CONTINENTAL-SCALE GLACIATION, SEDIMENT RECYCLING, AND UNROOFING SIGNATURES IN DETRITAL SEDIMENTS OF THE LATE PLEISTOCENE MISSISSIPPI DEEP-SEA FAN

Detrital mineral geochronology and thermochronology (i.e. “double dating”) of deep-sea sediments can provide insights into the tectonic and climatic evolution of regions within the continental catchment from which it is sourced. The late Pleistocene Mississippi River to deep-sea fan of North America was one of Earth’s largest sediment-routing networks during the most recent glacio-eustatic cycle. To understand late Pleistocene sediment production and dispersal of the ancestral Mississippi system, we sampled Deep Sea Drilling Project (Leg 96) cores and U.S. Geological Survey piston cores of late Wisconsin deep-sea fan deposits in the Gulf of Mexico for detrital zircon U-Pb and (U-Th)/He double-dating analyses. Our results suggest the late Pleistocene glacial Mississippi system forced a larger transfer of sediment from Cordilleran magmatic provinces and the Canadian Shield compared to the modern drainage. This indicates a more expansive and/or erosive ancestral Mississippi catchment driven by high-discharge meltwater and glacial-lake outbursts during ice retreat. Late Archean zircon with ~2 Ga cooling ages are interpreted as having been slowly exhumed from the continental shield with long-duration, continental sediment storage and insignificant burial. Additionally, the presence of zircon with Western U.S.-affinity U-Pb ages and Appalachian (U-Th)/He ages records pre-Mesozoic transport of western U.S. sediments into eastern U.S. basins, confirming the interpretation that western U.S. U-Pb zircon provenance indicators can be sourced from the Appalachian Mountains. Gulf of Mexico sediments also contain a distinct population of ~83 Ma (U-Th)/He ages which correlate with earliest Laramide uplift, suggesting that the earliest phases of unroofing and deformation may be preferentially preserved in the rock record.