preliminary geologic map of the grapevine 7.5' …€¦ · 136.4 ma 105 ma 105.2 ma 121.3 ma...
TRANSCRIPT
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105 Ma
105.2 Ma
121.3 Ma
135.6 Ma
101 Ma
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119°0'0''35°0'0"
34°52’30”119°0'0''
34°52’30”118°52’30”
118°52’30”35°0'0"
STATE OF CALIFORNIA – EDMUND G. BROWN JR., GOVERNORTHE NATURAL RESOURCES AGENCY – JOHN LAIRD, SECRETARY FOR NATURAL RESOURCES
DEPARTMENT OF CONSERVATION – MARK NECHODOM, CONSERVATION DIRECTOR CALIFORNIA GEOLOGICAL SURVEYJOHN G. PARRISH, Ph.D., STATE GEOLOGIST
This geologic map was funded in part by the USGS National Cooperative Geologic MappingProgram, Statemap Award no. G13AC00163
PRELIMINARY GEOLOGIC MAP OF THE GRAPEVINE 7.5' QUADRANGLE,KERN COUNTY, CALIFORNIA: A DIGITAL DATABASE
VERSION 1.0By
Brian P.E. Olson
Digital Preparation by
Brian P.E. Olson and Carlos I. Gutierrez
2014
PRELIMINARY GEOLOGIC MAP OF THE GRAPEVINE 7.5’ QUADRANGLE, CALIFORNIA
Copyright © 2014 by the California Department of ConservationCalifornia Geological Survey. All rights reserved. No part ofthis publication may be reproduced without written consent of theCalifornia Geological Survey.
"The Department of Conservation makes no warranties as to thesuitability of this product for any given purpose."
Projection: Universal Transverse Mercator, Zone 11N, North American Datum 1927.
Topographic base from U.S. Geological SurveyGrapevine 7.5-minute Quadrangle, 1991; Photorevised 1974. Shaded relief image derived from USGS 1/3 arc-second National Elevation Dataset (NED).
Professional Licenses and Certifications: B.P.E. Olson - PG No. 7923, CEG No. 2429
65
25
35
MAP SYMBOLS
27?
27?
? Contact between map units - Solid where accurately located; short dash where inferred; long dash where approximately located; dotted where concealed; queried where identity or existence is uncertain
Fault - Solid where accurately located; long dash where approximately located; short dash where inferred; dotted where concealed; queried where identity or existence is uncertain. Arrow and number indicate direction and angle of dip of fault plane
Thrust Fault - Barbs on upper plate; solid where accurately located; short dash where inferred; dotted where concealed; queried where identity or existence is uncertain. Arrow and number indicate direction and angle of dip of fault plane
Syncline - Solid where accurately located
Overturned syncline - Solid where accurately located
Anticline - Solid where accurately located; long dash where approximately located; dotted where concealed
Overturned anticline - Long dash where approximately located; dotted where concealed
Antiform - Solid where accurately located
Bentonite bed
Strike and dip of sedimentary beds. Number indicates dip angle in degrees:
Inclined bedding
Vertical bedding
Overturned bedding
Strike and dip of igneous foliation. Number indicates dip angle in degrees:
Inclined foliation
Vertical foliation
Strike and dip of inclined metamorphic foliation. Number indicates dip angle in degrees
Strike and dip of inclined joints. Number indicates dip angle in degrees.
Sample locality showing radiometric age date; may be shown with leader line
25
25
136.4 Ma
SELECTED REFERENCESChapman, A.D., 2012, Late Cretaceous gravitational collapse of the southern Sierra Nevada batholith and adjacent areas above underplated schists, southern California:
Ph.D. dissertation, California Institute of Technology, map scale 1:24,000.
Chapman, A.D., Kidder, S., Saleeby, J.B., and Ducea, M.N., 2010, Role of extrusion of the Rand and Sierra de Salinas schists in Late Cretaceous extension and rotation of the southern Sierra Nevada and vicinity: Tectonics, v.29, no.5.
Chapman, A.D., Luffi, P.I., Saleeby, J.B., and Petersen, S., 2011, Metamorphic evolution, partial melting and rapid exhumation above an ancient flat slab: insights from the San Emigdio Schist, southern California: Journal of Metamorphic Geology, v.29, no.6, p.601–626.
