Biostratigraphy of Kazhdumi Formation in Naghsh-e- Rostam Mountain

Abstract

The Kazhdumi Formation (Albian - Cenomanian) is one of the rock units of Bangestan group that is located in the Zagros Folded Zone. In this study the Kazhdumi Formation has a thickness of 222 m. The boundary between Kazhdumi and Dariyan formations is disconfirm, which is characterized by Iron oxide and glauconite layers which shows epirogeny that is confirmed by paleontological evidences. The presence of some foraminifera such as Nezzazatinella picardi, Scandonea sp., Daxia cenomania, Choffatella sp., Pseudolituonella reicheli together with calcareous algae, such as Lithocodium aggregatum in the Sarvak Formation, represent an early Cenomanian age. The microfossils in Kazhdumi Formation are: Ammobaculites goodlandensis, Marsonella trochus, Hemicyclammina sigali, Praechrysalidina infracretacea, Orbitolina (Orbitolina) concava, Orbitolina (Conicorbitolina) conica, Orbitolina (Orbitolina) subconcava, together with calcareous algae such as: Neomeris cretacea, Salpingoporella sp., Trinocladus tripolitanus, Permocalculus irenae, Dissocladella deserta. Based on assemblage zone of foraminifera and calcareous algae, 6 different biozones were recognized, which are: Dictyoconus arabicus ass. zone; Salpingoporella annulata concurrent zone; Hemicyclammina sigali ass. zone; Orbitolina (Orbitolina) subconcava ass. zone; Nezzazatinella picardi ass. zone; Lithocodium aggregatum ass. zone.