Clumped isotope analysis of central Australian carbonates: a potential palaeoclimate proxy for Australia’s arid interior
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Date
2022-12-06
Journal Title
Journal ISSN
Volume Title
Publisher
Australasian Quaternary Association Inc.
Abstract
Quantitative records of past temperature variability in arid environments are crucial for validating climate models and their ability to capture the full range of the Earth’s climatic regions. However, arid zone temperature reconstructions are rare, particularly in the Southern Hemisphere, including Australia. The clumped isotope thermometer provides a novel approach to potentially address this demand by allowing the estimation of carbonate precipitation temperature independent of environmental water isotopic composition. Two types of carbonate materials offer potential for clumped isotope temperature reconstructions in arid central Australia: fossil mollusk shells deposited within the shoreline sediments of now dry lakes, and tufa deposits formed in mound springs fed by continuous discharge of Great Artesian Basin groundwater. Here we present preliminary clumped isotope analyses from tufa and shell samples from central Australia. We also discuss the use of micro-XRF scanning and XRD to evaluate sample suitability for both clumped isotope analysis and U-series dating. Air temperatures inferred from tufa Δ47 measurements suggest mean annual air temperatures (MAAT) ~5°C cooler than present between 12-9 ka, which supports palaeoclimate model based estimates for central Australia. Average air temperatures inferred from mollusk shells indicate MAAT at least 15°C cooler than present during 70-35 ka, suggesting a larger MAAT reduction than previously estimated. Carbonate δ18O appears to have been largely driven by changes in environmental water δ18O for lakes but not for mound springs, reflecting different hydrological controls on the two water sources. Agreement between temperatures and palaeoclimate models suggest clumped isotope analysis may function as a valuable quantitative palaeotemperature proxy in central Australia. Analysis of additional tufa and shell samples along with an investigation of the genesis of different tufa is ongoing.
Description
Keywords
Isotopes, Australia, Carbonates, Climates, Climate models, Australia, Thermometers, Fossils, Ground water
Citation
Nixon, F., Tyler, J., Priestley, S., Cohen, T., Klaebe, R., Crossey, L., Karlstrom, K., Polyak, V., Asmerom, Y., Love, A., Hua, Q., Wade, B., Pollard, T., Dyrsdale, R., & Hall, P. A. (2022). Clumped isotope analysis of central Australian carbonates: a potential palaeoclimate proxy for Australia’s arid interior. Paper presented to AQUA 2022 Conference, 6-8 December 2022, Adelaide. (pp. 157-158). Retrieved from: http://aqua.org.au/wp-content/uploads/2022/11/AQUA-2022-conference-program-and-abstract-booklet.pdf