Hydrogeological architecture of the Great Artesian Basin: a consistent tool for future groundwater management

The Great Artesian Basin (GAB) is the largest groundwater basin in Australia. It underlies nearly one quarter of the continent, including parts of Queensland, New South Wales, South Australia and the Northern Territory. Groundwater from the GAB is a vital resource for agricultural and extractive industries, as well as for community water supply. It supports cultural values and sustains a range of groundwater-dependent ecosystems. Water managers from each jurisdiction manage their GAB resources using hydrogeological conceptualisations based on diverse historic nomenclature. However, GAB resources are continuous across borders and recent studies have shown high spatial variability in the hydrostratigraphic units across the basin. Therefore, there is a clear need to map the geological complexity consistently at a basin-wide scale in order to provide a hydrogeological framework to underpin effective long-term management of GAB water resources. The present study compiles and standardises existing and newly interpreted biostratigraphic and well formation picks from geological logs, 2D seismic and airborne electromagnetic data in a consistent chronostratigraphic framework. This framework was used to correlate geological units across the basin. Correlating the chronostratigraphy across the basin revealed age equivalent sediments deposited in different depositional environments during transgressive and regressive alternation events. Rigorous biostratigraphic control, using a common unified zonation scheme was used to identify lithological correlations. Rock properties were attributed based on sediment facies deposited during similar geological events. The approach provides a consistent way of mapping the distribution and properties of aquifers and aquitards across the whole GAB. The refined correlation of Jurassic and Cretaceous units between the Surat and Eromanga basins improves the resolution of our understanding of hydrogeological unit geometry and lithological variation that may influence groundwater flow within and between aquifers. The 3D hydrogeological architecture provides a model to refine hydrogeological conceptualisations and assist in improving basin water balance estimates. This Abstract was submitted/presented to the 2022 Australasian Groundwater Conference 21-23 November (https://agc2022.com.au/)