Speleothems as palaeofire archives – a synthesis and meta-analysis of data and methods
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Date
2021-12-18
Journal Title
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Publisher
American Geophysical Union (AGU)
Abstract
Speleothems, mineral deposits found in caves, have recently been developed as a suitable archive to reconstruct palaeofires. Speleothems are excellent candidates for palaeoenvironmental research as they can be absolutely dated using radiometric methods and annual lamina, they incorporate a large range of chemical and physical proxies, and many are resolvable at the seasonal to annual scale. Large databases such as the Speleothem Isotope Synthesis and Analysis V2 may be used to identify and access suitable samples (Figure 1). Here, we present a meta-analysis and synthesis of published research and unpublished data to provide a toolbox for the use of speleothems as proxies of past fire. Drawing on our data from monitored caves and modern speleothems that overlap with recorded fire history, we will outline the approaches that we have adopted and identify which proxies have been validated as fire sensitive in the speleothem record. Fire sensitive proxies include ash-derived elements, in particular P and some transition metals, and proxies which reflect changes in soil productivity, hydrology, and evapotranspiration (e.g. δ18O, growth rate, organic matter, fabric). However, the success of these proxies as fire sensitive signals can differ between events recorded in speleothems. We discuss the complexities and demonstrate that an understanding of local surface-cave hydrological connectivity is required for the correct interpretation of the palaeofire signal. Improved understanding of palaeofire is necessary to characterize pre-industrial fire regimes, especially in colonised countries, where the landscape management systems of Indigenous people was disrupted. This will be of interest to the palaeoclimate community, land managers and traditional owners. Plain-language Summary
Stalagmites (natural formations found in caves) have been used to reconstruct past fire events. These formations are useful for reconstructing past environments because we can find out when they grew, how quickly they grew, and so any change in chemicals included in them can be used to describe the environment that they grew in. Here, we analysed published reconstructions of past fires and unpublished data, and demonstrate which methods are best for analysing stalagmites, and which chemicals (and combinations of chemicals) best indicate that a fire occurred. The chemicals included in stalagmites include some from the ash left after a fire (especially phosphorous), and some which can change due to changes in the soil and limestone over the cave (such as the ‘type’ of oxygen included in infiltrating rainwater). How these chemicals react to a fire changes between caves, and between fire events. We need to understand past fire patterns so that we can better manage the landscape. This is especially true in colonised countries where Indigenous land management was stopped by colonialism. This research will interest land managers, traditional owners, and other scientists who research past environments.
Description
Keywords
Caves, Minerals, Fires, Radiometric analysis, Data, Historical aspects, Hydrology, Paleoclimatology
Citation
Campbell, M., Treble, P. C., McDonough, L., Baker, A., & Kosarac, N. (2021). Speleothems as palaeofire archives – a synthesis and meta-analysis of data and methods. Poster presented at the AGU Fall Meeting 2021, New Orleans, Louisiana and Online, 13-17 December 2021. In AGU Fall Meeting Abstracts (Vol. 2021, PP55B-0648). Retrieved from: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/851613