Authors / CoAuthors
Borissova, I. | Colwell, J.B. | Stagg, H.M.J.
Abstract
The Naturaliste Plateau is a large marginal plateau located immediately west of the southwestern tip of the Australian mainland from which it is separated by the N-S trending Naturaliste Trough. It has an area of about 90 000 km2, extending for about 400 km E-W and 250 km N-S in water depths of 2000 to 5000 m. Results of a recent study of the Naturaliste Plateau based on new and reprocessed seismic data and RV Marion Dufresne cruise 110 (1998) dredging results indicate that large parts of the plateau are underpinned by Proterozoic metamorphic basement similar to the Leeuwin Block of southwestern Australia. The Naturaliste Plateau is a structurally complex terrain that was rifted in the Jurassic-Early Cretaceous and modified by volcanism towards the end of the Early Cretaceous. A number of variable-size rift basins are imaged on seismic profiles on the plateau. Most of these basins are half-grabens bounded by steep ENE-trending normal faults that dip S or SE. The basins extend for up to 120 km along strike, and are from 10-30 km wide. The largest basin (the western Mentelle Basin) lies beneath the Naturaliste Trough and contains more than 5 km of sediment. Basin development probably commenced with the N-S oriented Permian intracratonic rifting that characterises the western and northwestern Australian margins. These Palaeozoic structures were then reactivated by the Jurassic to Early Cretaceous rifting that preceded breakup between Greater India, and Australia-Antarctica (A-A). However, this structural fabric has been subsequently overprinted by E-W trending rifting, reflecting the Early Cretaceous stress regime developed leading to the Late Cretaceous breakup of Australia and Antarctica. A large number of smaller E-W trending rift basins formed across the southern part of the Naturaliste Plateau during this time. In the Valanginian the Naturaliste Plateau separated from Greater India along its northern and western margins. This breakup was accompanied by widespread volcanism, which partly overprinted pre-existing extensional structures. The southern margin of the plateau was formed during the Late Cretaceous A-A breakup which is interpreted to have commenced in the Santonian with a phase of very slow-spreading. A deep-seismic line extending south from the Naturaliste Plateau across the Diamantina Zone imaged a broad (250 km wide) structurally complex zone, which has been interpreted as a continent-ocean transitional zone. The inboard part of this zone appears to contain a mixture of magmatic and continental crust, while further oceanward, it is dominated by peridotite ridges alternating with basaltic intrusions, producing the characteristic rough bathymetry of the Diamantina Zone. This crust could be alternatively interpreted as an ultra-slow spreading crust or highly extended continental crust with partly unroofed mantle and it is significantly different from the slow-spreading crust described on the southern Australian margin
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nonGeographicDataset
eCat Id
60487
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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- External PublicationAbstract
- ( Theme )
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- sedimentary basins
- ( Theme )
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- continental margins
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2003-01-01T00:00:00
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