Chapman, A.D. and Saleeby,J.B., 2012, Geologic map of the San Emigdio Mountains, southern California: Geological Society of America, Map and Chart m 101, map scale 1:40,000.
Chapman, A.D., Saleeby, J.B., and Eiler, J., 2013, Slab flattening trigger for isotopic disturbance and magmatic flare-up in the southernmost Sierra Nevada batholith, California: Geology, v.41, no.9, p.1007-1010.
Cole, R.B., and Decelles, P.G., 1991, Subaerial to submarine transitions in early Miocene pyroclastic flow deposits, southern San Joaquin basin, California: Geological Society of America Bulletin, v.103, no.2, p.221–235.
Critelli, S., and Nilsen, T.H., 2000, Provenance and stratigraphy of the Eocene Tejon Formation, Western Tehachapi Mountains, San Emigdio Mountains, and Southern San Joaquin Basin, California: Sedimentary Geology, 136(1), p.7-27.
Dibblee, T.W., Jr., 1973a, Geologic maps of the Santiago Creek, Eagle Rest Peak, Pleito Hills, Grapevine, and Pastoria Creek quadrangles, Kern County, California: U.S. Geological Survey Open File Report 73–57, map scale 1:24,000.
______, 1973b, Stratigraphy of the Southern Coast Ranges near the San Andreas Fault from Cholame to Maricopa, California: U.S. Geological Survey Professional Paper 764.
Dibblee, T.W., Jr. and Minch, J.A. (ed.), 2005, Geologic map of the Grapevine/south 1/2 of Mettler quadrangles, Kern County, California: Dibblee Geological Foundation, Dibblee Foundation Map DF-174, map scale 1:24,000.
Grove, M., Jacobson, C.E., Barth, A.P., and Vucic, A., 2003, Temporal and spatial trends of Late Cretaceous-early Tertiary underplating of Pelona and related schist beneath southern California and southwestern Arizona: Tectonic Evolution of Northwestern Mexico and the Southwestern USA: Geological Society of America, Special Paper 374, p.381-406.
Hall, N.T., 1984, Late Quaternary history of the eastern Pleito thrust fault, northern Transverse Ranges, California: Stanford, California, Stanford University, unpublished Ph.D. dissertation, 89 p., 16 pls., scale 1:6,000.
Hoots, H.W., 1930, Geology and oil resources along the southern border of San Joaquin Valley, California, in Contributions to economic geology: U.S. Geological Survey Bulletin 812-D, p. 243-338, scale 1:62,500.
Jacobson, C.E., Grove, M., Pedrick, J.N., Barth, A.P., Marsaglia, K.M., Gehrels, G.E., and Nourse, J.A., 2011, Late Cretaceous–early Cenozoic tectonic evolution of the southern California margin inferred from provenance of trench and forearc sediments: Geological Society of America Bulletin, v.123, nos.3-4, p.485-506.
Keller, E.A., Zepeda, R.L., Rockwell, T.K., Ku, T.L., and Dinklage, W.S., 1998, Active tectonics at Wheeler Ridge, southern San Joaquin Valley, California: Geological Society of America Bulletin, v.110, no.3, p.298–310.
Keller, E.A., Seaver, D.B., Laduzinsky, D.L., Johnson, D.L., and Ku, T.L., 2000, Tectonic geomorphology of active folding over buried reverse faults: San Emigdio Mountain front, southern San Joaquin Valley, California: Geological Society of America Bulletin, v.112, no.1, p.86–97.
Lagoe, M.B., 1987, Cenozoic stratigraphic framework for the San Emigdio Mountains, California, in Davis, T.L. and Namson, J.S., Editors, Structural Evolution of the Western Transverse Ranges: Society of Economic Paleontologists and Mineralogists, Book 48A, p. 85–98.
Lancaster, J.T., Hernandez, J.L., Haydon, W.D., Dawson, T.E., and Hayhurst, C.A., 2012, Geologic Map of Quaternary Surficial Deposits, Lancaster 30’ X 60’ Quadrangle: California Geological Survey Special Report 217, Plate 22.
