The Barreiras Group is a Miocene to Lower Pleistocene continental terrigenous sedimentary deposit exhibiting a large occurrence along the Brazilian coast. In the Conde region, located in the northeastern part of the State of Bahia, the sedimentological characteristics of these sediments are indicative of a deposition as gravelly and sandy bed load in braided fluvial systems, related to alluvial fans, under an arid to semi-arid climate. The basal portion of the group is dominated by a gravelly-sandy lithofacies deposited by debris flows and pseudoplastic debris flows, with lesser occurrences of subaqueous deposits, characterizing a proximal fluvial system deposition. The upper portion is made up of gravelly-sandy sediments that include subaqueous, debris flows and pseudoplastic debris flows deposits. They suggest deposition in a more distal zone as indicated by the larger occurrence of subaqueous deposits and the presence, though rare, of downstream-accretion macroforms. Besides the climate control, deposition of the Barreiras Group was strongly influenced by the intraplate tectonism, which has been affecting the South America Platform since the Middle Miocene, when neotectonism began in Brazil.

· SEDIMENTARIES FACIES AND SEDIMENTATION MODEL FOR THE PARAGUA<;U GROUP IN RIO DE CONTAS REGION, WESTERN BORDER OF CHAPADA DIAMANTINA, BAHIA. The Middle Proterozoic metasediments of the Paraguacu Group, outcropping in the Rio de Contas region, on the western border of the Chapada Diamantina (Bahia), consist of three terrigenous sedimentary facies displaying characteristic features of eolian-, coastal-, and shelf-type depositional environments. The facies I, which occupies the basal portion of the sequence, is made up of quartzites and laminated metasandstones interpreted as transgressive in nature, and deposited over as extensive. shallow marine platform, showing storm effects. The intermediate facies 2 is composedof quartzites with large scale high-angle cross-bedding defined as eolian is origin, accumulated on vast coastal dune fields, Facies 3, which constitutes the top of the group, starts with transgressive, fine. and laminated metasandstones (sub-facies 3A) deposited in a shoreface environment, under moderate energy conditions. This is overlain by muddy deposits (sub-facies 3B), also transgressive in nature and accumulated in a shelf environment submitted to hydraulic regimes of alternating calm and stormy periods. The uppermost facies of the Paraguacu Group (sub-facies 3C) consists of metasiltstones and metasendstones deposited in a shoreface zone, prograding over a muddy shelf.