Investigation of the sedimentary environment, sequence stratigraphy, and geochemical parameters of the Kazhdumi Formation (Aptian-Albian) in the Tang-e-Maghar outcrop, Bangestan Anticline, Zagros Basin

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Document Type : Research Paper

Authors

1 Department of Sedimentary Basin and Petroleum, Faculty of Earth Sciences, Shahid Beheshti University

2 Department of Sedimentary Basin and Petroleum, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

3 Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta T6G 2E3, Canada

Abstract

The Kazhdumi Formation is considered one of the most influential elements of the Middle Cretaceous–Early Miocene petroleum system and predominantly plays the role of source rock in most areas of southwestern Iran. This formation in the Tang-e Maghar outcrop is 242 meters thick and consists of shale, shaly limestone, and interbedded thin to medium limestone and argillaceous limestone. Studies conducted have led to the identification of 12 microfacies, which were deposited in three sub-depositional environments: outer ramp, hemipelagic, and pelagic. The depositional environment at the onset of this formation's sedimentation was a distally steepened carbonate ramp, which later transitioned into an organic-rich intra-shelf environment. By integrating all obtained data and information, five third-order depositional sequences have been identified in the Aptian–Albian sedimentary succession of this section. The geochemical characteristics of major and trace elements in the sediments of the Kazhdumi Formation indicate that the original carbonate mineralogy was aragonite. Plotting the major and trace element values (Fe, Mn, Sr, Na, Ca, Mg) against each other and comparing the results with the ranges proposed by various researchers indicates that the sediments of this formation were deposited under reducing conditions and were subjected to diagenesis within a closed to open diagenetic system. The variations in iron and manganese contents are correlated with the distribution of facies associations and sequence surfaces of the Kazhdumi Formation, such that the highest and lowest concentrations of these elements correspond to the maximum flooding surfaces and sequence boundaries, respectively.

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Journal of Stratigraphy and Sedimentology Researches

Articles in Press, Accepted Manuscript
Available Online from 28 September 2026

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