Abstract

Data on the patterns of growth of young, folded mountains are needed to complement inferences about orogenic histories derived from study of ancient deformed rocks. Crustal movements in the central Coast Ranges during the last 2 or 3 million years are determined by Pliocene-Pleistocene stratiggraphy, structures, and physiography. Although the magnitudes of movements are rather uncertain, the geometry is qualitatively well established by strata that dip off the flanks of the ranges. Boundaries between rising and subsiding areas are independent of the course of the San Andreas fault; furthermore, the geometric relationship of these major crustal blocks to the San Andreas fault is not that of a system of “wrench-fault tectonics.” Vertical movements of major blocks are probably mechanically independent of strike-slip movements on major faults; they appear to be primary, rather than secondary, results of lateral contraction. Comparison with other places and times suggests the possibility that the vertical movements may be related to intrusion of magma at depth.

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