Kutai Basin is Tertiary basin which is the largest coal producers in Indonesia. Basic sedimentology knowledge, regional geology controlled and modern environment analogue are needed to support coal exploration activity specially coal seams correlation framework in the fluvial – deltaic environment in Lower Kutai Basin.
The methods of this research are spot mapping in several coal outcrops in Samarinda – Tenggarong areas (Lower Kutai), comprehensive stratigraphic measurement in the Muara Teweh – Kutai Barat areas (Upper Kutai Basin) and modern Mahakam Delta sedimentology observation in the Samarinda area as modern analogue reference for fluvial – deltaic depositional environment.
There are several coal bearing formations which is famous in the Kutai Basin, start from the oldest is Middle – Late Eocene coal (equivalent to Tanjung Formation), Late Oligocene – Early Miocene coal (equivalent to Pamaluan Formation), Middle Miocene coal (equivalent to Balikpapan Formation). Middle to Late Miocene coal formation is the most productive formation which is exploited in Kutai Basin.
Middle to late Eocene deltaic coal characters are black, platy and blocky cleavage, vitreous luster, vitrain to clarain lithotype, thickness 20 to 30 cm. Late Oligocene – Early Miocene delta plain coal is characterized by black, blocky cleavage, hard to medium hard, thickness 30 to 70 cm. Middle to Late Miocene delta front coal is characterized by oyster bed coal, high gamma ray. Middle to Late Miocene fluvial coal character is coal sandwiching sandstone.
Modern Mahakam delta observation are showing several depositional environment which has potential become coal bearing environment. The first is fluvial flood plain environment, upper delta plain, lower delta plain, tidal distributary bar, delta front mouth bar and back spit / back lagoon.
Authors : P. T. Setyobudi, P. A.Suandhi, A. Bachtiar, A. Miri