Sequence Stratigraphy and Sea Level Fluctuations of the Ab-Deraz Formation, Based on Palynological Evidence and Magnetic Susceptibility Method “Kopet-Dagh Sedimentary Basin, Northeastern Iran”

Abstract

Ab-deraz Formation is one of the Lithostratigraphic units of upper cretaceous (Middle TouronianSantonian) in Kopet-Dagh sedimentary basin, located in northeastern Iran. The aims of this study are separating sequence units and determining sea level Fluctuation by using palynological factors and comparison via magnetic susceptibility which is used for the first time in Ab-deraz Formation. Assuming the average MS magnitude as the proxy for mean sea level changes, positive Magnetic Susceptibility (MS) values were considered to present sea level falls and negative values for sea level rises. Based on these data a curve showing water level fluctuations throughout the stratigraphic column was prepared which shows a general trend of regression from base to the top of the formation. To test accuracy of this method, magnetic susceptibility results were compared with those gained from palynology and palynofacies studies. Based on the changes in palynological factors (the terrestrial/marine particles ratio, C/PPC ratio, diversity and abundance of dinoflagellate), palynofacies, for separate sequences, three sequences of the third type with four sequence boundaries, (3 boundaries of the type II and one boundary of the type I) were differentiated, confirming the results gained from magnetic susceptibility method.