Browsing by Author "Priestley, SC"
Now showing 1 - 19 of 19
Results Per Page
Sort Options
- ItemA 35 ka record of groundwater recharge in south-west Australia using stable water isotopes(Elsevier B. V., 2020-05-15) Priestley, SC; Meredith, KT; Treble, PC; Cendón, DI; Griffiths, AD; Hollins, SE; Baker, AA; Pigois, JPThe isotopic composition of groundwater can be a useful indicator of recharge conditions and may be used as an archive to infer past climate variability. Groundwater from two largely confined aquifers in south-west Australia, recharged at the northernmost extent of the westerly wind belt, can help constrain the palaeoclimate record in this region. We demonstrate that radiocarbon age measurements of dissolved inorganic carbon are appropriate for dating groundwater from the Leederville aquifer and Yarragadee aquifer within the Perth Basin. Variations in groundwater δ18O values with mean residence time were examined using regional and flow line data sets, which were compared. The trends in the regional groundwater data are consistent with the groundwater flow line data supporting the hypothesis that groundwater δ18O is a robust proxy for palaeo-recharge in the Perth Basin. A comparison between modern groundwater and rainfall water isotopes indicates that recharge is biased to months with high volume and/or intense rainfall from the westerly wind circulation and that this has been the case for the last 35 ka. Lower stable water isotope values are interpreted to represent recharge from higher volume and/or more intense rainfall from 35 ka through the Last Glacial Maximum period although potentially modulated by changes in recharge thresholds. The Southern Perth Basin groundwater isotopic record also indicates a trend towards higher volume and/or intense rainfall during the Mid- to Late Holocene. The long-term stable water isotope record provides an understanding of groundwater palaeo-recharge. Knowledge of recharge dynamics over long time scales can be used to improve current water sharing plans and future groundwater model predictions. © Crown Copyright 2019
- ItemA 35 ka record of groundwater recharge using stable water isotopes for Perth Basin in south-west Australia(National Centre for Groundwater Research And Training, & Australian Chapter International Association Of Hydrogeologists, 2019-11-25) Priestley, SC; Meredith, KT; Treble, PC; Cendón, DI; Griffiths, AD; Hollins, SE; Baker, AA; Pigois, JPObjectives: As most large groundwater basins can contain ‘old’ groundwater where extraction exceeds groundwater recharge, knowledge of the past conditions and timing under which groundwater was recharged is needed to sustainably manage groundwater resources. Moreover, the isotopic composition of groundwater can be a useful indicator of rainfall isotope compositions and help to determine the drivers and impacts of rainfall and climate change. Applying isotopic tools to groundwater contained in regional aquifer systems can provide low-resolution information on recharge intensity, recharge source and past climatic conditions for the region. Design and Methodology: A dataset containing groundwater ages (14CDIC) and stable isotopes of water (δ18O and δ2H) from two regional groundwater systems within the Perth Basin, the Leederville Formation and Yarragadee Formation, were compiled to create a low-resolution palaeo-archive of groundwater recharge. Original data and results: The trends in stable isotopes of water over time in the regional groundwater data are consistent with groundwater flow line data supporting our hypothesis that groundwater stable isotopes are a proxy for palaeo-recharge. A comparison between modern groundwater and rainfall water isotopes indicates that recharge is biased to months with high volume and/or intense rainfall from the westerly wind circulation and that this has been the case for the last 35 ka. Lower stable water isotope values are interpreted to represent recharge from higher volume and/or more intense rainfall from 35 ka through the Last Glacial Maximum period although potentially modulated by changes in recharge thresholds. Conclusion: The groundwater isotope record is interpreted to be a low-resolution archive of recharge driven by changes in the relative intensity of past rainfall and recharge thresholds. This long-term stable isotopic recharge record provides a greater understanding of groundwater palaeo-recharge, and the connection between recharge and climate in the past. © The Authors
- ItemCaves demonstrate decrease in rainfall recharge of southwest Australian groundwater is unprecedented for the last 800 years(Springer Nature, 2023-06-09) Priestley, SC; Treble, PC; Griffiths, AD; Baker, AA; Abram, NJ; Meredith, KTBillions of people worldwide rely on groundwater. As rainfall in many regions in the future is projected to decrease, it is critical to understand the impacts of climate change on groundwater recharge. The groundwater recharge response to a sustained decrease in rainfall across southwest Australia that began in the late 1960s was examined in seven modern speleothems and drip waters from four caves. These show a pronounced increase or uptick in regional drip water and speleothem oxygen isotopic composition (δ18O) that is not driven by a change in rainfall δ18O values, but is in response to the shallow karst aquifers becoming disconnected from rainfall recharge due to regional drying. Our findings imply that rainfall recharge to groundwater may no longer be reliably occurring in this region, which is highly dependent on groundwater resources. Examination of the longer speleothem record shows that this situation is unprecedented over the last 800 years. © The Authors - Open Access licensed under a Creative Commons Attribution 4.0 International Licence.
