The Great Artesian Basin (GAB) is the largest groundwater basin in Australia, underlying approximately one fifth of the continent, including parts of Queensland, New South Wales, South Australia and the Northern Territory. The GAB consists of three hydraulically-connected geological basins – Eromanga, Surat and Carpentaria, which contain a sedimentary assemblage deposited almost continuously from Early Jurassic to Late Cretaceous. Groundwater from the GAB is a vital resource for agricultural and extractive industries, community water supplies. It supports cultural values and sustains groundwater-dependent ecosystems such as springs and wetlands. Knowledge of sedimentary depositional systems and stratigraphic correlations varies considerably across the GAB. Groundwater resources are continuous across the GAB and need to be mapped consistently to better assess the complex interconnected pathways across jurisdictions. The hydrogeological conceptualisations that underpin groundwater resource management approaches can be based on diverse and sometimes incompatible historic nomenclature across state and territory borders. Recent studies have shown significant spatial lithological variability within hydrostratigraphic units. Consistent and higher resolution mapping of the geological complexity at a basin-wide scale will provide an improved hydrogeological framework to underpin effective long-term management of GAB water resources. We have compiled and standardised existing and newly interpreted biostratigraphic data, well formation picks, 2D seismic and airborne electromagnetic data in a consistent chronostratigraphic framework to better correlate geological and hydrostratigraphic units across the GAB. Correlating the chronostratigraphy across the GAB reveals age-equivalent sediments deposited in different environments during alternating transgressive and regressive events. Comprehensive biostratigraphic control applying a unified zonation scheme helps to constrain lithological correlations. The distribution of sand/shale ratio in key wells across the GAB improves mapping of aquifer hydrogeological variability. This novel approach generates a consistent mapping of the regional distribution and properties of aquifers and aquitards across the GAB. The refined correlation of Jurassic and Cretaceous rock units between the Surat, Eromanga and Carpentaria basins improves our understanding of hydrogeological unit geometry, lithological variation, and potential groundwater connectivity above, below and within the GAB aquifers. The 3D hydrogeological architecture provides a model for refining hydraulic relationships between aquifers within the GAB, and enables development of more accurate system conceptualisations. This represents an important step towards the future goal of quantifying hydraulic properties and aquifer inter-connectivity to underpin more robust basin water balance estimates. This Abstract was submitted/presented to the 2022 Central Australian Basins Symposium IV 29-30 August (https://agentur.eventsair.com/cabsiv/).

The document summarises new seismic interpretation metadata for two key horizons from Base Jurassic to mid-Cretaceous strata across the western and central Eromanga Basin, and the underlying Top pre-Permian unconformity. New seismic interpretations were completed during a collaborative study between the National Groundwater Systems (NGS) and Australian Future Energy Resources (AFER) projects. The NGS and AFER projects are part of Exploring for the Future (EFTF)—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. The seismic interpretations build on previous work undertaken as part of the ‘Assessing the Status of Groundwater in the Great Artesian Basin’ (GAB) Project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion (Norton & Rollet, 2022; Vizy & Rollet, 2022; Rollet et al., 2022; Rollet et al., in press.), the NGS Project (Norton & Rollet, 2023; Rollet et al., 2023; Vizy & Rollet, 2023) and the AFER Project (Bradshaw et al., 2022 and in press, Bernecker et al., 2022, Iwanec et al., 2023; Iwanec et al., in press). The recent iteration of revisions to the 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 our understanding of 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 western and central Eromanga Basin. New seismic interpretations are being used in the western Eromanga, Pedirka and Simpson basins to produce time structure and isochore maps in support of play-based energy resource assessment under the AFER Project, as well as to update the geometry of key aquifers and aquitards and the GAB 3D model for future groundwater management under the NGS Project. These new seismic interpretations fill in some data and knowledge gaps necessary to update the geometry and depth of key geological and hydrogeological surfaces defined in a chronostratigraphic framework (Hannaford et al., 2022; Bradshaw et al., 2022 and in press; Hannaford & Rollet, 2023). The seismic interpretations are based on a compilation of newly reprocessed seismic data (Geoscience Australia, 2022), as part of the EFTF program, and legacy seismic surveys from various vintages brought together in a common project with matching parameters (tying, balancing, datum correcting, etc.). This dataset has contributed to a consolidated national data coverage to further delineate groundwater and energy systems, in common data standards and to be used further in integrated workflows of mineral, energy and groundwater assessment. The datasets associated with the product provides value added seismic interpretation in the form of seismic horizon point data for two horizons that will be used to improve correlation to existing studies in the region. The product also provides users with an efficient means to rapidly access a list of core data used from numerous sources in a consistent and cleaned format, all in a single package. The following datasets are provided with this product: 1) Seismic interpretation in a digital format (Appendix A), in two-way-time, on key horizons with publically accessible information, including seismic interpretation on newly reprocessed data: Top Cadna-owie; Base Jurassic; Top pre-Permian; 2) List of surveys compiled and standardised for a consistent interpretation across the study area (Appendix B). 3) Isochore points between Top Cadna-owie and Base Jurassic (CC10-LU00) surfaces (Appendix C). 4) Geographical layer for the seismic lines compiled across Queensland, South Australia and the Northern Territory (Appendix D). These new interpretations will be used to refine the GAB geological and hydrogeological surfaces in this region and to support play-based energy resource assessments in the western Eromanga, Pedirka and Simpson basins.