A fragmentação do Gondwana na região meio-norte do Brasil durante o mesozóico

Abstract

South America, Africa, India, Antarctic and Australia continents formed a great and complex supercontinent called Gondwana at the end of the Precambrian. From the Mesozoic this mega-continent underwent extension and regional uplift with volcanism associated, resulting in triple junctions which evolved to rift systems. These events are related to the Wealdenian Reactivation or South-Atlantic event witch took place in the interior and the boundary of the South America plate, been followed by intense basic magmatism and extensional systems formation, with listric and planar faults. Some basin architecture are controlled by ancient shear zones reactivations. From Triassic the extension gave rise to uplifts associates to the magmatism in the weakness areas of the basement, including the Paleozoic basins in the northern Brazil. This event responds to the Pangaea break-up, the formation of the Central Atlantic Ocean and the individualization of the Laurasia and Gondwana supercontinents. The arm of the Central Atlantic in the South America evolved to rift system in the Foz do Amazonas basin and volcanism in the Parnaíba Basin during the Triassic and Jurassic. This rifting event died out towards the south and propagated to the Caribbean region, resulting in North America plate formation. From the early Cretaceous (end of Barremian and beginning of the Aptian), new phase of rifting is registred in the region, without linkage to the Central Atlantic. This had been increased the Foz do Amazonas basin and Marajó basin formation and a new phase of uplifting followed by volcanism and rifting concentrated at the Ferrer-Urbano Santos Arc, Parnaíba Basin, and the formation of the Gurupi Graben System (Bragança-Viseu, São Luís and Ilha Nova basins) and Grajaú Basin. This event includes two distinct phases: early rifting resulting in the formation of the Bragança-Viseu and Ilha Nova basins; and thermal subsidence with the formation of the São Luís and Grajaú basins, separate by short time span. These basins underwent rapid evolution, with sedimentary environment records since fluvial and lacustrine until transgressions. In the Lower Cretaceous continued the evolution of the Foz do Amazonas Basin witch the fragmentation propagating towards the SE, resulting in the formation of the Pará-Maranhão Basin and Barreirinhas Basin at the beginning of the Albian. This event is resposible for the Equatorial Atlantic Ocean individualization, with associated transgression in the Pará-Maranhão and Barreirinhas basins, as well in the São Luís, Ilha Nova and Grajaú Basins, controled by NE-SW fractures and faults in the São Marcos Bay and by partial collapse of the Ferrer-Urbano Santos Arc. During the Late Cretaceous it had reducted the extension at the Marajó Basin, stopped the fragmentation in the Gurupi Graben System and the South America and African continents were completely pulled apart, with formation of oceanic crust and passive margins in the Foz do Amazonas, Pará-Maranhão and Barreirinhas Basins. From the Upper Cretaceous, the east margin of the South America and the west margin of Africa had assumed its current configuration, withchanges related to drifting and to the Neotectonic.