Glacial-age water resources in inland southeastern Australia
The distribution of water resources has long been recognised as a fundamental constraint upon the occupation of inland Australia. Therefore, the record of water resources is used in turn as a proxy for human settlement patterns and population levels in the interior. Quaternary environments and water resources reconstructed from archives in lakes, rivers and dunes formed over the last glacial cycle across the riverine plains of Australia’s Murray-Darling Basin have been interpreted as indicating severe aridity in the late Pleistocene leading into, and following, the Last Glacial Maximum ~22 ka. However, lake-level and palaeochannel records have been studied in isolation, making it difficult to establish the regional significance of hydrological change at important archaeological sites like the Darling and Willandra Lakes. Our study compares the record of floodplain lakes from the Willandra Lakes system with the record of the lower Lachlan River, and the main feeder channel to the lake before avulsion caused its drying in the late Pleistocene. Electromagnetic surveys, geomorphological and sedimentary investigations provide evidence to reconstruct the history of the various channel belts of the Lachlan River. Single grain optical stimulated luminescence dating of floodplain sediments indicates that channel avulsion had created the Middle Creek channel belt before 18.4 ka. A second avulsion had moved the upper reaches of the new channel belt to the location of the present Lachlan River by 16.2 ka. Within the Willandra Palaeochannel along the present Willandra Creek, nested floodplains and declining channel dimensions indicate a two-stage reduction in flow. The timing of these events is consistent with palaeohydrological and archaeological information contained in the Willandra Lakes record and with the record of palaeochannels on the Lachlan River upstream. These ages reinforce the regional significance of the Willandra Lakes palaeoclimate record, which shows substantially increased inflows during the Last Glacial Maximum. This highlights the need to combine fluvial archives with lake records to build complementary and more complete records of hydrological change in lowland riverine plains, and to better understand the constraints of geography and water resources on human settlement of continental Australia.
About the Presenter
Dr Justine Kemp is a Senior Research Fellow and Lecturer in Environmental Science in the School of Environment at Griffith University. She is a fluvial geomorphologist who uses sedimentology, geochronology and hydrology to understand Australia’s distinctive river systems and the ways in which they respond to environmental change, natural and human induced. Her primary focus is the perennial rivers of eastern Australia, but she has also studied rivers in Scotland, England, and Finland. She is particularly interested in the effects of large floods on river form and sediments, and the sensitivity of Australian rivers to changes induced by people. She is currently working on a major Australian Research Council project to investigate the co-evolution of inland riverine landscapes and early modern human societies in the Lachlan-Willandra system over the last 30,000 years.