Nilsen, T.H., 1987, Stratigraphy and Sedimentology of the Eocene Tejon Formation, Western Tehachapi and San Emigdio Mountains, California: U.S. Geological Survey Professional Paper 1268, map scale 1:62,500.
Nilsen, T.H., Dibblee, T.W., and Addicott, W.O., 1973, Lower and Middle Tertiary stratigraphic units of the San Emigdio and western Tehachapi Mountains, California: U.S. Geological Survey Bulletin 1372–H, p.H1–H23.
Pickett, D.A., and Saleeby, J.B., 1993, Thermobarometric constraints on the depth of the exposure and conditions of plutonism and metamorphism at deep levels of the Sierra Nevada batholith, Tehachapi Mountains, California: Journal of Geophysical Research, v. 98, p. 609–629.
Plescia, J.B., Calderone, G.J., and Snee, L.W., 1994, Paleomagnetic analysis of Miocene basalt flows in the Tehachapi Mountains, California: US Geological Survey Bulletin 2100.
Ross, D.C., 1989, The metamorphic and plutonic rocks of the southernmost Sierra Nevada, California, and their tectonic framework: USGS Professional Paper1381, map scale 1:125,000.
Saleeby, J., Farley, K.A., Kistler, R.W., and Fleck, 2007, Thermal evolution and exhumation of deep-level batholithic exposures, southernmost Sierra Nevada, California, in Cloos, M., Carlson, W.D., Gilbert, M.C., Liou, J.G., and Sorensen, S.S., eds., Convergent Margin Terranes and Associated Regions: A Tribute to W.G. Ernst: Geological Society of America Special Paper 419, p. 39–66
Smith, T.C., 1984, Wheeler Ridge and Pleito fault systems, southwestern Kern County, California: California Division of Mines and Geology, Fault Evaluation Report FER-150 (unpublished), scale 1:24,000.
Streckeisen, A.L., 1973, Plutonic rocks – Classification and nomenclature recommended by the IUGS Subcommission on Systematics of Igneous Rocks: Geotimes, v. 18, p. 26–30.
______, 1976, To each plutonic rock a proper name: Earth Science Reviews, v. 12, p. 1–33.
Tedford, R.H., 1961, Fossil mammals from the Tecuya Formation, Kern County, California: Society of Economic Paleontologists and Mineralogists, Society of Exploration Geophysicists, American Association of Petroleum Geologists, and San Joaquin Geological Society, Spring Field Trip Guidebook, p. 40-41.
Turner, D.L., 1970, Potassium-argon dating of Pacific Coast Miocene foraminiferal stages: Geological Society of America, Special Paper 124, p.91-129.
Williams, L.A., 1982, Lithology of the Monterey Formation (Miocene) in the San Joaquin Valley of California, in Williams, L.A. and Graham, S.A., Editors, Monterey Formation and Associated Coarse Clastic Rocks, Central San Joaquin Basin, California: Society of Economic Paleontologists and Mineralogists, Pacific Section, Volume and Guidebook, p.17-35.
AIR PHOTOS/Digital Imagery
U.S. Department of Agriculture, 1952, Aerial photographs, Flight ABL-21K, frames 14-20, 53-54, 173-177, 193-195, 212-214, black and white, dated 11/18 and 11/25/1952, approximate scale 1:24,000.
U.S. Department of Agriculture, Farm Service Agency–Aerial Photography Field Office, National Agriculture Imagery Program (NAIP), 2012, 1–meter resolution. http://datagateway.nrcs.usda.gov/
U.S. Geological Survey, 1994, Digital Orthophoto Quarter Quadrangle Photos, dated 05/29 and 6/5/1994, Grapevine Quadrangle. (DOQQ and information concerning them can be obtained at http://earthexplorer.usgs.gov/).
_____, 2002, Digital Orthophoto Quarter Quadrangle Photos, dated 06/11/2002, Grapevine Quadrangle. (DOQQ and information concerning them can be obtained at http://earthexplorer.usgs.gov/).
