluly, and to thank Cordell Durrell for reading the manuscript criti- cally. In addition, appreciation is extended to William H. Corey, who generously supplied the list of fossils recov- ered from the Santa Margarita formation. Part of the field expenses were defrayed by a Research Grant of the Uni- versity of California, Los Angeles. DESCRIPTIVE GEOLOGY The rocks of the Lebec quadrangle range in age from Paleozoic (?) to late Pleistocene. The basement rocks in- clude two kinds of granite, two kinds of quartz monzo- nites, crushed grahodiorite, diorite, and metamorphosed sediments of possible Paleozoic age. Overlying them are andesite flows, clastic sedimentary rocks of Tertiary age, and sand and gravel of Quaternary age. With the excep- tion of the Paleozoic (?) metamorphic rocks and late Pleistocene terrace deposits, correlations have not been possible across the San Andreas and Garlock faults. Metamorphosed Paleozoic (?) Sediments The oldest rocks of the Lebec quadrangle are large masses of limestone, with minor amounts of associated schist, quartzite, and hornfels, which cap the Tehachapi Mountains on the northeast and extend into the Neenach quadrangle. 8 Other exposures, chiefly small blocks only a foot in diameter, occur northwest of the Garlock fault in the Lebec quartz monzonite, particularly near Lebec and north of School Canyon. Slivers of similar rocks are found within the San Andreas and Garlock fault zones. On the geologic map (pi. 1) the rocks are divided into two units, one, chiefly limestone, and the other,_ chiefly schist and hornfels. Terrane underlain by the limestone or marble is mainly rugged, with numerous pitted and jagged outcrops, but covered with dense, nearly impenetrable thickets in which scrub oak predominates. The granite and quartz monzonite surrounding the limestone support grass and sparse trees, allowing limestone areas to stand out clearly both from a distance and on aerial photographs. Solution of the lime- stone has formed sink-holes, one of which occurs very near the top of the highest mountain in the area, and is shown on the contour map as a circular depression. The limestone usually consists of a coarse aggregate of interlocking bluish crystals of calcite which range in size from a few millimeters up to a few centimeters. Most of the rock is quite pure, but streaks of graphite and thin lenses of quartzite, calc-silicate hornfels, and iron-stained 7 Wiese, J. H., Geology and mineral resources of the Neenach quad- rangle, California: California Div. Mines Bull. 153, pp. 1-53, 1950. s W lese, J. H., op. cit., 1950. tactite, are intermixed. Diopside and garnet are locally conspicuous, and epidote, mica, feldspar, and quartz are not uncommon. Bedding has been preserved in a few places, as in the lens north of Castaic Lake, and along the eastern border of the quadrangle where it dips about 40° N. The general lack of bedding, poor exposures, and complexity of the structure where discernible have prevented mapping within the limestone bodies for this study, although de- tailed work on a large scale in selected areas might be rewarding. Associated with the limestone, but usually occurring independently, are elongate bodies of a friable dark-gray quartz-feldspar-biotite schist that has a saccharoiclal tex- ture made up of subspheroidal grains, 1 millimeter or 2 millimeters in diameter, in which fissility is caused by the relatively uniform orientation of biotite flakes. The quartz content varies, reaching 50 percent in some thin layers. The thinly bedded appearance of the rocks, as well as the composition, suggests that the schist was originally fine- grained arkose or silty sandstone, reconstituted by meta- morphism but without much, if any, introduction of material. In view of the composition and structure of the meta- morphosed series and its relation to the granite and quartz monzonite, there seems but little doubt that its outcrops are remnants of the sedimentary country rock invaded by the magma. The small inclusions are probably stoped blocks and the large exposure of limestone in the north- eastern corner of the area, a remnant of the roof rock. Although no fossils have been found in the metamor- phosed sediments, they are probably Paleozoic in age as they are lithologically similar to Paleozoic rocks in the Inyo Range and Randsburg district." 10 ' 11 The upper age limit is determined by the age of the intruding granitic rocks which are probably late Jurassic or early Cre- taceous. Jurassic (?) Intrusive Rocks Six plutonic intrusive rocks are exposed in the Lebec quadrangle and together make up over half of the area. In the absence of evidence to date the emplacement of these rocks, they are questionably assigned to the Jurassic period, although they may equally be Cretaceous in age. They resemble and have geologic occurrences similar to granitic rocks of the northern Sierra Nevada, emplaced during late Jurassic time 12 and of Baja California, emplaced during the Cretaceous period. 13 Diorite. Hornblende diorite is exposed over less than a square mile in the northwestern corner of the Lebec quadrangle where it forms the footwall of the Pastoria thrust zone. It extends northeastward across the Pastoria Creek quadrangle into the Neenach quadrangle. 14 In con- trast to the quartz monzonite to the south, which underlie? o Knopf, Adolph, A geologic reconnaissance of the Inyo Range anr the eastern slope of southern Sierra Nevada, California : U. b Geol. Survey Prof. Paper 110, 130 pp., 1910. i° Hulin C. D., Geology and ore deposits of the Randshurg quadrangle California: California Min. Bur. Bull. 95, 14S pp., 1925. "Wiese, J. H., op. cit., 1950. 12 Hinds, N. E. A., The Jurassic age of the last granitoid intrusives n the Klamath Mountains and Sierra Nevada, California, Amer Jour. Sci., 5th ser., vol. 27, pp. 1S2-192, 1924. "Woodford, A. O., and Harris, T. F., Geological reconnaissance acros: Sierra San Pedro Martin, Baja California: Geol. Soc. Americ: Bull., vol. 49, pp. 1297-1336, 1938. 11 Wiese, J. H., op. cit., 1950. Geology of the Lebec Quadrangle 8 Special Report 24 grassy barren hills with sparse trees, the diorite supports considerably more chaparral and woodland, and crops out in ragged ledges. The typical diorite is gray green and gneissose, con- tains about 40 percent dark minerals, and has grains 2 to 7 millimeters in diameter. Within the small area of ex- posure it is homogeneous ; the only subordinate facies con- sist of altered zones near the bordering faults. The distinct gneissic banding results from the elongation of the min- erals, apparently by flowage during intrusion, rather than from a marked separation of the dark and light minerals into folia. The contacts between minerals are slightly blurred ; the plagioclase crystals are larger than the horn- blende crystals, which have been partially streaked out parallel to the banding. Under the microscope the rock shows a mild crushing with microbreccia between the larger grains. In most of the specimens less than 1 percent of the rock has been finely ground, but in some the propor- tion is a little higher. The microbreccia is composed prin- cipally of a fine-grained mosaic of quartz showing strained and undulatory extinction that is associated with chlorite and iron stains. Because most of the quartz in the rock, which seldom exceeds 5 percent of the whole, is present in the microbreccia, the crushing may have occurred during final stages of crystallization as the mass was intruded. About half of the diorite consists of plagioclase (sodic andesine), mildly strained and slightly altered to sericite. The hornblende, making up about 40 percent of the rock, is bright green, slightly pleochroic, fractured, and com- monly altered to chlorite in part. Epidote, apatite, and magnetite are also present. Near the Pastoria fault zone at the northern boundary of the quadrangle the diorite has been significantly altered to a light gray-green silicified rock. Thin sections show a marked increase in fracturing and in the percentage of quartz, again distributed through the microbreccia be- tween the grains of feldspar and hornblende. Near the fault, which parallels the banding, the rock approaches a true mylonite, and about two-thirds of some specimens consist of milled rock flour. Epidote and chlorite are in- creased at the expense of hornblende, and there is about 5 percent of calcite. School Canyon Granite. Buff and orange granite is exposed in the northwestern corner of the Lebec quad- rangle within the Pastoria fault zone. Large jagged out- crops and cockcombs occur north of School Canyon, after which the granite is named. The School Canyon granite is similar to the Tejon Lookout granite, but as a rule it is coarser-grained, has a lower percentage of ferro-mag- nesian minerals, and is much more resistant to weathering. It is quite possible, however, that the two granites are closely related, although the relationship has not yet been established. The School Canyon granite consists typically of about 50 percent microcline, 25 percent plagioclase (sodic oligo- clase), 15 percent quartz, and 10 percent biotite and its alteration products. The microcline is markedly perthitic, and blebs of plagioclase are large enough to show twinning lamellae with here and there some myrmekite. Most speci- mens of the rock have been strongly sheared, and thin sec- tions show fractures, wavy extinctions, and mortar struc- ture. Some fractures cut through groups of crystals, and are filled with limonite derived from shredded and altered .-1 Figure 3. Diorite, showing gneissic banding. Dark minerals are chiefly hornblende, light minerals chiefly plagioclase with minor quartz. North side of School Canyon at the western border of Lebec quadrangle. biotite. To a great extent the characteristic orange and buff mottled appearance of the rock is due to iron-stains permeating the rock from such a source. Where deformation of the granite has been most intense, as near faults of the Pastoria zone, the rock has been crushed and sheared to a cataclasite. Thin sections show a microbreccia of feldspar and quartz, in a very fine- grained groundmass, stained with limonite. Here and there the cataclasite is crossed by shears along which frag- ments of the microbreccia have been milled to mylonite, but in the main the rock appears to have been crushed without much milling or shearing. In hand specimen these rocks are orange, aphanitic, massive, and splotched with' dark ironstains and only rarely contain masses where the original granitic nature can be recognized. Some show diffusion circles of iron stains similar to Liesegang rings. Lebec Quartz Monzonite. Gray Lebec quartz monzo- nite is exposed over about 14 square miles of the Lebec quadrangle northwest of the Garlock fault. It extends on west from Lebec several miles, but only a short distance northeastward into the Pastoria Creek quadrangle. So far as is known, it is confined to the hanging-wall block of the Pastoria thrust zone and has not been recognized north of the Pastoria thrust or south of the Garlock and San. Andreas faults. Geology of the Lebec Quadrangle «: we? - , e 5. <-.v-> w ' «■ V . -V; i tiki? ■ "Z. ..■ '-'-' ***> «*^Tr . ■ _ ■. ** -• ^i- • - . **« •*',-■ V. Figurio 4. Liebre quartz monzonite showing shears. Quarry a quarter mile west of V . S. Highway !•!( near southern border of -- - Lebec quadrangle. Terrane underlain by the Lebec quartz monzonite is characterized by subrounded, steep hills with few out- crops and a covering of deep grass and scattered oaks. The rock is best exposed in precipitous amphitheaters at the heads of small steep canyons. Elsewhere outcrops are rare, eveti in dry creek bottoms, and are practically limited to the slopes just below the prominent summit upland. The typical quartz monzonite consists of about 40 per- cent plagioclase (usually oligoclase), .'