A NEW STRUCTURAL MODEL FROM THE SCHELL CREEK RANGE, NEVADA AND IMPLICATIONS FOR CRUSTAL THICKENING OF THE NEVADAPLANO

The mechanism of crustal thickening of the Nevadaplano has been a topic of considerable controversy in recent years. Relative to other orogenic plateaux like the Altiplano and Tibetan Plateau, the Nevadaplano is unique because it has been extended and deeper crustal levels have been exhumed. This allows for investigation across structural levels to gain insight into the thickening mechanism. 44 samples were collected from across the Schell Creek Range, Nevada and analyzed for peak temperature using Raman Spectroscopy of Carbonaceous Material (RSCM). Peak temperatures from 150-600°C were measured. Evaluating the temperature distribution across the range, and in particular across faults that separate rocks of significant age difference, led us to identify a previously unrecognized exposed thrust fault based on the temperature signature across the fault and another thrust fault that has been excised by or reactivated as a low-angle normal fault. We put forth a new model that includes thrust stacking of three structural slices. This model is consistent with the geologic relationships in the range, and with other studies in preparation that show evidence for low paleogeothermal gradients across the Great Basin at the time of maximum crustal thickness. We therefore suggest that stratal duplication and thrust stacking played a significant role in crustal thickening of the Nevadaplano orogenic plateau.