Description : Eight regional Lower to Middle Pennsylvanian coal beds (Namurian B/C to Westphalian C) in southern West Virginia were examined. Beds were divided into their component sedimentary parts or benches by identifying bounding surfaces and associated siliciclastic partings within beds. Bounding surfaces represent the cessation of peat accumulation. Paleo-peat mire morphology at the bench level was determined using shape analysis, petrographic indices and coal chemistry data. Planar and raised paleo-peat mire benches were identified. All gas coal and some splint coal benches were derived from raised mires. Heterolithic coal and the remaining splint coal benches were derived from planar mires. Most bounding surfaces are thin, composed of oxidized and degraded organic materials, high in ash and sulfur content, and contain clay minerals and silt-sized quartz. Vitrinite reflectance is suppressed in the upper part of some benches. The associated siliciclastic parting materials, when thick, show evidence of tidal influence and contain brackish water to marine trace fossil assemblages. Bounding surfaces and the associated sediments represent a sudden increase in water depth and the lateral continuity of these surfaces indicates regional to basinal extent. Bounding surfaces are the up-paleoslope expression of rapid ( < 1-ka duration) marine flooding events. A repeating sequence was identified within six of the eight thick, regional coal beds examined. It consists in its simplest expression of (1) planar mire formation, initially occurring on interfluvial sequence boundaries, (2) probable evolution of the planar mire into a raised mire, (3) marine flooding event and bounding surface formation, (4) planar mire reestablishment, and (5) bed termination. The hiatus between the interfluvial sequence boundary and overlying coal bed, based on comparisons with modern analogues, may represent more than 100 ka of missing time. Peat accumulation and basin subsidence estimates suggest that an additional 100 ka or more may have been involved in the formation of a single coal bed sequence. The geographic extent of these sequences and the fact that they repeat indicates that an allocyclic mechanism (climate and/or glacioeustacy) was responsible for their development.
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