U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY PRELIMINARY GEOLOGIC MAP EMPHASIZING BEDROCK FORMATIONS IN CONTRA COSTA COUNTY, CALIFORNIA: A DIGITAL DATABASE Compiled by R.W. Graymer, D.L. Jones, and E.E. Brabb Open - File Report 94-622 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. This database, identified as "Preliminary geologic map emphasizing bedrock formations in Contra Costa County, California: A digital database," has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use. 1994 Introduction This digital map database, which is compiled from previously published and unpublished sources combined with new mapping, represents the general distribution and identity of bedrock in Contra Costa County, California. Together with the accompanying text file (ccgeo.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, and stratigraphic nomenclature. Quaternary units, however, are almost all combined into an undifferentiated unit, with the exception of Pleistocene gravels (Qmz) and several landslides on Mount Diablo (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. For those interested in the geology of Contra Costa County who do not use an ARC/INFO compatible Geographic Information System (GIS), we have included two Postscript plot files containing images of much of the data included in the digital database. The content and character of the database, as well as two methods of obtaining the database are described briefly below. A more detailed description of the database is included with it. Database Contents The digital database consists of the geologic map database itself and the supporting data, including index maps, base maps, map explanation, sources of data, and references. The geologic map database consists of two ARC coverages: cc_utm/ Faults, depositional contacts, and rock unit identities cc_sr/ Fold axes, strike and dip information The database directory also includes the following supporting directory, ARC coverages, and files: Directory: info/ INFO directory containing files supporting the databases ARC Coverages: cc-flt_utm and cc-flt_ano Together, these ARC coverages contain a fault map of Contra Costa County with major faults labeled. cc_dr/ Drainage base map. cc_cu/ Cultural base map. cc_topo/ Topographic contours base map. cc_so/ Index map of sources of data (see ccsource.txt) cc_as/ Index map of Assemblages in Contra Costa County (see ccgeo.txt for explanation of Assemblages). cc_quad/ and cc-quad_ano Together, these ARC coverages contain an index map of 7.5 minute quadrangles in Contra Costa County. cc-corr_utm/ This ARC coverage contains a correlation table for the units in these maps. Files: cckey.un cckey.mrk and cckey.ln Together, these key files produce a plottable or displayable map explanation and key. ccgeo.txt A text file containing detailed unit descriptions and geological information. ccdb.txt A detailed description of the contents and character of this database. ccsource.txt A text file containing references for data sources corresponding to areas outlined in the index map cc_so/. ccref.txt A text file containing a complete reference list for all parts of this database. ccmap.ps A Postscript plottable file containing an image of the geologic maps andbase maps at a scale of 1:75,000. ccexpl.ps A Postscript plottable file containing an image of the fault map, map keys, and index maps for Contra Costa County. The database was compiled in ARC/INFO, a commercial Geographic Information System (Environmental Systems Research Institute, Redlands, California), and is stored in ARC coverage format (ARC/INFO version 6) in a UNIX tar file. A UNIX computer system is therefore required to extract the database from the tar file, and ARC/INFO is required for its use or conversion to other formats. The digital compilation was done using version 6.1.1 of ARC/INFO with version 2.0 of the menu interface ALACARTE (Fitzgibbon and Wentworth, 1991, Fitzgibbon, 1991, Wentworth and Fitzgibbon, 1991). Obtaining the Digital Data A 21.3 MB compressed tar file of the database and related files can be obtained by anonymous ftp over Internet, or by sending a tape with request and return address to: Contra Costa Geologic Database c/o Carl M. Wentworth U.S. Geological Survey Do not omit any part of this 345 Middlefield Road, M/S 975 address Menlo Park, CA 94025 The compressed tar file will be returned on the tape. The acceptable tape types are: 1/4 inch, 150 MB cartridge tape 2.3 or 5.0 GB, 8 mm Exabyte tape. To obtain the tar file by ftp, log in to your UNIX system and do the following: cd local_directory -go to a directory to receive the tar file ftp sierra.wr.usgs.gov -make ftp connection with the USGS computer Sierra Name: anonymous -use "anonymous" as your user name Password: your name -use your own user name as password cd pub -go down to the pub directory type binary -change transfer type to binary get cc_g1.tar.Z -copy the compressed tar file across Internet to your directory quit -close the ftp connection Extracting the Database from the Tar file If you obtained the database on tape: put the tape in your tape drive cd local_directory -go to a directory to receive the tar file tar xvfb /dev/rstn 20 -/dev/rstn is the tape device with n an integer this puts the tar file in local_directory uncompress cc_g1.tar.Z -makes a 56 MB uncompressed tar file cc_g1.tar cd local_directory2 -go to the directory that will hold the workspace ccgeo (if different from local_directory) tar xvfb {path to tar file}/cc_g1.tar 20 -extract the ccgeo workspace from the tar file. If you obtained the database by anonymous ftp: uncompress cc_g1.tar.Z -makes a 56 MB uncompressed tar file cc_g1.tar cd local_directory2 -go to the directory that will hold the workspace ccgeo (if different from local_directory) tar xvfb {path to tar file}/cc_g1.tar 20 -extract the ccgeo workspace from the tar file. This process will create a workspace "/ccgeo" (a directory containing an INFO directory) that contains the databases and supporting files as described above. Postscript Plot Files The database is in ARC coverage format, and therefore requires use of ARC/INFO or compatible GIS system to access the information contained within it. For those interested in the geology of Contra Costa County, but who don't use an ARC/INFO compatible GIS system, we have included two Postscript plot files. One contains a plot of the map database, and the other contains a plot of much of the supporting data. Because this release is primarily a digital database, the plot files (and plots derived therefrom) have not been edited to conform to U.S. Geological Survey standards. Fold axes are undifferentiated, small units are unlabled, dip numbers are plotted an arbitrary distance from strike and dip symbols, and in some instance map features or annotation overlap. Preliminary plots by us have proved to be quite legible and usable, and so the plot files have been included in this release. The Postscript images are 44 inches wide by 34 inches high, to conform to the plotter we use at Menlo Park, so they require a large plotter to obtain paper copies at the intended scale. In addition, some plotters, such as those with continual paper feed from a roll are oriented with the long axis in the vertical direction. The postscript image will probably have to be rotated 90 degrees to fit entirely onto the page. Some plotters and plotter drivers have the ability to perform this rotation. In addition, many software packages that handle graphics will accept Postscript files and may be used to rotate the image. direction