Role of eolian dust deposits in landscape development and soil degradation in southeastern Australia

Abstract

Eolian dust plays a significant role in landscape development and landscape processes in Australia. Thin dust mantles, rarely exceeding 3 m in thickness, have been identified across many parts of the Australian landscape, particularly in southeastern Australia. The nature and properties of these dust materials can have a major influence on environmental degradation processes such as salinisation and soil erosion. Despite the existing body of research regarding this topic, there are still conflicting views about the likely sources, transport modes and properties of eolian dust in the Australian landscape. The aim of this review is to synthesise much of the available information and put forward a working hypothesis for the distribution and fundamental properties of dust deposits in southeastern Australia. A conceptual model describing the various dust sources and sinks, and the modes of transport of dust materials both into and out of these source areas, is introduced. The model identifies key source areas, such as the alluvial and lacustrine environments of the Lake Eyre and Murray-Darling Basins, and sinks, such as the Eastern Highlands. Transport rates and paths for eolian-dust materials across the Australian continent are also outlined. The model places particular emphasis on the recycling of dust, whereby sediments sourced from the Eastern Highlands are transported westward via the major alluvial networks, and deposited on floodplains or in terminal drainage systems. These sediments are then available to be reworked into local eolian landforms prior to re-entrainment of the finer materials in the easterly dust pathway. The characteristics of deposited eolian sediments are then outlined in detail, focusing particularly on their particle-size distribution, mineralogical composition, and geophysical and geochemical properties. The review also presents data and images of dust materials sampled from source areas, sink areas, as well as materials that have been deposited by modern dust events. Finally, the role of dust materials in land-degradation processes, particularly soil erosion, is discussed. The degree of reworking of the eolian sediments, the extent of leaching and the level of sodicity are all important in determining soil structural stability and hence erosion potential of these materials.