The coal measures of the North Block Complex occur on the eastern edge of the Witbank coalfield, within the Permian-age Vryheid formation of the Ecca Group in the Karoo Sequence. The Witbank coalfield is situated in the northern part of the Main Karoo basin and extends about 190km west-east between Brakpan and Belfast and about 60km north-south between Middelburg and Ermelo.

The main Karoo Basin:
- Was filled between the Late Carboniferous and Middle Jurassic periods;
- It is lithostratigraphically subdivided into the Dwyka, Ecca and Beaufort Groups, succeeded by the Molteno, Elliot and Clarens Formations and the Drakensburg Formation (volcanics);
- The coal bearing Ecca Group has been divided into three sub-units: the Pietermaritzburg; Vryheid and Volksrust Formations.

The Witbank Coalfield:
- The coal-bearing Vryheid Formation attains a thickness of 70m to 200m in the Witbank Coalfield;
- Here the Vryheid Formation consists of five coarsening-upward sequences with coal seams associated predominantly with the coarser grained fluvial facies at the top of each sequence;
- The No. 5, 4, 2 and 1 coal seams are of economic interest.

NBC (Glisa) mine resource area is close to the eastern edge of the Witbank Coalfield, in the northern part of the main Karoo basin. All Witbank Coalfield seams, i.e. S1, S2, S3, S4 and S5, occur in the Glisa area, with S2, S3 and S4 being economically important. Stratigraphy consists pred ........

The primary operation is the Glisa mine, a multi seam open-cast mining operation 5km west of Belfast in the Highveld region of Mpumalanga.

The Eerstelingsfontein block to the south-east of Glisa comprises gently sloping topography. The coal resource here is contained in a single seam, S2. This seam occurs as an erosional remnant on high ground at shallow depths, suitable for open-cast mining.

The Paardeplaats Section is an operational section that adjoins the Glisa Section. Mining is undertaken by opencast mining methods.

As RoM reduces at the Glisa Section, the shortfall will be addressed through coal mined at the Paardeplaats Section. The Paardeplaats Section is an open cast mining operation where bench mining techniques are employed to access the coal seams. The 2 Seam Burden is removed with Dozers doing roll-over of the 2 seam burden into the previous 2 seam voids, and the upper burden seams are removed with the truck and shovel mining method. Coal seams 4, 3 and 2 will be mined for processing. Seam 1 appears in certain areas only and is highly weathered and contaminated with inseam shales and is not suitable to mine and will be left in situ in the pit.

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