Geodynamic and tectonic processes played a dominant role in forming the present topographic relief of West Antarctica and are responsible for the largest submarine-based, and therefore most sensitive, ice sheet on Earth. The Geophysics Section at AWI exercises a leading role in deciphering the evolution of these geodynamic and tectonic processes and their function with respect to the West Antarctic Ice Sheet history and dynamics.

The extension, and subsequent separation, of New Zealand and West Antarctica dominate the tectonic signature of the Pacific continental margin of West Antarctica. This divergence of the Pacific and Antarctic plates led first to rifting and crustal extension between Chatham Rise (New Zealand) and the Amundsen Sea Embayment off easternmost Marie Byrd Land (West Antarctica) as early as 90 Ma. Rifting possibly continued within the Great South Basin between the Campbell Plateau and the South Island of New Zealand until its abandonment in favour of a new extensional locus to the south, forming the earliest oceanic crust between Campbell Plateau and Marie Byrd Land by 84-83 Ma.

At least three phases of tectonic deformation occurred along the West Antarctic margin and on the Amundsen Sea shelf: (1) distributed rifting events parallel to the breakup front, (2) the influence of the Bellingshausen Plate motion with a plate boundary through the Amundsen Sea Embayment, and (3) activity of early branches of the eastern West Antarctic Rift System. Geophysical data infer that the eastern Amundsen Sea Embayment shelf and its Pine Island Bay host tectonic lineaments and sedimentary basins formed by the West Antarctic Rift System. At times between 48 and 26 Ma, the West Antarctic Rift System east of the Ross Sea operated in either dextral strike-slip or extensional motion throughout the region to the south and east of the Amundsen Sea Embayment and in the Bellingshausen Sea sector, connecting eventually to a Pacific-Phoenix-East Antarctic triple junction via the Byrd Subglacial Basin and the Bentley Subglacial Trench of Marie Byrd Land. It is possible that an eastern arm of this early manifestation of the rift exists as a north-south striking zone of thinned crust in Pine Island Bay.

In ongoing studies, we further analyze existing and new seismic records together with collected gravity, magnetic and geothermal heat-flow data to improve our understanding of the role of the Amundsen Sea and Bellingshausen Sea shelves and margins in context of the continental breakup, activities of the West Antarctic Rift System and the evolution and dynamics of the West Antarctic Ice Sheet.