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Southern California Areal Mapping Project

 

Geologic Framework of the Los Angeles Basin

| Selected References | Find geologic maps & digital data |

SCAMP is currently conducting geologic-mapping, topical, geochronologic, and geophysical investigations to clarify the geologic setting and geologic history of the Los Angeles Basin. The goal is to describe the physical properties of rock and sediment, determine the long-term geologic history of the Basin, and to provide a geologic-map basis for evaluating geologic hazards and for investigating hydrogeologic resources.


Geologic-mapping Investigations

For the last few years, SCAMP has been releasing digital compilations of individual 1:24,000-scale 7.5' geologic quadrangles that comprise the Los Angeles 30' x 60' 1:100,000-scale quadrangle (Yerkes and others, 1998). The objective is to provide a uniform classification of geologic units and physical properties throughout the 100K quadrangle.

Recent SCAMP Products

Campbell, R.H., Blackerby, B.A., Yerkes, R.F., Schoellhamer, J.E., Birkeland, P.W., and Wentworth, C.M., 1996, Geologic Map of the Point Dume quadrangle, Los Angeles County, California: U.S. Geological Survey Map GQ-1747, scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1995, Preliminary geologic map of the Fillmore quadrangle, southern California: U.S. Geological Survey Open-File Report 95-502 (digital release OFR 95-802), scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1995, Preliminary geologic map of the Newhall quadrangle, southern California: U.S. Geological Survey Open-File Report 95-503 (digital release OFR 95-800), scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1995, Preliminary geologic map of the Val Verde quadrangle, southern California: U.S. Geological Survey Open-File Report 95-504 (digital release OFR 95-699), scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1995, Preliminary geologic map of the Piru quadrangle, southern California: U.S. Geological Survey Open-File Report 95-511 (digital release OFR 95-801), scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1996, Preliminary geologic map of the Burbank quadrangle, southern California: U.S. Geological Survey Open-File Report 96-253, (digital release OFR 97-166), scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1996, Preliminary geologic map of the Moorpark quadrangle, southern California: U.S. Geological Survey Open-File Report 95-827 (digital release OFR 97-260), scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1996, Preliminary geologic map of the Santa Susana quadrangle, southern California: U.S. Geological Survey Open-File Report 95-829 (digital release OFR 97-258), scale 1:24,000.

Yerkes, R.F., and Campbell, R.H., 1996, Preliminary geologic map of the Simi quadrangle, southern California: U.S. Geological Survey Open-File Report 95-828 (digital release OFR 97-259), scale 1:24,000.

Yerkes, R.F., compiler, 1996, Preliminary geologic map of the Mint Canyon quadrangle, southern California: U.S. Geological Survey Open-File Report 96-89 (digital release OFR 97-164), scale 1:24,000.

Yerkes, R.F., compiler, 1996, Preliminary geologic map of the San Fernando quadrangle, southern California: U.S. Geological Survey Open-File Report 96-88 (digital release OFR 97-163), scale 1:24,000.

Yerkes, R.F., compiler, 1996, Preliminary geologic map of the Sunland quadrangle, southern California: U.S. Geological Survey Open-File Report 96-87 (digital release OFR 97-270), scale 1:24,000.

Yerkes, R.F., compiler, 1996, Preliminary geologic map of the Van Nuys quadrangle, southern California: U.S. Geological Survey Open-File Report 96-86 (digital release OFR 97-165), scale 1:24,000.

Yerkes, R.F., compiler, 1997, Preliminary geologic map of the Beverly Hills 7.5' quadrangle, southern California: U.S. Geological Survey Digital Open-File Report 97-430.

Yerkes, R.F., compiler, 1997, Preliminary geologic map of the Hollywood 7.5' quadrangle, southern California: U.S. Geological Survey Digital Open-File Report 97-431.

Yerkes, R.F., compiler, 1997, Preliminary geologic map of the Los Angeles 7.5' quadrangle, southern California: U.S. Geological Survey Digital Open-File Report 97-432.

Yerkes, R.F., and Campbell, R. H., 1997, Geologic map of the Malibu Beach 7.5' quadrangle, southern California: U.S. Geological Survey Digital Open-File Report 97-257.

Yerkes, R.F., and Campbell, R. H., 1997, Geologic map of the Point Dume 7.5' quadrangle, southern California: U.S. Geological Survey Digital Open-File Report 97-276.

Yerkes, R.F., and Campbell, R. H., compilers, 1997, Preliminary geologic map of the Newbury Park 7.5' quadrangle, southern California: U.S. Geological Survey Open-File Report 97-428 (digital release OFR 97-459).

