Coverage of DRECP 12 km buffered study site, clipped from original USGS data "Preliminary integrated geologic map databases for the United States" found at
http://pubs.usgs.gov/of/2005/1305/. This digital map is a reformulation of previously published maps, primarily maps of states. The reformulation gives all the maps the same structure and format, allowing them to be combined into regional maps. The associated data tables have information about age and lithology of the map units, also in a standard format.