_____, 2008, High Resolution Orthoimagery (HRO), Grapevine Quadrangle, dated 04/29/2008, 1–meter resolution, http://datagateway.nrcs.usda.gov/
_____, 2010, High Resolution Orthoimagery (HRO), Grapevine Quadrangle, dated 04/07/2010, 1–meter resolution, http://datagateway.nrcs.usda.gov/
U.S. Geological Survey, EROS Data Center, 1999, National Elevation Dataset, 1/3 arc second resolution, http://ned.usgs.gov/
APPROXIMATE MEANDECLINATION, 2014
0
0
0
1
1
1.5
.5 2
2
2Thousand Feet
Kilometers
Miles
Scale 1:24,000
Contour Interval 40 feetNational Geodetic Vertical Datum of 1929
5
COTTONWOODCR
SANTA CLARA R
99
Bouquet ResElderberry
Forebay
Castaic Lake
R o s a m o n d L a k e Buckhorn
Lake
Piru Lake
Santa Clara River
Pyramid Lake
Little Rock Wash
Fillmore
Gorman
LakeHughes
Lebec
LeonaValley
Littlerock
Mojave
Piru
QuartzHill
Rosamond
Saugus
Valencia
Acton
Agua DulceCastaic
48
166
58
126
14
138
118°0'0"W118°30'0"W119°0'0"W
35°0
'0"N
34°3
0'0"
N
Mapping completed under STATEMAP
FY 2009-10FY 2009-10
FY 2008-09
PREVIOUS YEARS
CURRENT YEAR
FY 2010-11
FY 2010-11 FY 2010-11
FY 2011-12
FY 2011-12
FY 2012-13
Kilometers
Miles
5
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(T(T(T(TT(T(Tehehehehehehhacacacacacachahahahahahapipipipipipi))))))(T(T(T(T(T( ehehehehe acacaca hahahahaaapipipipipipi)))))
(T(T(T(T(T(Tehehehehehehacaacacachahahaaapipipipipipipi)))))))l
- Adjacent 30’ X 60’ quadrangles
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GRAPEVINE
FRAZIER
MOUNTAIN
ALAMO
MOUNTAIN
DEVILS
HEART
PEAK
PASTORIA
CREEK
LEBEC
BLACK
MOUNTAIN
COBBLESTONE
MOUNTAIN
WINTERS
RIDGE
LA LI
EBRE
RANCH
LIEBRE
MOUNTAIN
WHITAKER
PEAK
LIEBRE
TWINS
NEENACH
SCHOOL
BURNT
PEAK
WARM
SPRINGS
MOUNTAIN
TYLERHORSE
CANYON
FAIR
MONT
BUTTE
LAKE
HUGHES
GREEN
VALLEY
WILLOW
SPRINGS
LITTLE
BUTTES
DEL
SUR
SLEEPY
VALLEY
SOLEDAD
MOUNTAIN
ROSAMOND
LANCASTER
WEST
RITTER
RIDGE
BISSELL
ROSAMOND
LAKE
LANCASTER
EAST
PALMDALE
FY 2013-14
QuartzSyenite
QuartzMonzonite
QuartzMonzodiorite
Syenite Monzonite Monzodiorite
Granite
Alka
li-feld
spar
Gra
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Tonalite
Diorite
Syen
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Granodioriteno
Mnargoz
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Quartz
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CORRELATION OF MAP UNITS
QU
ATER
NAR
Y
Pliocene
Holocene
Pleistocene
Miocene
TER
TIAR
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Oligocene
CEN
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ICM
ESO
ZOIC
PALE
OZO
IC
CR
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EOU
SJU
RAS
SIC
Eocene
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Pastoria Plate TSE San Emigdio Schist WSEMC
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SURFICIAL UNITS
Artificial fill and disturbed areas (historic, Holocene) – Consists of man-made deposits of earth-fill soils derived from local sources. Mapped specifically along the California Aqueduct structure, debris catchment basins, and includes fill soils along freeway/road alignments.
Wash deposits (late Holocene) – Unconsolidated sand and gravel deposited in recently active stream channels. Deposits are generally derived from local bedrock, or reworked from other local Quaternary sources. Subject to localized reworking and new sediment deposition during storm events.
