Thermochronological constraints on the tectonic history of the Polda Basin

Abstract

The Polda Basin is a narrow, east–west striking intracontinental basin that extends ~400 km from the onshore Eyre Peninsula in South Australia to the offshore Great Australian Bight and contains up to 5 km of strata, with a thick sequence of Neoproterozoic rocks overlain by unconformably-bound sequences of Carboniferous-Permian, Jurassic and Cenozoic strata. Though the Polda Basin has witnessed limited exploration for hydrocarbons, it is attracting renewed interest due to the potential for underground hydrogen storage in Neoproterozoic halites, whilst surrounding regions of the Gawler Craton are considered prospective for natural hydrogen. To date however, knowledge of the tectonic history of the Polda Basin, which is critical to assessing its potential role in the energy transition, is limited. Here we present results from a regional apatite fission track analysis study of the Eyre Peninsula, focussing on data from the onshore Kilroo-1A borehole, which provide insights into the burial and exhumation history of the Polda Basin. Results indicate that the preserved Upper Jurassic sequence was thicker prior to Late Cretaceous exhumation, which may have supplied sediment to the adjacent Ceduna Sub-basin. Our results highlight a complex history of Phanerozoic vertical motions in this region, which have implications for both resource and energy storage potential.