Abstract: In the present investigation, The Upper Miocene biostratigraphy has been recognized in an area ofabout 100 sq. km. between Incipinan-Kurtkuyu west of Sinop Peninsula.The examination has been carried out at 106 samples, taken from four measured stratigraphic sections and twodrill-hole logs. In the Miocene sequence of the region with about 500 m of thickness representing, the marine and upward the continental transitional environments have been recognized five ostracode biozones.The choronostratigraphy of Neogene in the region using the stratigraphic distribution of characteristic ostracodesin the biozones of Turkey and other Tethys and Paratethys basins has been determined. Therefore the sequence at thebottom has been deposited during Meotian and the upper part of the sequence has been formed during Pontian. MarineMeotian deposits which has characteristic of the Tethys and Paratethys bioprovince has been determined and fresh waterPontian deposits which has characteristic of only Paratethys bioprovince has been established.