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Neogene-Holocene rift propagation in central Tanzania: Morphostructural and aeromagnetic evidence from the Kilombero area

Bernard Le Gall^,1, Laurent Gernigon^,1, Joel Rolet^,1, Cinthya Ebinger^,2, Richard Gloaguen^,3, Odd Nilsen^,4, Henning Dypvik^,4, Benoit Deffontaines^,5 and Abdul Mruma^,6

¹ UMR-CNRS 6538 ‘Domaines Océaniques,’ Institut Universitaire Européen de la Mer, Place Nicolas Copernic, 29280 Plouzané, France
² Department of Geology, Royal Holloway, University of London, Egham Hill, Egham, Surrey TW 20 0EX, UK
³ TU Bergakademie Freiberg, Institut fur Geologie, B. von Cotta 2, D-09599 Freiberg, Germany
⁴ Department of Geology, University of Oslo, Post Office Box 1047, Blindern N 0316 Oslo, Norway
⁵ Institut Morphologie et Environnement Littoral, 35320 Dinard, France
⁶ Department of Geology, University of Dar es Salaam, Post Office Box 35052, Tanzania

Based on field studies supplemented by remote sensing and aeromagnetic data from central Tanzania, a Phanerozoic structural history for the region can be developed and placed in a broader rift context. The major contribution of this work is the recognition of rift morphology over an area lying 400 km beyond the southern termination of the Eastern, or Kenya, Rift. The most prominent rift structures occur in the Kilombero region and consist of a wide range of uplifted basement blocks fringed to the west by an east-facing half-graben that may contain 6–8 km of sedimentary strata. Physiographic features and river drainage anomalies suggest that Holocene/Neogene deformation occurs along both rift-parallel and transverse faults, in agreement with the seismogenic character of a number of oblique faults. The present-day rift pattern of the Kilombero extensional province results from the complete overprinting of an earlier (Karoo) rift basin by Neogene- Holocene faults. The Kilombero rift zone is assumed to connect northward into the central rift arm (Manyara) of the Eastern Rift via an active transverse fault zone. The proposed rift model implies that incipient rifting propagates throughout the cold and strong lithosphere of central Tanzania following Proterozoic basement weakness zones (N140°E) and earlier Karoo rift structures (north-south). An eventual structural connection of the Kilombero rift zone with the Lake Malawi rift further south is also envisaged and should imply the spatial link of the eastern and western branches of the East African Rift System south of the Tanzanian craton.

Key Words: East African Rift • central Tanzania • Karoo/Cenozoic extensional faulting • satellite imagery • drainage pattern analysis • aeromagnetic data

This article has been cited by other articles:

				E. Calais, C. Ebinger, C. Hartnady, and J.M. Nocquet Kinematics of the East African Rift from GPS and earthquake slip vector data Geological Society, London, Special Publications, January 1, 2006; 259(1): 9 - 22. [Abstract] [PDF]

				U. RING, H. L. SCHWARTZ, T. G. BROMAGE, and C. SANAANE Kinematic and sedimentological evolution of the Manyara Rift in northern Tanzania, East Africa Geological Magazine, July 1, 2005; 142(4): 355 - 368. [Abstract] [Full Text] [PDF]