Geologic map and digital database of the Conejo Well 7.5 minute quadrangle, Riverside County, California

This data set maps and describes the geology of the Conejo
Well 7.5 minute quadrangle, Riverside County, southern
California. The quadrangle, situated in Joshua Tree
National Park 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
northwest-trending set 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 this system appear to be
overlain by Pleistocene deposits that accumulated on
younger pediments. East-west trending faults are younger
than and perhaps in part coeval with faults of the
northwest-trending set.
The Conejo Well database was created using ARCVIEW and ARC/INFO,
which are geographical information system (GIS) software
products of Envronmental Systems Research Institute (ESRI). The
database consists of the following items: (1) a map coverage
showing faults and geologic contacts and units, (2) a separate
coverage showing dikes, (3) a coverage showing structural data,
(4) a point coverage containing line ornamentation, and (5) a
scanned topographic base at a scale of 1:24,000. The coverages
include attribute tables for geologic units (polygons and
regions), contacts (arcs), and site-specific data (points). The
database, accompanied by a pamphlet file and this metadata file,
also includes the following graphic and text products: (1) A
portable document file (.pdf) containing a navigable graphic of
the geologic map on a 1:24,000 topographic base. The map is
accompanied by a marginal explanation consisting of a
Description of Map and Database Units (DMU), a Correlation of
Map and Database Units (CMU), and a key to point-and
line-symbols. (2) Separate .pdf files of the DMU and CMU,
individually. (3) A PostScript graphic-file containing the
geologic map on a 1:24,000 topographic base accompanied by the
marginal explanation. (4) A pamphlet that describes the
database and how to access it. Within the database, geologic
contacts , faults, and dikes are represented as lines (arcs),
geologic units as polygons and regions, and site-specific data
as points. Polygon, arc, and point attribute tables (.pat, .aat,
and .pat, respectively) uniquely identify each geologic datum
and link it to other tables (.rel) that provide more detailed
geologic information.