GREB, STEPHEN F., and DONALD R. CHESNUT, JR., Kentucky
Kentucky Geological Survey, Lexington, KY

Sedimentology of Pennsylvanian Sandstone from Bedding-Plane
Exposures, Laurel Dam Spillway, Eastern Kentucky Coalfield

	Exposures of bedding planes in a coarsening-upward sequence of the
Breathitt Formation at the Laurel Dam spillway in Whitley County,
Kentucky, were analyzed by surveying a 250,000-ft² area on a 10-ft grid
and mapping within grids.
	Detailed mapping of sedimentary structures revealed several internal
facies within the coarsening-upward sandstone unit. The lower facies is
fine grained, thin bedded, and dominated by asymmetric current rip-
ples except for a narrow area of large-scale trough stratification. The
troughs have asymmetrical limbs with ripple fans commonly developed
on the shallow dipping limbs. The lower sandstone is truncated by a
series of small channel facies that contain a siderite-pebble lag and mas-
sive sandstone grading upward into current-ripple-bedded sandstones
that exhibit parting lineations and flat-topped ripples interpreted to
represent sheared ripples during upper-regime flow. The upper sand-
stone facies is a large channel that truncates underlying facies. Channel
fill consists of plant-debris lags and abundant planar cross-beds depos-
ited by paleocurrents to the west.
	These types of exposures provide a detailed three-dimensional look
at a typical Pennsylvanian bay-fill deposit as well as an exceptional view
of the microforms and mesoforms within that environment.