3Faculty of Engineering and the Environment, University of South Australia, Mawson Lakes, SA, 5095, Australia.

Southern Australia preserves a rich assemblage of coastal landforms and sedimentary successions of last interglacial age (Oxygen Isotope Substage 5e). The sedimentary facies have many features in common with adjacent Holocene coastal facies and contemporary peritidal environments, but are partly lithified, mostly elevated and laterally displaced inland. Sediments are dominantly biogenic skeletal carbonates of cool-temperate water affinities (foram-mollusc-coralline algal association). Surficial calcrete development has aided preservation of morphostratigraphic forms and sedimentary structures.

Large coastal barrier complexes comprising aeolian, foredune and back-dune lagoon facies characterize exposed coastal tracts facing the Southern Ocean. In contrast, broad, low-gradient peritidal complexes, with a shoaling-upward sequence of subtidal, intertidal and supratidal mud/sand flat facies, characterize protected shorelines of major gulfs and embayments. A similar upward-shoaling sequence is preserved in back-barrier lagoons.

Differential shoreline elevations of last interglacial, intertidal facies reveal subtle differences spatially, that largely relate to tectonic setting. Along the more tectonically stable parts of southern Australia such as Eyre Peninsula (Gawler Craton), the last interglacial shoreline is consistently recorded at 2 m above present sea level (APSL) for over 500 km. This is an important regional datum that is significantly below the +6 m level globally attributed to this sea level highstand. Elsewhere, neotectonic variations in shoreline elevation are clearly discernible. In Gulf St. Vincent, the last interglacial Glanville Formation does not crop out in the Adelaide region, reflecting ongoing subsidence by up to ca. 11 m, but at Normanville, southern Fleurieu Peninsula, it occurs up to 12 m APSL. The Murray River mouth area indicates subsidence and the Coorong Coastal Plain reveals a gradual rise in the elevation of the last interglacial shoreline from near present sea level in the northern Coorong Lagoon to18 m APSL near Mount Gambier, the latter associated with Quaternary volcansim.

The last interglacial strata contain a number of distinctive fossils of subtropical affinity that no longer live in the local waters and include the estuarine, arcoid bivalve Anadara trapezia, the Shark Bay pearl oyster Pinctada carchariarium, and the conical-fusiform gastropod Euplica bidentata. Benthic foraminifers of similar affinity include the megascopic foraminifer Marginopora vertebralis, Pseudomassilina australis and Quinqueloculina polygona. These species appear to be associated with an enhanced Leeuwin Current coinciding with higher, less seasonally concentrated levels of precipitation and river discharge during the last interglacial maximum. Collectively, the evidence suggests that for much of southern Australia, the last interglacial maximum (Oxygen Isotope Substage 5e) was wetter than the present, Holocene interglacial.