Abstract: Mining Geology of the Hazard No. 8 Coal, Four Corners Formation, Middle Pennsylvanian, Eastern Kentucky Coal Field

GREB, STEPHEN F., and GERALD A. WEISENFLUH
Kentucky Geological Survey, University of Kentucky, Lexington, KY

The Hazard No. 8 bed is a bituminous coal of Middle Pennsylvanian (Atokan) age that is of mineable thickness over a large part of the Eastern Kentucky Coal Field. Geologic factors that affect mining of this bed are mostly related to variable roof conditions and coal quality. Specific roof lithotypes that affect mining include (1) carbonaceous shales with abundant plant debris, (2) thin coal beds and claystones in the immediate roof of the seam, (3) narrow cutouts and roof rolls, and (4) interlaminated lithologies with weak bedding-plane contacts. In a recent case study, quartz arenitic sandstones above the coal contained numerous deformational structures, including flow rolls and paleoslumps, that may also affect mining. In addition, a previously unrecognized monoclinal structure has been identified in the southeastern part of the coal field that is associated with changes in roof lithofacies and exhibits locally steep coal dip.

The roof rocks above the coal appear to have been deposited in channel, splay, and floodplain settings. Paleosols and peats draping irregular flood deposits led to the variable riders and claystones seen in the roof. Flow rolls and paleoslumps are abundant along channel trends and appear to be more common in the case study area than elsewhere, suggesting local influences, either excessive pore pressure in the orthoquartzites compared to the regionally more common lithic arenites, or syndepositional movement on the monocline. Recognizing common deformation along sandstone margins in the roof allows for possible adverse roof conditions to be recognized in advance of mining, even if specific paleoslumps cannot be identified.

AAPG Search and Discovery Article #90930©1998 AAPG Eastern Section, Columbus, Ohio