Modern alluvial fan deposits (late Holocene) – Unconsolidated to weakly consolidated, poorly sorted, gravel, sand, and silt deposits forming active, essentially undissected, alluvial fans. Includes small to large cones at the mouths of stream canyons and broad aprons of coarse debris adjacent to mountain fronts. Gravel clasts are typically unweathered with little to no oxidation. Unit includes local mudflow deposits consisting of massive sandy silty cobble to boulder gravel. (Units Q6 through Q8 of Hall, 1984).
Modern alluvium (Holocene) – Unconsolidated to weakly consolidated, mostly undissected, fluvial gravel, sand and silt. Loose, yellowish-gray sand, silt, and pebble to cobble gravel. Consists predominately of moderately sorted coarse-grained to very coarse-grained arkosic sand.
Ponded alluvium (Holocene) – Unconsolidated to weakly consolidated sand, silt, and clay deposits in closed depressions.
Younger alluvial deposits (middle Holocene to Late Pleistocene) – Unconsolidated thin- to thick-bedded gravel. Deposited in point bar and overbank settings associated with active stream channels.
Landslide deposits (Holocene to Late Pleistocene) – Unconsolidated to moderately well-consolidated jumbled rock debris consisting of surficial failures resulting from soil and rock creep, debris flows, and large-scale rotational rock slides. Recognizable by topographic expression or chaotic internal structure.
Younger alluvial fan deposits (middle Holocene to Late Pleistocene) – Unconsolidated to weakly consolidated, pale brown to dark yellowish brown, silty and coarse to very coarse arkosic sand with pebbles and cobbles, moderately to well-stratified. Gravels are typically clast-supported, oxidized, and primarily from granitic sources, with many sub–rounded friable mafic schist clasts. Silt layers exposed in vertical stream bank cuts show weak prismatic structure. Unit is exposed as slightly dissected, elevated broad alluvial fans and canyon fill along the northern flank of the San Emigdio Mountains. Along the Plieto Fault these deposits are slightly deformed and partially dissected (Units Q4 and Q5 of Hall, 1984).
Older fan deposits (Late to Middle Pleistocene) – Slightly to moderately consolidated, poorly sorted, silty pebbly sand to coarse gravel and boulder fan deposit. Unit is poorly to moderately stratified with a moderately developed Bt horizon up to 0.5m thick (Unit Q3 of Hall, 1984).
Very old fan deposits (Early Pleistocene) –Moderately to well-consolidated, poorly sorted, coarse gravel and boulder fan deposit, highly elevated and dissected.
TERTIARY SEDIMENTARY AND VOLCANIC UNITS
Tulare Formation (Pleistocene to Late Pliocene) – Loosely consolidated light gray boulder conglomerate, conglomeratic sandstone, sandstone, and claystone, non-marine. Conglomerate clasts composed of siliceous (Monterey) shale, sandstone, and basement rocks in gray sandy to clayey matrix, clasts are angular to subangular.
Monterey Formation (Middle to Early Miocene)Gould shale member – White to grayish brown siliceous and semi-siliceous biogenic shale and porcelanite, marine, thin bedded,
platy to fissile, abundant soft-sediment deformational folding, weathers cream to buff, includes thin dolomite layers. Abundant foraminifera indicating Late Saucesian to Relizian age (Dibblee, 1973a; Nilsen et al., 1973).
Clay shale member – Gray clay shale and siltstone, marine, bedded.
Bena Conglomerate (Middle to Early Miocene) – Gray to brown sandy polymictic cobble conglomerate with minor sandstone interbeds, non-marine, massive to crudely bedded, clast-supported, composed of poorly sorted cobbles with some boulders in a weakly consolidated arkosic sand matrix. Interfingers to the west with the Monterey Formation. Deposited with angular unconformity on the Tecuya Formation east of Tecuya Canyon.
Temblor Formation (Early Miocene)Siltstone member – Pale yellow, light gray, light brown siltstone and fine-grained sandstone, marine, massive to locally bedded.
Sandstone member – Gray, light yellow, and yellowish brown fine- to coarse-grained and conglomeratic sandstone, marine, micaceous, locally silty, bedded, locally contains brown spherical boulder-sized concretions.
