“…Further east they give way to the high-volatile to sub-bituminous coals of the Foothills and Plains until the lignites of southern Saskatchewan are reached. This broad correlation between geological age, depth of burial, residence time and coal rank (Norris 1971;Hacquebard and Donaldson 1974), which indicates pre-tectonic coalification (Kalkreuth and McMechan 1984;Kalkreuth and Langenberg 1986;Smith 1989), applies mainly to the less deformed portions of the Foothills and the Interior Plains. In the Front Ranges, were tectonic deformation is more severe, the simple age/rank relationship has been modified locally by late thrusting.…”