Aminostratigraphy of Quaternary coastal sequences in southern Australia — An overview

Abstract

Since the early 1980s, amino acid racemisation reactions have been applied to the dating of Quaternary coastal deposits in Australia. Sequences of Middle Pleistocene age or younger have received the greatest attention. Amino acid racemisation has been applied as a relative and numeric dating method, as well as for identifying remanie fossils and in delineating the spatial distribution of some fossil mollusc species. The method has also been used to verify the radiocarbon ages of fossil molluscs from interstadial sediments. It has also been used in studies of coastal neotectonics and in comparisons with other dating methods (e.g. electron spin resonance and thermoluminescence). The most reliable results are from replicate analyses of the hinge region of well-preserved and diagenetically unmodified fossil bivalve molluscs from deeply buried situations (i.e. > 1 m). Molluscs have been dated from a range of sites around the southern Australian coastline and include specimens of Plio-Pleistocene age, and from Middle Pleistocene (Oxygen Isotope Stage 7; ca. 220 ka BP), Late Pleistocene (Substage 5e; ca. 125 ka BP), interstadial (Stage 3; 45 to 30 ka BP), last glacial (Stage 2; ca. 18 ka BP) and Holocene sequences. Amino acid racemisation dating of the Australian Quaternary coastal record has: (1) confirmed the widespread occurrence of last interglacial coastal strata and allowed their correlation with sequences of equivalent age from the northern hemisphere; (2) identified strata of penultimate interglacial age; and (3) confirmed the interstadial age of marine strata (Stage 3) in Gulf St Vincent, South Australia. Aminostratigraphic studies of the southern Australian Quaternary coastal record also indicate that sea-levels during the penultimate interglacial (Stage 7) may have been higher than otherwise predicted on the basis of the oxygen isotope record.