Geological processes like magmatic underplating, crustal compression, depth-dependent extension, and erosion can cause the exhumation of sedimentary basins, a long-term return of once deeply-buried rocks towards the earth’s surface. Such upward motions lead to cooling, fracturing and deformation of rocks, which may ultimately slow the hydrocarbon source rock maturation and change the porosity and permeability of sedimentary rocks. Geological and thermochronological evidence strongly suggests that the Gippsland Basin has experienced exhumation, but its temporal and spatial distribution and connection to the tectonic evolution of the region are not well established. Previous exhumation and uplift studies in the region had limited spatial and temporal coverage and did not assess the robustness of the exhumation estimates. Here, we apply compaction and thermochronology techniques to data from fifty-five wells to establish the spatial and temporal distribution of exhumation in the basin. A Markov Chain Monte Carlo approach is employed to estimate the uncertainties associated with the exhumation model and account for the uncertainty in the input data.
The results indicate that significant exhumation occurred in the Mid-Cretaceous, Paleogene and Miocene periods. Total Cretaceous-to-present exhumation varies from 3 km in the northwest to 0.5 km in the southeastern parts of the basin, with uncertainty estimates ranging between 0.05 to 0.2 km. Our exhumation results, literature and plate reconstruction along the southeastern Australian margins support the hypothesis that significant exhumation in the region was caused by compression and inversion tectonics connected to distant plate reorganisation along the Australian margins. While such uplifting and folding promoted hydrocarbon fluid migration and trapping, the subsequent exhumation destroyed hydrocarbon seals in the onshore parts of the basin. The recovered spatial and temporal distribution maps of uplift and exhumation and their associated uncertainties can thus further assist in identifying suitable underground locations for CO2 and H2 storage.