The Corangamite lakes system, southeastern Australia: testing the mega-lake hypothesis, and a first chronology for eolian activity

The Corangamite basin in temperate southeastern Australia is a complex system of lakes and their shorelines, basaltic volcanoes and stony rises, and quartz-rich eolian deposits, including dunes and sandy patches. Repeated Quaternary volcanism within the basin has altered the drainage patterns and distribution of swamps, ephemeral and permanent lakes over time. A major flooding event in the 1950s prompted the hypothesis that the many lakes within the basin once formed a single mega-lake, with Lake Murdeduke constituting the easternmost margin. In this study, we test the mega-lake hypothesis using remotely sensed digital elevation modelling combined with the first optically stimulated luminescence (OSL) dating of lake shorelines in this basin. We identify three possibilities for a mega-lake, two of which pre-date Pleistocene volcanic activity. None of these extend as far as Lake Murdeduke as previously hypothesised. We establish that lake-full conditions at lakes Beeac (in the central basin) and Murdeduke occurred at ca 42 ka and ca 33.6 ka, respectively, coeval with lake-full events elsewhere in southeastern Australia. We also investigate the contribution of eolian processes in the basin by providing a first OSL chronology of quartz-rich dunes and sandy patches. Two sites record eolian activity dating to the earlier part of the extended Last Glacial Maximum in Australia and may indicate strengthened westerly winds around this time. Four < 220 y ages indicate substantial eolian reworking and redeposition associated with rapid land-use change subsequent to European colonisation. Although incomplete owing to the difficulty accessing sites in this region with its relatively long history of private land ownership, this first chronology for past eolian activity provides an opportunity to understand this complex landscape in a more quantitative way.