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Open-File Report 97-97

Quaternary geology of Alameda County, and parts of Contra Costa, Santa Clara, San Mateo, San Francisco, Stanislaus, and San Joaquin Counties, California: A digital database

By E.J. Helley and R.W. Graymer

Thumbnail of and link to report PDF (181 kB)Summary

Alameda County is located at the northern end of the Diablo Range of Central California. It is bounded on the north by the south flank of Mount Diablo, one of the highest peaks in the Bay Area, reaching an elevation of 1173 meters (3,849 ft). San Francisco Bay forms the western boundary, the San Joaquin Valley borders it on the east and an arbitrary line from the Bay into the Diablo Range forms the southern boundary. Alameda is one of the nine Bay Area counties tributary to San Francisco Bay. Most of the country is mountainous with steep rugged topography. Alameda County is covered by twenty-eight 7.5' topographic Quadrangles which are shown on the index map.

The Quaternary deposits in Alameda County comprise three distinct depositional environments. One, forming a transgressive sequence of alluvial fan and fan-delta facies, is mapped in the western one-third of the county. The second, forming only alluvial fan facies, is mapped in the Livermore Valley and San Joaquin Valley in the eastern part of the county. The third, forming a combination of Eolian dune and estuarine facies, is restricted to the Alameda Island area in the northwestern corner of the county.

Updated October 5, 2005

  • Database TAR.Z (18.6 MB)
    The database package in ARC/INFO 7.x uncompressed export format along with supporting materials in a compressed UNIX tar file
  • Maps TAR.Z (11.3 MB)
    Three Postscript plottable files containing images of the geologic maps and base maps at a scale of 1:100,000, explanation sheet, and explanatory text in a compressed UNIX tar file

For additional information, contact:
Geology, Minerals, Energy, and Geophysics Science Center
U.S. Geological Survey
345 Middlefield Road, MS 901
Menlo Park, CA 94025-3591
http://geomaps.wr.usgs.gov/gmeg/

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Suggested citation:

Helley, E. J., Graymer, R. W., 1997, Quaternary geology of Alameda County, and parts of Contra Costa, Santa Clara, San Mateo, San Francisco, Stanislaus, and San Joaquin Counties, California: A digital database: U. S. Geological Survey Open-File Report 97-97, 13 pp., https://pubs.usgs.gov/of/1997/0097/.



 


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