Controls on Mesozoic rift-related uplift and syn-extensional sedimentation in the Exmouth Plateau

Abstract

The Exmouth Plateau, part of the Northern Carnarvon Basin, has experienced a multi-phase extensional history, which is associated with regional-scale uplift, as well the uplift and erosion of individual footwall blocks. Detailed interpretation of 3D seismic surveys over the area shows that fault activity began in in the latest Triassic, mainly on NNE-SSW and NE-SW trending faults. Rotation of Triassic fault blocks initiated in the Upper Triassic and continued during the Jurassic. Erosion of pre-rift Triassic sediment occurred during the latest Triassic and the Jurassic. In the latest Jurassic deposition infilled half-grabens and deposition onto highs was limited in the west as the area was starved of sediment. A significant change in sediment supply in the early Cretaceous associated with progradation of the Barrow Delta resulted in the infilling of previously starved half-grabens. Fault activity had decreased by the mid-Cretaceous, with limited activity confined to major faults. Later Cretaceous sediment distribution in the study area was largely controlled by remnant topography. High-quality 3D seismic data allows a detailed examination of the way in which rift-related fault activity affects sediment distribution. In addition to creating fault block traps in pre-rift Triassic sediments, understanding syn-extensional sediment patterns and fault reactivation has implications for syn-rift plays and seal integrity.