Main content area

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

Karadirek, Selin, Ozcelik, Orhan
Energy & fuels 2019 v.33 no.2 pp. 677-690
Neogene period, algae, basins, biomarkers, coal, drilling, immatures, total organic carbon, Turkey (country)
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.