Marco Antônio Fonseca

Assembling West Gondwana in the Neoproterozoic: Clues from the São Francisco craton region, Brazil

The Sao Francisco craton, which consists of Archean and Paleoproterozoic basement, now forms eastern Brazil; it once was at the center of West Gondwana. Distinct Neoproterozoic Brasiliano (Pan-African) orogenic belts border the cratons margins. Crosscutting relationships among these belts, along with stratigraphic features of the cover in the cratons interior, provide constraints on the sequence of collisions leading to the assembly of West Gondwana. The earliest collision involved the Sao Francisco–Congo and Rio de la Plata cratons and resulted in the formation of the Southern Brasilia belt. Next came the closure of the Brazilide ocean by collision between the Sao Francisco–Congo and Amazonia cratons. This event produced the Northern Brasilia belt, which now defines the northwest side of the Sao Francisco craton. An intracontinental rift, which merged southward with a narrow sea, once was between the Sao Francisco and Congo cratons; closure of this rift and sea led to the formation of the Aracuai and West Congo orogen, and to the southwestward extrusion of the Ribeira belt. Continued convergence of Amazonia against the Sao Francisco–Congo craton caused the eastward extrusion of the Borborema province. The final stage of West Gondwana assembly closed a basin between the Rio de la Plata and Amazonia cratons and created the Paraguai belt.