Multiproxy analysis of sediment collected from the Glomar Challenger Basin and the slope and rise area (eastern Ross Sea, Antarctica)

The West Antarctic Ice Sheet (WAIS) experienced several advances and retreats during past glacial and interglacial periods. According to several authors (e.g. Halberstadt et al., 2016; Anderson et al., 2019; Lowry et al., 2020), the WAIS was grounded near the continental shelf break during the Last Glacial Maximum (LGM). Previous works (e.g. Bart et al., 2018) suggested an early retreat of the ice sheet in the Easter Ross Sea (ERS). Nevertheless, post-LGM glacial retreat requires further investigation (Lowry et al., 2020). A series of gravity cores and box cores have been selected along a transect from the inner continental shelf of the Glomar Challenger Basin to the slope and rise area. These cores have been collected during several PNRA expeditions and studied in the frame of the STREAM project (Late Quaternary evolution of the ocean-ice sheet interactions: the record from the Ross Sea continental margin, Antarctica) and the ANTIPODE project (Onset of Antarctic ice sheet vulnerability to ocean conditions). X-ray and sedimentological (magnetic susceptibility, water content, grain size), micropaleontological (foraminifera), geochemical (IPSO25, sterols, TOC) and chemical (XRF measurements) analyses have been performed. Radiocarbon ages have been obtained using organic matter. The aim of this work is to reconstruct the evolution of the WAIS dynamics in the Glomar Challenger and the slope and rise area during Late Quaternary. The results of this work allowed us to recognize three main sedimentary units: 1) Glacial unit: sediments deposited by the advancing ice sheet likely occurred during the Last Glacial Maximum; 2) Deglacial unit: sediment with high ice rafted debris (IRD) content deposited during the ice sheet retreat; 3) Open marine unit: Holocene muddy sediments characterized by higher biogenic content. These sediments are coarser (gravelly and sandy) near the continental shelf margin, suggesting winnowing of fine material and increased IRD supply. References Anderson et al., 2019. Seismic and geomorphic records of Antarctic Ice Sheet evolution in the Ross Sea and controlling factors in its behavior. Geol. Soc., London, Special Publications 475, 223-240. Bart et al., 2018. A centuries-long delay between a paleo-ice-shelf collapse and grounding-line retreat in the Whales Deep Basin, Easter Ross Sea, Antarctica. Sci. Rep. 8, 1-9. Halberstadt et al., 2016. Past ice-sheet behavior retreat scenarios and changing controls in the Ross Sea, Antarctica. The Cryosphere 10, 1003-1020. Lowry et al., 2020. Geologic controls on ice sheet sensitivity to deglacial climate forcing in the Ross Embayment, Antarctica. Quat. Sci. Adv. 1, 100002.