Abstract

The trough extending north from Tahoe, past Donner Lake, California, is bounded on the west by a zone of uplift in which the base of Tertiary andesitic deposits on the eroded surface of the basement complex is 800 to 2400 feet higher than in adjacent parts of the depression. This paper deals with a part of the uplifted zone extending from Donner Pass 10miles S. 15°E. to Squaw Peak. Here are two areas of maximum uplift caused by folding and faulting of the east limbs of the folds. The faults with greatest throw dip east at high angles, but notable movements occurred on west-dipping and vertical faults, and, on some faults, the dip changes from east to west in passing along the strike. Deformation began with folding of the entire zone. This was then accentuated, with accompanying faulting, to produce the two structural highs. Finally there was major faulting along the east edge of the zone. Deformation is believed to be post-Miocene and preglacial. The evidence from this region gives no support to the idea that the Tertiary deposits of the Sierra Nevada were deformed merely by westward tilting of a rigid block.

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