GEOLOGY

The Adaro coal deposit is located on the northeastern border of the Barito Basin, a broad cratonic depression up to 250 kilometers wide, of Eocene to Pliocene age in the Tertiary period. The basin occupies much of the province of Central Kalimantan and the western part of South Kalimantan and is bordered to the west by the Sunda Shield and to the east by an upthrust belt of basement rocks which form the Meratus range.

The main coal bearing sequence in the Adaro area is the Warukin Formation which is divided into three sub units with the principal coal horizons occurring in the uppermost sub-unit.

Up to 13 seams can be recognised within a single deposit which are lenticular in development but which also vary in thickness due to converging and splitting. Individual seams may be up to 50m thick. Although the coals are characteristically low in ash there is regional and stratigraphic variation in rank and therefore in calorific value.

The coals with the higher CV (+ 5000 Kcal as received) occur in the Tutupan area with highest values occurring in the lower seams in the sequence. The coals in the Wara deposits to the west and south west have higher moisture (+35% adb) and consequently lower calorific values.

The Tutupan coal deposit stretches for a length of 20 kilometers along a ridge in the north eastern part of the Adaro area. No major faults are known to disrupt the coal. The deposit contains thirteen individual seams with the majority of the coal occurring in the T100, T200 and T300 seam groups. The thickest coal (50 meters) occurs in the T100 seam in the southern part of the deposit. The T200 seam is the principal seam in the north where it is also up to 50 meters thick.

The Wara 1 coal deposit is located 5 kilometers west of the Tutupan Central area. It is separated from the Tutupan deposit by the Dahai thrust. The deposit stretches in a north-easterly direction over a distance of 12 kilometers and dips to the southeast at 45°. The Wara 1 deposit is composed of three major seams which are characteristically low in ash (less than 3%) but with moisture contents of around 40%.

The North Paringin coal deposit lies to the southeast of Tutupan and around 1 kilometers north of the old Paringin Pit. The deposit forms an asymmetrical anticline of 4 kilometers strike length with the eastern limb dipping at 30° and the western limb at 60°. It is also a multi-seam deposit consisting of over 40 seams ranging in thickness from less than 5 meters to greater than 20 meters. The quality of North Paringin is similar to Tutupan with ash around 3% and CV gar of around 4800 kcal. The Paringin coal deposit extends south of the Balangan River.