SYSTEMATIC MULTIPLE OSL DATING OF LONGITUDINAL AND TRANSVERSE (SOURCE-BORDERING) DUNE PROFILES IN MONSOONAL NORTHERN AUSTRALIA

Luminescence dating, particularly by optically stimulated luminescence (OSL), has revolutionised Quaternary dune chronologies of the past 2-300 ka. However, the paucity of natural exposures of deep dune profiles and the difficulties of OSL sampling of intact dune profiles at depth have often resulted in a dominance of relatively shallow dates and multiple sites with few dates in the literature. The upper portions of dune profiles are likely to be affected by ephemeral shallow aeolian reworking, bioturbation and pedogenesis. Resultant mixing of grains is likely to impact on the OSL age and raises questions regarding the veracity of periods of regional dune activity imputed from clusters of ages from multiple shallow sites.

We report the results of systematic OSL dating down dune profiles in the northern Great Sandy Desert of Western Australia with 14 dates through a 5m late Holocene longitudinal dune, 12 dates through a 10m Pleistocene longitudinal dune and 9 dates through a Pleistocene source-bordering transverse (lunette) dune. Though occurring in the semi-arid zone, these dunes are in the summer monsoon-watered part of the continent and therefore subjected to considerable seasonal pedogenic processes and are likely to be subject to bioturbation, particularly due to termites. The age profiles obtained are discussed in terms of the age(s) or dune building or mobility and indications of possible post-depositional sediment mixing.