Calcareous nannofossils, biostratigraphy, and paleobiogeography of the Aptian/Albian Romualdo Formation in the Araripe Basin, North-Eastern Brazil

Calcareous nannofossils, biostratigraphy, and paleobiogeography of the Aptian/Albian Romualdo Formation in the Araripe Basin, North-Eastern Brazil

Blog Article

Abstract The objectives of this study were the biostratigraphic and paleobiogeographic interpretations of the calcareous nannofossil records of the Romualdo Formation (Aptian-Albian) in the south-central portion of the Araripe Basin.The methods used to process the samples were decanting, smear slide, centrifugation, and ultra-thin section confection.The taxonomic and biostratigraphic interpretations were carried out through qualitative and quantitative investigations.A total of 11 genera and 17 species of calcareous nannofossils, namely, Biscutum constans, Biscutum sp.

, Braarudosphaera africana, Braarudosphaera sp., Calculites Gym Mat sp., Discorhabdus ignotus, Hayesites albiensis, Hayesites sp., Nannoconus bucheri, Nannoconus sp.

, Retecapsa surirella, Rhagodiscus sp., Thoracosphaera sp., Watznaueria barnesiae, Watznaueria sp., Zeughrabdotus erectus, and Zeughrabdotus noeliae were identified.

The integrated analysis of three outcrops suggests two distinct marine phases: the first in the Aptian, recognized ORG PROTEIN in two outcrops, and during the Albian age.The genera Hayesites and Nannoconus suggest a strong Tethyan affinity.Differently, other calcareous nannofossils such as Watznaueria, Thoracosphaera, and Braarudosphaera recorded here are considered more resistant, cosmopolitan, and/or opportunistic species.Biscutum and Zeughrabdotus are sensitive calcareous nannofossils because they are more susceptible to dissolution and cannot be surely used to define this paleobiogeography and biostratigraphic range.