ABSTRACT: The Surgah Formation was studied in four sections (Kuh-e-Surgah anticline, Zifel, Sarkan, and Mal-e-kuh) from the NW-SE of the Zagros sedimentary basin. Forty-one planktonic foraminiferal species belonging to 20 genera were observed. The recorded species were used to subdivide the Surgah Formation into three biozones: Marginotruncana sigali-Dicarinella primitiva Zone, Dicarinella concavata Zone, and Dicarinella asymetrica Zone. Based on these data, the Surgah Formation was estimated to be of late Turonian to late Santonian age. The Coniacian/Santonian boundary is placed at the Dicarinella asymetrica Zone. The base of the Santonian stage is identified on the FO of Globotruncana linneiana (pill box shaped), the FOs of Dicarinella asymetrica, Globotruncanita elevata and Globotruncana bulloides, and the LOs of Dicarinella primitiva, Dicarinella concavata and Muricohedbergella flandrini.