Coastal Tanzania

A combination of four major tectonic events has contributed to the evolution of Coastal Tanzania; a failed NNE rift, a successful NNW rift, an EW graben and the right-lateral drift of Madagascar. The petroleum province is delineated to the east by the Davie Fracture Zone (DFZ) which represents the right-lateral wrench fault along which Madagascar moved. West of this zone, synrift sediments of Triassic to Early Jurassic age overlain by post Middle Jurassic to Recent post rift sequences are preserved. The Selous Basin occupies the failed rift in the southern area of the Coastal Basin. To the north, the rift is occupied by the Ruvu Basin, to the north- west of the Dar es Salaam Platform. The successful rift margin is occupied by the present-day Ruvuma and Mandawa basins, which are situated east of Selous and separated by the Masasi Spur basement high. North of these basins the east-west trending Rufiji Trough cuts across both failed and successful rifts. Offshore Tertiary Basins parallel the coast and are associated with large, down-to-the-basin faults, which demarcate the present coastline. A series of broad troughs and anticlines parallel the coast offshore. The islands of Pemba, Zanzibar, Latham, and Mafia appear to be basement-cored uplifts.