Identification of a penultimate interglacial (marine isotope stage 7) alluvium in South Australia and its climatic and sea-level implications

Alluvial sequences proximal to coastlines offer opportunities to establish associations between terrestrial, sea-level and climatic events. South Australia hosts a globally significant Pleistocene interglacial sea-level record and numerous terrestrial sediment sources. However, only fragmentary evidence of pre-Last Interglacial alluvium has been identified. This paper presents the first definitive recognition of MIS 7 alluvium in South Australia, which occurs beneath the surface of extensive river terraces flanking Currency Creek and the Finniss River, between the Mount Lofty Ranges and the River Murray Lakes. A thermoluminescence age, 227 ± 24 ka, correlates with the penultimate interglacial global sea-level highstand. Nearby, last interglacial fossils of the estuarine bivalve Spisula trigonella at 2.53 ± 0.25 m APSL occupy a hollow eroded into the MIS 7 alluvium. Increasing aridity and decreased fluvial activity in the late Quaternary have preserved the MIS 7 alluvium. The fragmentary record of ...