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A new sequence stratigraphic framework has been developed for the Otway Basin based on the interpretation and integration of offshore wells, key onshore wells, new biostratigraphic results and a regional grid of 2D seismic data. In the new tectonostratigraphic framework, seven major basin phases and their eight component supersequences are recognised as follows: 1) Tithonian?-Barremian rifting of the Crayfish Supersequence 2) Aptian-Albian post-rift deposition of the Eumeralla Supersequence 3) mid-Cretaceous compression and inversion 4) Late Cretaceous rifting of the Shipwreck and Sherbrook Supersequences 5) latest Maastrichtian to Middle Eocene basin reorganisation and early thermal subsidence of the Wangerrip Supersequence 6) local inversion and thermal subsidence of the Nirranda Supersequence (Middle Eocene to Early Oligocene) followed by thermal subsidence and progressive compression of the Heytesbury Supersequence (Late Oligocene to Late Miocene) leading to Late Miocene uplift and erosion and 7) Plio-Pleistocene deposition of the Whalers Bluff Supersequence. Basin phases are distinguished by their different tectonic driving mechanisms as the primary control on the creation of accommodation space. The supersequences are bounded by regional unconformities and define major episodes of sedimentation within each basin phase. Supersequences are related to second-order transgressive-regressive cycles within the basin and are regionally mappable. The new sequence stratigraphic framework is then used as the basis for correlation to deep-water regions where well-control is limited or absent. The framework is also used to help place existing, complex, facies-dependent lithostratigraphic schemes into depositional and petroleum systems context.

The Bass Basin is a moderately explored Cretaceous to Cainozoic intracratonic rift basin on Australia?s southeastern margin. A basin-wide integration of seismic data, well logs, biostratigraphy and sequence stratigraphy has resulted in the identification of six basin phases and related megasequences/ supersequences. These sequences correlate to three periods of extension, a rift-transition phase, and two subsidence phases. The complex nature of facies relationships across the basin is attributed to the (mostly) terrestrial setting of the basin until the Middle Eocene, multiple phases of extension, strong compartmentalisation of the basin due to underlying basement fabric, and differential subsidence during extension and early subsidence phases. Evidence of the initial rift phase (Otway Megasequence) is only clearly observed in the Durroon Sub-basin and in the southwestern Cape Wickham Sub-basin. The second rift phase (Durroon Megasequence) is pervasive throughout the Bass Basin, although a full succession of this megasequence was only penetrated in the Durroon Sub-basin. The third-rift phase (Bass Megasequence) is also pervasive throughout the basin, but appears to have affected only particular depocentres such as the Pelican, Cormorant and Yolla troughs. Here, expanded syn-tectonic growth sections have been intersected. There is wide variation in facies type, environment and thickness of the Bass Megasequence due to differential rates of subsidence. Three component sequences have been recognised within the Bass Megasequence (Furneaux, Tilana and Narimba sequences), with each component sequence correlated to discrete periods of increased accommodation. The shift from rift-to-post-rift conditions (Aroo Megasequence) was signaled by waning subsidence rates and an increasing brackish influence. A wide variation in facies types, environments and thicknesses is also observed. The frequency and thickness of coals began to increase during the deposition of this megasequence, lasting from Early Eocene until the mid-Middle Eocene. A slowdown in subsidence rates allowed the aggradation of coaly facies (many geochemically characterised as ?hydrogen-rich?), indicating there was a balance between accommodation, sediment supply and peat production. The most important sequences for petroleum generation and trapping are the Bass and Aroo megasequences. Most of the coaly source rocks now typed to liquid hydrocarbon generation were deposited during the period of late Early Eocene to Middle Eocene rift-transition phase. The critical factor in sourcing accumulations from the coaly succession appears to be effective primary and secondary expulsion from the source rock and the volume of charge. Biostratigraphic studies have identified lacustrine cycles during the Late Cretaceous to Middle Eocene, with geological evidence indicating these lakes developed during times of increased accommodation. Lacustrine shales are likely to be more important as seal facies, rather than as potential source rocks. The Middle Eocene (Demons Bluff Sequence) and younger marine successions (Torquay Sequence) show low source potential and do not lie within the oil window. Optimal conditions for seal deposition occurred during lacustrine cycles in the Late Cretaceous to Early Eocene, and the mid-Eocene. Untested plays include reservoir/seal pairs associated with seven maximum flooding events in the western Bass Basin. The petroleum systems elements of the Durroon Sub-basin differ significantly from the Cape Wickham Sub-basin owing to the cessation of tectonically-driven subsidence in the eastern Bass Basin (Durroon Sub-basin) from the mid-Campanian onward.

A prospectivity assessment of the offshore northern Perth Basin, Western Australia, was undertaken as part of the Australian Goverment's Offshore Energy Security Program.

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The North Australian Basins Resource Evaluation was a multidisciplinary project. Its aim was to provide the mineral exploration industry with a predictive chronostratigraphic basin framework in northern Australia. The project was a collaborative venture of the Commonwealth, Queensland and Northern Territory Governments, funded under the National Geoscience Mapping Accord. Industry collaboration provided access to confidential drill core and regional geophysical datasets.

Legacy product - no abstract available

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. Although the basin is being tested by new drilling it remains one of the least explored passive margins in the world, and will require much more exploration to fully assess its potential.

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