?;") percent orthoclase (microcline in some sections), 15 percent quartz, (5 per- cent biotite, '2 percent hornblende, and 2 percent apatite, sphene, zircon, and magnetite. Most of the plagioclase, twinned and euhedral, is fresh and only slightly altered to sericite. Most potash feldspar is poikilitic and interstitial, although some is perthitic, containing streaks, patches, and blebs of twinned albite, and a little is myrmekitic. The biotite is strongly pleochroic, commonly has a ragged crystal form, and much is altered to chlorite, muscovite, and iron oxides. Two i'acics of the Lebec quartz monzonite are con- spicuous, one gray and medium-grained, the other buff and somewhat more coarse-grained with gradational and indistinct contacts. The gray fades is the dominant type and probably makes up 80 percent of the rock, and con- tains the hurt' facies as irregular and elongated bodies. Through a distance of several inches, and sometimes sev- eral feet, the grain size of the rock changes from an average of less than 3 millimeters to aboul 5. The buff color, which is associated with the coarse facies. appears to be caused by secondary stains of limonite; so far as could be determined it was not due to any significant dif- ference in the primary mineralogy. Shearing and slickensiding are present everywhere in the quartz monozonite but near the Garlock and Pastoria fault zones the shearing is developed to an even greater degree. Despite the sheared character of the rock in out- crop, thin sections taken between shears show little cata- clasis, although a few specimens have slight fractures. in Special Report 24 The Lebec quartz monzonite contains small stoped blocks or pendants of marble, hornfels, schist, and quart - zite. Since the Tejon Lookout granite intrudes similar rocks, the two are probably related although now separ- ated by the Garlock fault. The relative age of the quartz monzonite in respect to the other plutonic rocks of the region cannot be determined, however, since an intrusive contact has not yet been recognized. Tejon Lookout Granite. A light buff, medium- to coarse-grained biotite granite is the predominant rock cropping out in the wedge-shaped area between the San Andreas and Garlock faults and is well exposed near Tejon Lookout. It underlies about half of the Lebec quad- rangle and no doubt extends beneath the Paleozoic (?) limestone in the northeast and beneath the Santa Marga- rita formation on the east. The rock extends less than a mile westward to where the Garlock fault meets the San Andreas rift. Farther northeast it underlies about 30 square miles of the Neenach quadrangle. 15 Deep weathering along irregular shears and joints, re- sulting in easy disintegration of the rock, is characteristic of the Tejon Lookout granite. Few good outcrops occur, even in deep canyons, and rounded hills covered with grass and scattered oaks predominate. The granite is exposed at buff bare spots where the soil has been carried away and in steep gullies at canyon heads, particularly near the San Andreas and Garlock faults. These conspicuous salmon-colored scars often originate in part at the base of the deep regolith by spring-sapping, where the upland surface meets the steep canyon walls. The fine-grained facies of the rock is less susceptible to disintegration and weathers into sub-spheroidal blocks demarcated by an ir- regular joint system. The granite body appears to be composed of five prin- cipal facies with minor variations. Most typical, and prob- ably making up 75 percent, is the massive, medium- grained (2 to 5 millimeters) buff biotite granite, so prone to disintegration. In hand specimen its color ranges from gray to salmon ; most commonly it is pinkish-buff. On smooth weathered surfaces large squarish crystals of pot- ash feldspar and clear bluish quartz are conspicuous. About 35 percent of the rock, sometimes more, is potash feldspar, 20 percent plagioclase, 25 percent quartz, 10 percent biotite, and the remainder apatite, zircon, magne- tite, and secondary minerals. Biotite in booklets and dis- seminated shreds, and in rims around the potash feldspar, is usually ragged and partly altered to chlorite and hema- tite. Locally the rock is slightly porphyritic with large poikilitic phenoerysts of potash feldspar, up to 3 centi- meters in length. The other facies are found within the one described above and do not represent any considerable departure in mineralogic composition. Comprising probably 10 per- cent of the area are medium-grained aplites composed mainly of potash feldspar and quartz with minor amounts of biotite. This variant is slightly finer grained than the predominant facies, has an interlocking granitic texture, and is more resistant to weathering. Another aplite, but whiter and finer-grained, is a third variant characterized by a granular texture which permits easy disintegration. The rock certainly makes up less than " Wiese, J. H., op. cit. 1950. 10 percent of the area, and occurs in nearly flat-lying veins up to 2 feet in thickness having sharp contacts. A fine white dusty alteration product, perhaps kaolinite, is con- spicuous. Quite distinct from these three types is the fourth, con- sisting of thin lenticular basic segregations made up al- most entirely of altered biotite and minor amounts of feld- spar. This facies probably comprises not more than 2 or 3 percent of the granite mass. The fifth, pegmatite, consist- ing predominantly of quartz and potash feldspar crystals up to 4 or 5 centimeters in length, also totals less than 2 or 3 percent of the mass. Near the San Andreas rift, and to a lesser extent, the Garlock fault, the granite is commonly finer-grained, and individual crystals of clear quartz and feldspar can not be easily discriminated with the hand lens. Biotite, much altered to chlorite, is often streaked out. Under the micro- scope the rock shows a moderate cataclasis superimposed upon the granitic texttire. Albite twin lamellae of the plag- ioclase are bent between larger grains, all within a mortar structure. Quartz, mildly strained as shown by undula- tory extinction, has crystallized in small embayments in the feldspar. Crushed Granodiorite. Crushed and comminuted granodiorite with some quartz diorite and diorite occurs in slivers up to a quarter of a mile in length in the San Andreas fault zone, and in the thrust-plate south of Gor- man. The rock shows great variation in appearance, tex- ture, and composition. Blocks of the rock incorporated in the San Andreas fault zone are bounded by zones of breccia and gouge. Cen- ters of the blocks are often fairly solid although serici- ' tized, chloritized, and iron-stained. In some places the rock has a normal granitic texture, with only a mortar structure and bent feldspar twinning lamellae. The grano- diorite in the thrust plate south of Gorman, which is tenta- tively considered to have had its roots in the rift zone, ; often shows well-marked gneissic banding. Hand specimens of the rock are either dark gray, green, or brownish and contain conspicuous plagioclase, biotite, hornblende, and quartz, although in some the quartz is ! barely discernible. Contacts between the minerals are us- ually vague and indistinct, no doubt due to cataclasis and alteration. The feldspar often has an unusual porcellan- eous lustre and the biotite a distinctive golden brown color. Under the microscope the feldspar is seen to consist of both orthoclase and plagioclase (itsually andesine) al- though the proportion of the two varies greatly. Quartz ranges between 10 and 15 percent of the rock, hornblende between 15 and 20 percent and biotite between 5 and 15 percent. Epidote, apatite, zircon, and iron oxides are also present. The source of the granodiorite slivers is unknown. As the comminuted rock contains several large pieces of lime- stone, the blocks may have been torn from rocks north of the San Andreas fault zone, but until more is known about the distribution of crystalline rocks in the region no corre- lation is possible. Liebre Quartz Mouzonite. Gray quartz monzonite crops out at the western tip of Liebre Mountain in the Geology of the Lebec Quadrangle 11 I 'few ■>' X A s FlOURE 5. Detail of shears, Liebre quartz monzonite. Black Rouge is at hammerhead, so soft that the knife was easily pushed into it. Location of this photograph shown by hammer in figure 2. southeastern corner of the Lebec quadrangle, in the anti- oline beneath Hungry Valley and Peace Valley beds a1 the southern border of the area, and in slivers within the Han Andreas fault zone. These relations suggest that the rock forms the basement beneath Ridge Basin sediments in this region. How far westward it extends beneath the sedi- ments is speculative but it does not extend beyond the San Gabriel fault and its northwestward projection. 18 The quartz monzonite can be traced from the southeastern cor- ner of the quadrangle into the Neenach quadrangle ,T and the main mass of Liebre Mountain. It lias not been recog- nized northeast of the San Andreas rift. The Liebre quartz monzonite in the Lebec quadrangle is characterized by the closely spaced joints and shears (figs. 4 and 5). This brecciation, aided by deep weather- ing, results in rapid disintegration and paucity of out- crops. Although Liebre Mountain and its extension toward the northwest stand higher than the surrounding terrane, and are composed of this rock, they are much more rounded and subdued than the hills underlain by the Ridge Basin sedimentary rocks to the west. The typical quartz monzonite is gray and medium- grained with crystals averaging about 2 or 3 millimeters in diameter, although locally the rock is porphyritie with "Crowell, J. C, op. cit, 1!>r>0. " Wiese, J. H., op. cit., l!». r )0. squarish plagioclase phenocrysts up to a centimeter in length. It is composed of 30 percent orthoclase, 35 percent plagioclase (andesine and oligoclase), much of which is saussuritized, 25 percent quartz, and about 15 percent biotite. Minor amounts of hornblende, epidote, calcite, sphene, apatite, zircon, and iron oxide minerals are pres- ent. The granitic texture has been slightly modified by cataclasis, although samples taken from rock masses be- tween shears do not show more than minor fracturing, bent plagioclase twin lamellae, and undulatory extinction. Here and there the rock has a faint flow banding. Trains of elongate and spindle-shaped dark inclusions, which, though conspicuous in the quartz monzonite, prob- ably constitute less than 1 or 2 percent of the mass. They ran^e in length from a few inches up to a score or more feet, with sharp, yet gradational, contacts. The inclusions sometimes carry a faint foliation parallel to that of the surrounding rock. They are composed largely of biotite and hornblende and up to 40 percent plagioclase (ande- sine), with minor amounts of quartz and accessory min- erals, chiefly sphene. Thin sections show a crystalloblastic texture with an indistinct gneissic foliation. Although the origin of the bodies is not clear they may be partially assimilated masses of either the country rock into which the quartz monzonite was emplaced, or concentrations of early crystallizing minerals. Aplite and pegmatite dikes are common throughout the Liebre quartz monzonite, and in view of their resistance to weathering, fragments from them litter hillsides under- lain by the rock. Some are several feet in thickness, and can be traced for a few hundred yards, but most are much thinner. Tertiary Rocks Miocene (?) Volcanic Rocks Andesite Flows. Immediately north of the San An- dreas Hit a 50- to 100 foot thick How of purple andesite lies upon the Tejon Lookout granite beneath the basal peb- bly sandstones of the Santa Margarita formation. Similar rocks, with associated flow breccia and interbedded sand- stone and shale, occur in thin slivers along the San An- dreas fault as far west as Holland's Summit. Massive purple andesite. strongly fractured, is the pre- dominant volcanic rock. Judging from the texture and interbedded relation with clastic sediments, it was prob- ably extruded as thick flows with local dikes and feeders, one of which crops out in fine-grained granite within the rift zone about jj of a mile east of the junction of Highways !>!» and 138. Here and there scoriaceous andesite crops out which may have formed near the top of a flow. Under the hand lens most of the andesite is seen to be aphanitic ex- cept for dusty concentrations of limonite representing altered phenocrysts. Thin sections show a sparsely porphyritie rock with a pilotaxitic groundmass. Most of the phenocrysts are al- tered biotite. ragged and replaced by hematite, chlorite, and epidote. Shreds of muscovite and veins of calcite are present. The groundmass of the andesite consists of a felty mass of plagioclase laths up to 1 millimeter in length, but averaging about half a millimeter, The plagioclase, calcic-andcsine, is extensively altered to scricite and epi- dote, and freely intermixed with disseminations and streaks of iron oxide minerals. 