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  • We collected 38 groundwater and two surface water samples in the semi-arid Lake Woods region of the Northern Territory to better understand the hydrogeochemistry of this system, which straddles the Wiso, Tennant Creek and Georgina geological regions. Lake Woods is presently a losing waterbody feeding the underlying groundwater system. The main aquifers comprise mainly carbonate (limestone and dolostone), siliciclastic (sandstone and siltstone) and evaporitic units. The water composition was determined in terms of bulk properties (pH, electrical conductivity, temperature, dissolved oxygen, redox potential), 40 major, minor and trace elements as well as six isotopes (δ18Owater, δ2Hwater, δ13CDIC, δ34SSO4=, δ18OSO4=, 87Sr/86Sr). The groundwater is recharged through infiltration in the catchment from monsoonal rainfall (annual average rainfall ~600 mm) and runoff. It evolves geochemically mainly through evapotranspiration and water–mineral interaction (dissolution of carbonates, silicates, and to a lesser extent sulfates). The two surface waters (one from the main creek feeding the lake, the other from the lake itself) are extraordinarily enriched in 18O and 2H isotopes (δ18O of +10.9 and +16.4 ‰ VSMOW, and δ2H of +41 and +93 ‰ VSMOW, respectively), which is interpreted to reflect evaporation during the dry season (annual average evaporation ~3000 mm) under low humidity conditions (annual average relative humidity ~40 %). This interpretation is supported by modelling results. The potassium (K) relative enrichment (K/Cl mass ratio over 50 times that of sea water) is similar to that observed in salt-lake systems worldwide that are prospective for potash resources. Potassium enrichment is believed to derive partly from dust during atmospheric transport/deposition, but mostly from weathering of K-silicates in the aquifer materials (and possibly underlying formations). Further studies of Australian salt-lake systems are required to reach evidence-based conclusions on their mineral potential for potash, lithium, boron and other low-temperature mineral system commodities such as uranium. <b>Citation:</b> P. de Caritat, E. N. Bastrakov, S. Jaireth, P. M. English, J. D. A. Clarke, T. P. Mernagh, A. S. Wygralak, H. E. Dulfer & J. Trafford (2019) Groundwater geochemistry, hydrogeology and potash mineral potential of the Lake Woods region, Northern Territory, Australia, <i>Australian Journal of Earth Sciences</i>, 66:3, 411-430, DOI: 10.1080/08120099.2018.1543208

  • The role of palaeovalley evolution in the manifestation of salinity across the Australian continent P.M. English1 & J.W. Magee1, 2 1Geospatial & Earth Monitoring Division, Geoscience Australia, GPO Box 378, Canberra, ACT 2601 Pauline.English@ga.gov.au 2Department of Earth & Marine Sciences, Australian National University, Canberra, ACT 0200 jwmagee@ems.anu.edu.au Networks of palaeovalleys characterise much of arid, semi-arid and sub-humid Australia, including widespread rangelands and agriculturally important regions. These ancient river valley systems are very commonly the focus of salinity across our landscape, both primary salinity (Quaternary salt lakes and associated saline landforms), and secondary salinity in regions that have been cleared for agricultural development in the last 150 years. The preservation of palaeovalleys is a legacy of the continents tectonic stability, low relief and slow erosion and sedimentation rates. Palaeovalleys drain all the cratonic blocks and extend from Precambrian basement uplands across Palaeozoic, Mesozoic and Cainozoic sedimentary basins. They are now largely filled with Tertiary, or older, sediments and are commonly blanketed with Quaternary lacustrine, alluvial or aeolian sediments, including saline sediments and salts. While the palaeovalleys and their sedimentary infill are relatively ancient (early to mid Tertiary) the groundwater systems they host have evolved during latest Tertiary and Quaternary times. Salt began to concentrate in these palaeovalley networks and surrounding hinterlands from as long as 350 000 years ago, in response to glacial-interglacial cyclicity driven by global climate regimes. More recent salt accumulation in the historic period is the consequence of hydrologic disequilibrium wrought by land clearing which has caused broad-scale mobilisation of ancient salt stores into topographic lower areas and waterways in agricultural regions. Sodium chloride (NaCl) is the dominant salt in the Australian terrestrial environment, in both the arrays of ancient salt lakes and in secondary salinised agricultural regions. This reflects the dominance of marine aerosol source of salts in our rainfall and the longevity of salt accumulation in the near-surface environment. The marine signature is further pronounced in the case of primary salinity occurrences, where calcium sulphate, or gypsum (CaSO4.2H2O), is prevalent across the inland landscape. The ubiquity and solubility of NaCl and its mobility in shallow groundwater systems accounts for the recurrence and concentration of salinity in palaeovalley systems in particular. The persistence of ancient palaeovalley networks and of marine-derived salts in the salinised Australian landscape forms the basis of comparisons with southern Africa, for example, where tectonism and a significantly higher proportion of terrestrially-derived salts predispose contrasting manifestations of salinity. Such comparisons provide some insight and a broad perspective relevant to Australias contemporary salinity issues.

