Late Miocene to Plio-Pleistocene Antarctic Ice-Sheet Behavior in Ross Sea Outer Continental Margin: Insights from Regional Seismic Stratigraphy and IODP Site U1522

Abstract

Regional seismic stratigraphic analysis with scientific drill site data can be used to understand past Antarctic ice-sheet behavior and associated sedimentary processes in the Ross Sea continental margin. However, the limited availability of seismic and drill site data in the outer shelf and slope of the Ross Sea has impeded our comprehensive understanding of the major seismic sequences between RSU3 and RSU2 (RSS-6) and above RSU2 (RSS-7/8). In this study, we present the results of a seismic stratigraphic analysis conducted on sedimentary sequences developed since the late Miocene (above RSU3). We correlate core-log-seismic data from IODP Exp. 374 Site U1522 with adjacent seismic profiles in the eastern Ross Sea outer continental margin. By comparing seismic facies of RSS-6 and RSS-7/8 with lithostratigraphy and physical properties from sediment cores and downhole logging data, we trace the RSU3 and RSU2 seismic reflectors across the continental shelf and slope. The mapping results of the reconstructed RSU3 and RSU2, along with the stacking patterns of RSS-6 and RSS-7/8, represent the different evolution of paleo-shelf breaks and depocenters at the major glacial troughs of the eastern and western parts of the Ross Sea. During the late Miocene (RSU3) to early Pliocene (RSU2), the progradation of the paleo-shelf break was observed at all glacial troughs. However, during the Plio-Pleistocene (above RSU2), a shift from progradation to aggradation occurred, except for the Pennell and JOIDES Troughs, which are located in the central region of the Ross Sea. This suggests a more stable condition of grounded ice during small-scale deglaciation in the central part of the Ross Sea, likely due to the relatively high topography of Pennell Bank. The thicker and larger extent of depocenters of RSS-6 and RSS-7/8 are found in the eastern Ross Sea, contrasting with the western Ross Sea. This distribution implies a more pronounced advance and retreat of the ice sheet in the eastern Ross Sea margin.