Coals of the Belly River Group were studied over a one-year period as part of a joint Alberta Energy and Natural Resources/Alberta Research Council coal resource evaluation program. The objectives of this program were twofold: (a) to evaluate the coal resource potential south of township 64 and down to a depth of 400 m and (b) to develop geologic techniques to assess the distribution, thickness and continuity of coal seams. Data was gathered from oil and gas well logs and from shallow Alberta Research Council well logs. Data was stored and manipulated in a computer database and a suite of maps was generated outlining the coal potential of the three coal zones in the Belly River Group; i.e. Lethbridge, Taber and McKay. Each zone is treated separately and appendices are provided with complete descriptions of all maps and cross sections. Conventional stratigraphic and computer-based structural cross sections were also constructed to show the third dimensional aspect of the coal zones. Geological knowledge about the Belly River coals, before this study, was limited to southern Alberta. With the completion of the present study, a very large additional amount of information on the coals of this geological unit becomes available.
Coals within the Belly River Group have seam thicknesses most commonly in the 0.5 to 1.5 m range but seams around 3.0 m thick are present. The thickest seam encountered (4.9 m) was from an Alberta Research Council well through the Lethbridge coal zone, in the Brooks area. The thickest accumulations of coal within the Taber and McKay zones are found along northwest to southeast trending belts, with thickest individual seams, largest number of seams, and best seam correlation potential also occurring within these belts. Regional coal distribution patterns within the Lethbridge zone are less clear, but seem to show an increase in amount, thickness, and numbers of seams in a north to south direction. Coal development in the Lethbridge coal zone reaches a maximum in south central Alberta, and then diminishes southward to zero.
Belly River Group coals are thought to have formed from peat swamps in coastal plain environments some distance landward ( westward) of paleoshorelines. The positioning of these shorelines was critical in determining where, and to what extent, these peat swamps would develop, and thus thick coal seams would form.