Victoria’s Proterozoic basement controls the distribution of its southern margin petroleum basins
David Taylor A and David Moore AGeoscience Victoria GPO Box 4440 Melbourne VIC 3001
The APPEA Journal 49(2) 581-581 https://doi.org/10.1071/AJ08054
Published: 2009
Abstract
There are three petroleum basins of differing character off the Victorian coast: the Otway, Bass and Gippsland basins. These formed during continental rifting between Australia, Antarctica and New Zealand, associated with the break up of Gondwana Marked variation in the development of these basins appears to have been largely controlled by the distribution of Proterozoic basement—the Selwyn Block—under central Victoria. Lying deep under central Victoria, this block surfaces towards the coast and continues southward as the Proterozoic crust of western Tasmania. The boundaries of this block are coincident with the boundaries separating the three basins.
The Otway Basin in western Victoria represents a clean break between Australia and Antarctica. The Otway Basin has thick fill upon thinned continental crust with an outboard break to a continent-ocean boundary. The overall geometry here is a classic lower plate margin.
This clean continental break-up failed to propagate eastward across the Proterozoic Selwyn Block. Instead, localised continental stretching resulted in some grabens and the overlying steers head sag of the Bass Basin. True continental separation was transferred southward to the margin of the Tasmania/Selwyn Block.
The Gippsland Basin lies east of the Selwyn Block. Its development reflects initial southern margin rifting, but this was overtaken by orthogonal-oriented Tasman rifting. This left the Gippsland Basin with a complex interplay of north-south and east-west structures controlling the platforms, terraces and deeps.
keywords: Bass Basin, Otway Basin, Gippsland Basin, Tasman rifting, southern rifting, Proterozoic basement, Victoria, Tasmania, Gondwana break-up
David Taylor graduated from Monash University in 1992 with a MSci. Since that time he has worked as a State Government geologist in Victoria, which involved new generation field mapping of the Palaeozoic bedrock geology right across Victoria. This work resulted in numerous reports and maps, with highlights being the recognition of a new metamorphic complex in western Victoria and the presence of Proterozoic basement in central Victoria. David then transferred his regional mapping expertise to the Energy Group to work on the basin structures and the geothermal potential of Victoria. David has published numerous articles and discussions on the tectonic evolution and geodynamic framework of Victoria. david.taylor@dpi.vic.gov.au |
David Moore has worked for about 40 years as a geologist in both the mining and exploration and government sectors. Over the last 20 years he has been interpreting geophysical data in geologically meaningful ways, with an emphasis on highlighting potentially prospective areas. For the last 13 years he has been with GeoScience Victoria, working mainly in western and central Victoria’s Murray, Gippsland and Otway basins, interpreting their Palaeozoic basements. David.Moore@dpi.vic.gov.au |
References
Cayley, R.A., Taylor, D.H., Vandenberg, A.H.M., and Moore, D.H. (2002). Proterozoic—Early Palaeozoic rocks and the Tyennan Orogeny in central Victoria: The Selwyn Block and its tectonic implications Australian Journal of Earth Sciences 49, 225–54.Cummings, A.M., Hillis, R.R., and Tingate, P.R. (2004). New perspectives on the structural evolution of the Bass Basin: implications for petroleum prospectivity EABS 2, 133–49.
Lister, G.S., Etheridge, M.A., and Symonds, P.A. (1991). Detachment models for the formation of passive continental margins Tectonics 10, 1038–64.
Norvick, M.S., and Smith, M.A. (2001). Mapping the plate tectonic reconstruction of southern and southeastern Australia and implications for petroleum systems APPEA Journal 41, 15–34.
Teasdale, J.P., Pryter, L.L., Stuart, Smith P.G., Romine, K.K., Etheridge, M.A., Loutit, T.S., and KYAN, D.M. (2003). Structural framework and basin evolution of Australia’s southern margin APPEA Journal 43, 13–37.
