Eolian and lacustrine evidence of late Quaternary palaeoenvironmental changes in southwestern Australia

Lake Lefroy and Lake Cowan occur in the relic Tertiary palaeodrainage that used to drain to the east in central western Australia. Lacustrine conditions prevailed during the late Neogene and the early part of the Quaternary. Strong aridity sets in during mid-Quaternary, resulting in extensive gypsum precipitation and eolian deposition in and around the playa lakes. Lakes Lefroy and Cowan are now hypersaline and deflating, with a salt crust developed on the lake floor and lunette dunes constructed along the eastern margins. Optical dating (green light-stimulated luminescence (GLSL) dating) of the lunette dunes along the eastern and southeastern margins of the playas and electron spin resonance (ESR) dating of relic gypsum dunes on the lake floor show that intensified eolian activity occurred during the last glacial period, with a major lunette construction phase occurring during the Last Glacial Maximum (LGM). 14C dating of high-lake deposits, which are extensively developed along the margins of Lake Cowan, suggested a significant high-lake event during the early to mid-Holocene. The late Quaternary eolian and lacustrine evidence of palaeoenvironmental changes supports the model that during the Last Glacial Maximum, the subtropical high-pressure cell intensified and probably shifted southward, displacing the southern westerlies.