Preliminary geologic map emphasizing bedrock formations in Alameda County, California: A digital database

This digital map database, compiled from previously open-filed U.S. Geological Survey reports (Graymer and others, 1994), other published and unpublished data and substantialnew mapping by the authors in about two-thirds of the county, represents the general distribution of rocks and geologic structures in Alameda County. Together with the accompanying text file (algeo.txt), it provides current information on the stratigraphy and structural geology of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. Quaternary units are almost all combined into an undifferentiated unit, with the exception of some artificial deposits (Qar), some early Holocene or late Pleistocene gravel deposits (Qt, Qoa) and a few large landslides (Qls). More specific information about the units may be available in the original publications. The scale of the source maps limits the spatial resolution (scale) of the database to 1:50,000 or smaller. The digital database consists of the geologic map database itself and the supporting data, including a fault map, base maps, map explanation, geologic description, and references. The digital maps, or coverages, along with their associated INFO directory have been converted to ARC/INFO export files. The database components may be downloaded from the following URL: "http://pubs.usgs.gov/of/1996/of96-252/".