Exploring for the Future—Architecture of the deep Ti Tree Basin (Report 1) Northern Territory

This report presents key results from the Ti Tree Basin project completed as part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. The Ti Tree Basin is one of four Northern Territory water management areas in the Southern Stuart Corridor (SSC) area, part of Geoscience Australia’s Exploring for the Future project. The Ti Tree Basin is approximately 150–200 kilometres north of Alice Springs. The intracratonic basin is infilled Cenozoic alluvial and lacustrine sediments. Since the 1960s the basin has been the focus of many government investigations and policies into its groundwater potential. Most have concentrated on the relatively shallow Cenozoic aquifers less than 100 metres below surface. Wischusen et al. (2012) identified the potential of the deeper aquifers (at depths of greater than 100 m) to expand the potential water resources of the Ti Tree Basin. This report uses three sets of AEM data, two acquired by Geoscience Australia and one from historic mineral exploration, to map the depth to basement in the Ti Tree Basin. We confirm the prediction of Wischusen et al. (2012) that there is significant potential for a much thicker Cenozoic succession in the Basin and show that up to 500 m of sediments are present in fault bounded structures. We demonstrate that these sediments occur in two successions, one of probably Eocene age within narrow, fault-bounded troughs and the other of probable Miocene to Pliocene age occurring across a wider area. The two successions are separated by a low angle unconformity. We interpret the lower succession as forming during strike-slip opening of the basin, and the upper succession as being deposited by passive basin infill. The faults forming the deep basin show are mostly congruent with basement structures previously interpreted from aeromagnetic data. Most of the lower succession has not been fully penetrated by earlier drilling. The interpreted AEM data shows that the deep Ti Tree Basin may contain extensive sandy aquifer units whose potential are completely unexplored. We recommend further investigations, including further stratigraphic drilling, mapping of the uniformity surface, and installation of monitoring bores, to more fully explore the potential of the deep Ti Tree Basin.