Major episodes of Quaternary activity in the lower Neales River, northwest of Lake Eyre, central Australia

Abstract

Abstract The Lake Eyre Basin, Australia's largest internal drainage system, represents a key site in unravelling the complexities of terrestrial climate change. The basin, covering one-sixth of the Australian continent, spans a number of climatic zones, including the tropical monsoon system to the north and the mid-latitude westerly circulation to the south. This study describes four major episodes of Quaternary fluvial, lacustrine and aeolian activity in the Neales River, a western catchment of Lake Eyre. The first phase is represented by coarse-grained fluvial aggradation which dates to at least 170 ka. The depocentre of Lake Eyre is believed to have been located further to the east during this phase. The second episode is a phase of high lake level lacustrine deposition which occurred before 103 ka. The deltaic margin of the lake at this time was approximately 20 km west of the present playa. The third phase was characterised by significant base level lowering and channel incision after 50 ka but before 31 ka. Lake level lowering induced fluvial incision of up to 9 m, scouring several metres into the basal silicified Miocene sediments some time after 50 ka. The final phase was a period of aeolian and ephemeral-fluvial deposition which peaked between 20 ka and 18 ka, coincident with the Last Glacial Maximum. These episodes are compared with chronostratigraphic data from the monsoon dominated catchments of the Cooper and Diamantina Rivers. The nature and record of fluvial and lacustrine deposition are correlated throughout the basin during the penultimate and last interglacial cycles. The late Quaternary record is more ambiguous and further studies are required to elucidate the precise nature of climate change in the basin over the last 30 ka.