OICC Press Iranian Journal of Earth Sciences 2228-785X 14 3 2021 06 15 Diversity of the Early-Miocene (Burdigalian) Ostracoda from Northeastern Semnan, Central Iran 196 209 10.30495/ijes.2021.1919627.1581 EN Alireza Chegini Pasargad Company, Tehran, Iran Iraj Maghfouri Moghaddam Department of Geology, Faculty of Science, Lorestan University, Lorestan, Iran Hassan Bahramizadeh Sajjadi Department of Geology, Petro Gostar Permayoon (PGP), Tehran, Iran Journal Article 2021 06 15 Seven genera and seventeen species of marine Ostracoda are reported for the first time from the Attari section (Qom Formation), northeast of the Semnan, Central Iran. In this section, the Qom Formation outcrops with 280 m thickness lies on the Eocene volcanic and under the Upper Red formation. According to the distribution of index foraminifera, there is conspicuous similarity between larger bentic foraminifera assemblages of the Qom Formation foraminifera and those of the Zagros basin, such as Borelis melo curdica the age of Qom Formation in the Attari section is Early Miocene (Burdigalian). The Miocene and even Oligocene Ostracoda fauna, relatively similar to the Attari section, have been reported from the Mediterranean area and the Proto- Indo- Pacific Ocean. The presence of one species with Paratethian origin in the Qom Formation is strong evidence that during the Burdigalian stage, the sea way between Central Iran and Paratethys basin still existed.