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.
The digital geologic map database for the Conejo Well quadrangle has been created as a general-purpose data set that is applicable to land-related investigations in the earth and biological sciences. Along with geologic map databases in preparation for adjoining quadrangles, the Conejo Well database has been generated to further our understanding of bedrock and surficial processes at work in the region and to document evidence for seismotectonic activity in the eastern Transverse Ranges. The database is designed to serve as a base layer suitable for ecosystem and mineral resource assessment and for building a hydrogeologic framework for Pinto Basin.
Within the geologic map database, map units are identified by standard geologic map criteria such as formation-name, age, and lithology. The authors have attempted to adhere to the stratigraphic nomenclature of the U.S. Geological Survey and the North American Stratigraphic Code, but the database has not received a formal editorial review of geologic names.
Special symbols are associated with some map units. Question marks have been added to the unit symbol (e.g., QTs?, Jmi?) and unit name where unit assignment based on interpretation of aerial photographs is uncertain. Question marks are plotted as part of the map unit symbol for those polygons to which they apply, but they are not shown in the CMU or DMU unless all polygons of a given unit are queried. To locate queried map-unit polygons in a search of database, the question mark must be included as part of the unit symbol. In some polygons, multiple units crop out in individual domains that are too small or too intricately intermingled to distinguish at 1:24,000, or for which relations are not well documented. For these polygons, unit symbols are combined using plus (+) signs (e.g., Qyaos + Qyas2) in the LABL and PLABL items.
Geologic map unit labels entered in database items LABL and PLABL contain substitute characters for conventional stratigraphic age symbols: Proterozoic appears as 'Pr' in LABL and as '<' in PLABL, Triassic appears as 'Tr' in LABL and as '^' in PLABL. The substitute characters in PLABL invoke their corresponding symbols from the GeoAge font group to generate map unit labels with conventional stratigraphic symbols.
Content. This database, identified as "Geologic map and digital database of the Conejo Well 7.5 minute quadrangle, Riverside County, California" has been approved for release and publication by the Director of the U.S. Geological Survey. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on the condition that neither the USGS nor the United States Government may be held responsible for any damages resulting from its authorized or unauthorized use. This database is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Faults. The Conejo Well database is sufficiently detailed to identify and characterize many actual and potential geologic hazards represented by faults, but it is not sufficiently detailed for site-specific determinations or evaluations of these features. Faults shown do not take the place of fault-rupture hazard zones designated by the California State Geologist (see, for example, Hart, 1988; Hart and Bryant, 1997).
Hart, E. W., 1988, Fault-rupture zones in California; Alquist-Priolo Special Studies Zones Act of 1972 with index to special studies zones maps (revised, 1988): California Division of Mines and Geology Special Publication 42.
Hart, E. W., and Bryant, W.A., 1997, Fault-rupture zones in California; Alquist-Priolo Special Studies Zones Act of 1972 with index to special studies zones maps (revised, 1997): California Division of Mines and Geology Special Publication 42.
This database was prepared in the GIS laboratory at the Spokane Field Office of the USGS in Spokane, Washington. The facility is maintained primarily by the Mineral Resource Surveys Program and supported in part by the National Geologic Mapping Program. We thank Paul C. Hyndman and Steven R. Munts in Spokane and Rachel Hauser Alvarez of the SCAMP GIS laboratory at the University of California, Riverside for their assistance in solving problems encountered during digital preparation of the data set.
Technical review by Fred K. Miller has led to significant improvements in the database and in the map plot file. David R. Bedford has examined the digital database file for internal logical consistency, has reviewed the metadata file, and has tested the viability of digital products.
The areal extent of the map is represented digitally by an appropriately projected (Polyconic projection), mathematically generated box. Consequently, polygons intersecting the lines that comprise the map boundary are closed by that boundary. Polygons internal to the map boundary are completely enclosed by line segments which are themselves a set of sequentially numbered coordinate pairs. Point data are represented by coordinate pairs.
Linear features in the Conejo Well geologic map database are represented as solid, dashed, and dotted lines. Using the DOQQ base, points and linear features represented by solid lines are located to within 10 m or less of their position on the ground. Linear features represented as dashed lines may or may not be located to within 10 m of their position on the ground. Linear features represented by dotted lines are concealed beneath overlying mapped units. The accuracy of the various lines is identified in the digital database as well as on the geologic-map plot.
