To test existing geological interpretations and the regional stratigraphic relationships of the Carrara Sub-basin with adjacent resource-rich provinces, the deep stratigraphic drill hole NDI Carrara 1 was located on the western flanks of the Carrara Sub-basin, on the seismic line 17GA-SN1. The recovery of high quality near-continuous core from the Carrara Sub-basin, in concert with the spectrum of baseline analytical work being conducted by Geoscience Australia through the EFTF program, as well as other work by government and university researchers is greatly improving our understanding of this new basin. While recently published geochemistry baseline datasets have provided valuable insight into the Carrara Sub-basin, the age of the sedimentary rocks intersected by NDI Carrara 1 and their chronostratigraphic relationships with adjacent resource rich regions has remained an outstanding question. In this contribution, we present new sensitive high-resolution ion microprobe (SHRIMP) geochronology results from NDI Carrara 1 and establish regional stratigraphic correlations to better understand the energy and base-metal resource potential of this exciting frontier basin in northern Australia.

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/).

<div><strong>Output Type:</strong> Exploring for the Future Extended Abstract</div><div><br></div><div><strong>Short abstract: </strong>Australia is the driest inhabited continent on Earth and relies heavily on groundwater to support communities, industries, ecosystems and cultural values. Despite groundwater resources transcending state and territory boundaries, each jurisdiction operates under different legislative frameworks, policies and water management approaches, and accordingly coordination between jurisdictions is crucial to achieving the common goal of water security. Improving the alignment of water strategies between states and territories requires a national coordination of data collation with common standards and integration of subsurface geology, using a consistent and up-to-date 3D hydrogeological framework for better understanding of groundwater systems and flow pathways at regional to national scales. Despite ever increasing data availability in each jurisdiction there is a lack of comprehensive knowledge regarding cross-jurisdictional sedimentary architecture, aquifer extents and hydraulic connections. Geoscience Australia, through the Exploring for the Future program, is developing a consistent national chronostratigraphic framework to underpin the development of 3D (hydro)geological models which can be used to standardise hydrogeological classifications, update borehole stratigraphy and provide a basis for integrating diverse geoscientific datasets. By collaborating with jurisdictions to harmonise 3D geology nationally through correlation with the geological time scale, aquifer boundaries can be updated and shared with other collaborators such as the Bureau of Meteorology to ensure that national groundwater datasets are updated with the latest geological knowledge. This chronostratigraphic method is suitable for sedimentary basins and provides a consistent platform to support effective resource assessment and management, infrastructure planning, and environmental impact assessment at regional and national scales.</div><div><br></div><div><strong>Citation: </strong>Rollet, N., Vizy, J., Norton, C.J., Hannaford, C., McPherson, A., Symington, N., Evans, T., Nation, E., Peljo, M., Bishop, C., Boronkay, A., Ahmad, Z., Szczepaniak, M., Bradshaw, B., Wilford, J., Wong, S., Bonnardot, M.A. &amp; Hope, J., 2024. Developing a 3D hydrogeological framework for Australia. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, https://doi.org/10.26186/149418 </div>