Palynofacies-based sequence stratigraphy of the Upper Cretaceous strata (Abderaz Formation) in east of Koppeh-Dagh Basin, Northeast of Iran

The Upper Cretaceous strata were studied in a composite stratigraphic section named here Padeha-Baghak section in east of Koppeh- Dagh basin, north east of Iran. In this study, palynostratigraphy, palynofacies and depositional environment history of Abderaz Formation were integrated with sequence stratigraphy. Determination of sea level history and sequence units of the Abderaz Formation using sedimentology data is accompanied with many problems due to uniform deposition of this formation in moderately deep parts of the basin. Hence, using the fossil evidences together with sedimentology information, sequence units of this formation have been splitup. For this purpose, 127 rock samples were collected and studied. Studies of planktonic foraminifera and dinoflagellate cysts suggested a late Turonian-early Campanian age for this formation. Palynofacies parameters such as frequency and diversity of dinoflagellate species and the ratio of continental to marine constituents (CONT/MAR ratio) have been used for interpretation of the sequence stratigraphy of the formation. The ratios of amorphous organic matter to Marine Palynomorphs (AOM/MP), and Chorate to Proximate, Proximochorate, Cavate (C/PPC) and peridinioid to gonyaulacoid dinocysts (P/G) reflect the changes in sea level throughout the studied section. According to these studies, five palynofacies have been recognized. The record of sea level changes in the shales and marls of this section shows seven third – order sequence with six sequence boundary (type II), The interpreted sea-level curve in the Koppeh-Dagh basin can be correlated with late Cretaceous global curves.