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Delvaux, D., Kervyn, F., Vittori, E., Kajara, R.S. & Kilembe, E. 1998. ‘Late Quaternary tectonic activity and lake level fluctuation in the Rukwa rift basin, East Africa’. Delvaux, D. and Khan, A. (eds), Journal of African Earth Sciences 26(3), special issue : Tectonics, sedimentation and volcanism in the East African Rift System : 397-421. Elsevier. I.F. 1.219.
Article in a scientific Journal / Article in a Journal
Interpretation of remotely sensed images and air photographs, compilation of geological and topographic maps, morphostructural and fault kinematic observations, and 14C dating reveal that, beside obvious climatic influences, lake water extent and sedimentation in the close hydrologic system of Lake Rukwa is strongly influenced by tectonic processes. Series of sandy ridges, paleo-lacustrine terraces and paleo-underwater delta fans are related to an Early Holocene high lake level and subsequent progressive lowering. The maximum lake level was controlled by the altitude of the watershed between the Rukwa and Tanganyika hydrological systems. Taking as reference the present elevation of the paleo-lacustrine terraces around Lake Rukwa, two orders of vertical tectonic movements are evidenced: (1) a general uplift centred on the Rungwe Volcanic Province between the Rukwa and Malawi rift basins, and (2) a tectonic north-eastwards tilting of the entire Rukwa rift basin, including the depression and the rift shoulders. This is supported by the observed hydro-morphological evolution. Local uplift is also induced by the development of an active fault zone in the central part of the depression, in prolongation of the Mbeya Range-Galula fault system. The Ufipa and Lupa Border Faults, bounding the Rukwa depression on the south-western and north-eastern sides respectively, exert passive sedimentation control only. They appear inactive or at least less active in the Late Quaternary than during the previous rifting stage. The main Late Quaternary tectonic activity is represented by dextral strike slip movement along the Mbeya Range-Galula fault system, in the middle of the Rukwa Rift Basin, and by normal dip-slip movements along the Kanda fault, in the western rift shoulder.