Thrust and strike-slip faulting are recognized in the Plomosa Mountains, southwestern Arizona. The distribution of rock types and the geometry of the thrust faults necessitate that the upper plate moved from east to west. The amount of displacement is not known, but is considered to be large. Apparent separations along the strike-slip faults are in a right-lateral sense and are greater than 19,000 ft. Rhyodacite flows, dated by K-Ar methods at 19 to 20 m.y., unconformably overlie the thrust faults and are cut by the strike-slip faults.

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