Abstract The behaviour of ice caps and glaciers on sub-Antarctic islands during previous periods of warming provide key empirical evidence for understanding the behaviour of marine ice sheets in the future. However, the extent of ice on sub-Antarctic islands during the last 100 kyr is poorly constrained. Here, we investigate the past glacial extents on South Georgia, where previous Last Glacial Maximum (LGM) reconstructions vary between small fjord-terminating glaciers and a large marine-based ice sheet. To help resolve this uncertainty, we apply Schmidt hammer relative-age dating to measure rock hardness and, thus, exposure age of a range of glacial deposits. Applying a hardness–age calibration curve constructed from well-dated Holocene, late-glacial deposits and terminal LGM deposits, we determine that deglaciation of the approximately 600 m-high peaks on the outer Lewin Peninsula occurred during the latter half of the last glacial stage, and probably the end of the LGM. We infer that South Georgia was covered by a marine-based ice cap during the latter part of the last glacial stage.

Abstract Landforms and sediments in the Prince Charles Mountains record the timing and magnitude of Cenozoic palaeotopographic changes in the Lambert Glacier–Amery Ice Shelf system. A review of geomorphic and sedimentological evidence indicates that considerable (>1–2 km) glacial incision into a pre-glacial palaeosurface occurred along the major outlet glaciers during the Cenozoic. This erosion was in turn the likely driver for uplift that averaged c. 50 m/Ma along the flank of the Amery Ice Shelf since at least the mid-Miocene Epoch. The volume of eroded material is an order of magnitude greater than the quantity of sediment presently preserved in Prydz Bay, suggesting considerable export of Cenozoic sediment off the continental shelf. The magnitude of erosion recorded in the Prince Charles Mountains is sufficient to have focussed Cenozoic ice-drainage patterns, but was too slow to have driven Quaternary changes in ice volume.