Browsing by Author "Love, AJ"
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- ItemClumped 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, PAQuantitative 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.
- ItemClumped 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, PAQuantitative 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.
- ItemHydrochemical variations of groundwater and spring discharge of the western Great Artesian Basin(National Centre for Groundwater Research And Training, & Australian Chapter International Association Of Hydrogeologists, 2019-11-25) Priestley, SC; Shand, P; Love, AJ; Crossey, LJ; Karlstrom, KE; Keppel, MN; Wohling, DL; Rousseau-Guetin, PObjectives: The chemical variations of groundwater provide important clues to the geochemical processes responsible for water quality and evolution across the western GAB. The objective of this study was to examine the hydrochemical variations of groundwater and spring discharge along the entire western GAB expanding on several key results from a 4-year project studying the hydrochemistry of the western GAB presented in Love et al. (2013) and Love et al. (2013). Design and Methodology: The dataset comprises data collected during the Allocating Water and Maintaining Springs in the Great Artesian Basin project funded by the National Water Commission (Love, et al., 2013, Love, et al., 2013), with additional data from a government database, as well as, a number of published government reports and journal articles. Electrical balances and comparison of monitoring and duplicate data was undertaken to ensure the collated data were representative and accurate. Original data and results: The regional hydrochemical trends generally support the modern interpreted flow paths, indicating that these generally represent the long-term flow paths. However, the chemical variations along the flow paths in the western GAB are complex with their composition being a function of several controlling processes, including recharge location, evapotranspiration and water-rock interactions. These processes being spatially variable cause groundwaters to be generally of Na-HCO3 type east of Lake Eyre and Na-Cl-(-SO4) type when originating from the western margin. Springs within the western GAB springs appear to be discharging water predominantly from the main GAB aquifer. However, springs on the Peake and Denison Inlier are either completely or partially fractured rock source and there are several springs discharging water with a component from a source other than the main GAB aquifer. Conclusion: The source, evolution and several key geochemical processes responsible for water quality were identified through this study. However, work is still needed to fully characterise all water-rock interactions and geochemical processes occurring within the main GAB aquifer. © The Authors
- ItemReply to Comment on “Uranium series dating of Great Artesian Basin travertine deposits: Implications for palaeohydrogeology and palaeoclimate” by Uysal et al. (2019).(Elsevier, 2020-01-01) Priestley, SC; Karlstrom, KE; Love, AJ; Crossey, LJ; Polyak, VJ; Asmerom, Y; Meredith, KT; Crow, R; Keppel, MN; Habermehl, MATonguc Uysal and co-authors (this issue) propose that at least some of the U-series ages reported by Priestley et al. (2018) and Ring et al. (2016) provide minimum ages of movement at the Norwest Fault Zone in central Australia resulting from significant CO2 production due to mantle degassing related to active tectonics. We thank Tonguc Uysal and co-authors for their discussion on the role of tectonics and CO2 degassing in travertine precipitation and note that we had previously published (and agree with) the importance of mantle degassing as a source of CO2 that closely interacts with palaeohydrogeologic and palaeoclimatic forcings in explaining the rate and distribution of travertine deposition in the southwestern Great Artesian Basin (GAB) of central Australia. Based in part on western U.S. analogues (Crossey et al., 2016; Karlstrom et al., 2013a), we proposed and explored a model for these processes and their implications for the GAB in previous publications (Crossey et al., 2013; Karlstrom et al., 2013b) whereas Priestley et al. (2018) focused more specifically on palaeoclimate implications. Crown Copyright © 2019 Published by Elsevier B.V
- ItemUranium series dating of Great Artesian Basin travertine deposits: implications for palaeohydrogeology and palaeoclimate(Elsevier, 2018-01-15) Priestley, SC; Karlstrom, KE; Love, AJ; Crossey, LJ; Polyak, VJ; Asmerom, Y; Meredith, KT; Crow, R; Keppel, MN; Habermehl, MATravertine deposits precipitated by groundwater discharging from the Great Artesian Basin (GAB) are widespread in central Australia and have the potential to provide a record of palaeohydrogeology and palaeoclimate. The GAB is one of the largest artesian basins in the world and a relationship between travertine deposits and recharge sites has potential importance regarding the time and position of past climate events, given that the travertines growth forms from precipitation discharge. We sampled numerous travertine sites in the southwest section of the GAB as a first approach to test this relationship. U-series dating of the travertine deposits reveal that spring discharge has likely been episodic for the last several hundred thousand years. Spring travertine deposition occurred episodically around 465 ± 50 ka, 370 ± 20 ka, 335 ± 15 ka, 285–240 ka, 185 ± 10 ka, 160–150 ka, 110–100 ka and during the past 30 ka. The periodicity of travertine ages observed with simultaneous deposition at multiple locations, argues for regional palaeohydrologic controls. Comparison of the travertine deposit ages with climate proxies in Australia shows that elevated travertine deposition rates are synchronous with wet periods in both central and southern Australia. Due to the large size of the GAB and that the recharge zones extend over multiple climatic regions of Australia, the times of travertine deposition are interpreted to represent times of high rainfall regionally. This study shows that the travertine deposits of central Australia provide a datable archive of past climate and hydrogeology of importance for understanding the groundwater evolution of the Great Artesian Basin, and that further more comprehensive studies are warranted. © 2018 Elsevier B.V.
- ItemUse of U-isotopes in exploring groundwater flow and inter-aquifer leakage in the south-western margin of the Great Artesian Basin and Arckaringa Basin, central Australia(Elsevier, 2018-11) Priestley, SC; Payne, TE; Harrison, JJ; Post, VEA; Shand, P; Love, AJ; Wohling, DLThe distribution of uranium isotopes (238U and 234U) in groundwaters of the south-western margin of the Great Artesian Basin (GAB), Australia, and underlying Arckaringa Basin were examined using groundwater samples and a sequential extraction of aquifer sediments. Rock weathering, the geochemical environment and α-recoil of daughter products control the 238U and 234U isotope distributions giving rise to large spatial variations. Generally, the shallowest aquifer (J aquifer) contains groundwater with higher 238U activity concentrations and 234U/238U activity ratios close to secular equilibrium. However, the source input of uranium is spatially variable as intermittent recharge from ephemeral rivers passes through rocks that have already undergone extensive weathering and contain low 238U activity concentrations. Other locations in the J aquifer that receive little or no recharge contain higher 238U activity concentrations because uranium from localised uranium-rich rocks have been leached into solution and the geochemical environment allows the uranium to be kept in solution. The geochemical conditions of the deeper aquifers generally result in lower 238U activity concentrations in the groundwater accompanied by higher 234U/238U activity ratios. The sequential extraction of aquifer sediments showed that α-recoil of 234U from the solid mineral phases into the groundwater, rather than dissolution of, or exchange with the groundwater accessible minerals in the aquifer, caused enrichment of groundwater 234U/238U activity ratios in the Boorthanna Formation. Decay of 238U in uranium-rich coatings on J aquifer sediments caused resistant phase 234U/238U activity ratio enrichment. The groundwater 234U/238U activity ratio is dependent on groundwater residence time or flow rate, depending on the flow path trajectory. Thus, uranium isotope variations confirmed earlier groundwater flow interpretations based on other tracers; however, spatial heterogeneity, and the lack of clear regional correlations, made it difficult to identify recharge and inter-aquifer leakage. Crown Copyright © 2018 Published by Elsevier Ltd