Open File Report 1990-03

Open File Report 1990-03

OFR 1990-03

Coal Compilation Project - Moberly creek: NTS 83E/9

The study area of mapsheet NTS 83E/9 (Moberly Creek) is located in west-central Alberta. The communities of Hinton (83F/5) and Grande Cache (83E/14) are the primary population centers near the study area. Much of the Regional mapsheet 83E/9 is located within the proposed Yellowhead North IRP. Willmore Wilderness Provincial Park, in part, located in the southwest half of the mapsheet, is located outside of the Yellowhead North IRP.

Within the mapsheet 83E/9, coal measures are deposited amid 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 Luscar Group consists of sandstones, shales, conglomerates and coals, deposited predominantly in nonmarine environments. Strata of the Lower Cretaceous Luscar Group have been subjected to deformation which has produced northwesterly trending thrust faults and folds. As a result, the Luscar Group coal seams are now 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. Several seams have been identified within the mapsheet. No correlations could be established for the Luscar Group coal seams. Individual seam thicknesses vary to a maximum of 10 meters.

The Upper Cretaceous Brazeau Formation and the Paleocene Coalspur Formation are located in a gentle monocline that trends in a northwesterly strike direction. Strata dip to the northeast, generally between 5 and 20 degrees. No other major structures were noted from the available outcrop or drillhole data.

The Brazeau Formation consists of nonmarine sandstones, conglomerates, shales and coals and lies conformably above the marine Wapiabi Formation. The Brazeau Formation is overlain by the Entrance Conglomerate (or an equivalent sandstone). In the upper 200 meters of the Brazeau Formation, coal seams have been identified. On the mapsheet, at least two Brazeau coal seams have been intersected in a limited number of drillholes.

The Coalspur Formation consists of nonmarine sandstones, siltstones, shales and coals and overlies the Entrance Conglomerate (or an equivalent sandstone). Within the mapsheet, as many as 12 coal seams have been identified within the Coalspur Formation. The seams have an average aggregate thickness of 17.5 meters and are contained within a 250+ meter-thick sedimentary sequence. It should be noted that some of the 'traditional' Coalspur coal zones (i.e., Silkstone and Mynheer) have not been recognized within the mapsheet area. It is believed there is a stratigraphic interval of 400-450 meters from Seam 1 to the underlying Entrance Conglomerate.

A promising area for future work is the coal zone trend to the north of the Jarvis Lake Coal Field. Additional subsurface geological studies, including the construction of regional cross- sections and seam correlations, are needed in the eastern and northeastern regions of the map area. Structural geology studies are critical for an evaluation of the central and western areas.