THE USE OF PROTOLITH ZIRCON-AGE FINGERPRINTS IN DETERMINING THE PROTOSOURCE AREAS FOR SOME AUSTRALIAN DUNE SANDS

Utilising a combination of SHRIMP U-Pb dating of single zircon grains and specially constructed 'expected' zircon-age histograms the provena nce or protosource areas for sediment samples have been determined and the percentage inputs from these areas established. The 'expected' hi stograms and accompanying text provide an up-to-date summary of the ge ochronologic development of major basement areas in Australia concentr ating on crust-forming and high-level metamorphic events and their rel ative importance. These histograms may therefore be considered as the zircon 'fingerprints' of major Australian basement terranes. This meth od has been successfully applied to protosource determination in Quate rnary sand samples from the Australian Continental Dunefields. In each of three examples protosource areas have been determined and in sampl es containing more than one protosource the relative inputs have been estimated. From the results of this study the following conclusions ca n be drawn regarding the formation of the Australian deserts. Firstly, each individual desert is composed of material from several different protosource areas, some of these are local while others are up to 850 km away. Secondly, most of these protosource areas no longer contribu te sediments to the dunefields, suggesting substantial changes have oc curred in climatic regime and sediment transport patterns in Australia . Finally, there appears to have been only a limited amount of long-di stance aeolian transport within the Australian Continental Dunefield w ith most sand material apparently reworked from older fluvial and mari ne deposits.