Exposure Ages for Pleistocene Periglacial Deposits in Australia

Abstract

Pleistocene periglacial landforms are widespread in Australia and provide valuable information on past temperatures, but dating the time of their formation has proven difficult. To remedy this, we have explored the use of cosmogenic 36Cl for direct dating of periglacial deposits. We sampled six deposits in four locations in southeastern Australia, ranging from blockstreams and block slopes to former rock glaciers. Eighteen exposure ages reveal a concentration of periglacial activity during the last glacial maximum (LGM) between 16 and 23ka, with a population having a weighted mean age of 21.9±0.5ka. This age is shortly before the time of maximum ice advance during the LGM in southeastern Australia. Exposure dating of block deposits provides a way of extending the chronology of cold climate activity beyond glaciated regions.