Towards the development of fire proxies in speleothems using geochemical signatures in ashes from bushfires
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Date
2022-12-06
Journal Title
Journal ISSN
Volume Title
Publisher
Australasian Quaternary Association Inc.
Abstract
Our knowledge of past fire regimes is limited by short observational records. Proxy archives (such as sediment cores, ice cores, speleothems, and tree scars) are used to extend these records and develop a better understanding of past fire regimes. Recently, stalagmites (i.e., cave deposits), have been shown to record past fire events, and it is possible that they include other attributes of the fire regime (e.g. burn severity). Stalagmite fire proxies are both chemical (e.g. oxygen isotope composition of calcite, and nutrient and trace metal concentrations), and physical (e.g. growth rate, fabric). Trace metals and nutrients are leached from ash and subsequently transported to the stalagmite via hydrological pathways. We collected ash from four Australian karst sites which experienced fires in recent years (2019 and 2022). Ash chemical composition was determined by analysis of leachates (inorganic chemistry) and by analysis of the ash itself (organic biomarker concentrations of a subset of the ash dataset). The concentrations of inorganic components (e.g. of trace metals strontium and magnesium) show a clear difference between more- and less-combusted materials, as inferred by ash colour. Common fire biomarker concentrations (e.g. polycyclic aromatic hydrocarbons and levoglucosan) showed no clear relationship with inferred burn severity. Together, this has implications for the use of both organic and inorganic fire proxies in stalagmites and other sedimentary proxy archives. Inorganic ash geochemistry results will be used to contextualise changes in stalagmite geochemistry from Western Australian stalagmites (as measured by LA-ICP-MS and Synchrotron micro-XFM) which experienced bushfires during the satellite era. We aim to determine whether stalagmite chemistry can be used as a proxy for burn severity.
Description
Keywords
Fires, Caves, Records management, Sediments, Drill cores, Trees, Geologic deposits, Oxygen isotopes, Ashes, Australia, Metals
Citation
Campbell, M., McDonough, L., Naeher, S., Treble, P., Grierson, P, Sinclair, D., Howard, D., & Baker, A. (2022). Towards the development of fire proxies in speleothems using geochemical signatures in ashes from bushfires. Paper presented to AQUA 2022 Conference, 6-8 December 2022, Adelaide,. In Aqua program and abstract booklet, Adelaide 2022, (pp. 31-32). Retrieved from: http://aqua.org.au/wp-content/uploads/2022/11/AQUA-2022-conference-program-and-abstract-booklet.pdf