12 Special Report 24 Minor intercalations of volcanic breccia and clastic sedi- ments occur in the volcanic series. The breccia is composed of angular volcanic fragments welded by greenish glass. The sandstone and shale lenses, no doubt deposited be- tween flows, are best exposed just north of Highway 138 about a mile east of its intersection with Highway 99. The position of the thin andcsite flow between the granite and the Santa Margarita sandstone gives the age of the volcanic rock as post- Jurassic (?) and pre-late Mio- cene. In the Neenach quadrangle the volcanic rocks are much better represented and reach a maximum thickness of at least 5000 feet. 18 Although proof is lacking, a Mio- cene age for the volcanic rocks seems reasonable since the flows are structurally conformable beneath the Santa Margarita sandstones, and elsewhere in southern Califor- nia thick sections of Miocene volcanics are common. They may just as well be older, however. Silicified Andesite. Irregular dikes of buff silicified andesite crop out near the northern boundary of the Lebec quadrangle, intruding Lebec quartz monzonite and meta- morphosed limestone. Dikes are well-exposed in roadcuts of the Powerline road, although the largest exposure caps the nearby ridge to the west. The andesite forms ragged outcrops which weather into a dark brown rubble of angular block. Fresh exposures are characterized by dif- fusion rings of limonite which stain the buff-colored rock with distinct scalloped bands. The microscope reveals the rock to be made of felted feldspar laths in interstitial secondary quartz, with ir- regular blotches and disseminations of limonite. A few of the limonite patches show a questionable amphibole crystal outline, suggesting that originally the rock had sparse small phenocrysts of hornblende. Quartz, apparently en- tirely secondary, occurs in two forms : as chalcedony in the groundmass and as a very fine mosaic among replaced feldspar laths. The highly altered nature of the rock pre- cludes correlation with other volcanic rocks in the region. It is placed in the Miocene for convenience, although all that is known about its age is that it is post- Jurassic ( ?). Miocene Series Santa Margarita Formation. Marine shale, sandstone, and conglomerate beds of late Miocene age crop out at the eastern border of the quadrangle north of the San Andreas rift. Here they lie upon andesite and Tejon Lookout granite, and in general dip eastward and north- ward beneath the terrace deposits and alluvium at the western tip of Antelope Valley. Hills underlain by the formation are subrounded, and covered with only sparse grass and scattered oaks. Here and there, as northeast of Oso Creek, the soil is very thin, and beds trend faintly across the hills, although good outcrops are rare. Along the San Andreas rift, where erosional dissection has been greater than to the northeast, the rocks are well exposed and can be observed easily from Highway 138 just west of Quail Lake. The formation is exposed in three principal sectors, separated by two faults. West of the German fault the lowermost unit, consisting of coarse sandstones and con- glomerate beds, lies on purple andesite and Tejon Look- out granite. Between this fault and the north-south fault about half a mile to the east, a maximum of 3300 feet of 18 Wiese, J. H., op. cit. 1950. shale, sandstone, and conglomerate, gently folded except right near the San Andreas fault, dips toward the east. East of this north-south fault, more than 5000 feet of sandstone and conglomerate with a general east-west strike are folded into several anticlines and synclines, slightly faulted. Correlation between beds in these three sectors is difficult and has been only partly successful. The basal gray pebbly sandstone and conglomerate beds of the Santa Margarita formation lie depositionally upon the Tejon Lookout granite and Miocene ( ?) andesite along the western edge of exposure of the formation. Just north of Oso Creek the basal beds contain numerous fos- sils, chiefly Pert en and Ostrea, weakly cemented in gray pebble conglomerate. Proceeding upward from massive beds, the bedding becomes more distinct. At the top of the section just west of the German fault, about 80 percent of the rocks are gray and orange gritty and pebbly sand- stone in beds 2 inches to 2 feet in thickness. About 15 percent is composed of soft gray silty sandstone, in beds from half an inch to 6 inches in thickness. These, as well as gray and brown medium-fine biotite arkose, in 2- to 6- inch beds, are intercalated with pebbly sandstone. Thin layers of dark gray-brown and bluish silt shale occur along with the arkose. All of these rocks, except the shale, appear highly permeable. Clasts in the lower unit of the Santa Margarita forma- tion consist predominantly of the Tejon Lookout granite, with the resistant pegmatitic and aplitic dikes chiefly represented. Light purple clasts of the underlying ande- site are conspicuous, but mostly several stratigraphic feet above the base. Here, too, occur subangular fragments of cream-colored, bleached, flow-banded rhyolite. North of Oso Creek, and west of the Powerline fault, granitic debris prevails to the near exclusion of other rock types. In this area, the fault can be mapped as separating the coarse irregularly, bedded rubble of granite on the west from better bedded gray pebbly sandstones on the east. The rocks in the triangular wedge between the San Andreas, German, and north-trending fault on the east are interbedded pebbly sandstone and shale with a general easterly dip. The beds are considered to lie close above the rocks west of the German fault, because shale stringers lithologically similar to the upper shale beds begin to come into the section just west of the fault. An iinknown thickness of beds may be missing, however. In the north- ern and western part of the triangular sector, brown thin- bedded fine-grained sandstone and shale predominate which give way rapidly to white soft conglomeratic sand- stone toward the south. At the San Andreas fault, in the upper part of this section, only very minor stringers of fine thin-bedded sandstone and shale remain, although at the base of the section, near the German fault, this lithology still predominates. Tongues of these two rock types have been differentiated on the geologic map. Outcrops of the lower and northern sandstone and shale consist of about sixty percent brown and gray, hard, well- cemented arkose in beds from half an inch to nearly 1 foot in thickness. Usually the fine sandstone is fractured, and limonite stains are conspicuous. About 25 percent is composed of dark brown and black silt shale and mud- stone. Bedding planes commonly show fragments of char- coal, including some reed or rush material, although no recognizable leaves or other fossils were discovered. Upon Geology of the Lebec Quadrangle 13 weathering, these rocks break into small angular shards and chips which characterize the overlying soil. The re- maining 5 percent or so of the rocks consist of gray gritty and pebbly sandstone similar to the rocks on the east and south. Soft orange and white pebbly and gritty sandstone in beds 2 to 8 feet in thickness flank the canyon just north of Quail Lake School. Thin beds of hard, well-cemented, laminated, medium- and fine-grained sandstone are inter- calated with the pebbly sandstones and with soft light- gray medium- and fine-grained sandstone containing some dark brown concretions. Here and there are minor inter- beds of dark brownish-purple hard irregularly fissile silt shale, iron- and manganese-stained. Although most of the clasts in these rocks consist of granitic debris, a few purple quartzite pebbles, well-rounded, as well as bleached flow-banded rhyolite, were uncovered. At several localities near the center of the triangular sector mollusk frag- ments occur in brownish soft medium-grained sandstones, which can be traced northward toward the juncture of the two faults bounding the sector. Toward the top of this section the sandstones become more massive and irregularly bedded, even cross bedded and with scour channels. As these same rocks appear east of the aorth-SOUth fault they provide a basis for correla- tion across it although facies changes interfere with per- fect correlation. Rocks in the eastern sector, bordering Antelope Valley, consist predominantly of buff and white pebbly and cobbly sandstone with only minor thicknesses of siltstone and shale. At the south these beds are folded into several anticlines and synclines, but at the north an homoclinal section of about 3200 feet dips toward the north. The typical outcrop in this sector reveals white and buff cross-bedded and irregularly bedded conglomeratic sand- stone with a few granitic boulders up to 5 feet across. Con- cretionary zones and conspicuous limonite stains, particu- larly along joints, are common. In the main these rocks are porous and permeable although locally, as at the northern- most outcrop of the formation on the quadrangle, they are well cemented with lime derived in part from numer- ous fossils within the conglomerate. Clasts, angular to subrounded, consist predominantly of debris from a granite terrane (aplite, pegmatite, vein quartz, alaskite, and graphic quartz-orthoclase rock). In addition, light- purple porphyritic andesite, white bleached flow-banded rhyolite, and light gray quartzite occur. Red pebbly sandstones are exposed in the core of an anticline about a third of a mile north of Quail Lake and beneath the white pebbly sandstone just described. Sepa- rating the two is a thin unit of olive-drab thin-bedded soft silty sandstone and siltstone. The red beds extend out of the quadrangle toward the east and southeast and ap- parently belong to the Tertiary non-marine sequence described by Wiese and Fine. 19 As they underlie some of the upper beds they are presumably in part equivalent in age to beds west of the north-south fault. Mr. William II. Corey, who has studied the fossils from the Santa Margarita formation, has kindly provided the following list of the known megafauna : ALGAE calcareous (abundant) BRYOZOA sp. PELECYPODA Dosinia sp. (abundant) Ostrea titan cf. subtitan (abundant) Ostren sp. Pecten estrellanus variant (abundant ) Pecten ef.crassicardo'l Pecten raymondi Pecten (Amusium) sp. Glycimeris sp. GASTROPODA A sir ahum sp. Xtiti/a (Polinices?) sp. Oliva sp. ECHINOIDEA F.'h in ii roth n i its ijn li l> i Astrodapsis cf. bretoerianns Mr. Corey concluded that this fauna is very similar to that from upper Miocene beds in the Tejon Hills of the southern San Joaquin Valley and in the eastern Ventura and Ridge Basins. He also stated that though foraminifera were recovered from some of the dark shale beds, they were so poorly preserved that identification was impos- sible. ( Mi the basis of most of these species Wiese 20 concluded that the formation could be correlated with the Santa Margarita of limits -' at the southern end of the San Joa- quin Valley, In view of this, and particularly in view of the striking lithologic similarity of the beds at the two Localities, Wiese applied the same name to his unit, a prac- t ice followed here. Pliocene Series Peace Valley Beds. Greenish siltstones with inter- bedded sandstones lie beneath the Hungry Valley forma- tion in the southeastern corner of the quadrangle. These beds, of middle Pliocene age, are part of the thick non- marine section of Ridge Basin — well-exposed along U. S. Highway !»!» in Peace Valley for several miles south of the area. A formation name has not been given to these rocks 28 as the base of the section of similar lithology is not exposed in the areas so far studied. Only the upper 1500 feet of these beds crop out in the Lebec quadrangle whereas about 4,000 feet are present altogether in Ridge Basin. Peace Valley beds are exposed over an area of about a square mile in a strip along the southern border of the quadrangle near its southeastern corner. In general hills underlain by these rocks are subrounded with here and there outcropping sandstone ledges. At the heads of some canyons steep cliffs provide excellent exposures where amphitheaters have been eroded in anti-dip slopes. In view of the softness or incompetence of the beds, many landslides are found, particularly where the slopes are steep. The soft siltstones are frequently contorted where the dip is steep and folding intense. Two rock types, interbedded in variable proportions, make up the bulk of the Peace Valley beds in the Lebec quadrangle. Most conspicuous are white and buff poorly- sorted conglomeratic sandstones, in places massive, but locally in beds ranging in thickness from (i inches to 10 '» Wiese, J. H., and Fine, S. F., op. cit. 1950. « Wiese, J. II., op. cit.. 1950. s > Hoots, H. \V.. Geology and oil resources alone the southern border of San Joaquin Valley, California: U. S. Geol. Survey Bull. 812, PP. 243-332, 1929. , „ , a Eaton, J. E., Ridge Basin, California: Am. Assoc. Petroleum Geol- ogists Bull., vol. 23. pp. 517-558, 1939. "Crowell, J. C. Geology of Hungry Valley area, southern California: Am. Assoc. Petroleum Geologists Bull., vol. 34, pp. 1623-1646, 1950. 