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Philip O'Brien, Geoscience Australia (Australia)
Alix Post, Geoscience Australia (Australia)
Mark Hemer, CSIRO Marine and Atmospheric Research (Australia)
Mike Craven, Australian Antarctic Division (Australia)
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The drainage basin feeding the Amery Ice Shelf is one of the largest in East Antarctic. At present the Amery Ice Shelf floats over a cavity 550 km long and up to 2400 m deep. During the last glacial cycle, the grounding zone reached 618 km north of its present position where it built grounding zone wedges obliquely across Prydz Channel. Cores from Prydz Bay and ODP drilling on the continental slope suggest that this position is as far north as the grounding zone has reached since the mid Pleistocene. Exposure dating in the Prince Charles Mountains likewise indicates only xx m increase in ice surface heights during the last glacial cycle.
Retreat from this extended position commenced about 15 ka though this is based on the AMS dating of the earliest marine organic carbon advected into the cavity. Older sediments contain abundant recycled carbon and so give old dates. The initial phase of retreat saw deposition on of grounding zone facies such as pelletised muds formed by compressed englacial material melted out of the base of the ice and cross bedded sands and gravels formed by tidal pumping and thermohaline circulation in the cavity. The limited increase in glacial ice thicknesses when compared to adjacent areas such as the Mac.Robertson Shelf reflects the continentality of the Amery Lambert drainage system which, in many areas received less precipitation during the cold phases of Late Pleistocene cycles than during warm phases.
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