70 72

24

30

62

77

35

5540

6038

30

QofQa}pos

QofQa

Qyf

Qof

Kgr

af

QofKgr

Qof

Qyf

Qa

QofQyf

Qa

Qyf

af

}db

af

QyfsQa

}pos}db

}pos

}pos

Qc

Qyfs Qf

Qa

Qa

Qe

Qa

Qe

af

Qf

Qe

Qw

af

af

Qya

Qyf

af

af

Qf

Qyfc

Qyp

Qf

af

af

af

Qf

af

af

Qa

Qf

Qf

Qyfc

Qf

Qa

Qf

af

Qyfc

Qyp

Qyp

Qyfc

}pos

}db

Qyf

Qyf

Qf

Qyfc

Qyfc

Qf

QypQyp

Qyp

Qya

118°15'34°45'00"

34°37'30"118°15'

34°37'30"118°07'30"

118°07'30"34°45'00"

STATE OF CALIFORNIA - ARNOLD SCHWARZENEGGER, GOVERNORTHE NATURAL RESOURCES AGENCY - LESTER A. SNOW, SECRETARY FOR NATURAL RESOURCES

DEPARTMENT OF CONSERVATION - DEREK CHERNOW, ACTING DIRECTOR CALIFORNIA GEOLOGICAL SURVEYJOHN G. PARRISH, Ph.D., STATE GEOLOGIST

Topographic base from U.S. Geological Survey Lancaster West 7.5-minute Quadrangle, 1958, Photorevised 1974UTM projection, Zone 11, North American Datum 1927

This geologic map was funded in part by the USGS National Cooperative Geologic MappingProgram, Statemap Award no. G09AC00193

GEOLOGIC MAP OF THELANCASTER WEST 7.5' QUADRANGLE

LOS ANGELES COUNTY, CALIFORNIA: A DIGITAL DATABASEVERSION 1.0

ByJanis L. Hernandez

Digital Database by

Janis L. Hernandez, Carlos I. Gutierrez and George J. Saucedo

2010

Copyright © 2010 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."

65 Strike and dip of metamorphic foliation.

35 Strike and dip of igneous joint.

Vertical igneous joint.

Vertical igneous foliation

MAP SYMBOLS

27

Fault - Solid where accurately located, dashed where where approximately located; short dash where inferred; dotted where concealed, queried where uncertain. Arrow and number indicate direction and angle of dip of fault plane.

Contact between map units - Solid where accurately located; long dash where approximately located; short dash where inferred; dotted where concealed, queried where uncertain.

?

?

SELECTED REFERENCESBarrows, A.G., Kahle, J.E., and Beeby, D.J., 1985, Earthquake hazards and tectonic history of the San Andreas Fault Zone, Los Angeles County, California: California Division of Mines and Geology Open-File Report 85-10LA, 236 p., 21 plates, scale 1:12,000.

Dibblee, T.W., Jr., 1960, Geologic map of the Lancaster quadrangle, Los Angeles County, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-76, scale 1:62,500.

______, 1967, Areal geology of the western Mojave Desert, California: U.S. Geological Survey Professional Paper 522, 153 p., scale 1:125,000.

Evans, J.G., 1966, Structural Analysis and movements of the San Andreas Fault Zone near Palmdale, southern California, Ph.D. thesis, University of California, Los Angeles, scale 1:12,000.

Evans, J.G., 1978, Postcrystalline Deformation of the Pelona Schist bordering Leona Valley, southern California: U.S. Geological Survey Professional Paper 1039, 17 p., scale 1:10,000.

Hoirup, D.F., and Hernandez, J.L., 2004, Earthquake-Induced landslide zones of required investigation in the Lancaster West 7.5-minute quadrangle, Los Angeles County, California: California Geological Survey Seismic Hazard Zone Report 95, Section 2, pp. 21-38.

Loyd, R.C., 2004, Liquefaction zones of required investigation in the Lancaster West 7.5-Minute quadrangle, Los Angeles County, California: California Geological Survey Seismic Hazard Zone Report 95, Section 1, pp. 3-20.

Miller, F.K., and Morton, D.M., 1980, Potassium-argon geochronology of the eastern Transverse Ranges and southern Mojave Desert, south ern California: U.S. Geological Survey Professional Paper 1152, 30 p.

