INTRODUCTION

Open-File Report 02-22 contains a digital geologic map database of the Corona North 7.5’ quadrangle,
Riverside and San Bernardino Counties, California that includes:

1. ARC/INFO (Environmental Systems Research Institute, http://www.esri.com) 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. This Readme; includes in Appendix I, data contained in crn_met.txt
b. The same graphic as plotted 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 formation name, 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. Marine deposits are in part overlain by local, mostly alluvial fan, deposits and are labeled Qomf. Grain size follows f.

Even though this is an Open-File Report and includes the standard USGS Open-File disclaimer, the report
closely adheres to the stratigraphic nomenclature of the U.S. Geological Survey. Descriptions of units can
be obtained by viewing or plotting the .pdf file (3b above) or plotting the postscript file (2 above).

Visit the GeoScience Node of the National Spatial Data Clearinghouse to find other geologic-map datasets in southern California or elsewhere in the Nation

Download a free copy of Adobe Acrobat Reader version 5.0

For questions about the content of this report, contact Douglas Morton