AMINOSTRATIGRAPHY AND ELECTRON-SPIN-RESONANCE DATING OF QUATERNARY COASTAL NEOTECTONISM IN TASMANIA AND THE BASS STRAIT ISLANDS

Tasmania and the Bass Strait islands (King and Flinders) preserve a wi despread but fragmentary Quaternary coastal record. Quaternary coastal sediments occur in a range of morphostratigraphic settings, typically contain well-preserved and diverse molluscan fossil assemblages of sh allow water origin, and provide evidence for varying degrees of neotec tonic uplift over contrasting temporal and spatial scales. Holocene an d Late Pleistocene (last interglacial) coastal strata occur most exten sively in this region, as revealed by amino acid racemization, electro n spin resonance and radiocarbon dating. Radiocarbon dates for marine molluscs from Holocene coastal strata range between 790 to 7120 a and relate specifically to the interval since the culmination of the post- glacial marine transgression. Holocene coastal sediments in this regio n do not provide convincing evidence for a higher sea level during the last 7000 years. The last interglacial coastal sediments in Tasmania represent the highest topographic occurrences of coastal strata of thi s age on the Australian continent (+11 to +32 m above present sea-leve l) and consistently occur above the defacto global 'eustatic' sea leve l datum of +6 m for oxygen isotope substage 5e. Thus, tectonic process es must be considered for their anomalously high elevation. In contras t, sediments of last interglacial age on King Island and Flinders Isla nd do not provide evidence for uplift. Neotectonic uplift is indicated , however, by the elevation of Early and Middle Pleistocene coastal st rata in this region. A southerly migration in the locus of neotectonic uplift is suggested, such that uplift occurred earlier in the Bass St rait islands than in Tasmania. The nature and precise timing of neotec tonic uplift remain unresolved.