Organic geochemical and isotopic (C and N) characterization of carbonaceous rocks of the Denizli Area, Western Turkey

The sediments under examination constitute part of the Hayrettin Formation expanding to the northwest of Acıgöl (Denizli/Turkey) containing coal. The aims of this study are to assess the organic matter content (Corg, %), type, maturity and established paleoenvironment of deposition based primarily on Rock-Eval pyrolysis data, biomarker distributions and δ13C, δ15N values. The total organic carbon (Corg, %) contents of carbonaceous rocks range from 0.21% to 39.61%, and hydrogen index (HI) values are between 25 and 174 mg HC/g rock. The samples studied contain type III organic matter (OM). Tmax values for the Hayrettin carbonaceous rocks range from 400 to 437 °C. Vitrinite reflectance values (Ro) are between 0.26% and 0.36%, and these values reveal that the carbonaceous rocks are at peat-lignite coal stage. On the basis of biomarker maturity parameters, these rocks are immature. The high pristane/phytane (Pr/Ph) ratios (0.79–7.85), low C35 homohopane index (0.02–0.07) indicates that carbonaceous rocks were deposited in a suboxic environment. δ13C (range from −26.06‰ to −23.88‰) and δ15N (range from 2.63‰ to 3.33‰) values, high concentrations of C29 steranes (C29>C28>C27) and C26/C25 tricyclic terpane ratios (1.00 and 1.18) indicate that these carbonaceous rocks formed in a peat-swamp environment.