Applications of clumped-isotope palaeothermometry

Standard palaeotemperature equations, used to interpret the formation conditions of carbonate materials, are generally problematic. This is due to the need to know both the δ18O value of the water and the precipitated carbonate to complete the equation. The clumped-isotope method overcomes these uncertainties by examining the affinity of heavy isotopes bonding (13C18O16O = 47CO2) in favour of bonding to lighter isotopes (12C16O16O = 44CO2) in evolved CO2 from carbonates. This process of “clumping” is sensitive to ambient temperature, so can be used to determine palaeotemperature, but is independent of bulk isotopic composition of the original water. Measured values (Δ47) are expressed as per mil variation of the relative abundance of an isotopologue compared to the theoretical predicted relative abundance based on a stochastic random distribution. This study reports the first set of clumped-isotope results from the University of Wollongong laboratory. Improvements were made to previously developed analytical systems to more accurately and precisely determine carbonate formation temperatures. This study has indicated that the cold-water carbonate glendonite and equilibrium precipitated cave deposits have the potential to be utilised as reliable clumped isotope palaeotemperature proxies. Further improvements in the clumped isotope method are needed to more accurately investigate both of these types of material as well to resolve the origin of discrepancies in the mollusc clumpedisotope results.