HOW DO LONGITUDINAL DUNES RESPOND TO CLIMATE FORCING? INSIGHTS FROM 25 YEARS OF LUMINESCENCE DATING OF THE AUSTRALIAN DESERT DUNEFIELDS

A meta-analysis of 689 luminescence age estimates of Australian desert sand dunes aimed to examine the hypothesis that Quaternary climate changes have forced dune accumulation and to understand longitudinal dune behaviour from the age-architecture of sand dunes for which stratigraphic information is often absent or poorly known. A novel approach to the analysis of probability density curves of dune age frequency shows that in the Mallee dunefield of SE Australia only the LGM (18-34 ka) experienced marked dune growth which cannot be explained by random background noise. During the LGM, most, but not all, Mallee longitudinal dunes were accumulating more rapidly than before and after. In the Strzelecki dunefield of central Australia source-bordering longitudinal dune TL and OSL ages are more frequent at the Pleistocene – Holocene transition but nearby free longitudinal dunes were only active above background levels during the LGM. However, the Strzelecki dune age data set suffers from being drawn from a small number of individual dunes with a marked bias away from surficial (young) and basal (old) ages. Even during the LGM, many dunes do not record active growth and the dunefield was most likely a mosaic of stable dune surfaces and bare mobile patches, supported by the scant pollen data from the arid zone. Hyper-aridity has not been experienced in these dunefields. These vegetated dunes exhibit conservative behaviour with limited response to the range of climate forcing experienced in the late Pleistocene. A more complete understanding of dunefield response to Quaternary climates would require an intensive and structured dating program yet the strong possibility remains that no coherent palaeoclimate record will result because of the strength of self-organising and stochastic processes in these dunes.