Preglacial to glacial sediment thickness grids for the Southern Pacific Margin of West Antarctica

Abstract

AbstractCircum‐Antarctic sediment thickness grids provide constraints for basin evolution and paleotopographic reconstructions, which are important for paleo‐ice sheet formation histories. By compiling old and new seismic data, we identify sequences representing preglacial, transitional, and full glacial deposition processes along the Pacific margin of West Antarctica. The preglacial sediment grid depicts 1.3–4.0 km thick depocenters, relatively evenly distributed along the margin. The depocenters change markedly in the transitional phase at, or after, the Eocene/Oligocene boundary when the first major ice sheets reached the shelf. Full glacial sequences, starting in the middle Miocene, indicate new depocenter formation North of the Amundsen Sea Embayment and localized eastward shifts in the Bellingshausen Sea and Antarctic Peninsula basins. Using present‐day drainage paths and source areas on the continent, our calculations indicate that an estimated observed total sedimentary volume of ∼10 × 106 km3 was eroded from West Antarctica since the separation of New Zealand in the Late Cretaceous. Of this, 4.9 × 106 km3 predates the onset of glaciation and need to be considered for a 34 Ma paleotopography reconstruction. Whereas 5.1 × 106 km3 postdates the onset of glaciation, of which 2.5 × 106 km3 were deposited in post mid‐Miocene full glacial conditions.