Ypresian Alveolina and calcareous nannofossils from the south Sabzevar area (Central Iran): biostratigraphic, taxonomic and paleobiogeographic implications

The Eocene carbonates of the south Sabzevar region in central Iran hold a rich Alveolina assemblage.Nine species including A. globula, Alveolina sp. 1, Alveolina aff. globula, A. regularis, A. globosa, A. pasticillata, A. laxa, A. pisiformis and A. cf. decipiens are identified through detailed analysis in thin section. The biostratigraphy obtained points to the early Ypresian Shallow Benthic Zones SBZ6 and partly SBZ7, indicating the occurrence of a lower Eocene carbonate system. The Alveolina biostratigraphy is correlated to the calcareous nannofossil biostratigraphy, and is assignable to the middle part of the NP10 Zone and especially with the CNE2 biozones. The evolutionary trends of A. globula and its dispersal through thewestern and central Neo-Tethys Ocean during theYpresian is here considered in relation with the occurrence of Alveolina sp. 1.