Orme, A.R., 2008, Lake Thompson, Mojave Desert, California: The late Pleistocene lake system and its Holocene dessication: Geological Society of America, Special Paper 439, pp. 261-278.

Ponti, D.J., 1985, The Quaternary alluvial sequence of the Antelope Valley, California, in Weide, D.L., and Faber, M.L., editors, Soils and Quaternary geology of the southwestern United States: Geological Society of America, Special Paper 203, p. 79-96.

______, 1980, Stratigraphy and engineering characteristics of upper Quaternary sediments in the eastern Antelope Valley and vicinity, California: M.S. thesis, Stanford University, California, 157 p., Plates 1-4, scale 1:62,500.

Ponti, D.J., Burke, D.B., and Hedel, C.W., 1981, Map showing Quaternary geology of the central Antelope Valley and vicinity, California: U.S. Geological Survey Open-File Report 81-737, scale 1:62,500.

Ross, D.C., 1976, Metagraywacke in the Salinian block, central Coast Ranges, California – and a possible correlative across the San Andreas Fault: U.S. Geological Survey, Journal of Research, v. 4, no. 6, p. 683-696.

Silver, L.T., 1971, Problems of crystalline rocks of the Transverse Ranges: Geological Society of America Abstracts with Programs vol. 3, p. 193-194.

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.

0°40'12 MILS

13°231 MILS

GNMN

UTM GRID AND 2010 MAGNETIC NORTHDECLINATION AT CENTER OF SHEET

0

0

0

1

1

1.5

.5 2

2

2Thousand Feet

Kilometers

Miles

Scale 1:24,000

Contour Interval 5 feetNational Geodetic Vertical Datum of 1929

5

COTTONWOODCR

SANTA CLARA R

99

Bouquet Res

Elderberry 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

AguaDulce

Castaic

48

166

58

126

14

138

118°0'0"W118°30'0"W119°0'0"W35

°0'0

"N34

°30'

0"N

5Kilometers

5Miles

GRAPEVINE

PASTORIA

RIDGE

TWINS

TYLERHORSE

WILLOW

SOLEDAD

BISSELL

ROSAMOND

ROSAMOND

LITTLE

FAIRMONT

NEENACH

LA LIEBRE

LEBEC

FRAZIER

MOUNTAIN

BLACKMOUNTAIN

BURNT

LAKE SUR

LANCASTER

PALMDALE

SLEEPY

GREEN

WARM

WHITAKER

COBBLESTONE

PEAK

WINTERS

LIEBRE

CANYON

SPRINGS

MOUNTAIN

MOUNTAIN

SCHOOL

RANCH

BUTTE

BUTTES

LAKEEAST

DEL

HUGHES

PEAK

LIEBRE

MOUNTAIN

ALAMO

HEARTDEVILS

MOUNTAIN

PEAK

SPRINGS

MOUNTAIN

VALLEY

VALLEY

RIDGERITTER

CREEK

LANCASTER

WEST

QuartzSyenite

QuartzMonzonite

QuartzMonzodiorite

Syenite Monzonite Monzodiorite

Granite

Alka

li-fe

ldsp

ar G

rani

te

Tonalite

Diorite

Syen

ogra

nite

Granodioriteno

Mnargoz

eti

Quartz

Diorite

90 65 35 10

5

20

60Q Q

A P

60

20

5

Classification of plutonic rock types (from Streckeisen, 1973; 1976). A, alkali feldspar; P, plagioclase feldspar; Q, quartz.

CORRELATION OF MAP UNITS

af Qw Qa QeQc

Qya Qyp Qyfs Qyf

Qof

Qf

Qyfc

}db

Kgr

}pos

Holocene

}Pleistocene

}

Paleocene

} }}

}QUATERNARY

CENOZOIC

MESOZOIC

TERTIARY

CRETACEOUS

afArtificial fill and disturbed areas (Holocene, historic) – Surfaces intensely modified by human construction and grading activities. 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.

QaModern alluvium (Holocene) – Unconsolidated to weakly consolidated, fluvial gravel, sand, and silt. Loose, yellowish-gray to brown (10YR 4/3) sand, silt, and pebble-cobble gravel. Consists predominately of moderately sorted medium- to very coarse-grained arkosic sand.

Colluvium (Holocene to late Pleistocene) – Unconsolidated sand, gravel, and rock fragments flanking bedrock slopes. Deposited by down-slope creep or rain wash. Mapped where thick and continuous enough to obscure underlying bedrock.

