DISCUSSIONS on the opening of the South Atlantic in terms of major plate tectonic structures such as spreading ridges, transform faults, and so on, have tended to concentrate on the West African segments1–3. Evidence has been presented for regarding the original break in the Gulf of Guinea as an RRR junction, the southward-trending arm becoming the Mid-Atlantic Ridge, the north-east-trending arm (Benue Trough) undergoing a relatively minor phase of opening followed by closing, and the westward arm becoming modified by a series of oblique shears so that movement there became a combination of spreading and transform motion (ref. 1, Fig. 1). An analogous set of movements was proposed for the Red Sea, Dead Sea, Gulf of Suez junction. Later, a large number of other triple junctions was recognised4, including a Georgetown RRR junction to the west which helped to define the course of the Africa/South America split and left the Takutu rift in Guyana as a failed arm filled with Cretaceous deposits.