Coal-bearing depositional environment impact to sulphur and ash content in coal of Batu Ayau formation, Murung Raya, Central Kalimantan

Coal formation is controlled by several factors that also relate to the coal-bearing formation, which affects the coal chemical components. The coal of Batu Ayau Formation is one of the most targeted coking coal in Murung Raya, Central Kalimantan. Thus, a thorough study of the chemical components is highly required. This study aims to interpret the depositional environment of the Batu Ayau Formation as the coal-bearing formation and determine its impact on the sulphur and ash content of the coal. The method applied to this study is the measuring stratigraphy, utilised in interpreting the coal-bearing depositional environment, which later is elaborated with the proximate analysis result from 9 seams. The lithofacies identified from measured stratigraphy are claystone, sandstone, and coal. The facies association of interdistributary bay, crevasse splay, and channel lead to the interpretation of transitional lower delta plain depositional environment. The low composition of sulphur (0.35-0.55wt %) and low ash content (4.4-4.9wt %) are yielded from the coals of the upper part of the measured section. The coal from the lower section constitutes higher sulphur (1.2-2.41wt %) and high ash content (5.1-9.8wt %), which is caused by the relatively deeper environment frequently influenced by seawater.