3D structural and stratigraphic model of the Perth Basin, Western Australia: Implications for sub-basin evolution

The history of rifting and breakup of eastern Gondwana is recorded by the development and fill of the Perth Basin in Western Australia. Knowledge of the structural architecture and stratigraphic geometry of the Perth Basin is essential to understand the evolution of the Western Australian margin and its applications to hydrocarbon and geothermal prospects, and effective aquifer management. This study integrates existing, publicly available geological, gravity, magnetic and digital elevation data to develop the first refined, regional structural and stratigraphic interpretation of the entire onshore and offshore Perth Basin, Western Australia. This new 3D model offers formation depth and thickness predictions in areas of sparse or no data. The model shows significant heterogeneity in the preserved formation thicknesses and depths at both local and regional scales. These differences may have resulted from differential subsidence and/or differential exhumation, but the formation geometries alone cannot distinguish between these two models if any erosion has occurred. Only the Lower to Middle Jurassic stratigraphy has been minimally eroded and thereby records the net subsidence. This stratigraphic interval shows that subsidence was broadly hinged from south to north, with a greater subsidence rate in the southern and central Perth Basin. Localised differences in thicknesses across adjacent sub-basins were likely controlled by differential displacement along sub-basin bounding faults during subsidence and, subsequently, during exhumation episodes. This new 3D model of the entire Perth Basin provides a framework for numerical simulations of fluid and heat flow and large-scale tectonic analysis, such as stratigraphic forward modelling of the southwestern Australian margin.