Reconstructing a fire and climate history using a stalagmite from Crystal Cave, south-west Western Australia

Bushfires are a major natural hazard, with a growing impact on communities and ecosystems in Australia and worldwide. However, our understanding of long-term past fire intervals and behaviour is limited by low temporal resolution. Cave stalagmites offer a novel opportunity to reconstruct long, high-resolution datasets of past fire and climate with a precise chronology. CRY-S1 is a cave stalagmite from Crystal Cave, Margaret River, south-west Western Australia. Monitoring has shown that speleothems from shallow caves are more likely to record fire events as pulses of ash-derived elements and evaporative enrichment of δ18O. However, Crystal Cave is located approximately 30 m below the surface, indicating that past fire events can also be recorded in a deep cave system. This may be on account of the cave’s fracture flow contribution enabling a more direct connection with the surface, or the catchment morphology. This Honours project aims to compile and analyse fire and climate data over 300 years using new and existing datasets for stalagmite CRY-S1. We assess 18O and 13C isotope data, as well as a suite of trace elements. Past studies have determined that fire events can be identified through ash-derived elements in stalagmite laminae. Elements of interest include phosphorous, strontium and zinc. Results from 14C analyses will be used to test a hypothesis that large fires will eliminate young carbon in soils, altering the stalagmite 14C/12C ratio. An age depth model was obtained using annual lamina counts from Sr synchrotron mapping. Studying trace elements and isotope signals in this context increases our understanding of how past fire and climatic changes can be interpreted through stalagmite geochemistry. This Honours project will contribute to a world first project which uses stalagmites to construct annually-resolved records of fire frequency and intensity.

Keywords

Caves, Fires, Trace elements, Environment, Australia, Ecosystems

Citation

Kosarac, N., Treble, P., McDonough, L., Paterson, D., Adler, L., & Baker, A. (2021). Reconstructing a fire and climate history using a stalagmite from Crystal Cave, south-west Western Australia. 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

URI

http://aqua.org.au/wp-content/uploads/2021/07/Abstract-book-2021-1.pdf
https://apo.ansto.gov.au/handle/10238/15081

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