MESOZOIC-KAROO AND POST-KAROO FORMATIONS IN THE KILWA AREA, SOUTHEASTERN TANZANIA - A STRATIGRAPHIC STUDY BASED ON PALYNOLOGY, MICROPALAEONTOLOGY AND WELL LOG DATA FROM THE KIZIMBANI WELL

The Kizimbani exploration well, drilled by Agip (Africa) Ltd. in the Kilwa area of southeastern Tanzania in 1979, has provided new information on the Karoo basin in the coastal region of Tanzania and its post-Karoo geohistory. The sediments can be divided into four major lithostratigraphic units which have been dated on palynological and micropalaeontological evidence: The Ngerengere(?) Beds, of Early Jurassic age, are resting on metamorphic basement (reached at 2612 m depth) and consist of approximately 700 m of continental conglomerates, sandstones and clays representing the youngest Karoo. Succeeding these beds are three post-Karoo units which are correlatable with lithostratigraphic units previously described from outcrops. These start with the Middle Jurassic Matumbi Series (600 m of clays and limestones) followed by the Middle(?) to Late Jurassic Pindiro Shales and Evaporites (1100 m) and terminate with the mid-Cretaceous Kingongo and Kihuluhulu marls (250 m).The evaporites are assigned a Late Jurassic age in contrast to earlier interpretation of another well (Mandawa No. 7) which had placed them in the upper part of the Karoo sequence (Triassic - ?Early Jurassic). A geohistory diagram has been constructed for the Kizimbani Well and a reinterpretation is offered for the Mandawa No. 7 Well.