| Abstract: | This data set maps and describes the geology of the Telegraph 7.5‘ quadrangle, San Bernardino
County, California. Created using Environmental Systems Research Institute‘s ARC/INFO
software, the data base consists of the following items: (1) a double precision 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), Description of Map Units (DMU), and the graphic
produced by the PostScript plot file.
The Telegraph Peak quadrangle is located in the eastern San Gabriel Mountains part of the
Transverse Ranges Province of southern California. The generally east-striking structural
grain characteristic of the crystalline rocks of much of the San Gabriel Mountains is
apparent, but not well developed in the Telegraph Peak quadrangle. Here, the east-striking
structural grain is somewhat masked by the northwest-striking grain associated with the San
Andreas Fault zone.
Faults within the quadrangle include northwest-striking, right-lateral strike-slip faults of
the San Andreas system. The active San Andreas Fault, located in the northern part of the
quadrangle, dominates the younger structural elements. North of the San Andreas Fault is the
inactive Cajon Valley Fault that was probably an early strand of the San Andreas system. It
was active during deposition of the middle Miocene Cajon Valley Formation. South of the San
Andreas, the Punchbowl Fault, which is probably a long-abandoned segment of the San Andreas
Fault (Matti and Morton, 1993), has a sinuous trace apparently due to compression in the
eastern San Gabriel Mountains that post-dates displacement on the fault. The Punchbowl Fault
separates two major subdivisions of the Mesozoic Pelona Schist and is left-laterally offset by
a northeast-striking fault in the northwestern part of the quadrangle. Within the Punchbowl
Fault zone is a thin layer of highly deformed basement rock, which is clearly not part of the
Pelona Schist. To the southeast, in the Devore quadrangle, this included basement rock
attains a thickness of several hundred feet. Along strike to the northwest, Tertiary
sedimentary rocks are included within the fault zone. South of the Punchbowl Fault 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, and probably include the eastern part of the San Gabriel Fault.
The Vincent Thrust of late Cretaceous or early Tertiary age separates the Pelona Schist in the
lower plate from a heterogeneous basement complex in the upper plate. Immediately above the
Vincent Thrust is a variable thickness of mylonitic rock generally interpreted as a product
of displacement on the thrust. The upper plate includes two Paleozoic units, a schist and
gneiss sequence and a schist, quartzite, and marble metasedimentary sequence. Both sequences
are thrust over the Mesozoic Pelona Schist along the Vincent Thrust, and intruded by Tertiary
(late Oligocene) granitic rocks, granodiorite of Telegraph Peak, that also intrude the |
| Genre: | USGS Numbered Series |
| ProdID: | 31406 |
| Citation Author: | Morton, D. M.; Woodburne, M. O.; Foster, J. H.; Morton, Gregory; Cossette, P. M. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | 21 p., 1 over-size sheet, scale 1:24,000 (1 inch = 2,000 feet). |
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| Citation Series: | Open-File Report |
| Citation Series Code: | OFR |
| Citation Series Number: | 2001-293 |
| Citation Search Results Text: | Geologic map of the Telegraph Peak 7.5‘ quadrangle, San Bernardino County, California; 2001; OFR; 2001-293; Morton, D. M.; Woodburne, M. O.; Foster, J. H.; Morton, Gregory; Cossette, P. M. |
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| Citation Year: | 2001 |
| Type: | citation/reference |
| Text: | Geologic map of the Telegraph Peak 7.5‘ quadrangle, San Bernardino County, California; 2001; OFR; 2001-293; Morton, D. M.; Woodburne, M. O.; Foster, J. H.; Morton, Gregory; Cossette, P. M. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/usgs_thumb.jpg |
| URL (INDEX PAGE): | http://geopubs.wr.usgs.gov/open-file/of01-293 |
| Date Other: | Tue, 1 Jan 2002 00:00 -0600 |
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