LATE MIOCENE TO PLEISTOCENE LITHOSTRATIGRAPHIC CHANGES FROM IODP SITE U1522 ON THE ROSS SEA CONTINENTAL SHELF

In 2018 the International Ocean Discovery Program (IODP) Expedition 374 recovered a Upper Miocene to recent geological record from the Glomar Challenger Basin on the Ross Sea continental shelf Antarctica at Site U1522. One of the main objectives of drilling was to determine whether ice sheet overriding events observed at the Antarctic Geological Drilling Project (ANDRILL) Site AND-1B advanced to the shelf edge, thus helping to constrain the contributions of Antarctica’s ice sheets to Pliocene sea level lowstands. Furthermore, this site provides an opportunity to assess paleoceanographic conditions at the outermost Ross Sea, where downhole logging may provide insights into the orbital controls on marine-based ice sheet extent. We present a new record of bulk geochemical mineral composition (~200 samples), for comparisons with high-resolution XRF core scanning data, shipboard physical property data, clast count data, ICP-MS geochemical measurements, and downhole logging data in order to contribute to studies focused on paleo ice-stream behavior. Initial statistical analyses reveal geochemical facies that support shipboard visual observations of clast changes throughout the record. Muddy diamictite intervals primarily have higher values of muscovite and natural gamma radiation (NGR), while interbeds of sandy and muddy diamictite show alterations in high values of quartz, L*, and K-spar/albite. Above Ross Sea Unconformity 2 (RSU2), diamictite variability within Pleistocene age strata appears to be compositionally different from below. The change in bulk mineralogy is consistent with an overall change in the variability in downhole NGR and magnetic susceptibility (MS) data. Down-core variations in geochemical facies presented, combined with sediment facies analyses and provenance scenarios, when compared to integrated studies from AND-1B, will contribute towards a better understanding of Antarctic ice stream variability during the late Miocene to Pleistocene.