Abstract

Late Cenozoic tectonic reconstructions of southern California (United States) have been hindered for decades by disagreement over the total displacement on the southern San Andreas fault; disparate estimates of dextral offset range from 160 km to 240 km. Prior estimates were based on purely translational models that neglect the effects of transrotational strain on the orientation and distribution of key geologic markers. We present a new reconstruction that integrates published lithologic, structural, and paleocurrent data with the effects of clockwise rotation in the eastern Transverse Ranges (ETR). This model yields 200 ± 14 km of cumulative offset on the southern San Andreas fault system in the Salton Trough. The disparity between our estimate and a lower estimate of 160 km for the Mojave segment can be explained by a combination of transtensional elongation along the southwest boundary of the ETR, transfer of strain to the eastern California shear zone, and diffuse crustal shortening in the Big Bend region. This reconstruction reconciles previously incompatible and long-debated models, and places an important new constraint on the tectonic evolution of the Pacific–North America plate boundary in southern California.

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