Stratigraphy of the Limestone Unit of Pabdeh Formation in Bankul section (Northeast Ilam), Lorestan Zone

In the present study, the limestone unit of the Pabdeh Formation was investigated in Bankul  stratigraphic section in the northeast of Ilam and compared with other outcrops of this unit. The studied unit is 73m in thickness and formed by thin to medium -bedded limestone. According to the identified index microfossils, four biozones were recorded: 1) Assemblage Zone 1, which is equivalent to the upper part of Acarinina topilensis Partial Range Zone; 2) Morozovelloides lehneri Partial Range Zone; 3) Orbulinoides beckmanni Taxon Range Zone. As a result of this study and based on the identified planktonic foraminifera, the age of the middle part limestone of the Pabdeh Formation is Lutetian –Bartonian and correlated to the Shahbazan Formation. The sedimentation of this unit has been contemporary with global temperature decrease and eustatic sea level decrease. Meanwhile, the limestone unit at the base of the Pabdeh Formation in the Early Eocene age in the south of Lorestan has a shallow facies and is equivalent to global warming and rising eustatic water level. This was the same condition in Izeh zone. In the north of Dezful, there was the opposite of these conditions, so that in the Middle Eocene, the limestone unit of Pabdeh Formation had a shallow facies. This difference in facies has probably been influenced by various tectonic movements in the Lorestan foreland zone.