|Abstract:||This data set maps and describes the geology of the Lakeview 7.5‘ quadrangle, Riverside County,
California. The quadrangle encompasses part of the northern Peninsular Ranges Province.
Tonalitic granitic rocks of the Cretaceous Peninsular Range batholith dominate the bedrock
areas, and include rocks ranging in composition from monzogranite to gabbro. The Lakeview
Mountains are underlain chiefly by tonalite of the Lakeview pluton and related rocks. In the
northeastern corner of the quadrangle, Tertiary sedimentary rocks of the San Timoteo beds of
Frick (1921) and Mount Eden Formation of Fraser (1931) rest on Paleozoic schist, quartzite,
gneiss, and marble having a well developed east dipping foliation. The Tertiary formations are
much more extensively exposed in the San Timoteo Badlands to the northeast and southeast.
These Tertiary and Paleozoic units are separated from the Lakeview Mountains by the San Jacinto
Valley, which locally contains up to 3,000 m of Quaternary sediments. Two strands of the
seismically active San Jacinto Fault zone bound the Valley, the Claremont Fault on the
northeast side, and the Casa Loma Fault on the southwest side. Numerous cracks and fissures
related to both groundwater withdrawal and tectonic movements are developed in the Quaternary
sediments, especially in the northern part of the quadrangle.
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 data, (3) a coverage containing geologic unit
annotation and leaders, and (4) five additional INFO data tables (.rel) that contain detailed,
coded, geologic information such as texture, fabric, color, and mineralogy and (5) line and
point dictionaries, lines.rel and points.rel. 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, and (2) PDF files of this Readme (including the
metadata file as an appendix), the poly_attrib_code.txt (the polygon attribute coding), and the
graphic 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.