South Atlantic, Benue Trough, and Gulf of Guinea Cretaceous Triple Junction

Abstract

During the early separation of Africa from South America, the South Atlantic and the transform faults of the Gulf of Guinea were joined by a short-lived line of lithosphere spreading running northeast from the Niger delta, under the Benue trough. The separation of the continents was established by Aptian times, and the spreading under the Benue trough lasted from the Albian to the Santonian. The early separation of West Africa from northern Brazil was characterized by lateral movements of the two continents against each other along the St. Paul9s and the Romanche oceanic transform faults. Some 20 m.y. of transform fault motion may have elapsed before West Africa was completely separated by oceanic crust from northern Brazil. The South Atlantic, Benue trough, and the Gulf of Guinea formed an unstable RRF triple junction, which may have caused internal strain in the African plate. It may also have resulted in possible dilation of the Gulf of Guinea transform faults which, together with the short intervening ridge segments, served to localize the Cretaceous volcanicity thought to be responsible for the recently discovered North Brazilian Ridge.