The National Groundwater Systems (NGS) project, is part of the Australian Government’s Exploring for the Future (EFTF) program, led by Geoscience Australia (https://www.eftf.ga.gov.au/national-groundwater-systems), to improve understanding of Australia’s groundwater resources to better support responsible groundwater management and secure groundwater resources into the future. The project is developing new national data coverages .to further delineate groundwater systems and improve data standards and workflows of groundwater assessment. While our conceptual understanding of the hydrogeology of the Great Artesian Basin (GAB, Figure 1) continues to grow, in many parts of the Eromanga, Surat and Carpentaria basins that form the GAB we are still reliant on legacy data and knowledge from the 1970s of variable quality. Additional information provided by recent studies in various parts of the GAB highlights the level of architectural complexity and spatial variability in stratigraphic and hydrostratigraphic units across the basin. We now recognise the need to standardise these regional studies to map such geological complexity in a consistent, basin-wide hydrostratigraphic framework that can support effective long-term management of GAB water resources. The recent iteration of revision of GAB geological and hydrogeological surfaces (Vizy & Rollet, 2022) provides a framework to interpret various data sets consistently (e.g., boreholes, airborne electromagnetic, seismic data) and in a 3D domain, to improve the aquifer geometry, and the lateral variation and connectivity in hydrostratigraphic units across the GAB (Rollet et al., 2022). Vizy and Rollet (2022) highlighted some areas with low confidence in the interpretation of the GAB where further data acquisition or interpretation may reduce uncertainty in the mapping. One of these areas was in the Carpentaria Basin, particularly the transition from the offshore to onshore across the Gulf of Carpentaria. This data compilation provides open file SEGY, cultural data and value added seismic interpretation in the form of seismic horizons and grids for two key surfaces, these enable improved correlation to existing studies. This data also aim to provide users an efficient mean to rapidly access core data from numerous sources in a consistent and cleaned format, all in a single package. This dataset provides: 1) Seismic data compilation in a digital format with publically accessible information, including scanned seismic sections converted to SEGY format where digital data was not available; 2) Base Mesozoic and Near Base Cenozoic seismic interpretation in two-way-time; 3) Depth converted regional surfaces for the Base Mesozoic and Near Base Cenozoic unconformities generated using additional constraints such as AEM interpretation and borehole constraints previously compiled in Vizy & Rollet (2022). This new interpretation will be used to refine the GAB geological and hydrogeological surfaces in this region.

This report presents the results of an assessment of geoscience data and tools applied in the eastern Eromanga Basin to improve the hydrogeological conceptualisations. The assessment is one component of the Australian Government funded project ‘Assessing the Status of Groundwater in the Great Artesian Basin’. The results demonstrate that the application of existing and new geoscientific data and technologies has the potential to further improve our understanding of the Great Artesian Basin (GAB) hydrogeological system thus supporting the responsible management of basin water resources. Hydrogeological synthesis using airborne electromagnetic data, in conjunction with hydro- and chrono-stratigraphic data and well geological information, are effective at mapping the three dimensional distribution of the aquifers and aquitards. The results lead to an improved understanding of groundwater intake bed geometry, potential connectivity between aquifers, possible structural controls on groundwater flow paths, and plausible source of groundwater discharging as springs. In the southern part of the study area, the dominantly shale-rich Evergreen Formation is electrically conductive, but is locally resistive in places due to sand-rich facies. These areas allow hydraulic connectivity between the overlying and underlying Hutton and Precipice sandstone aquifers. Anticlinal folds and juxtaposed strata are observed on AEM traverses along the strike of the aquifer units, and includes the Hutton, Adori and Cadna-owie – Hooray sandstones. Abrupt folding and juxtaposed strata were interpreted as fault zones. Both structural features have the potential of controlling groundwater flow directions or groundwater storage compartmentalisation. The northern limits of Precipice Sandstone and Evergreen Formation are at Blackall and south of Barcaldine towns respectively. This zone also coincides with the southern edge of the east-west trending sub-surface Barcaldine Ridge where the basal Jurassic sequence abut against. On and north of the Barcaldine Ridge, the Cadna-owie – Hooray, Adori and Hutton sandstones are present. Mapping using AEM conductivity sections affirm that the Hutton Sandstone is the major aquifer in the northern part of the study area. The Poolowanna Formation, an age equivalent to the Evergreen Formation and Precipice Sandstone, is laterally extensive towards the northern part of the study area. This formation crops-out west of Lake Buchanan in the Great Dividing Range, but forms sub-crops elsewhere along the groundwater recharge areas. Numerous groundwater springs and spring clusters are present along the east and west of the outcropping sandstone hills in the Great Dividing Range. In the northern parts of the study area, source of groundwater for the springs are mainly derived from the Hutton Sandstone aquifers through either gravity-feed or lateral groundwater flow process. Polygonal faults mainly occur on conductive and fined-grained sedimentary units of the Rolling Downs Group. There is lack of observable evidence from AEM conductivity sections on the presence of polygonal faults to suggest preferential groundwater flows along these potential hydraulic conduits. Further investigation using ground based methods are needed to establish the presence of the faults and their hydraulic properties.

