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Geological development of the East African coastal
basin of Tanzania

The East African coastal basin of Tanzania, which is characterised by an extensional tectonic style, is located along the passive continental margin of the western Indian Ocean. The present study is concerned with the Mafia Island and the Mafia Channel which together form a subbasin within the north-south elongated coastal sedimentary basin of Tanzania. In the time interval from late Paleozoic to Recent, the passive margin of the region was subjected to a three-fold geological development, namely the Karoo rifting phase (1) which is characterised by extensional tectonics, the Gondwana break-up and opening o f the Somali basin (2) which was contemporaneous with the movement o f Madagascar o f f the east African coast in the Mesozoic, and the Cenozoic East African rift system (3). This structural framework made provision to the basin deposition history. The development started with the deposition of the continental, terrigenous, Karoo sequence in the Upper Permian to Lower Jurassic. The Karoo deposition was followed by a series of transgressions and regressions under full marine conditions which started in the Middle Jurassic and continued into the Tertiary.