Deposition characteristics of pliocene coals in the denizli region (SW Turkey) via organic petrography, geochemistry, and stable isotope composition.

The objective of this study is to identify and evaluate the organic geochemical properties, paleo vegetation, and paleo depositional environment of coals in Denizli (SW Turkey). Organic geochemical and petrographic investigations, scanning electron microscopy, X-ray diffractometry, and palynological and stable isotope (δ²H, δ¹³C, δ¹⁵N, δ¹⁸O and δ³⁴S) investigations have been performed. Coal, clayey coal, and coaly claystone samples from the study area have gas and oil production potential according to their total organic carbon (0.59–48.30 wt%), hydrogen index (56–286 mg HC/g TOC), oxygen index (30–121 mg CO 2 /g TOC) and S 2 /S 3 (0.47–9.59) values. Dominant maceral assemblages included huminites and low amounts of liptinite group macerals. Tissue preservation index (0.39–5.13), gelification index (4.11–96.83), groundwater index (0.40–8.77) and vegetation index (0.49–42.67) parameters indicate a limno-telmatic environment and increased woody tissue. Mean random huminite/vitrinite reflectance values (ranging from 0.23 to 0.41 %Ro) denote lignite and sub-bituminous C and B ranked coals. Carpinus , Alnus , Zelkova , Platanus-Salix , Carya , and Ostrya were found through palynologic investigations. In addition, freshwater algae B otryococcus was detected in coal samples from Denizli. δ¹³C, δ¹⁵N values and C/N ratios indicated a terrestrial C3 ecosystem. Some sterane and tricyclic terpane ratios and aromatic biomarkers have shown that high plant input, immature organic matter and oxic-suboxic conditions are predominant in the depositional environment. [ABSTRACT FROM AUTHOR]