14 Special Report 24 or 15 feet. Intercalated with these rocks are greenish-gray and brown siltstones and mudstones, usually earthy and imbedded. Although these constitute over half of the sec- tion, their lack of resistance to erosion makes them far less conspicuous than the ledges of sandstone. The siltstones and mudstones, although usually without bedding, here and there are thinly bedded, and in some places are intercalated with thin discontinuous layers of fine-grained sandstone and shale. As a rule the fine clastic sediments are very poorly sorted, and many sand grains and a few grannies arc disseminated through the rock. Many of the associated thin sandstone and shale beds, in thin lenses up to an inch or so in thickness are very well sorted. Concretionary zones of white poorly sorted medium-grained sandstone constitute about 1 percent of the mudstone section. Joints with limonitic cement cross many of the outcrops, and where exposures are poor they can easily be confused with bedding. The white and buff conglomeratic sandstones are char- acteristically massive but with faint irregular lenses of sparse pebble conglomerate. Cross-bedding and scour channels, and abrupt changes in grain size and sorting, both normal and parallel to the bedding, indicate tor- rential deposition. These features are so irregular that it is quite difficult to determine the tops and bottoms of beds on the basis of these structures. Clasts contained within the conglomeratic sandstones are commonly subangular to subrounded, and ran^e up to several feet in diameter although pebbles are the most common. In the Lebec quadrangle the rock types repre- sented among the clasts are very little different from those in the overlying Hungry Valley formation. By far the most abundant are fragments derived from aplitic and pegmatite veins of a granitic terrane. These clasts, dominantly of quartz and feldspar with only minor amounts of other minerals, appear the same as the veins and dikes in the quartz monzonite underlying Liebre Mountain to the east. That at least part of them were eroded from this quartz monzonite is suggested by the presence of fragments of biotite-plagioclase rock, similar to the basic inclusions which occur in the Liebre quartz monzonite. Other rock types such as dark metavolcanic rocks, hard brown fine-grained sandstone, and gneiss, with unknown sources occur among the pebbles, but these make up probably less than 1 percent of the total. Bordering the exposure of quartz monzonite on either side of Highway 99 at the southern boundary of the quad- rangle is a coarse breccia within the Peace Valley beds. The deposit consists of angular blocks and boulders of quartz monzonite in a jumbled imbedded mass with a matrix of disintegrated quartz monzonite. The unit, up to 200 feet thick, was derived from the quartz monzonite against which it has been deposited, and clearly grades upward into the conglomeratic sandstone and siltstone of the Peace Valley beds. It probably accumulated as a talus deposit at the base of the quartz monzonite ridge in the middle Pliocene and Avas subsequently overlapped by upper Peace Valley units and the Hungry Valley formation. Units of the Peace Valley beds are lenticular and vary in composition and thickness along the strike. Upwards the beds interfinger and grade into the Hungry Valley formation ; the contact is drawn in the conformable sec- tion where predominantly mudstone and siltstone give way to predominantly conglomeratic sandstone. Toward the east, in the southeastern corner of the quadrangle, 'massive tongues of fanglomerate interfinger with the mudstone. D. T. Axelrod 2i has studied a collection of fossil plants from a Ridge Basin locality several miles south of the Lebec quadrangle and stratigraphically below the Peace Valley beds. He considers their age to be middle Pliocene. From nearly the same stratigraphic position, Lore Rose David -"' has described a fossil stickleback, closely re- lated to living fishes, which she believes is probably Plio- cene in age. As the Peace Valley beds lie stratigraphically above these two localities, and below the vertebrate locality in the upper Pliocene Hungry Valley formation, they also are assigned to the middle Pliocene. 20 Previous workers have dealt with these beds in a general way. Eaton 27 subdivided the Ridge Basin sediments into four "divisions," the third of which corresponds approxi- mately to the Peace Valley beds, and the fourth to the Hungry Valley formation. In addition, Clements 28 de- scribed briefly some continental Pliocene beds in the cen- tral Ridge Basin several miles to the southeast, which he named the Ridge Route formation. For several reasons these names have not been applied to the stratigraphic units at the northern end of Ridge Basin. 29 When the study of Ridge Basin stratigraphy has eventually been completed, Peace Valley beds may be found to be the same as the Ridge Route formation of Clements, in which case the latter name will have priority of usage, and the name Peace Valley beds may be discarded. Hungry Valley Formation. Non-marine white con- glomeratic sandstones with interbedded gray-green mud- stones, reaching a thickness of about 4000 feet, crop out across the Lebec quadrangle south of the San Andreas rift. These beds, the Hungry Valley formation of Pliocene age, conformably overlie the Peace Valley beds and are the youngest Ridge Basin sediments, but only the north- eastern part of the area of outcrop is in the Lebec quad- rangle. Fossil vertebrate remains, including fragments of horse teeth from a locality 600 feet above the base of the formation, indicate deposition in late middle or early late Pliocene time. 30 Although about 3500 feet of undated strata lie above the fossil zone, these beds are placed in the upper Pliocene also, as about 18,000 feet of lower and middle Pliocene strata occur beneath the zone. In the absence of fossils in the youngest Hungry Valley strata it seems reasonable to assume a roughly constant rate of Pliocene sedimentation in Ridge Basin; if so, and assuming further that the duration of the late Pliocene represents about one-third of Pliocene time, about 6000 feet of beds could have been laid down in the late Pliocene. Hence it is likely that the entire formation is Pliocene in age, although not impossible that the uppermost beds are. Pleistocene. 24 D. I. Axelrod, op. cit., 1950. 25 David, Lore Rose, A Neogene stickleback from the Ridge formation of California: Jour. Paleontology, vol. 19, pp. 315-318, 1945. 2 " Crowell, J. C, op. cit., 195 0. 27 Eaton, J. E., op. cit, 1939. 28 Clements, Thomas, Structure of southeastern part of Tejon quad- rangle, California : Am. Assoc. Petroleum Geologists Bull., vol. 34, pp. 1623-1646, 1950. 28 Crowell, J. C, op. cit. 1950. 30 Stock, C. B., oral communication. Geology of the Lebec Quadrangle 15 Strata of the Hungry Valley formation are exposed south of the Ran Andreas rift over most of the southern third of the Lebec quadrangle. Steep barren gullies sep- arated by sharp serrated ridges occur in the vicinity of Freeman Canyon, where the terrane underlain by the formation lias a badlands aspect with steep cliffs up to 300 feet high at the heads of amphitheaters. North of this region, however, and bordering the San Andreas rift on the south, the hills are in the main gently rounded with infrequent outcrops, and contrast markedly with the dis- sected badlands. In the Lebec quadrangle the Hungry Valley formation is composed of irregularly interbedded non-marine sand- stone, conglomerate, and mudstone. The sandstone and conglomerate beds predominate in the section, but on the east, south of Quail Lake, the relative proportion of mud- stone increases slightly to make up about one quarter of the formation. "White poorly-indurated sandstone with lenses of pebbly sandstone characterize the Hungry Valley formation. Beds range in thickness from a few feet up to about 50 feet, and are usually cross-bedded and sconr-channeled. Unless outcrops are particularly pood, the cross-beds and irregular bedding are easily confused with the true bed- ding. In addition numerous joints in the massive rocks in many places cemented with iron-stained material, simu- late bedding. In the main the Hungry Valley sandstone beds are arkosic, poorly sorted, and have a high proportion of clay and mud between the subangular sandgrains. Feld- spar and quartz, with minor amounts of rock fragments, and rare hornblende and biotite make up the bulk of the rock. The composition of the grains, confirmed by that of the pebbles, discussed below, indicates that the sandstone was derived primarily from a granitic terrane. The larger fragments in the sandstones, which range in size from granules up to small boulders, are character- istically scattered through the sandstone and only here and there concentrated into pods and lenses without strongly demarcated boundaries. Not infrequently, indi- vidual clasts are surrounded by large amounts of sand- stone; in other outcrops, the clasts predominate and the rock becomes a true conglomerate. In respect to size of clasts, almost any outcrop of Hun- gry Valley sandstone will yield many granules and several pebbles. Locally pods of larger clasts prevail, with cobbles up to several inches in diameter standing out conspicu- ously, but with far more pebbles and granules actually present. In a few places, such as at the head of Freeman Canyon in some of the basal units of the upper member of the formation, cobbles predominate, and here and there boulders up to 2 to :? feet in diameter are present. Many of the exposures of coarse conglomerate in these higher stratigraphic units are very angular and consist of im- bedded rubble and breccia which show little evidence of current sorting. The clasts are in the main subrounded to subangular, with here and there some well-rounded or very angular. Usually there is a correlation between the rock type and the shape and rounding of the fragment. Quartzite clasts are commonly rounded, suggesting derivation from an older conglomerate, and those of aplite, limestone, and hornfels subangular, and were probably washed in di- rectly from their source area. Some conglomerate beds in the formation, especially in the lower strata, consist of many rock types; others, espe- cially in the upper member, consist of few. Conglomerates like the former with many types are called polymictic, those with few, oligomictic. 31 In the polymictic conglomerates granitic pebbles usually make up about a third of the clasts. Most are white and pinkish aplite and pegmatite, composed of feldspar and quartz with less than 5 percent of other ferro-mag- nesian minerals. Interlocking and graphic textures are characteristic, with pegmatitic texture very common. These clasts have been transported from a granitic terrane and represent the more resistant parts of a parent plu- tonic body. The bulk of the granite apparently disinte- grated upon weathering to form the sand grains of the formation whereas the aplite and pegmatite veins in the granite give rise to the clasts. These and other rock types represented are tabulated below : Approximate percentage Rock typo Brief description 20-50 Granitic Aplite, pegmatite: Gray, pink, quartz-feld- spar rock ; sco text. 0- 5 Andesite Purple, porphyritie, up to 40% plagioclase phenoerysts, aphanitic groundmass, flow structure. 0- 5 Andesite Cray-green, porphyritie, up to 5% plagio- clase phenocryts, aphanitic groundmass, flow structure. 0-10 Rhyolite Cream-colored, gray, mottled, sparse pheno- erysts of feldspar, faintly flow-banded, often bleached, often tuffaeeous. 0-20 Gneiss Brown, thinly handed, quartz plagioclase biotite gneiss; some fragments of schist. 0-20 Quartzite Cray, purplish, vitreous, pure hut with some iron-staining; some have sugary tex- ture. Characteristically well-rounded; some "rotten" and easily broken. 0-1.") Hornfels Dark brown, gray, hard, fine-grained, re- crystallized sandstones, siltstones, and shales. Some calc-silicate hornfels. 0- 5 Limestone White, crystalline, pure, medium- to coarse- grained. Some marble, with flecks of graph- ite, epidote, garnet. 0- 5 Quartz White, milky, rein quartz. 