Palynologic and petrographic variation in the Pond Creek coal bed, Pike County, Kentucky

Recent studies of the petrology and ash geochemistry of the Pond Creek coal bed (Middle Pennsylvanian Breathitt Formation) in Pike and Martin Countries, Kentucky, have defined vertical and lateral trends that are related to the development of the northeast-trending Belfry anticline contemporaneous with the deposition of the Pond Creek peat. To the northwest of the anticline the coal bed has a high-CaCO₃ middle zone and a high Fe₂O₃-high sulfur upper zone. To the east of the anticline, particularly in the Lick Creek and Jamboree 7 1 2′ quadrangles, the coal bed exhibits a distinctive petrographic zonation. In the latter area, the usual megascopic sequence is a basal durain followed by a bright clarain-durain/dull. The palynology of the Pond Creek coal bed was investigated in six sets of bench/lithotype samples from the Lick Creek and Jamboree 7 1 2′ quadrangles. The low-vitrinite basal durain (zone 1) has a palynomorph assemblage which reflects the importance of tree ferns and herbaceous lycopods. The easternmost site has a bright clarain below the durain. The latter lithotype has a fair diversity of palynormph groups and also has the highest percentage of arborescent lycopod forms of any bench below the bone (zone 5). The bright zone 2 above the durain has the greatest maceral group range and the greatest floral diversity of any of the lithotypes. The zone 3 dull lithotype has increased amounts of herbaceous lycopods and decreased amounts of arborescent lycopods, sphenopsids and tree ferns. The zone 4 bright lithotypes are generally over 80% vitrinite and, in general, exhibit a dominance of arborescent lycopods although sphenopsid, tree fern and small fern forms exhibit varying importance. The high-ash bone (zone 5) has 71.6-77.0% vitrinite. This lithotype is marked by a dominance of herbaceous lycopods at the expense of arborescent lycopods and sphenopsids. The zone 6 bright clarian is marked by an increase in arborescent lycopods and a large decrease in herbaceous lycopods. The low-vitrinite terminal durain has an assemblage with high percentages of herbaceous lycopods and low percentages of arborescent lycopods as well as increase in tree fern spores over zone 6. In general, the petrology and palynology trends are predictable. Dull lithotypes have abundant herbaceous lycopod representation and bright lithotypes have abundant arborescent lycopod representation. The greatest deviation from this simple pattern is within the zone 4 bright lithotypes, where diverse palynomorph assemblages occur among the high-vitrinite benches. Overall, the greatest floral diversity appears to have occurred near the base of the coal bed.