The Permian deposits in the stratigraphic section of Sangsar (located in the eastern Alborz), are the best expose in the Semnan area. This sequence consists of the Doroud (Asselian-Sakmarian), Ruteh (Artinskian-Murgabian) and Nessen (Early Djulfian) formations. The Dorud Formation in the studied section with 56 m thickness consists of conglomerate, sandstone and quartzite, which is disconformity overlies on the Mobarak Formation. The Ruteh Formation with a thickness of 116 m consists of fossiliferous limestones. This formation in the studied section can be subdivided into two rock units that is covered the Doroud Formation with a transitional contact and overlain by bauxite-laterite horizon of the Nessen Formation disconformable. The rich foraminifer fauna of the Ruteh Formation can be established three biozones include the Schubertella-Mesoschubertella Assemblage Zone (Artinskian), Dunbarulla-Codonofusiella Assemblage Zone (Early Murgabian), Pachyphloia-Neoendothyra Assemblage Zone (Late Murgabian).