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Clastic sediments in the Pocahontas Formation of the east-central Appalachian basin in Virginia and West Virginia were deposited in a series of stacked delta lobes along the southeastern shoreline of a Carboniferous Appalachian seaway. These sediments prograded northwestward and were depositionally continuous with precursor Mississippian coal-bearing strata presently located primarily to the southeast in the faulted and folded belt of the Appalachians. During periodic stillstands in Early Pennsylvanian time, coastal currents and waves reworked and segregated sand along the delta front, forming a system of curvilinear barrier-bars. Behind these protective barriers, vegetation flourished in swamps on the abandoned delta lobes. An analysis of the relationship of coal occurrences to the geometries of sandstone units indicates that the origin of thick, low-sulfur coal in the Pocahontas Formation can be attributed to the initial and continuing accumulation of peat on the periodically inactive delta lobes. Conversely thin, impure, and discontinuous peat (coal) accumulated in the shale-dominated interlobe areas. An increase in the sulfur content of the coal to the northwest may have resulted from the proximity of marine conditions to the distal ends of the delta lobes. The genetic relation of coal distribution and sulfur content to the delta system provides a basis for designing exploration programs in coal-bearing strata of the Appalachian basin, particularly for predicting both the quantity and the quality of the coal.

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