A New Sequence Framework Forthe Great Australian Bight: Starting With a Clean Slate

Abstract

The 1999 release of offshore petroleum exploration acreage in the Great Australian Bight and the acquisition of high quality seismic datasets covering the Bight and Duntroon Basins, have provided a timely opportunity to reassess the stratigraphic and tectonic evolution of the area. A sequence stratigraphic framework for the Great Australian Bight region has been developed based on the interpretation of exploration wells in the Bight and Duntroon basins and a grid of new and reprocessed seismic data in the Bight Basin. Previous formation-based nomenclature has emphasised lithostratigraphic correlations rather than the chronostratigraphic relationships. The new sequence framework underpins an analysis of play elements and petroleum systems and is helping to identify new exploration opportunities.Deposition in the Bight and Duntroon Basins commenced in the Late Jurassic during a period of lithospheric extension. Extensive half graben systems were filled with fluvial and lacustrine clastic sediments (Sea Lion and Minke supersequences). Potential source rocks within these supersequences are immature at Jerboa-1 in the Eyre Sub-basin, however higher maturities are expected within adjacent half graben and in the Ceduna and Recherche Sub-basins. The syn-rift successions are overlain by widespread Berriasian to Albian fluvio-lacustrine to marine sediments of the Southern Right and Bronze Whaler supersequences. The onlapping sag-fill geometry of these Early Cretaceous packages in the Eyre, Ceduna and inner Recherche Sub-basins suggests that they were deposited during a period of thermal subsidence.Accelerated subsidence commencing in the late Albian led to the deposition of the marine shales of the Blue Whale supersequence, followed by a period of gravity-controlled faulting and deformation in the Cenomanian. The White Pointer supersequence is characterised by growth strata associated with a series of listric faults that sole out in underlying ductile shales of the Blue Whale supersequence. Open marine conditions during the Turonian-Santonian (Tiger supersequence) were followed by the development of massive shelf margin delta complexes in the late Santonian-Maastrichtian (Hammerhead supersequence). The progradational to aggradational stratal geometries within the Hammerhead supersequence suggest initial high rates of sediment input that subsequently waned during this period. An overall transgressive phase of sedimentation in the Early Tertiary (Wobbegong supersequence) was followed by the establishment of open marine carbonate shelf conditions from the Early Eocene onward (Dugong supersequence). Organic geochemical studies show that the Bronze Whaler to White Pointer supersequences have good source rock potential in the relatively proximal facies intersected by existing petroleum exploration wells. Our sequence stratigraphic model predicts the likelihood of widespread late Aptian, Albian, Cenomanian-Santonian, and Campanian marine shales, which underpin four potential marine petroleum systems.

A tectonic model reconciling evidence for the collisions between India, Eurasia and intra-oceanic arcs of the central-eastern Tethys

“…6c), until mid-Cretaceous time, when the arm between India and Argoland was abandoned (Gibbons et al, 2012b). Seafloor spreading between Australia and Antarctica slowly initiated from 83 Ma (chron 34) (Mutter et al, 1985), following rifting that probably initiated as early as 160 Ma (Totterdell et al, 2000) and experienced two significant changes in direction at 100 Ma and 50 Ma (Veevers, 2000;Whittaker et al, 2007;Whittaker et al, 2013). Greater India also began to separate from Madagascar from Albian-Cenomanian time (Fig.…”

Re-evaluation of the Mentelle Basin, a polyphase rifted margin basin, offshore southwest Australia: new insights from integrated regional seismic datasets

“…Subsequent to the establishment of the Eocene fast spreading, Australia's southern margin became a stable trailing margin (Totterdell et al, 2000). Miocene to Holocene deposits form a thin (200 ms TWT) veneer across the Mentelle Basin and Naturaliste Plateau and are interpreted to have been deposited on the stable trailing margin.…”

“…Syn-rift successions were deposited in the SRS at this time (Totterdell et al, 2000) and on the Naturaliste Plateau (Burkle, 1967;Borissova, 2002).…”

Fault-related biogenic mounds in the Ceduna Sub-basin, Australia. Implications for hydrocarbon migration

“…The most prospective petroleum systems are believed to be associated with thick Mid to Late Cretaceous deltaic and marine siliciclastic sediments, which provide reservoirs, seals and potential oil-prone source rocks at several stratigraphic levels (Fig. 3, Blevin et al, 2000;Totterdell et al, 2000;Struckmeyer et al, 2001).…”