Nature of petrographic variation in Taylor-Copland Coal of Middle Pennsylvanian Breathitt Formation of eastern Kentucky

The Taylor-Copland Coal is petrographically distinctive in that it has lowest average vitrinite content (63%) and concomitant highest inertinite (25%) and exinite (12%) of all eastern Kentucky coals. Additionally, average total sulfur is 3.4%, or nearly twice the 1.8% figure determined for all eastern Kentucky samples. Deviations from the maceral averages are equally distinctive. Particularly interesting is an areally extensive, though discontinuous, sample sequence showing significantly lower vitrinites (commonly 40%), very high inertinites (40%), and high exinite content (15-20%). This "high inertinite" trend is traceable over an east-west linear distance of at least 20 mi (32 km), is occasionally interrupted along trend by samples having higher than average vitrinite, and probably disappears completely southward where coals with high vitrinite-lower inertinite contents prevail. The high-inertinite and high total-sulfur trends and variations for each were presumed to be related to proximity to the coal of marine lithologic units of the overlying Magoffin Member. However, it was found that maceral and possible sulfur trends are probably unrelated to roof rock variation, but are related to existence or absence of a thick durain coal lithotype toward the middle of some coal beds. When present, the durain is commonly interspersed with fusain and/or pyrite bands or lenses, and is microscopically observed to be enriched in inertinite-exinite. Palynology reveals that spores in the durain-rich samples are poorly preserved (micrinitized), but assemblages and relative percentages of genera forming the assemblages remained unchanged from those found in high-vitrinite (durain-free) samples. Unchanged spore assemblages possibly indicate that unchanging plant communities existed through the durain-forming episode of the Taylor-Copland swamp. Rather, the effect of the durain phase on the Taylor-Copland swamp was to accelerate degradation (oxidation) of peat deposits associated with the surrounding plant community. The durain deposit is thought to have accumulated within an encroaching brackish-marine water system. This influx may have represented an early, short-lived pulse of the same advancing marine system thatproduced the extensive overlying Magoffin deposits.