Print this pageStructural Geology and Evolution of the Shipwreck Trough, East-Central Otway Basin, Southeastern Australia
Craig
L. Schneider
School of Earth Sciences,
The University of Melbourne
Melbourne, Australia
[email protected]
The Otway Basin is one of a series of east-west to northwest trending rift basins that formed during the Early Cretaceous–Eocene, north–south separation of the Australian and Antarctic continental plates. During the Late Cretaceous, the rift architecture changed within the Otway Basin as rift propagation shifted from eastward to southward. This shift caused the abandonment of the Bass Basin rift segment to the east and the creation of a northwest trending, left-lateral-oblique rift margin. The Shipwreck Trough, a north-south trending depocentre in the east-central Otway Basin, marks the location of this fundamental shift in the basin architecture. Growth fault geometries and growth sediment sequences preserved within the Shipwreck Trough record the evolution from orthogonal to oblique rifting.
Detailed mapping of 3D seismic surveys (~1200 km2) within the Shipwreck Trough shows that the overall east-west trending Early Cretaceous rift system is composed of variably oriented rift segments that appear to reflect the structural fabric of the pre-rift Palaeozoic basement. Late Cretaceous faults are primarily northwest-oriented and are largely detached within Early Cretaceous sedimentary sequences. However, the location of fault tips and accommodation/transfer zones is controlled by the underlying basement topography. The Shipwreck Fault Zone, the primary accommodation/transfer zone that forms the eastern boundary of the Shipwreck Trough, exhibits Cenomanian–Maastrichtian flower structures and rhomb-shaped depocentres, attesting to a left-lateral strike-slip component of extension. 3D reconstruction of this transfer zone will further our understanding of the relative role of orthogonal versus oblique-slip faults in the evolution of oblique rift margins.
AAPG Search and Discovery Article #90033©2004 AAPG Foundation Grants-in-Aid