Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Tectonostratigraphic Evolution of the Exmouth Sub-basin, Northwest Shelf, Western Australia
(1) Earth Sciences, Royal Holloway University of London, Egham, United Kingdom.
Detailed analysis of fault architecture using 3D seismic data on the western margin of the Exmouth Sub-basin, NW Shelf of Australia, gives an understanding of stratigraphic and 
structural
evolution of the sub-basin since Late Triassic to Recent. This part of the NW Shelf has undergone a complex tectonic evolution with Late Triassic-Jurassic rifting, Jurassic thermal subsidence and inversion, Late Jurassic-Early Cretaceous rifting, Late Cretaceous inversion and Cenozoic post-rift subsidence and, in places, Paleogene inversion.
The first phase of rifting is characterized by an oblique east-west extension to form north to northeast trending segmented extensional faults. An overlapping en-echelon array of Rhaetian to Oxfordian fault segments is interpreted to be a result of reactivation of preexisting northeast basement fabrics. Subsequent post-rift subsidence was initiated in the Oxfordian and was punctuated by north-south inversion that occurred during the Oxfordian to Tithonian.
The second phase of rifting occurred in the Berriasian with west-northwest extension. These extensional faults are characterized by domino-style pseudo-conjugate fault arrays. Rifting was terminated by a Valanginian age contraction interpreted to be related to ridge push associated with Cuvier and Gascoyne seafloor spreading systems. This uplift and erosion event ceased in the Aptian and was followed by the Late Cretaceous northeast inversion. The widespread Cenozoic post-rift thermal subsidence was developed with localised non-tectonic post-rift polygonal fault systems. Paleogene contraction potentially promoted breaching of inversion anticlinal traps developed by northeast trending reactivated faults and formed vertically linked fault systems.
This investigation of the detailed stratigraphic and structural
evolution of the Exmouth Sub-basin provides an understanding of the tectonostratigraphic evolution of this part of NW Australian marginal basins. It has implications for hydrocarbon trap development and preservation.
This research project is part of a Royal Holloway University of London - Geoscience Australia research collaboration. Schlumberger is thanked for providing GeoFrame software.