Sequence stratigraphy and depositional environment of the Oligocene deposits at Firozabad section, southwest of Iran based on microfacies analysis

Abstract

The Asmari Formation was deposited in the foreland basin of southwest Iran (Zagros Basin). Carbonate sequences of the Asmari Formation consist mainly of large benthic foraminifera along with other skeletal and non-skeletal components. Three assemblage zones have been recognized by distribution of these large foraminifera in the study area that indicate Oligocene age (Rupelian-Chattian). Absence of turbidite deposits, reefal belt and gradual facies changes indicate that the Asmari Formation was deposited in a carbonate ramp environment. Based on analysis of large benthic foraminiferal assemblages and microfacies features nine different microfacies have been recognized, which can be grouped into three depositional environments: inner, middle and outer ramp. Based on the microfacies analysis and sequence stratigraphic studies, two third-order sequences in Firozabad section were identified.