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The Pittsburgh No. 8 coal, the basal member of the Monongahela Formation, is considered one of the most important coal seams in Ohio. Maceral analyses and reflectance studies were conducted on four seams to determine its depositional environment. Petrographic analyses of coal from Guernsey, Belmont,
and Jefferson Counties, Ohio, show large amounts of vitrinite, varying amounts of exinites, and inertinites. The inertinites, consisting mainly of fusinites and semifusinites are normally present in larger amounts than the sporinites and resinites that make up the exinites. Large amounts of mineral matter, composed of pyrite, carbopyrite, and carbargillite, exist within this high sulfur coal. Vitrinite reflectance studies reveal that all seams rank as high volatile bituminous coal.
Macerals within the coal imply that at the time of deposition the predominant facies was forest moor, occasionally interrupted by the mixed forest-and-reed and reed moor facies. The coal seams were in an upper delta-plain fluvial environment on an easterly building deltaic lobe.
The two westerly seams are thinner, with a higher ash content indicating their proximity to the main delta. They were deposited under brackish water conditions due to the distributary's diluting of the marine sea. The southern and northernmost seams have higher pyritic values reflecting deposition under marine conditions. The southernmost seam's higher pyritic values at its extremes indicate inundations of the sea in that area of the deltaic lobe.
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