Browsing by Author "Feitz, AJ"

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    Groundwater chemistry baseline of the Walloon coal measures in the Clarence-Moreton and Surat basins, Queensland, Australia
    (International Association of Hydrogeologists, 2013-09-19) Raiber, M; Cox, ME; Cendón, DI; Feitz, AJ
    The Walloon Coal Measures (WCM) are a major target for coal seam gas exploration in the Surat and Clarence-Moreton basins in Queensland and New South Wales, Australia. It is now widely acknowledged that an improved understanding of the groundwater baseline is essential. Fundamental is determining the geological framework and an unbiased examination of the natural range, or baseline, of groundwater chemistry of the coal seams and adjacent aquifers. In order to determine the processes that control the spatial variability and evolution of groundwater chemistry, the chemistry baseline data of the WCM for the Surat and Clarence-Moreton basins are placed within the framework of a 3D geological model. In the assessment of the water chemistry baseline, four groundwater chemistry groups were identified from the hierarchical cluster analysis (HCA) which was applied to historical groundwater chemistry records from the Department of Natural Resources and Mines (DNRM) groundwater database. Each of these distinct groups contains groundwaters of a similar composition, which result from a number of different processes (e.g. groundwater recharge or interaction with other aquifers). However, groundwater of only one group has the typical composition of CSG waters, as documented by very high HCO3, and simultaneously low SO4, Ca and Mg concentrations, whereas the chemical composition of groundwater assigned to the other groups suggests that these follow a different evolutionary pathway. Following this initial screening, a total of ~60 samples was collected from the different groundwater chemistry groups for analysis of water chemistry (major, trace, rare earth elements and dissolved gases) and isotopic fingerprinting (d2H, d2H-CH4, d13C-DIC, d13C-CH4, d18O, 87Sr/86Sr,14CDIC and 36Cl/Cl). The analyses were combined with results from a similar groundwater chemistry study undertaken in the Surat Basin during 2009-2011 that aimed to establish a groundwater chemistry baseline for geological storage of CO2. The analyses of dissolved gases shows that there is a strong variability of dissolved CH4 concentration within groundwaters of the WCM, ranging from values below the reporting limit to ~50 mg/L. Likewise, isotope signatures and groundwater residence times within these coal-bearing sequence are highly variable spatially, reflecting the range of processes involved in groundwater evolution as well as the variable composition of these sedimentary rocks.
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    Strontium isotopes in the atmosphere, geosphere and hydrosphere: developing a systematic “fingerprinting” framework of rocks and water in sedimentary basins in eastern Australia
    (Elsevier, 2024-11-15) Raiber, M; Feitz, AJ; Cendón, DI; Flook, S; Suckow, A; Schöning, G; Hofmann, H; Martinez, J; Maas, R; Kelly, BFJ
    Understanding the connection between aquifers, aquitards, and groundwater-dependant ecosystems remains a key challenge when developing a conceptual hydrogeological model. The aim of this study was to develop a systematic strontium isotope (87Sr/86Sr) fingerprinting framework of rocks and water within the sedimentary Surat and Clarence-Moreton basins (SCM basins) in eastern Australia – an area of extensive coal seam gas development and high potential for aquifer and groundwater-surface water connectivity. To do this, new groundwater samples (n = 298) were collected, analyzed and integrated with published data (n = 154) from the basins' major sedimentary, volcanic and alluvial aquifers, including the major coal seam gas target, the Walloon Coal Measures. Samples were also analyzed from rainfall (n = 2) and surface water (n = 40). In addition, rock core samples (n = 39) from exploration and stratigraphic wells were analyzed to determine the range of Sr isotope composition from host rocks. The analyses of cores demonstrate a distinct and systematic contrast in 87Sr/86Sr between different hydrogeological units. This confirms that all major hydrogeological units have a narrow range with unique 87Sr/86Sr population characteristics that are useful for guiding conceptual model development. Comparison with selected hydrochemical and groundwater age tracers (14C and 36Cl) suggests only limited changes of 87Sr/86Sr from recharge beds to the deeper parts of the basins or with a decrease in natural 14C and 36Cl tracer content along flow paths. Stream sampling during baseflow conditions confirms that 87Sr/86Sr in surface waters are similar to those of the underlying bedrock formations. We demonstrated that 87Sr/86Sr analyses of rocks and water provide a powerful hydrostratigraphic and chemostratigraphic fingerprinting framework in the SCM basins, enabling reliable assessments of plausible aquifer and groundwater-surface water interconnectivity pathways. Applied in other complex multi-aquifer sedimentary basins in Australia, and globally, a similar approach can help to constrain conceptual hydrogeological models and facilitate improved water resource management. © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY - NC 4.0 license.