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Abstract

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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