EXPOSURE DATING OF GLACIAL ERRATICS FROM THE SOUTHERN ELLSWORTH MOUNTAINS, ANTARCTICA

Dating of glacial deposits in Marie Byrd Land, central West Antarctica and the Ross Sea indicates that the West Antartic Ice Sheet (WAIS) reached its maximum size thousands of years after the Northern Hemisphere ice sheets and that deglaciation continued into the Holocene. However, there is little evidence to constrain the timing of deglaciation elsewhere in West Antarctica. We are dating erratics from the Marble Hills in the southern Ellsworth Mountains to investigate the deglaciation history of the Weddell Sea sector of the ice sheet.

Glacial erratics, spanning altitudes from 1390 to 980 meters, were collected from surfaces overrun during the last glacial maximum and exposed as the ice sheet thinned. The apparent ages of three samples analyzed predate the last glacial maximum. We interpret these results as evidence of recycling and prior exposure. A fourth sample collected ~160 meters above the ice margin yielded an age of 4100 ± 300 years, indicating significant late Holocene ice retreat. This preliminary result may suggest delayed deglaciation as seen in the Ross Sea sector of the WAIS. Analysis of the remaining samples, currently in progress, will provide a representative thinning history for ice flowing into the southern Weddell Sea.