<p>This research aims to investigate and reconstruct the sedimentary paleoenvironment of the Upper Aptian to Upper Albian deposits in the Zagros Basin, southwestern Iran. To achieve this, the Kalgeh Amir Sheikhi (KAS) section of the Kazhdumi Formation, situated in the eastern Izeh Zone, was selected for analysis. In this section, thickness of the Kazhdumi Formation is 135&#xa0;m and is composed of fossiliferous limestone and dark shales. Its lower boundary with the Dariyan Formation is unconformity, whereas its upper boundary with the Sarvak Formation is in a continuous sequential manner. Nine microfacies have been identified and deposited along platform margin, slope, outer shelf, and basin. The microfacies of the Kazhdumi Formation in this section contain F1: Laminated Organic-Rich Shale, MF2: Radiolaria Wackestone-Packstone, MF3: Planktonic Foraminifera Radiolaria Wackestone-Packstone, MF 4: Planktonic Foraminifera Wackestone-Packstone, MF 5: Planktonic Foraminifera Oligosteginid Wackestone-Packstone, MF 6: Oligosteginid Packstone, MF 7: Planktonic Foraminifera Oligosteginid Intraclast Packstone, MF 8: Peloid Planktonic-Benthic Foraminifera Packstone and MF 9: Peloid Intraclast Grainstone. These microfacies indicate that the studied sequence was deposited in an intrashelf environment. The formation of this intrashelf setting resulted from seabed subsidence in the central Zagros, primarily due to the activity of the Kazerun Fault system during the Aptian, followed by the influence of the Hendijan Fault in the Late Aptian, which led to a rapid increase in accommodation space.</p>