Geologic Map of the Swansea-Copper Penny Area, Central Buckskin Mountains, West-Central Arizona

The Buckskin-Rawhide detachment fault separates a variety of Proterozoic through Cenozoic rock types from underlying mylonitic crystalline rocks. In the Swansea-Copper Penny area of the central Buckskin Mountains, the detachment fault defines a gently ENE-plunging synform. Upper-plate rocks are preserved in the synform, whereas lower-plate myloni tic crystalline rocks compose the flanking, topographically higher, ENE-trending antifonns. Mylonitization of lower-plate crystalline rocks was the result of ductile shearing along the down-dip projection of the Buckskin-Rawhide detachment fault early in its movement history. TWo assemblages of rocks are preserved in the upper plate of the Buckskin-Rawhide detachment fault in the Swansea-Cbpper Penny area: (l) Pre-Tertiary rocks, especially Paleozoic and Mesozoic metasedimentary rocks, are complexly deformed and have undergone greenschist-facies metamorphism. Metamorphism, folding, cleavage development, and tectonic interleaving of diverse rock types is interpreted to be the result of Merozoic thrust faulting. (2) A litholcgically diverse stratigraphic sequence of Miocene and upper Oligocene(?) volcanic and sedimentary rocks generally dips moderately to steeply to the southwest and is folded into two north-south trending, south-plunging anticlines.Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu