Organic Geochemical Characteristics and Depositional Environment of the Soma-Eynez (Manisa) Coals, Western Anatolia, Turkey

Research paper by Selin Karadirek, Orhan Ozcelik

Indexed on: 09 Feb '19Published on: 28 Jan '19Published in: Energy & Fuels


The organic geochemical characteristics of Soma-Eynez coals located in the southwest section of the Soma Neogene Basin in Turkey were examined, and the depositional environment and maturity levels were evaluated. The analyzed samples were drilling samples taken from the Lower Coal Seam (KM2) to represent the basin. The coal’s total organic carbon (TOC) content is 28.45–73.38%, potential yield (PY) value is 22.43–168.29, and extractable organic matter (EOM) yield is 1204–29774 ppm, which are all indicators that the source rock has excellent hydrocarbon-production potential. Tmax values are between 389 and 430 °C, indicating an immature stage for hydrocarbon production. This is further supported by biomarker maturity parameters (a high odd-to-even predominance index (OEP), low 20S/(20S + 20R) sterane ratio, low ββ/(ββ + αα) sterane ratio, low 22S/(22S + 22R)(C32) homohopane ratio, and low C29Ts/C29Ts + C29H ratio). Unresolved complex mixtures (UCMs) observed in gas chromatograms point to immature–low mature nonbiodegraded organic matter. The saturated biomarker fractions of KM2 coals are characterized by a high Tm/Ts (C27 17α-trisnorhopane/C27 18α-trisnorhopane) ratio, high Pr/Ph ratio, dominant C29 regular sterane presence, and high C30*/C29Ts ratio. All biomarker parameters showed that terrestrial higher plant materials and algal/bacterial source organisms collectively deposited in the paleo-swamp and under suboxic–oxic conditions.