Depositional wedge cycles on evolving plate margin, western and northwestern Australia

The Barrow province lies at the transition between the western and northwestern rift domains of the Australian continental margin. As these domains evolved during the Mesozoic, five depositional wedge sequences developed in the eastern half of the province. Each sequence possesses distinct stratigraphic and sedimentological characteristics, which differs from the others as a function of proximity, direction, and style of rift-related diastrophism along the evolving margin. The first depositional sequence developed during the Triassic as part of a regional Tethyan-facing passive margin clastic wedge. This event was followed during the Early and Middle Jurassic by a second more provincial sequence in response to early syn-rift fault-related subsidence. By the Callovian, a deep anastomosing rift complex had formed and deposition of the third Late Jurassic cycle was initially very localized, confined by the new graben topography. However, stratigraphic continuity returned during post-breakup subsidence of the northwestern margin as subregional depositional systems began to bury the fragmented borderland. This cycle was terminated at the close of the Jurassic in response to renewed rifting between western Australia and Greater India. Sediment stripped from the uplifted rift shoulders fed the northerly prograding Barrow delta system to form a fourth depositional sequence during the Late Jurassic-early Neocomian. The final cycle commenced as Greater India uncoupled from Australia during the middle Neocomian. Post-breakup subsidence is reflected by a major regional transgression and the development of a second margin-wide depositional wedge during the later Cretaceous. The close temporal and spatial relationship that exists between these cycles and the evolution of the western and northwestern Australian continental margin emphasizes the importance of tectonic control upon sedimentation.