U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY QUATERNARY GEOLOGY OF ALAMEDA COUNTY, AND PARTS OF CONTRA COSTA, SANTA CLARA, SAN MATEO, SAN FRANCISCO, STANISLAUS, AND SAN JOAQUIN COUNTIES, CALIFORNIA: A DIGITAL DATABASE By E.J. Helley1 and R.W. Graymer1 Open - File Report 97-97 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 "Quaternary geology of Alameda County, and parts of Contra Costa, Santa Clara, San Mateo, San Francisco, Stanislaus, and San Joaquin Counties, 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.1997 1Western Region Mapping Group, U.S. Geological Survey, 345 Middlefield Rd., M/S 975, Menlo Park, CA 94025 Introduction This Open-File report is a digital geologic map database. This pamphlet serves to introduce and describe the digital data. There is no paper map included in the Open-File report. The report does include, however, PostScript plot files containing images of a geologic map sheet and an explanation sheet, as well as the accompanying text describing the Quaternary geology of the area. For those interested in a paper plot of information contained in the database or in obtaining the PostScript plot files, please see the section entitled "For Those Who Don't Use Digital Geologic Map Databases" below. This digital map database, compiled from previously unpublished data, and new mapping by the authors, represents the general distribution of surficial deposits in Alameda County and surrounding areas. Together with the accompanying text file (alqgeo.txt or alqgeo.ps), it provides current information on the quaternary 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 content and character of the database, as well as three methods of obtaining the database, are described below. For Those Who Don't Use Digital Geologic Map Databases For those interested in the Quaternary geology of Alameda County who do not use an ARC/INFO compatible Geographic Information System (GIS), two PostScript plot files containing map images of much of the data in the digital database, as well as PostScript plot files of the explanatory text, have been included in the database package (please see the section "PostScript Plot Files" below). Those interested who have computer capability can access the PostScript plot files in any of the three ways described below to access the digital data (please see the section "Obtaining the Digital Data") including the Western Region Web Page (please see the section "Web Pages"). For those without computer capability, we have made the plot files available to an outside vendor or we can provide users with the PostScript plot files on digital tape that can be used by other vendors (please see the section "Obtaining Plots from an Outside Vendor"). Database Contents The digital database package consists of the geologic map database itself, and the supporting data, including base maps, map explanation, geologic description, and references. A second data package consists of PostScript plot files of a geologic map, explanation sheet, and geologic description. DIGITAL DATABASE PACKAGE The first database package includes a separate geologic map database file for each of the 26 quadrangles with Quaternary deposits in Alameda County. The digital maps, or coverages, along with their associated INFO directory have been converted to uncompressed ARC/INFO export files. ARC export files promote ease of data handling, and are usable by some Geographic Information Systems in addition to ARC/INFO (see below for a discussion of working with export files). The ARC export files and the associated ARC/INFO coverages and directories, as well as the additional digital material included in the database package, are described below: ARC/INFO Resultant Description of Coverage export file Coverage -------------- ------------------------------------------- at_sp-py.e00 at_sp-py Altamont quadrangle bh_sp-py.e00 bh_sp-py/ Byron Hot Springs quadrangle cf_sp-py.e00 cf_sp-py/ Clifton Court Forebay quadrangle cm_sp-py.e00 cm_sp-py Cedar Mtn quadrangle cr_sp-py.e00 cr_sp-py Calaveras Reservoir quadrangle du_sp-py.e00 du_sp-py/ Dublin quadrangle em_sp-py.e00 em_sp-py Eylar Mtn quadrangle ha_sp-py.e00 ha_sp-py Hayward quadrangle hp_sp-py.e00 hp_sp-py Hunters Point quadrangle lc_sp-py.e00 lc_sp-py La Costa Valley quadrangle lt_sp-py.e00 lt_sp-py/ Las Trampas Ridge quadrangle lv_sp-py.e00 lv_sp-py Livermore quadrangle mb_sp-py.e00 mb_sp-py Mt Boardman quadrangle md_sp-py.e00 md_sp-py Mt Day quadrangle mp_sp-py.e00 mp_sp-py Milpitas quadrangle ms_sp-py.e00 ms_sp-py Mendenhall Springs quadrangle mv_sp-py.e00 mv_sp-py Mountain View quadrangle mw_sp-py.e00 mw_sp-py Midway quadrangle ne_sp-py.e00 ne_sp-py Newark quadrangle ni_sp-py.e00 ni_sp-py Niles quadrangle oe_sp-py.e00 oe_sp-py Oakland East quadrangle ow_sp-py.e00 ow_sp-py Oakland West quadrangle ri_sp-py.e00 ri_sp-py/ Richmond quadrangle rp_sp-py.e00 rp_sp-py Redwood Point quadrangle sl_sp-py.e00 sl_sp-py San Leandro quadrangle ta_sp-py.e00 ta_sp-py/ Tassajara quadrangle The database directory also includes the following ARC coverages, and files:ARC Coverages, which have been converted to uncompressed ARC/INFO export files: ARC/INFO Resultant Description of Coverage export file Coverage -------------- ------------------------------------------- alq_quad.e00 alq_quad/ Index map of quadrangles in Alameda County. alq_corr.e00 alq_corr/ Correlation table for the units in this map database. al_dr-sp.e00 al_dr-sp/ Drainage base map (from 1:100,000 scale originals). al_cu-sp.e00 al_cu-sp/ Cultural base map (from 1:100,000 scale originals). al_topo-sp.e00 al_topo-sp/ Topographic contours base map (from 1:100,000 scale originals). ASCII text files, including explanatory text, ARC/INFO key files, PostScript plot files, and a ARC Macro Language file for conversion of ARC export files into ARC coverages: alqgeo.ps A PostScript plot file of a report containing detailed unit descriptions and