THE UPPER PENNSYLVANIAN DUQUESNE COAL OF OHIO (USA) - EVIDENCE FOR A DYNAMIC PEAT-ACCUMULATING SWAMP COMMUNITY

An outcrop of the Duquesne Coal (Conemaugh Cyclothem) has the only sig nificant occurrence of coal balls in Upper Pennsylvanian (Stephanian B equivalent) sediments of the Appalachian Basin. Excellent preservatio n of plant debris within autochthonous pear has permitted a more refin ed reconstruction of the source plant community than reported in publi shed studies of other coals. Coal balls were quantitatively sampled fo r whole-plant species and mineralogical content. Shoot-root ratios wer e extremely high compared with values reported for other coals. The sa mples were analyzed using cluster analyses and non-metric multidimensi onal scaling (MDS) in order to differentiate microhabitats and stages of ecological succession within the general flora. Cluster analysis pr oduced 5 stable clusters, which agreed with the sequence of ecological succession as determined in a previous study, and with microhabitat d ifferentiation in contemporaneous seral stages. Three dimensions of th e MDS analysis provided the best fit to the data. The dimensions are i nterpreted as representing: (1) ecological time or succession; (2) inc reasing dominance of Psaronius tree ferns in the plant community; and (3) an increase in microtopological variation (probably hummock format ion). The initial stages of succession (oldest layers of permineralize d peat) are characterized by aerial debris from Mesoxylon, Sigillaria and Calamites, followed by an assemblage dominated by Chaloneria. This was succeeded by more species diverse assemblage, dominated by Neurop teris seed ferns and Psaronius tree ferns, with numerous subcanopy pla nts, including lianas, epiphytes and ground herbs. Late seral stages ( youngest layers of permineralized peat) were dominated by Psaronius tr ee ferns.