<div><strong>Output Type: </strong>Exploring for the Future Extended Abstract</div><div><br></div><div><strong>Short Abstract: </strong>Australia's Great Artesian Basin (GAB) is a vital groundwater system extending across parts of Queensland, New South Wales, South Australia, and the Northern Territory, crucial for community water supplies, economic development, indigenous cultural values and groundwater dependent ecosystems. Managing GAB groundwater poses challenges due to the complex structure of the sedimentary basin, requiring a better understanding of aquifers, aquitards, and hydraulic connections at a whole GAB scale. Additionally, inconsistencies in nomenclature and subdivisions across the basin further complicate the definition and description of these strata. This study employs an integrated basin analysis workflow using new and existing data to create a 3D geological model tied to a consistent chronostratigraphic framework and State and Territory hydrostratigraphic classifications. The model refines the characteristics of 18 hydrogeological units, offering insights into aquifer boundaries and connectivity. This comprehensive approach enhances the 'whole-of-Basin' subsurface geological understanding, benefiting groundwater management, resource assessments, uncertainty risk assessment and environmental impact assessments across multiple jurisdictions and the broader resource sector (e.g., Carbone Capture and Storage and hydrogen).</div><div><br></div><div><strong>Citation: </strong>Rollet, N., Vizy, J., Norton, C.J., Hannaford, C., McPherson, A., Symington, N., Evans, T., Bradshaw, B., Szczepaniak, M., Bui Xuan Hy, A., Schoning, G. &amp; Keppel, M., 2024. Great Artesian Basin 3D chronostratigraphic model: providing new insights into hydrogeological variability and connectivity. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts. Geoscience Australia, Canberra, https://doi.org/10.26186/149235</div>

<div>Understanding groundwater flow dynamics within the Great Artesian Basin (GAB) is critical for responsible management of groundwater from an environmental, economic and cultural perspective. Numerical groundwater flow modelling involves generating a simplified representation of a groundwater system and using Darcy’s Law to simulate groundwater flow rates and the distribution of hydraulic heads throughout the system. This is a pilot study aimed at developing a workflow for groundwater flow modelling of the Great Artesian Basin using Bayesian methods. In this report, we present our initial results from building and running a steady-state groundwater flow model of the entire GAB. We demonstrate a Bayesian inference framework to generate an ensemble of groundwater flow models allowing an assessment of the uncertainty of model parameters and flow velocities.&nbsp;</div><div>Several models have been built to simulate groundwater flow across various areas and layers of the GAB. Most of these models aimed to predict the likely impacts on the groundwater system of some future scenario, generally climate change or groundwater extraction relating to mining activities. While these models are well-suited to their purpose, their focus on particular regions or aquifers makes them unsuitable for investigating large-scale groundwater flow throughout the GAB. In contrast, the model built as part of this study captures the entire GAB and aims to simulate large-scale flow. Although not in scope for this pilot study, the questions a model at this scale is capable of addressing include characterising 3D flow within hydrogeological layers, computing groundwater flux between aquifers and between sub-basins, inferring hydraulic properties and identifying poor quality data. As this model is steady-state and uses hydraulic head data from before the year 2000, it provides a baseline estimate of groundwater flow without considering recent anthropogenic forcing or transient system stresses.