Robert T. Kay

Publication Date


Document Type


First Advisor

Perry, Eugene C., 1933-

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology


Geochemistry--Iowa; Water-rock interaction--Iowa; Aquifers--Iowa; Groundwater--Iowa


Water from the Pennsylvanian and Mississippian aquifers in south-central Iowa is high in sulfate and total dissolved solids in areas where Pennsylvanian shales and siltstones are present. Considering the flow patterns present in the major aquifers in the study area, there are three possible explanations for the source of the poor water from the Pennsylvanian and Mississippian aquifers, dissolution of evaporite minerals in the Mississippian strata, dissolution of evaporite minerals in the Devonian aquifer, and oxidation of sulfide minerals in the tills and Pennsylvanian strata. δ³⁴S sulfate isotopic values indicate that the source of most of the sulfur present in the Mississippian and Pennsylvanian aquifers is sulfide mineral oxidation. Plotting δ¹⁸O water against δ¹⁸O sulfate shows that the waters in the Pennsylvanian and Mississippian aquifers are isotopically indicative of meteoric water, while water in the Cambro-Ordovician aquifer has a glacial source. Plotting δ¹⁸O sulfate against the sulfate concentration shows that both water oxygen and molecular oxygen are used to oxidize the sulfide minerals and that water oxygen is used only after molecular oxygen has been consumed.


Bibliography: pages [109]-113.


viii, 113 pages




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