An evaluation of Australia as a major source of dust

Abstract

Since Australia is the driest inhabited continent, it is a natural laboratory to study on a large scale dust, its composition, its sources, transport and geochemical composition. This is necessary as there has been a lack of appreciation of the diversity of the Australian regolith characterized by a great array of ages and compositions. This is particularly true of studies that examined the geochemistry of Australian dusts and links with potential deposition sites such as in Antarctica and comparison with South America. Hence, the first part of this paper provides an overview of the surficial geology of Australia with emphasis on regions from where dust can become deflated. A review follows on the investigations of significant dust transport and events in Australia.

The second part of the paper provides a review of the sites of potential deflation of dust. It includes the study of different geomorphological sites of dust deflation, with a discussion on how dust particles can accumulate in regions linked to large playa lakes that are under the influence of groundwater below them. This is an important mode of dust deflation, a process of which had insufficiently been detailed before. The processes involving evaporative pumping are explained and several illustrations are provided to document those processes and location of dust deposits. Another region of importance to dust deflation consists of extensive alluvial plains and these are also documented, with an area in the upper reaches of the Darling River being now documented more fully. Finally, the inter-dunal corridors in large dune fields are also mentioned as a source of dust as previous studies already show. This second part ends with the description of the two main Potential Source Areas (PSA) of dust in Australia and these are the Kati Thanda-Lake Eyre region of central Australia, and the Darling Riverine Plain in the upper reaches of the Darling River. These two regions are important for their geochemical fingerprints for transcontinental studies, and supported by satellite imagery that identify dust plumes originating from these regions.

The third part of the paper examines the geochemical composition of Australian PSAs by paying particular attention to Neodymium, Strontium and Lead isotopic ratios from both continents. We also suggest the possibility of combining Nd and Pb isotopes as a way of fingerprinting geochemically between different Australian regions, and for comparison with other continental PSAs. This part also reviews previous studies that aimed at geochemically fingerprinting the Australian regolith by referring also how these studies were applied to reconstruct past environmental conditions.