Did South America and West Africa Marry and Divorce or Was it a Long-lasting Relationship?

Abstract

The 2.1-2.0 Ga Transamazonian orogen in South America can be well correlated with the 2.1-2.0 Ga Eburnean orogen along the western margin of West Africa. Both the orogens are characterized by early tangential tectonics, marked by large-scale thrusts and sinistral strike-slip faults, followed by later transcurrent tectonics, marked by dextral shear zones. Metamorphic evolution of the two orogens involved an initial phase of crustal thrusting and thickening, followed by exhumation and final cooling. These suggest that South America and West Africa may have been jointed along the Transamazonian-Eburnean orogen at 2.1-2.0 Ga. This is supported by the presence of ∼2.0 Ga fluvio-deltaic formations in nearly every craton in South America and West Africa. The available Paleomagnetic data also indicate that between 2.1-1.5 Ga, coeval rocks in West Africa and South America recorded similar polar wander paths. If South America and West Africa remained coherent from their amalgamation at 2.1-2.0 Ga until their incorporation into Gondwana at 0.6-0.5 Ga, the positions of South America and West Africa in the present configurations models of Rodinia need to be re-evaluated, since these configurations did not bring the two blocks into close proximity.