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. T
max 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.