INVESTIGATING THE FORMATION OF LINEAR DUNES IN ARID AUSTRALIA USING OPTICALLY STIMULATED LUMINESCENCE DATING

More than one third of the Australian continent is covered by desert dunes. In this arid environment, aeolian records represent a major source of potential palaeoenvironmental information. Records of aeolian response to climatic change, however, are beset by limitations such as discontinuous preservation and a reliance on chronologies. Nevertheless, substantial developments have been made in our understanding of the palaeoenvironmental history of Australia’s arid zone, through the increasingly widespread application of optically stimulated luminescence (OSL) dating of aeolian sediments to provide large-scale chronologic frameworks. When combined with regional geomorphic and stratigraphic information, large scale studies assist in elucidating the timing and formation of desert dunes. Here we assess the utility of OSL dating for understanding linear dune formation in arid central Australia, based on a chronology from 30 sites. The regional dataset reveals that dunes preserve up to four stratigraphic horizons, indicating multiple periods of reactivation. Dune construction occurred when sediment was available for aeolian transport, primarily during relatively arid conditions. Aeolian stratigraphic units are bounded by paleosols which represent phases of increased environmental stability. The preservation of dune stratigraphy, however, appears to vary between individual features. The chronostratigraphies of some dunes record relatively rapid sediment accumulation prior to stabilisation, implying intensive reworking during arid phases and preservation only of the most recent event preceding pedogenesis. At other sites longer age ranges are preserved within individual aeolian units, suggesting extended or intermittent periods of relative aridity and less intensive reworking of underlying sediment. These results highlight the importance of an approach combining age-depth relationships down dune profiles with large scale studies to eliminate sampling bias. Large scale OSL chronologies for dunefield formation enable comparison with palaeoenvironmental proxies from beyond the region, suggesting that dune construction coincided with cold, arid conditions during marine isotope stages 4, late 3 and 2, and warm, dry climates during 14-10 ka and the late Holocene.