Late Carboniferous (Stephanian B-C) collections at Ohio University include over 7,000 three-dimensional, cellularly preserved plant fossils from North American midcontinent cyclothems. This is the best preserved and most stratigraphically complete collection of Stephanian plant fossils in the world. The plants from each cyclothem are preserved in offshore marine shales and constitute an assemblage from a diverse suite of terrestrial environments. Systematic analysis using thin sectioning, peel techniques and scanning electron microscopy to document the cellular features will determine which Stephanian plant groups are present and identify new taxa. Typically, very few offshore marine units contain well preserved terrestrial plant debris. The taphonomic constraints influencing preservation of these Stephanian plants deposited in cyclothem beds of middle to outer shelf offshore marine environments have not been fully determined. Marine organism interaction with the transported plant debris and an understanding of the depositional conditions will resolve the taphonomic pathways involved. This combined research on plant systematics and marine taphonomic constraints is significant because it allows the first extensive documentation and analysis of terrestrial floras in the offshore marine environment. This data base will allow detailed comparison with rare Stephanian floral communities from coal swamps and the drier upland environments.
