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The Pleistocene Glacial Record At Two Quarries In Decatur County, Iowa, Keith E. Schilling, Robert A. Stewart

Journal of the Iowa Academy of Science: JIAS

The Pleistocene stratigraphy and sedimentology of two quarry exposures near Grand River and Decatur City in Decatur County, Iowa document a sequence of Pleistocene sediments overlying striated Pennsylvanian limestone which represent at least two pre-Illinoian glacial advances into the ancestral Grand River valley. Two pre-Illinoian diarnictons separated by a clast pavement were observed at the Decatur City quarry; a single diarnicton was present at the Grand River quarry. At both quarries, the diarnictons exhibit comparable lithologic properties and are genetically interpreted as basal tills. The pre-Illinoian tills are tentatively correlated with the Alburnett Formation in eastern Iowa, primarily on the …