Last Glacial pluvial periods evident in subaqueous speleothems from Australia’s southern arid-margin

Archives from Kati Thanda (Lake Eyre) basin indicate at least three distinct periods of lake filling during the Last Glacial Period. The headwaters of the megalake lie as far north as -19 °, therefore filling events are indicative of increased intensity of the Indo-Australian Summer Monsoon (IASM). However, due to the nature of unconsolidated materials, these archives are limited in how precisely they can constrain the timing of Last Glacial pluvial periods, and they cannot capture millennial-scale climate variability. Speleothems from Mairs Cave (Flinders Ranges, South Australia), present an opportunity to address these issues. The cave lies on the boundary between the arid and semi-arid regions and currently receives rainfall from both the Southern Hemisphere Westerly Winds (SHWW) and the IASM. The cave contains pendulites: stalactites with an external overgrowth of subaqueously precipitated calcite. The stalactites were initially submerged ~ 89 ka by rising groundwaters, which flooded the cave. From that point forward, the pendulites grew subaqueously during periods of regional groundwater recharge. Preliminary findings suggest periods of subaqueous growth align with higher Southern Hemisphere summer insolation, suggesting the site received enhanced tropical rainfall due to moisture delivery from the IASM. Growth rate and magnesium concentrations both appear to be responsive to millennial-scale climate change, exhibiting increases during both Heinrich events and the cold limbs of Dansgaard-Oeschger events. This is consistent with increased delivery of tropical moisture due to southerly incursions of the IASM. The study site lies near the intersection of two ‘superhighways’ of early human expansion proposed by Crabtree et al. (2021). The cave is also 200 km directly south of the Warratyi shelter, one of the earliest sites of human occupation in southern-central Australia. Therefore, the palaeoclimate record to emerge from this research could potentially provide a more detailed climatic contextualisation for this period of human history.

Keywords

Australia, Lakes, Materials, Climates, Caves, Calcite, Ground water, Magnesium

Citation

Gould-Whaley, C., Drysdale, R., May, J., Hellstrom, J., Treble, P., Grieg, A., Cheng, H., & Buswell, C. (2022). Last Glacial pluvial periods evident in subaqueous speleothems from Australia’s southern arid-margin. Paper presented to the AQUA 2022 Conference, 6-8th December, Adelaide (pp. 51-52). Retrieved from: https://aqua.org.au/conference/aqua-2022/aqua-2022-conference-program-and-abstracts/

URI

https://aqua.org.au/conference/aqua-2022/aqua-2022-conference-program-and-abstracts/
https://apo.ansto.gov.au/dspace/handle/10238/14763

Collections

Conference Publications

Full item page