Geologic Map of the Cucamonga Peak 7.5' quadrangle, San Bernardino County, California

Metadata Updated: November 12, 2020

This data set maps and describes the geology of the Cucamonga Peak 7.5' quadrangle, San Bernardino County, California. Created using Environmental Systems Research Institute's ARC/INFO software, the database consists of the following items: (1) a map coverage containing geologic contacts and units, (2) a coverage containing site-specific structural data, (3) a coverage containing geologic-unit label leaders and their associated attribute tables for geologic units (polygons), contacts (arcs), and site-specific data (points). 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), an index map, a regional geologic and structure map, and a key for point and line symbols; (2) PDF files of this Readme (including the metadata file as an appendix) and the graphic produced by the PostScript plot file. The Cucamonga Peak quadrangle includes part of the boundary between two major physiographic provinces of California, the Transverse Ranges Province to the north and the Peninsular Ranges Province to the south. The north part of the quadrangle is in the eastern San Gabriel Mountains, and the southern part includes an extensive Quaternary alluvial-fan complex flanking the upper Santa Ana River valley, the northernmost part of the Peninsular Ranges Province. Thrust faults of the active Cucamonga Fault zone along the the south margin of the San Gabriel Mountains are the rejuvenated eastern terminus of a major old fault zone that bounds the south side of the western and central Transverse Ranges (Morton and Matti, 1993). Rejuvenation of this old fault zone, including the Cucamonga Fault zone, is apparently in response to compression in the eastern San Gabriel Mountains resulting from initiation of right-lateral slip on the San Jacinto Fault zone in the Peninsular Ranges. Within the northern part of the quadrangle are several arcuate-in-plan faults that are part of an antiformal, schuppen-like fault complex of the eastern San Gabriel Mountains. Most of these arcuate faults are reactivated and deformed older faults that probably include the eastern part of the San Gabriel Fault. The structural grain within the San Gabriel Mountains, as defined by basement rocks, is generally east striking. Within the Cucamonga Peak quadrangle, these basement rocks include a Paleozoic schist and gneiss sequence which occurs as large, continuous and discontinuous bodies intruded by Cretaceous granitic rocks. Most of the granitic rocks are of tonalitic composition, and many are mylonitic. South of the granitic rocks is a comple assemblage of Proterozoic(?) metamorphic rocks, at least part of which is metasedimentary. This assemblage is intruded by Cretaceous tonalite on its north side, and by charnockitic rocks near the center of the mass. The charnockitic rocks are in contact with no other Cretaceous granitic rocks. Consequently, their relative position in the intrusive sequence is unknown. The Proterozoic(?) assemblage was metamorphosed to upper amphibolite and lower granulite grade, and subsequently to a lower metamorphic grade. It is also intensely deformed by mylonitization characterized by an east-striking, north-dipping foliation, and by a pronounced subhorizontal lineation that plunges shallowly east and west. The southern half of the quadrangle is dominated by extensive, symmetrical alluvial-fan complexes, particularly two emanating from Day and Deer Canyons. Other Quaternary units ranging from early Pleistocene to recent are mapped, and represent alluvial-fan, landslide, talus, and wash environments. The geologic map database contains original U.S. Geological Survey data generated by detailed field observation and by interpretation of aerial photographs. This digital Open-File map supercedes an older analog Open-File map of the quadrangle, and includes extensive new data on the Quaternary deposits, and revises some fault and bedrock distribution within the San Gabriel Mountains. The digital map was compiled on a base-stable cronoflex copy of the Cucamonga Peak 7.5' topographic base and then scribed. This scribe guide was used to make a 0.007 mil blackline clear-film, from which lines and point were hand digitized. Lines, points, and polygons were subsequently edited at the USGS using standard ARC/INFO commands. Digitizing and editing artifacts significant enough to display at a scale of 1:24,000 were corrected. 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.

Access & Use Information

License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Date February 5, 2016
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Reference Date(s) January 1, 2001 (publication)
Frequency Of Update asNeeded

Metadata Source

Harvested from DOI Open Data

Graphic Preview

Non-navigable .jpg image of the geologic map, topographic base, Correlation of Map Units, Description of Map Units and key to point and line symbols. 400x406 pixels, 32-bit RGB true color, 45k bytes.

Additional Metadata

Resource Type Dataset
Metadata Date February 5, 2016
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Reference Date(s) January 1, 2001 (publication)
Responsible Party U.S. Geological Survey, Western Region, Earth Surface Processes Team (Point of Contact)
Contact Email
Access Constraints Use Constraints: The Cucamonga Peak 7.5' geologic-map database should be used to evaluate and understand the geologic character of the Cucamonga Peak 7.5' quadrangle as a whole. The data should not be used for purposes of site-specific land-use planning or site-specific geologic evaluations. The database is sufficiently detailed to identify and characterize geologic materials and structures. However, it is not sufficiently detailed for site-specific determinations. Use of this digital geologic map database should not violate the spatial resolution of the data. Although the digital form of the data removes the constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. The fact that this database was compiled and edited at a scale of 1:24,000 means that higher resolution information may not have been uniformly retained in the dataset. Plotting at scales larger than 1:24,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, although higher resolution data is incorporated in parts of the map, the resolution of the combined output will be limited by the lower resolution data., Access Constraints: None
Bbox East Long -117.49990774
Bbox North Lat 34.24999995
Bbox South Lat 34.1249841
Bbox West Long -117.62509226
Coupled Resource
Frequency Of Update asNeeded
Graphic Preview Description Non-navigable .jpg image of the geologic map, topographic base, Correlation of Map Units, Description of Map Units and key to point and line symbols. 400x406 pixels, 32-bit RGB true color, 45k bytes.
Graphic Preview File
Graphic Preview Type JPEG
Licence The U.S. Geological Survey (USGS) provides these geographic data "as is." The USGS makes no guarantee or warranty concerning the accuracy of information contained in the geographic data. The USGS further makes no warranties, either expressed or implied as to any other matter whatsoever, including, without limitation, the condition of the product, or its fitness for any particular purpose. The burden for determining fitness for use lies entirely with the user. Although these data have been processed successfully on computers at the USGS, no warranty, expressed or implied, is made by the USGS regarding the use of these data on any other system, nor does the fact of distribution constitute or imply any such warranty. 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 the delivery, installation, operation, or support by USGS. This digital, geologic map database of the Cucamonga Peak 7.5' quadrangle, 1:24,000 map-scale, and any derivative maps thereof, is not meant to be used or displayed at any scale larger than 1:24,000 (e.g., 1:12,000).
Metadata Language
Metadata Type geospatial
Progress completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True
Temporal Extent Begin 1974-04-01
Temporal Extent End 1981-08-01

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