A CRITICAL ANALYSIS OF THE HIGHER PENNSYLVANIAN MEGAFLORAS OF THE APPALACHIAN REGION

Published records of Stephanian megafloras in eastern North America ar e critically reviewed and the results of personal investigations in th e AppaIachian region are reported. This includes a partial revision of the lower Conemaugh flora of eastern Ohio reported by McComas (1988); selected elements of this flora are reported here. The megafloral rec ords of this region are scattered, incomplete and of variable quality. Nevertheless, our analysis allows the conclusion that the succession in the Appalachian area hides a large stratigraphic gap, at the base o f the Upper Pennsylvanian Series. This gap is in the same position and of similar magnitude to that below the Rotliegend of northwestern Eur ope. The highest Allegheny, below the gap, reaches a basal Cantabrian level at the Upper Freeport coal bed and perhaps already at the Upper Kittanning horizon. The lower Conemaugh, above this gap, belongs to th e (upper?) Stephanian C. Thus, most of the Stephanian is missing in th e Appalachian region. Analysis of the floral records in the Southern A nthracite held shows evidence of a similar gap. Megafloral data from t he Narragansett basin are analysed, but are found insufficient for det ermining if there is a stratigraphic gap. Published data from the Mari time Provinces of Canada are used to suggest that the same pre-Rotlieg end gap exists in this area. Recognition of this important regional un conformity in eastern North America, which is similar to that in the B ritish Isles and throughout northwestern Europe, strengthens the view that the Appalachian region and the paralic coal belt of northwestern Europe constitute a single, major palaeogeographic area. Three new com binations are proposed: Lobatopteris pseudovestita (White) Wagner, com b. nov., L. tenuinervis (Fontaine et White) Wagner, comb. nov. and Mix oneura nervosa (Fontaine et White) Wagner et Lyons, comb. nov.