Reinterpretation of Lime Peak thrust as a low-angle normal fault: Implications for the tectonics of southeastern Arizona

Abstract

Normal separation of offset stratigraphic units across the Lime Peak fault, mapped by Cooper and Silver as a thrust in the Dragoon quadrangle of southern Arizona, indicates that the fault is actually a low-angle normal fault, reflecting crustal distension rather than crustal contraction. The fault has been identified by Drewes as one of the few exposed segments of the supposed Hidalgo thrust of inferred subregional extent. Recognition that the structure is a low-angle normal fault of probable mid-Tertiary age thus casts doubt on the concept that coherent subhorizontal thrust sheets of Laramide age actually exist in southern Arizona.