Tecuya Formation (Early Miocene to late Oligocene)Sandstone and conglomerate member (Early Miocene) – Pale yellow, light yellowish brown, and gray medium- to coarse-grained
and conglomeratic sandstone and sandy pebble to cobble conglomerate, nonmarine, massive to thick-bedded, cemented. Conglomeratic sandstones and conglomerates contain distinctive black subrounded to rounded fine-grained mafic clasts. Local basal boulder conglomerate, clasts up to 3 meters in diameter. Overall, this unit is lithologically similar to the granitic conglomerate member (map symbol: Ttg) but with a higher proportion of sandstone to conglomerate.
Airfall tuff (Early Miocene?) – Hornblende-rich airfall tuff, well-indurated. Unit only occurs on ridgeline between Colorful and Tecuya Canyons, near the Grapevine Thrust Fault, where it appears to be in contact with both Jurassic gabbro (map symbol: Jg) and the lower members of the Tejon Formation (map symbols: Ttju and Ttjl). The nature of these contacts is not readily observable in the field and therefore, the unit is tentatively included with the other volcanic units in the map area, following Chapman (2012).
Basalt flows (Early Miocene) – Black to dark reddish brown aphanitic and locally scoriaceous basalt with basalt breccias/conglomerate, subaerial, local silica-filled amygdules. Outcrops locally exhibit sub-parallel sheet jointing. Interfingers to the west with the sandstone member of the Temblor Formation (map symbol: Tts). In thin section the basalt exhibits pilotaxitic to trachytic texture (Cole and DeCelles, 1991). Breccia and conglomerate facies are poorly-sorted, inversely-graded, matrix-supported, and contain angular to subrounded boulder-sized clasts of thinly bedded aphanitic basalt. K/Ar date of 24.6 ± 2.9 Ma (Turner, 1970).
Dacite tuff and tuff breccia (Early Miocene) – Light gray thin to medium-bedded tuff and gray, pink, and red dacitic tuff breccias, subaerial. Lower portion is 4 to 12 meters of thin-bedded tuff containing fragments of zoned and twinned plagioclase, quartz, biotite, hornblende, porphyritic dacite, and pumice in a vitric groundmass (Cole and DeCelles, 1991). Tuff facies also contains very thin pumice-rich beds. Upper part of unit consists of poorly-sorted, matrix-supported dacite tuff breccia, 1 to 15 meters thick, massive with local inverse grading, porphyritic dacite boulders (up to 4 meters in diameter) are common, locally welded with flattened and deformed pumice fragments. Basal contact is conformable with nonmarine conglomerate member (Ttg). K/Ar dates range from 21.5 ± 0.6 to 21.9 ± 0.7 Ma (Turner, 1970).
Granitic conglomerate member (Early Miocene to late Oligocene) – Interbedded red, green, gray, and brown mudstone, siltstone, sandstone, and pebble to boulder conglomerate, nonmarine, occasional channel scour and fill structures. Conglomerate is primarily composed of granitic and metamorphic clasts, including metavolcanic and quartzite clasts, in a coarse sandy matrix. Occasional interbeds of fossiliferous marine siltstone. Mammalian fossils recovered between Tecuya Creek and Salt Creek are assigned to the early part of the Arikareean Land Mammal Age (Tedford, 1961).
Granitic breccia member (late Oligocene) – Greenish gray boulder cobble conglomerate with minor very coarse-grained to pebbly sandstone, nonmarine. Only found along western edge of map area, discontinuous.
TERTIARY SEDIMENTARY AND VOLCANIC UNITS (continued)
San Emigdio Formation (late(?) to middle Eocene) – Thinly laminated siltstone and silty shale with fine-grained sandstone, marine/lagoonal deposits. Unit is exposed discontinuously throughout the map area and is not formally recognized east of Grapevine Creek. Locally contains molluscan megafossils and foraminifera, as well as carbonaceous and coal-bearing strata. Mapped as the Reed Canyon Siltstone Member of the Tejon Formation by Nilsen (1987) and Dibblee (1973a).
Tejon Formation (middle to early Eocene)Metralla Sandstone Member (middle Eocene) – Silty and fine- to medium-grained sandstone with occasional siltstone interbeds
and minor conglomerate, marine, poorly cemented. Number and thickness of siltstone beds and total unit thickness increase from east to west. Sandstone is typically highly bioturbated, exhibits large-scale cross-stratification, current ripple marks, and contains distinctive spherical calcareous concretions. Typical conglomerate clasts include quartzite, porphyritic volcanic, gneiss, and quartz diorite-granodiorite up to one inch in diameter. Sandstone and conglomerate beds contain locally abundant molluscan megafossils and siltstone beds commonly possess abundant foraminifera.
Live Oak Shale Member (middle to early Eocene) – Laminated to massive shale and mudstone with interlaminated siltstone and minor sandstone interbeds, marine, poorly cemented. Extensively bioturbated by various irregular burrows and borings. Predominately fine to medium sandstone near the upper and lower contacts. Sandstone is commonly graded and exhibits cross-stratification and sole marks suggestive of turbidity flow deposits. Upper and lower contacts are both gradationally conformable. Shale contains abundant foraminifera and occasional invertebrate megafossils.
Uvas Member (middle to early Eocene) – Buff-weathering conglomeratic medium- to coarse-grained arkosic sandstone and cobble conglomerate, marine. Sandstones are typically quartz-rich, well-sorted with medium to large-scale cross-bedding, current ripple marks, and massive bedding. The conglomerate beds contain well-rounded clasts of quartzite and porphyritic volcanic rock, as well as locally derived gneissic, granodioritic, and gabbroic clasts. Locally abundant invertebrate megafossils and foraminifera.
INTRUSIVE AND METAMORPHIC ROCKS – MESOZOIC AND/OR OLDER
Pastoria Upper PlateLebec Granodiorite (Late Cretaceous) – Light gray medium- to coarse-grained biotite granodiorite, locally potassium feldspar
porphyritic, some secondary chlorite and muscovite. Weighted mean U/Pb zircon ages range from 88 to 92 Ma (Chapman, 2012).
Granite of Brush Mountain (Early Cretaceous) – Light colored coarse-grained granite, highly altered, liesegang banding common, forms yellow to orange craggy exposures. Occurs as the uppermost plate of the Pastoria fault system forming extremely altered klippen. U/Pb zircon age of 104.7 ± 0.9 Ma (Chapman, 2012).
Marble (Mesozoic to Paleozoic?) – White to gray medium grained mylonitic to cataclastic marble.
Techachapi-San Emgdio Complex (TSE)Garnet–Biotite Tonalite of Grapevine (Late Cretaceous) – Light-colored fine- to medium-grained, garnet biotite tonalite, foliated.
Garnets range from 3 to 5 mm in diameter. Intrudes Grapevine Canyon paragneiss (Pzg). Correlative to the "garnet tonalite" of the Intrusive suite of Bear Valley in the Tehachapi Mountains and southern Sierra Nevda to the northeast (Saleeby et al., 2007). In thin section, samples have abundant plagioclase, biotite, hornblende, and disseminated small garnets. U/Pb zircon age of 101 ± 1 Ma (Saleeby et al., 2007).
San Emigdio Quartz Diorite Orthogneiss (Early Cretaceous) – Dark colored, medium-grained, hornblende quartz diorite orthogneiss, foliated, locally contains coarse red almandine-rich garnet porphyroblasts up to 3 cm. Unit is located structurally above the Rand Fault and exhibits a strongly attenuated structural fabric characterized by anastomosing ductile to brittle shear zones. Correlative with the "hornblende gabbroids" of the Bear Valley intrusive suite of Saleeby et al. (2007) in the Tehachapi Mountains and southern Sierra Nevada to the northeast. In thin section, samples show biotite-rich shear bands and quartz grains with undulatory extinction. U/Pb zircon age of 105.8 ± 0.6 Ma (Chapman, 2012).
Quartzofeldspathic Gneiss of Pastoria Creek (Early Cretaceous) – Heterogeneous mixture of tonalite, mafic rock, and granodiorite, moderately to strongly layered. Part of the "gneiss complex of the Tehachapi Mountains" described by Saleeby et al. (2007) with a U/Pb zircon age of 112 ± 2 Ma.
