Biostratigraphy of the Surgah Formation in Shah Nakhjir Anticline Section (South West of Ilam) Based on Planktonic Foraminifera and Correlation with Type Section

In order to study of the Surgah Formation in Southwest of Ilam City, one section in the Shah Nakhjir anticline was selected. The thickness of the Surgah Formation is about 161 meters and consists mainly of green shales and olive green marly shales with intercalation of gray shaly limestones. The lower and upper boundaries of the Surgah Formation are the Sarvak and Ilam Formation, respectively and are conformable with sharp lithology and abundant iron nodules. In this study, 52 species belonging to 28 genuses of foraminifera and 3 biozones were identified. Based on the planktonic foraminifera and identified biozones, the Surgah Formation has an age of Late Turonian to early Late Santonian. Comparison of biozones identified in this section with those of the type section in Tang-e- Garab shows that these two sections are similar in biozones and age, and the only difference is in thickness of biozones.