0- 5 Basalt or Dark-brown to blackish, non-porphyritic, andesite aphanitic. Proceeding upward in the formation, the great variety of rock types represented among the clasts gives way to fewer and fewer types. In the upper oligomictic member of the formation metamorphic clasts predominate, in- cluding fragments of gneiss, amphibolite, schist, and similar rocks from the terrane southwest of the San ( iabriel fault zone. In addition, larger proportions of lime- stone with calc-silicate hornfels, derived from the lime- stone roof remnants now lying north of the San Andreas rift, make their appearance. ( >n the east, south of Quail Lake, there is great variation in the composition of the clasts. At one outcrop, quartzite cobbles and pebbles predominate; at another, the debris consists almost entirely of aplitic and pegmatitic material. Here, too, fragments of volcanic rocks are conspicuous. In summary, the composition of the Hungry Valley clasts sutr-'ests that the bulk of the material was derived s» Pettijohn, F. J., Sedimentary rocks, Harper and Brothers, New York, 526 pp., 194U. 1() Special Report 24 Quail Lake—, Liebre Mountain r-East border of Lebec quadrangle San Andreas rift-j ««*■& vm&; Figure 6. Southeast corner of Lebec quadrangle, showing overlap of volcanic rocks and granite by conglomerate of the Santa Margarita for- mation. Tsmcg = Santa Margarita conglomerate; Tv = Miocene (?) andesite Hows; Jgt = Tejon Lookout granite. Taken from just west of powerline on ridge with German triangulation station upon it. from a granitic terrane, but that from time to time, large quantities were contributed from terranes of other compo- sition. On the west, and in the higher parts of the forma- tion, gneiss, schist, and amphibolite fragments were washed in from southwest of the San Gabriel fault zone. In the main, however, tnost of the material probably came from the east, northeast, and north, since in those direc- tions lay expanses of granite, with associated roof pend- ants of limestone and hornfels. Volcanic rocks, some simi- lar in composition to the elasts, are exposed in the southern part of the Neenach quadrangle 32 and on eastward north of the San Andreas rift. Older sedimentary rocks con- tributed material, such as the rounded quartzite elasts from an older conglomerate, but these source areas are no longer recognizable. The greater variety of rock types in the lower parts of the formation suggests that erosion in the northeastern source area may have worked down 3 -Wiese, J. H., op. cit, 1950. through older sediments as time passed, and cut more and more into the underlying granite and metamorphic rocks. Mudstone, with minor amounts of siltstone and shale, is interbedded with the conglomerate and sandstone. They are usually poorly sorted, gray, greenish, or brown, with many disseminated sand grains and granules. Bedding or fissility is lacking in many places, but locally the finer elastics are better sorted, and shale and siltstone is interbedded. The mudstone layers are commonly 2 to 25 feet in thickness, whereas the shales and siltstones, usually less than 6 inches thick, are interbedded with con- glomeratic sandstone and not with the mudstone. Judging from these characteristics, as well as from the position of the possible source areas, it seems likely that the formation accumulated as a fanglomerate, near the distal ends of coalescing alluvial fans reaching from the north, east, and west. Mudflows and running water probably were the chief transporting agents. Geology of the Lebec Quadrangle Quaternary System Pleistocene Series Terrace Deposits. Undeformed gravels, sands, and silts cap low ridges at the western tip of Antelope Valley north of Quail Lake and at many other places within the quadrangle. The deposits unconformably overlie all other formations within the area and have been detectably tilted and faulted within the San Andreas fault zone only. In general their distribution is clearly related to the pres- ent stream courses, although north of Quail Lake they probably accumulated as a small piedmont when base level was significantly higher. In this region the deposits reach their maximum thickness of between 100 and 150 feet. The terrace deposits consist of poorly sorted gravel and rubble in a dark-brown earthv matrix. A massive struc- - Figure 7. Conglomeratic sandstone of Santa Margarita formation. Powerline road near German triangulation station. r \ r 17 . *'-1t--* Figure 8. Shale and siltstone <>f Santa Margarita formation. Pow- erline read near German triangulation station. Figure 9. Rubble <>f quartz monzonite clasts in Peace Valley beds. West of 1'. S. Highway '.»'•> just north of south border of Lebec quadrangle. ture, with indistinct bedding, is characteristic although here and there indurated lenses are conspicuous. Most of the gravel consists of angular and subangular fragments from the terrane lying upstream from the deposits. The dark-brown color, the unsorted earthy matrix, and the composition of the fragments serve to distinguish terrace sediments even where the topographic form of the deposits is obscure. As the terrace deposits were laid down after the region had been deformed by the mid-Pleistocene diastrophism, they are assigned to the upper Pleistocene. They are the only rocks in the quadrangle which cross the San Andreas rift, although along it they have been cut and broken. Because they have been disturbed by this fault movement, and in addition now stand high (up to 200 feet) above some of the present streams, they are considered late Pleistocene and not Recent in age. Recent Alluvium Large parts of the low-lying valleys are receiving detri- tus from the surrounding hills. This material, mapped as alluvium, consists of poorly sorted and unconsolidated silt. sand, and gravel and has not been deformed techni- cally except along the course of the principal fault within fhe San Andreas rift. Deep soil has developed on the alluvium at places but everywhere it contains fragments of rocks from the nearby terrane. STRUCTURAL GEOLOGY The principal structural features of the Lebec quad- rangle are the San Andreas, (iarlock, and Pastoria faults zones, which divide the quadrangle into four sectors. The plutonic rocks between the faults, broken into blocks of massive rock, some small and some large, have been de- formed chiefly by slight movement on fractures with slickensides, gouge and breccia. Sedimentary rocks have been folded and faulted accompanied by much move- ment alone bedding planes and by crumpling of incom- petent strata. 18 Special Report 24 .'?f lower Hungry Valley formation. Note discontinuous beds, due mostly to differential movement during deformation. U. S. Highway 91) roadeut half a mile north of south border of Lebee quadrangle. Faults San Andreas Fault Zone. The southern part of the Lebec quadrangle is crossed by the San Andreas fault zone which separates Ridge Basin sedimentary rocks on the south from the Tejon Lookout granite and overlying andesite flows and Santa Margarita formation on the north. The fault zone as a whole, which is as much as a mile wide, has a course of N. 70° W., although individual faults within the zone may depart considerably from this strike. Several subparallel faults with long arcuate traces on the surface make up the zone and separate thin narrow slivers of rock, usually about ten times as long as wide. The topographic sulcus or rift corresponding with the San Andreas, and the landforms due to recent movement, are conspicuous along its course. In the Lebec quadrangle, a principal fault with a rela- tively straight course and upon which there has been recent movement, lies within the San Andreas zone. That this fault is younger than some of the others is clearly shown between Holland Summit and Gorman, where it lies at the foot of the steep ridge. Here it has truncated the earlier faults on the north which intersect it at angles between 10 and 40 degrees. Just north of Highway 99, it is marked topographically by a small scarp. Between Gorman and the intersection of Highways 99 and 138, where it passes through marshy terrain, its course is not clear, but eastward to the edge of the quadrangle it can be traced easily. To the northwest, beyond the limits of the quadrangle, it can be followed for several miles although east of the town of Frazier Park it splits into several branches. Despite the fact that this central fault appears to have a remarkably straight course in comparison with the branch faults on either side, its trace on the map is slightly undulatory. Considering north as "up," there is a trough near Holland Summit, a crest near the inter- section of Highways 99 and 138, and a slight trough near the small sag pond about lj miles from the highway intersection. From this point on eastward, the undula- tions are not conspicuous. Whether they are significant, Geology of the Lebec Quadrangle 19 or characteristic of the San Andreas fault elsewhere, must await further detailed work along the fault. Xote, how- ever, that in the western Lebec quadrangle the conspicuous sliver zones occur in the concavities of this principal fault. The area of fault slivers northwest of Gorman and north of the fault, for example, is in a trough. A similar position is suggested for the sliver area east of the inter- section of Highways 09 and 138. The granodiorite thrust plate on the south wall of the zone is in a crest. At three places along the San Andreas fault zone, an unusally large number of these slivers are present side by side. Northwest of Gorman, in a fusiform area 7000 feet long and 2000 feet wide, sixteen slivers have been mapped. Rocks in this area are highly fractured and broken and no doubt other faults are present, but only those which separ- ate different rock types are shown on the geologic map. Most of the fault planes within this /.one are nearly verti- cal or dip steeply. The spindle-shaped plan view of the area on the map. being broader at the surface than the average width of the fault zone, and the fact that most of the faults converge toward the principal fault in plan view, suggest narrowing with depth (see cross section AA. plate 2). At some places along the San Andreas, as near Quail Lake School and locally along Highway 138, faults which cut alluvial and terrace surfaces are mapped, and shown as solid lines on the geologic map. This means thai the faults depicted are chiefly of two kinds: those that separate different rock types, and those which break ter- race and alluvial surfaces. A similar but smaller area lies on the north side of Highway 138, about 3000 feel cast of its intersection with Highway 99. Although here the pattern of tin' faults is about the same, the diversity of rock types is lacking and most of the slivers consist of andesite. Southwest of the intersect inn <>f Highways 99 and 138, crushed granodiorite, with blocks of limestone, has 1 n thrust over the sandstone and conglomerate of the I [ungry Valley formation. In addition In the main thrust mass. two small klippen have been recognized on the west. It ap- pears likely that the small thrust has its roots within the fault zone and that during movement mi the San Andreas the comminuted granodiorite was squeezed from between the two walls. Perhaps, however, the thrust mass owes its present position in part to landsliding. South of Quail Lake is another area of many fault slivers. Here the subparallel faults separate blocks of Hungry Valley and terrace sediments, although some near the principal course of the San Andreas are marked by scarps cutting across terrace surfaces. In the field this area e'ives the impression of being much more faulted and broken than can be depicted on the geologic map. As beds cannot be followed more than a few feet, even where expos- ures are good, and as bedding is jumbled, and gougey shale and slickensides common, perhaps the incoherent sediments have been stripped from the basement rucks beneath and deformed independently. Xo conclusive evidence on the direction and amount id' movement on the San Andreas, or on its age, has come to lieht as the result of this study. The problems are still outstanding and remain among the most perplexing and significant in the geology of California. Mapping in the Lehec quadrangle shows, however, that the San Andreas is a fault of large displacement and great structural sig- nificance. Factors leading to this conclusion are discussed below. The San Andreas fault zone separates granite with roof remnants of metamorphosed sediments on the north from Ridge Basin sediments underlain by quartz monzonite on tin- smith. Roof rocks on the south, metamorphosed during emplacement of the