Further examination of the ragged edge of the herrin coal bed, Webster county, western Kentucky coal field

The Herrin (Western Kentucky No. 11) coal bed in the Dixon 7 1/2 min quadra ngle, Webster County, Kentucky, displays another manifestation of the thinn ing margin of the coal bed. Previous studies in adjacent Hopkins County hav e demonstrated that the coal is brecciated as the margin is approached. The brecciated coal is not always thin; 1.5 m of brecciated, inertinite-rich c oal was previously described to the southeast of the present study area. In general, the brecciated coals are considerably thinner than the 1.5-2-m-th ick, "normal" Herrin coal. Both cores studied are thin (22.6 and 33 cm) and display petrographic characteristics different from thicker Herrin coals. The cores described in the present study show some signs of brecciation; in certain cases, the fragmented macerals are cemented by exsudatinite. Multi ple generations of pyrite mineralization were noted in one core, with total sulfur exceeding 13% in the upper 8.48 cm lithotype. Overall, the cores investigated in this study, along with examples from pre vious studies, illustrate the progression of the Herrin coal from its absen ce, either through nondeposition or erosion, through thin, brecciated coals , to mineable coals. No other economic coal in western Kentucky shows as ma ny examples of the depositional edge as does the Herrin. All of the example s studied are from cores, emphasizing the need to study more than just the thick, mineable coals if the total extent of the coal body is to be underst ood. (C) 2001 Elsevier Science B.V. All rights reserved.