Polycyclic Aromatic Hydrocarbons in tropical Australian stalagmites: a framework for reconstructing paleofire activity - Research data

We investigate the possibility to use polycyclic aromatic hydrocarbons in stalagmites as proxies for paleofires at KNI-51, a shallow cave located in tropical Western Australia, where bushfire is a regular occurrence. In order to test links between the stalagmite PAHs and fire above the cave, we performed a series of experiments using PAH distributions in stalagmite aragonite, sediment from the cave and overlying soil. In addition, the possibility of surface contamination was evaluated by measuring PAH abundances and distributions in sequential digestions. PAHs were measured in soils above the cave, in sediments from the stalagmite chamber floor as possible sources of these organic compounds, and at near annual resolution in three aragonite stalagmites to evaluate the degree of deposition and conservation. Signal replication of PAHs was also tested in two coeval stalagmites. The results support the hypothesis that PAHs in KNI-51 stalagmite carbonate reflect paleofire activity within 3 km of the cave, and thus that stalagmites can serve as an important new high resolution proxy for landscape-scale fire activity. Given that karst is present in many fire-prone environments, and that stalagmites can be precisely dated and may grow continuously for millennia, the potential utility of a stalagmite-based paleofire proxy is high.