Biomarker characteristics of pliocene coals, Ilgin (Konya)

In this study, organic geochemical and petrographic properties of the coal-bearing strata of the Pliocene Dursunlu Formation (Ilgın-Konya) were investigated. The Pliocene units consist of a package of conglomerate, sandstone, mudstone, clay, claystone, coal and marl in the study area. The TOC amount of coal of the Pliocene Dursunlu Formation was determined as 40.11-49.62 wt. % (average 45.21 wt.%), immature level (Tmax, average 416 0C), and kerogen type Type III kerogen. The samples evaluated show the characteristics of potential source rocks. However, they were the immature stage for gas/oil production. Coalification and paleoenvironmental characteristics of the coal-bearing strata were examined using the values obtained from biomarker geochemistry data. The n-alkane and isoprenoid values, sterane, terpane, monoaromatic steroid, triaromatic steroid, phenanthrene and dibenzothiophene distributions obtained from the coal indicate that organic matter containing terrestrial and lacustrine algal showed deposited peatified in paleswamp and presented anoxic conditions. Coals examined has changed in the immature-early mature stage. According to the parameters obtained from the CPI-OEP indices, it was determined that the samples belonging to the study area were in the immature-early mature stage. In addition, the UCM determined in the gas chromatograms shows that the organic matter is immature and biodegraded. According to the petrographic analysis data carried on the samples belonging to the study area, the dominant maceral group consists of huminites (62-73%). There is also a small amount of liptinite (2-4%) and inertinite (8-14%) group macerals other than the huminite group. Also pyrite (3-5%) and clay-silicate (13-18%) the amounts were observed at high values in coal-bearing strata. The vitrinite/huminite reflection (Ro) measured on the coal samples are between 0.37-0.38% and indicating immature organic matter. According to the elemental analysis data of coal samples, carbon (C) varied from 52.01% to 56.70%, hydrogen (H) varied from 3.48% to 3.86%, oxygen (O) varied from 20.27% to 25.05%, nitrogen (N) varied from 0.84% to 1.43%, and sulfur (S) varied from 4.95% to 6.55%. In addition, using the elemental analysis data, atomic H/C (0.78-0.82) and O/C (0.26-0.33) values were calculated. By using a Van- Krevelen diagram, the organic matter type of the coal samples is type III kerogen and it has been determined the "lignite and sub-bituminous coal" stage.