The humic macerals in the samples are dominated by low-reflectance humic materials. In terms of the definitions of ICCP (1971), the low reflectance forms should be referred to huminite. However, this material becomes vitrinite at higher levels of rank, and the use of huminite is considered by many authors to be confusing. Using ICCP terminology, essentially the same component changes from the huminite group to the vitrinite group at a reflectance of 0.5%. The Australian Standard has combined the two materials within the vitrinite group, and this terminology is the basis of the classification used here (see Table T1).
In the Australian Standard (SAA), the textural differences that are a function of rank (that is, textures can be different for the lower and higher rank forms of vitrinite) are identified and separated at the maceral level. The classifications are identical at group and subgroup levels.
The dominant forms of organic matter present in this sample suite belong to the telovitrinite subgroup. Within this group, textinite, texto-ulminite, and ulminite are all present, and some material is best considered as telocollinite, a term normally restricted to some forms of vitrinite present in higher-rank coals. Discussions of the compaction of structures within vitrinite are given in Taylor et al. (1998) and Teichmüller and Teichmüller (1950).
The Australian Standard builds on the ICCP (1971) classification for low-rank coals. At a general level, this classification proved adequate. However, at a more detailed level it has proved inadequate in relation to woody tissues that show low reflectance and moderate to strong fluorescence, largely from the primary cell walls. In the ICCP (1971) classification, primary fluorescence is considered as coming only from suberinite, the primary cell wall material associated with bark tissues.
However, in the present study, many examples were found of xylem tissues with primary cell walls showing fluorescence as strong or stronger than suberinite in the same sample. These tissue types are illustrated in Plate P3, figure 3 and figure 4, and Plate P4, figure 1, figure 2, figure 3, and figure 4. Generally, the fluorescing cell walls have not been counted as liptinite, even though in terms of optical properties, they resemble that maceral group much more closely than vitrinite.