Qc

Younger alluvium (Holocene to Late Pleistocene) – Unconsolidated, dark-yellowish-brown (10YR 4/4) sand and gravel of slightly dissected alluvial fans and associated washes.Qya

Qyf Younger alluvial fan deposits (Holocene to late Pleistocene) – Unconsolidated to weakly consolidated, dark- yellowish-brown (10YR 4/4), fine- to medium-grained arkosic sand with fine gravel. Gravels are primarily from a granitic source, with many subangular quartz fine gravel clasts. Unit is exposed as slightly dissected, elevated alluvial fans.

Qyfs Younger alluvial fan deposits, silt rich (Holocene to late Pleistocene) – Consolidated, brown (10YR 4/3) to dark- yellowish-brown (10YR 4/6), silty, fine arkosic sand. Some clay coatings on roots and rootlets. Deposits are generally distal fan sediments.

Qyp Younger playa deposits (Holocene to late Pleistocene) – Moderate to well consolidated, clay with some silt. Soils generally light-grayish-brown to brown when moist, 10YR 5/3, with upper soil profile showing laminations, and occasional pinhole porosity. Lacustrine silt and clay deposits with minor loose, well-sorted sand and fine gravel deposited in the shallow-water regions of the last pluvial lake that filled the lowland parts of Antelope Valley up to about 12,000 years ago. Deposits are generally covered with a veneer of loose sand and silt.

}dbDiabase dikes (early Tertiary to Mesozoic?) – Black to dark-brown diabase dikes. Common in Portal Schist unit, especially within Quartz Hill in the south central map area. Fine-grained groundmass, with fine phenocrysts of plagioclase and hornblende. Resistant outcrops cross-cut Portal Schist. Occasionally seen in unit Kgr, too small to map.

Kgr Granitic rocks (Late Cretaceous) – Monzogranite to quartz-monzonite in composition, light-tan to light-gray, medium- grained, some what incoherent where weathered. Moderately foliated. Late Cretaceous age assumed from r egional work by Miller and Morton, 1980. Mapped as quartz monzonite by Dibblee (1960), and granodiorite by Evans (1978).

}posPortal Schist (Late Cretaceous - earliest Tertiary) – Quartzo-feldspathic and biotite schist; schist is partially re-crystallized, and has strong foliation with quartz augen layering and quartz veins parallel to foliation. Amphibolite, marble, vein quartz and quartzite layering are common, with minor talc-actinolite schist and graphite. Unit is fine-grained, composed largely of albite, plagioclase and biotite. Noted as typical amphibo lite facies of metamorphism. Unit is highly folded, with detached intrafolial folds common.

Qyfc Younger alluvial fan deposits, clay rich (Holocene to late Pleistocene) – Consolidated, dark-yellowish-brown (10YR 4/3 to 4/4), silty, fine arkosic sand with clay and calcium carbonate content. Carbonate likely deposited during fluctuating groundwater conditions of former pluvial Lake Thompson stands. Deposits are generally distal fan sediments near edges of former lake shoreline.

Older alluvial fan deposits (late Pleistocene) – Moderately consolidated, strong brown (7.5YR 4/6 to 5/6), medium dense, fine- to medium-grained arkosic sand with fine to medium gravel. Gravels predominately fine to medium, sub-rounded granitic clasts. Clay coatings on grains and clasts predominant. Crude bedding observed with basal gravel layers.

Qof

SURFICIAL UNITS

METAMORPHIC AND INTRUSIVE ROCKS

DESCRIPTION OF MAP UNITS

Wash deposits (late Holocene) – Unconsolidated fine- to medium-grained sand, with some coarse sand and fine gravel, and silt. Deposits are generally pale-brown (10YR 5/3), angular to sub-angular grains, derived from local bedrock, or reworked from other local Quaternary sources. Subject to localized reworking and new sediment deposition during storm events.

Qw

Eolian deposits (Holocene) – Unconsolidated windblown deposits of very fine- to medium-grained, subangular, arkosic sand with some silt. Deposits are loose, generally light-gray where predominately sand, to dark- yellowish-brown (10YR 4/4) with increased silt content. Thickness estimated up to 2 m.

Qe

Qf Modern alluvial fan deposits (Holocene) – Unconsolidated to weakly consolidated, poorly sorted, rubble, 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.

Preliminary Geologic Map available from:http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm

Revised: 09/24/2010