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U.S. Geological Survey
Open-File Report 01-031
Online version 1.0

Geologic Map and Digital Database of the Conejo Well 7.5 minute Quadrangle, Riverside County, Southern California


Robert E. Powell

Digital preparation by

Pamela M. Cossette


The Southern California Areal Mapping Project (SCAMP) has undertaken regional geologic mapping investigations in Joshua Tree National Park, sponsored by Geologic Division's National Cooperative Geologic Mapping Program in cooperation with the National Park Service. These investigations span the east end of Pinto Basin and include parts of the Eagle, Cottonwood, Hexie, and Pinto Mountains. Quadrangles being mapped include the Conejo Well, Porcupine Wash, San Bernardino, and Pinto Mountain 7.5' quadrangles, Riverside County, California. Mapping of the Conejo Well quadrangle has been directed toward generating a multipurpose digital geologic map database. The quadrangle, situated in the eastern Transverse Ranges physiographic and structural province, encompasses part of the northern Eagle Mountains and part of the south flank of Pinto Basin. It is underlain by a basement terrane comprising Proterozoic metamorphic rocks, Mesozoic plutonic rocks, and Mesozoic and Mesozoic or Cenozoic hypabyssal dikes. The basement terrane is capped by a widespread Tertiary erosion surface preserved in remnants in the Eagle Mountains and buried beneath Cenozoic deposits in Pinto Basin. Locally, Miocene basalt overlies the erosion surface. A sequence of at least three Quaternary pediments is planed into the north piedmont of the Eagle Mountains, each in turn overlain by successively younger residual and alluvial deposits. The Tertiary erosion surface is deformed and broken by north-northwest-trending, high-angle, dip-slip faults in the Eagle Mountains and an east-west trending system of high-angle dip- and left-slip faults. In and adjacent to the Conejo Well quadrangle, faults of the both sets displace Miocene sedimentary rocks and basalt deposited on the Tertiary erosion surface and Pliocene and (or) Pleistocene deposits that accumulated on the oldest pediment. Faults of the NNW-trending system appear to be overlain by Pleistocene deposits that accumulated on younger pediments.

Learn more about the Conego Well dataset and its contents

Page-size image of oversize map of Conejo Well 7.5 minute quadrangle

This illustration is a .jpg (JPEG) non-navigable image of the USGS geologic-map plot of the Conejo Well quadrangle. A full-size, navigable map graphic can be viewed on-screen (cwell_map.pdf ) or can be plotted either from the PostScript file ( or the PDF file. Note: the full-size plot requires a large-format plotter, and is best reproduced at 600 (or greater) dpi.


File Name
File Type and Description
File Size

Readme tabulates contents of database and describes how to access them. Provided in ASCII text and Portable Document formats. Metadata file contains detailed technical descriptions of structure and content of digital data. Provided as parseable text in ASCII format, and as outline in Hypertext Markup Language format. Also available on the USGS Geologic Division Node of the National Geospatial Data Clearinghouse in these two and other formats. Explanatory pamphlet describes approach used in building database, and discusses purpose, content, and geologic framework of database.

ASCII readme file
25 KB
PDF readme file
111 KB
ASCII metadata file
74 KB
HTML metadata file
95 KB
ASCII version of explanatory pamphlet
51 KB
PDF version of explanatory pamphlet
138 KB
Database files are packaged as a tarred and gzipped file that bundles and compresses the following information: Database files: ASCII-formatted ARC/INFO interchange/export (.e00) file for each ARC/INFO coverage, symbolset, and dictionary. ASCII text files for readme, metadata, and explanatory pamphlet.
GZIP compressed 25.2-MB TAR bundle of all database files
5.4 MB
Gzip-compressed PostScript plot-file for generating paper copy of geologic map with marginal explanation. Portable Document Format file containing full-sized, navigable graphic image of geologic map with marginal explanation. Portable Document Format files containing stand-alone versions of Description of Map and Database Units (DMU) and Correlation of Map and Database Units (CMU) from map-margin explanation
Gzipped 244-MB PostScript plot file of map with marginal explanation
8.9 MB
PDF file containing geologic map with marginal explanation
5.0 MB
cwell_cmu.pdf PDF Correlation of Map and Database Units file
77 KB
cwell_dmu.pdf PDF Description of Map and Database Units file
70 KB


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

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For questions about the content of this report, contact Robert Powell

This report is only available on the web.

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URL of this page:
Maintained by: Michael Diggles
Created: March 8, 2001
Last modified: November 17, 2005 (mfd)