1.2.1.1.2 Dewrang Group

Hughes (1995, p. 418) notes that the Weismantel Coal Member is the thickest uniform seam in the Gloucester Basin with a thickness of up to 15 m in the area of Wards River (see Figure 22, Section 1.1.3), and up to 22 m thick in the Stratford area (see Figure 22, Section 1.1.3) as noted by Resource Strategies (2001, p. 3–3). Its moderately high sulfur content (1.8%) is the result of being developed in a back barrier environment and overlain by marine sediments, and the seam generally thins towards the north on both the eastern and western margins of the basin. In the Rocky Hill Coal Project area (see Figure 9, Section 1.2.4) the seam consists of five main plies (AGE, 2013, p. 4-45). Although coal rank varies laterally and vertically across the basin, Hughes (1995, p. 425) notes a mean maximum reflectance of vitrinite (Rv,max) of 0.71% for the Weismantel Coal Member in the south. Roberts et al. (1991, p. 171) regard this bright coal to be of medium to high bituminous rank.

SRK Consulting (2010, p. 8) mentions that the coal in the Mammy Johnsons Formation (Figure 4) is thick and discontinuous and Roberts et al. (1991, p. 171-174) note that locally it can be up to 10 m thick interspersed with sandstone and claystone.