GEOCHEMICAL AND MINERALOGICAL INVESTIGATION OF THE WISCONSIN AGE GLACIAL TILL OF PEFFER PARK OXFORD,OHIO : AN IMPORTANT ENVIRONMENTAL REFERENCE MATERIAL FOR METAL POLLUTION STUDIES

Glacial tills form the Wisconsin glaciation are important environmental materials because they are parent materials for soils, play important hydrogeologic roles and are a major control on background chemistry. One aspect of glacial tills that is poorly understood is the extent and variation of concentrations of metals of environmental concern as well as mineralogical variability. These are important parameters to constrain for a variety of applied environmental questions such as background determination for pollutants and geotechnical behavior.

Several (n=20) samples from a single representative Wisconsin till outcrop in Peffer Park located just outside Oxford, Ohio was analyzed to assess chemical and mineralogical content and variation. The till was poorly sorted with its grain size distribution being mainly comprised of clay (~40 to 60%) and some silt (~20 to 30%) and there were some small clasts (~5 to 25%). Clasts were typically no larger than 25 mm in diameter. The overall texture was homogenous at the decimeter to meter scale. For selected elements of environmental concern the ranges of concentrations observed by inductively coupled plasma – mass spectrometry (ICP-MS) are As (3.2 – 20.9 ppm), Ba (304.1 – 402.9 ppm), Co (7.6-12.7 ppm), Cr (35.8-58.4 ppm), Cu (14.0-20.4 ppm), Sn (b.d. – 0.5 ppm), Th (3.6 – 7.5 ppm), U (0.9-1.7 ppm), W (0.5 to 0.7 ppm), and Zn (11.4-34.5 ppm). Clay mineralogy of the till is dominated by ripidolite and illite. Powder X-ray diffraction indicates that the non-clay mineralogy of the till is dominated by quartz, calcite and dolomite. The results of this study provides a significant quantification of background for ongoing and future studies of vehicular pollution, coal pollution, machining pollution (tungsten) and uranium pollution from the Fernald site and other outlier sites. The clay mineral assemblage is rich in ripidolite (Fe-rich chlorite) which typically has reduced iron and may be an electron source in biogeochemical cycles. This work illustrates that the Peffer Park till serves as an important environmental reference material for the region.