- ItemCaves provide early warning of unprecedented decrease in rainfall recharge of groundwater(Research Square, 2022-05-02) Priestley, SC; Treble, PC; Griffiths, AD; Baker, AA; Abram, NJ; Meredith, KTBillions of people worldwide rely on groundwater. As rainfall in many regions in the future is projected to decrease, it is critical to understand the impacts of climate change on groundwater recharge. In this study, five caves record a consistent response to a sustained decrease in rainfall across southwest Australia that began in the late 1960s, characterised by a pronounced increase or ’uptick’ in dripwater and speleothem oxygen isotopic composition (δ18O). It is demonstrated that the uptick is in response to the shallow karst aquifers becoming disconnected from recharge due to regional drying. Our findings imply that rainfall recharge to groundwater across this region is no longer reliably occurring. Examination of the longer speleothem record shows that this is unprecedented over at least the last 800 years. A global network of cave dripwater monitoring would serve as an early warning of reduced groundwater recharge elsewhere, while evidence for upticks in speleothem paleoclimate records would provide a longer-term context to evaluate if current groundwater recharge changes are outside the range of natural variability. This study also validates speleothems as recorders of past hydroclimate via amplification of the δ18O signal by karst hydrology highlighting that speleothem δ18O are records of recharge, rather than a direct proxy for rainfall. © 2022 The Authors
- 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, LJ; Karlstrom, KE; Polyak, VJ; Asmerom, Y; Love, A; 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(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.
- ItemComparison of δ18O in groundwater and a cave flowstone: improving the interpretation of the speleothem δ18O paleoclimate proxy(International Union for Quaternary Research (INQUA), 2019-07-30) Adler, L; Priestley, SC; Treble, PC; Baker, AA; Hellstrom, JC; Griffiths, AD; Meredith, KTSpeleothems are high-resolution records that can be used for terrestrial paleoclimate reconstruction from their oxygen and carbon isotopes (δ18O and δ13C), and whose deposition is directly related to the groundwater recharge process. Groundwater δ18O records have the potential to provide an important long-term record of past climate, but they are low-resolution records as the isotope signal can be altered during flow within the aquifer. In this study we compare measured δ18O values from both a groundwater record and speleothem record from a flowstone over the past 12,000 years for the first time from south west Western Australia. Flowstones normally form from cave streams or fast dripping seepages and their oxygen isotope composition is sensitive to the extent of kinetic fractionation, determined by water flow rate, as well as, streams or seepages water δ18O composition. In this study comparison of δ18O values from a groundwater record and flowstone enables the source water oxygen isotopic composition to be constrained in order for a more complete interpretation of the higher resolution speleothem record, including the site specific kinetic processes and climatic changes. The flowstone δ18O values appear consistent with millennial variability in recharge δ18O predicted using the groundwater values, although the flowstone oxygen isotopes are generally enriched in 18O compared to the regional groundwater record before ~7.4ka. This offset between the records indicates that flowstone calcite deposition was not in isotopic equilibrium with its source water likely due to low flow regimes and extensive degassing of CO2. According to a model of isotopic disequilibrium that is driven by water supply, the Holocene portion of the flowstone record contains periods of relatively lower isotopic disequilibrium indicating possible higher water supply, and periods of relatively higher isotopic disequilibrium indicating possible lower water supply consistent with local and regional archives.
