Biostratigraphy of the Ilam Formation in Kabir Kuh and Sourgah Anticlines and Comparison with the Type Section

For biostratigraphy of the Ilam Formation، in Surgah and Kabirkuh anticlines، 2 sections of Mehdiabad and Holostem - Poshte were selected and sampled. The thickness of the Ilam Formation in Mehdiabad and Holostem - Poshte sections are 183 and 66 meters respectively and main lithology includes limestone، shale and argillaceous limestones with intercalation of shale. The lower and upper boundaries of the Ilam Formation with Surgah and Gurpi formations are conformable with sharp lithology changes. For biostratigraphic studies 36، species belong to 15 genus of formaminifera were recognized and 4 biozones based on Premoli Silva & Verga (2004) biozonation were identified. These include: 1. Dicarinella concavata zone 2. Dicarinella asymetrica zone3. Globotruncanita elevata zone 4. Globotruncana ventricosa zone Based on these biozons، the age of the Ilam Formation in both sections is Santonian – early Middle Campanian. In this study، the Ilam Formation in Mehdiabad and Holostem – Poshteh sections were compared with type section.