Reconstructing the late Pleistocene climate sequence at Alexandra Cave, Naracoorte, using trapped charge dating and palaeoenvironmental proxies

The drivers of Australia-wide megafaunal extinction during the late Pleistocene remain poorly resolved. Hypotheses include individual or synergistic combinations of climate fluctuations, human impacts through hunting or habitat alteration by landscape burning. Moreover, the relationship between extinction dynamics and long term glacial - interglacial environmental change is not yet understood. Using a series of complementary geochronological, palaeoecological and geochemical techniques on a sedimentary sequence in Alexandra Cave, Naracoorte, this study provides improved reconstructions of past climates in south-east South Australia prior to, and around the time of, megafaunal extinction. Optically stimulated luminescence and electron spin resonance dating constrain the age of the sedimentary sequence to Marine Isotope Stage (MIS) 1 – 5. Preliminary environmental reconstructions undertaken using carbon isotopes of charcoal and Itrax micro X-ray fluorescence analysis reveal high precipitation during late MIS 5, while MIS 4 was arid. Decreased organic matter and increased sedimentation rates in mid-late MIS 3 suggest a change in landscape conditions, consistent with an environmental shift around the time of megafaunal demise locally. The Last Glacial maximum was arid, with frequent local fires, followed by a shift during the Holocene, marked by an increase in precipitation.

Keywords

Luminescence, Age estimation, Electron spin resonance, Charcoal, Isotopes, South Australia, Climatic change, Humans, Environment, Habitat, Plants, Glaciers, Quaternary period

Citation

Priya, L. J., Arnold, M. D., Guilarte, V., Cohen, T., Tyler, J., Demuro, M., Gadd, P., & Reed, E. H. (2021). Reconstructing the late Pleistocene climate sequence at Alexandra Cave, Naracoorte, using trapped charge dating and palaeoenvironmental proxies. Paper presented to the Australasian Quaternary Association/Friends of the Pleistocene Pop-up Conference 2021, 8-9th July 2021. Retrieved from: http://aqua.org.au/wp-content/uploads/2021/07/Abstract-book-2021-1.pdf