- ItemEmbracing the karst hydrological control on speleothem oxygen isotope variability(European Geosciences Union (EGU), 2023-04-27) Treble, PC; Baker, AA; Priestley, SC; Griffiths, ADThe influence of karst hydrology or ‘flowpaths’ on speleothem oxygen isotopic (δ18O) values has been simulated using karst forward models. Cave monitoring studies have also shown that variability in dripwater δ18O can be directly related to whether flowpaths are dominated by preferential/quick flow or diffuse/slow flow which challenges the paradigm of speleothems as archives of past variability in mean rainfall δ18O. Yet it is not known how common this flowpath effect is and whether it should be considered in the interpretation of speleothem δ18O records. Recently, Treble et al. (2022) analysed two global databases: SISAL v2 (Comas-Bru et al., 2020) and an extended compilation of dripwater from Baker et al. (2019). It was demonstrated that within-cave variability in mean δ18O values were common worldwide in both datasets. An analysis of cave meta-data demonstrated that the flowpath effect is unrelated to climate, cave depth or lithology; further supporting the ubiquitous nature of flowpaths, i.e., there is (1) a mixture of preferential and diffuse flow for all karstified carbonate rocks due to its triple-porosity nature (primary=matrix, secondary=fracture, tertiary=pipes and conduit); and (2) differences in soil/epikarst water storage and drainage characteristics. We demonstrate how a mechanistic understanding of flowpaths can lead to a more robust interpretation using a case study that is also relevant for managing water resources in the Mediterranean-type climate of south-west Australia. Using seven modern stalagmite records from four caves, plus dripwater data, we demonstrate that the cave δ18O record shows a common response to a sustained decrease in rainfall that impacted the region in the 1970s, characterised by a rise or ‘uptick’ in δ18O (Priestley et al., 2022). Mean annual rainfall δ18O values over the same period were quantified using observed and modelled data to have varied by −0.4 to +0.1 ‰ whereas the speleothem uptick is +1.5 ‰. The much larger magnitude of the uptick is consistent with a reduction in the preferential-flow component to these caves driven by reduced rainfall recharge. Preferential flow is an important contribution to groundwater. The ‘uptick’ or reduction in preferential flow implies that rainfall recharge to groundwater across the study region may no longer be reliably occurring. The longer paleo-record for south-west Australia confirms that no replicated upticks are seen in the last 800 years in stalagmites from the region and highlights the impact of climate change to water security in a region heavily dependent on groundwater. © Author(s) 2023. This work is distributed under the Creative Commons Attribution 4.0 License.
- ItemEnvironmental tracers in groundwaters and porewaters to understand groundwater movement through an argillaceous aquitard(Elsevier, 2017) Priestley, SC; Love, AJ; Post, V; Shand, P; Wohling, D; Kipfer, R; Payne, TE; Stute, M; Tyroller, LInter-aquifer leakage through an aquitard can be an important component of groundwater flow and can occur by diffuse leakage or via preferential pathways along secondary permeability features. In order to properly characterize inter-aquifer leakage it is desirable to use both porewater from the aquitard in conjunction with a regional investigation of groundwater in the aquifers. The aim of this study was to characterize inter-aquifer leakage through a regionally extensive aquitard between the Great Artesian Basin (GAB) and the deeper Arckaringa Basin of Australia. Chloride concentrations in the aquitard porewater profile indicates that transport through the aquitard is dominated by diffusion, but there is evidence at t least one location for increased interaquifer leakage due to secondary permeability features. © 2017 The Author(s). Published by Elsevier B.V.
