پالئواكولوژي روزن بران سازند قم در برش قصر بهرام، دامنه هاي شمال غربي سياه كوه، واقع در جنوب گرمسار

Paleoecology of Foraminifera of the Qom Formation in Ghasr-e- Bahram Section, Northwest Part of Siahkuh, South Garmsar

A total 191 samples of the sediments of the Qom Formation in northwest part of Siahkuh were investigated. The Qom Formation, in the examined section with a thickness of 359m., mainly consists of argillaceous limestone, limestone, marl and gypsy marl and disconformably overlies the Lower Red Formation and underlies the sediments of the Upper Red Formation. A study of foraminifera was led to identifying 50 genera and 79 species from benthonic and plankthonic foraminifera. Based on the occurrence of the index foraminiferal species and their stratigraphic distribution, the age of the Qom Formation in the studied section is Early Miocene (Aquitanian to Burdigalian). Study of assemblage, abundance, and species diversity of foraminifera in the examined samples shows noticeable changes in the paleoenvironmental conditions, and species diversity of foraminifera is decreased and increased through the studied section. The maximum diversity is nineteen species. On the basis of species diversity, the mentioned section is classified to seven assemblages A to G. The abundance of foraminifera in each assemblage indicates that species the sediments of the Qom Formation belongs to marine and shelf (lagoon to outer shelf) environments.