PALYNOLOGY OF LOWER AND MIDDLE PENNSYLVANIAN COAL BEDS IN THE CENTRAL APPALACHIAN BASIN: PALEOBOTANIC AND BIOSTRATIGRAPHIC IMPLICATIONS

The Central Appalachian Basin is a large, foreland basin in the eastern United States that covers parts of West Virginia, Kentucky, Ohio, Virginia and Tennessee. Compositional changes in spore and pollen assemblages from Lower and Middle Pennsylvanian age coal beds in the Central Appalachian Basin reflect temporal changes in coal forming floras. In addition, the occurrence of taxa with limited range zones assists in the placement of stage boundaries within the basin, and helps with correlation on a global scale.

Lower Pennsylvanian strata in the Central Appalachian Basin include the Pocahontas, New River, and lower one-third of the Kanawha Formation. Palynologically, a majority of the coal beds in this part of the section are dominated by Lycospora, indicating that large lycopod trees (e.g., Lepidodendron, Lepidophloios) were important elements of the peat-forming floras. Densosporites, and related crassicingulate genera, are also common in this part of the section, indicating the presence of Omphalophloios, a subarborescent lycopod. Biostratigraphically, the introduction of Laevigatosporites, Endosporites, Granasporites medius, near the middle of the Lower Pennsylvanian section, and termination of Radiizontes aligerans and Schulzospora rara, at the top, assist with coal bed identification and correlation.

Middle Pennsylvanian strata in the Central Appalachian Basin can be subdivided into lower, middle and upper parts, based on the occurrence of widespread marine zones. Lower Middle Pennsylvanian coal beds largely resemble their Lower Pennsylvanian counterparts, in that they typically are dominated by Lycospora. Although Lycospora remains an important component of middle and late Middle Pennsylvanian coals, a progressive increase in tree fern spore abundance, and diversity, is seen in this part of the section. The top of the Middle Pennsylvanian marks the termination point of several taxa, most notably Lycospora. Other biostratigraphically important taxa include Radiizonates difformis, Thymospora pseudothiessenii, and Torispora securis.

Local increases in calamite spores, and cordaite pollen occur throughout the Lower and Middle Pennsylvanian section. These are usually associated with mire margin areas where the coal is thin, and/or contains elevated amounts of mineral matter.