The Paleozoic Bonaparte Basin in the East Kimberley Region, northern Australia, has a complex history of basin evolution, tectonic inversion, basin fluid expulsion, mineralisation, multi-scale Paleozoic and Neogene-to-Recent tectonics, and deep weathering and erosion processes that have modified the primary sedimentary basin architecture, influencing groundwater processes, aquifer properties and groundwater quality distribution.
In 2015, Geoscience Australia commenced groundwater investigations jointly funded by the WA Water for Food (WFF) Program and Geoscience Australia’s Exploring for the Future (EFTF) Program. Data acquisition included: 2,800 km of airborne electromagnetic (AEM) data; a LiDAR dataset; >100 Surface Nuclear Magnetic Resonance (SNMR) measurements; drilling (to depths of ~300 m); borehole geophysics (induction, spectral gamma and nuclear magnetic resonance (NMR)); a seismic reflection survey; structural, geological, geomorphic and morphotectonic mapping and analysis; recharge, discharge and vegetation structure mapping; and hydrochemical and hydrodynamic analysis. AEM inversions include 1D, 2.5D and 3D inversions, while the project has also re-processed pre-existing industry seismic reflection data. In complementary investigations, the West Australian Department of Primary Industries and Regional Development (DPIRD) carried out a soil suitability assessment, surface water assessment, and a hydrogeological assessment of the near-surface aquifer system including shallow drilling, bore testing and numerical groundwater modelling.
The project has found significant groundwater resources in several inter-layered dipping aquifers. The main groundwater resource potential lies within the near-surface Kuriyippi Formation aquifer. This formation directly underlies the surficial Cockatoo Sands (soils), identified as potentially prospective for irrigated agriculture. Groundwater salinities are generally very low (<800 µS/cm), with high estimated transmissivities (>100 m2/day to >1,000 m2/day). The Kuriyippi Formation aquifer is unconfined where it is in direct connection with the surface, and confined where it is overlain by the Keep Inlet Formation. Potential fresh groundwater resources also occur in the older Tanmurra Formation aquifer system which is confined, has high transmissivities, and hydraulic heads above those of the overlying Kuryippi Formation aquifers. Recharge in the area is to the Kurriyippi Formation aquifers below the Cockatoo Sand Plain, and to the Tanmurra Formation in the hills in the west of the area. AEM mapping combined with hydrochemistry and hydrodynamic data from the few bores suggests limited connectivity between the main stacked aquifers, which may be separate groundwater systems.
Overall, an inter-disciplinary, multi-physics approach involving the acquisition of new hydrogeophysical and hydrogeological datasets has revealed significant new groundwater resources within a stacked sequence of aquifers in the tectonically inverted Palaeozoic Bonaparte Basin.