A SEDIMENTOLOGICAL AND GEOCHEMICAL APPROACH TO ELUCIDATING ANTARCTIC ICE SHEET EXTENT IN THE LATE MIOCENE TO PLIOCENE: INITIAL RESULTS FROM IODP SITE U1522 ON THE ROSS SEA CONTINENTAL SHELF

Understanding how ice sheets respond to warmer temperatures is critical to predicting future sea level rise. The marine-based West Antarctic Ice Sheet is particularly vulnerable to increasing ocean temperatures; however, a lack of ice-proximal records limits the ability of modelers to use paleoclimate data to better constrain potential future ice sheet retreat. International Ocean Discovery Program (IODP) Expedition 374 collected Neogene sequences at five sites on the Ross Sea continental shelf and slope/rise that provide insight into ice sheet advance and retreat. Site U1522, in the Glomar Challenger Basin on the Ross Sea continental shelf, was cored in 558 m of water, penetrated to ~702 m below seafloor (mbsf), and recovered ~280 m of core (40%). The site targeted a seismic sequence of massive and laminated acoustic facies interpreted as interbedded glacial, glaciomarine, and open marine deposits. Our study targets the more consolidated sediments below 200 mbsf, which consist of Pliocene diatom-bearing sandy to muddy diamictite interbedded with diatom-bearing mudstone and upper Miocene diatom-bearing to -rich diamictite and diatomite. We present X-ray fluorescence (XRF) core scanning results, calibrated with major and trace element analyses on discrete samples using inductively coupled plasma-mass spectrometry (ICP-MS), that provide a high-resolution record of late Miocene to Pliocene sedimentary geochemical variations. These data, coupled with X-ray diffraction (XRD) bulk mineralogy and sedimentary facies analyses, are used to evaluate late Miocene to Pliocene changes in relative ice sheet proximity and sediment provenance. We also use downhole logging data to assess lithological variations across core gaps. Initial results reveal cyclical (m to 10s of m) geochemical variations that may reflect changes in provenance. This integrated approach allows us to develop a better understanding of Antarctic ice sheet sensitivity in a warming world.