Leg 188 Sythesis: Transitions in the Glacial History of the Prydz Bay Region, East Antarctica, from ODP Drilling

Drilling during Leg 119 (1988) and Leg 188 (2000; Sites 1165-1167) of the Ocean Drilling Program (ODP) provides direct evidence for long- and short-term changes in Cenozoic paleoenvironments in the Prydz Bay region. Cores from across the continental margin reveal that in preglacial times the present shelf was an alluvial plain system with austral conifer woodland in the Late Cretaceous that changed to cooler Nothofagus rainforest scrub by the middle to late Eocene (Site 1166). Earliest recovered evidence of nearby mountain glaciation is seen in late Eocene-age grain textures in fluvial sands. In the late Eocene to early Oligocene, Prydz Bay permanently shifted from being a fluvio-deltaic complex to an exclusively marine continental shelf environment. This transition is marked by a marine flooding surface later covered by overcompacted glacial sediments that denote the first advance of the ice sheet onto the shelf. Cores do not exist for the early Oligocene to early Miocene, and seismic data are used to infer the transition from a shallow to normal depth prograding continental shelf with submarine canyons on the slope and channel/levees on the rise.

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