LATE CRETACEOUS TO EARLY CENOZOIC COOLING HISTORY ACROSS THE SEVIER HINTERLAND OF THE NORTH AMERICAN CORDILLERA

During the Late Cretaceous to early Cenozoic, a high-standing plateau covered much of the Sevier hinterland of the North American Cordillera. Although most authors agree that this plateau was in place by the Eocene, its spatial extents, and formation and destruction are much debated. Within the region, individual thermochronology studies indicate a complicated localized history, with two likely Pre-Miocene exhumation histories not attributed to Sevier deformation alone. The purpose of this study is to create a database of published and unpublished thermochronology data across the region to identify spatial and temporal patterns in cooling that may provide clues into the landscape evolution of this broad region. By analyzing patterns of cooling across the hinterland, phases of deformation and possible drivers may be discerned. Here we present a archive of published and unpublished low- to moderate-temperature thermochronology data from Nevada, southeastern California, western Utah, and northwestern Arizona that reveal the Late Cretaceous to Pliocene landscape evolution of this region. The database includes radiometric ages from seventy-nine thermochronology studies (e.g. K/Ar, 40Ar/39Ar, fission track, and (U-Th)/He), using a variety of minerals (e.g., apatite, zircon, titanite, feldspar, micas, and hornblende) with a wide range of closure temperatures (75-500 °C). In total, over 3000 ages have been assembled, with ages ranging from Cretaceous through Quaternary. Data is limited in certain regions (e.g., southeastern and central Nevada) as public access is restricted or studies have not been completed. The database has revealed three main phases of cooling: (1) Cretaceous cooling is linked to magmatic cooling, Sevier contraction, and syn-convergent extension; (2) Miocene to Pliocene cooling is linked to Basin and Range extension and dextral transtension; (3) Eocene cooling in the southern Sierra Nevada, the northern and western Great Basin, and Mojave may be related to the unconformity’s development, but its cause is not entirely clear. Further, a distinct lack of regional cooling in the middle Eocene to early Miocene suggests that tectonic and erosional exhumation was insignificant during this ~30 Myr period.