Revisão estratigráfica da Seção Silurodevoniana na Sub-bacia de Tucano Norte, região do Gráben de Santa Brígida, nordeste da Bahia

Abstract

The Santa Brígida Graben contains an important record of Tucano Norte Sub-basin with Silurodevonian Section outcrops. This record is represented by the Tacaratu Formation which is attributed to Silurian, and Inajá Formation that is assigned a Devonian age by its fossiliferous contents. However, there is a lack of more detailed characterization for these deposits in this region. In this context, it was sought, in two field mapping expeditions, to define thoroughly the deposicional system which encompasses these geologic units, through detailing the present sedimentary fácies, as well as accessing remote areas like ridges and hills tops. Regarding Tacaratu Formation, the paleocurrents analysis was important to interpret the presence of structural highs between what appears to have been a big braided tide-influenced delta plain. Detail sections of cliffs localized in the region provided a possible redefinition of the lithoestratigraphic arrangement previously proposed in the literature. In the Umbuzeiro Hill, rocks with strong evidences of a desertic system were observed, which were attributed to Sergi Formation that was in fault contact with Tacaratu Formation. Finally, in the Encantado Hill, it was characterized the most complete section of this work, as it has been indentified the Tacaratu Formation as the more basal Unit, superimposed by Inajá Formation delta front deposits, which, in turn, are underling the Sergi Formation aeolian sediments. Furthermore, petrographic analysis was made, which showed distinct textural characters between the discriminated units