Open File Report 1990-02

Open File Report 1990-02

OFR 1990-02

Alberta Geological Survey - Coal Geology: Coal Compilation Project - Entrance NTS 83F/5

The objective of the pilot Coal Compilation Project was to provide coal resource maps, at a 1:50,000 scale, to stimulate and support industry exploration programs and assist government in matters of resource management. This report covers the study area of NTS 83F/5 (Entrance) in west-central Alberta.

Within this area, coal measures are deposited within thick successions of sandstones, siltstones, shales and conglomerates. These coal-bearing sequences are part of the Lower Cretaceous Luscar Group, Upper Cretaceous Brazeau Formation and Paleocene Coalspur Formations. The area contains coal resources and reserves in the following EUB-designated coal fields: Brule, Coalspur, Jarvis Lake and McLeod River, and a 'small isolated deposit' in Maxwell Lake.

The Luscar Group coal seams are exposed in a series of northwest-trending thrust sheets and associated folds. Often the coal seams have been further locally folded and faulted. Depending on the severity of these local structural complexities, and acknowledging a general discontinuity of coal outcrops in the Inner Foothills, coal-seam correlations and evaluations can be extremely difficult.

The Brazeau Formation is overlain by the Entrance Conglomerate (or an equivalent sandstone). In the upper 200 m of the Brazeau Formation, coal seams have been identified. North of the Athabasca River, one 0.6 m Brazeau seam has been located in outcrop. Three thin Brazeau coal seams have also been identified in a coal drillhole, north of the Athabasca River. Two of the seams are 0.7 m thick each, whereas the third is 0.75 m thick.

The Coalspur Formation consists of nonmarine sandstones, siltstones, shales and coals and overlies the Entrance Conglomerate. Within the project area, north of the Athabasca River, as many as 10 coal seams have been identified within the Coalspur Formation. The seams have an average aggregate thickness of 19.5 m and are contained within a 300 m thick sedimentary sequence.

Additional subsurface geological studies, including the correlation of regional cross-sections and seam correlations, are needed both along the strike of the Coal Valley Coal Zone and along the Entrance Syncline. Structural studies in the Brule Lake Coal Field and along the Luscar trend north and south of the Brule Field could be rewarding.

Richardson, R.J.H., Langenberg, C.W., Chao, D.K. and Fietz, D.W. (1990): Alberta Geological Survey - Coal geology: Coal compilation project - Entrance NTS 83F/5; Alberta Research Council, ARC/AGS Open File Report 1990-02, 68 p.