Investigating the reliability of Gamma Deviation log in sequence stratigraphic studies: Dariyan Microfacies, depositional environment, sequence stratigraphy and diagenetic process affected the Doroud Formation in the Eram Section (south Neka), north flank of central Alborz

The Permian deposits (Doroud Formation) are exposed in a wide area of central Alborz. A stratigraphic section of Permian deposits in the Eram section (South Neka) has been selected for the study of facies, depositional environments, sequence stratigraphy, and diagenetic processes. The 320 m thick Doroud Formation in the study area mainly consists of intercalation of limestones and sandstones. Field and petrographic studies of thin sections led to identifying four siliciclastic petrofacies and three carbonate microfacies. These facies are deposited in four facies belts, including fluvial, coastal, lagoon, and shoal. The low diversity of facies and the gradual change of facies belts, the absence of turbidites, and the absence of large barrier reef indicate that the Permian deposits in the study area were deposited on a carbonate ramp. Also, based on the absence of turbidite deposits of a deep marine environment, it can be deduced that the depositional environment of the Doroud Formation is homoclinal. Two third-order depositional sequences have been identified in the studied interval of the Doroud Formation. Different diagenetic processes have been affected on the studied interval in the study area, most notably dolomitization, cementation, mechanical and chemical compaction, pyritization, fracturing, and neomorphism.