In the present study, the sediments of the Gurpi Formation in the Jafarabad section located in the southeast of Ilam were examined from the point of view of calcareous calcareous nannofossils. The sediments of the upper part of Gurpi Formation with a thickness of about 42 m are composed of limy marl sediments. In this study, 34 species belonging to 22 genera from the group of calcareous nannoplankton were identified. In this formation, based on recorded bio-events, bio-zones CC25 (UC19^TP-UC20a^TP) to (CC26 (UC20b^TP, UC20c^TP, UC20d^TP in sediments belonging to the Upper Cretaceous followed by the bio-zone, NP4 (CNP6-CNP7), NP5 (CNP7-CNP8), NP6 (CNP8) were identified from Paleocene sediments in the upper part of the Gurpi Formation. According to the determined bio-zones, the age of the upper part of Gurpi Formation, late Maastrichtian (Cretaceous) to late Selandian (Middle Paleocene) was identified. In the present study, based on the absence of registration of NP1, NP2, NP3 bio-zones and the lack of fossil data, the boundary between Cretaceous and Paleogene in the upper part of this formation is proposed to be discontinuous. In addition, based on the record of bio-events from the group of calcareous nannofossils, which confirm the warm climate, the conditions prevailing in the sedimentary basin at the time of sedimentation of the Gurpi Formation are inferred with warm climate.