Sr/Sr Ratios in Ground Water in and around Cedar Bog, Ohio

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Isotopic ratios of 87Sr/86Sr were measured in 57 ground and surface water samples taken from in and around Cedar Bog in an effort to determine the provenance of the bog waters. Cedar bog lies in Champaign County, southwest Ohio, and it and its surrounding area are underlain by a variety of glacial deposits. The aim of this study is to delineate which of these deposits is the source of the water in the bog. Strontium was separated from the water samples and the isotopic ratios determined using standard methods. The range of values for this ratio is 0.00117 (0.70826 - 0.70943), which is more than 50 times the precision of an individual ratio as measured by modern mass spectrometry. Analyses of waters collected from a single site, however, show that these ratios vary over a small but measurable range through time. Such variations are most likely caused by local differences in the amounts of silicate and carbonate material in the glacial units and by local variations in precipitation and runoff, and they form a background noise in studies such as these. Efforts to characterize the individual glacial units by the 87Sr/86Sr ratios in their ground waters are hampered by this noise and by uncertainties, when sampling water wells, as to which glacial units yield the water in the wells. Although these factors make it difficult to trace the ground waters back to individual glacial units, the data do indicate that Cedar Bog waters are most likely derived from the area northeast of the bog and that they are unlikely to be derived entirely from the Mad River outwash.


Author Institution: Floyd Browne Associates, Inc. and Department of Geological Sciences, Wright State University



The Ohio Journal of Science. v93, n1 (March, 1993), 27-34