Strontium Anomalies in Till of the Powell-Union City Moraine, Ohio

Abstract

The strontium concentration of till from the Powell-Union City Moraine varies with grain size and has maximum values in the —120 + 200 mesh (70— 125 /Jim) fractions. It correlates positively with the carbonate content of till but depends also on the presence of feldspar, clay and other minerals. The strontium content of —120 + 200 mesh fractions of 19 till samples collected along the Powell-Union City Moraine increases from about 100 ppm in central Ohio up to 220 ppm at the Indiana border. The increase coincides with a change in the lithologic composition of the bedrock from sandstone and shale (Mississippian and Devonian) to carbonate rocks (Devonian and Silurian). Two positive strontium anomalies were found at Fulton and Piqua that might be attributed to the presence of celestite (SrSO4) derived from the underlying bedrock. However, no celestite was found in the till samples. The excess strontium concentrations of samples in the Fulton anomaly correlate positively with their K-feldspar/plagioclase ratios and appear to be caused by a change in the mineralogical composition of feldspar rather than by an increase in the abundance of this mineral. The cause for the Piqua anomaly is unknown.