Browsing by Author "Klaebe, RM"

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    Clumped isotope analysis of Central Australian carbonates: a potential palaeoclimate proxy for Australia’s arid interior
    (American Geophysical Union (AGU), 2022-12-13) Nixon, F; Tyler, JJ; Priestley, SC; Cohen, TJ; Klaebe, RM; Crossey, LJ; Karlstrom, KE; Polak, VJ; Asmerom, Y; Love, AJ; Hua, Q; Wade, B; Pollard, T; Drysdale, RN; Hall, PA
    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.
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    Clumped isotope analysis of central Australian carbonates: a potential palaeoclimate proxy for Australia’s arid interior
    (Australasian Quaternary Association Inc., 2022-12-06) Nixon, F; Tyler, JJ; Priestley, SC; Cohen, TJ; Klaebe, RM; Crossey, LJ; Karlstrom, KE; Polyak, VJ; Asmerom, Y; Love, A; Hua, Q; Wade, B; Pollard, T; Drysdale, RN; Hall, PA
    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.
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    Clumped isotope analysis of central Australian carbonates: a potential palaeoclimate proxy for Australia’s arid interior
    (Australasian Quaternary Association Inc., 2022-12-06) Nixon, F; Tyler, JJ; Priestley, SC; Cohen, TJ; Klaebe, RM; Crossey, L; Karlstrom, KE; Polyak, V; Asmerom, Y; Love, AJ; Hua, Q; Wade, B; Pollard, T; Drysdale, R; Hall, PA
    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.
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    A Holocene subtropical hydroclimate reconstruction from Karboora (Blue Lake), Minjerribah, Queensland
    (Australasian Quaternary Association, 2022-12-06) Maxson, C; Tibby, J; Tyler, JJ; Marshall, J; McGregor, G; Schulz, C; Jacobsen, GE; Klaebe, RM
    Holocene palaeoclimatology provides insights into the climate system, with particular relevance to the next century. This is especially true in sub-tropical Australia due to the under representation of the region in Holocene climate studies. Karboora (Blue Lake), on Minjerribah (North Stradbroke Island), Queensland, Australia is a groundwater window lake of major ecological and cultural significance. The lake’s strong connection with the regional aquifer underpins lake level stability, rendering Blue Lake sediments an ideal tracer of subtle changes in climate. Here, we report a new 5,500-year oxygen isotope record from biogenic (diatom) silica (δ18OBSi) that records variations in rainfall resulting from changes in Pacific atmospheric circulation. These interpretations are supported by modern monitoring over a 20 month period, including the δ18O of lake water, rain water, plant cellulose, and biogenic silica. We link rain δ18O to changes in El Niño Southern Oscillation (ENSO) phases, with phases showing distinct isotopic change that may be linked to tropical or extratropical sources of rainfall. On these grounds, we infer a dominance of extratropical rainfall from 5.5 kyr BP to 3.5 kyr BP, a period of transition from 3.5 kyr BP to 2.5 kyr BP dominated by neither tropical or extratropical rainfall, then a shift to tropically sourced rain from 2.5 kyr BP to the present. The early record (5.5 kyr BP – 3.5 kyr BP) most likely reflects a suppression of summer rainfall caused by a weakened ENSO. This is most likely linked to higher northern hemisphere insolation causing a northward shift in the intertropical convergence zone and westerly wind belt which in turn affected synoptic systems in the Coral and Tasman Seas. The increasing variability in the late record (3.5 kyr BP to present) most likely represents an increase in summer rainfall driven by the intensification of ENSO in the late Holocene.