quartz monzonite, must have been re- moved by i\ci'\) erosion before deposition of the Ridge Basin sediments. If simple dip-slip movement is assumed for the San Andreas fault, these relations imply that the southern block stood high relative to the northern block for a long time, so that erosion could cut deeply into it. This involves upward movement on the south. The preser- vation of the Ridge Basin sediments on the south, how- ever, which have since accumulation been downfaulted so that their contact with basement rocks lies several thou- sand feet beneath the surface at the San Andreas rift, im- plies downward movement on the south. These arguments therefore lead us to postulate a reversal in the direction of movement on the rift of several thousand feet, if simple dip-slip displacement is adhered to, first up on the south, then down on the south. Strike-slip movement, measured in many miles, might explain these relations, but mapping far beyond the limits of the Lehec quadrangle will be necessary to cast Hgh1 on this possibility. Future work may disclose the offset portions of the Lebec quadrangle rocks, although as yet they have not been recognized. Do the rock types represented in the fault slivers pro- vide information on the kind and amount of displace- ment .' I lertainly the large number of slivers, the quantity of gouge and breccia, and the width of the fault zone all point toward a large displacement. Only one rock that occurs in the slivers, the crushed p ra nodiorit c, is not now found in the wall rocks adjacent to t he fault, and its source is unknown. Purple andesite. lithogically similar to that lying on Tejon Lookout granite at the east, occurs in the fault zone at least as far as the western edge of the quadrangle, ~> miles from its apparent source. Although the slivers may have been dragged to their position near Holland Summit by strike slip movement of about 5 miles, the flows may have lapped much farther westward on the Tejon Lookout granite before removal by erosion. II' so. dip-slip movement could have dropped them into the fault zone. Much more detailed mapping along the San Andreas fault is required before iis displacement can be deter- mined. There is no doubt that the San Andreas fault in this quadrangle has moved very recently as shown by the rift topography hardly modified by erosion. The antiquity of the fault, however, is problematic. An age as old as Mio- cene is implied since the San Gabriel fault, which borders Kid Lie 1 '>asin on the southwest, was in existence in the Mio- cene. ;:; This fault, which probably abuts against the San Andreas today beneath the Frazier Mountain thrust west of the Lehec 1 1 ii ad ra n l; le, has not been recognized to the north, implying that in the Miocene epoch it also joined the San Andreas or was a member of ancestral San Andreas system. The lack of data mi tl riginal distri- bution and lithology of upper Miocene and Pliocene sedi- ments in the region prevents comment on whether the San Andreas zone was a factor in defining their basins of • ; lOaton, J. i: . op. cit, 193fl. ( irowell, .1. <'., op. cit., 1050. 20 Special Report 24 deposition. Within the quad ran pie the distribution of basement rock types only requires that the fault lias moved previous to the deposition of the Hungry Valley formation. Garlock Fault Zone. The northwestern part of the Lebec quadrangle is crossed by the < Jarlock fault zone near its terminus at the San Andreas fault zone a mile and a half vest of the quadrangle. About Qi miles of Hie fault, which has a strike of N (i()° E, is exposed, although the fault can be followed on eastward as far as the northern end of the Avawatz Mountains, south of Death Valley, about 175 miles from the San Andreas. 34 Evidence in hand to date, and discussed by Hulin, 3,1 Nolan :! ' ; and Wiese :;T suggests that movement on the Garlock fault has been principally horizontal (left lateral) of the order of many miles — perhaps as much as 25. Recently, Dibblee and Hill ss have described the Big Pine fault, southwest of the San Andreas, which has many features in common with the Garlock. It may be the Garlock fault, offset along the San Andreas, or a fault, never continuous with the Gar- lock, but genetically related and caused by the same strain system in the crust. Terrane northwest and southeast of the fault is similar, consisting of plutonie rocks with roof remnants of lime- stone. However, as the Lebec quartz monzonite is appar- ently underlain by a major thrust, at depth the Garlock may separate the diorite constituting the footwall of the thrust from the Tejon Lookout granite and its associated limestones. Because little is yet known about the original distribution of these rocks, no conclusions on the manner of movement of the Garlock fault have come from this study of the Lebec quadrangle. That it has not moved recently in this area, however, is clearly shown by the fact that neither the alluvium nor the terrace deposits have been offset by the fault. In this respect, at least, the fault differs from the San Andreas, although Hulin 30 noted that the fault has displaced terrace deposits in the El Paso Mountains northeast of Mojave. The congruency of Castaic Valley and the canyon northeast of Castaic Lake with the course of the fault is a secondary feature, owing to selective erosion along the weakened rocks of the fault zone. Half of the course of the Garlock fault in the Lebec quadrangle is beneath alluvium of Castaic Valley, so de- tails along the fault can be observed only near the northern boundary. Here the zone consists of several sub- parallel faults separating slivers of Tejon Lookout granite and Lebec quartz monzonite in association with elongate sheared and recrystallized masses of marble with minor amounts of schist. These masses of metamorphic rocks, streaked out along faults, are very helpful in working out details in the fault zone. Wiese, 4 " who described similar masses in the Neenach quadrangle, explained their pres- ence as follows: strike-slip movement on the fault would result in local areas of tension permitting sliverlike grabens of limestone to descend between the two fault 34 Jenkins, O. P., Geologic map of California : California Div. of Mines, 1938. 35 Hulin, C. D., op. cit., 1925. 86 Nolan, T. B., The Basin and Range province in Utah, Nevada, and California: U. S. Geol. Survey Prof. Paper 197, pp. 141-196, 1943. 37 Wiese, J. H., op. cit., 1950. 38 Dibblee, T. W., Jr., and Hill, M. I,., Big Pine fault, California (ab- stract) : Geol. Soc. America Bull., vol. 59, p. 13C9, 1948. 80 Hulin, C. D., op. cit., 1925, p. C4. 10 Wiese, J. H., op. cit., 1950, p. 40. walls, and with continued horizontal movement these blocks would be mashed, sheared, and recrystallized. In the Neenach quadrangle "' the Garlock fault is shown to consist of two branches nearly a mile apart, with a strip of Pelona schist ( pre-Cambrian .' ) between them. Tn the southeastern corner of the Pastoria Creek quadrangle these two branches converge and pass beneath the Pastoria thrust. Where last in view at the surface, the band of schist is 1700 feet wide. Pastoria Thrust. The northwestern corner of the Lebec quadrangle is crossed by faults of the Pastoria thrust zone which bring Lebec quartz monzonite on the south over School Canyon granite and diorite on the north. The thrust system is named for exposures in the middle fork of Pastoria Creek-, northwest of the Garlock fault, in the southeastern corner of the Pastoria Creek quad- rangle. Here the thrust dips 20 or 30 degrees to the south, although it apparently steepens near the Garlock. The ridge just northeast of Pastoria Creek is a klippe of com- minuted and cataelastic Lebec quartz monzonite, lying on gneissose diorite. From this locality the thrust can be traced westward across the southern part of the Pastoria quadrangle and into the Lebec quadrangle, where three faults make up the zone. To the west it crosses Grapevine Creek and Highway !•!) at the mouth of O'Neil Canyon, where the General Petroleum Corporation maintains a pipeline pumping station. In the Lebec quadrangle the principal branch of the Pastoria thrust trends along the southern slopes of School Canyon, where it brings Lebec quartz monzonite over diorite with many slivers of limestone, cataelastic quartz monzonite, and minor amounts of hornfels and schist within the thrust zone. Here the zone apparently dips about :i() degrees to the south. East of the exposure of School ( Janyon granite, where the fault crosses the canyon, relations are obscure. Tt may continue on eastward to meet the Oarlock fault, but, if so, it has not been recog- nized, as quartz monzonite is thrust on quartz monzonite, and outcrops are rare. In School Canyon, however, two north-south faults bounding the granite body, both with a steep easterly dip, apparently converge to form one fault and swiii"' eastward in the southern part of the Pastoria Creek quadrangle. This fault, bringing quartz monzonite over diorite, is the main Pastoria thrust, exposed in the middle fork of Pastoria Creek. More mapping in the region will be necessary before further characteristics of the faults can be worked out. Other Faults. North of the San Andreas rift, between Oso Canyon and Quail Lake, are several high-angle faults. The German fault, given this name because it passes through the triangulation station of German on the map, dips eastward very steeply. As it drops Santa Margarita shales and sandstones down against the basal member of the formation, it is apparently a normal fault. Note that the German fault is nearly parallel to the Garlock and to faults shown by Wiese in the Neenach quadrangle 41 and is therefore probably genetically related. Another normal fault, dipping eastward, trends north and intersects the German fault at its north end. The western tip of Liebre Mountain, which barely reaches into the southeastern corner of the quadrangle, is 11 Wiese, J. H., op. cit., 1950. Geology of tiil Lebec Quadrangle 21 faulted on both its northern and southern margins. The southern thrust moved principally before the deposition of the Hungry Valley formation as it passes beneath it. Where exposed at the surface, at the southern border of the quadrangle, it thrusts quartz monzonite southward over Peace Valley beds and dips northward about 60 degrees. The thrust on the north, which dips steeply south- ward, brings quartz monzonite over Hungry Valley sand- stones, and has apparently moved more recently than the southern thrust, and may be a part of the San Andreas system. These two faults presumably converge at depth (»n the west; the southern may extend northwestward to meet the San Andreas fault, but beneath the Hungry Valley beds at the surface. Another subsurface fault probably trends along the southern boundary of the quadrangle, bordering on the south the anticline with quartz monzonite at its core, as in- dicated by the hand of coarse granitic rubble in the Peace Valley beds. The rubble is interpreted as a talus deposit at the foot of an escarpment, perhaps caused by a fault now buried. Structures in the southeastern corner of the quadrangle indicate continuous or i nt e run t tent movement during the late Tertiary and Quaternary, in part during the deposition of Peace Valley and Hungry Valley beds. Folds All the unmetainorphosed sedimentary rocks in the Lebec quadrangle are folded, having trends subparallel or en echelon to the major faults. The anticline astride Highway 99 at the southern border of the quadrangle has a core of Liebre quartz monzonite, infolded with the sediments. Exposures of the granite show a large number of sheared joints and gouge zones along which adjustment between blocks of the massive plutonic rock presumably took place during folding. Be- cause the outcrops show the same degree of shearing and brecciation as the granitic rocks elsewhere in the area where sedimentary rocks have been stripped away by ero- sion, it seems likely that the plutonic rocks elsewhere were also folded. GEOMORPHOLOGY The diversity of rock type and structure in the Lebec quadrangle has been responsible for a great variety of landforms. In addition, the complicated tectonic history of the region in Pleistocene and Recent time has left its imprint upon the topography. Nevertheless, all of the physiographic features now observed originated since the mid-Pleistocene. The tectonic events were important pri- marily in bringing about the present distribution of rock types. Erosion, operating differentially and selectively on the hard and soft rocks of the Pleistocene