Basement control on past ice sheet dynamics in the Amundsen Sea Embayment, West Antarctica

摘要

The development of landscapes and morphologies follows initially the tectonic displacement structures of the basement and sediments. Such fault zones or lineaments are often exploited by surface erosional processes and play, therefore, an important role in reconstructing past ice sheet dynamics. Observations of bathymetric features of the continental shelf of the Amundsen Sea Embayment and identification of tectonic lineaments from geophysical mapping indicate that the erosional processes of paleo-ice stream flows across the continental shelf followed primarily such lineaments inherited from the tectonic history since the Cretaceous break-up between New Zealand and West Antarctica. Three major ice flow trends correspond to different tectonic phases in east-west, northwest-southeast and north-south directions. East-west oriented basement trends correlate with coastline trends and overlay tectonic lineaments caused by former rift activities. Directional trends with northwest-southeast orientation are observed for the glacial troughs of the western embayment outer shelf, the western Pine Island Bay coastal zones, and the inner Pine Island glacial trough and are associated with a distributed southern plate boundary zone of the former Bellingshausen Plate. The north-south trend of the main Pine Island glacial trough and the north-northeast trend of the Abbot Ice Shelf trough on the outer shelf follow the predicted lineation trend of an eastern branch of the West Antarctic Rift System extending from the Thwaites drainage basin northward into Pine Island Bay. An understanding of this context helps better constrain the geometries and sea-bed substrate conditions for regional paleo-ice sheet models.