摘要：To review of the Ilam Formation in Zagros Basin, the cut of southeast of Khorramabad (Southwest Iran) is studied under biostratigraphy and lithostratigraphy. A total of 99 rock samples were collected. In this study 31 species from 10 genera identified and introduced. The Ilam Formation in the study section has 360 m thickness, and is formed mainly from limestone alternating thin layers of limestone and clay limestone thick layer of light gray to dark between layers of shale. This formation is continuously and gradients, on Surgah Formation and below Gurpi. Foraminifera microfauna rich in this formation represents the upper Turonian and Campanian beginning, and based on the above Microfauna 4 Biozone was recognized for Ilam Formation. Biozone 1: Marginotruncana sigali-Dicarinella primitiva partial range zone, The Upper Turonian age, Biozone 2: Dicarinella concavata interval zone, Upper Turonian until the end Coniacian, Biozone 3: Dicarinella asymetrica total range zone, is Santonian age, and Biozone 4: Globotruncanita elevate partial range zone, early Campanian age. According to identified biozones Ilam formation age in under study cutting is the end of Upper Turonian to early Campanian.
