USING MODERN TERRESTRIAL ORGANISMS TO IMPROVE THE INTERPRETATION OF PENNSYLVANIAN PALEOSOLS AND CONTINENTAL ICHNOFOSSILS OF THE APPALACHIAN BASIN

Ichnofossils provide an in situ record of paleoenvironment, paleoecology, and paleoclimate. As such, they have become essential to the analysis of sedimentary facies. The identification of tracemakers as well as the interpretation of environmental factors such as temperature and precipitation, depositional environments, and substrate characteristics from ichnofossil morphology is possible through the study of modern organisms and their trace-making behaviors.

Ichnofossils are abundant in paleosols of the late Pennsylvanian Conemaugh Group of southeastern Ohio. The paleosols developed on fluvial and lacustrine deposits in a low accommodation setting. Many of the ichnofossils present in these paleosols are undescribed and represent new potential tracemakers and behaviors. The Conemaugh ichnofossils were interpreted through the study of the burrowing behavior and biogenic structures of extant terrestrial animals in a laboratory setting. This research has involved several different annelids, arthropods, amphibians, and reptiles selected for their morphological, taxonomic, and ecological similarity to animals present in the Pennsylvanian of North America. The animals were placed in sediment-filled aquaria for two-week periods; the resulting traces were cast with plaster. Biogenic structures produced in the aquaria included subsurface burrows and chambers, as well as surface tracks and trails. Detailed descriptions of the cast traces include the architectural and surficial morphologies, type of fill, complexity, and tortuosity. Additional experiments exposed the animals to variations in substrate composition and moisture in order to correlate trace morphology to environmental conditions.

Biogenic structures produced in the laboratory have greatly improved the interpretation of the Conemaugh ichnofossils. Most of the ichnofossils represent locomotion, feeding, and dwelling behaviors of soil arthropods. Larger burrows were likely temporary to permanent dwellings of tetrapods. The type and diversity ichnofossils also provide data for the interpretation of soil consistency, soil moisture and water-table level, nutrient concentration, and sedimentation rates. Data obtained from the neoichnological experiments allow the quantification of these environmental variables.