Multiphase Deformation of the Northern Carnarvon Basin

Abstract

The Northern Carnarvon Basin has experienced multiple phase of deformation, most likely starting in the Lower Palaeozoic and continuing to the present day. The widespread availability of public domain 2D and 3D seismic data sets over large parts of the basin allows mapping of structures at different stratigraphic levels in considerable detail, which in turn enables spatial relationships between structures of different ages to be established. Permian rifting established the fundamental underlying architecture of the basin and created the accommodation space for the accumulation of thick sequences of Triassic sediments. NE-SW trending structures were reactivated under E-W extension, starting in the latest Triassic, but the onset and magnitude of rifting is variable across the basin. The initial phase of rifting ended in the Middle Jurassic, but subsequent reactivation is variable, both spatially and temporally. Upper Jurassic to Lower Cretaceous reactivation is most evident in the easternmost and westernmost parts of the basin, and may be associated with a change in stress regime. A particularly short lived and enigmatic episode of extension occurs in the Exmouth sub-basin, associated with significant uplift and erosion. The Valanginian unconformity marks the end of most rift related activity, although minor fault reactivation occurs into the Albian. Upper Cretaceous to Recent compressional structures form at different times in different parts of the basin.