In a complete succession obtained from southeast of Birjand, in the Eastern part of Iran, the open marine sediments have been deposited without any disconformity from Paleogene to early Neogene systems. We conducted the biostratigraphic investigations within this sedimentary succession according to calcareous nannofossils from the Roobiat Village section. Based on the calcareous nannofossil species index, we have detected the NP16 to NN3 zones and subzones which are comparable with the Martini biozonation pattern. Thus, we could suggest a middle Eocene (Bartonian) to early Miocene (Burdigalian) age for this section. Since the studied section contains a complete sedimentary sequence from Paleogene to Neogene systems, as a comparisonal section for the correlation between bio-horizons from western parts of the Tethys basin and its eastern parts, it is recommended.