facies analysis, depositional environment and sequence stratigraphy of the permian ruteh formation in north of mahabad (nw iran)

The permian ruteh formation is known as one of the most significant successions in northwestern iran. in the studied area itexposed a thick succession (201 m) of medium to thick-bedded carbonate sedimentary rocks in the west of kuseh-kahrizeh village inthe north of mahabad city. this formation unconformably overlain the cambrian mila formation and it is unconformably underlainby the oligo-miocene qom formation the laboratory studies on the thin sections led to the identification of 15 microfacies that arearranged in three facies associations: inner ramp, mid-ramp and outer ramp. the petrographic results and facies analysis demonstratethat the depositional environment of ruteh formation in the studied area exhibits the characteristics of a homoclinal carbonate rampplatform of a gentle slope. this platform is mainly composed of supratidal, intertidal, lagoon, shoal, open marine, mid-ramp, and outerramp environments. according to facies frequency analysis, the lagoon environment accounts for the highest abundance of facies(33%), whearas the outer ramp environment shows the least abundance (2%).vertical distribution analysis of sedimentary facies led tothe identification of transgressive and regressive depositional patterns. accordingly, a total of 4 depositional sequences of third-order,5 sequence boundaries and 4 maximum flooding surfaces were identified. the boundaries between all sequences are identified as sb1.