Structural Framework and Basin Evolution of Australia’s Southern Margin

Abstract

The structural evolution of all of the Southern Margin Basins can be explained by episodic reactivation of basement structures in respect to a specific sequence of tectonic events. Three geological provinces dominate the basement geology of the Southern Margin basins. The Eyre, Ceduna, Duntroon and Polda Basins overlie basement of the Archean to Proterozoic Gawler-Antarctic Craton. The Otway and Sorell Basins overlie basement of the Neoproterozoic-early Palaeozoic Adelaide- Kanmantoo Fold Belt. The Bass and Gippsland Basins overlie basement of the Palaeozoic Lachlan Fold Belt. The contrasting basement terranes within the three basement provinces and the structures within and between them significantly influenced the evolution and architecture of the Southern Margin basins.The present-day geometry was established during three Mesozoic extensional basin phases:Late Jurassic–Early Cretaceous NW–SE transtension forming deep rift basins to the west and linked pullapart basins and oblique graben east of the Southwest Ceduna Accommodation Zone; Early–Mid Cretaceous NE–SW extension; and Late Cretaceous NNE–SSW extension leading to continental breakup. At least three, potentially trap forming, inversion events have variably influenced the Southern Margin basins; Mid Cretaceous, Eocene, and Miocene-Recent. Volcanism occurred along the margin during the Late Cretaceous and sporadically through the Tertiary.First-order structural control on Mesozoic rifting and breakup were east–west trending basement structures of the southern Australian fracture zone. Second-order controls include:Proterozoic basement shear zones and/or terrane boundaries in the western Gawler Craton, which controlled basin evolution in the Eyre and Ceduna Subbasins; Neoproterozoic structures, which significantly influenced basin evolution in the Ceduna sub-basin; Cambro-Ordovician basement shear zones and/or terrane boundaries, which were a primary control on basin evolution in the Otway and Sorell Basins; and Palaeozoic structures in the Lachlan Fold Belt, which controlled basin evolution in the Bass and Gippsland Basins.A SEEBASE™ (Structurally Enhanced view of Economic Basement) model for the Southern Margin basins has been constructed to show basement topography. When used in combination with a rigorous interpretation of the structural evolution of the margin, it provides a foundation for basin phase and source rock distribution, hydrocarbon fluid focal points and trap type/distribution.

Site U1512

“…Since 2000, SRK Consulting has undertaken a number of SEEBASE™ projects on Southern Margin basins for a range of government and industry clients (e.g., SRK Consulting, 2001. In 2003/4, SRK Consulting undertook a 'stitch' of all previous SEEBASE projects along the Southern Margin for Geoscience Australia (Teasdale et al, 2003;Teasdale, 2004).…”

Early opening of Australia and Antarctica: New inferences and regional consequences

“…Considering the sedimentary basins and the fault distribution over South-eastern Australia (e.g. Teasdale et al, 2003), such a large WNW-ESE motion seems unlikely, because all basins along the margin and in the Bass Strait display a NE-SW extension. We rather consider a different, more complicated history for the whole area.…”

“…The central section is characterized by the presence of the Polda Trough which divert from the Australian margin within the Australian continent. The Polda Trough is part of a set of East-West structures known collectively as the "Southern Australian Fracture Zone", which extend across the south-eastern margin of Australia through the Robe Trough, the Otway and Gippsland basins (Teasdale et al, 2003). Although reactivating older structures, it is reported to have been mostly active during the (Late) Jurassic, accommodating NW-SE extension.…”

“…3-a) was affected by extension along the Southern Australian Fracture Zone, extending E-W from the Southern Perth Basin through the Great Australian Bight to the northern margin of the Otway and Gippsland basins (Teasdale et al, 2003) and finally the Bellona Trough. As a consequence of this extension, East Antarctica started to drift southeastward relative to Australia at an ultraslow rate (assumed to remain constant at 11 km/Ma full rate).…”

Fault-related biogenic mounds in the Ceduna Sub-basin, Australia. Implications for hydrocarbon migration

“…1) is a large, mainly offshore basin along the continental margin of southern Australia which resulted from the separation of Australia and Antarctica (e.g. Veevers, 1986;Teasdale et al, 2003). The basin underlies the continental shelf and slope in water depths ranging from less than 200 m to over 4000 m. The main depocentres (including the Ceduna Sub-basin) occur in the eastern part of the Bight Basin and is potentially one of the most prospective deep-water frontier area in offshore Australia (Totterdell and Mitchell, 2009).…”