PALEOSOLS AND ICHNOFOSSILS OF THE MONONGAHELA AND DUNKARD GROUPS: A MULTI-PROXY APPROACH TO UNDERSTANDING LATE PALEOZOIC TERRESTRIAL LANDSCAPES

Paleosols in the Upper Pennsylvanian to Lower Permian Monongahela and Dunkard groups of Ohio and West Virginia are abundant but poorly understood. The Late Paleozoic transition is a critical interval in Earth history in terms of tectonics, climate, and life. Paleosols can provide important data on how terrestrial environments and ecosystems were affected by these changes. The goal of this research is to document the changes in landscapes and soil ecosystems through this interval in the Appalachian basin and to determine the local and regional controls on soil development through time. A detailed case study of a 32 m section in Athens County, Ohio resulted in the recognition of eight pedotypes. Data was derived from three sections spanning 70 m including the description of lithologic, paleopedologic, ichnologic and paleontologic properties of paleosols in outcrop and thin section as well as the analysis of bulk geochemistry and clay mineralogy. Ichnofossils were abundant in the paleosols and included rhizoliths, burrows, plant feeding traces and coprolites produced by various plants, larval and adult arthropods and micro- to macro-vertebrates. Body fossils included bone fragments and teeth, compression plant fossils, ostracodes and gastropods. Nine soil-forming environments were interpreted from facies associations including palustrine, levee, proximal to distal floodplain, interfluve, backswamp, marsh, marsh channel and fen. Most facies were continuous across the outcrop, but lateral variations in paleosol properties and ichnofossil assemblages did occur. Vertical transitions between these subenvironments are attributed to fluvial channel migration (small scale) and climatic changes (large scale). Precipitation was seasonally distributed with MAP estimates ranging from 300–1000 mm/yr. This research provides an improved understanding of the complex relationships between paleosol properties and local-scale variations in hydrology, topography, parent material and biota.