Print this pageNew roadcuts on U.S. Highway 23 through Pound Gap on Pine Mountain in eastern Kentucky have exposed a nearly complete, 600-m-thick (2000-ft-thick) section of Upper Devonian through Lower Pennsylvanian strata. The section occurs on the leading edge of the Pine Mountain thrust fault, and strata are exposed in mostly undeformed, moderately dipping beds. Several sequences and associated boundaries are exposed in the outcrops, which is important because equivalent beds occur at depths of more than 600 in (2,000 ft) in front of the thrust. Because of its significance, the Pound Gap roadcut was designated as the first official Distinguished Geologic Site in Kentucky by the Kentucky Society of Professional Geologists.
The base of the section occurs in the Huron Member of the Ohio Shale, and more than 81 in (270 ft) of the Upper Devonian is exposed. Mississippian strata consist of 33 in (110 ft) of the Sunbury Shale, overlain by 90 in (300 ft) of turbidite-dominated siliciclastics of the Grainger Formation, overlain by 167 in (556 ft) of shallow-water ramp carbonates and shales of the Newman Limestone and 279 in (930 ft) of mixed carbonates, tidally influenced clastics, red and green paleosols, and other clastics of the Pennington Formation. The Pennington is disconformably overlain by more than 30 in (100 ft) of Lower Pennsylvanian, fluvial, cross-bedded, quartz-pebble conglomerates assigned to the undifferentiated Warren Point-Sewannee sandstones.
AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana