Organic petrological characteristics of Iimnic and paralic coals of Sarawak

An organic petrological study was performed on Tertiary coals from the Merit-Pila and the Mukah-Balingian coalfields of Sarawak. The main objective of this study was to determine the petrological characteristics of these coals in relation to their environment of deposition. The coals analysed were deposited in two distinct depositional settings. The Mukah-Balingian coals were deposited under paralic conditions of a lower coastal plain setting whilst the MeritPila coals were deposited inland under limnic condition of a lacustrine setting. Differentiation of these depositional settings are based on the presence of diagnostic macerals, such as alginite, and on cross plots of gelification index (Gl) versus tissue preservation index (TP1). While both sets of coals possess TPI values < 1, the paralic origin coals generally possess GI values> 10 whilst limnic coals possess Ol values < 10. Abstrak: Suatu kajian petrologi organik dilakukan ke atas arang batu Tertiar dari Merit-Pila dan Mukah-Balingian, Sarawak. Objektif utarna kajian ini ialah untuk menentukan ciri-ciri petrologi arang batu ini yang berkaitan dengan . persekitaran pengenapan mereka. Arang batu yang dikaji telah dienapkan di dalam dua persekitaran pengenapan yang berbeza. Arang batu Mukah-Balingian dienapkan di bawah keadaan paralik di kawasan dataran pantai bawah sementara arang batu Merit-Pila dienapkan di kawasan daratan pendalaman di bawah keadaan limnik persekitaran lakustrin. Perbedaan di antara persekitaran pengenapan ini adalah berdasarkan kepada kehadiran maseral-maseral diagnostik seperti alginit, dan berdasarkan plot indeks gelifikasi (Ol) lawan indeks pengawetan tisu (TPI). Sementara kedua-dua set arang batu ini mempunyai nilai TPl < 1, arang batu asalan paralik biasanya mempunyai nilai Gl > 10 semen tara arang batu limnik mempunyai nilai Ol < 10.