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ABSTRACT: Tectonics and play fairways in Bass Strait, Australia

Power, Michael, Daniel Palmowski, Kevin Hill, Nick Hoffman, and Martin Norvick , La Trobe 3D-GEO, Bundoora, Australia

In the Otway and Gippsland Basins along Australia's SE margin, major extension was initiated by Late Jurassic to Mid Cretaceous oblique rifting of Australia from Antarctica. In the Otway Basin, extension proceeding to Southern Ocean spreading, occurred in the Mid to Late Cretaceous along a north-dipping moho-detachment, leaving only 2-3 km of pre-Mesozoic crust. In the Gippsland Basin aulacogen, however, initial rifting was associated with a south-dipping crustal-scale décollement leading to 75% extension and 10km of syn-rift subsidence. Early Cretaceous rifting failed in the Gippsland Basin, as Late Cretaceous Tasman Sea spreading changed the extension vector to a south-easterly direction.

Both basins contain clear signatures of tectonic events and plate reorganisations within the Indonesian archipelago. In the Mid Tertiary, Australia's northern margin collided with island arcs in Timor and New Guinea and compressional stress was transmitted to the Southern Margin causing inversion and trap formation along the basin margins.

In the Gippsland Basin, deposition of deltaic source and reservoir rocks occurred from Late Cretaceous till Early Tertiary. The Mid Tertiary inversion resulted in the formation of structural traps. Middle to Late Tertiary regional post-rift subsidence in the eastern Gippsland Basin led to hydrocarbon generation. While early exploration was concentrated on structural traps at the top of the Latrobe Group, exploration is now directed towards intra-Latrobe Group, and in deeper-water plays.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia