Cannelton Shale--Unique Stratigraphic Marker Bed for Lower Part of Middle Pennsylvanian in Central Appalachian Basin
Charles L. Rice, James C. Currens, James A. Henderson, Jr.
The Cannelton shale in the Breathitt Formation and equivalent formations can be identified in gamma-ray logs of oil and gas test wells in much of the Central Appalachian basin. This generally overlooked unit lies above the Clintwood coal bed and below the highly productive Elkhorn coal zone (or their equivalents), midway in the 400-1,500-ft thick interval between the top of the Lower Pennsylvanian Lee Formation and the base of the Middle Pennsylvanian Kendrick Shale Member of the Breathitt Formation. The Cannelton is a sparsely fossiliferous, upward-coarsening, marine bay-fill sequence of shale and siltstone as much as 110 ft thick containing a dark 3-ft thick shale near its base. The relatively high radioactivity of the basal shale deflects the gamma-ray curve as much as 100 API units above the gray-shale base line. Although not commonly tested for oil and gas, the Pennsylvanian section increasingly is being logged by gamma-ray methods that show the Cannelton and its radioactive bed are most conspicuous in the deeper and poorly known parts of the section within and northwest of the Cumberland overthrust sheet in Tennessee, Virginia, and Kentucky. The Pennsylvanian rocks are characterized by abrupt lateral variations in lithology and thickness that make correlation difficult, even between closely spaced core sections. Because the Cannelton shale provides a consistent geophysical datum, its recognition greatly simplifies local and regional correlation of coal beds and provides an excellent datum for study of the controversial Pennsylvanian quartzarenites o the Lee Formation.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.