Holocene hydrologic variability in temperate southeastern Australia: An example from Lake George, New South Wales

Lake George is one of the largest freshwater lakes in Australia when full, and provides one of the most complete records of Quaternary sedimentation in the southeastern part of the continent. The lake is currently ephemeral, but sediments within the basin preserve evidence of multiple permanent and dry lake conditions in the past. We present an optically stimulated luminescence (OSL) chronology of recent lake shoreline sediments in order to reconstruct Holocene hydrologic variability at Lake George, providing past climatic context for the presently ephemeral lake conditions. The OSL chronology indicates three distinct periods of permanent lake conditions up to 15-18 m depth over the Holocene period, at approximately 10-8, 6-2.4 and 0.7-0.3 ka, with lower lake levels occurring in between those events. There appears to be a trend towards lake regression over this period despite relatively recent high lake levels. The chronology is broadly synchronous with comparable records of Holocene climatic variability across southeastern Australia. We also investigate the intrinsic luminescence characteristics of different sediment types as diagnostic tools, but these appear not to be appropriate in this context or form.