Digier Canyon Quartz Diorite Orthogneiss (Early Cretaceous) – Brownish green to black medium-grained hornblende quartz diorite to gabbro orthogneiss, weakly to moderately developed foliation. Similar to Kseg but garnet porphyroblasts are rare. Western continuation of the White Oak diorite gneiss, which is a tectonic mixture of amphibolite to locally greenschist (retrograde) facies dioritic, gabbroic, and mylonitic gneisses representing the lower portion of the "gneiss complex of the Tehachapi Range" described by Saleeby et al. (2007). In thin section, samples have abundant hornblende, subhedral zircons, and weakly-developed polycrystalline quartz ribbons. U/Pb zircon ages range from 105.2 ± 4.2 to 121.3 ± 1.4 Ma (Chapman, 2012).
San Emigdio Tonalite (Early Cretaceous) – Light colored garnet biotite tonalite and trondhjemite, massive to moderately foliated, composed predominantly of plagioclase, quartz, biotite, and reddish pink garnet. Metamorphosed to upper amphibolite facies. In thin section, samples show euhedral epidote phenocrysts embayed in biotite. U/Pb zircon age of 136 ± 2 Ma (Chapman, 2012).
Grapevine Canyon Paragneiss and Grapevine Peak migmatite (Mesozoic to Paleozoic?) – Light to dark brown metasandstone and metapelite, strongly foliated and isoclinally folded, variably migmatized. Occurs as pendants within TSE complex. Contains mainly plagioclase, quartz, potassium feldspar, biotite, red garnet, and graphite, with large (1-3 cm) tabular muscovite pseudomorphs after kyanite (Pickett and Saleeby, 1993). Correlative with the "migmatitic paragneiss" at the structural base of the "gneiss complex of the Tehachapi Mountains" (Saleeby et al., 2007).
San Emigdio SchistMetasandstone (Late Cretaceous) – Light blue to dark gray coarse-grained metapsammite, quartzite, and quartzofeldspathic schist,
massive to well-foliated, highly sheared. Metasandstone member characterized by the peak mineral paragenesis of garnet + plagioclase + biotite + quartz ± muscovite ± kyanite (Chapman, 2012). Garnets typically occur as idoiblastic grains ranging from 1 to 5 mm. Grades from upper amphibolite to epidote-amphibolite facies. Occasional deformed quartzofeldspathic veins are visible in outcrops. The San Emigdio Schist represents forearc trench sediments deposited between 98 and 102 Ma, subducted to a depth of 30 to 35 km, and exhumed to upper crustal levels between 89 and 93 Ma (Grove et al., 2003; Jacobson et al., 2011, Chapman et al., 2013). In thin section, metasandstone samples have elongate quartz grains with undulatory extinction and subhedral garnet porhyroblasts with blebby quartz inclusions. Primary micas show uniform orientation.
Metabasalt (Late Cretaceous) – Dark brown to greenish black metabasalt, commonly black and white polka-dotted to striped texture, commonly bimineralic with amphibole and plagioclase. Plagioclase porphyroblast composition typically ranges from An17 to An35 (Chapman, 2012). Diopsidic and augitic clinopyroxenes occur proximal to the Rand Fault. Appears as small, irregular bodies within map unit Ks.
Ultramafic (Late Cretaceous) – Light to dark green talc and actinolite schist bodies, massive, waxy, associated with map unit Ksm.
Western San Emigdio Mafic Complex (WSEMC)Gabbro (Jurassic) – Light purple to green fine- to medium-grained gabbro, olivine gabbro, and hornblende gabbro, massive to
strongly foliated. Locally pervasive alteration of pyroxene to amphibole (Chapman, 2012).
DESCRIPTION OF MAP UNITS
af
Qw
Qa
Qya
Qyf
Qf
Qpa
Qls
Qof
Qvof
QTt
Tmg
Tmc
Tbc
Tt
Tts
Ttva
Ttc
Ttvb
Ttvd
Ttg
Ttgb
Tse
Ttjm
Ttjl
Ttju
Kle
Ksu
Ksm
Ks
Kg
Kbm
Kdc
Kseg
Kpc
Kset
}|m
Jg
|g
Preliminary Geologic Map available from:http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm