Basin Outline
The Bonaparte Basin is located predominantly offshore (Figure 1 [PDF, 602KB]) and covers an area of approximately 270,000 km2 of Australia's northwest continental margin. The basin contains up to 15000 m of Phanerozoic marine and fluvial siliciclastics and marine carbonates. The regional geology, structural evolution and petroleum potential have been described by Laws and Kraus (1974), Gunn (1988), Lee and Gunn (1988), Gunn and Ly (1989), MacDaniel (1988), Mory (1988, 1991), Botten and Wulff (1990), Petroconsultants Australasia Pty Ltd (1990), Hocking et al (1994), Woods (1994), and summarised by Longley et al (2002) and Cadman and Temple (2004). Numerous papers on the petroleum geology of the region are presented in the Proceedings of the Timor Sea Symposium, Darwin, June 2003 (Ellis et al, 2004).
The Bonaparte Basin is bounded to the northwest by the Timor Trough, where water depths exceed 3000 m. In the northeast, beyond the limits of the Darwin Shelf, the basin adjoins the Arafura and Money Shoal basins. To the southwest, it is contiguous with the Browse Basin.
The Bonaparte Basin is structurally complex and comprises a number of Paleozoic and Mesozoic sub-basins and platform areas (Figure 1 [PDF, 602KB]). The basin developed during two phases of Paleozoic extension, followed by Late Triassic compression, and then further extension in the Mesozoic that culminated in the breakup of Gondwana in the Middle Jurassic (O'Brien et al, 1993). Convergence of the Australia-India plate and Southeast Asian microplates in the Miocene to Pliocene resulted in flexural downwarp of the Timor Trough and widespread fault reactivation across the western Bonaparte Basin.
The Petrel Sub-basin is a northwest-trending Paleozoic rift in the eastern portion of the Bonaparte Basin. The sub-basin contains a thick section of mostly Paleozoic and thinner Mesozoic sediments, and is underlain by Proterozoic crystalline basement (dolerite in wells) and sediments of the Proterozoic Kimberley Basin (Colwell and Kennard, 1996). The eastern and southwestern margins of the sub-basin are flanked by platforms of relatively shallow basement and thin sediment cover. Sedimentation in the sub-basin commenced in the Cambrian, and northeast-trending rifting was initiated in the Late Devonian to Early Carboniferous. Offshore, the Petrel Sub-basin is orthogonally overprinted by a northeast-trending structural grain that resulted from Late Paleozoic and Mesozoic rifting.
The Malita Graben and Calder Graben form a major northeast-trending rift system that lies between the Petrel Sub-basin and the Sahul Platform. The graben contains a thick succession of Late Paleozoic, Triassic, Jurassic and Early Cretaceous sediments.
The Sahul Platform, which underlies most of the Joint Petroleum Development Area (JPDA), is an area of relatively shallow basement. The Permo-Triassic succession in this area was uplifted to form a structural high during Jurassic extension of the adjacent Malita and Calder graben.
The Vulcan Sub-basin is a major northeast-trending Late Jurassic rift depocentre in the western part of the Bonaparte Basin. It is flanked to the southeast and northwest by Permo-Triassic platforms; the Londonderry High and the Ashmore Platform, respectively.
The Sahul and Flamingo synclines are northwest-trending depocentres that link and offset the northeast-trending Vulcan Sub-basin, Malita Graben and Calder Graben rift systems. These synclines are separated by the Laminaria and Flamingo highs.
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