Early to Mid-Pleistocene Warm Events at the Antarctic Margin

The response of the Antarctic Ice Sheets and the Southern Ocean to warm events during the Pleistocene is ambiguous. Marine Isotope Stage 31 (MIS; 1.07 Ma) occurred during some of the highest Southern Hemisphere insolation values of the Plio-Pleistocene, and is the last known interval where there is direct evidence that the marine-based Antarctic Ice Sheet was smaller than present in the Ross Embayment, while a carbonate rich interval deposited ~1 Ma on the continental rise off Prydz Bay has also been documented. We examine a well-dated, new record of Marine Isotope Stage 31 from a continental rise drill core collected during Integrated Ocean Drilling Program Expedition 318 to the Wilkes Land margin of East Antarctica. Marine Isotope Stage 31 is unique in Plio-Pleistocene intervals recovered from Expedition 318 sediment drill cores in that it contains several ~1m thick intervals of bioturbated carbonate-bearing (i.e. >10% carbonate) mudstones. These are interbedded by massive and finely laminated mudstones indicating a strong cyclicity that is operating at likely Milankovitch-scale frequencies. We present a multi-proxy dataset, including sedimentary, geochemical and microfossil data from planktonic foraminifera, diatoms, bulk sediments, and molecular organic biomarkers, that provides new insight into changing water mass properties and sea-surface temperatures through several Early- to mid-Pleistocene glacial/interglacial cycles, including the peak warmth of MIS 31. Characterizing the sedimentary and geochemical signature of the well-dated MIS 31 interval may also afford an opportunity for identification in Expedition 318 (and other East Antarctic margin) sediments of similar warm periods/glacial cyclicity during Late Pleistocene interglacials. These new records will be examined in the context of records recovered from ANDRILL, Cape Roberts Project and ODP site 1165.