Reconstruction of the evolution of the Niger River and implications for sediment supply to the Equatorial Atlantic margin of Africa during the Cretaceous and the Cenozoic

Abstract

AbstractThis paper presents a reconstruction of the palaeodrainage evolution of the Niger River in West Africa in order to contribute to the understanding of sediment supply to the Niger Delta. It has been covered extensively in literature that the Niger River has undergone changes along its course in the Holocene, as implied by the large bend it makes in Mali. However, other enigmatic bends further downstream are indicative of an older and more complicated history that has yet to be understood, and is the focus of this paper. Until now, sediment supply from the Niger River has been considered as being negligible compared to that of the Benue River. The results of this study imply that the contribution from the Niger River was more important than previously thought. The Niger River obtained its present-day geometry in three phases: a Bida Basin phase (Maastrichtian–Miocene); a Iullemmeden Basin phase (Miocene–Pleistocene); and a present-day Niger River phase (Holocene). In the Miocene, an important capture event occurred, increasing the incipient drainage basin by 106 km2, thereby changing the provenance of the sediment supplied to the Niger Delta from mainly crystalline basement to mixed lithologies including sandstone, shale, limestone and volcanic outcrops.