Age and origin of the Yilki Shore Platform, Encounter Bay, South Australia

Situated between Rosetta Head and the mouth of the Inman River on southern Fleurieu Peninsula, South Australia, the Yilki Shore Platform is a marine-abraded, seaward-sloping shore platform primarily developed on calcarenite. “Whole-rock” amino acid racemisation analyses reveal that the calcarenite is of Late Pleistocene age correlating with the Last Interglacial (MIS 5e; 132–115 ka), and the Upper Member of the Bridgewater Formation. The 200–280 m wide shore platform developed by the marine abrasion of either consolidated aeolian dune successions or a mixed assemblage of coastal beach-dune and back-barrier estuarine-lagoonal facies following the culmination of post-glacial sea-level rise some 8–7 ka ago. Solution pipes exposed on the platform surface have developed by syngenetic karst weathering processes. The raised rims of the tops of the bevelled solution pipes are substrates for colonies of the serpulid tube worm Galeolaria sp. The minor solution forms are unrelated to diagenetic features within the underlying Permian glacigene sediments, as originally suggested by Howchin in 1921.