--> Abstract: The Complex History of the Shipwreck Fault Zone, Otway Basin, Southeast Australia—A Transfer Fault within an Oblique Rift Setting, by Craig L. Schneider, Kevin C. Hill, and Nick Hoffman; #90039 (2005)

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The Complex History of the Shipwreck Fault Zone, Otway Basin, Southeast Australia—A Transfer Fault within an Oblique Rift Setting

Craig L. Schneider1, Kevin C. Hill2, and Nick Hoffman3
1 The University of Melbourne, Melbourne, Australia
2 School of Earth Sciences, Melbourne, Australia
3 3D-Geo, Melbourne, Australia

The north-south trending Shipwreck Trough lies within the west-northwest trending Otway Basin, southeastern Australia, and is the location of numerous recent gas discoveries including Thylacine, Geographe, and Casino (> 2.5 TCF combined OGIP). The Otway Basin is one of several rift basins that formed during the Late Jurassic–Paleocene separation of the Australian and Antarctic continental plates. The Shipwreck Trough formed in response to a Late Cretaceous basin reorganization in which rift propagation shifted from eastward to southward creating a left-lateral oblique margin.

The Shipwreck Fault Zone (SFZ), is a left-lateral oblique fault system that forms the eastern structural margin of the Shipwreck Trough. Within the Shipwreck Trough, the predominant fault strike is west-northwest, consistent with north-northeast–south-southwest extension. However, at the eastern margin of the trough, most faults tip-out or merge into the north-northwest trending SFZ. The angle between the presumed extension direction and the SFZ (a) is 25°. The SFZ shows both positive and negative flower structure morphology and rhomb-shaped depocenters.

Basement topography plays a central role in the establishment of this strike- to oblique-slip transfer fault system. Although the SFZ is located over and sub-parallel to pre-existing Early Cretaceous, basement-involved structures, it and adjacent normal faults appear to be detached within the Early Cretaceous rift sequence.

Hydrocarbon traps adjacent to the SFZ display a spectrum of distributed and focused structural styles, including normal fault blocks, accommodation zones between normal fault sets, and minor transpressive inversion anticlines, collectively highlighting the complex structural evolution of this oblique rift margin.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005