Calcareous Nannofossils of the Gurpi Formation in Marun Oil Field

In the present study, calcareous nannofossil of the Gurpi Formation have been studied from well No. 123 of Marun oil field in the Zagros sedimentary basin. In this study, thirty-eight nannoplankton species belonging to eighteen genera were introduced from the Gurpi Formation deposits. Based on index calcareous nannofossil species, the Gurpi Formaation deposit was subdivided into nine calcareous nannofossil biozones, including CC17- CC25 zones (Sissingh, 1977) and UC12-UC20 (Burnett, 1998). The identified biozones are assigned to the Late Santonian-Late Maastrichtian ages for the studied interval. In order to paleoecology and Paleoenvironment studies, the diversity, abundance, size and extent of preservation of nannofossil taxa were also investigated. The distribution and abundance of some species such as Micula decussata, Micula murus and Watznaueria barnesiae indicate that the temperature and environmental stress have increased towards the end of the Formation. Also, the sedimentary environment of Gurpi Formation during the Late Cretaceous was mainly in low to mid-latitudes based on calcareous nannofossil assemblages.