mountains, has been chiefly responsible for the present physiography. But diastrophic events, still active today, have been in- strumental in directing the course of this erosion, chiefly by means of regional tilting and its control on the position of base level for the present day streams. Several well-developed old erosion surfaces and many prominent terraces are conspicuous in the quadrangle. The highest of the distinct surfaces is the summit upland surmounting the western Tehachapi Mountains, the ridges north of Castaic Lake, and ridges extending southward into Ridge Basin. Remnants of this surface, characterized by gently rolling topography of low relief, are well marked north of the Tejon Lookout, along the Edison Company transmission line and service roads where they cross the mountains, and in the vicinity of the Airway Beacon near the northern border of the quadrangle. The lowest eleva- tions on this surface north of the San Andreas rift are now at about 4 '_'.">() feet above sea level, but rounded sum- mits stand as much as 1500 feet above this. The highest of these hills surmounting the old surface of the Tehachapi .Mountains are limestone which is more resistant to erosion than the surrounding granite in the semi-arid climate of the region. In fact, there is such contrast in resistance to erosion between the two rock types, that the contact be- tween the two often forms a marked topographic break on this old surface, where the gentle surface of the granite meets the steeper and more rugged limestone terrane. Judging from the slope of the surface remnants, drain- age appears to have flowed to a trunk stream along the Garlock and northeastward out of the area. South of the main divide along the axis of the Tehachapi Mountains, drainage reached both the Mojave Desert on the east, and Pirn Creek and the Santa Clara River on the south. Ridges in Ridge Basin arc capped with terrace surfaces, some of which have gravel still upon them. The prominent terraces on the east flank of Frazier Mountain, west of Holland Summit and the quadrangle boundary, were once parts of this surface. Prominent terrace surfaces, lower than the summit up- land just described. Hank the Tehachapi Mountains north id' Quail Lake and south of the San Andreas rift west of Quail Lake School. The surface has an elevation of about 3800 feet where it i ts the foothills and slopes gently basinward. Most remnants overlie thick accumulations of terrace debris which lie in turn on a fairly even, basin- ward-sloping surface cut on the older rocks. Near the Kern County-Los Angeles County boundary at the east edge of tin' quadrangle, this lower surface is exposed and is now being regraded by streams. As it is cut in bedrock, and lies as an apron extending between streams courses, it probably represents an exhumed pediment. The cut surface in the bedrock, the accumulation of gravels above, and the graded surface on top can all be explained as results of pedimentation and consequent alluviation in connection with a rising baselevel east of the quadrangle. At the time of the maximum extent of the upper terrace surface it reached across the San Andreas and extended southward into Peace Valley. Drainage in the northwestern part of the quadrangle now flows down Grapevine Creek from Castaic Valley. At the time of the development of the summit upland, how ever, as described above, a trunk stream flowed along the zone of rocks weakened by the Garlock fault and out of the quadrangle to the northeast. This stream was cap- tured by Pastoria and Grapevine Creeks, working head- wards in steep gorges from the San Joaquin Valley far below to the north. As most of the drainage in the old northeast-flowing stream came from the west. Grapevine Creek inei-eased its flow markedly with this capture, and became one of the principal streams in the region. The alluviation of Castaic Valley may be due to clamming by a large landslide .just northwest of the quadrangle in Grapevine Creek, or to a decrease iii discharge in Cuddy Creek, bringing in drainage from far to the west. If the 22 Special Report 24 headwaters of Cuddy Creek were captured, discharge would be insufficient to move alluvial debris brought down to the stream by tributaries just west of the Lebec quadrangle. This would choke the canyon and cause the eastward building of the broad alluvial fan in Castaic Valley. As the fan crowded into the mouth of the canyon northeast of the valley, a depression was formed, making the site of Castaic Lake. A modified version of this fan- crowding explanation was suggested by W. M. Davis. 42 Topography Along the Sun Andreas Eift. The San Andreas fault zone, locally up to a mile wide, occupies a topographic sulcus frequently referred to as the San Andreas rift. This depression or groove is conspicuous along the course of the fault in the southern part of Cali- fornia, and although it crosses in turn through valleys, foothills, or over shoulders of rugged mountains, it is everywhere a distinct and recognizable topographic fea- ture. The groove owes its existence to the ease with which the smashed and broken rock along the fault is eroded. Tn contrast to the relatively resistant rocks adjacent to the fault zone, debris within the rift is easily weathered and eroded so streams cut their courses headward in the crushed rock. The principal topographic expression of the San Andreas, therefore, is due to this cause and is not directly due to either the kind of displacement on the fault nor to the relative recency of this movement. Recent movement on the fault, however, has caused an array of minor topographic features which lie within the sulcus. Topographic features due to recent movement along the San Andreas are of several kinds. Fault scarps be- tween 5 and 10 feet high, which cut alluvium, may be seen between Holland Summit and Gorman and inter- mittently along most of the extent of Highway 138. These scarps truncate the steep alluvial cones reaching valley- ward from the ridge north of the rift, and only at a few places have gullies succeeded in notching it. Locally scarps face northward, as at the sag ponds east of Quail Lake School and about 1] miles from the intersection of Highways 99 and 138, which have here caused the ponding of the surface water. Because some scarps face north and some south, appar- ently along the same fault, strike-slip movement is sug- gested. Uneven topography cut along a fault and then displaced horizontally would give rise to the scarps; for example, a hill on the north offset to a place opposite a valley on the south results in a south-facing scarp. The small sag pond west of Quail Lake School is on a depressed sliver between two facing scarps. South of Quail Lake many fault scarps can be mapped, although it is fre- quently difficult to separate them from landslide scars. Depressions along the San Andreas rift, a few occupied by ponds, are of several types. Some, such as the small one west of Quail Lake School, are true sag ponds, represent- ing water accumulated in depressed blocks. Others, like the sag pond If miles east of the intersection of High- ways 99 and 138, are caused by ponding where a scarp has risen across a stream course. Still others, like the alluvia-ted depression south of Gorman, apparently were caused by landslide damming. Here a large composite landslide south of the rift near the intersection of High- ways 99 and 138, dammed the upper part of Peace Valley. "Davis, W. M., The lakes of California: California Div. Mines Rent. 29, p. 223, 1933. In addition, depressions along the rift have formed in at least two other ways, although they are not large enough to show on the contour map. A shallow swale has been ' formed by warping of the alluvial surface southwest of ] Quail Lake School and several depressions behind land- , slide masses occur south of Quail Lake. At one place west of the quadrangle an alluvial fan building into a depressed area has blocked off a small depression on its flank. Ponds occurring along the rift therefore have diverse origins and not all are true sag ponds. Similar topographic manifestations of recent movement do not occur along the Garlock fault in the Lebec quad- rangle. Although the fault zone lies within a topographic sulcus, again due to weak resistance of the rock to erosion, drainage along and across the fault zone is completely integrated and there are no closed depressions. Offset stream courses and elongate ridges in and near the fault can all be explained by selective headward erosion of streams in zones of weak rock. About a dozen landslides are shown on the geologic map although a great many more are in the area. Most of them have moved recently and thus possess clearly defined topographic forms characteristic of landslides, but others are older and have been very much modified by erosion, j Certain formations or beds are more subject to land- ; sliding than others. In Freeman Canyon several large l landslides have developed in gently dipping silty sand- : stone beds interbedded with the coarse white conglomer- atic sandstone of the Hungry Valley formation. Along | the San Andreas rift, where landslides are particularly [ noticeable, on steep slopes, recent slides, many of which ! are still in motion, are most conspicuous. One of these, southwest of the intersection of Highways 99 and 138, consists of at least three slides superimposed, the smaller slides moving on top of the larger. The rock at this locality consists of a fault breccia primarily composed of comminuted granodiorite and containing small limestone inclusions, which, with water, readily forms a plastic and mobile mass under gravity. Several other similar slides are along the rift. South of Quail Lake many landslides and fault scarps are intimately associated. Recent movement on branches of the San Andreas has resulted in oversteepened slopes, with true fault scarps, which have then slid downhill to , the north. Here it is difficult to separate landforms due to faulting from those due to landsliding; if an escarp- ment crosses two or more ridges and thus includes slopes bounding more than one stream course, it is considered to be a fault scarp. MINERAL RESOURCES No petroleum or mineral deposits of value have been discovered in the Lebec quandrangle although the accessi- bility of the area has led to considerable prospecting. Chief economic interest in the region has been a search for tin deposits in the limestone of the Tehachapi Mountains. Metals Four prospect pits shown on the geologic map have been sunk in limestone in the northeast part of the quad- rangle in an effort to discover metalliferous deposits of value but at the present time none of these prospects is being developed. Since the geology and mineralogy at Geology of the Lebec Quadrangle 23 these sites lias been studied in detail by Wiese and Page, 43 they need only be reviewed here. Most of the tin produc- tion has come from the Meeke Mine in the Neenach quad- rangle on the east. According to them, traces of tin, zinc, copper, silver, and iron have been obtained from these pits. The minerals bearing these metals occur in deep red brown tactite or gossan in the Paleozoic ( ?) limestones very near the contact with Tejon Lookout granite. These relations indicate that the tactite bodies were formed during the emplacement of the granite, probably during the Jurassic or Cretaceous period, in connection with contact metamorphism of the limestone. Petroleum No wells have been drilled for petroleum within the Lebec quadrangle although two dry holes have been put down just outside of the boundaries. In 1920 the Tejon Ranch Oil Company Tejon \'o. 1 was drilled to 2163 feet in the northwestern coiner of see. 13, T. S X., R. IS \\\. which places it 1 mile north of Quail Lake. Although it has been reported thai the bottom of the well is in granite, which cannot be verified from the log, it presumably penetrated only beds of the Santa Margarita formation. According to the driller's log "sandy shale showing colors and tar" was encountered between 646 and 648 feel and "sand showing tar" between 1275 and 127G feet. Neither surface seeps nor oil sands were noticed in connection w ith the present field work. In 1948 and 1949 the Tine ( !anyon Oil Company drilled its Davidson No. 1 to 2726 feel in the southwestern part of sec. 26, T. 8 X., R. Is \V„ .just outside of the southern boundary of the quandrangle where crossed by the Edison Company transmission line. The well penetrated a section of siltstone, sandstone, and conglomerate of the Peace Valley beds on the flank of an anticline