Authors / CoAuthors
Lane, H.
Abstract
The formation of passive margins has been intensively studied on the Iberian-Newfoundland margins for over two decades leading to complex models for the formation of conjugate nonvolcanic rifted margins. The main area of debate is focussed on deciphering the nature of the so-called transitional zone between unambiguous continental and oceanic crust. The transitional zone often displays characteristics of both continental and oceanic crust. The Great Australian Bight and Wilkes Land margins are type-examples of conjugate nonrifted volcanic margins, but much less well studied than the Iberian-Newfoundland margins. Research along the Southeast Indian Ocean margins has been propelled by Australia's submission to the United Nations Convention of the Law of the Sea, yet the study of the margins has been limited to research on particular regions on either the Australian or Antarctic margins. No consistent stratigraphy has been derived that would allow a unified study of this margin pair. This thesis uses seismic and potential field data to provide a consistent interpretation across the two margins in terms of sedimentary sequences and crustal structure for the first time. The interpretation of both margins provides insight into the nature and formation of the transitional zone. A new sequence stratigraphy for the Wilkes Land margin has been developed to correlate with the interpretation of Totterdell et al. (2000) along the Great Australian Bight margin. Combined with the crustal structure classification of Leitchenkov et al. (2007) a revised model for the breakup and formation of the transitional zone was developed. The formation of the transitional zone is interpreted to be the result of extension of the two plates and the successive breakup of continental crust and mantle followed by the emplacement of oceanic mantle, initially without the formation of oceanic crust. The presence of the Moho within the seismic data shows that the transitional zone is underlain by mantle rocks. Continental mantle is interpreted to be exhumed to form prominent basement highs on both margins. Seaward of these highs, the change in basement architecture and the presence of magnetic anomaly 34 (83Ma) is interpreted to correlate with the juxtaposition of continental mantle and the emplacement of oceanic mantle. This is consistent with well subsidence data from Totterdell et al. (2000) which shows a change in the rate of subsidence at this time. The location of the Transitional Zone-Ocean Boundary (TZOB) and Transitional Zone- Continent Boundary (TZCB) are repositioned as a result of this study. The TZOB is located further landward of previous interpretations by Sayers et al. (2001) and Colwell et al. (2005). The interpretation of the transitional zone being underlain by mantle rocks renders the term Continent-Ocean Boundary (COB) invalid as, continental crust is not found immediately next to oceanic crust.
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nonGeographicDataset
eCat Id
76877
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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- Resource
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2008-01-01T00:00:00
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