Abstract Middle Pennsylvanian coal-measure sequences of the eastern Kentucky coal field, central Appalachian basin, occur in ordered groupings of five to six fourth-order coal-clastic cycles, between third-order marine flooding surfaces. Lower Pennsylvanian coal measures also are present, but are laterally truncated by at least four, 60舑80-km (37舑50-mi)-wide belts of quartz-pebble-bearing quartzarenites that were deposited in a longitudinal drainage system. Successive quartzarenite belts are truncated updip by the next youngest belt. Each belt consists of at least a pair of vertically stacked, composite sandstones separated by a coal bed and estuarine or marine shale facies. Although less marine than their middle Pennsylvanian counterparts, the base of these lower Pennsylvanian midformation shales also represents marine flooding surfaces, or the updip equivalents of flooding surfaces. Therefore, lower Pennsylvanian third-order genetic sequences can be defined that include both marginward quartzarenites and basinward coal-measure facies. Changes in foreland-basin subsidence, sedimentation patterns, climate, and marine influences affected depositional sequences from the early to middle Penn-sylvanian. The westward shift of the longitudinal drainage belt was accompanied by a westward shift in basinward coal measures, resulting in increasingly more extensive coals with time. Increasing expanse and uniformity of coal measures was accompanied by decreasing foreland accommodation. In each third-order sequence, the greatest accommodation appears to occur in the regressive parts of the brackish to marine shales that bound each sequence. The greatest spatial changes in sequence thickness occur across the northern hinge line of the basin and along the basinward limit of successive quartzarenite belts. Foreland-basin subsidence influenced the stacking of successive lower Pennsylvanian quartzarenites, the westward overlap of successive quartzarenite belts, basinward increases in the number of coal beds, development of coal zones in third-order sequences, and basinward increases in the thickness of coal beds.

Abstract Stratigraphic analysis of the Lower and Middle Pennsylvanian rocks of part of the central Appalachian basin reveals two orders of cycles and one overall trend in the vertical sequence of coal-bearing rocks. The smallest order cycle, the coal-clastic cycle, begins at the top of a major-resource coal bed and is composed of a sequence of shale, siltstone, sandstone, seat rock, and overlying coal bed which, in turn, is overlain by the next coal-clastic sequence. The major marine-transgression cycle is composed of five to seven coal-clastic cycles and is distinguished by the occurrence of widespread, relatively thick (generally greater than 5 m) marine strata at its base. The Breathitt coarsening-upward trend describes the general upward coarsening of the Middle Pennsylvanian part of the Breathitt Group and includes at least five major marine-transgression cycles. Chronologic analysis, based on averaging relative age dates determined in previous investigations, provides a duration of 20 my for the deposition of Lower and Middle Pennsylvanian strata of the central Appalachian basin. The eight major marine-transgression cycles that occurred in this interval are calculated to represent an average of 2.5 my each. The average duration of the coal-clastic cycle, in contrast, is calculated to be only about 0.4 my. The average duration of coal-clastic cycles is of the same order of magnitude (10 5 yr) as the Milankovitch orbital-eccentricity cycles and matches the 0.4 my second-order eccentricity cycle (Long Earth-Eccentricity cycle). These orbital periodicities are known to modulate glacial stages and glacio-eustatic levels. The calculated periodicities of the coal-clastic cycles can be used to support glacio-eustatic control of the coal-bearing rocks of the Appalachian basin. The 2.5-my periodicity of the major marine-transgression cycle does not match any known orbital or tectonic cycle. The cause of this cycle is unknown, but might represent episodic thrusting in the orogen, propagation of intra-plate stresses, or an unidentified orbital cycle. The Breathitt coarsening-upward trend represents the increasing intensity and proximity of the Alleghanian orogeny.

Abstract The “Four Corners” exposure is located at the intersection of Kentucky 80, Kentucky 15, and the Daniel Boone Parkway about 2.7 mi (4.3 km) northward of Hazard in Perry County, Kentucky. The stop is located in Carter coordinate section 14-S-76, on the Hazard North 7½-minute Quadrangle (Fig. 1). The multilane highways offer easy accessibility by vehicle. Buses may park along the shoulder of the Daniel Boone Parkway or Kentucky 80. Multiple benches on these high roadcuts offer access to most of the strata by foot; however, much of the geology is visible from the road. Potential dangers such as traffic, extreme heights, rock falls, and unstable footing should be stressed. Be particularly aware of people below you. Do not enter adits or overhangs of adits.

Abstract A Pennsylvanian-age distributary-mouth bar in the Breathitt Formation can be seen at two localities in Knott County, Kentucky. The northwest locality is on Kentucky 80,500 ft (152 m) west of the intersection of Kentucky 80 and the Hindman access road (“Hindman Spur”) (Fig. 1). This stop is located in Carter coordinate section 16-K-79, in the northwestern comer of the Hindman 7½-minute Quadrangle. The multilane highway offers easy accessibility by vehicle, and buses may park along the shoulder of Kentucky 80, between the road cut and the intersection of the Hindman access road. The southeast locality is a road cut located on the Hindman access road about 0.5 mi (0.8 km) south of the intersection of Kentucky 80 and the access road. This stop is in the northwestern comer of the Hindman 7½-minute Quadrangle in Carter coordinate section 25-K-79. Buses may park in the large flat area on the southwestern side of the road just west of the road cut.