The 14C Record of Late Pleistocene Ice Advance and Retreat in the Central Ross Sea, Antarctica

Abstract

Twenty-three AMS radiocarbon dates obtained from central Ross Sea sediment cores constrain the timing of ice advance across the continental shelf and highlight the difficulties of determining a chronology of ice-sheet retreat in this region. Ages derived from till and postglacial sediments are bimodally distributed and the majority of dates are >20 14C ka. The dates obtained from the acid-insoluble organic fraction of till indicate that grounded ice advanced across the inner central Ross Sea continental shelf 17.8 ± 1 14C ka. Benthic foraminifera from till on the outer shelf indicate that grounded ice reached its maximum position after 13.8 14C ka indicating that the Ross Sea sector of the Antarctic ice sheet was advancing as eustatic sea level was on the rise. Postglacial sediment sequences in the central Ross Sea are up to 70 cm thick, and the ages are older than those from the western Ross Sea. These postglacial sediments produced ages >20 14C ka (uncorrected) that are apparently inconsistent with the timing of ice advance and preclude development of a high-resolution chronology of ice-sheet retreat. Surface sediments deposited under open-marine conditions in the central Ross Sea typically range from 4000 to 6000 14C yr BR Total organic carbon (TOC) measurements for the dated sediments in this study reveal no significant relationship between TOC content and reported 14C age.