Late Pleistocene evolution of Robe Range, southern Australia – The timing and carbonate source dynamics of coastal dune development
Robe Range is a coastal barrier that extends for over 155 km along the modern coastline of the Coorong Coastal Plain in southern Australia, a region renowned as preserving one of the world's longest records of Quaternary eolian dune deposition. Previous research has shown that the late Pleistocene dune development in this barrier structure is linked with sea-level highstands, particularly warm interstadials of marine isotope stage (MIS) 5. To better understand the principal depositional phases and sediment provenance of the dune successions of Robe Range, we use a combination of amino acid racemization analyses on the foraminifer Lamellodiscorbis dimidiatus and optically stimulated luminescence dating of associated quartz sand. The new and previously published optical dating results indicate that phases of dune formation correlate with MIS 5c–a (ca. 105–75 ka) and early in MIS 3 (ca. 61–53 ka). More importantly, the distribution of the extent of amino acid racemization on single-foraminifers reveals that the overall barrier successions have complex sources of carbonate sediment, principally derived from contemporaneous inner shelf temperate carbonate factories and reworked skeletal grains from the erosion of older marginal marine successions. The regional narrowing of the Bonney Shelf restricted the degree of lateral changes of the shoreline in response to the glacial–interglacial cycles, in contrast to the wider Lacepede Shelf to the north. The characteristics of offshore shelf topography allow wind-driven onshore transport and delivery of bioclastic sand from mixed-age carbonate sources to onshore coastal dunes during lower sea levels, particularly in association with the intensified wind regime of early MIS 3. This points to other factors influencing coastal dune emplacement besides simply glacio–eustatic sea-level changes, and relates to the availability of biogenic particles and the delicate balance between shelf topography and wind regimes during the interstadials of the late Pleistocene.
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University of Wollongong