Basin Details and Geological Overview
The Naturaliste Plateau is one of several large submarine plateaus off Western Australia. It has an area of about 90 000km2 and lies in water depths of 2000 to 5000 metres. The plateau has a roughly rectangular shape, extending about 400 km E-W and 250km N-S. The plateau is bordered by the Perth Abyssal Plain in the north and west, the Australian-Antarctic Basin in the south and the Mentelle Basin in the east. The eastern half of Naturaliste Plateau lies within Australia's Exclusive Economic Zone and the western half within the 'extended Continental Shelf (see Figure 1).
Seismic surveying and drilling on the Naturaliste Plateau took place mostly in the early 1970s (see Figure 1). Deep Sea Drilling Project (DSDP) wells (sites 258 and 264) recovered a succession of Cretaceous to Miocene sedimentary rocks. Neither of the wells reached basement, however, volcaniclastic conglomerates of Cenomanian or older age recovered at DSDP site 264 lie close to acoustic basement. A cobble from this conglomerate is composed of altered tholeiites, which was interpreted as evidence for the oceanic origin of the plateau. Dredge sampling on the steep southern flank of the plateau by Marion Dufresne in 1998 and Southern Surveyor in 2005 recovered a number of Cambrian granite and orthogneiss samples. The current viewpoint is that the whole or at least a large part of the Naturaliste Plateau is underpinned by the continental basement.
Seismic data acquired over the Naturaliste Plateau is sparse and comprises Continental Margins (1972) and Petrel (1973) survey records. It shows that most of the plateau is covered by several hundred metres of predominantly Cainozoic sediments. Some seismic lines intersected small rift basins filled with up to 2.5 km of sediment. Correlation to Ocean Drilling Program (ODP) wells suggests that the upper sedimentary fill in these basins is Cretaceous, however, the age of older sequences is currently unknown. These older sequences are >1km thick may comprise Jurassic to Lower Cretaceous strata (Borissova, 2002).
- ProvExplorer - Naturaliste Plateau Details and Geological Overview
The Naturaliste Plateau is a structurally complex fragment of continental crust rifted in the Jurassic-Early Cretaceous and modified by volcanism towards the end of the Early Cretaceous. The basement of the southern Naturaliste Plateau is faulted and more eroded in comparison to its northern part. A number of variable size rift basins are imaged on seismic profiles. Most of the individual rift basins are half-graben bounded by steep ENE oriented normal faults dipping S or SE (see Figure 2). The basins are 10 to 30 km wide and up to 120 km long.
The largest basin is located in the southeastern part of the plateau and consists of several en-echelon rift segments. A few smaller NE-trending rift basins are located along the northern flank of the plateau. The northwestern part of the Naturaliste Plateau is dominated by a large circular topographic high. In the absence of the seismic data this feature was interpreted as a volcanic complex.
Stratigraphy of the Naturaliste Plateau and surrounding areas is based on the two DSDP holes (Sites 258 and 264) combined with information from the dredged and cored seabed samples. The tectonostratigraphic chart (see Figure 3) correlates mapped seismic sequences, drilled stratigraphy and regional tectonic events.
Petroleum Systems and Hydrocarbon Potential
Based on the existing seismic data small rift basins mapped on the Naturaliste Plateau are interpreted to contain up to 2.5 km of Late Jurassic to Early Cretaceous sediments (see Figures 5a and 5b). This sediment thickness is likely to be insufficient for source socks (if present) to become mature and generate hydrocarbons. The current viewpoint is that these basins are not prospective for hydrocarbons. However, if modern seismic data is collected and the sediment fill in these basins prove to be significantly thicker, the prospectivity assessment will need to be revised.
The eastern part of the Naturaliste Plateau is adjacent to the western Mentelle Basin. Recent petroleum prospectivity assessment of the Mentelle Basin has shown that potential source rocks in the western Mentelle Basin generated hydrocarbons and there are a number of structural and stratigraphic traps that may contain accumulations.
|Author(s) ||Year ||Title |
|Beslier, M.-O., Royer, J.Y., Girardeau, J., Hill, P.J., Boeuf, E., Buchanan, C., Chatin, F., Jacovetti, G., Moreau, A., Munschy, M., Partouche, C., Robert, U., and Thomas, S.||2004||A wide ocean-continent transition along the southwest Australian margin: First results of the MARGAU/MD110 cruise: Bulletin de la Société Géologique de France, v. 175, p. 629–641|
|Borissova, I.||2002||Geological framework of the Naturaliste Plateau. Geoscience Australia Record 2002/20|
|Coleman, P.J., Michael, P.J. and Mutter, J.C.||1982||The origin of the Naturaliste Plateau, SE Indian Ocean; implications from dredged basalts. Journal of the Geological Society of Australia, 29(4), 457-468|
|Chatin, F., Robert, U., Montigny, R. and Whitechurch, H.||1998||La Zone Diamantine (ocean Indien oriental) temoin de la separation entre l"Australie and lAntarctique: arguments petrologique et geochimique, C. R. Acad. Sci. Paris, 326, 839-845|
|Coleman, P.J., Michael, P.J. and Mutter, J.C.||1982||The origin of the Naturaliste Plateau, SE Indian-Ocean—Implications from dredged basalts: Geological Society of Australia Journal, v. 29, p. 457–468|
|Crawford, A.J., Direen, N.G., Coffin, M.F., Cohen, B., Paul, B. and Mitrovic, L.||2006||Extensive basaltic magmatism on the Naturaliste Plateau, offshore SW Australia. Geochimica et Cosmochimica Acta, 18, A116|
|Direen, N.G., Borissova, I., Stagg, H.M.J., Colwell, J.B. and Symonds, P.A.||2007||Nature of the continent-ocean transition zone along the southern Australian continental margin: a comparison of the Naturaliste Plateau, SW Australia, and the central Great Australian Bight sectors, in Karner, G.D., et al., eds., Imaging, mapping and modelling continental lithosphere extension and breakup, Volume 282: London, Geological Society Special Publication, p.235-261|
|Halpin, J.A., Crawford, A.J., Direen, N.G., Coffin, M.F., Forbes, C.J. and Borissova, I.||2008||Naturaliste Plateau, offshore Western Australia: A submarine window into Gondwana assembly and breakup. Geology, 36(10), 807–810|
|Hayes, D.E., Frakes, L.A. and Barrett, P.J.||1975||Initial reports of the Deep Sea Drilling Project, Leg 28: Washington, D.C., U.S. Government Printing Office|
|Munschy, M.||1998||The Diamantina Zone as the result of rifting between Australia and Antarctica: Geophysical constraints.: La zone de Diamantine, temoin de la separation de l'Australie et de l'Antarctique: Arguments geophysiques. C. R. Acad. Sci. Paris, 327(8), 533-540|
|Stagg, H.M.J., Colwell, J.B., Borissova, I., Ishihara, T. and Bernardel, G.||2006||The Bruce Rise Area, East Antarctica: Formation of a Continental Margin near the Greater India - Australia - Antarctica Triple Junction. Terra Antarctica, 13 (1/2), 3–22|
|Storey, M., Kent, R.W., Saunders, A.D., Salters, V.J., Hergt, J., Whitechurch, H., Sevigny J.H., Thirlwall, M.F., Leat, P., Ghose, N.C. and Gifford, M.||1992||Lower Cretaceous volcanic rocks on continental margins and their relationship to the Kerguelen Plateau. IN: Wise, et al. Proceedings of the Ocean Drilling Program, Scientific Results, Leg 120, Texas A&M University, College Station, 33-53|