Biostratigraphic correlation of the transition of Maastrichtian–Thanetian based on calcareous nannofossils and planktonic foraminifera in Fars province, Zagros (Eastern Tethyan realm)

This study focuses on late Campanian–early Thanetian calcareous nannofossils and foraminifera assemblages from the Gurpi and Pabdeh formations in the Fars province (SW Iran). To conduct biostratigraphic studies, the upper part of the Gurpi Formation and the lower part of the Pabdeh Formation were studied in Morgah stratigraphic section in Fars province. In this section, the upper part of the Gurpi Formation with 63 m thickness is mainly composed of gray argillaceous limestones and shale. Also, the base of the Pabdeh Formation includes 7 m of purple shales and argillaceous limestones. The upper boundary of the Gurpi Formation is also discontinuously associated with purple shales at the base of the Pabdeh Formation. In the biostratigraphic studies of the upper part of the Gurpi Formation, while identifying 29 species belonging to 20 genera of calcareous nannofossils, five biozones were identified. In addition, in biostratigraphic studies of the lower part of Pabdeh Formation, while identifying six species belonging to five genera of calcareous nannofossils, one biozone was identified. Based on the identified biozones, the transition of Gurpi Formation to the Pabdeh Formation in the studied section of Late Maastrichtian–Thanetian was determined. Also, based on a study based on planktonic foraminifera, four biozones were identified in the transition deposits of the Gurpi Formation to Pabdeh Formation. Biostratigraphic studies eventually led to a correlation between the two fossil groups.