Aims:

Groundwater is vital for community water supplies and economic development in Australia. It also supports indigenous cultural values and sustains a range of groundwater dependent ecosystems, including springs and vegetation communities. Geoscience Australia’s regional assessments and basin inventories are investigating Australia’s groundwater systems to improve knowledge of the nation’s groundwater systems under the Exploring for the Future (EFTF) Program. Where applicable, we applied integrated basin analysis workflows to build models of geological and hydrostratigraphic architecture and link them to a nationally consistent chronostratigraphic framework. While the focus of this paper is the Great Artesian Basin (GAB), the overlying Lake Eyre Basin (LEB) and the Upper Darling Floodplain (UDF) region, these datasets and surfaces continue expanding beyond this current study area by linking additional studies using this consistent approach, towards building a national picture of groundwater systems.

Method:

Geoscience Australia continues to refine the chronostratigraphic framework that correlates time equivalent geological units from neighbouring basins and hydrostratigraphy for the GAB, LEB and UDF (Figure 1), infilling key data and knowledge gaps from previous compilations and adding new interpretation. In collaboration with Commonwealth, State and Territory government agencies, we compiled and standardised data from thousands of boreholes, including stratigraphic (Norton & Rollet, 2023; Vizy & Rollet, 2023a) and biostratigraphic picks (Hannaford & Rollet, 2023), 2D and 3D seismic (Szczepaniak et al., 2023) and airborne electromagnetic derived conductivity sections across the study area (McPherson et al., 2022a &b; Wong et al., 2023). We undertook a detailed stratigraphic review of thousands of boreholes with geophysical logs to construct consistent regional transects across the GAB, LEB and UDF (Norton & Rollet, 2023). In addition we applied geological time constraints from hundreds of boreholes with existing and newly interpreted biostratigraphic data (including from legacy palynological preparations from the Geoscience Australia archives where old reports could not be found) (Hannaford & Rollet, 2023). New biostratigraphic data from core samples has been analysed from bores in the Northern Territory, South Australia and Queensland. The biostratigraphic data was calibrated to the most recent biostratigraphic zonation scheme and used to provide geological time constraint to the stratigraphic picks.

Results:

We infilled the stratigraphic correlations along key transects across Queensland, New South Wales, South Australia and the Northern Territory to refine nomenclature and stratigraphic relationships between the Surat, Eromanga and Carpentaria basins, improving chronostratigraphic understanding within the Jurassic‒Cretaceous to Cenozoic units. We extended the GAB geological framework to include the overlying LEB and UDF as well to better resolve the Cenozoic stratigraphy and structure and potential for hydrogeological connectivity. The new data and information fill recognised gaps and refine the previous 3D geological model of the entire GAB and extend it to the LEB and UDF region (Vizy & Rollet, 2023b).

The updated 3D geological and hydrostratigraphic model provides a framework to integrate additional hydrogeological and rock property data. It assists in refining hydraulic relationships between aquifers within the GAB, LEB, UDF and provides a basis for developing more detailed hydrogeological system conceptualisations.

The improved cross-jurisdictional chronostratigraphic understanding supports improvements to the common agreed terminology for Australian hydrogeological units and groundwater provinces between jurisdiction borders

( http://www.bom.gov.au/water/groundwater/naf/). This enables the delivery of geologically and hydrogeologically consistent datasets to inform decision makers and the broader groundwater community in Australia.

This abstract was submitted/presented to the 2023 Australasian Groundwater / New Zealand Hydrological Society (AGC NZHS) Joint Conference ( https://www.hydrologynz.org.nz/events-1/australasian-groundwater-nzhs-joint-conference)

References:

Hannaford, C. and Rollet, N. 2023. Palynological data review of selected boreholes in the Great Artesian, Lake Eyre basins and Upper Darling Floodplain (part 2): Infilling data and knowledge gaps. Record 2023/27. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/147173

McPherson, A., Rollet, N., Vizy, J., Kilgour, P. 2022a. Great Artesian Basin eastern recharge area assessment - northern Surat Basin airborne electromagnetic survey interpretation report. RECORD: 2022/017. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2022.017

McPherson, A., Buckerfield, S., Tan, K., Kilgour, P., Symington, N., Ray, A., Buchanan, S. 2022b. Developing (hydro)geological conceptual models to support improved groundwater management. The Upper Darling Floodplain Project, New South Wales. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/147055

Norton, C. J. and Rollet, N. 2023. Regional stratigraphic correlation transects across the Great Artesian, Lake Eyre basins and Upper Darling Floodplain region (part 2): Infilling data and knowledge gaps. Record 2023/28. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/147243

Szczepaniak, M., Rollet, N., Bradshaw, B, Lund, D., Iwanec, J., Bradey, K., Vizy, J., 2023. Western and central Eromanga and underlying basins seismic interpretation ‒ Data package. Geoscience Australia, Canberra. https://pid.geoscience.gov.au/dataset/ga/147900

Vizy, J. & Rollet, N. 2023a. Australian Borehole Stratigraphic Units Compilation (ABSUC) 2023 Version 1.0. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/147641

Vizy, J. & Rollet, N., 2023b. 3D geological and hydrogeological surfaces update in the Great Artesian, Lake Eyre basins and Upper Darling Floodplain region (part 2): report and data package. Geoscience Australia, Canberra. https://pid.geoscience.gov.au/dataset/ga/148552

Wong, S.C.T., Hegarty, R.A., Pitt, L., Crowe, M.C., Roach, I., Nicoll, M., LeyCooper, Y., Hope, J., Bonnardot, M. 2023. Eastern Resources Corridor Airborne Electromagnetic Interpretation Data Package. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/147992