Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Biostratigraphy & Paleoenviroment of the Qom Formation in Northeast of Mahneshan

Document Type : Original Research Paper

Authors
J. Daneshian 1
M. Shahrabi 2
M. Akhlaghi 3
1 Department of Geology, Tarbiat Moallem University, Tehran, Iran
2 Zarnab Co., Tehran, Iran
3 Department of Geology, Science Faculty, Tarbiat Moallem University,Tehran, Iran.
10.22071/gsj.2010.55643
Abstract
75 samples of the Qom Formation in Andabad, northeast Mahneshan, were investigated. The Qom Formation in the examined section with a thickness of 301m, mainly consists of limestone and marl, and disconformably overlies the Lower Red Formation and lies under the sediments of the Upper Red Formation. A study of foraminifera was led to identifying 42 genera and 70 species of the benthonic and plankthonic foraminifera, which 37 genera and 57 species is reported from this area for the first time. Among them, benthonic foraminifera have more varieties and abundances, and used for biostratigraghy. Based on the identified foraminifera, the Andabad section is comparable to Assemblages Zone 1 and 2 introduced by Adams and Bourgeois. On the basis of occurrence of the index foraminiferal species and their stratigraphic distribution, the age of the Qom Formation in the studied section is Early Miocene (Late Aquitanian to Burdigalian).The assemblage, abundance, and species diversity of foraminifera in the examined samples shows noticeable changes in the paleoenvironmental conditions. The maximum diversity of foraminifera is sixteen species. Based on species diversity, the strata classified to nine assemblages A to I. The abundance of foraminifera in each assemblage indicates that the sediments of the Qom Formation belong to inner shelf environments.
Keywords
Central Iran
Mahneshan
Early Miocene
Biostratigraghy
Paleoenvironment
Foraminifera
Qom Formation
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Scientific Quarterly Journal of Geosciences
Volume 19, Issue 76
Winter 2010
Pages 45-50