geological information, plus sources of data and references cited. alqgeo.txt A text-only file containing an unformatted version of alqgeo.ps alqdb.ps A PostScript plot file version of this report alqdb.txt This report alqkey.un Together, these key files produce a alqkey.ln plottable or displayable map explanation and key. import.aml ASCII text file in ARC Macro Language to convert ARC export files to ARC coverages in ARC/INFO. The following supporting directory is not included in the database package, but is produced in the process of reconverting the export files into ARC coverages: info/ INFO directory containing files supporting the databases. This directory is not included in the database release, but is created in the process of converting the export files into ARC coverages. POSTSCRIPT PLOTFILE PACKAGE A second digital data package is also available, which contains the PostScript images described below: alqmap.ps A PostScript plottable file containing an image of the geologic map and base maps of Alameda County at a scale of 1:100,000 (Sheet 1). alqexpl.ps A PostScript plottable file containing an image of map keys, correlation charts, and index maps for Alameda County (Sheet 2). alqgeo.ps A PostScript plot file of a report containing detailed unit descriptions and geological information, plus sources of data and references cited. Database Release Format The database was compiled in ARC/INFO, a commercial Geographic Information System (Environmental Systems Research Institute, Redlands, California), and is stored in uncompressed ARC export format (ARC/INFO version 7) in a compressed UNIX tar (tape archive) file. Tar and uncompress utilities are therefore required to extract the database from the tar file. These utilities are included in most UNIX systems, and can be obtained free of charge via the Internet from Internet Literacy's Common Internet File Formats Web page (http://www.matisse.net/files/formats.html). ARC/INFO export files (files with the .e00 extension) can be converted into ARC/INFO coverages (see below) and can be read by some other Geographic Information Systems, such as MapInfo via ArcLink. The digital compilation was done using version 7.0.3 of ARC/INFO with version 3.0 of the menu interface ALACARTE (Fitzgibbon and Wentworth, 1991, Fitzgibbon, 1991, Wentworth and Fitzgibbon, 1991). Obtaining the Digital Data The digital database package can be obtained in any of three ways: a. Sending a tape with request b. Anonymous ftp over the Internet c. From the Western Region Geologic Information Web Page. A 19.5 MB compressed tar file of the database and related files can be obtained by sending a tape with request and return address to: Alameda County Quaternary Geologic Database c/o Database Coordinator U.S. Geological Survey 345 Middlefield Road, M/S 975 Menlo Park, CA 94025 Do not omit any part of this address! 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 wrgis.wr.usgs.gov -make ftp connection with the USGS computer WRGIS Name: anonymous -use "anonymous" as your user name Password: your name -use your own user name as password cd pub/geologic -go down to the pub/geologic directory cd ca/of97-97 -go down to the open file directory type binary -change transfer type to binary get al_q1.tar.Z -copy the compressed tar file across Internet to your directory quit -close the ftp connection Web Pages The U.S. Geological Survey now supports a set of graphical pages on the World Wide Web. Digital publications (including this one) can be accessed via these pages. The location of the main web page for the entire U.S. Geological Survey is "http://www.usgs.gov". The web server for digital publications from the Western Region is "http://wrgis.wr.usgs.gov"; go to the California page to access this publication. In addition to providing easy access to the entire digital database, the Western Region web page also provides simple access to the PostScript plot files of the map and explanation sheet containing much of the data in the digital database for those interested in the Quaternary geology of Alameda County who do not use digital databases (see below). Extracting the digital database package from the Tar file If you obtained the database package 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 al_q1.tar.Z -makes a 87 MB uncompressed tar file al_q1.tar cd local_directory2 -go to the directory that will hold the directory alqgeo (if different from local_directory) tar xvfb {path to tar file}/al_q1.tar 20 -extract the alqgeo directory from the tar file. If you obtained the database package by anonymous ftp or from the web page: uncompress al_q1.tar.Z -makes a 87 MB uncompressed tar file al_q1.tar cd local_directory2 -go to the directory that will hold the directory alqgeo (if different from local_directory) tar xvfb {path to tar file}/al_q1.tar 20 -extract the alqgeo directory from the tar file. This process will create a directory "/alqgeo" that contains the ARC export files and supporting files as described above. PostScript Plot Files The database is in ARC export format, and therefore requires use of ARC/INFO or another compatible GIS system to access the information contained within it. For those interested in the Quaternary geology of the Alameda County who don't use an ARC/INFO compatible GIS system we have included a separate data package with three PostScript plot files. One contains a color plot of the geologic map database at 1:100,000 scale (Sheet 1, alqmap.ps). The second contains a color plot of the map keys and index map (Sheet 2, alqexpl.ps). 