Kenya5

Kenya Offshore

If the southern part of the Kenya offshore is dominated by the Pemba-Simba and Davie Ridges with the Maridadi Trough (depocenter) between them, the northern part is characterized by the reverse reactivation of the normal faults bounding the rift-type basins during the late Middle Cretaceous and by a gravitary folded-belt quite developed in the Somalia offshore (see Page 67 and Page 68). This tentative geological interpretation of a manual autotrace of a strike seismic line, roughly, parallel to the Kenya coastline, illustrated the major geological features of this offshore. The breakup unconformity is, easily, recognized, as well as, the rift-type basins which predating the breakdown of the Gondwana lithosphere, are, basically, Jurassic in age. The Atlantic-type divergent margin is well developed, particularly during the Early -Middle Cretaceous, with the formation of a major depocenter (Maridadi Trough) in the southern part of the offshore. However, by the end of these geological epochs, a compressional tectonic regime reactivated the normal faults bounding the rift-type basins with reverse faulting movement, creating an huge anticlinorium (inverted depocenter) and a local tectonic enhanced unconformity, i.e., a local relative sea level fall since the sediments were shortened and uplifted (generally, to have a significant erosion, a substantial relative sea level fall is necessary because the sediments must be to exhumed). The anticlines of the anticlinorium are elongated along the axial direction by compressional strike-slip, which, often, certain geoscientists, erroneously, interpreted them as normal (it is impossible to short and to length the sediments at same time in same place). This kind of faults, on the top of the anticline, was, perfectly described, in the 60's, on the Swiss Jura by my professor C.E. Wegman. A lateral ramp of the gravitary folded-belt is, barely, viable on the northern part of the autotrace. Such a folded-belt is obvious on dip seismic lines as illustrated on the manual autotrace of Page 41.