Cooling History of the Sevier Hinterland Plateau During the Late Cretaceous to Eocene in East-central and Southern Nevada

During the Late Cretaceous to Paleogene, an orogenic plateau, like the modern Andean Puna-Altiplano, lay in the hinterland of the Sevier retroarc system. The plateau is well documented, however, its spatial extent and the dynamic processes involved in its construction and destruction are not well established. Two primary models, gravitational collapse and slab rollback, are suggested for the demise of the plateau. We test these models by obtaining new bedrock thermochronology data from the southern segment of this system in east-central and southern Nevada. We collected nine samples from seven sites across this large study corridor. Samples were collected from Cambrian to Ordovician quartzites (e.g. Stirling, Prospect Mountain, and Eureka) that presently reside in the footwalls of Miocene to Quaternary Basin and Range normal faults. The samples can provide critical constraints on exhumation associated with the central Nevada thrust belt, a belt of contractional deformation in the hinterland, and/or synconvergent extensional structures that may have been involved in the initial demise of the hinterland plateau. Sample processing and apatite and zircon (U-Th)/He analyses are currently underway. The bedrock thermochronology data will be combined with retrodeformable cross-sections and forward and inverse temperature history modeling to determine the timing, magnitude, and spatial pattern of cooling and to establish which of these models may be most relevant for the region. Exhumation ages linked to thrusts and/or synconvergent extensional structures in the region should be close in timing to published constraints on contraction in the central Nevada thrust belt and would support the gravitational collapse model. Exhumation ages younger than published Eocene ages to the north and that young southward through the study corridor would be best explained by mantle dynamic processes associated with slab rollback. Finally, if exhumation in the study corridor is broadly like documented Eocene ages to the north and west, then other hinterland-scale dynamic processes that have not yet been fully explored (e.g., denudation linked to climate change), may have been involved.