Fault timing and depocentre development in the northern Perth Basin during the evolution of the East Gondwana rift

Despite renewed interest in the energy resources of the Perth Basin, rift propagation, the evolution of fault activity and depocentre development along the Western Australian margin during rifting of East Gondwana are not well established. Rifting resulted in a series of predominantly NNW–SSE trending graben and half-graben extending from the Southern Carnarvon Basin in the north, through to the Perth Basin in the south. Gravity and magnetic data indicate two regions of greater structural complexity along this margin, with the northern of these regions data-poor. We investigate the more southerly region, commonly referred to as the northern Perth Basin, a Paleozoic to Mesozoic depocentre that developed through multiple phases of extension with variable extension directions, recording intracontinental rifting and eventual break-up of Australia and Greater India as part of the East Gondwana interior rift. Recently acquired seismic surveys that better image the pre-Mesozoic stratigraphy, together with legacy seismic and well data, have been utilised to create composite sections perpendicular and parallel to the rift axis. These composite sections reveal a progressive southward shift in fault activity and depocentres from the late Carboniferous through to the Early Cretaceous and that towards the south, many of the N–S trending fault segments previously thought to be active during the Cisuralian (early Permian) initiate much later in the Jurassic or Cretaceous. By contrast, E–W trending faults in the north of the basin, which formed perpendicular or at high angles to the rift axis, become throughgoing faults during the Late Triassic to Early Jurassic. Ultimately, these new interpretations provide evidence for episodic propagation of the rift system toward the south.