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Unexpected variations in sulfur were encountered during mining of the Glenalum Tunnel coal in Wyoming County, West Virginia, in the Central Appalachian Basin. A geological analysis was initiated to determine the cause of the sulfur variations and provide a predictive tool for anticipating high-sulfur anomalies during future mining operations. The coal seam is comprised of six benches including bright to dull clarain, bone coal, and carbonaceous shale. The lower three benches are consistently less than 1% in raw and 1.5 sp. gr. sulfur, with average values for each bench less than 0.73%. The average raw and 1.5 sp. gr. sulfur for each of the upper benches is greater than 1.23%, and ranges from 0.27 to 6.07%. The majority of the sulfur occurs as finely disseminated pyrite. Thirteen cores drilled in 2012 indicate that the coal is overlain by laterally and vertically variable lacustrine, deltaic and estuarine facies. This interval averages 6.7 m thick and is overlain by the Oceana Shale, a widespread marine unit. A sinuous, branching belt of high-sulfur coal approximately 305–610 m wide and 3.22 km long extends across the southern portion of the property. This belt correlates with cores where the lacustrine shale of the immediate roof is thin or absent and where the stratigraphic interval between the coal and the base of the Oceana Shale is comprised mostly of sandstone. Raw sulfur generally exceeds 1% and is more variable where the lacustrine roof shale is less than 52 cm thick and where roof sandstone occupies 78–100% of the interval. The 1.5 sp. gr. sulfur generally exceeds 1% where the lacustrine roof shale is less than 33.5 cm and where the roof sandstone occupies 80–100% of the interval. High-sulfur areas are attributable to 1) the local influence of brackish to marine waters from tidal or deltaic distributaries which eroded down to the peat, and/or 2) thinning or removal of impermeable, lacustrine roof shale by channel erosion and hydraulic connection of the Oceana Shale marine pore fluids to the peat via permeable channel-fill sands. [ABSTRACT FROM AUTHOR]