Basin Outline
The Carnarvon Basin is the southernmost component of the Late Paleozoic to Cenozoic Westralian Superbasin that underlies the northwestern continental margin of Australia from North West Cape in the south to the Arafura Sea in the north. The basin can be divided into northern and southern components. The offshore Northern Carnarvon Basin covers approximately 535000 km2 with water depths up to 3500 m and comprises up to 15000 m of largely Mesozoic sedimentary rocks. The Southern Carnarvon Basin consists of Paleozoic depocentres, with Permian to Ordovician strata being exposed onshore.
The offshore part of the Northern Carnarvon Basin evolved from a pre-rift, predominantly sag-type basin in the Late Paleozoic, through a tectonically active period of syn-rift sub-basins in the Jurassic, to a passive margin carbonate shelf in the from the Late Cretaceous (Figure 1 [PDF, 180KB]). The geological evolution of the basin has been discussed in detail by many authors, and the summary presented below is derived from the work of Kopsen and McGann (1985), Boote and Kirk (1989), Hocking (1990), Jablonski (1997), Westphal and Aigner (1997), Tindale et al (1998), Bussell et al (2001), Norvick (2002) and Longley et al (2002).
The offshore part of the Northern Carnarvon Basin comprises the inboard Exmouth, Barrow, Dampier and Beagle sub-basins, and outboard the Exmouth Plateau, including the Rankin Platform, Kangaroo Syncline and Wombat Plateau (Figure 2 [PDF, 582KB]). The tectonic elements of the region are dominated by a northeasterly trend that developed as a result of rift tectonism initiated in the Early Jurassic and continuing until the Late Jurassic. Proximal basin-bounding faults are similarly oriented, and subsequent tectonic movements have variably inherited this structural alignment. The last major rift-related tectonism occurred in the Valanginian, preceding the final continental separation of Greater India from Australia .
As a result of the Jurassic and Early Cretaceous rift tectonism, the Barrow and Dampier sub-basins formed a northeast-trending graben, bounded on the distal side by the buried fault escarpment of the Rankin Platform and the Exmouth Plateau. The oceanic crust of the Argo, Cuvier and Gascoyne abyssal plains bound the distal area of the Exmouth Plateau and the Exmouth Sub-basin.
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