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REVISÃO ESTRATIGRÁFICA DA BACIA DOS PARECIS – AMAZÔNIA

2006; Sociedade Brasileira de Geologia; Volume: 36; Issue: 4 Linguagem: Inglês

10.25249/0375-7536.2006364692703

2177-4382

Ruy Benedito Calliari Bahia, Marcelo A. Martins-Neto, Maria Sílvia Carvalho Barbosa, Augusto José Pedreira,

Geological formations and processes

The Parecis basin is located in central-western Brazil, on the southwestern part of the Amazon Craton, between the Rondônia and Guaporé fold belts. From west to east, the Parecis basin can be divided into three tectono-sedimentary domains: a tectonic low to the west, a central compartment characterized by a negative gravimetric anomaly, and a interior sag to the east. During the Paleozoic (Ordovician to Early Permian), the Amazon region was affected by an extensional event, when the Cacoal, Furnas, Ponta Grossa, Pimenta Bueno e Fazenda da Casa Branca formations were deposited in the Parecis basin. The Coacal Formation is composed of conglomerates, wackes, shales and dolomites, interpreted as deposited in alluvial fans, deltas and lakes. The pebbly sandstones and shales of the Furnas and Ponta Grossa formations are interpreted as deposited, respectively, in tidal flats and marine environments. Glacial or glacial-influenced environments are suggested for the conglomerates, sandstones and shales of the Pimenta Bueno and Fazenda da Casa Branca formations. The sedimentary record of Parecis basin shows a stratigraphic gap from Permian to Triassic. Mesozoic volcanic and sedimentary successions record another extensional event in the Amazon region. This event is represented in the Parecis basin by the eolian sandstones of the Jurassic Rio Ávila Formation and the basalts of the Anarí and Tapirapuã formations. The sandstones of the Parecis Group have been deposited during the Cretaceous in fluvial and eolian environments. Cretaceous kimberlite bodies cut the sediments in the northeastern and southeastern parts of the Parecis basin. Cenozoic sandstones and mudstones cover unconformably the deposits of the Parecis basin.