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AS TAFROGÊNESES SUPERPOSTAS ESPINHAÇO E SANTO ONOFRE, ESTADO DA BAHIA: REVISÃO E NOVAS PROPOSTAS

1996; Sociedade Brasileira de Geologia; Volume: 26; Issue: 4 Linguagem: Inglês

10.25249/0375-7536.19964265276

2177-4382

CARLOS SCHOBBENHAUS,

Indigenous Health and Education

The built up of the Espinhaço rift in the states of Bahia and Minas Gerais, took place along NS and NW-SE faults.In the State of Bahia the initial phase of the taphrogeny was marked by the Rio dos Remédios volcanism, dated at about 1750 Ma (U-Pb), and followed by the deposition of more than 5,000 meters of continental and shallow marine sediments.These units represent the Espinhaço supergroup in the northern part of the Espinhaço range and in the Chapada Diamantina plateau.A second extensional phase at the beginning of the Neoproterozoic, between 1000 and 900 Ma, lead to a new rifting episode in the area of the Espinhaço supergroup and its basement.Old faults of the former aborted Espinhaço rift were reactivated.A triple junction was developed in the southeastern margin of the São Francisco craton.In the lesser active arm of this junction the Santo Onofre rift was formed, penetrating the site of the Espinhaço supergroup in the State of Bahia.Along this neoproterozoic rift continental and marine sediments including turbiditic lobes were deposited.These units are represented by the redefined Santo Onofre group, which outcrops along the strike of the Espinhaço supergroup.The southern extension of the redefined Santo Onofre group is represented by the Macaubas group, in the upper Pardo river, northern Minas Gerais.Both southernly located limbs of the triple junction are represented by the assimetric Macaubas rift, which opens to the east to form a passive continental margin -the Araçuaf basin.In the Chapada Diamantina plateau, a discordance at the basis of the Morro do Chapéu formation, is interpreted to be genetically related to the deposition of the redefined Santo Onofre group.The Morro do Chapéu formation represents therefore also a neoproterozoic unit.On the other hand, the Tombador and Caboclo formations are mesoproterozoic platform sediments (∼1200-1000 Ma), probably related to a geodynamic event of grenvillian age.The closing of the Macaubas basin during the Brasiliano orogenesis, lead to the formation of the Araçuaí belt and to the deformation of the Santo Onofre group along the so called Paramirim deformation corridor in the interior of the São Francisco craton.This deformation involved also the Espinhaço system and its basement.