Paleoenvironmental Interpretation based on Lithotype and Macerals Variation from Ritan's Lignite, Upper Kutai Basin, East Kalimantan☆

Abstract The present study describes vertical variations in lithotypeand petrographic composition of a Miocene lignite bearing succescion from the Upper Kutai Basin, East Kalimantan. Twenty four lignite samples from two drill holes at Ritan area were callected. Ritan's lignite have been analyzed Based on the lithotype analysis, the Ritan's lignite show variations in the predominance of some macerals that macroscopically and microscopically to asses the characteristics and depositional environment of the lignite present. indicating succesion of inveronmental changes. Macroscopically the dominanlithotype are banded dull, followed by dull, and parting impregnated within the lignite seam. Microscopically the dominant maceral group are huminite present in moderate to high value (27,9-78,7%) while the minor one is inertinite group showing a low value (6,5 12,2%), followed by low to moderate value of liptinite (19,9 31,5%). Reflectance measured on the maceralhuminite range from 0,235 to 0,354% placing the Ritan coals into a transition stage from peat to lignite. Examiniation of lihotype variation and the distribution macerals constituent suggest a Miocene lignite as marsh to upper delta plain depositional setting.