Upper Aptian–lower Albian of the southern-central Araripe Basin, Brazil: Microbiostratigraphic and paleoecological inferences

Abstract

The aim of this study was to produce an integrative analysis of macroinvertebrates (decapods, gastropods, and bivalves) and microfossils collected in the Romualdo Formation, south-central Araripe Basin. Additionally, we provide the first report of calcareous nannofossils, a diverse and unique association of the marine ostracods Dicrorygma cf. minuta, Perissocytheridea spp., Dicrorygma (Orthorygma?) dimorpha, and Paracypris sp. and benthic and planktonic foraminifera. The Santo Antonio section contains assemblages of Tethyan origin that indicate an unstable paleoenvironment formed by hypersaline lagoons with two marine ingressions. Planktonic foraminifera assemblages comprised of Hedbergella aptiana and Pseudoguembelitria sp., suggest that the first marine ingression occurred in the Aptian (possibly late Aptian – planktonic foraminifera biozone Paraticinella rohri), while the second occurred during the early Albian (biozone CC8), as indicated by calcareous nannofossils (Hayesites albiensis). The fossil assemblages that characterize the Romualdo Formation, provide new biostratigraphic information and point towards the probable Aptian–Albian boundary in the Santo Antônio section.