Paleoecology of an upper Middle Pennsylvanian coal swamp from Western Pennsylvania, U.S.A.

Abstract

The first sufficient quantitative analysis of vegetation preserved in coal balls from the Allegheny Formation, late Middle Pennsylvanian age, was made in the present study by measuring 13,203 cm 2 from middle peels of over 300 coal balls or pieces of coal balls. The distinctive features of this flora are the dominance of lycopods, the absence of cordaitean plants, and the extremely low shoot/root ratio (0.74 for total plant remains, 0.24 for lycopods). It is suggested that the climate at the Derringer Corners coal swamps was a drier tropical climate, compared to that of some earlier coal-forming environment of the Appalachian Basin, and to those of coal swamps in the Illinois Basin during the Middle Pennsylvanian. The discrepancy between the abundance of lycopods (as an indicator of a wet environment or habitat) and the low shoot/root ratio (inferring relatively dry conditions) in the coal-forming peat swamps at the Derringer Corners indicates that the actual set of factors causing massive reduction of arborescent lycopods at, or near, the boundary between Middle and Late Pennsylvanian would be much more complex than simply a “drier climate”. Some local factors, such as edaphic, perhaps geomorphic conditions, and local events, might play an important role in creating a favorable environment for the growth of lycopod trees.