In order to use the foraminiferal contents for biostratigraphy and age dating, chronostratigraphy and explanation of some evolutionary trends the well-known foraminifera rich Abderaz Formation of the Kopeh-Dagh basin in northeastern Iran was sampled at the type section. The 300 meters thick section is mainly made up of grey shales and marls with two units of chalky limestone in the upper part. The lower contact of the formation with Aitamir Formation is disconformable while the upper contact with Abtalkh Formation is continuous. Fifty nine species belonging to 18 genera were identified and four biozones identical to those established more recently for the Tethyan were erected and compared with the existing biozonation. The biozones are quite correlatable through with minor changes in the boundaries. Based on these, an age of middle Turonian-early Campanian is quoted to the formation. The Neoflabellinids can be used to mark the Coniacian-Santonian boundary. Neoflabellinids has world-widely been distributed during the Coniacian-Santonian time. Four species of Neoflabellina including N.suturalis, N.praerugosa, N.gibbera, N.praecursor were identified. The N.gibbera and N.praecursor appear at the very base of the Santonian stage differentiating therefore, the Coniacian-Santonian boundary. The findings of this study is quite correlatable with those from the Global Standard Stratotype Section and point (GSSP).

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