f Coal Depositional Settings of Mukah-Balingian, Sarawak: Implications for Coaly Petroleum Source Rocks of the Balingian Province

The coals and coaly sediments analysed in this study are from the Neogene (Miocene-Pliocene~ coal-bearing sequences of the Begrih-Liang and Balingian formations which outcrop within the onshore part of the Balingian Province. Most of the samples analysed are from the Sulau Coal Quarry and outcrops along the Mukah-Selangau Road. Using a combination of lithofacies studies, organic petrological analyses, and organic geochemical characteristics of these coal-bearing sediments, the environment of deposition for both the Balingian Formation and the Begrih-Liang Formation appears to have been within fluvial-deltaic. However, there seems to have been greater marine influence in the Begrih-Liang Formation compared to the Balingian Formation. Although most of the coals studied are of an autochthonous origin (formed beneath the plant cover from which they were derived), some are hypautochthonous deposits (originated from material that was transported from its immediate source but accumulated within the same sedimentary environment). The autochthonous coal deposits are relatively thicker and commonly associated with rootlets within the underlying clay while the hypautochthonous coal deposits are relatively thin and associated with significant amounts of clay minerals.