Geochemistry of the Pond Creek coal bed, Eastern Kentucky coalfield

The Pond Creek coal bed (Middle Pennsylvanian Breathitt Formation) is an important low-sulfur resource in Pike and Martin countries in the Eastern Kentucky coalfield. The mined area is crossed by the N20°E-trending Belfry anticline. The Pond Creek coal bed has a higher sulfur content on the west side of the anticline. The vertical trends in the ash geochemistry also vary across the anticline. The sites to the east of the anticline represent deposition of peat through periods of relative stability with slow deposition (bright lithotypes) interspersed with periods of relatively rapid clastic deposition (dull lithotypes), both generally removed from marine influence. Comparison of elemental trends between the lowest bright lithotype and the second bright lithotype suggest that the swamp became less acidic with time. An upward decrease in minor-element concentration may be related to the influx of clays and other silicates present in the bone lithotype. This bone may have acted as a relatively low-nutrient soil for the growth of the plants which contributed to the overlying bright lithotype. The sites to the west of the anticline were subjected to a greater marine influence than the eastern sites. High K₂O/Al₂O₃ ratios at the bottom and top of the coal bed and a high TiO₂Zr dull clarain near the bottom of the coal point to clastic influences on the geochemistry. The relatively high CaO percentages in the middle third of the coal bed suggest deposition at near-neutral pH. The upper third of the coal bed was dominated by syngenetic and epigenetic pyrite emplacement.