Microbiostratigraphy and paleoecology of the Qom Formation in the Goylar section, southwest of Zanjan Province

A stratigraphic section (155 meter in the thickness) was selected to determine biostratigraphic and paleoecological features of Qom Formation in southwestern Zanjan province, Central Iran geological zone. Field observations show that the Qom Formation is composed of cream to brown, thin-to thick bedded limestone, sandy limestone, alternation of shale and green marl, reef-coral limestone, and green marl and argillitic limestone.According to paleontological studies, a total of 24 genera and 18 species including 17 genera and 9 species of benthic foraminifera and 7 genera and 9 species of planktonic foraminifera have been identified. Based on the stratigraphic distribution of foraminifera, Borelis melocurdica-Borelis melomelo Assemblage Zone (Burdigalian, Early Miocene) has been recognized with certainty for the Qom Formation and 5-meters in the thickness of basal Qom deposits (Lower boundary on volcanic rocks) is considered to be the possible age of Aquitainian (?). Base on paleoecological features including the abundance of fossil assemblages, morpho-types, shell types of benthic and planktonic foraminifera, and the abundance of reef corals along with algal coexistence, the Qom sea has a normal salinity and semi warm to warm in the temperature. Also, light changes in the Qom Sea have been mainly in the Mesophotic-Oligophotic and Aphotic zones. Base on the fauna bathymetry, sedimentation of the Qom Formation has been occurred in a carbonate shelf ? in the lagoon, barrier to the deep open marine depositional setting.