Older Quaternary alluvium and marine deposits

Older alluvium, lake, playa, and terrace deposits.
State California
Name Older Quaternary alluvium and marine deposits
Geologic age Pleistocene
Lithologic constituents
Unconsolidated > Coarse-detrital (Alluvial, Terrace, Bed)
Unconsolidated > Fine-detrital (Lacustrine, Bed)
Comments from the 2010 data source metadata: The depiction of Quaternary geologic units on the original map by Jennings (1977) was simplified by the author who noted that "various surficial deposits of Quaternary age are lumped into the unit 'Q'." Since Jennings' work, subdivisions of these deposits have been found to have very different potential for liquefaction and for amplification of seismic shaking. Relative age of Quaternary alluvial fan deposits have also been found to correlate with potential for flooding. Since these units are important for evaluation of geologic hazards, the 2010 update of the geologic map includes a subdivision of Jennings "Q" into younger alluvium "Q" and older alluvium "Qoa".

Jennings, C.W., with modifications by Gutierrez, C., Bryant, W., Saucedo, G., and Wills, C., 2010, Geologic map of California, Version 2.0 (California Geological Survey 150th Anniversary Edition), Department of Conservation, California Geological Survey: California Geologic Data Map Series, GDM No. 2, scale 1:750,000.

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