Dynamics of Pliocene East Antarctic Ice Sheet from depositional signatures of the Prydz Bay shelf and Trough Mouth Fan

The Pliocene saw multiple advances and retreats of the ice-sheet margin in East Antarctica. Amery Ice Shelf (AIS) is the largest ice shelf in East Antarctica and also the largest single ice stream draining from the Antarctic Plateau. It buttresses the Lambert Glacier drainage system, and accounts for 14% of the outflow from the East Antarctic Ice Sheet (EAIS). However, evidence for the state of the EAIS during the Pliocene is sparse and difficult to interpret unequivocally. Marine geological-geophysical data collected from the continental shelf in Prydz Bay, Antarctica, including seismic-reflection data, bathymetry, core records from ODP drilling and gravity coring sites, reveal a complex paleo-subglacial drainage system linked to an offshore depositional regime dominated on a trough mouth fan (TMF). Detailed seismic stratigraphic and facies analysis reveals the glacial evolution of Prydz Bay shelf and its TMF, including several glacial expansions across the shelf indicated by erosional surfaces and stratal bodies with chaotic acoustic character. The geometry of seismic sequences suggests that the glaciers and their associated TMF developed after a major episode of shelf and slope erosion during the Pliocene-Pleistocene.

 The shelf in Prydz Bay is dominated by a wide, south-north trending glacially-eroded trough (the Prydz Channel: -500~-1000 m depth) and shallower banks (-500~0 m depth). Well preserved grounding zone wedges areevidenced by prograding foreset deposits. Evidence for erosion of the wedges and/or lineations that extend across their upper surfaces indifferent water depths ranging from 200 m to 800 m imply their formation during multiple glacial stages or cycles.  Stacked erosional surfaces reveal major cross-shelf glacial expansions and the development of deep channel systems (up to -500 m depth) associated with extensive subglacial meltwater in Prydz Bay. These glacial related features provide good constraints for reconstructing the stability of the Pliocene EAIS.