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The Upper Jurassic-Lower Cretaceous Mist Mountain Formation in the southeastern Canadian Cordillera is a nonmarine succession up to 670 m thick that includes as many as 15 major seams of high volatile bituminous to semi-anthracite coal. Coals at the base of the formation were deposited in coastal and delta plain environments, whereas those of the upper part are interpreted as upper delta plain and alluvial plain deposits. The coal seams are thicker, more abundant, and laterally less continuous in the upper part of the formation. The geometry of the coal seams is influenced by the presence of adjacent channels that have locally thinned or washed out some seams. The effect of differential compaction on coal seam geometry is variable; some seams thin over paleo-channels, whereas others are thicker and/or contain fewer partings. The ash content of most coals shows no predictable lateral or vertical variation that can be related to the overall sedimentology, nor is there a correlation between seam thickness and ash content. The sulfur content of all seams is low (<1 percent), suggesting the absence of marine influence during peat accumulation. There is a general increase in vitrinite and a decrease in inertinite and semi-fusinite from the base to the top of the formation, which may reflect a greater contribution of herbs to coals formed from coastal marsh-swamp complexes at the base.

Variations in roof conditions in underground mines are related to the structural fabric of the coal measures, which in turn reflects the kinematics and dynamics of tectonic deformation and roof rock lithology. In the Vicary Creek Mine, the roof rock comprises two lithofacies: a thin-bedded, very fine grained, carbonaceous sandstone lithofacies interpreted as distal crevasse splay deposits, and a thick-bedded sandstone lithofacies interpreted as proximal splay deposits. The thin-bedded lithofacies includes carbonaceous partings that were preferred horizons for intrastratal slip along which cohesion of the roof rock has been lost. The thick-bedded sandstone lithofacies is well jointed, leading to a blocky roof rock that localized intrastratal slip within the underlying coal seam. In the Balmer North and Five Panel Mines, the roof rock is composed of carbonaceous siltstone and very fine grained sandstone interpreted as crevasse splay and overbank deposits. During flexural-slip folding, slip was localized along carbonaceous partings that have destroyed the cohesion between successive beds in the roof rock. The intersections of slickensided bedding surfaces and major shear and extension fracture systems have resulted in unstable roof rock, particularly in rooms and roadways developed parallel to their intersection.

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