DETRITAL GEO- AND THERMOCHRONOLOGIC DATA FROM MODERN RIVER SEDIMENTS OF THE CENTRAL AND NORTHEASTERN BROOKS RANGE, ALASKA, USA

Resolving the geologic history of the Brooks Range orogenic belt of northern Alaska is fundamental for understanding the tectonic evolution of the Arctic and the development of adjacent sedimentary basins. Yet, limited geo- and thermochronologic information is available due to difficulty of access to the remote ranges. To better characterize the compositional, geo-, and thermochronologic variation across the eastern extent of the orogenic belt, modern sand was sampled from over 25 rivers along the northern foothills of the Brooks Range, upstream of the Arctic Alaskan Coastal Plain. The contiguous river catchments span a >600 km length from the northcentral Brooks Range to the United States-Canada border. Complimentary river samples are currently being collected from the central and eastern areas of the southern flank of the Brooks Range, upstream of the Yukon-Koyukuk and Yukon Flats Basins, respectively.

We present detrital zircon (DZ) and detrital apatite (DA) U-Pb and fission track (FT) double dates from a preliminary subset of 12 samples along the central Brooks Range, Philip Smith Mountains, and Shublik-Sadlerochit Mountain regions. This ~300 km long transect crosses the west-to-east transition from the inactive to active segments of the uplifting mountain belt. River catchment areas coincide with juxtaposed Mesozoic Brookian allochthons and parautochthonous rocks in the northeastern salient of the orogenic belt. We compare the distributions of modern sediment FT cooling ages to published bedrock geo- and thermochronologic data within the catchment areas to test the existing understanding of protracted Cretaceous exhumation and subsequent Cenozoic reactivation of the orogen. Furthermore, we explore the relationship between crustal exhumation and the stratigraphic record in the eastern Colville Foreland Basin. Forthcoming data from the entire sample set is expected to resolve spatial extents of mid- and low-temperature cooling age components both along and across the orogenic belt. Furthermore, DZ and DA U-Pb age distributions can be analogously applied to ongoing provenance studies to determine contributions of Brooks Range sub-terrane sediment to the Mesozoic–Cenozoic strata of the Colville Foreland and Yukon-Koyukuk Basins to the north and south, respectively.