<div>The Lake Eyre surface water catchment covers around 1,200,000 km2 of central Australia, about one-sixth of the entire continent. It is one of the largest endorheic river basins in the world and contains iconic arid streams such as the Diamantina, Finke and Georgina rivers, and Cooper Creek. The Lake Eyre region supports diverse native fauna and flora, including nationally significant groundwater-dependent ecosystems such as springs and wetlands which are important cultural sites for Aboriginal Australians.</div><div><br></div><div>Much of the Lake Eyre catchment is underlain by the geological Lake Eyre Basin (LEB). The LEB includes major sedimentary depocentres such as the Tirari and Callabonna sub-basins which have been active sites of deposition throughout the Cenozoic. The stratigraphy of the LEB is dominated by the Eyre, Namba and Etadunna formations, as well as overlying Pliocene to Quaternary sediments.</div><div><br></div><div>The National Groundwater Systems Project, part of Geoscience Australia's Exploring for the Future Program (https://www.eftf.ga.gov.au/), is transforming our understanding of the nation's major aquifer systems. With an initial focus on the Lake Eyre Basin, we have applied an integrated geoscience systems approach to model the basin's regional stratigraphy and geological architecture. This analysis has significantly improved understanding of the extent and thickness of the main stratigraphic units, leading to new insights into the conceptualisation of aquifer systems in the LEB.</div><div><br></div><div>Developing the new understanding of the LEB involved compilation and standardisation of data acquired from thousands of petroleum, minerals and groundwater bores. This enabled consistent stratigraphic analysis of the major geological surfaces across all state and territory boundaries. In places, the new borehole dataset was integrated with biostratigraphic and petrophysical data, as well as airborne electromagnetic (AEM) data acquired through AusAEM (https://www.eftf.ga.gov.au/ausaem). The analysis and integration of diverse geoscience datasets helped to better constrain the key stratigraphic horizons and improved our overall confidence in the geological interpretations.</div><div><br></div><div>The new geological modelling of the LEB has highlighted the diverse sedimentary history of the basin and provided insights into the influence of geological structures on modern groundwater flow systems. Our work has refined the margins of the key depocentres of the Callabonna and Tirari sub-basins, and shown that their sediment sequences are up to 400 m thick. We have also revised maximum thickness estimates for the main units of the Eyre Formation (185 m), Namba Formation (265 m) and Etadunna Formation (180 m).</div><div><br></div><div>The geometry, distribution and thickness of sediments in the LEB is influenced by geological structures. Many structural features at or near surface are related to deeper structures that can be traced into the underlying Eromanga and Cooper basins. The occurrence of neotectonic features, coupled with insights from geomorphological studies, implies that structural deformation continues to influence the evolution of the basin. Structures also affect the hydrogeology of the LEB, particularly by compartmentalising groundwater flow systems in some areas. For example, the shallow groundwater system of the Cooper Creek floodplain is likely segregated from groundwater in the nearby Callabonna Sub-basin due to structural highs in the underlying Eromanga Basin.</div><div> Abstract submitted and presented at the 2023 Australian Earth Science Convention (AESC), Perth WA (https://2023.aegc.com.au/)

<div>The geological data includes the spatial extents of the Kati Thanda - Lake Eyre Basin (KT-LEB) project area, geological basin and sub-basin boundaries, and geological models of the extent and thickness of the main Cenozoic sedimentary packages in the KT-LEB in central Australia. This data package has particular focus on the geological Lake Eyre Basin (LEB) and its main sedimentary depocentres of the Callabonna and Tirari sub-basins, and the Cooper Creek Palaeovalley. The new geological datasets available in this data package were developed as part of the project on the Cenozoic geology, hydrogeology, and groundwater systems of the Kati Thanda - Lake Eyre Basin, the results of which were published in Evans et al. (2024). This activity was undertaken as part of the National Groundwater Systems project in the Geoscience Australia Exploring for the Future program.</div><div><br></div><div>This geological data package contains the following eight datasets:</div><div>1. Spatial extents of the boundary of the KT–LEB project area.</div><div>2. Major sites of Cenozoic sediment deposition within the KT-LEB.</div><div>3. Total thickness of Cenozoic sediments in KT-LEB, with derived contours, hillshaded image and Cenozoic cover extent. </div><div>4. Saturated thickness model of Cenozoic sediments in the KT-LEB with derived contours, hillshaded image and Cenozoic cover extent.</div><div>5. Model of the base of Cenozoic surface of the KT-LEB project area, with derived contours, hill-shaded image and Cenozoic cover extent.</div><div>6. Model of thickness of Quaternary sediments of the KT-LEB with derived contours, hillshaded image and the Quaternary sediments extent outline.</div><div>7. Model of thickness of Namba Formation in KT-LEB, with derived contours, hillshaded image and the Namba Formation extent outline.</div><div>8. Model of thickness of Eyre Formation in KT-LEB with derived contours, hillshaded image and the Eyre Formation extent outline.</div><div><br></div><div>Reference:</div><div>Evans TJ, Bishop C, Symington NJ, Halas L, Hansen JWH, Norton CJ, Hannaford C and Lewis SJ (2024) <em>Cenozoic geology, hydrogeology, and groundwater systems: Kati Thanda – Lake Eyre Basin</em>, Record 2024/05, Geoscience Australia, Canberra, http://dx.doi.org/10.26186/147422.</div><div><br></div>

<div>The Kati Thanda – Lake Eyre Basin (KT–LEB) covers about 1.2 million square kilometres of outback Australia. Although the basin is sparsely populated and relatively undeveloped it hosts nationally significant environmental and cultural heritage, including unique desert rivers, sweeping arid landscapes, and clusters of major artesian springs. The basin experiences climatic extremes that intermittently cycle between prolonged droughts and massive inland floods, with groundwater resources playing a critical role in supporting the many communities, industries, ecological systems, and thriving First Nations culture of the KT–LEB.</div><div><br></div><div>As part of Geoscience Australia’s National Groundwater Systems Project (in the Exploring for the Future Program) this report brings together contemporary data and information relevant to understanding the regional geology, hydrogeology and groundwater systems of Cenozoic rocks and sediments of the KT–LEB. This work represents the first whole-of-basin assessment into these vitally important shallow groundwater resources, which have previously received far less scientific attention than the deeper groundwater systems of the underlying Eromanga Basin (part of the Great Artesian Basin). The new knowledge and insights about the geology and hydrogeology of the basin generated by this study will benefit the many users of groundwater within the region and will help to improve sustainable management and use of groundwater resources across the KT–LEB.</div><div><br></div>