Microstructural evidence for northeastward movement on the Chocolate Mountains fault zone, southeastern California

Journal Article · Wed Jan 10 04:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB01p00529· OSTI ID:5010301

Simpson, C ^[1]

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1. Johns Hopkins Univ., Baltimore, MD (United States)

Microstructural analysis of rocks from the Chocolate Mountains fault zone, Gavilan Hills area, southeastern California, show unequivocal evidence for northeast directed transport of the upper plate gneisses over lower plate Orocopia schists. Samples were taken from transects through the fault zone. Prefaulting fabrics in upper plate gneisses show a strong component of northeast directed rotational deformation under lower amphibolite facies conditions. In contrast, prefaulting lower plate Orocopia schists show strongly coaxial fabrics (minimum stretch value of 2.2) formed at greenschist grade. Mylonitic fabrics associated with the Chocolate Mountains fault are predominantly northeast directed shear bands that are unidirectional (northeastward) in the gneisses but bi-directional in the schists, suggesting a significant component of nonrotational deformation occurred in the Orocopia schists during and after emplacement of the upper plate. The kinematic findings are in agreement with Dillon et al. (1989), who found that the vergence of asymmetrical folds within the fault zone indicates overthrusting to the northeast, toward the craton, in this region. The available evidence favors a single protracted northeastward movement on the Chocolate Mountains fault zone with temperatures waning as deformation proceeded.

• OSTI ID: 5010301
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B1; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CALIFORNIA
CENOZOIC ERA
CRETACEOUS PERIOD
CRYSTAL STRUCTURE
DEFORMATION
DEVELOPED COUNTRIES
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
GNEISSES
MESOZOIC ERA
METAMORPHIC ROCKS
MICROSTRUCTURE
MOUNTAINS
NORTH AMERICA
ORIENTATION
PLATE TECTONICS
RESERVOIR ROCK
RESERVOIR TEMPERATURE
ROCKS
SAMPLING
SCHISTS
TECTONICS
TERTIARY PERIOD
USA