Pleistocene Lake Brachina: a preliminary stratigraphy and chronology of lacustrine sediments from the central Flinders Ranges, South Australia

A preliminary interpretation of Upper Pleistocene lacustrine sediments from Brachina Gorge in the central Flinders Ranges of South Australia is presented. Based upon AMS carbon-14 dating, our results indicate that depositional environments in the Flinders Ranges varied considerably during the Late Pleistocene, During this time period, the environment responded to both regional climatic forcing and local factors which modified regional trends. Prior to ca 28 ka BP, rapidly developing dust mantles altered local hydrology by reducing runoff and increasing infiltration. When combined with a regionally wetter climate, fluvial sedimentation is interpreted to have been more extensive and continuous than today. Between ca 28 and 20 ka BP conditions stabilised resulting in widespread soil development within the recently deposited fluvial sediments. Shortly after ca 20.5 ka BP a sudden blockage established lacustrine conditions in Brachina Gorge. Under the influence of reduced evaporation and increased orographic rainfall, semi-permanent lacustrine conditions existed between ca 20.5 and 16 ka BP. In recording environmental change during the height of the last glacial maximum, Brachina Gorge will provide an important site to observe changes in climate from an area which regionally was undergoing deflation and non-deposition.