BIOTIC CHANGE AND LATE DEVONIAN FLOODPLAIN DYNAMICS IN THE CATSKILL FORMATION (UPPER DEVONIAN) IN PENNSYLVANIA

During the Late Devonian, components of the biosphere and geosphere interacted within continental floodplains to generate profound effects on the earth system. Among plant groups, the continuing evolution of the arborescent form, a deeper rooting horizon, and the origin of seeds permitted the invasion and partitioning of wetlands and other floodplain habitats in the terrestrial realm. The spread of plants profoundly impacted mechanical and chemical weathering, biogeochemical cycling, erosion dynamics, and the nature of alluvial deposition on the floodplains. Research at the Red Hill site in Clinton County, Pennsylvania, informs non-marine depositional models, particularly the avulsion model, and documents many elements of the flora and fauna living within diverse depositional settings of the Catskill Formation (Upper Devonian; Famennian). Plant material from Red Hill supports a model of habitat partitioning among higher order taxa. Archaeopteris progymnosperms appear to dominate on levees, Rhacophyton ferns are widespread on the floodplains, lycopsids thrive in the wetland habitats, and early seed plants occupy disturbed sites, particularly after fires. Likewise, habitat specializations among vertebrates living within Late Devonian floodplains may be reflected in body form, locomotor specializations, feeding mechanics, reproductive strategies and other life-history traits among disparate clades. Recovery of vertebrates from Red Hill and an ever-growing variety of sites in the Catskill Formation of north-central Pennsylvania are improving hypotheses of biosphere-geosphere feedback associated with the vertebrate invasion of continental ecosystems. Placoderm nurseries dominated by juvenile individuals have recently been documented, while occurrence patterns of some placoderms and small actinopterygians indicate specific habitat preferences. Several taxa from the tetrapodomorph sarcopterygian lineage show body forms specialized for shallow-water locomotion and predation. Continued recognition of vertebrate partitioning of continental floodplains of the Catskill Formation demonstrates the increasingly heterogeneous nature of these depositional settings and begins to inform the co-evolution of biotic and abiotic elements.