The Timing of the Last Glacial Maximum in Australia

Abstract

Late Pleistocene glaciation of Australia was restricted to the Snowy Mountains and the Tasmanian highlands. Glaciers were most extensive in Tasmania where ice caps formed on the Central Plateau and West Coast Ranges, and systems of valley and cirque glaciers formed on surrounding mountains. To investigate the timing of maximum glacier advance during the Last Glacial Maximum (LGM), we dated boulders on 18 moraines in 8 glaciated areas using cosmogenic 36Cl and 10Be. We sampled moraines deposited by cirque and valley glaciers, in a range of climate types and lithologies over a 7° latitudinal and a 1430m altitudinal transect. Exposure ages for LGM moraine boulders group tightly in the range 17-20 ka. Boulders from the Hamilton moraine, often treated as the LGM type moraine, range in age from ∼190-350 ka, indicating that it was deposited well before the last glaciation. Collectively, the exposure ages show that southeastern Australia was glaciated briefly during and after the LGM, and deglaciated well before the Holocene. Ice retreated from the terminal moraines after the period of coldest sea-surface temperatures in the southwest Pacific Ocean. No evidence was found for readvance of glaciers during the Antarctic Cold Reversal or the Younger Dryas period.