Digital geologic map and map database of parts of Marin, San Francisco, Alameda, Contra Costa, and Sonoma Counties, California

This database and accompanying plot files depict the distribution of geologic materials and structures at a regional (1:62,500) 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 This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area.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 (mageo.txt, mageo.pdf, or mageo.ps), 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 1:62,500 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 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. Revisions: 8/31/99 This is the pre-release version of the report. There have been no revisions to any part of the report. Data Revision List > File Report Version Last Update > Last Updated > > mamap.ps 1.0 > maexpl.ps 1.0 > mageo.ps 1.0 > mamap.pdf 1.0 > maexpl.pdf 1.0 > mageo.pdf 1.0 > ma-geol.e00 1.0 > ma-strc.e00 1.0 > ma-blks.e00 1.0 > ma-altr.e00 1.0 > ma-quad.e00 1.0 > ma-corr.e00 1.0 > ma-so.e00 1.0 > ma-terr.e00 1.0 > mageo.txt 1.0 > mafig1.tif 1.0 > mafig2.tif 1.0 > madb.ps 1.0 > madb.pdf 1.0 > madb.txt 1.0 > import.aml 1.0 > mageol.met 1.0 Reviews_Applied_to_Data: This report has undergone two scientific peer reviews, one digital database review, one review for conformity with geologic names policy, and review of the plotfiles for conformity with USGS map standards. Related_Spatial_and_Tabular_Data_Sets: This report consists of a set of geologic map database files (Arc/Info coverages) and supporting text and plotfiles. In addition, the report includes two sets of plotfiles (PostScript and PDF format) that will generate map sheets and pamphlets similar to a traditional USGS Miscellaneous Field Studies Report. These files are described below: > ARC/INFO Resultant Description of Coverage > export file Coverage > ----------- ----------- -------------------------------- > ma-geol.e00 ma-geol/ Polygon and line coverage showing faults, > depositional contacts, and rock units > in the map area. > > ma-strc.e00 ma-strc/ Point and line coverage showing strike and dip > information and fold axes. > > ma-blks.e00 ma-blks/ Point coverage showing location of high-grade > blocks in Franciscan rock units. > > ma-altr.e00 ma-altr/ Polygon coverage showing areas of hydrothermal > alteration. > > ma-quad.e00 ma-quad/ Line coverage showing index map of quadrangles > in the map area. Lines and annotation only. > > ma-corr.e00 ma-corr/ Polygon and line coverage of the correlation > table for the units in this map database. > This database is not geospatial. > > ma-so.e00 ma-so/ Line coverage showing sources of data index > map for this map database. > > ma-terr.e00 ma-terr/ Polygon and line coverage of the index map of > tectonostratigraphic terranes in the map area. > (Terranes are described in mageo.txt, > mageo.ps, or mageo.pdf). ASCII text files, including explanatory text, ARC/INFO key files, PostScript and PDF plot files, and a ARC Macro Language file for conversion of ARC export files into ARC coverages: > mageo.ps A PostScript plot file of a report containing > detailed unit descriptions and geological > information, plus sources of data and references > cited, with two figures. > > mageo.pdf A PDF version of mageo.ps. > > mageo.txt A text-only file containing an unformatted > version of mageo.ps without figures. > > mafig1.tif A TIFF file of Figure 1 from mageo.ps > > mafig2.tif A TIFF file of Figure 2 from mageo.ps > > madb.ps A PostScript plot file of a pamphlet containing > detailed information about the contents and > availability of this report. > > madb.pdf A PDF version of madb.ps. > > madb.txt A text-only file containing an unformatted > version of madb.ps. > > import.aml ASCII text file in ARC Macro Language to convert > ARC export files to ARC coverages in ARC/INFO. > > mamap.ps A PostScript plottable file containing an image > of the geologic map and base maps at a scale of > 1:62,500, along with a simple map key. > > maexpl.ps A PostScript plot file containing an image of > the explanation sheet, including terrane map, > index maps, correlation chart, and unit > descriptions. > > mamap.pdf A PDF file containing an image of the geologic > map and base maps at a scale of 1:62,500, along > with a simple map key. > > maexpl.pdf A PDF file containing an image of the > explanation sheet, including terrane map, index > maps, correlation chart, and unit descriptions. Base maps Base Map layers used in the preparation of the geologic map plotfiles were derived from published digital maps (Aitken, 1997) obtained from the U.S. Geological Survey Geologic Division Website for the Western Region (http://wrgis.wr.usgs.gov). Please see the website for more detailed information about the original databases. Because the base map digital files are already available at the website mentioned above, they are not included in the digital database package.