RIFTING AND MAGMATISM ASSOCIATED WITH THE SOUTH AMERICA AND AFRICA BREAK UP

Abstract

Based on about 380 K/Ar dating of basic and alkaline magmatic rocks from Brazilian sedimentary basins and the Argentinean Atlantic margin it is possible to interpret the evolution of the rifting that caused the South America and Africa break-up. This process started in the Triassic and took place northwestward of the Foz do Amazonas Basin, on the equatorial Brazilian continental margin, and reached the San Julian and North Malvinas basins, in the southern portion of South America. From this latter region up to the Espírito Santo Basin, rifting took place between the Jurassic and Neocomian whereas transcurrence caused by clockwise rotation of South America on the equatorial margin generated the Potiguar Basin. The available information suggests that the final break-up of Africa and South America occurred along the eastern Brazilian margin, between the Cumuruxatiba/Mucuri and Pernambuco basins, during the Cenomanian/Turonian. The resistance offered by the São Luis/West African and São Francisco/Congo cratons promoted the huge magmatic manifestations which occur in the Brazilian Paleozoic intracratonic basins (Acre, Solimões, Amazonas, Parnaíba and Paraná basins) as well as in the interior Tacutu Rift. Hot spots turned out during the drift phase, as registered by the Mecejana (CE)/Rocas Atoll/Fernando de Noronha Archipelago Alignment and Poços de Caldas/Cabo Frio Alkaline Rocks Alignment that persists up to the Vitória/Trindade Chain.