PALEOFRACTURE AND STRUCTURAL INFLUENCES ON THE ACCUMULATION OF THE STOCKTON COAL (BOLSOVIAN), FOUR CORNERS FORMATION, EASTERN KENTUCKY COAL FIELD, U.S.A

The Lower Broas-Stockton coal is a heavily mined coal of the Central Appalachian Basin that shows several scales of structural influence in northeastern Kentucky. Coal thinning, splitting, and sandstone cutouts occur along an east-west trend consistent with, but west of, the Warfield Fault and Warfield Anticline. The Warfield structures delineate the southern boundary of a basement aulocogen called the Rome Trough. Westward thinning is coincident with the Floyd County Channel-Paint Creek Uplift, another basement feature. Several preferential, conjugate linear trends of coal thickness variability define a smaller-scale structural influence, interpreted as regional paleofractures. Detection of subtle trends of less than 50 cm of thickness variation requires closely-spaced, mine-scale data to confirm the linear relationships.

The Stockton coal is split adjacent to lateral sandstones interpreted as paleochannels. The split is transitional to a shale parting and a high-ash increment toward the middle of the seam. Compositional group analyses of 30 increment samples from four sites indicate that the coal is dominated by the Mixed Palynoflora (codominant tree ferns, small lycopods, and arborescent lycopods)-High Ash group, with lesser amounts of the Mixed Palynoflora-High Vitrinite and Mixed Palynoflora-Low Ash groups. Coal-bench architecture analyses indicate that most of the thickness variation in the coal occurs beneath the middle durain, as would occur if the peat was infilling an uneven topographic surface. Hence, the peat is interpreted as a topogenous to soligenous mire. In soligenous mires, water seeps from springs or slopes laterally into the peat. Rectangular thickness trends are inferred to represent fracture influences on the pre-peat paleotopography and groundwater movement into the paleomire when the peat was accumulating, such that some part of the paleomire was probably soligenous. Periodic drying caused by a seasonally wet paleoclimate formed numerous low-ash, low-vitrinite durain layers in the coal. If ombrogenous conditions developed at all, the domes were relatively short-lived, and not widespread in the study area.