Calcareous nannofossils biostratigraphy of the Campanian-Danian interval, Gurpi Formation in the Zagros Basin, SouthWest Iran

This study presents calcareous nannofossils biostratigraphy of the Campanian‒Danian interval at the Gurpi Formation in the southwest of Ilam Province, in the Zagros Basin. The studied sequence of the Gurpi Formation mainly consists of marly shale and limestones. The thickness of Gurpi Formation was measured as approximately 230 m. Forty-five species belonging to twenty-eight genera were recorded in these strata. The biostratigraphy based on calcareous nannofossil assemblages allows the identification of nannofossil standard zones such as CC18b, CC19, CC20, CC21, CC22, CC25b,‌c and CC26b, that equivalent to UC14cTP - UC20dTP for Cretaceous, and NP2 - NP3 (equivalent with CNP2, CNP3 and lower part of CNP4) for the Paleogene strata in the Gurpi Formation. The studied section spans the early Campanian to early late Campanian with good continuity. A biostratigraphic gap is identified in the late late Campanian to early Maastrichtian (CC23, CC24, and CC25a), across the late Maastrichtian (CC26a) and at the early Danian (NP1).