Chemical and stable-isotope data for water from wells completed in the Glaciofluvial aquifer in the central Lower Peninsula of Michigan were used to prepare maps that show the areal variation of 8180; distribution of dissolved solids, dissolved chloride, dissolved iron, and dissolved sulfate; and distribution of hydrochemical facies. Delta oxygen-18 values indicate the presence of modem meteoric water (6180 approximately 40 parts per thousand) and glacial-age meteoric water, which is isotopically light 0180 less than -15 parts per thousand). Isotopically light ground water is present in the Saginaw Bay Area in the eastern part of the study area. Dissolved-solids concentrations are generally less than 1,000 milligrams per liter, and dissolved-chloride concentrations are generally less than 100 milligrams per liter. These concentrations are greatest in ground water from the Saginaw Bay Area where measured concentrations are as large as 12,000 milligrams per liter for dissolved solids and 6,700 milligrams per liter for dissolved chloride. Dissolved-iron concentrations range from 0.001 to 6.0 milligrams per liter. Dissolved-sulfate concentrations range from 1 to 1,800 milligrams per liter. Most ground water from the Glaciofluvial aquifer is classified as a calcium bicarbonate type. In the Saginaw Bay Area, ground water is a sodium chloride type.
