Depositional history of the West Antarctic continental margin off Marie Byrd Land and the implication for a dynamic West Antarctic Ice Sheet

The evolution of the West Antarctic continental margin was significantly influenced by the growth, advance and retreat of the West Antarctic Ice Sheet (WAIS) since the Miocene. Seismostratigraphic studies of the continental margin have highlighted the influence of a dynamic oceanographic setting on the WAIS and understanding the connection between the two may aid in predictions of future grounding line retreat. Reconstructions of the history of the ice sheet and its relationship with the continental margin have, however, focused on individual marine embayments, such as the Ross Sea and Amundsen Sea, with little connectivity in between. Using new seismic reflection data acquired in 2019 offshore central Marie Byrd Land, combined with drill site data from IODP Expedition 379, a new seismostratigraphic model has been produced which fills the gap between the Ross and Amundsen Seas. This model allows for direct comparison of shelf-to-rise seismostratigraphy and the timing of major erosional and depositional events on the continental shelf between the two embayments. A distinct asynchrony is observed between the Ross and Amundsen Seas, wherein major growth of the WAIS and changes to the subglacial system occur at different times. Possible causes of this asynchrony remain unclear, but may be due to the influence of the East Antarctic Ice Sheet and/or differing oceanographic settings between the two embayments. In addition, the model allows for the analysis of the deeper basin of the continental rise and the evolution of this poorly understood part of the continental margin. Preservation of buried channels and sediment drifts within the sedimentary cover paints a picture of dynamic downslope and along-slope depositional processes. Further east-west asynchrony along this part of the continental margin reflect differences in the dominant sedimentary processes in the Amundsen and Ross Seas, which further adds to the spatial disparity in advance and retreat of the WAIS along the continental margin.