PRELIMINARY DETRITAL ZIRCON AND ΕHF DATA FROM THE UPPER TRIASSIC (NORIAN) AULD LANG SYNE BASIN OF NEVADA (USA), WITH IMPLICATIONS FOR ARC EVOLUTION AND CONTINENTAL PALEOGEOGRAPHY

Upper Triassic strata of the Auld Lang Syne (ALS) basin in northwest Nevada, USA, record the Late Triassic evolution of a marine backarc basin located on the western margin of the North American continent. The original basin geometry was overprinted by Jurassic shortening during development of the Luning-Fencemaker fold-thrust belt (i.e., folding, reverse faulting, and cleavage development), middle to Late Cretaceous pluton emplacement, and Neogene volcanism and Basin and Range extension. However, Norian (ca. 227-208.5 Ma) siliciclastic strata that dominate the basin fill are well-preserved in many areas and collectively represent a significant marine depocenter: shallow marine deposits in the eastern basin have an original stratigraphic thickness of up to 1 km and modern areal extent of ~6,000 km², whereas deeper marine deposits in the western basin have an original thickness of ≥ 5 km and areal extent of ~20,000 km². The ALS basin strata have long been inferred to represent the terminal sink for a transcontinental (e.g., > 1500 km-long) river network with headwaters in the ancestral Ouachita orogen of Texas and Oklahoma, recorded by fluvial deposits of the Chinle and Dockum Groups of the Colorado Plateau and continental interior. We test these inferred source-to-sink relationships using new detrital zircon (DZ) data for Norian sandstones of the ALS basin. Composite DZ age distributions for new marine and published terrestrial samples are statistically indistinguishable at 95% confidence, both characterized by abundant Triassic, Paleozoic, and Mesoproterozoic to Paleoproterozoic dates that support a sediment source in the ancestral Ouachita orogen of Texas and Oklahoma, and thus, connectivity between the Chinle-Dockum paleoriver system and the ALS basin. In addition, the new data highlight variations within Triassic and Paleozoic DZ dates and εHf values that can be linked, respectively, to nuances in Triassic arc activity and discrete source regions in the Ancestral Rocky Mountains province. Ultimately, our new DZ data provide new information for early Mesozoic Cordilleran arc and basin histories that are otherwise obscured by post-Triassic deformation and magmatism.