The Early Miocene Qom Formation depositional setting; Northwest of Central Iran Basin

Authors : Hamideh Noroozpour

Pages : 121-137

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Publication Date : 2022-07-28

Article Type : Research

Abstract :An outcrop of the Qom Formation (Fm.) is considered to determine the depositional setting model in the northwest of Central Iran. Field observations show that the Qom Fm. is composed of thin to thick-beds limestone along with alternation of green marl and argillaceous limestone. Based on the stratigraphic distribution of foraminifera, Borelis melocurdica-Borelis melo melo Assemblage Zone has been recognized in the Qom Fm.. Consequently, the Burdigalian in age is offered for the Qom deposits. A careful study of the characteristics of biological facies and sedimentary textures is specified eight facies types concerning the four facies belts of the lagoon, reef, slope, and open marine. Lacking in the sediment gravity flows and turbidity facies, and high abundance of reef facies (25 percent of Qom deposits) including coral boundstone, algae, and bryozoans, reflect likely a deposition on an open shelf. Facies distribution chart shows that the Qom Fm. sedimentation had began in the continental slope depositional setting over Aquitanian? without considering the possible erosion processes. However vigorous sea level fluctuations had occurred during Aquitanian-Burdigalian. Hence, active tectonic can be proposed for study area over Early Miocene.
Keywords : facies, depositional setting, Qom, Burdigalian, Central Iran