Pliocene age lignites from Lower Sajau
seam, from borehole in Berau Basin, Northeast Kalimantan, Indonesia were
investigated with respect to organic geochemistry by HPLC, GC and GC/MS. The
analysis was conducted to drilling sequence of Kasai Coal Field, Berau Basin
which has been applied to identify organic sources and maturity of organic
matter. The result of normalized yields of the soluble organic matter (SOM)
data indicates saturated and aromatic proportion of hydrocarbon are very low
(under 10%), this was reflecting that lignite coal is still in immature stage.
Moreover, biomarker hydrocarbon such as diterpenoids was not found from the
sample that indicates absence of gymnosperm precursor in the paleo-peat. In
contrast, there was great abundance of terpenoid biomarkers including lupane
and oleanane showing domination of angiosperms indicate that angiosperm was
dominated vegetation source. There also hopanoid biomarkers explaining acidic
depositional environment in coal formation and microbes-affected conditions in
peat formation process. Ratio of Tm/Ts shows paleomire where ratios value of
Tm/Ts is in range of oxide condition.