Provenance of the Siliciclastic Pestehliegh Formation (Early Paleocene) in the Chahchahe section, NE Iran

The Pesteliegh Formation (Lower Paleocene) is composed of 94/5 m of sandstone, shale and evaporate units in the Chahchahe section. Shale samples show that major oxides such as SiO2, Al2O3, Na2O, P2O5 and trace elements like Sr, Ba, Nb and Ce are depleted relative to Upper Continental Crust (UCC) while, U and CaO enriched. The diagram of TiO2 versus Al2O3 and Zr versus Al2O3 suggest an intermediate igneous rock as possible source rock for shale of the  Pesteliegh Formation. The diagram of K2O/Na2O versus SiO2 and ternary diagram of Th/Co/Zr, La/Th/Sc, Th/Sc/Zr show a continental arc islands as tectonic setting for this Formation. The CIA index values reveal poor to moderate degree for intensity of weathering and arid to semi-arid as paleo-climate in the studied area. In the other hand, the U/Th and Ni/Co indexes indicate oxidant condition in depositional environment. The beginning of Paleocene was along with tectonic activity and regression of sea level in most parts of the word and well the Kopet-Dagh Basin in Iran. These occurrences were most important factor for deposition of siliciclastic sediments of the Pesteliegh Formation. Due to regression, the thickness of this formation decrease, from south east toward north west in Kopet-Dagh Basin.