The OligoceneeMiocene Qom Formation has different depositional models in the Central Iran,SanandajeSirjan and Urumieh-Dokhtar magmatic arc provinces in Iran.The Kahak section of the Qom Formation in the Urumieh-Dokhtar magmatic arc has been studied,in order to determinate its microfacies,depositional model and sequence stratigraphy.The textural analysis and faunal assemblages reveal ten microfacies.These microfacies are indicative of five depositional settings of open marine,patch reef,lagoon,tidal flat and beach of the inner and middle ramp.On the basis of the vertical succession architecture of depositional system tracts,four third-order sequences have been recognized in the OligoceneeMiocene Kahak succession of Qom Formation.Based on the correlation charts,the transgression of the Qom Sea started from the southeast and continued gradually towards the north.This resulted in widespread northward development of the lagoon paleoenvironment in the Aquitanian-Burdigalian stages.Also,the sequence stratigraphic model of the OligoceneeMiocene Qom Formation has an architecture similar to those that have developed from OligoceneeMiocene global sea level changes. The Oligocenee Miocene Qom Formation has different depositional models in the Central Iran, Sanandaje Sirjan and Urumieh-Dokhtar magmatic arc provinces in Iran. The Kahak section of the Qom Formation in the Urumieh-Dokhtar magmatic arc has been studied, in order to determine its its microfacies, depositional model and sequence stratigraphy.The textural analysis and faunal assemblages reveal ten microfacies.These microfacies are indicative of five depositional settings of open marine, patch reef, lagoon, tidal flat and beach of the inner and middle ramp. On the basis of the vertical succession architecture of depositional system tracts, four third-order sequences have been recognized in the Oligocenee Miocene Kahak succession of Qom Formation. the basis of the correlation charts, the transgression of the Qom Sea started from the southeast and discontinuous gradually toward the north. his resulted in widespread northward development of the lagoon paleoenvironment in the Aquitanian-Burdigalian stages.Also, the s equence stratigraphic model of the Oligocenee Miocene Qom Formation has an architecture similar to those that have been developed from Oligocenee Miocene global sea level changes.