The Jurassic-Cretaceous Bight Basin is a large, mainly offshore basin that extends along the southern Australian margin, from the southern tip of Western Australia, across the Great Australian Bight to the western tip of Kangaroo Island.
The basin underlies the continental shelf and slope, including two broad bathymetric terraces, in water depths ranging from less than 200 to over 4000 metres.
The Bight Basin contains a Middle Jurassic to Late Cretaceous sedimentary succession that in the thickest depocentre, the Ceduna Sub-basin, is in excess of 15 km thick. To the east of the main depocentre, a thin Bight Basin succession overlies the western tip of the mostly Proterozoic Polda Basin.
The Bight Basin is overlain unconformably by the dominantly cool-water carbonates of the Cainozoic Eucla Basin. To the south, the uppermost sequences of the Bight Basin onlap highly extended continental crust and rocks of the continent-ocean transition on the abyssal plain between Australia and Antarctica.
Between 1999 and 2003, Geoscience Australia undertook an integrated geological study of the Bight Basin, which resulted in the development of a new chronostratigraphic framework and an improved understanding of the tectonic and depositional history of the basin.
A key component of this study was the sequence stratigraphic and structural interpretation of 8600 line kilometres of newly acquired, high quality, regional 2D seismic reflection data. These investigations revealed that the Late Cretaceous evolution of the basin was dominated by the development of two large progradational delta systems in the Cenomanian and the Late Santonian-Maastrichtian.
The Bight Basin contains a thick, prospective Jurassic-Cretaceous sedimentary section. Recent work by both Geoscience Australia and the petroleum exploration industry has increased our understanding of the structural and stratigraphic development and the range of opportunities available in this frontier basin.
The presence of thick deltaic units and indications of active petroleum systems further enhance its prospectivity. The basin remains one of the least explored passive margins in the world and will require much more exploration to fully assess its potential.
Regional setting map of the Bight Basin.
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