Biofacies, depositional model, and sequence stratigraphy of the Asmari Formation, Interior Fars sub-zone, Zagros Basin, SW Iran

To interpret the biofacies, depositional model, and sequence stratigraphy of the Asmari Formation in Western Interior Fars sub-zone, one stratigraphic section with 407 m was studied in Sefidar anticline. The studied area is located in Simply Folded Zagros Zone. The Asmari Formation in the studied section is Rupelian-Chattian (Oligocene) in age. The distribution of the Oligocene larger benthic foraminifera indicates that shallow marine carbonates of the Asmari Formation at the studied area deposited in the photic zone and oligo-mesotrophic conditions in tropical-to-subtropical waters. In this study, nine different microfacies were recognized, which are formed in lagoon, shoal, and open-marine sub-environments corresponding to inner and middle ramps. The lower parts of the Asmari Formation are dominated by lagoonal microfacies; in the middle parts, the open-marine microfacies are prevailed; and the upper parts are mainly deposited in lagoonal settings. Three third-order sequences were identified based on the deepening and shallowing patterns in microfacies and foraminifera distributions.