A review of the elemental composition and redox conditions of Oligocene organic matter-rich deposits, Western Anatolia Turkey

Abstract

Organic matter-rich deposits of the Oligocene Hayrettin Formation, Denizli, West of Turkey, may considered as a carbonaceous interval within a succession dominated by mudstone and sandstone. Samples were investigated to determine the source rock composition and provenance, and redox conditions of the depositional environment. Carbonaceous rocks are characterized by high organic carbon (2.12-34.35 wt. %) contents and by significant enrichments of several trace elements (Co, Cr, Mo, Ni, Pb, S, Th, U and V) relative to average shale. According to La/Th versus Hf diagram, Al2O3/TiO2 ratios, and Cr/Ni, Th/Co, Th/Cr, and Cr/Th ratios indicate that the sediment was derived from intermediate source rocks in addition to being an important contribution of detritus. Average CIA, PIA and CIW values imply intense weathering of the source terrane. K2O/Na2O, SiO2/Al2O3 and K2O/Na2O ratios and bivariate discriminant functions diagram indicate that most samples in the active continental margin. Ni/Co, V/Cr, and U/Th ratios of the studied samples suggest that the redox conditions of depositional environment are oxic.