Please Note: This is an archived website. It is recommended to search on-line for revised or newer information.
Link to USGS Home Page CGS home USGS home


Find Geologic Maps


Southern California Geology

Links and Resources

Site Contents

Contact Us

Southern California Geology


Surficial Geologic Materials in Southern California


Surficial materials--geologic materials that have accumulated at the land surface over the last one million years or so--are widespread throughout southern California. These are relatively unconsolidated materials that mantle the ground surface of valleys and hillslopes, or that form the uppermost fillings of valleys and alluvial fans. Typical examples include:


  • sand and gravel deposits that occur in river and creek bottoms or that form valley floors;
  • loose rubble that lies on hillslopes;
  • landslides and other slope-failure materials that occur on hillsides;
  • wind-deposited sand dunes and sand sheets.

The Southern California Areal Mapping Project (SCAMP) is developing a uniform scheme to classify and map the myriad different types of surficial materials that occur in southern California. The provisional classification uses three kinds of information to distinguish among geologic-map units of such deposits:

  • physical properties and lithologic features (including consolidation and induration, depositional fabric, grain size, sorting, bed forms, matrix support versus grain support);
  • geologic age (as determined from pedogenic-soil characteristics, desert varnish and pavement, vegetation, degree of incision, radiometric analyses, paleontology, magnetostratigraphy);
  • genesis and geomorphic setting (physiographic setting) and mode of origin (alluvial-fan, slope-wash, pediment-veneer, estuarine, etc.).

Inclusion of geologic origin (genesis) as a classification factor runs counter to the way most geologic materials are classified. With most classifications, descriptive features are used to define similarities or differences among geologic items; highly interpretive and derivative criteria such as genesis are avoided. However, the use of genetic criteria as a basis for the classification and mapping of surficial materials in southern California is inescapable because the materials are forming right before our eyes: we can observe how the natural setting and geologic origin of the materials determines their physical properties. Thus, it is useful to include genetic factors in the differentiation of these materials.

blue line
Southern California Areal Mapping Project logo
SCAMP Home Page
USGS Geology, Minerals, Energy, and Geophysics
California Geological Survey
USGS Home || Search USGS

blue line

  U.S. Department of the Interior, U.S. Geological Survey
Maintainer: WESP team webmaster contact
Privacy Statement || Disclaimer || Accessibility
This site last updated September 3, 2004 (ps)

First Gov