Microfacies، Sedimentary Environment and Sequence Stratigraphy of the Qom Formation، Deh Namak، Northwest of Garmsar

Deh Namak section is exposed along the most northern point of the Qom Formation¡ where the Central Iran zone and Alborz zone come together. The study of microfacies¡ sedimentary environments and sequence stratigraphic features of the Qom Formation in this area can help to understand the situation of the Qom sedimentary basin in the northern part¡ bordering the Alborz zone. 166 samples of the Qom Formation in Deh Namak section in the northwest of Garmsar are investigated. Microfacies analysis of these sedimentary rocks indicates that according to sedimentary environment they consist of nine microfacies belonging to four facies belts including tidal flat¡ agoon¡ shoal/reef sediments and slope of platform. Due to the absence of the gravitational and turbidity sediments and abundance of reef/shoal sediments¡ a rimmed carbonate shelf depositional environment is suggested in which more sediments were precipitated in shallow water. In this model¡ deep facies of the basin did not spread and the deepest facies belong to the slope. Also¡ sequence stratigraphic studies show that the Deh Namak section is composed of four sedimentary sequences of third- order¡ two types II and one type I sequence boundaries were recognized in this formation.