Holocene Deglaciation of Mac.Robertson Land, East Antarctica

Changes in East Antarctic Ice Sheet volume exert a fundamental control on eustatic sea level, but ice sheet fluctuations are poorly documented since the Last Glacial Maximum. 10-Be and 26-Al exposure dating of 21 glacial erratic boulders from the Framnes Mountains, Mac.Robertson Land enables us to test whether the East Antarctic Ice Sheet was the source of Meltwater Pulse 1A, a rise in eustatic sea level of 20 m that occurred in less than 500 years at c. 14,600 years BP. Exposure ages show that the ice sheet remained at its maximum extent until c. 12,000 years BP, when geomorphic evidence indicates that 350 m of ice sheet thickening occurred near the present-day coastline, declining to less than 100 m at a distance of 70 km inland. The ice sheet reached its present elevation by c. 5000 years BP, at a time when eustatic sea level stabilised. The rate and volume of ice loss and timing of deglaciation in the Framnes Mountains does not support the hypothesis that the East Antarctic Ice Sheet was the source of Meltwater Pulse 1A. Conversely, our data indicate that deglaciation of Mac.Robertson Land occurred during the Holocene, and took thousands of years to complete.