Biofacies and palaeoecology of the Jahrum Formation in Lar area, Zagros Basin, (SW Iran)

Document Type : Regular Paper


1 Faculty of Sciences, Department of Geology, University of Isfahan, Isfahan, Iran

2 Faculty of Earth Sciences, Department of Geology, Shahrood University of Technology, Shahrood, Iran

3 Department of Geology, National Iranian South Oil Company, Ahvaz, Iran


Biofacies and palaeoecology of the limestone of the Jahrum Formation in the Lar area in the southwest of Iran (Zagros Basin) is addressed in this paper. Our detailed analysis of biofacies and palaeoecology shows that the Jahrum Formation in the studied area were deposited in a carbonate open shelf dominated by heterozoan and, subordinately, photozoan skeletal assemblages. Based on analysis of larger benthic foraminiferal assemblages and biofacies features, two major depositional environments are identified. These include inner shelf and middle shelf environments. The inner shelf facies is characterized by wackestone-packstone, dominated by various taxa of imperforate foraminifera. The middle shelf is represented by wackestone-packstone with a diverse assemblage of larger foraminifera with perforate wall. The distribution of the larger benthic foraminifera indicates that shallow marine carbonate sediments of the Jahrum Formation at the studied areas have been deposited in the photic zone of tropical to subtropical oceans.