Palynostratigraphy, Palynofacies and Paleoecology of the Sarcheshmeh Formation at Toos well #1, East of Koppeh-Dagh

The Sarcheshmeh Formation is a shaly sequence of Lower Cretaceous age (Aptian) which is deposited in Koppeh-Dagh sedimentary basin and conformably overlies and underlies the Tirgan and Sanghaneh formations respectively in the Toos well # 1. Lithologically، this formation has a thickness of 177m and consists mainly of marl، shale and shaly limestone. Palynological studies resulted in identification of 18 genera and 31 species of dinoflagellate cysts. They were classified in Odontochitina operculata biostratigraphic zone that shows the Aptian age. Based on palynological factors، three types of palynofacies (II، IV and VI) have been identifies. From the palynofacies and paleoecological evidences it can be concluded that the sedimentary environment was a shallow and oxic inner platform at the beginning، but gradually turned to a dysoxic outer neritic shelf at the termination of the formation.