&nbsp;</div><div>The GAB is represented as a 14 hydrogeological layer model including basement, Permo-Carboniferous basins, Mesozoic sedimentary aquifers and aquitards and Cenozoic layers. This includes updated hydrogeological surfaces from the GAB project. The input data consisted of 8,065 hydraulic head measurements and 6,151 estimates of recharge rate while the model parameters were a single hydraulic conductivity value for each of the 14 layers. The modelling domain was discretised using 10 x 10 km cells in the horizontal plane and the mesh was deformed vertically to fit between the topography and the basement surface, with the resulting mesh having a vertical discretisation of no coarser than 50 metres. The top boundary condition was a constant head boundary that was a smoothed version of topography. The sides and bottom of the model have no flux boundary conditions and a buffer zone around the GAB was included to minimise boundary effects.&nbsp;&nbsp;</div><div>In total 2500 groundwater flow simulations were run using a Bayesian inversion framework. The inversion sampled various combinations of input parameters to find models with a relatively low misfit, which was calculated by squaring the difference between the observed and simulated values of hydraulic head and recharge. Rather than searching for a global minima, the Metropolis Hastings Markov Chain Monte Carlo sampling algorithm was used to explore a range of possible models and estimate the posterior distribution of each layer’s hydraulic conductivity.&nbsp;</div><div>The model performed adequately and the model parameters were generally consistent with the prior probability distributions based on previous modelling studies. However, the posterior distribution of model parameters were very broad indicating the model was not particularly informative in its current form.&nbsp;&nbsp;</div><div>Groundwater flow velocity vectors from the maximum likelihood model were used to investigate groundwater trends within the Cadna-owie-Hooray aquifer. Uncertainty of model predictions were investigated by calculating the groundwater flow velocity variance across the ensemble. This study demonstrates that it is technically feasible to use Bayesian inference to probabilistically mode groundwater flow across the entire GAB. However, for this approach to yield useful results, more work is required to understand the impacts of simplifying assumptions about layer properties, the quality of the input data and model structure on the resulting flow model.&nbsp;</div><div><br></div>

<div>This document provides metadata for the gross depositional environment (GDE) interpretations that have been generated in support of the energy resource assessments under the Australia’s Future Energy Resources (AFER) project.&nbsp;&nbsp;</div><div>The AFER projects is part of Geoscience Australia’s Exploring for the Future (EFTF) Program—an eight year, $225 million Australian Government funded geoscience data and precompetitive information acquisition program to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This will help support a strong economy, resilient society and sustainable environment for the benefit of all Australians. The EFTF program is supporting Australia’s transition to a low emissions economy, industry and agriculture sectors, as well as economic opportunities and social benefits for Australia’s regional and remote communities. Further details are available at http://www.ga.gov.au/eftf.&nbsp;</div><div>The GDE data sets provide high level classifications of interpreted environments where sediments were deposited within each defined play interval in the Pedirka, Simpson and Western Eromanga basins. Twelve gross depositional environments have been interpreted and mapped in the study (Table 1). A total of 14 play intervals have been defined for the Pedirka, Simpson and Western Eromanga basins by Bradshaw et al. (2022, in press), which represent the main chronostratigraphic units separated by unconformities or flooding surfaces generated during major tectonic or global sea level events (Figure 1). These play intervals define regionally significant reservoirs for hydrocarbon accumulations or CO2 geological storage intervals, and often also include an associated intraformational or regional seal.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</div><div>GDE interpretations are a key data set for play-based resources assessments in helping to constrain reservoir presence. The GDE maps also provide zero edges showing the interpreted maximum extent of each play interval, which is essential information for play-based resource assessments, and for constructing accurate depth and thickness grids.&nbsp;&nbsp;</div><div>GDE interpretations for the AFER Project are based on integrated interpretations of well log and seismic data, together with any supporting palynological data. Some play intervals also have surface exposures within the study area which can provide additional published paleo-environmental data. The Pedirka, Simpson and Western Eromanga basins are underexplored and contain a relatively sparse interpreted data set of 42 wells and 233 seismic lines (Figure 2). Well and outcrop data provide the primary controls on paleo-environment interpretations, while seismic interpretations constrain the interpreted zero edges for each play interval. The sparse nature of seismic and well data in the study area means there is some uncertainty in the extents of the mapped GDE’s.&nbsp;&nbsp;</div><div>The data package includes the following datasets:&nbsp;&nbsp;</div><div>Play interval tops for each of the 42 wells interpreted – provided as an ‘xlsx’ file.&nbsp;</div><div>A point file (AFER_Wells_GDE) capturing the GDE interpretation for each of the 14 play intervals in each of the 42 wells – provided as both a shapefile and within the AFER_GDE_Maps geodatabase.&nbsp;</div><div>Gross depositional environment maps for each of the 14 play intervals (note that separate GDE maps have been generated for the Namur Sandstone and Murta Formation within the Namur-Murta play interval, and for the Adori Sandstone and Westbourne Formation within the Adori-Westbourne play interval) – provided as both shapefiles and within the AFER_GDE_Maps geodatabase.&nbsp;</div><div>&nbsp;</div><div>These GDE data sets are being used to support the AFER Project’s play-based energy resource assessments in the Western Eromanga, Pedirka and Simpson basins.&nbsp;</div><div><br></div>

As part of the Great Artesian Basin (GAB) Project a pilot study was conducted in the northern Surat Basin, Queensland, to test the ability of existing and new geoscientific data and technologies to further improve our understanding of hydrogeological systems within the GAB, in order to support responsible management of basin water resources. This report presents selected examples from the preliminary interpretation of modelled airborne electromagnetic (AEM) data acquired as part of this pilot study. The examples are selected to highlight key observations from the AEM with potential relevance to groundwater recharge and connectivity. Previous investigations in the northern Surat Basin have suggested that diffuse groundwater recharge rates are generally low (in the order of only a few millimetres per year) across large areas of the GAB intake beds—outcropping geological units which represent a pathway for rainfall to enter the aquifers—and that, within key aquifer units, recharge rates and volumes can be heterogeneous. Spatial variability in AEM conductivity responses is identified across different parts of the northern Surat Basin, including within the key Hutton Sandstone aquifer. Consistent with findings from other studies, this variability is interpreted as potential lithological heterogeneity, which may contribute to reduced volumes of groundwater entering the deeper aquifer. The influence of geological structure on aquifer geometry is also examined. Larger structural zones are seen to influence both pre- and post-depositional architecture, including the presence, thickness and dip of hydrogeological units (or parts thereof). Folds and faults within the Surat Basin sequences are, in places, seen as potential groundwater divides which may contribute to compartmentalisation of aquifers. Discrete faults have the potential to influence inter-aquifer connectivity. The examples presented here demonstrate the utility of AEM models, in conjunction with other appropriate geophysical and geological data, for characterising potential recharge areas and pathways within the main GAB aquifer units, by helping to better define aquifer geometry, lithological heterogeneity and possible structural controls. Such assessments have the potential to further improve our understanding of groundwater recharge and flow path variability at local to regional scales. Acquisition of broader AEM data coverage across groundwater recharge areas, along with complementary geophysical, geological and hydrogeological data, would further assist in quantifying recharge variability, facilitating revised water balance estimates for the basin and thereby supporting GAB water resource management and policy decision-making.

