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Análise da evolução tectonossedimentar da Bacia dos Parecis através de métodos potenciais

2007; Sociedade Brasileira de Geologia; Volume: 37; Issue: 4 Linguagem: Inglês

10.25249/0375-7536.2007374639649

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, partially covering the Sunsás, Rondônia-Juruena and Tapajós-Parima provinces (Santos 2002). Based on Teixeira (1993) and Siqueira (1989), the Parecis basin was divided, from west to east, into three tectono-sedimentary domains: the Rondônia tectonic, the central compartment ( negative gravimetric anomaly) and a interior sag (Alto Xingu basin). During the Ordovician to Early Permian, the eastern Amazon region was affected by an extensional event and the Cacoal formation was deposited (rift stage of the Parecis basin). From Devonian to Early Permian, Furnas, Ponta Grossa, Pimenta Bueno and Fazenda da Casa Branca formations were deposited during the sag stage of the basin. Mesozoic (Late Triassic to Cretaceous) 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 Rio Ávila Formation and the basalts of the Anarí and Tapirapuã formations. The Cretaceous depositional stage is represented by the Parecis Group. Gravity and magnetic data of the Parecis basin have been acquired by IBGE, PETROBRAS and CPRM. Gravimetry and magnetometry maps obtained through the use of the Oasis/Geosoft software show an extensive negative anomaly in the interior of the Amazon Craton, with an average deviation from regional field of -40 mgal. The east-west regional structural trend with a deviation from regional field of -80 mgal evidences the eastward continuity of Pimenta Bueno and Colorado grabens underneath the Mesozoic succession (Rondônia tectonic low). The existence of this structure is supported by the Euler Deconvolution map, obtained through an inversion procedure that allowed an estimation of the anomaly (basement) depth.