Publication Date


Document Type


First Advisor

Perry, E. C. (Eugene C.), 1933-

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology




Oxygen and hydrogen (deuterium) isotope ratios for the waters of the Cambro-Ordovician aquifer of northern Illinois closely approximate the ratios in meteoric water, implying that little isotope exchange has occurred between groundwater and rocks of the aquifer. Delta ¹⁸0 of groundwater in the system ranges from about -7 permil (vs. SMOW), characteristic of modern precipitation in Illinois, to about -12 permil, characteristic of modern precipitation in considerably colder climates than that of northern Illinois. The implication of this is that some of the water in the Cambro-Ordovician aquifer system of northern Illinois may have been stored since the Pleistocene. Pleistocene climatic evidence suggests that the light water is glacial meltwater. Based on δ¹⁸0 content, a map of % modern water has been contoured. Sulfur and oxygen isotopes in sulfate in northern Illinois groundwater suggest this sulfate to be a mixture.of two end-member compositions. One end-member (δS = +20, 6 δ¹⁸0 = +16) presumably is derived from Paleozoic sulfate minerals in rocks associated with the aquifer. The other sulfate component (δS = +2.6, δ¹⁸0 = +1.5) presumably results from oxidation of sulfides in the glacial drift overlying the aquifer. The presence of natural isotope tracers in the groundwater of northern Illinois and adjacent areas should prove useful in establishing recharge and possible flow patterns in this important aquifer.


Includes bibliographical references.


vii, 88 pages




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