Calcareous nannofossil biostratigraphy and paleoecolgy of the Rupelian-Chattian stages (Oligocene) in the Central Iran basin

Abstract

Calcareous nannofossils are one group of microfossils that use in biostratigraphy studies since the 1950âs and 1960âs. Recently, because of the potential of nannofossil species for age determination, several authors use this fossil-group in the study of Cenozoic sediments and rocks. Here, we present a nannofossil biozonation based on biostratigraphic information from the Sabzevaran section (Central Iran). The Sabzevaran section mainly consists of marl, limestone, and shaly limestone. Based on index nannofossil species, three nanno-bizones (NP23-NP25) were recognized in this section. According to the identified biozones, the age of the studied deposits in the Sabzevaran section is middle to late Oligocene (Rupelian to Chattian stages). In this section, calcareous nannofossils abundance and diversity are medium to low with a sharp decrease slightly near the conglomerate and sandstone layers and are absence in conglomerate and sandstone beds. Paleoecological data indicate the shallow marine, low latitude and low productivity for the marine deposits of Sabzevaran section.