Date of Award

4-2007

Degree Name

Master of Science

Department

Geological and Environmental Sciences

Department

Geosciences

First Advisor

Dr. Alan E. Kehew

Second Advisor

Dr. Carla Koretsky

Third Advisor

Dr. Michael Barcelona

Access Setting

Masters Thesis-Open Access

Abstract

The objectives of this study are to characterize the stratigraphy of the glacial drift in an area located in Portage, Michigan using four complete rotasonic cores, and to determine the variation of organic carbon content in the drift that may explain the high iron concentrations in the groundwater typically obtained in moderate to deep wells in southwestern Michigan. The four cores were characterized in detail in terms of lithology, textural and statistical analyses, gamma ray logging, S13C variation and organic carbon analyses. Clay minerals were characterized using X-ray diffraction analysis.

Results of this study identified two main diamicton units that were differentiated by means of 7/1OA peak height ratios, mean matrix texture and stratigraphic position. Application of the t-test confirmed that the two units were significantly different at the 95% confidence level. Organic carbon contents of the diamicton units were significantly higher than in the outwash sediments. This organic carbon acts as an electron donor to drive redox reactions as groundwater passes through the diamicton units. Fe(III) in aquifer solids is the terminal electron acceptor in these reactions, and is reduced to the much more soluble Fe(II), thereby producing the high iron concentrations in groundwater.

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