OICC Press Iranian Journal of Earth Sciences 2228-785X 2026 07 14 The Impact of the Hendijan Fault on Formations Located at the Border of the Aghajari and Pazanan Oil Fields (Paleo-highland Setting, Eastern Tethys) 10.57647/ijes.2027.14881 EN Saeedeh Senemari Imam Khomeini International University, Qazvin, Iran Behzad Saeedi Razavi Construction and Minerals Research Group, Technology and Engineering Research Center, Standard Research Institute (SRI), Karaj, Iran Maryam Al-Sadat Mirkamali Imam Khomeini International University, Qazvin, Iran Journal Article 2026 07 14 In this study, the Gurpi Formation was studied in one of the wells of the Aghajari oil field. The thickness of the Gurpi Formation in this well is 130 meters, and 65 thin sections of its drilling cores were examined. The main lithology of this formation in the aforementioned well includes argillaceous limestone, marly limestone, shale, and marl. In this research, thirty-three species belonging to thirteen genera of foraminifera and four biozones were identified. To determine the boundaries of biozones, classification was performed by studying thin sections, in which the criteria of first appearance and last occurrence of indicator species were used. The designated biozones are: Dicarinella asymetrica Zone, Globotruncanita elevata Zone, Radotruncana calcarata Zone, Gansserina gansseri Zone. In this study, the Contusotruncana plummerae Zone is absent and can therefore only be explained by a sedimentary hiatus or faulting. Based on the identified biozones, the age of the Gurpi Formation in the studied well is suggested to be from the Late Santonian to Middle Maastrichtian. The Gurpi Formation is covered in its upper part by shales of the Pabdeh Formation. In the lower part of this formation, the Sarvak Formation is located, and the Ilam Formation is absent. By determining the status of the lower part of the Gurpi Formation using biostratigraphic data, we were able to justify the absence of the Ilam Formation based on the activity of the Hendijan Fault. Therefore, in paleo-highland setting, such as the boundary of the Aghajari and Pazanan oil fields, the decrease and increase in sediment thickness on both sides of the fault can have a significant impact on the distribution of different rocks, especially source and reservoir rocks.