An Overview of Geoscience Australia’s Regional Mapping over the Central North West Shelf


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A regional mapping program conducted by Geoscience Australia has addressed aspects of exploration uncertainty within the Triassic succession of the Roebuck Basin and parts of the adjacent sub-basins (central North West Shelf). N-trending and NE-trending fault sets dominate the Triassic section. Vertical separation of faults between the upper Triassic and lower Triassic successions results in different fault fabrics mapped on the top and base Triassic surfaces. Major faults locally penetrate through the Mesozoic section and into the Paleozoic basement, forming features with significant displacement such as the Thouin Graben, Whitetail Graben, Naranco High, and half graben in the Barcoo Sub-basin. Isochore maps reveal two Triassic depocentres separated by an area of thin Triassic extending from the inboard Bedout Sub-basin out to the western Rowley Sub-basin and NE Exmouth Plateau. This new mapping shows that there is a poor correlation between Triassic depocentres and existing basin boundaries.

A new Triassic stratigraphic framework for the region is based on five regional seismic surfaces that define four stratigraphic packages. Fluvio-deltaic, carbonate-siliciclastic plaform, marine mudstone, and volcanic gross depositional facies are distributed among these stratigraphic packages, and constrain the palaeogeographic and structural evolution of the study area. The lower part of the Triassic succession in the Bedout Sub- basin has been identified as Australia’s new offshore oil and gas province. The results from this study help to place recent Bedout Sub-basin discoveries within a regional geological context and will inform future assessments of the hydrocarbon prospectivity across the central North West Shelf.

Your Instructor

Steve Abbott, PhD, PESA
Steve Abbott, PhD, PESA

Steve Abbott earned his qualifications in sedimentary geology from Flinders (Hons, 1987) and James Cook (PhD, 1994) universities. He joined the Energy Systems Branch at Geoscience Australia in 2013, where he works on regional tectonostratigraphic studies of the North West Shelf. Steve’s past roles include mineral exploration (mainly for sedimentary uranium in central Australia), teaching and research (Southern Cross University, James Cook University, and the University of Tasmania), and regional mapping with the Northern Territory Geological Survey. Steve is President of PESA-ACT.

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