Contacts between lithologic domains that make up surficial deposits as mapped on the DOQQs typically are readily located to within 10 m, but to make domains that can be resolved at 1:24,000 contacts are often drawn by approximating the dominant unit on a percentage basis. Interspersal of well- and approximately located contacts is common among the many hundreds of contact segments present in the Conejo Well quadrangle. Given that many quadrangles are being mapped in a relatively short time interval, it was deemed too time-consuming to distinguish well-located and approximately located contacts between surficial deposits; therefore, all surficial contacts are represented as approximately located and shown with a dashed line symbol.
Powell, R.E., 1981, Geology of the crystalline basement complex, eastern Transverse Ranges, southern California: Constraints on regional tectonic interpretation [Ph.D. thesis]: Pasadena, California Institute of Technology, 441 p.
USGS, 1973, True color aerial photographs labeled GS-SE. Photographs taken along northwest-southeast oriented flight lines covering the eastern Transverse Ranges south of the Pinto Mountain fault. Lines flown at moderate to low sun-angle in October 1973; scale 1:36,000.
Powell, R. E., Whittington, C. L., Grauch, V. J. S., and McColly, R. A., 1984, Mineral resource potential of the Eagle Mountains Wilderness Study Area (CDCA-334), Riverside County, California: U.S. Geological Survey Open-File Report 84-631, 25 p., scale 1:62,500.
Powell, R.E., 1993, Balanced palinspastic reconstruction of pre-late Cenozoic paleogeology, southern California: Geologic and kinematic constraints on evolution of the San Andreas fault system, in Powell, R.E., Weldon, R.J., II, and Matti, J.C., eds., The San Andreas fault system: Displacement, palinspastic reconstruction, and geologic evolution: Geological Society of America Memoir 178, p. 1-106.
USGS, 1998, True color aerial photographs labeled J.T.N.P. Photographs taken along east-west oriented flight lines covering part of Joshua Tree National Park in Pinto Basin and parts of the Coxcomb, Pinto, Eagle, Cottonwood, Hexie, and Little San Bernardino Mountains. Lines flown at high sun-angle in May 1998; scale 1:24,000.
(1) The coverage cwell_geo includes the following feature attribute tables: (a) a polygon attribute table (cwell_geo.pat) that describes the geospatial distribution of rock units represented in the Postscript (.ps) and Portable Document Format (.pdf) plotfiles of the geologic maps; (b)region subclass attribute tables (cwell_geo.patmetunit, cwell_geo.patpedunit, cwell_geo.patplutunit, cwell_geo.patsedunit, cwell_geo.patveinunit, cwell_geo.patvolcunit, cwell_geo.hydaltunit) that describe all geologic units contained in the database; and (c) an arc attribute table (cwell_geo.aat) that describes the contacts and faults that bound rock-unit polygons. For display purposes in the .ps and .pdf geologic maps, the geology coverage includes one annotation subclass (anno.geo) which contains unit labels derived from the coded item PLABL.
(2) The coverage cwell_dk includes an arc attribute table (cwell_dk.aat) that describes hypabyssal dikes. Dikes are planar intrusive features that intersect the Earth's surface as linear features; they are represented as lines where their surface widths are too narrow to be represented as polygons at a scale of 1:24,000.
(3) The coverage cwell_str includes a point attribute table (cwell_str.pat) that describes geologic structural point data, including the types and orientation of bedding, foliation, and lineation. An annotation subclass (anno.value) displays the dip or plunge values associated with point data.
(4) The coverage cwell_orn includes a point attribute table (cwell_orn.pat) that describes structural line ornamentation. An annotation subclass (anno.line) displays the sense of movement on a fault.
(5) The coverage cwell_ldr includes an arc attribute table (cwell_ldr.pat) that describes annotation leaders. Unit symbols that are placed outside the perimeter of a particular polygon identify that polygon with annotation leaders.
In no event shall the USGS have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of use of or reliance on the geographic data or arising out of delivery, installation, operation, or support by USGS.
This digital, geologic map database of the Conejo Well 7.5 minute quadrangle, and any derivative maps thereof, is not meant to be used or displayed at any map scale larger than 1:12,000 on the DOQQ base or 1:24,000 on the topographic base.