Strike’s Berau Thermal Coal Project is located in one of the most well endowed coal provinces of the world, East Kalimantan.
Regional Geology
The Berau Sub-Basin, separated from the Kutai Basin by The Mangkaliat Highlands, occupies the area along and around the Berau Rivers (Segah River and Kelai River), East Kalimantan. To the west, the basin is bounded by Kuching Highlands, underlain by Pre-Tertiary rocks.
The Berau Sub-Basin is a part of Tarakan Basin which developed along the eastern continental margin of Kalimantan during the tertiary period. There are four sub-basins within the Tarakan Basin; they are the Tidung Sub-Basin, Tarakan Sub-Basin, Berau Sub-Basin, and Muara Sub-Basin. The Berau Sub-Basin covers approximately 6,500 km2 (Figure 1) and is known to host several significant coal deposits as well as active coal mines.
Figure 1. The Tarakan Basin and sub basin divisions.
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Within the Berau Sub Basin, the basin’s coal deposits are generally confined to the Latih and Lebanan Formations. Both of these formations occur within a generally circular to elliptical shaped subsiding basin with the centre of the basin. The sides of the basin are gently tilted around the perimeter, with the general stratigraphy dipping towards the centre of the basin from the periphery. From this, the coal deposits in the area also dip towards the centre of the basin from the periphery.
Concession Geology – Nyapa Resource
The Nyapa resource is located in southern extremity of the Berau Sub-Basin. The Tertiary sedimentary units that occur within, or closely adjacent to the concession area are the Birang Formation (Tomb), Lebak Formation (Toml), and Latih Formation (Tml).
The Company’s identified coal resources occur in the Miocene aged Latih Formation. The deposit has multiple coal seams with up to nine seams (C1-C9) identified with multiple sub-seams and seam splits. The generalised stratigraphic sequence is shown in Figure 2. The main seam in Nyapa West and East is Seam C5 which averages 5.0 m in Nyapa West and 4.5m in Nyapa East, while other seams are typically in the range of 0.4 to 2.1 m wide.
Generally, the coal-bearing sequence in the Nyapa area dips to the northeast at approximately 15-20° however displays local variation, particularly close to minor structures known to occur in some areas of the deposit. In general the sedimentary units trend northwest- southeast, striking between 280-340° the coal seams of the Nyapa Coalfield are hosted within sandstone and mudstone lithologies.
The coal quality data indicates the coal is a sub-bituminous, medium calorific coal with low ash, low moisture and low overall sulphur. The thicker seams display better coal qualities than the thinner seams.
Figure 2. Interpreted stratigraphic column of the Nyapa area, showing the seam position and the interpreted depositional setting. 
