Reconstructing timeframes, processes and environmental implications of Late Quaternary aeolian Parna deposition in south-eastern Australia

Abstract

Sedimentary sequences with major aeolian dust contribution blanket the flat to hilly landscapes of eastern New South Wales. Originally identified by Butler in 1956 within the Riverine Plain and adjoining hills, these widespread clay-rich sediments were termed "Parna”. Parna – which has often been compared to loess – is thought to be fine-grained sediment generated through exogenic processes in arid environments and transported as stable aggregates by prevailing westerly winds during the Quaternary. The primary hypothesized source regions for Parna are arid and semi-arid river and lake systems situated in the western Murray-Darling Basin. Despite the prolonged critical discourse surrounding the concept and terminology of Parna, investigations addressing unresolved questions have been limited, with absolute dating of the aeolian sequences being restricted to only a few sites. Given the complexity of the Parna sequences resulting from the interaction of aeolian, hillslope and pedological processes, we choose a multimethodological approach combining field observations, grain size analysis, geochronological and geochemical methods to investigate the processes and time frames of sedimentation and sediment provenance. Results of optically stimulated luminescence (OSL) dating for several Parna sites in the Wagga Wagga (Beattie 1972) and Yass region, show age estimates reaching back 150,000 years. Sedimentological parameters are used to distinguish between material derived from local hillslope and aeolian input. Geochemical characteristics will help to trace sources and pathways of the aeolian material. Advancing our understanding of the Parna concept, implying large-scale deposition but also deflation of aeolian material, is one component of reconstructing Quaternary landscape development and environmental conditions in south-eastern Australia. Butler, B.E., 1956. Parna-an aeolian clay. Australian Journal of Science, 18(5), 145-151. Beattie, J.A., 1972. Groundsurfaces of the Wagga Wagga Region, New South Wales. C.S.I.R.O Soil. Pub Australia. No. 28.