Dynamics of prolonged continental extension in magmatic rifts: the Turkana Rift case study (North Kenya)

Abstract

The Turkana magmatic rift (Northern Kenya) initiated at 45 Ma as one of the nucleation zones of rifting in the East African Rift. It forms an anomalously broad-rifted zone (c. 200 km) striking with a north-south trend and lying within a NW-SE topographic depression, floored on both sides of the Turkana area by Cretaceous rifts in the Sudan and Anza plains. From a compilation of available data, combined with newly acquired remote sensing and DEM dataset, we propose a five-stage tectono-magmatic model for the Turkana rift evolution (45–23 Ma; 23–15 Ma; 15–6 Ma; 6–2.6 Ma and 2.6 Ma-Present). The corresponding ‘restored’ maps clearly show the changing spatial distribution of magmatism and fault/basin network with time, hence supplying some clues about dynamics of continental extension. First-order basement-rooted transverse faults zones are identified and their influence on nucleation and propagation of strain is demonstrated, whereas the role of magmatic ‘soft-spots’ as concentrating strain is minimized. Blocking of deformation as well as rift jump and lateral transfer of strain are discussed in relation to various types of fault interaction (dip direction, strikes and acute/obtuse angle of the intersecting faults). The causal links between rift nucleation ‘cells’ and inherited transverse weakness zones in the Turkana rift might also exist elsewhere along the eastern branch of the East African Rift, hence suggesting a complex and discontinuous mode of rift propagation.

Timing of volcanism and evolution of the northern Kenya Rift

“…This sample comes from a structurally complex zone, called the Kataboi Fault Zone by Vetel & Le Gall (2006), which appears to separate older rocks to the north from younger rocks to the south (Fig. This sample comes from a structurally complex zone, called the Kataboi Fault Zone by Vetel & Le Gall (2006), which appears to separate older rocks to the north from younger rocks to the south (Fig.…”

Tectonic Inheritance in Continental Rifts and Passive Margins

“…The area between the two normal faults is called an 'accommodation zone' or a 'transfer zone' (Fig. In one way, the entire Wilson cycle is controlled by inheritance (Vetel and Le Gall 2006;Stuart et al 2006;Adet et al 2011). Review and comparison of passive rifts are available in Melankholina (2008), Melankholina and Suschevskaya (2008), Levell et al (2010) etc.…”

Analysis of gravity field to reconstruct the structure of Omo basin in SW Ethiopia and implications for hydrocarbon potential

“…1). The connection between the Mesozoic south Sudan basins and the Anza graben is debatable due to large data gap (Brown et al, 1985;Bosworth, 1992;Ebinger and Ibrahim, 1994;Hendrie et al, 1994;Vetel and Le Gall, 2006) and an understanding of the structural evolution of the Turkana e Omo rifts will definitely shade light on this possible link. At the southern end of the Omo basin lies the potentially promising north e south trending Kenyan rifts; at its northern end the Omo basin forks into the narrower Mago and Usno basins at its northern end (Ebinger and Ibrahim, 1994).…”