EVOLUÇÃO TECTÔNICA DA MARGEM EQUATORIAL BRASILEIRA

Rifting and tectonic evolution along the Equatorial margin of Brazil were highly complex. ln offshore Amapá, an early stage of rifting started ln Permo-Trlaseic time, accompanied by diabase intrusions. Volcanic activity extended eastward to the Maranhão Basin, without leading to continental breakup. ln early Cretaceous time (144-119 Ma) the clockwise rotation of South America relative to Africa, about a pole situated near 39°W and 7°S, caused compression west of Fortaleza, forming the Ferrer-Urbano Santos Arch, and eastward increasing extension east of Fortaleza, leading to the formation of the Potiguar Basin. ln this eastern portion, N-S extension was accompanied by E-W compression as the eastern tip of Brazil was pressed against Africa. The resulting stresses reactivated Precambrian ductile shear zones by transtensional movement, creating several inland half grabens including the Pendência, Orós, and Rio do Peixe grabens. During Alagoas (Aptian) time, rifting propagated westward along the Equatorial margin and eastward along the Benué trough, both of which became marine seaways. From Albian time on, right lateral transtensional movement created NW trending rhomb grabens along the Equatorial margin. From Campanian through Eocene time, this right lateral movement was repeatedly interrupted by N-S compressional pulses which formed E-W trending folds and thrusts along the Equatorial margin and closed the seaway of the Benué trough. This compression may have been a distant reflex of the continental collision between Africa and Europe.