Study of Oligosteginids palaeoenvironment of the Sarvak Formation in Tang-e-Chenarbashi, Southwest Ilam

712 meters succession of the Sarvak Formation in Tang-e-Chenarbashi indicates a pelagic facies and contains encompasses Middle Albian to Cenomanian planktonic foraminifera and Oligosteginids. In this study, Oligosteginids indicated that they are not present in deep and high energy shallow water, or they have a very low abundance in such environments. Therefore, best probable depth for oligosteginids is upper portions of shelf margin. The genera Cadosina & Colomiosphaera are reported for the first time from Iran and it seems that they adapted to high depths.