that has granite at its core on the surface about a quarter of a mile to the west. No shows of oil were reported, and no evidence was found that the well reached marine strata. As the non- marine Peace Valley and Hungry Valley beds lie upon basement granite between the well-site and just west of Highway W. it is doubtful that oil reservoirs will be found in the vicinity. Limestone Although much of the Paleozoic (') limestone in the northeastern part of the quadrangle is impure and con- tains considerable iron, magnesium, and aluminum, beds and lenses of relatively pure limestone many feet thick occur here and there. In the future, when the inaccessi- bility of the deposits is of less economic i in port a i ice than today, the limestone may warrant consideration by the cement industry. Extensive sampling would be necessary to prove its suitability. REFERENCES Anderson, K.. Preliminary report en the geology and possible oil resources of (lie south end of the San Joaquin Valley, California : U. S. Geol. Survey Bull. 471, pp. 106-136, 1912. Axel rod, I ). I., The Piru Gorge flora of southern California : Carnegie Inst. Washington I'nlil. 5!M), V, pp. 159-21 I. 1950. Blake, W. 1'.. Geological report: I". S. Pacific U.K. Expl., vol. 5, pi. 2, pp. ls.",7. "Wiese, .1. II , and I 'am-, I,. R., Tin deposits of the Gorman district, Kern Countj , California : California Div. Mines Rept. 42, pp. :: \-:<2, 19 10. Clements, Thomas, Structure of southeastern part of Tejon quad- rangle, California : Am. Assoc. Petroleum Geologists Bull., vol. 21, pp. 212-2:52, 1937. Crowell, J. ('., Geology of Hungry Valley area, southern California : Am. Assoc. Petroleum Geologists Bull., vol. 34, pp. 1623-1646, 1900. David, I.. Rose, A Neogene stickleback from the Ridge formation of California: Jour. Paleontology, vol. 19, pp. 315-318, 194:,. Davis. W. M., The lakes of California : California Div. Mines Rept. 2d, pp. i7<;-2:;t>. 1933. Dibblee, T. W., Jr. and Hill, M. L., Rig Pine fault, California (abstract i : Geol. See. America Bull., vol. .",:), p. L369, 1948. Eaton, J. E., Ridge Basin, California: Am. Assoc. Petroleum Geologists Bull., vol. 2::, pp. 517-558, 1939. Fairbanks, II. W.. Report of State Earthquake Investigation Com- mission on the California Earthquake of April is, 1906: Carnegie Inst. Washington, vol. 1, 1908. Fine, S. I'.. Geology of part of the western end of Antelope Valley, California: Unpubl. M, A. thesis, Univ. California, Los Angeles, pp. 1-36, 1947. Goodyear, W. A.. Kern County: California Div. Mines. Rept. 8, pp. 309-324, 1888. Hershey, <>. II.. The Quaternary of southern California: Univ. Cali- fornia Dept. Geol. Sci., Bull., vol. 3. pp. 1-29, 1902. Hershey, <>. II.. Some crystalline rocks of southern California: Am. Geol., vol. 29, pp. 273-290, 1!H>2. Hershey, < '. II., Some Ternary formations of southern California: Am. Geol., vol. 29, pp. :;i!>:;72. 1902, Hinds, X. I-.'. A.. The Jurassic age of the last granitoid intrusives in the Klamath Mountains and Sierra Nevada, California: Amer. Join-. Sci.. 5th Ser., vol. 27. pp. 1^2 1!»2. 1924. Hoots, II. W.. Geologj and oil resources along the southern border of San Joaquin Valley, California: U. S. Geol. Survey Bull. 812, pp. 243 332, 1929. Ilulin. C. D., Geology and ore deposits of the Randsburg quadrangle, California: California Min. Bur. Bull. '.».',, 1 }S pp., V.VITk Jenkins, Olaf P.. Geologic map of California : California Div. Mines, 1938. Johnson, II. R., Water resources of Antelope Valley, California: U. S. Geol. Survey Water-Supply Paper 27s, 99 pp., l'.dl. Knopf, Adolph, A geologic reconnaissance of the [nyo Range and the pastern slope of southern Siena Nevada, California: 1'. S. Geol. Survey Prof, Paper 110, 130 pp., 1910. Loel, Wayne, Geologj of the Ridge Route with road log from Lebec to Cnstaic Junction : Am. Assoc. Petroleum Geologists field Trip Guidebook, Los Angeles, California, pp. 128-132, 1U17. Miller, W. J.. Crystalline rocks of southern California: Geol. Soc. America Bull., vol. 57, pp. 157-542,1946. Noble, I.. P.. The San Andreas rift and some other active faults in i In' desert region of southeastern California : Carnegie Inst. Wash- ington, yearbook i'.". pp. 415-428, 1926. .Nolan, T. I'... The Basin and Range province in Utah, Nevada, and California : U. S. Geol. Survey Prof. Paper 197, pp. 1 11-196, 1943. Pettijohn, I'. J . Sedimentary rocks, Harper and Brothers. New York, 52G pp., Hi !'.». Taliaferro, N. I... Notes on the geologj of Ventura County, Cali- fornia : Am. Assuc. Petroleum Geologists Bull., vol. s, pp. 789 810, 1924, Whitney, J. D., California Geological Survey, vol. 1, pp. 498, 1865. Wiese, J. II.. Geology and mineral resources of the Neenach quail rangle, California: California Div. Mines Bull. 153, pp. 1 53, 1950. Wiese, J. II.. anil Fine, S. P.. Structural features of western Ante lope Valley, California: Am. Assoc. Petroleum Geologists Bull., m,|.:; I. pp. If, 17 1G58, 1950. Wiese, J. II., and Page, L. R., Tin deposits of the Gorman district, Kern County, California: California Div. Mines Kept. 42, pp. 31 52, 1940. Woodford, A. « >. and Harriss, T, F., < leological reconnaissance across Sierra San Pedro Martin, P.aia California: Geol. Soc. America Bull., vol. 4!», pp. 1297-1336, 1938. GEOLOGIC QUADRANGLE MAPS AND REPORTS PUBLISHED BY THE STATE DIVISION OF MINES Scale 1:62500 Geology of the San Renito quadrangle, California, by Ivan F. Wil- son : California Jour. Mines and Geology, April 1943. Map and re- port. Price C>0<\ Geology of the Jamesburg quadrangle, Monterey County, Cali- fornia, by \Y. M. Fiedler: California Jour. Mines and Geology, April 11)44. Map and report. Price (iOc. Geology of the San Juan Rautista quadrangle, California, by J. E. Allen : Rulletin 133. 1940. Geologic and economic maps and report. Price $1.50 (paper-bound), $2.25 (cloth-bound). Geology of the Tesla quadrangle. California, by A. S. Huey : Rulle- tin 140. 104K. Geologic and economic maps and report. Price $1.50 ( paper-bound ) . Geology of the Hollister quadrangle, California, by X. L. Talia- ferro: Rulletin 143. Maps only (geologic and economic). Price 75tf. Geology of the Cppperopolis quadrangle, California, by X. L. Talia- ferro: Bulletin 145. Maps only (geologic and economic). Price ~~,f. Geology of the Lake Elsinore quadrangle, by Rene Engel : Rulletin 14(5. Maps only (geologic and economic). Price 7.">C. Geology of the Quien Sabe quadrangle, California, by C. J. Leith : Rulletin 147. 1949. Geologic and economic maps and report. Price $1.75. Geology of the Rlue Lake quadrangle, California, by G. A. Man- ning and R. A. Ogle: Rulletin 14S. 1050. Geologic and economic maiis, and report. Price $1.50. Geology and mineral deposits of an area north of San Francisco Bay, California (Vacaville, Antioch, Mt. Vaca, Carquinez, Mare Is- land, Sonoma, Santa Rosa, Petaluma, Pt. Reyes quadrangles), by Charles E. Weaver: Rulletin 14!). 1940. Geologic and economic maps and report. Price $4.00. Geology of southwestern Santa Barbara County, California ( Pt. Arguello, Lompoc, Pt. Conception, Los Olivos, Gaviota quadrangles) , by T. W. Dibblee Jr. : Rulletin 150. 1950. Geologic and economic maps and report. Price $5.00. Ceology and mineral resources of the Xeenach quadrangle, Cali- fornia, by John II. Wiese : Rulletin 153. 1950. Geologic and economic maps and report. Price $1.75. Geology of the Cuyamaca Peak quadrangle, San Diego County, California, by 1). L. Everhart : Bulletin 159. 1951. Geologic and eco- nomic maps and report. Price $3.00. Geology of the Saltdale quadrangle, California, by T. W. Dibblee Jr.: Bulletin 160. 1052. Geologic and economic maps and report. Price $2.00. Geology of the Healdsburg quadrangle, California, by W. K. Gealey : Bulletin 101. 1952. Geologic map and report. Price $2.00. Scale: 1:125000 Geology of the Macdoel quadrangle, California, by Howel Wil- liams: Bulletin 151. 1049. Geologic and economic maps and report. Price $1.75. prtnted in California state printing office 60S94 4-52 2M ALPHABETICAL INDEX TO OIL NUMERICAL INDEX TO OIL AND GAS FIELDS AND GAS FIELDS Div. OilSGis Lc designation FIELD Mip" FIELD wit Alton ISA Cat Canyon 10 18 10 Belridge. North Belridge. South Beverly Hills 'I 7 E. Coyote 12 (San Em.diO) Midway i southern portion ol) 54 McKittrick 57 Cymric (portion Of) 55 Temblor 55 McKittrick 43 Cymric 3 North Belridge ISA 2 Csstaie Junction Cat Canyon Chowchilla (gas) VI Antelope Hills McDonald Anticline 14 55 Blackwells Corner 55 Coles Levee. South " 13A Peso Creek Kern Front 39 Coalmga 9A East Coalmga Extension 9 Cymric (portion of) Oel Valle IV 15 Elk Hills 12 29 14 Domingue* |:3Sn.i, 48 East Coyote |j Santa Paula El Segundo Elk Hills 40 Elwood 1 Simi 49 Gill Ranch (gas) Temescal 40 Goleta i abandoned) 53 Greeley 62 Guijarral Hills 1 Newhall-Potrero Oet Valle 30 Oak Canyon Caslaie Junction 31 Inglewood 19 Honor Rancho II 20 Long Beach 13A 13 l 27 28 Huntington Beach Santa Fe Springs Ut.n&te V **" 11 Lodi tgas) Ingievtood 20 LorTg P Beach 34 mVposo* 35 11 Lost Hills IV Round Mountain n McDonald island (gas) Ketlleman North Dome Newport. West North Belridge North Coles Leve Oak Canyon Ojai Placenta Playa del Rey Pleasant Valley Poso Creek 30 Rosecrans 30 35 45 Russell Ranch Salt Lake 47 San Joaquin 15 San Miguelilo 38 Sansinena 27 Santa Fe Springs 51 Santa Maria Valley 17 Santa Paula 1 32 Seal Beach 54 Semitropic (gas) 18 18 Simi 10 55 South Coles Levee 45 South Cuyama 17 30 South Rosecrans Strand Suisun Bay (gas) 7 Sunset (San Emidi 61 61 Tejon Hills Temblor 18 Temescal 55 Ten Section Thornton (gas) 28 Tracy (gas) 58 38 Turnbull Vernalis (gas) 54 West Coyote West Montalvo 60 61 Wheeler Ridge 50 Wilmington 2 Zaca Goleta I abandoned) La Goleta (gas) 41 42 Playa del Rey 43 Capitan 44 Mesa 45 South Cuyama Russel Ranch 46 47 San Ardo 48 Mountain View Ed.son 49 Santa Maria Valley 51 52 El Segundo 53 R?o Bravo Greeley 54 Buttonwtllow (gis) 55 North Coles Levee Ten Section Cantield Ranch Canal 56 Paloma 57 Rio Vista (gas) Cache Slough ((or 1 58 59 60 Newport West Newport 61 Teion Tejon Hills 62 Guijarral Hills 63 Placenta 64 Raisin City San Joaquin FIELDS WITH LETTER DESIGNATIONS i NO DIVISION Oil. M ", I jT I ImH C/flKKUl rziZtl | -" | frmion (re* ~T I Upptr Juriim I I mmc nti-Mtaob j : . | IMdw rd Lfl»n Jibk I I mm* rvtt-w&nesli 1 ft 1 rwli-jjinnJa f-T~ I UrdnW pn-Orltuoa 1 T | UndiRJtd p/t-Frtncuuii 15=]*"* mi>4*M CirtoAnw mm* n*ti'K | (Wi btuN | Q< ] fViihctm nluha [ CV \ FVaten* rhyrtt | Qv> | Platen* bull ■i to. i as^ ^ j P, |fW«fcre, | _ P> f | Ptan* rfrit* | Pv 1 | Piocn* vfcsk | P.' | piecn* buill J p i| j 1M B PVxgJ BfcWH [ »,' | Mten* r^'-y | M.' I M«n» nlnr* | M.» | W«.« teuH j E. | Eece* BluTKt I y, I UrdiwW Totwy | V | Tn-ar, rfyfe | V | T«Mry mkslt | T.> | Twtyry to.ll | T> j Ttfufy mnnno I j rn | Tntary (-«t < redi g[ [TT] UMti p«* r«ta 8[[T]^-..— g, I ) rvt.Kfcjfta 1 OM-.-W PJmkk mtu- r£] GEOLOGIC BOUNDARIES 1 I i L , ■ *■' uHCtm. DIVISION OF MINES OLAF P, JENKINS, CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES EXPLANATION SEDIMENTARY ROCKS Peace Volley beds (brown stltstone with buff sandstone; some onglomerote and sedimentary breccia) UNCONFORMITY >.! VM Lebec quartz monzonite (gray hornblende biotite quartz monzonite) Diorite (coarse gray bio tile hornblende diori te, gneissose, with minor quarlz) Crushed gronodiorile (brown sheared gronodiorite, diorite and other granite rocks, with limestone inclusions) Liebre quorlz monzonite (fractured gray hornblende biolile quartz monzonite with dark inclusions and pegmatites) (chiefly blue-gray limestone, recrystallized) liMMJIjii] (chiefly brown hornfels and schist) {Known position Approximate position Alluvium and terrace boundaries Mappoble beds {Known position Approximate position Concealed Thrust, H on upper plate GEOLOGIC MAP OF THE LEBEC QU ADR ANGLE , CALIFORNIA By John C. Crowell Anticline shov ing plu fige Anticline, ove rtur ned Syncline Normal Overturned Vertical Fossils Prospects Geologic mopping 1947-50 Peace Volley San Andreos fault zone Section along line A- A 4000- 300u- Hunqry Volley Fre Q ui 2000 ■ TM - 1000- •."'""'■"•I „ Section along line B- B' Tehachapi Mountains Liebre Mountain Section along line C-C Son Andreas (null .on. Antelope Valley Section along line D-D SEO LEVE Section along line E-E EXPLANATION Chiefly sandstone School Conyon gr< Hungry Volley formation Chiefly conglomerate Terrooe deposits Peace Valley beds Sonta Morganta fo rmation Oiorite Crushe :, : , r/ j Liebre aaor.i m 's Limestone ho Tejon Lookout gron.te rnlels and schis GEOLOGIC SECTIONS OF THE LEBEC QUADRANGLE, CALIFORNIA By John C. Crowell, 1947-50