Non-marine ostracod biostratigraphy of Cretaceous rift lake deposits (Sousa Basin, Brazil): Paleogeographical implications and correlation with Gondwanic basins

Abstract

The Cretaceous section of the Sousa Basin represents alluvio-fluvio-lacustrine deposits from rift lakes generated in NE Brazil as a consequence of the West Gondwana break-up process, marked by progressive separation of the African and South American plates. The chronostratigraphic age of the sedimentary succession is controversial due to the few biostratigraphic data available, based on palynomorphs, ostracods and ‘conchostracans’ (Spinicaudata), and taxonomic problems of some of the fossils. Non-marine ostracods (microcrustaceans) are useful index fossils and have been used for a regional biozonation of the lacustrine deposits. Due to this factor non-marine ostracods from the core 2-FC-01-PB, which comprises rocks of the Sousa Formation (Rio do Peixe Group), were analysed. The core 2-FC-01-PB assemblage includes index taxa for biozones RT-002 to RT-005 (Alicenula leguminella, Brasacypris ovum, Cypridea ambigua and Reconcavona swaini), indicating a Berriasian to Hauterivian age (Rio da Serra/Aratu local stages). The previous assignment of a Jurassic age to the early stage of deposition of the Rio do Peixe Group is refuted here. We discuss and revise the stratigraphic range and paleogeographical distribution of relevant index ostracods. Our revised non-marine ostracod biostratigraphy facilitates correlations of non-marine strata of the Sousa Basin with those of Brazilian (Recôncavo, Tucano and Sergipe) and African (Gabon and Congo) sedimentary basins of West Gondwana.