THE MICROFACIES OF LOWER SUBAN COAL SEAM IN SOUTH SUMATRA BASIN, INDONESIA: IMPLICATION OF PALEOMIRE DYNAMICS

The studied coals taken from Lower Suban seam in the Tanjung Enim area, South Sumatra Basin, are of low rank and huminite dominates the maceral composition (34.7-85.9 vol.%). Less abundant are liptinite (11.6-50.8 vol.%) and inertinite (1.4-13.6 vol.%). Minerals are found only in small amounts (0.4-2.0 vol.%), mostly as iron sulfide. Based on maceral assemblages the coals can be grouped into 4 classes: (1) Humodetrinite-liptinite-rich coal represents the basal section of studied coal seams. This group might be derived from sapric or fine hemic peat often occurring at the base of modern tropical peats, (2) Humotelinite-rich coal and (3) humocollinite-rich coal both characterize the middle section of the seams. The precursors of these groups were hemic and fine hemic peats. (4) Humodetrinite-rich coal represents the top section of coal seams. This group is the counterparts of fibric peat at the top of the modern peats. The sequence of maceral assemblages thus represents the change of topogenous to ombrogenous paleopeat and a development of raised paleo-peat bog.