Geologic map and map database of the Oakland metropolitan area, Alameda, Contra Costa, and San Francisco Counties, California

This database and accompanying plot files depict the distribution of geologic
materials and structures at a regional (1:24,000) scale. The report is
intended to provide geologic information for the regional study of materials
properties, earthquake shaking, landslide potential, mineral hazards, seismic
velocity, and earthquake faults. In addition, the report contains new
information and interpretations about the regional geologic history and
framework. However, the regional scale of this report does not provide
sufficient detail for site development purposes. In addition, this map does
not take the place of fault-rupture hazard zones designated by the California
State Geologist (Hart and Bryant, 1997). Similarly, the database cannot be
used to identify or delineate landslides in the region.

This digital map database, compiled from previously published and unpublished
data, and new mapping by the authors, represents the general distribution of
bedrock and surficial deposits in the mapped area. Together with the
accompanying text file (oakmf.ps, oakmf.pdf, oakmf.txt), it provides current
information on the geologic structure and stratigraphy 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. The scale of the source maps limits the spatial resolution (scale) of
the database to 1:24,000 or smaller.

The databases in this report were compiled in ARC/INFO, a commercial Geographic
Information System (Environmental Systems Research Institute, Redlands,
California), with version 3.0 of the menu interface ALACARTE (Fitzgibbon and
Wentworth, 1991, Fitzgibbon, 1991, Wentworth and Fitzgibbon, 1991). The files
are in either GRID (ARC/INFO raster data) format or COVERAGE (ARC/INFO vector
data) format. Coverages are stored in uncompressed ARC export format (ARC/INFO
version 7.x). ARC/INFO export files (files with the .e00 extension) can be
converted into ARC/INFO coverages in ARC/INFO (see below) and can be read by
some other Geographic Information Systems, such as MapInfo via ArcLink and
ESRI's ArcView (version 1.0 for Windows 3.1 to 3.11 is available for free from
ESRI's web site: http://www.esri.com ). The digital compilation was done in
version 7.1.1 of ARC/INFO with version 3.0 of the menu interface ALACARTE
(Fitzgibbon and Wentworth, 1991, Fitzgibbon, 1991, Wentworth and Fitzgibbon,
1991). The geologic map information was digitized from stable originals of the
geologic maps at 1:62,500 and 1:24,000 scale. The author manuscripts (pen on
mylar) were scanned using a Altek monochrome scanner with a resolution of 800
dots per inch. The scanned images were vectorized and transformed from scanner
coordinates to projection coordinates with digital tics placed by hand at
quadrangle corners. The scanned lines were edited interactively by hand using
ALACARTE, color boundaries were tagged as appropriate, and scanning artifacts
visible at 1:24,000 were removed.