Depositional history and archaeology of the central Lake Mungo lunette, Willandra Lakes, southeast Australia

Lake Mungo, presently a dry lake in the semi-arid zone of southeastern Australia, preserves a unique record of human settlement and past environmental change within the transverse lunette that built up on its downwind margin. The lunette is >30 km long and the variable morphology along its length suggests spatial variability in deposition over time. Consequently this presents differential potential for the preservation of past activity traces of different ages along the lunette. Earlier work at Lake Mungo focused primarily on the southern section of the lunette, where two ritual burials of considerable antiquity were found. Here we describe the depositional history of the central section of the Lake Mungo lunette, together with the first single grain optically stimulated luminescence (OSL) chronology of the full stratigraphic sequence and of three hearths. We thereby lay the foundation for systematic investigation of the distribution of archaeological traces through the sedimentary record. The older depositional units (Lower and Upper Mungo) were deposited ca. 50–40 ka and ∼34 ka respectively, and are substantially thinner in the central section of the lunette compared with the south. By contrast, the overlying unit of interbedded sands and clayey sands (Arumpo–Zanci units), deposited ca. 25–14 ka, is markedly thicker and dominates the stratigraphic sequence in the central portion of the lunette. Although the sequence broadly reflects previous models of the lunette's depositional history and changing hydrological conditions, our results indicate spatially variable deposition of sediments, possibly as a result of changes in prevailing wind regimes. Archaeological traces are exposed in all stratigraphic units deposited after ca. 50 ka, including sediments deposited after the final lake drying ca. 15 ka, indicating human occupation of the area under a range of palaeoenvironmental conditions. Dating and stratigraphical examination of individual hearth features demonstrates that even within individual stratigraphic units, human occupation persisted under variable conditions. Mid-Holocene occupation of the area following the final lake retreat took place during a period of relatively humid climate.