Abstract

Tertiary to Holocene(?) strike-slip and oblique-slip faults with minor displacements cut metasedimentary rocks of Snow Lake pendant and surrounding Jurassic to Cretaceous plutonic rocks in the Tower Peak quadrangle. These faults occur in a part of the Sierra Nevada where little Cenozoic deformation has previously been documented. Two sets of faults are present, one set striking northeast and the other striking east-northeast. Pre-Tertiary markers have separations across these faults ranging from 10 to 335 m. Some dextral displacement on both sets of faults postdates an 8.8 Ma hornblende andesite dike. The faults also show evidence of minor Holocene(?) displacements.

Displacement histories of these faults are complicated. Geometric relations of markers of different ages indicate that multiple episodes of displacement, including slip reversals, have occurred, and that displacements were not synchronous on all faults. Displacement on the faults was mainly strike slip, although field relations indicate some oblique displacement. The faults may have originated as joint and fracture sets that formed shortly after emplacement of plutonic rocks of the Sierra Nevada batholith (80-90 Ma). Reactivation of the faults then probably occurred during Cenozoic uplift and erosion of the Sierra Nevada, which was probably related to the complex interaction of oblique-convergent to transform margin tectonics and Basin and Range extension.

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