Nigeria

Potential Source-Rocks

Regressive Phase of the Continental Encroachment Cycle

In the very deep part of Nigeria offshore (3-4 seconds t.w.t. of water depth), it is, unlikely, that there is a generating petroleum sub-system. All organic matter preserved in the sediments is immature, since the water depth has any role in the maturation of organic matter. However, upstream (left part of the autotrace), a deep water Neogene generating petroleum sub-system may exist. In fact, on this autotrace above the oceanic crust there is a thick sedimentary column of about 6 seconds (double time), in which it is difficult to highlight transgressive sediments, in which an alternative generating petroleum sub-system seems to exist up-dip. Two compressional tectonic regime are recognized on this tentative geological interpretation. The first one, which seems to see a counterpart of the extensional tectonic regime present up-dip in the continental slope and conventional offshore, is characterized by reverse faults with a seaward vergence. The second one, represented, here, by faulted anticline structures with a landward vergence (reverse faults looking continentward) is induced by the decreasing morphology of the oceanic mountains away of the mid-oceanic ridge (rift-valley).