Possible reactivation of the Vincent-Chocolate Mountains thrust in the Gavilan Hills area, southeasternmost California

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5129240

Oyarzabal, F R; Jacobson, C E ^[1]; Haxel, G B ^[2]

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1. Iowa State Univ., Ames, IA (United States)
2. Geological Survey, Flagstaff, AZ (United States)

The Late Cretaceous-early Tertiary Orocopia Schist (OS) of southeasternmost California consists of metamorphosed continental margin sedimentary and basaltic rocks, overlain by an upper plate of continental crust along the Vincent-Chocolate Mountains fault (VCMF). Previous analysis of late folds and shear band in OS and upper plate in the Gavilan Hills and adjacent ares indicated that the direction of transport of the upper plate was northeastward. This has been considered evidence of a SW dipping subduction zone, along which an outboard continental fragment was sutured to North America. Another view is that the VCMF was formed by underplating of the OS in an Andean continental margin, and that the NE-vergent late structures formed during uplift of the OS. The authors' continuing work in the Gavilan Hills confirm the NE sense of vergence but suggests a more complex structural history. The schist is characterized by refolded folds, shear bands, and two penetrative lineations. An older lineation that ranges from N10[degree]E to N30[degree]E is widespread in the area, but is more evident at low structural levels. A second lineation ranges from N40[degree]E to N70[degree]E and is strongly developed in rocks near the VCMF. The complex folding pattern, presence of mylonitic schist, relative thinness of upper-plate mylonite, and possible retrogressive character of the shear bands suggest that the VCMF in the Gavilan Hills area may have been reactivated after original thrusting. The VCMF in the Gavilan Hills is intermediate in character between the probable subduction thrust in the San Gabriel Mountains and the reactivated faults in the Orocopia Mountains and areas surrounding the Gavilan Hills.

• OSTI ID: 5129240
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CALIFORNIA
CENOZOIC ERA
CRETACEOUS PERIOD
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
MESOZOIC ERA
METAMORPHIC ROCKS
NORTH AMERICA
PLATE TECTONICS
ROCKS
SCHISTS
SUBDUCTION ZONES
TECTONICS
TERTIARY PERIOD
USA