The Simpson, Strzelecki and Tirari Deserts: Development and sand provenance

Sands of the Simpson, Strzelecki and Tirari Deserts, central Australia, can be divided into two main groups on the basis of their physical and chemical characteristics (colour, grainsize, heavy minerals, quartz oxygen-isotope composition, zircon U-Pb ages). The first group encompasses the Strzelecki, Tirari and southeastern Simpson Deserts, while the second occupies the northern and the western Simpson Desert. The boundary between the two groups corresponds approximately to the northern-most extent of the Kallakoopah Lakes. Several lines of evidence suggest derivation of the sands mainly from local bedrock, with very little subsequent aeolian transport. Ultimate protosources for the sands, in order of importance, are: of the southeastern Simpson, Tirari and Strzelecki Deserts - the Tasman Orogenic System (New England and Lachlan Fold Belts, Georgetown Inlier), Musgrave and Arunta Blocks, Gawler and Curnamona Cratons; and for the north and western Simpson Desert - Arunta, Musgrave and Mount Isa Blocks and Tennant Creek Inlier. Sediment from the Tasman Orogenic System includes an additional 'exotic' component from Palaeozoic sediments, probably derived mainly from Antarctica. Sediment transport from these protosources across the several hundred kilometres to the surficial sedimentary basins, was dominantly by fluvial, not aeolian, means. Quaternary aeolian transport or reworking has been minimal, serving only to form the dunes by vertical corrasion of underlying sedimentary rocks or residual products of local basement weathering. The deserts have received some recent localised sediment input from modern fluvial systems.