Yerkes, R.F., and Campbell, R. H., compilers, 1997, Preliminary geologic map of the west half, Los Angeles 60' x 30' quadrangle: U.S. Geological Survey Open-File Report 97-483, 2 sheets, scale 1:100,000.

Yerkes, R.F., Campbell, R.H., and Graham, Scott, 1998, Digital geologic map of the Los Angeles 60' x 30' quadrangle: Geological Society of America Abstracts with Programs, v. 30, no. 5, p. 71.


Basin-Framework Investigations

SCAMP is supporting surface and subsurface investigations designed to clarify the geologic framework and geologic history of the Los Angeles Basin. Research emphasizes:

 

  • Gravity and rock-density investigations of the deep Los Angeles Basin. The density/porosity model of the basin sedimentary fill will be used to improve models of seismic response to strong earthquakes;
  • Strontium-isotope studies of shelly fossils and radiometric-isotope studies of volcanic rocks, both designed to improve geochrono-logic control on Basin events;
  • Paleontologic studies of fossil foraminifers and mollusks;
  • Paleomagnetic studies to determine age of sedimentary and volcanogenic sequences

The basin-framework investigations have the following objectives:

 

  • To outline Jurassic through Oligocene paleogeographic and structural events prior to Miocene development of the LA Basin;
  • To refine the structural and stratigraphic evolution of the Miocene LA Basin proper, as this history relates to regional geologic events such as extension in the greater Mojave-Sonora Desert province and rotation of the western Transverse Ranges;
  • To clarify the history and tectonic role of bounding structures that separate the LA Basin fill from crystalline rocks of the Transverse Ranges, Peninsular Ranges, and Continental Borderland;
  • To clarify tectonic and paleogeographic relations among time-equivalent sedimentary fills in the Ventura Basin and the Santa Monica and Santa Ana Mountains;
  • To determine the Quaternary tectonic evolution of the LA Basin area in the context of the overall San Andreas transform-fault system.

Geologic information developed in support of these objectives is applicable to a wide range of societal issues--including evaluations of energy, water, and nonmetallic mineral resources and analysis of geologic hazards associated with faults, folds, and landslides. Geologic features of economic and social significance include major petroleum resources in the Los Angeles Basin, and numerous faults and contractional folds of the San Andreas transform-fault system-including the San Andreas and San Gabriel faults, the Malibu-Santa Monica-Raymond Hill fault zone, the frontal fault zone of the San Gabriel Mountains, and buried blind thrusts that caused the 1993 Northridge earthquake.

Recent SCAMP Products

 

Beyer, L. A. and McCulloh, T. H., 1998, Bulk densities and porosities of Cenozoic and Cretaceous basin-filling strata and Cretaceous and older basement rocks of the Los Angeles basin, California, determined from measurements of core samples: U. S. Geological Survey Open-File Report 98-788, 197 p.

Hillhouse, J. W., 1997, Magnetic Stratigraphy of Plio-Pleistocene sediments of the Los Angeles Basin, California: Society for Sedimentary Geology (SEPM), Pacific Section Annual Convention, Bakersfield, California (May 14-16, 1997), Convention Program, p. 37.

McCulloh, T. H., Beyer, L. A., and Enrico, R. J., 2000, Paleogene strata of the eastern Los Angeles basin, California: Paleogeography and constraints on Neogene structural evolution: Geological Society of America Bulletin, v.112, p. 1155-1178.

McCulloh, T. H., Beyer, L. A., and Morin, R.W. 2001, Mountain Meadows Dacite: Oligocene intrusive complex that welds together the Los Angeles Basin, northwestern Peninsular Ranges, and central Transverse Ranges, California: U.S. Geological Survey Professional Paper 1649, 34 p.

McCulloh, T. H., Fleck, R. J, Denison, R. E., Beyer, L. A., and Stanley, R. G., 2002, Age and tectonic significance of volcanic rocks in the northern Los Angeles Basin, California: U.S. Geological Survey Professional Paper 1669, 24 p.


Geophysical Investigations

SCAMP is co-sponsoring geophysical studies of the Los Angeles Basin that will lead to a 3-D geologic/structural/physical-property model. This model will provide a basis for estimates of seismic velocity in various geologic media, which in turn will be used for earthquake ground-shaking estimates, for ground-water flow modeling, and for estimates of potential for groundwater recharge. The geophysical work is closely coordinated with, and has parallel tasks in, the USGS Earthquake Hazards Program Southern California Project and Water Resources Division.

Recent SCAMP Products

Langenheim, V.E., and Jachens, R.C., 1996, Aeromagnetic map of the Long Beach 1:100,000-scale quadrangle, California: U.S. Geological Survey Open-File Report 96-287.

