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”

Farshid Yousefimoghadam,Seyed Mahmood Hoseininezhad,Mohsen Allameh

doi:10.4236/ojg.2015.55024

Farshid Yousefimoghadam, Seyed Mahmood Hoseininezhad + Show 1 more

Open Access

https://doi.org/10.4236/ojg.2015.55024

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Abstract

Ab-deraz Formation is one of the Lithostratigraphic units of upper cretaceous (Middle Touronian-Santonian) 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.

Highlights

The Kopeh-Dagh sedimentary basin formed the middle Triassic orogeny in northeastern Iran [1]
This paper aims to evaluate magnetic susceptibility role in sedimentary sequence analysis and for identification of sequence boundaries and system tracts
The comparison confirms that this method is quite appropriate for determining regressions and transgressions

Summary

Introduction

The Kopeh-Dagh sedimentary basin formed the middle Triassic orogeny in northeastern Iran [1]. A relatively new method is using palynological elements and factors such as biological degradation of palynological particles, roundness and homogeneity of equidimensional phytoclasts [5], the relative abundance of opaque and semi opaque to transparent phytoclasts, the marine palynomorph/terrestrial particles ratio, relative abundance and diversity of dinoflagellate cysts and Chorate/Proximate, Proximochorate, Cavate (C/PPC) morphotype ratio [5]. These factors were used for sequence differentiation in this paper. In order to test accuracy of this method magnetic susceptibility results have been used in conjunction and compared with palynology and palynofacies analysis

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