61st Annual Report on Research 2016

The purpose of this project is to study the paleosols of the Upper Pennsylvanian to Lower Permian Dunkard Group in southeastern Ohio to develop a better understanding of the relationships between paleosol properties and local scale variations in hydrology, topography, parent material, and biota. In addition, these studies will be used to reconstruct the Late Paleozoic terrestrial landscapes of the Dunkard foreland basin and improve the understanding of the changing climate over this transitional interval of Earth history.

During third year of the project my students and I have undertaken field and laboratory work on multiple field sites with exposures of the Washington Formation and lower Greene Formation of the Dunkard Group in Athens and Meigs counties in Ohio. These field areas have allowed the investigation of multiple coeval paleosols through these units. We have begun a study of large burrows in a sandstone unit (Marietta Sandstone?) located in a roadcut in eastern Athens County. These burrows (cf. Camborygma) likely represent dwelling of freshwater decapod crustaceans and, if so, are a new occurrence of this type of animal in the region. Outcrops in Meigs County are correlative to those studied in eastern Athens County in the first year of the project. In the Meigs County localities we have constructed 15 detailed stratigraphic sections from three new localities and described multiple occurrences of five different types of paleosols from the outcrop and hand sample descriptions. Samples were collected for the preparation of thin sections as well as geochemical and clay mineralogical analyses. The bulk geochemistry and thin sections have been completed and are currently being analyzed and interpreted. New continental trace fossils and plant fossils have also been described from the localities which will provide invaluable evidence to characterize the fauna and flora that occupied the landscape surface and the subsurface. The plant fossils will also provide stratigraphic control for the field sites.

The described paleosols formed on proximal to distal floodplains of a meandering to anastomosed river system. The paleosols are associated with fine- to medium-grained sandstone bodies and show a trend of forming in environments proximal to distal active channels. There is an upward trend of increasing paleosol maturity and landscape stability. The paleosols include Entisols, Inceptsiols, Histosols, and calcic to gleyed Vertisols that show strong influence by autogenic processes due to pronounced lateral variation in the properties of individual paleosol horizons within and between outcrops. These variations include development of horizons, development of peds and cutans, presence and composition of nodules and concretions, and depth of rooting and burrowing. Lateral changes in topographic relief, drainage conditions, and soil organisms appear to have had the greatest degree of control in altering these paleosol properties across space. Despite these variations, however, major features of the paleosols, including those that help define their paleosol orders, were consistent across coeval units. We also noted a strong allogenic signal in the vertical changes in paleosol properties, suggesting an overall control by changing climate from higher precipitation near the base of the section associated with Inceptisols, gleyed Vertisols and Histosols to lower and more seasonal precipitation near the top of section associated with calcic Vertisols.

The third year of this grant has involved the participation of two undergraduate students and one graduate student in the Department of Geological Sciences at Ohio University. The students conducted research at the field localities, measuring sections, describing hand samples, and collecting samples for laboratory analyses. Results of this research have been presented in one talk given by my current graduate student at the 2016 Geological Society of America Annual Meeting in Denver, CO. Since the start of the grant, two graduate students have graduated with Masters of Science degrees in Geological Sciences (2014 and 2015) with thesis projects involving paleosols of the Dunkard Group. I have published a paper with one former graduate student Michael Blair in Palaeogeography, Palaeoclimatology, Palaeoecology (2016; v. 454, p. 246-266). A second paper is currently in review with PALAIOS and two more are in preparation.

At the start of the fourth year of the grant, I have one new graduate student and one continuing undergraduate student that have started to work on the project. We are in the process of reviewing the work that has already been conducted over the last three years and investigating new field localities.