ANÁLISE ESTRATIGRÁFICA DA SEQÜÊNCIA DEPOSICIONAL DEVONIANA DA BACIA DO PARANÁ (BRASIL)

Abstract

The Devonian System in the Paraná Basin is one of the major transgressive sequence over the Brazilían Craton, cal1ed the Gàmma Sequence. The marine shale and siltstones of the Ponta Grossa Formation overlap and grade updip toward north and east thé fluvial and litoral sandstones of the Furnas Formatíon. At north the Ponta Grossa Formation embodies a c1astic wedge that is correlatable to a wide sheet of litoral and shallow platform fine sandstones, known in "eastern part of the basin as Tibaji Member. The Iower and upper parts are the Jaguariaíva and São Domingos members. The Furnas Formatíon consísts of coarse to fine and conglomeratic sandstones with prominent planar cross stratifícation. No fossils remains are known in this unit except various ichnofossils inclusively Rouaultia fumai. Field observation and log signatures indicate environment of anastomosed fluvial plain ar alluvial fan, for the main part of the formation, and beaches in the upper transitional part. The Jaguaruaíva Member of the Ponta Grossa Formation ís made up of fine sandstones grading to siltstones with the marine fossils Língula and Orbiculoidea and gray to black shales and siltstones with the fóssil community of Australocoelia of deeper platform of Emsian age. The sandstones of the Tibaji Member contaíns the Australospirífer community, representing a regressive part of the cycles as results of a prograding clastic wedge event. The shales of the São Domingos Member contain the fossíls of the Notiochonetes community of Eífelian-Givetian age preserved in very low energy environment of platform, recording the new transgressive cycle. The Devonian System ends up in the Paraná Basin with siltstones and fine sandstones deposited in maríne bars and barríers with the Lingula community, at the end of the Gívetían, truncated by the Early to Late Carboniferous unconformity.