Detrital Zircon U–Pb Geochronology and Hf Isotope Geochemistry of Sandstones in a “Mudpile” (Auld Lang Syne Basin, Nevada, USA): Insights into the Late Triassic Paleogeography of Laurentia

The Upper Triassic Chinle Formation and equivalents, exposed across the Western Interior of North America, have long been interpreted to record a transcontinental river system that connected the Ouachita orogen of Texas–Oklahoma to the Auld Lang Syne basin (ALSB) of northwestern Nevada. Fluvial strata are well-characterized by existing detrital zircon (DZ) data, but the provenance of the ALSB has remained poorly constrained by comparison. We present new DZ U–Pb and Hf isotopic data that characterize the provenance of sandstones in the mudstone-dominated ALSB. Mixture modeling of potential sediment source regions in the Alleghany–Ouachita–Marathon belt supports a primary source area in the Marathon sector, generally validating prior inferences, but also highlights sediment contributions from eastern sectors of the orogen. These results indicate that southern Laurentia hosted a Mississippi River-scale watershed during the Late Triassic. Further, a comparison of new Hf isotopic data with those characterizing Late Triassic peri-Laurentian arc complexes demonstrates that multiple volcanic arcs may have simultaneously contributed Late Triassic volcanogenic zircons to Laurentia and the ALSB, but the west Pangean arc of Mexico and northwestern South America stands out as a source for highly evolved Permian to Late Triassic DZ grains in the ALSB. In summary, our use of paired DZ U–Pb geochronology and Hf isotope geochemistry data to characterize the terminal deposits of a Mississippi River-scale drainage network provides paleogeographic insight for southern Laurentia and its active margins during the Late Triassic.