Sulphur: a proxy for wildfires in stalagmites

Bushfires are a global hazard that can have catastrophic impacts on communities and ecosystems. However, there is limited baseline data on how fire frequency and intensity have responded to climate change in the past. A speleothem-based bushfire record will allow us to determine long-term natural fire regimes and better understand the relationship between bushfires and climate. Recent research has demonstrated the potential of using sulphur as a speleothem paleofire proxy1 but a full characterisation of S in the karst environments of SW Western Australia is lacking. Here, we quantify the relative contributions of different sources of sulphur in a modern cave environment through the characterisation of rainfall, soil, bedrock, vegetation and cave drip water sulphate concentration and isotopic values (δ18O- SO4 and δ34S- SO4) to assess the role of sulphur cycling through the biomass in response to burn events at this site. This information will be used to interpret the SO4 isotope record, supported by other proxies in a 2-12 ka speleothem from SW Western Australia. This is the first speleothem SO4 isotope study in the southern hemisphere and the first in the world to use speleothem S isotopes in a paleofire context. © Author(s