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Rejuvenation of this old fault zone, including the Cucamonga Fault zone,is apparently in response to compression in the eastern San Gabriel Mountains resultingfrom initiation of right-lateral slip on the San Jacinto Fault zone in the PeninsularRanges.The structural grain within the San Gabriel Mountains, as defined by basementrocks, is generally east striking. Thrust faults of the Cucamonga Fault zone along the south margin of theSan Gabriel Mountains, represent the rejuvinated eastern end of a major old fault zonethat bounds the south side of the western and central Transverse Ranges (Morton andMatti, 1993). As a result, the interrelation between it, theGlen Helen Fault, and the probable easternmost part of the San Gabriel Fault isintrepretive. South of the Cucamonga and SanAndreas Fault zones, the extensive alluviated area in the south half of the quadranglelies within the upper Santa Ana River Valley, and represents the northernmost part ofthe Peninsular Ranges Province.There are numerous active faults within the quadrangle, including right-lateralstrike-slip faults of the San Andreas Fault system, which dominate the youngerstructural elements, and separate the San Gabriel from the San Bernardino Mountains.The active San Jacinto Fault zone projects toward the quadrangle from the southeast, butits location is poorly constrained not only within the quadrangle, but for at leastseveral kilometers to the southeast. The north half of the quadrangle includes the eastern SanGabriel Mountains and a small part of the western San Bernardino Mountains, both withinthe east-central part of the Transverse Ranges Province.

In addition, the dataset includes the following graphic and text products: (1) A PostScript graphicplot-file containing the geologic map, topography, cultural data, a Correlation of MapUnits (CMU) diagram, a Description of Map Units (DMU), an index map, a regionalgeologic and structure map, and a key for point and line symbols (2) PDF files of thisReadme (including the metadata file as an appendix), Description of Map Units (DMU),and the graphic produced by the PostScript plot file.The Devore quadrangle straddles part of the boundary between two major physiographicprovinces of California, the Transverse Ranges Province to the north and the PeninsularRanges Province to the south. Created using Environmental Systems Research Institute'sARC/INFO software, the data base consists of the following items: (1) a map coveragecontaining geologic contacts and units, (2) attribute tables for geologic units(polygons), contacts (arcs), and site-specific data (points). This data set maps and describes the geology of the Devore 7.5' quadrangle, SanBernardino County, California.