The Perth Basin is a north to north-northwest trending, onshore and offshore sedimentary basin extending about 1300 km along the southwestern margin of the Australian continent. This is a large (172,300 km2), structurally complex basin that formed during the separation of Australia and Greater India in the Permian to Early Cretaceous. It includes a significant onshore component and extends offshore to the edge of continental crust in water depths of up to 4500m.
The structural architecture of the Perth Basin is the product of oblique rifting during the Permian, Late Triassic to Early Jurassic and Middle Jurassic to Early Cretaceous, superimposed over pre-existing basement terrains. Extension during the Permian produced a series of deep (up to 15 km), north-south trending rift basins (Bunbury Trough and Dandaragan Trough) along the western margin of the Yilgarn Craton. The Abrolhos Sub-basin represents a northwestern branch of the Permian rift system formed along the southwestern margin of the Northampton Complex, which is separated from the Dandaragan Trough by an intra-basin high represented by the Beagle Ridge, Dongara Terrace and Greenough Shelf. The Houtman Sub-basin is a major depocentre for Triassic and Jurassic sedimentary rocks that formed as a westward thickening sag basin across a hinge zone during the Middle Triassic to Middle Jurassic, and was extensively faulted during Late Jurassic to Early Cretaceous rifting. The Vlaming Sub-basin is the major Middle Jurassic to Early Cretaceous rift basin in the Perth Basin and is characterised along its northern extent by a very large and deep half graben that dips to the west. The footwall block of this half graben consists of a series of shallow tilted fault blocks containing mainly Permian and older strata from the Edward's Island Block.
Breakup during the Early Cretaceous (Valanginian) was associated with widespread inversion, erosion, strike-slip tectonics and volcanism, which significantly modified the structural architecture of the Perth Basin. Major structural elements associated with breakup tectonism include an area of inverted Permian half graben in the Turtle Dove Ridge and the Zeewyck Sub-basin which formed in a zone of strike-slip faulting along the Turtle Dove Transfer.