1.2.1.1.2 Newcastle Coalfield

Greta Coal Measures

The Homeville Coal Member of the Greta Coal Measures is up to 6 m thick and generally thicker east of Cessnock. The overlying Greta seam (informal unit) is up to 11 m thick in the vicinity of Cessnock but thins over a relatively short distance towards the south. The upper portion of the seam is of lower quality and is high in sulfur (Agnew et al., 1995, p. 209). At the Austar Coal Mine the Greta seam is described as a 7 m thick, semi-hard coking coal and thermal coal (Yancoal, 2015a), with low ash and medium moisture contents (Idemitsu Kosan, 2010, p. 2). Agnew et al. (1995, p. 209) recorded moisture contents of 1.7 and 2.1%, ash yields of 5.9 and 6.3%, and volatile matter contents of 42.6 and 42% for the Homeville Coal Member and the Greta seam, respectively. These coals are generally vitrinite-rich, with mean vitrinite content about 67% for the two main seams (Agnew et al., 1995, p. 210).

Tomago Coal Measures

Coal seams of the Tomago Coal Measures are generally split and vary in lateral extent, mainly due to their depositional environments. The coals are generally vitrinite-rich, with contents greater than 72% (Agnew et al., 1995, p. 210). Of the main coal units in the sequence the Rathluba Formation varies between 1.5 and 3 m in thickness, the Big Ben Coal Member is 1.5 to 4.5 m thick, and the (informally named) Donaldson seam between 1 and 3 m thick. The Rathluba Formation contains a number of stone bands and coal quality is variable. The Big Ben Coal Member contains mudstone interbeds and thickens towards the west of the coalfield, and the Donaldson seam commonly has a number of splits enclosed within a 30 m thick section (Agnew et al., 1995, p. 209). Agnew et al. (1995, p. 210) recorded moisture contents between 2.1 and 2.5%, ash yields between 10.6 and 12.8%, and volatile matter contents between 34.9 and 37% for these seams. Compared to the coals of the Newcastle Coal Measures the Tomago Coal Measures have relatively high sulfur contents.

Newcastle Coal Measures

The lowest seam in the Newcastle Coal Measures, the informally named Borehole coal seam, occurs throughout the coalfield. In the east it varies between 1.5 and 2.5 m thick, and thickens to 2.5 m towards the north-west of the coalfield. The coals immediately overlying the Borehole coal seam (the Yard, Dudley and Nobbys coal seams) are relatively thin and have limited resources (Agnew et al., 1995, p. 209). The Victoria Tunnel coal seam is best developed along the coast, east of Lake Macquarie. The next seam of economic interest, the Australian seam (an informally named, local seam), is generally 2.5 m in its basal section, but can be as thick as 16 m in places.

Of the upper seams of the Newcastle Coal Measures, the Fassifern, Great Northern and Wallarah coal seams are the most notable, with thicknesses varying between 2.5 and 3 m although some seams such as the Fassifern seam are up to 8 m and the Great Northern seam up to 7 m (Agnew et al., 1995, p. 209). At the Tasman Coal Mine, for example, semi-soft coking and thermal coal is produced from the Fassifern coal seam where it is reported to be 2.2 to 2.5 m thick (Tyler and Sutherland, 2011). The Great Northern seam is approximately 120 m deep and the Wallarah seam about 80 m below surface at Myuna Colliery (AECOM, 2011, p. 37). The uppermost seam of the sequence, the Vales Point coal seam, consists of up to three splits (Agnew et al., 1995, p. 209).