Early Cretaceous basalt volcanism and initial continental rifting in Benue Trough, Nigeria

Abstract

THE Benue Trough, located at the Gulf of Guinea re-entrant on the west coast of Africa (Fig. 1) is a sediment-filled ‘failed rift’, forming the third arm of a Cretaceous triple-rift (rrr) system that involved the South Atlantic and the Gulf of Guinea^1–3. The rift nature of the Benue Trough was first documented by King⁴ on geomorphological grounds, and this supposition has since been confirmed by geophysical⁵, stratigraphic⁶ and faunal evidence^7,8. The considerable interest shown in the stratigraphic and tectonic evolution of the Benue graben is due to its relationship to the opening of the South Atlantic and the initiation of continental drift^9–11. The age of the oldest Albian sediments within the trough, and their faunal biostratigraphy have been used to date the continental separation of Africa from South America⁷, and infer the history of seafloor spreading in the equatorial Atlantic region¹². New evidence is presented here on the nature of the early Cretaceous volcanism in the Benue Trough, and its petrogenesis is shown not to be due to a shortlived subduction or continental collision.