<div>This report summarises information regarding groundwater processes considered to have direct influence on the water balance for the Great Artesian Basin (GAB). These processes are recharge, discharge, and connectivity within the GAB sequence, as well as connectivity with underlying basins and overlying cover. </div><div>The substantial body of literature available on the GAB gives the impression that there is a considerable degree of understanding of the GAB groundwater system. This is, however, misleading. The reality is that many reports and reviews have been cited or reworked from pre-existing studies without carrying over the original uncertainties. Over time, the scale of knowledge gaps has been reduced only incrementally, while there has been a growing appreciation of the complexities in the system. With so much conceptual and quantitative uncertainty, much additional investigation is still required.</div><div><br></div>

This report presents palynological data compiled and analysed as part of the National Groundwater Systems (NGS) Project. NGS is part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. This study builds on previous work (Hannaford et al., 2022) undertaken as part of the ‘Assessing the Status of Groundwater in the Great Artesian Basin’ project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, examined an additional 688 boreholes across the GAB and compiled 149 new palynological summary sheets having Jurassic‒Cretaceous succession, with reviewed palynology data (down to total depth). The combined borehole palynological data examined from this study and the previous GAB work (Hannaford et al., 2022) is compiled in Appendix B4. The combined dataset totals 1,394 boreholes examined and 652 with palynology in the stratigraphic interval of interest, 102 of these boreholes contained Cenozoic palynology relevant to the Lake Eyre Basin. This information has been used to revise stratigraphic correlations across the GAB (Norton & Rollet, 2022 and 2023). Initial review of the stratigraphy in the Lake Eyre Basin (LEB) compiled existing palynology from outcrop, mineral and petroleum boreholes. An additional 28 boreholes in the Upper Darling Floodplain region were examined, 16 of which contained relevant palynology. The main palynological data infill in the GAB and LEB region during this follow-up study focused on: 1. Collecting, processing and analysing new biostratigraphic data on 149 key boreholes particularly across the Eromanga and Surat basins boundary. The study focussed on integrating data in New South Wales from the southern Surat Basin and central Eromanga Basin. 2. Further palynological data infill and palynological analysis on 15 samples from 7 boreholes in the western Eromanga Basin to assess difficulties in correlating the stratigraphy across the Algebuckina Sandstone. 3. Compiling existing analyses and update any historical palynological data in the Lake Eyre Basin to reflect the latest zonation scheme developed in this study. The new palynological data combined with new zircon data from other studies in the Carpentaria and Surat basins (Foley et al., 2020, 2021, 2022; La Croix et al., 2022, respectively) provides information on the tie to the geological timescale and help refine the chronostratigraphic chart that summarises stratigraphic correlations across the Carpentaria, Surat and Eromanga basins of Hannaford et al. (2022). All boreholes were examined outside of the Cooper and Bowen basins boundaries with selected boreholes around transects defined for stratigraphic correlation review through the Cooper and Bowen basin outlines (Norton & Rollet, 2022 and 2023). As a result, most of the remaining unreviewed palynological data lies within the Cooper and Bowen basins. The results of the palynology data infill in the western Eromanga Basin, in South Australia and Northern Territory, show that the Algebuckina Sandstone section is dominated by clean sandstone and so the cuttings samples were also dominated by sand. Although attempts were made to concentrate the shale from the cuttings in the thicker shale mid formation, this did not yield results, due to the amount of caved Cretaceous material. An initial assessment of the Lake Eyre Basin palynological data and zonation scheme was undertaken using information derived from water, mineral and petroleum boreholes. This provides an initial state of knowledge for the Lake Eyre Basin that can be built on in the future. Recommendations are provided for further studies to build a better understanding of the stratigraphy in the Great Artesian and Lake Eyre basins.