Langenheim, V.E., and Jachens, R.C., 1996, Gravity data collected along the Los Angeles Regional Seismic Experiment (LARSE) and preliminary model of regional density variations in basement rocks, southern California: U.S. Geological Survey Open-File Report 96-682, 25p.

Langenheim, V.E., and Jachens, R.C., 1997, Aeromagnetic map of the Los Angeles 1:100,000-scale quadrangle, California: U.S. Geological Survey Open-File Report 97-162.

Langenheim, V.E., and Jachens, R.C., 1996, Aeromagnetic map of the Long Beach 1:100,000-scale quadrangle, California: U.S. Geological Survey Open-File Report 96-287.

Langenheim, V.E., Griscom, Andrew, and Jachens, R.C., 1994, Gravity and magnetic data help image the regional tectonic setting of the 1994 Northridge earthquake: Annual meeting, Seismology Society of America, Pasadena, CA, April 4-6, 1994.


Cooperative Interactions

SCAMP geologic investigations in the Los Angeles Basin are coordinated with several USGS projects, with the California Division of Mines and Geology, and with various State and County agencies. These cooperative investigations include:

Geologic Framework for Quaternary Surficial Materials

Large areas of the Los Angeles Basin region are underlain by surficial deposits of clay, silt, sand, and gravel deposited during the last 2 million years by rivers that coursed across the basin to the ocean. The boundary between ocean (marine) deposits and river-plain (nonmarine) deposits shifted back and forth during this period, as did the boundaries between various types of flood-plain and marsh and pond deposits. As a result, the subsurface geology of these surficial sediments reveals a complex pattern of marine and nonmarine rock bodies and zones of varying grain size, texture, and permeability.


It is important to understand these subsurface patterns in order to provide geologic insight into ground-water flow, geologic hazards, and faulting and folding history. To this end, the USGS, California Division of Mines and Geology, and several partners are conducting surface and subsurface investigations that include geologic mapping, geological-engineering investigations, subsurface drilling, and paleontologic and paleomagnetic studies. These will shed light on the thickness, composition, physical properties, and geologic history of the surficial materials. Link to a sister USGS project (FOCUS LA) to learn more about subsurface investigations in the Los Angeles Basin region.

SCAMP is interacting with various investigations that focus various aspects of the Quaternary surficial deposits in the Los Angeles Basin:

Fault-activity Investigations

Investigations designed to evaluate earthquake potential on faults within the Los Angeles Basin are led by USGS scientists from the Earthquake Hazards Program and its Southern California office. The USGS earthquake-geology team conducts a variety of fault investigations that contribute to a Fault-Activity Data Base for Southern California, including online release of a fault-activity map of the Long Beach 30' x 60' quadrangle. SCAMP geologic mapping in the Los Angeles 30' x 60' quadrangle will assist the eventual release of the fault-activity map for that quadrangle

Geologic-Hazard Investigations

Within the Los Angeles Basin, the California Division of Mines and Geology (CDMG) has several programs directed toward the recognition and evaluation of geologic hazards imposed by surficial materials and the faults and folds that disturb them:

 

CDMG's Regional Geology and Hazards Mapping Program is conducting earthquake-fault mapping and zonation under the auspices of the State Alquist-Priolo Act identifies fault lines and outlines setback guidelines. Navigate to an Index of Official Maps of Fault Zones to find links to maps available for the Los Angeles Basin region.

CDMG's program of Seismic Hazards Evaluation and Zoning has yielded a growing list of seismic-hazard maps for the Los Angeles Basin region. Link to CDMG's index of planned and available seismic-hazards maps to see a schedule of what is happening in southern California, but especially link to an interactive index of seismic-hazard maps in the greater Los Angeles region to access seismic-hazard maps and evaluation reports. These reports map classify surficial materials using the scheme that SCAMP and CDMG jointly are developing for southern California.

CDMG's Regional Geology and Hazards Mapping Program is conducting geologic mapping of surficial materials in the greater Los Angeles Basin region, including the Long Beach 30' x 60' quadrangle and coastal parts of the Santa Ana 30' x 60' quadrangle. SCAMP has provided geologic mapping to these efforts.

Ground-Water investigations

Within the Los Angeles Basin, the U.S. Geological Survey in cooperation with local and State water agencies like the Water Replenishment District of Southern California is conducting regional ground-water modeling investigations designed to clarify ground-water flow, recharge, and salt-water intrusion. USGS hydrologic investigations are coordinated by the Water Resources Division California District Office, and are led out of the Coastal Area Program and its Central and West Basins Project, Los Angeles County, California. USGS geologic investigations are coordinated by Earthquake Hazards Program personnel, and emphasize subsurface drilling and the analysis of drill core for physical properties, paleontology, and magnetostratigraphy.


