Occurence of Long-chain n-Alkanes in MuaraWahau Coal, Upper Kutai Basin, Indonesia

MuaraWahau coal belongs to Wahau Formation which was deposited during Early Miocene in terrestrial environments. Organic geochemistry study has been performed to characterize the biomarker composition of the coal. Saturated hydrocarbon fraction comprises n-alkanes with carbon numbers from 14 to 40. Bimodal distribution peaking at n-C16 and n-C31 are detected. Additionally, unusual peak is also remarkable at n-C38. The long chain n- alkanes peaking at n-C31 might be derived from higher plants. The origin of short chain n-alkanes (n-C14 to n-C21) are less specific, probably originate from higher plants and/or algae. Other related identified biomarkers which confirm the significant contribution of higher plants are olean-13(18)-ene, olean-18-ene and urs-12-ene. The presence of longer-chain n-alkanes especially unusual high amount of n-C38 is interesting to be noted as this compound has been reported only from some Kalimantan coals. Considering the abundance of higher plants biomarkers in MuaraWahau coal, it is hypothesized that the C38 n-alkane was likely derived also from higher plants.