This report presents palynological data compiled and analysed as part of Geoscience Australia’s ‘Assessing the Status of Groundwater in the Great Artesian Basin’ project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion. Diverse historic nomenclature within the Great Artesian Basin (GAB) Jurassic‒Cretaceous succession in different parts of the GAB makes it difficult to map consistently GAB resources across borders, at a basin-wide scale, in order to provide a geological and hydrogeological framework to underpin effective long-term management of GAB water resources. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, examined 706 wells across the GAB and compiled 407 wells, having Jurassic‒Cretaceous succession, with reviewed palynology data (down to total depth). This initial palynology data review allowed identification of new data samples from 20 wells (within the 407 wells) in Queensland and South Australia to fill data and knowledge gaps within the Jurassic‒Cretaceous GAB succession. This study resulted in: 1) a summary compilation of existing palynology data on 407 wells selected to create a regional framework between the Surat, eastern Eromanga and western Eromanga basins, to help regional correlations across the GAB, 2) a review of several different palynology zonation schemes and adaptation to a single consistent scheme, applying the scheme of Price (1997) for the spore pollen zonation and Partridge (2006) for the marine zonation, 3) updated stratigraphic charts across the Surat, Eromanga and Carpentaria basins, 4) identification of data and knowledge gaps, and 5) sampling of new palynology data to help fill some data and knowledge gaps identified in 13 key wells in the Surat Basin and 10 key wells in the Eromanga Basin. In the Surat Basin the new sampling program has targeted units within: the Evergreen Formation, Hutton Sandstone, Springbok Sandstone, Gubberamunda Sandstone, Orallo Formation, Mooga Sandstone, Bungil Formation. In the Eromanga Basin the sampling program targeted units within: the Poolowanna Formation, Hutton Sandstone, Adori Sandstone, Algebuckina Sandstone, Namur Sandstone and Hooray Sandstone. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, provides updated biostratigraphic information compiled in a standardised chronostratigraphic framework across the Surat, Eromanga and Carpentaria basins that mostly comprise the GAB. This work allows comparison of various geological, lithological, hydrogeological schemes. It provides links between various lithostratigraphic units, with different nomenclature, across jurisdictions. It also links these units to some key regional chronostratigraphic markers that can be used to generate consistent surfaces that correlate to aquifer and aquitard boundaries. The compilation of legacy and newly sampled and analysed palynology data allows refinement of a regional chronostratigraphic framework that can be used to map a common Mesozoic play interval scheme across all the resource types, for basin-scale assessments of groundwater, hydrocarbons, carbon capture and storage, and mineral potential. From this correlation of time equivalent geological units deposited in different environments, it is then possible to map internal lithological variations in stratigraphic facies within sequences that influence hydraulic properties and connectivity within and between aquifers across the GAB. The updated geometry and variability mapping within and between aquifers will help refine the conceptual hydrogeological model, to assess how aquifers and aquitards are connected within the GAB. The revised conceptual hydrogeological model can facilitate an improved understanding of potential impacts from exploitation of sub-surface resources in the basin, providing a basis for more robust water balance estimates.

This data package, completed as part of Geoscience Australia’s National Groundwater Systems (NGS) Project, presents results of the second iteration of the 3D Great Artesian Basin (GAB) and Lake Eyre Basin (LEB) (Figure 1) geological and hydrogeological models (Vizy & Rollet, 2023) populated with volume of shale (Vshale) values calculated on 2,310 wells in the Surat, Eromanga, Carpentaria and Lake Eyre basins (Norton & Rollet, 2023). This provides a refined architecture of aquifer and aquitard geometry that can be used as a proxy for internal, lateral, and vertical, variability of rock properties within each of the 18 GAB-LEB hydrogeological units (Figure 2). These data compilations and information are brought to a common national standard to help improve hydrogeological conceptualisation of groundwater systems across multiple jurisdictions. This information will assist water managers to support responsible groundwater management and secure groundwater into the future. This 3D Vshale model of the GAB provides a common framework for further data integration with other disciplines, industry, academics and the public and helps assess the impact of water use and climate change. It aids in mapping current groundwater knowledge at a GAB-wide scale and identifying critical groundwater areas for long-term monitoring. The