Age of the Separation of South America and Africa

Abstract

ON the basis of the positions of the magnetic south pole in the Triassic determined by palaeomagnetic studies of African and South American rocks, Creer¹ has argued that the drifting apart of Africa and South America began in the Permian. Briefly, if South America and Africa are placed in such a position that their Palaeozoic polar wandering curves coincide, there is obtained a reconstruction very similar to that suggested by the shapes of the coastlines, and the earliest palaeopoles which do not coincide are those of the Triassic. In this argument, the Triassic palaeopole for South America was computed from a study of the lavas of the Serra Geral formation, in the southern part of Brazil. Unfortunately, a radiometric study² of forty-one samples of basalt and dacite has shown that the principal phase of this igneous cycle is of Middle Cretaceous age, about 115–125 m.y.