PALEOSOLS AND ICHNOFOSSILS OF THE UPPER PENNSYLVANIAN–LOWER PERMIAN MONONGAHELA AND DUNKARD GROUPS (OHIO, USA): A MULTI-PROXY APPROACH TO UNRAVELING COMPLEX VARIABILITY IN ANCIENT TERRESTRIAL LANDSCAPES

Abstract

The upper Monongahela and lower Dunkard groups of southeastern Ohio include abundant paleosols containing ichnofossils as well as vertebrate, invertebrate, and plant body fossils. These paleosols formed on diverse Late Pennsylvanian to Early Permian landscapes in an alluvial setting. This study investigated small-scale lateral and vertical variability of the paleosols that formed at the distal edge of the Dunkard Basin. Three detailed, 32-m thick stratigraphic sections across a 70 m outcrop were measured in eastern Athens County, Ohio. Seven pedotypes representing soil formation in nine subenvironments were identified through bulk geochemical, clay mineralogical, and petrographic analyses as well as a detailed study of the ichnofossils, body fossils, and macromorphological paleosol properties. Ichnofossils were abundant and included rhizoliths, actively to passively filled burrows, and coprolites. These ichnofossils were produced by various plants, larval and adult arthropods, and micro- to macro-vertebrates. Body fossils within the paleosols included micro- and macro bone fragments and teeth, compression plant fossils, ostracodes, and gastropods. Vertical transitions among the subenvironments were due to both fluvial channel migration and climatic changes. Precipitation was seasonally distributed with a range of mean annual precipitation (MAP) from 300–1000 mm/yr through the section. This study demonstrates that by investigating the small-scale lateral and vertical variations in paleosols, finer resolution paleoclimatic, paleoenvironmental, and paleoecological reconstructions are possible.