- ItemGroundwater isotopic record in southwest Australia: links to recharge variations and climatic conditions(Australiasian Quaternary Association Inc., 2018-12-10) Priestley, SCGroundwater resources are a reliable and important source of water. Considering most large groundwater basins can contain ‘old’ groundwater where extraction exceeds groundwater recharge, knowledge of the past conditions and timing under which groundwater was recharged is needed to sustainably manage groundwater resources. Applying isotopic tools to groundwater contained in regional aquifer systems can provide low-resolution information on recharge intensity, recharge source and past climatic conditions for the region. Furthermore, an understanding of how groundwater recharge and climate have been connected in the past can be used to inform climate adaptation strategies for sustaining groundwater resources during climate change. Large regional groundwater systems, contained within the Perth Basin in southwest Australia were investigated in this study to provide information on groundwater recharge and climate over the past 35,000 years. Regional scale databases containing groundwater age and isotopic records are not commonly developed in Australia and are generally more site specific. Therefore, this Perth Basin database provides a unique opportunity to study and interpret a low-resolution palaeo-archive of groundwater recharge for southwest Australia. Groundwater ages (14CDIC) and stable O isotopes of water (δ18O) from two regional groundwater systems within the Perth Basin have been collated and groundwater ages calculated. The trends δ18O over time in the regional groundwater data are consistent with the groundwater flow line data supporting our hypothesis that groundwater δ18O is a proxy for palaeo-recharge. The Southern Perth Basin groundwater isotope record is interpreted to be a low resolution archive of recharge driven by changes in the relative intensity of past rainfall and recharge thresholds. This long-term stable isotopic recharge record provides a greater understanding of groundwater palaeo-recharge, as well as how recharge and climate have been connected in the past. © Author(s)
- ItemGroundwater δ18O record of paleorecharge and climate for the last 35ka in south-west Western Australia(International Union for Quaternary Research (INQUA), 2019-07-30) Priestley, SC; Meredith, KT; Treble, PC; Cendón, DI; Griffiths, AD; Hollins, SE; Baker, AA; Pigois, JP; Schafer, DThe isotopic composition of groundwater can be a useful indicator of rainfall isotope compositions and help to determine the drivers and impacts of rainfall and climate change. Additionally, as most large groundwater basins can contain ‘old’ groundwater where extraction exceeds groundwater recharge, knowledge of the past conditions and timing under which groundwater was recharged is needed to sustainably manage groundwater resources. Applying isotopic tools to groundwater contained in regional aquifer systems can provide low-resolution information on recharge intensity, recharge source and past climatic conditions for the region. Furthermore, an understanding of how groundwater recharge and climate have been connected in the past can be used to inform climate adaptation strategies for sustaining groundwater resources during climate change. Groundwater from south-west Western Australia located at the northernmost extent of the westerly wind belt can help constrain the drivers and impacts of rainfall and climate change in this region. Large regional groundwater systems contained within the Perth Basin in south-west Western Australia were used in this study to provide information on groundwater recharge and climate over the past 35,000 years. This dataset containing groundwater ages (14CDIC) and stable isotopes of water (δ18O and δ2H) from two regional groundwater systems within the Perth Basin provides a unique opportunity to produce a low-resolution palaeo-archive of groundwater recharge, and hence interpret rainfall and climate change, for south-west Western Australia. The trends in stable isotopes of water over time in the regional groundwater data are consistent with the groundwater flow line data supporting our hypothesis that groundwater stable isotopes are a proxy for palaeo-recharge. The Southern Perth Basin groundwater isotope record is interpreted to be a low resolution archive of recharge driven by changes in the relative intensity of past rainfall, moisture source from changes in the position of the westerlies and recharge thresholds. This long-term stable isotopic recharge record provides a greater understanding of groundwater palaeo-recharge, and the connection between recharge and climate in the past.