NGS project is part of the Exploring for the Future (EFTF) program—an eight-year, $225 million Australian Government funded geoscience data and precompetitive information acquisition program. The program seeks to inform decision-making by government, community, and industry on the sustainable development of Australia's mineral, energy, and groundwater resources, including those to support the effective long-term management of GAB water resources. This work builds on the first iteration completed as part of the Great Artesian Basin Groundwater project (Vizy & Rollet, 2022; Rollet et al., 2022), and infills previous data and knowledge gaps in the GAB and LEB with additional borehole, airborne electromagnetic and seismic interpretation. The Vshale values calculated on additional wells in the southern Surat and southern Eromanga basins and in the whole of Carpentaria and Lake Eyre basins provide higher resolution facies variability estimates from the distribution of generalised sand-shale ratio across the 18 GAB-LEB hydrogeological units. The data reveals a complex mixture of sedimentary environments in the GAB, and highlights sand body development and hydraulic characteristics within aquifers and aquitards. Understanding the regional extents of these sand-rich areas provides insights into potential preferential flow paths, within and between the GAB and LEB, and aquifer compartmentalisation. However, there are limitations that require further study, including data gaps and the need to integrate petrophysics and hydrogeological data. Incorporating major faults and other structures would also enhance our understanding of fluid flow pathways. The revised Vshale model, incorporating additional boreholes to a total of 2,310 boreholes, contributes to our understanding of groundwater flow and connectivity in the region, from the recharge beds to discharge at springs, and Groundwater Dependant Ecosystems (GDEs). It also facilitates interbasinal connectivity analysis. This 3D Vshale model offers a consistent framework for integrating data from various sources, allowing for the assessment of water use impacts and climate change at different scales. It can be used to map groundwater knowledge across the GAB and identify areas that require long-term monitoring. Additionally, the distribution of boreholes with gamma ray logs used for the Vshale work in each GAB and LEB units (Norton & Rollet, 2022; 2023) is used to highlight areas where additional data acquisition or interpretation is needed in data-poor areas within the GAB and LEB units. The second iteration of surfaces with additional Vshale calculation data points provides more confidence in the distribution of sand bodies at the whole GAB scale. The current model highlights that the main Precipice, Hutton, Adori-Springbok and Cadna-owie‒Hooray aquifers are relatively well connected within their respective extents, particularly the Precipice and Hutton Sandstone aquifers and equivalents. The Bungil Formation, the Mooga Sandstone and the Gubberamunda Sandstone are partial and regional aquifers, which are restricted to the Surat Basin. These are time equivalents to the Cadna-owie–Hooray major aquifer system that extends across the Eromanga Basin, as well as the Gilbert River Formation and Eulo Queen Group which are important aquifers onshore in the Carpentaria Basin. The current iteration of the Vshale model confirms that the Cadna-owie–Hooray and time equivalent units form a major aquifer system that spreads across the whole GAB. It consists of sand bodies within multiple channel belts that have varying degrees of connectivity' i.e. being a channelised system some of the sands will be encased within overbank deposits and isolated, while others will be stacked, cross-cutting systems that provide vertical connectivity. The channelised systemtransitions vertically and laterally into a shallow marine environment (Rollet et al., 2022). Sand-rich areas are also mapped within the main Poolowanna, Brikhead-Walloon and Westbourne interbasinal aquitards, as well as the regional Rolling Downs aquitard that may provide some potential pathways for upward leakage of groundwater to the shallow Winton-Mackunda aquifer and overlying Lake Eyre Basin. Further integration with hydrochemical data may help groundtruth some of these observations. This metadata document is associated with a data package including: • Seventeen surfaces with Vshale property (Table 1), • Seventeen surfaces with less than 40% Vshale property (Table 2), • Twenty isochore with average Vshale property (Table 3), • Twenty isochore with less than 40% Vshale property (Table 4), • Sixteen Average Vshale intersections of less than 40% Vshale property delineating potential connectivity between isochore (Table 5), • Sixteen Average Vshale intersections of less than 40% Vshale property delineating potential connectivity with isochore above and below (Table 6), • Seventeen upscaled Vshale log intersection locations (Table 7), • Six regional sections showing geology and Vshale property (Table 8), • Three datasets with location of boreholes, sections, and area of interest (Table 9).