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Abstract: Evidence for Syndepositional Faulting and the Petrographic and Geochemical Characteristics of the Western Kentucky No. 4 Coal, Tradewater Formation (Desmoinesian), Western Kentucky

EBLE, CORTLAND F., GREB, STEPHEN F., and WILLIAMS, DAVID A.
Kentucky Geological Survey, University of Kentucky, Lexington, KY

The No. 4 coal bed, which occurs in the upper part of the Tradewater Formation (Raccoon Creek Group), is the stratigraphically oldest coal of major economic importance in western Kentucky. The coal is economically important because it generally exhibits lower ash yields and sulfur contents than most western Kentucky coals.

The No. 4 coal was sampled within, and south of the Pennyrile Fault System, along the southern rim of the Illinois Basin. Samples show the coal to be low to moderate in overall ash yield (5 to 10 %, dry basis) and moderate in overall total sulfur content (2 to 3 %, dry basis). However, the coal exhibits considerable lateral and vertical variability, with ash yields ranging from less than 2 % to more than 15 %, and total sulfur contents from less than 1 % to more than 8 % within individual bench samples.

In several mines, coal dip and thickness were influenced by syndepositional faulting. In one surface pit, the coal thickened from 75 cm to 150 cm down a fault ramp, before being offset along the hanging wall of a small fault. Soft-sediment deformation in the strata above the coal, where it dipped down the fault ramp, indicates that movement continued during burial of the peat and then subsided. In the same area, sulfur trends increased toward the main faults from 1 % away from the faults to greater than 3 % toward the faults. This example suggests that sulfur content in the No. 4 coal may have been partially controlled by fault-mitigated fluid migration, both during and immediately following peat deposition.

AAPG Search and Discovery Article #90930©1998 AAPG Eastern Section, Columbus, Ohio