- 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
- ItemSpeleothem ‘uptick’ supports reduction in rainfall recharge to groundwater is unprecedented for last 800 years, SW Western Australia(Australasian Quaternary Association, 2022-12-06) Priestley, SC; Treble, PC; Baker, AA; Griffiths, AD; Abram, NJ; Meredith, KTSouthwestern Australia relies significantly on groundwater for domestic and industrial purposes. As water availability has decreased and is projected to continue to decrease with climate change, it is critical to understand the impacts of climate change on groundwater recharge for this region. Speleothem (e.g. cave stalagmites) deposition is directly related to groundwater recharge, as they form from rainfall which has infiltrated into the vadose zone and represent periods of potential aquifer recharge. In this study, modern speleothems from five caves record a consistent response to a sustained decrease in rainfall across south-west Australia that began in the 1970s, characterised by an ‘uptick’ in the speleothem oxygen isotopic composition (Priestley et al., 2022). It is demonstrated that the ‘uptick’ is in response to the shallow karst aquifers becoming disconnected from rainfall recharge due to regional drying. As the coastal caves are located in highly permeable host rock along the wettest zone of the region, our findings imply that rainfall recharge to groundwater across the southwest Australian region may no longer be reliably occurring. The paleo-record for speleothems from south-west Australia (Treble et al., 2022) provides a longer-term context to assess the recent isotopic uptick against and confirms that no similar events are seen in the last 800 years in stalagmites from the region.
- ItemUbiquitous karst hydrological control on speleothem oxygen isotope variability in a global study(Springer Nature, 2022-02-15) Treble, PC; Baker, AA; Abram, NJ; Hellstrom, JC; Crawford, J; Gagan, MK; Borsato, A; Griffiths, AD; Bajo, P; Markowska, M; Priestley, SC; Hankin, SI; Paterson, DJSpeleothem oxygen isotopic (δ18O) records are used to reconstruct past hydroclimate yet records from the same cave do not always replicate. We use a global database of speleothem δ18O to quantify the replicability of records to show that disagreement is common worldwide, occurs across timescales and is unrelated to climate, depth or lithology. Our global analysis demonstrates that within-cave differences in mean speleothem δ18O values are consistent with those of dripwater, supporting a ubiquitous influence of flowpaths. We present a case study of four new stalagmite records from Golgotha Cave, southwest Australia, where the isotopic differences between them are informed by cave monitoring. It is demonstrated that karst hydrology is a major driver of within-cave speleothem and dripwater δ18O variability, primarily due to the influence of fractures on flowpaths. Applying our understanding of water movement through fractures assists in quantitative reconstruction of past climate variability from speleothem δ18O records. © The Authors - Open Access under a Creative Commons Attribution 4.0 International License.
- ItemUbiquitous karst hydrological control on speleothem oxygen isotope variability in a global study(Springer Nature, 2022-02-15) Treble, PC; Baker, AA; Abram, NJ; Hellstrom, JC; Crawford, J; Gagan, MK; Borsato, A; Griffiths, AD; Bajo, P; Markowska, M; Priestley, SC; Hankin, SI; Paterson, DJSpeleothem oxygen isotopic (δ18O) records are used to reconstruct past hydroclimate yet records from the same cave do not always replicate. We use a global database of speleothem δ18O to quantify the replicability of records to show that disagreement is common worldwide, occurs across timescales and is unrelated to climate, depth or lithology. Our global analysis demonstrates that within-cave differences in mean speleothem δ18O values are consistent with those of dripwater, supporting a ubiquitous influence of flowpaths. We present a case study of four new stalagmite records from Golgotha Cave, southwest Australia, where the isotopic differences between them are informed by cave monitoring. It is demonstrated that karst hydrology is a major driver of within-cave speleothem and dripwater δ18O variability, primarily due to the influence of fractures on flowpaths. Applying our understanding of water movement through fractures assists in quantitative reconstruction of past climate variability from speleothem δ18O records. © Crown 2022 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
- 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