Atlantica revisited: new data and thoughts on the formation and evolution of a long-lived continent

Abstract

The existence of the continent Atlantica, postulated to encompass the Amazonian, São Luís, West African, São Francisco–Congo, and possibly, Rio de la Plata cratons, as well as the basement of the Neoproterozoic Gurupi, Araguaia, Borborema, Nigeria, and Cameroon belts, is evaluated based on an assessment of a large volume of recently published data. Striking similarities are found in the pre-Brasiliano–Pan-African geological events in these regions, supporting the Palaeoproterozoic formation of Atlantica and its persistence through the end of the Precambrian, when it was incorporated in western Gondwana. Formation of Atlantica involved the amalgamation of Archaean microcontinents, 2.4–2.3 thousand million year-old juvenile crust (extremely rare elsewhere), and 2.25–2.10 thousand million year-old crust, culminating with a great collisional event at 2.10–2.05 Ga. Afterwards, Atlantica continued to grow southwestward by accretion of successive magmatic arcs to the Amazonian craton, and eastward by incorporation of the Tanzania craton and the Bangweulu Block to the Congo craton, whereas its core was subjected to several events involving intraplate continental extension. Major rifting in the early Neoproterozoic led to the formation of a passive margin south of the São Francisco craton, which may be related to separation of the Rio de la Plata craton. This event and successive ones did not produce large ocean basins separating the other components of Atlantica. Rifting and limited drifting followed by convergence in the late Neoproterozoic produced the Brasiliano–Pan-African Gurupi, Araguaia, Borborema, Nigeria, and Cameroon belts. Complete splitting of Atlantica only occurred during the Mesozoic with opening of the Atlantic Ocean.