STRUCTURAL LINK BETWEEN TANGANYIKA- AND RUKWA-RIFT BASINS AT KAREMA-NKAMBA (TANZANIA): BASEMENT STRUCTURAL CONTROL AND RECENT EVOLUTION

Abstract-In a WNW-ESE striking depression on the basement-high between the Rukwa and Central Tanganyikarift basins of West Tanzania, the drainage pattern of the Nkamba river testifies that during the Last Early Holocene, water drained from Lake Rukwa towards Lake Tanganyika. This connection was only interrupted in recent times. From geological maps, and supported by basement structural studies, interpretation of satellite images and a digital elevation model of the region, the close structural relationshipbetween the rift and the Palaeoproterozoic Ubende belt is highlighted. TIle NW striking rift roughly follows the regional buildup of the Palaeoproterozoic Ubende belt, particular structures of which were repeatedly reactivated and became inherited in todays rift morphology. This also applies for the basement structuresunder the WNW-ESE trending Nkamba-Karema depression, where eclogite remnants show that the Palaeoproterozic Ubende belt is involved as a suture. The WNW trending flexure and its reactivation features confirm the close control of the Ubende belt's structural characteristics on the Phanerozoic rift evolution: the Rukwa rift developed upon the regional NW Ubende suture, and is linked to the Central Tanganyika (-Kalemie) rift through the WNW flexure in the suture, controlling the Karema-Nkambarift depression. Recent tectonic activity along the NW Rukwa trend may have triggered the closing of the WNW-ESE Nkamba-Karema flexure