East Antarctic continental shelf: Prydz Bay and the Mac.Robertson Land Shelf

© The Geological Society of London 2014. Prydz Bay and the Mac.Robertson Land Shelf exhibit many of the variations seen on Antarctic continental shelves. The Mac.Robertson shelf is relatively narrow with rugged, inner-shelf topography and shallow outer-shelf banks swept by the westflowing Antarctic Coastal Current. U-shaped valleys cut across the shelf. It has thin sedimentary cover, deposited and eroded by cycles of glacial advance and retreat through the Neogene and Quaternary. Modern sedimentation is diatom-rich siliceous, muddy ooze in shelf deeps, while, on the banks, phytodetritus, calcareous bioclasts and terrigenous material are mixed by iceberg ploughing. Prydz Bay is a large embayment fed by the Amery Ice Shelf. It has a broad inner-shelf deep area and outer bank, with depths ranging from 2400 m beneath the ice shelf to 100 m on the outer banks. A clockwise gyre flows through the bay. Fine mud and siliceous ooze drape the seafloor; however, banks are scoured by icebergs to depths as great as 500 m. The Mac.Robertson shelf has seen advances to the shelf edge during glacial episodes and retreat during warming and rising sea level. Prydz Bay shows more complexity, with parts of the bay showing partial advance of the ice-grounding zone.