Published:January 01, 1995
1995. "Orange Basin", Sequence Stratigraphy in Offshore South African Divergent Basins: An Atlas on Exploration for Cretaceous Lowstand Traps by Soekor (Pty) Ltd., L. F. Brown, Jr., J. M. Benson, G. J. Brink, S. Doherty, A. Jollands, E. H. A. Jungslager, J. H. G. Keenan, A. Muntingh, N. J. S. van Wyk, G. J. Brink, N. J. S. van Wyk, L. F. Brown, Jr., K. R Barton, K. J Bate, S. R Carney, A. A. Fraser, N. Fraser, H. J. Gouws, M. G. Guest, K. A. Kitchin, H. W. Pferdekämper, J. Turner, V. H. Valicenti, G. W. J. Beamish, D. S. Broad, P. J. Buck, P. L. A. Burden, C. P. N. Davies, J. Fouché, C. E. Gilbert, K. Hodges, J. J. Maier, S. P. Petrie, S. H. Robson, J. Roux, G. J. Smit, J. Turner, V. H. Valicenti, D. Van Der Spuy, T. Webb, S. J. Winters, H. T. Buhrmann, R. D. P. Noble, P. J. Strauss
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The South African part of the Orange Basin covered by this Atlas underlies the Atlantic Ocean offshore from southwestern South Africa and extends almost 500 km between Cape Town and the South African-Namibian border near Alexander Bay (Figures 1, 127). The postrift basin overlies several rift basins of Early Cretaceous age and is bounded on the northwest by the Kudu Arch of southern Namibia and on the southeast by the Agulhas-Columbine Arch. The basin is filled with postrift Cretaceous siliciclastic rocks ranging in age from late Hauterivian drift onset (~117.5 Ma) to Tertiary (Figure 128). Drift onset in the basin was ~9 m.y. later than that in the Pletmos and Bredasdorp basins, as noted in Figures 9, 10, and 128. A major focus of this Orange Basin study was an analysis of Cretaceous rocks ranging in age from 112 to 67 Ma. Analysis of the older postrift strata (117.5–112 Ma) was generally constrained in this investigation because of perceived source rock and diagenetic limitations on reservoir quality.
Exploration of the Orange Basin began during 1974 with discovery of the Kudu gas field in southern offshore Namibia (Figure 127). Regional interpretations of the then-available geologic and seismic data from the southwestern African continental margin south of Namibia were published during the 1980s (e.g., Austin and Uchupi, 1982; Gerrard and Smith, 1982). Soekor (Pty) Ltd. has drilled 30 boreholes in South African Atlantic waters within the 145,000 km2 area (Figure 1) from the shoreline seaward to the 2000-m isobath (not shown). Before
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Sequence Stratigraphy in Offshore South African Divergent Basins: An Atlas on Exploration for Cretaceous Lowstand Traps by Soekor (Pty) Ltd.
“Sequence Stratigraphy in Offshore South African Divergent Basins” is the result of an offshore exploration and drilling program by Soekor (Pty) Ltd in the Republic of South Africa beginning in 1987. Seismic stratigraphic data and borehole information were incorporated and released in what was one of the first detailed and comprehensive published examples of the new field of sequence stratigraphy. The project was conducted over a South African offshore area of 175,000 km2, in the Pletmos, Bredasdorp, and Orange basins, which are examples of divergent basins associated with the breakup of Gondwana. Thirty-four third-order Cretaceous sequences between 126 and 67 Ma were recognized and correlated. The book is published in an oversized 11” × 24” landscape format, which works well for the numerous seismic lines and cross sections in this heavily illustrated volume. Each basin is examined in detail, including discussion of the tectonic, paleogeographic, and depositional settings, and the sequence stratigraphy based in large part on regional seismic interpretation. The application of the sequence stratigraphic interpretations to generation of petroleum prospects and evaluation of drilling results is the end result, provided in a manner that is far more open and enlightening than is the case for typical petroleum industry publications.