  • <p>Summary <p>Spring point locations compiled for the Nulla Basalt Province <p>A compilation of spring locations as identified through various methods, including existing Queensland Springs Database, topographic mapping, fieldwork visits, landholder citizen scientist mapping, and inspection for neighbouring similar features in Google Earth. This compilation has had locations adjusted through inspecting visible imagery and elevation data to identify the likely positions of springs at higher resolution.

  • <div>This was the last of five presentations held on 31 July 2023 as part of the National Groundwater Systems Workshop. Towards developing a 3D hydrogeological framework for Australia: A common chronostratigraphic framework for aquifers&nbsp;</div><div><br></div>

  • This data set contains gridded values for unit thickness, sand thickness, shale thickness and percentage, and porosity of an area in the Great Artesian Basin (GAB). The data was measured, calculated and reported in "Geology of the Cooper and Eromanga Basins, Queensland", Draper J.J., Qld Government - Natural Resources and Mines, 2000" (ISSN 1039-5555, ISBN 0 7345 2411 0) . This data forms a subset of the values reported in Draper 2000, with the subset containing the stratigraphic areas of interest to the GAB Water Resource Assessment.

  • Areas of groundwater intake beds for the Great Artesian Basin, including regionally variable local recharge in some places. Data is available as polygons in Shapefile format. This GIS data set was produced for the Great Artesian Basin Water Resource Assessment and used in: Figures 2.2 and 5.29 of Ransley TR and Smerdon BD (eds) (2012) Hydrostratigraphy, hydrogeology and system conceptualisation of the Great Artesian Basin. A technical report to the Australian Government from the CSIRO Great Artesian Basin Water Resource Assessment. CSIRO Water for a Healthy Country Flagship, Australia. Figure 1.4 in Smerdon BD, Ransley TR, Radke BM and Kellett JR (2012) Water resource assessment for the Great Artesian Basin. A report to the Australian Government from the CSIRO Great Artesian Basin Water Resource Assessment. CSIRO Water for a Healthy Country Flagship, Australia. This dataset and associated metadata can be obtained from www.ga.gov.au, using catalogue number 75842.

  • Unregulated river reaches with riparian vegetation potentially intersecting shallow groundwater in the Great Artesian Basin. Interpreted from enhanced vegetation index (EVI) time series with high coefficients for the period 2000-2008. Data is available in Shapefile format This GIS data set was produced for the Great Artesian Basin Water Resource Assessment, and used in Figure 9.2 of Ransley TR and Smerdon BD (eds) (2012) Hydrostratigraphy, hydrogeology and system conceptualisation of the Great Artesian Basin. A technical report to the Australian Government from the CSIRO Great Artesian Basin Water Resource Assessment. CSIRO Water for a Healthy Country Flagship, Australia. This dataset and associated metadata can be obtained from www.ga.gov.au, using catalogue number 76533.

  • This web service provides access to gridded data produced by Geoscience Australia from studies of Australian groundwater and hydrogeological systems.

  • This web service provides access to gridded data produced by Geoscience Australia from studies of Australian groundwater and hydrogeological systems.