Constraints on low-angle faulting kinematics in the eastern Peninsular Ranges mylonite zone, and implications on southern California tectonics
Spatially associated with the eastern Peninsular Ranges mylonite zone (EPRMZ) are a complex series of regionally significant east-dipping low-angle faults whose kinematics are controversial. At issue is whether the faults represent west-directed thrusts, east-directed detachment faults, or a superposition of the latter on the former. The question has critical implications on late Mesozoic and Cenozoic tectonics of southern California. In the northern Santa Rosa Mountains south of Palm Springs, a relatively complete stack of five imbricate low-angle faults possess characteristics of well known thrust belts. Four of the faults, floored by the Palm Canyon and roofed by the Asbestos Mountain fault, comprise a west-directed duplex system, while the fifth may be a relic of an upper duplex. Relative offsets and the geometrically complex fold, basin, and domal structure of fault surfaces suggest that faults were initiated, folded synkinematically and subsequently locked promoting the initiation of new fault surfaces at upper levels. Total minimum offset is 20 km. Recent proposals correlating low-angle faults with metamorphic core complex/detachment terrains located to the east across the San Andreas fault are unfounded. Most geological relationships apparently conflicting with west-directed thrusting may be attributed to downdip eastward-reactivation of fault surfaces related, in part, to the creation of the topographically and structurally depressed Salton Trough flanking the belt to the east. The EPRMZ appears to represent an 8-10 km wide late Cretaceous post-intrusive deformation belt between two terrains: continental rocks to the east, and continent-fringing transitional crust to the west.
- Research Organization:
- Univ. of California, Berkeley (USA)
- OSTI ID:
- 6612409
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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