PERMIAN TECTONICS IN THE DIAMOND MOUNTAINS, EUREKA AND WHITE PINE COUNTIES, NEVADA

New stratigraphic and structural analyses of Permian rocks in the Diamond Mountains of east-central Nevada reveal significant tectonic activity—deformation, uplift, and erosion, followed by deposition of a conglomerate unit—within the Permian. Early workers recognized deformation of the Permian section in the Diamond Mountains but did not document the geometry or constrain the age of deformation. This study examined the Permian section in the central eastern Diamond Mountains, approximately 35 km north of Eureka, Nevada. Permian tectonism folded basinal facies of Upper Wolfcampian through Middle Leonardian age, including fine grained siliciclastics and carbonates. The deformation resulted in broad, open folds with subhorizontal axes oriented northwest-southeast. These strata were beveled by erosion. A Roadian-Capitanian conglomerate and chert litharenite unit, originating in a highland to the west, was deposited on these strata. These Permian units folded under a Permian unconformity document an event that postdates the classical definition of the Antler orogeny, predates that of the Sonoma orogeny, and is not accounted for in traditional models for Paleozoic tectonism. The age of the overlap conglomerate suggests correlation with the regional P4 unconformity documented in northern Nevada (Trexler et al, 2004). Post-Permian, probably Mesozoic, deformation overprints the study area and is distinguished from the Permian deformation based on style and orientation of the folding. This study, when considered with other documented evidence of Late Paleozoic deformation, uplift, erosion, and basin evolution, adds to the growing body of data that indicate active compressional tectonism along the late Paleozoic margin of western Laurentia.