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. Small units have not been labeled with leaders and in some instances map features or annotation may overlap. Sample plots by the authors have proven to be quite legible and useful, however. In addition, a third PostScript file containing the geologic description and discussion is provided (alqgeo.ps). These plot files are available in any of the three ways described above, including the World Wide Web pages. However, the plot files are stored in compressed UNIX tar files requiring uncompress and tar utilities to access the files. These utilities are included in most UNIX systems, or can be obtained free of charge via the Internet from Internet Literacy's Common Internet File Formats Web page (http://www.matisse.net/files/formats.html). The PostScript image of Sheet 1 is 44 inches wide by 34 inches high, so it requires a large plotter to produce paper copies at the intended scale. The image of Sheet 2 is 15 by 20 inches. In addition to size constraints, some plotters, such as those with continual paper feed from a roll, are oriented with the long axis in the vertical direction, so the PostScript image will have to be rotated 90 degrees to fit entirely onto the page. Some plotters and plotter drivers, as well as many graphics software packages, can perform this rotation. The geologic description is on 8.5 by 11 inch pages. Obtaining Plots from an Outside Vendor For those interested in the Quaternary geology of Alameda County who do not use computers, we have made the PostScript plot files available to Capitol Color (phone: (800) 700-2656 or (408) 727-7560, FAX: (408) 727-0737). They will provide plots of the PostScript images of the geologic map sheet and explanation sheet for a fee (around $25 per sheet, with discounts for orders of multiple copies). We will also provide the PostScript plot files on digital tape for use by other vendors. A 12 MB compressed tar file (alqps.tar.Z, 40 MB when uncompressed) of the PostScript plot files can be obtained by sending a tape with request and return address to: Alameda County Quaternary Geology PostScript Plotfiles c/o Database Coordinator U.S. Geological Survey 345 Middlefield Road, M/S 975 Menlo Park, CA 94025 Do not omit any part of this address! 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. Make sure your vendor is capable of reading these tape types and PostScript plot files. Important information regarding tape file format is included in the section "PostScript Plot Files" above, so be certain to provide a copy of this document to your vendor. Extracting the PostScript plotfile package from the Tar file If you obtained the plotfile package 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 alqps.tar.Z -makes a 40 MB uncompressed tar file alqps.tar cd local_directory2 -go to the directory that will hold the directory alqplot (if different from local_directory) tar xvfb {path to tar file}/alqps.tar 20 -extract the alqplot directory from the tar file. If you obtained the database by anonymous ftp or from the web page: uncompress alqps.tar.Z -makes a 40 MB uncompressed tar file alqps.tar cd local_directory2 -go to the directory that will hold the directory alqplot (if different from local_directory) tar xvfb {path to tar file}/alqps.tar 20 -extract the alqplot directory from the tar file. This process will create a directory "/alqplot" that contains the PostScript plot files as described above. Converting ARC export files ARC export files are converted to ARC coverages using the ARC command IMPORT with the option COVER. In order to ease conversion and to maintain naming conventions, we have included an ASCII text file in ARC Macro Language that will convert all of the export files in the database into coverages and create the associated INFO directory. From the ARC command line type:Arc: &run import.amlARC export files can also be read by some other Geographic Information Systems. Please consult your GIS documentation to see if you can use ARC export files and the procedure to import them. Digital Compilation The geologic map information was digitized from stable originals of the geologic maps at 1:24,000 scale. The author manuscripts (pencil 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. Base Maps Base Map layers were prepared from scale-stable printing negatives of the U.S. Geological Survey San Francisco (1978 edition), Stockton (1989 edition), Palo Alto (1983 edition), and San Jose (1978 edition) 1:100,000 topographic maps, which have a 50 meter contour interval. Scanned and vectorized images were transformed from scanner coordinates to projection coordinates with digital tics placed by hand at map corners. The images were then trimmed interactively by hand using ALACARTE to conform to the area of the geologic coverages, and the four portions were combined. Small mismatches at the boundaries caused by slight differences in the original scans remain in the three base map coverages. These base map layers are digital images but no information other than location is attached to the lines. The base maps are provided for reference only. Faults and Landslides This map is intended to be of general use to engineers and land-use planners. However, its small scale 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, 1988). Similarly, the database cannot be used to identify or delineate landslides in the region. For a depiction of landslide distribution, see Nilsen and others (1979). Spatial Resolution Uses of this digital geologic map should not violate the spatial resolution of the data. Although the digital form of the data removes the constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. The fact that this database was edited at a scale of 1:24,000 means that higher resolution information is not present in the dataset. Plotting at scales larger than 1:24,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, where this database is used in combination with other data of higher resolution, the resolution of the combined output will be limited by the lower resolution of these data. Note that in contrast to the geologic coverages, the base map layers have a resolution of 1:100,000, so significant discrepancies with the geologic coverages are possible. The base map layers are provided for reference only.