|Speleothems from Yonderup Cave system Photo: WA Department Environment and Conservation|
The Smithsonian Magazine has featured the cave deposit research of a collaboration including ANSTO isotope paleoclimatologist Pauline Treble in a recent issue. The lead author of the article is AINSE honours scholarship recipient Gurinder Nagra, a student at the University of New South Wales (UNSW) Australia, who analysed how bushfires might affect drip water chemistry in caves.
The research, which involved contributions from Treble, Andy Baker, Martin Andersen and Katie Coleborn from UNSW and Ian Fairchild from the University of Birmingham (UK), is currently under review for publication in Hydrology and Earth System Sciences.
The research came about after Treble had travelled to shallow cave system in Western Australia (WA) to extract the cave’s rainfall information from speleothems (stalagmites and stalacites) but encountered an unexplained lack of rainfall signal. The geochemical composition of speleothems can be used to interpret past climate information.
To resolve the issue, Treble turned the project over to Nagra to determine how fires affect the land they burn and how those effects drip into caves.
An intense bushfire occurred at the Yonderup Cave in Yanchep National Park, south of Perth WA in February 2005. An analysis of drip water collected between August 2005 and March 2011 at Yonderup was compared with regional groundwater chemistry and dripwater data from another cave in southwest Australia.
The results of the research suggest that local conditions, such as bushfires, can affect the isotopic signal of the oxygen and could be misinterpreted as past climate variability. The unique fire signature of isotopes of oxygen, sulfur and chlorine in speleothems, combined with magnesium and strontium, might open a new avenue for paleo fire records.