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Open-File report 03-270

Prepared in cooperation with the California Geological Survey

Preliminary Geologic Map of the Perris 7.5’ Quadrangle, Riverside County, California

By Douglas M. Morton

Thumbnail of and link to report PDF (3 MB)Introduction

Open-File Report 03-270 contains a digital geologic map database of the Perris 7.5’ quadrangle, Riverside County, California that includes: 1. ARC/INFO (Environmental Systems Research Institute, version 7.2.1 coverages of the various elements of the geologic map.

2. A Postscript file to plot the geologic map on a topographic base, and containing a Correlation of Map Units diagram (CMU), a Description of Map Units (DMU), and an index map.

3. Portable Document Format (.pdf) files of:

a. A Readme file

b. The same graphic as described in 2 above. Test plots have not produced precise 1:24,000- scale map sheets. Adobe Acrobat page size setting influences map scale.

The Correlation of Map Units and Description of Map Units is in the editorial format of USGS Geologic Investigations Series (I-series) maps but has not been edited to comply with I-map standards. Within the geologic map data package, map units are identified by standard geologic map criteria such as formationname, age, and lithology. Where known, grain size is indicated on the map by a subscripted letter or letters following the unit symbols as follows: lg, large boulders; b, boulder; g, gravel; a, arenaceous; s, silt; c, clay; e.g. Qyfa is a predominantly young alluvial fan deposit that is arenaceous. Multiple letters are used for more specific identification or for mixed units, e.g., Qfysa is a silty sand. In some cases, mixed units are indicated by a compound symbol; e.g., Qyf2sc.

First posted July 16, 2003

Readme's and Metadata


Files for viewing and plotting

  • Map PDF (3 MB)
    PDF file of map sheet that can be used for viewing map in a browser, as well as for plotting
  • Map PS.GZ (1.9 MB)
    Compressed (gzip) PostScript file used for plotting a paper copy of the map

The National Geologic Map Database has additional data about this publication

For additional information, contact:
Geology, Minerals, Energy, and Geophysics Science Center
U.S. Geological Survey
345 Middlefield Road, MS 901
Menlo Park, CA 94025-3591

Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Morton, Douglas M., 2003, Preliminary Geologic Map of the Perris 7.5’ Quadrangle, Riverside County, California: U.S. Geological Survey Open-File Report 03-270,

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