Geologic map of the Fawnskin 7.5' quadrangle, San Bernardino County, California

This data set maps and describes the geology of the Fawnskin 7.5' quadrangle, San Bernardino
County, California and contains original U.S. Geological Survey data generated by detailed
field observation and by interpretation of aerial photographs. The geologic map covers part
of the northern San Bernardino Mountains. Bedrock units in the San Bernardino Mountains are
dominated by large Cretaceous and Jurassic granitic bodies ranging in composition from
monzogranite to gabbro, and include lesser Triassic monzonite. These granitic rocks intrude
highly faulted and folded Late Proterozoic and Paleozoic formations representative of those
found in the southern Great Basin. Low-angle thrust faults, many of them complexly folded,
cut the Late Proterozoic and Paleozoic formations. A large, deformed cataclastic zone in
the western part of the quadrangle cuts pre-Late Cretaceous units, and is intruded by Late
Cretaceous plutons. Spanning the Pleistocene in age, large alluvial fans flank the north
side of the mountains, and are dominated by debris flow deposits. Young, south dipping
reverse faults, some with moderately to well eroded fault scarps, discontinuously flank the
northern edge of the mountains. Young and old high-angle faults are mapped within the range.
Created using Environmental Systems Research Institute's ARC/INFO software, the database
consists of the following items: (1) a map coverage containing faults, geologic contacts and
units, (2) a coverage showing structural point data, (3) a coverage containing linear
structural data, (4) a coverage showing geologic line ornamentation and (5) six additional
INFO data tables (.rel) that contain detailed, coded, geologic information such as texture,
fabric, color, and mineralogy,. These additional data are accessible to the user through
the utilization of ARC/INFO relate environments and provide the user access to as much or as
little of the encoded data as required. In addition, the data set includes the following
graphic and text products: (1) A PostScript graphic plot-file containing the geologic map,
topography, cultural data, a Correlation of Map Units (CMU) diagram, a Description of Map
Units (DMU), and a key for point and line symbols; (2) PDF files of this Readme (including
the metadata file as an appendix), Description of Map Units (DMU), and a screen graphic of
the plot produced by the PostScript plot file.
The geologic map database contains original U.S. Geological Survey data generated by
detailed field observation and by interpretation of aerial photographs. Within the
database, geologic contacts are represented as lines (arcs), geologic units as polygons, and
site-specific data as points. Polygon, arc, and point attribute tables (.pat, .aat, and
.pat, respectively) uniquely identify each geologic datum.
Version 1.1 of this digital release differs from Version 1.0 mainly by changes and additions
to conform to the more recently released digital geologic map of the Butler Peak quadrangle
(OF 00-145), which adjoins the Fawnskin quadrangle on the west. Along the western edge of
the quadrangle several polygons of Quaternary units are added and the names of several are
changed. Colors of some granitic units are changed to conform to colors assigned to the
same units in the Butler Peak quadrangle.