lithostratigraphy and biostratigraphy of the permian deposits in sangsar section, north of semnan, eastern alborz

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).