SCAMP has interacted with these investigations by conducting paleontologic, biostratigraphic, and magnetostratigraphic investigations that provide age control for Quaternary and late Tertiary sedimentary materials. The paleontologic studies focus on marine microfossils and macrofossils as they bear on biostratigraphic and ecologic zonation. The magneto-stratigraphic studies focus on determining depth to the Brunhes-Matuyama magnetic-reversal event (about 780,000 years B.P.). This work should result in the first true time-calibration of Quaternary and Pliocene sediments in the Los Angeles region.


Cooperative Quaternary Framework studies in the Los Angeles Basin region will lead to the following outcomes:

 

  • A three-dimensional model of how the various kinds of surficial materials are distributed in the subsurface;
  • Age control for regional correlation of surficial units and ground-water aquifers;
  • A reliable estimate of uplift and subsidence rates associated with buried fault zones to constrain hazard assessments;
  • Estimates of sedimentation rates, which in turn will assist in evaluating uplift rates along buried and exposed geologic structures like folds and faults.

 

Recent Cooperative Products

 

Hillhouse, J. W., 1997, Magnetic Stratigraphy of Plio-Pleistocene sediments of the Los Angeles Basin, California: Society for Sedimentary Geology (SEPM), Pacific Section Annual Convention, Bakersfield, California (May 14-16, 1997), Convention Program, p. 37.

Lajoie, K.R., Ponti, D.J., and Powell, C.L., II, 1995, Amino-stratigraphy correlations of surface and subsurface marine Pleistocene sediments in the western Los Angeles Basin. Diversity in engineering geology and groundwater resources, Annual Meeting - Association of Engineering Geologists, v. 38, abstract volume, p. 65. Meeting: AEG-GRA 1995 annual meeting; Diversity in engineering geology and groundwater resources, Sacramento, CA, United States, Oct. 2-8, 1995.

Lajoie, K.R., Ponti, D.J., Powell, C.L. II, Mathieson, S.A., and Sarna-Wojcicki, A.M., 1991, Emergent marine strandlines and associated sediments, coastal California; a record of Quaternary sea-level fluctuations, vertical tectonic movements, climatic changes, and coastal processes, in Morrison, R.B., ed., Quaternary Nonglacial Geology: Conterminous U.S., the Geology of North America, vol. K-2, p. 190-214.

Ponti, D. J., Lajoie, K. R., and Powell, C. L., II, 1991, Upper Pleistocene marine terraces in San Pedro, southwestern Los Angeles Basin, California: implications for aminostratigraphy and coastal uplift. Geological Society of America Abstracts with Programs, v. 23, no. 2, p. 89.

Ponti, D. J., Quinn J. P., Hillhouse, J. W., Powell, C. L., II, (in press), Chronostratigraphy of Pleistocene sediments in the Hancock Park (La Brea Tar Pits) area, Los Angeles, California: Implications for Quaternary deformation and blind-thrust faulting in the northern Los Angeles Basin: U.S. Geological Survey Open-file Report, 22 p.

Ponti, D. J., Quinn, J. P., Hillhouse, J. W., and Powell, C. L., II, 1996, Quaternary chronostratigraphic constraints on deformation and blind-thrust faulting, northern Los Angeles Basin: EOS, Transactions of the American Geophysical Union, v. 77, p. F644.

Ponti, D.J., Barron, J.A., Sarna-Wojcicki, A.M., Cotton, M.L., Hummon, C., and Schneider, C.L., 1994, Benthic foram biostratigraphy and the age of the Pico Formation in the northern Los Angeles Basin: Potential problems for evaluation activity of blind thrust faults (abstract): EOS, Transactions of the American Geophysical Union, v 74, no. 43, p. 434.

Powell, C.L., II, Geologic and molluscan evidence for a previously misunderstood late Pleistocene, cool water, open coast terrace at Newport Bay, southern California. Submitted to The Veliger, 18 ms pp.

Powell, C.L., II, and Stevens, D., in press, Age and paleoenvironmental significance of mollusks from the "San Pedro" Formation, Coyote Hills, Orange County, southern California: Western Society of Malacologists Annual Meeting.

Powell, C.L., II, Ponti, D., and Lajoie, K.A., in press, Preliminary chronostratigraphy for the late Quaternary of southern California based on molluscan biogeography: Western Society of Malacologists Annual Meeting


 

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