USGS Geoscience Data Catalog
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Miller, David M., and Bedford, David R., 2000, Geologic Map Database of the El Mirage Lake Area, San Bernardino and Los Angeles Counties, California: U.S. Geological Survey Open-File Report 00-222, U.S. Geological Survey, Menlo Park, CA.
This is a Vector data set. It contains the following vector data types (SDTS terminology):
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.000016
Ordinates (y-coordinates) are specified to the nearest 0.000016
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.
|contact, approx. located||Boundary between two mapped units that has been observed but the location is not precise|
|contact, certain||Boundary between two mapped units that was observed, the location of which is well known and is described in Positional_Accuracy|
|contact, gradational||Boundary between two mapped units that is transitional over an area.|
|fault, approx. located||Structural boundary between mapped units or structural discontinuity within a mapped unit that has experienced relative offset. Locational accuracy is approximate, and described in Positional_Accuracy.|
|fault, approx. located, queried||Structural boundary between mapped units or structural discontinuity within a mapped unit that has experienced relative offset. The existence is inferred from structural, stratographic, of lineament relations. Locational accuracy is approximate, and described in Positional_Accuracy.|
|fault, certain||Structural boundary between mapped units or structural discontinuity within a mapped unit that has experienced relative offset. Locational accuracy is well located, and described in Positional_Accuracy.|
|fault, concealed||Structural boundary between mapped units or structural discontinuity within a mapped unit that has experienced relative offset. The fault is obscured by overlying map units, so it is not well-located as described in Positional_Accuracy, but is constrained to within about 120 meters on the ground.|
|fault, concealed, queried||Structural boundary between mapped units or structural discontinuity within a mapped unit that has experienced relative offset. The fault is obscured by overlying map units, so it is not well-located as described in Positional_Accuracy, but is constrained to within about 150 meters on the ground. Existence of the fault is inferred from lineaments or structural relations elsewhere.|
|map boundary, certain||Edge of mapped area, used to bound polygons at the edge of the map database. Locational confidence is described in Positional_Accuracy|
|scratch boundary||An arbitrary line usually with no geologic significance, but sometimes used to divide polygons with the same rock type, but divided by a separate attribute|
|Range of values|
U.S. Geological Survey
(650) 329-4923 (voice)
(650) 329-4936 (FAX)
This digital geologic map database, intended for use at 1:24,000- scale, describes and portrays the rock units and surficial deposits of the El Mirage Lake area. It was prepared as part of a water-resource assessments of the area, describing and interpreting surface geology that provides information to help understand distribution and extent of deeper groundwater-bearing units. Map data were assembled as a digital database using ARC/ INFO to enable wider applications than traditional paper-product geologic maps and to provide for efficient integration with other digital data bases prepared by the U.S. Geological Survey's Southern California Areal Mapping Project (<http://geology.wr.usgs.gov/wgmt/scamp>), other federal and state agencies, and the Mojave Water Agency.
Dibble, T.W., 1960, Preliminary geologic map of the Shadow Mountains quadrangle, Los Angeles and San Bernardino Counties, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-227.
Troxel, B.W. Gunderson, J.N., 1970, Geology of the Shadow Mountains and northern part of the Shadow Mountains SE quadrangles, western San Bernardino County, California: California Division of Mines and Geology Preliminary Report 12.
Ponti, D.J. Burke, D.B, 1980, Map showing Quaternary geology of the eastern Antelope Valley and vicinity, California: U.S. Geological Survey Open-File Report OFR80-1064.
Martin, M.W., 1992, Stratigraphic and structural evolution of the Shadow Mountains, western Mojave Desert, California: Implications for the tectonic development of the central and western Mojave Desert.
Person who carried out this activity:
Accuracy of line locations is carried in the database and displayed by different line symbols (solid vs. dashed lines) in the cartographic display. For the purpose of this database, solid lines represent contacts and faults located with an accuracy greater than 10 m and commonly greater than 5 m. Dashed lines represent two kinds of less certainly located features, each distinguished in the database: 1) contacts and faults located with an accuracy of 10 to 15 m, 2) contacts that represent gradational boundaries between adjacent units. Gradational contacts represent interleaving of sediments and smooth gradations in characteristics such as percentage of eolian sand. In general, these gradations take place over distances of 50 to 150 m. Lineaments and fold axes are lines whose positions do not affect location of polygons; they are located with an accuracy of 25 m.
This report is intended to completely describe the surficial and bedrock materials of the map area at a scale of 1:24000.
Polygon and chain-node topology present. Geologic lines attributed as a 'contact' do not separate geologic map units of the same type.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None
- Acknowledgement of the U.S. Geological Survey, Southern California Areal Mapping Project, Mojave Water Agency, and California Division of Mines and Geology would be appreciated in products derived from this dataset
(650) 329-2923 (voice)
USGS Open-File Report 00-222
This report 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.
This database, identified as "Geologic Map Database of the El Mirage Lake Area, San Bernardino and Los Angeles Counties, California," has been approved for release and publication by the Director of the USGS. 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 condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
|Data format:||ARC/INFO export files, explanatory materials, and printable maps for the digital database can be downloaded at the specified URL in format ArcInfo export (version 8.0)|
Database files, PostScript plotfiles, and related files can be obtained by sending a tape or CDR (Recordable CD-ROM) with request and return address to:
El Mirage Lake, California Database c/o Database Coordinator U.S. Geological Survey 345 Middlefield Road, M/S 975 Menlo Park, CA 94025Do not omit any part of this address!
The compressed tar file will be returned on the tape or CD-ROM. The acceptable tape type is: 2.3 or 5.0 GB, 8 mm Exabyte tape.