Facies architecture of a last interglacial barrier: a model for Quaternary barrier development from the Coorong to Mount Gambier Coastal Plain, southeastern Australia

Abstract

The last interglacial Woakwine Range, a linear, barrier shoreline complex of temperate bioclastic carbonate origin, in the southeast of South Australia, occurs essentially uninterrupted over a distance of 300 km and up to 10 km inland from the present coastline. Mapping of the internal facies architecture of the barrier as revealed in McCourt's Cutting southeast of Robe, reveals the presence of transgressive and regressive facies associated with the last interglacial maximum (Oxygen Isotope Substage 5e), as well as an older aeolianite within the core of the barrier, correlated herein with Oxygen Isotope Stage 7. Amino acid racemisation and thermoluminescence dating indicate that volumetrically, the majority of the Woakwine Range is of last interglacial age. The bulk of the barrier structure comprises aeolian facies in the form of landward-migrating coastal dunes. The internal facies appear to record the culmination of the post-Stage 6 marine transgression at the onset of Substage 5e, and possibly the termination of Substage 5e based on the shallow seaward dip of the discontinuity between regressive littoral and sublittoral facies.