Maquoketa river, located in the Dissected Till plains of east-central Iowa, was established consequent on the Nebraskan and Kansan drift sheets and superposed across preglacial bedrock valleys eroded into the exhumed preDesmoinesian backslope of the Niagara cuesta. Where deeply entrenched into bedrock uplands, except in the Richland Highlands, modern Maquoketa river is bordered by rock terraces, which bevel structure. The presence of a series of shallow-phreatic caves 20 to 60 feet below the terraces, which transects structure, shows that the terraces are erosional, not structural, features. Caves related to the strath contain evidence of a time of aeration followed by complete re-submergence and filling with fluvial and lacustrine sediments. Because Maquoketa River valley has been neither aggraded nor dammed up to the level of the caves since Kansan time, the caves and, therefore, the strath are believed to be of Aftonian age. The Scotch Grove strath is topographically equivalent to and at Savanna, Illinois appears to merge with the Central Illinois peneplane and with Baselevel No. 3 of the Freeport Baselevel Section, but inability to find a definitive criterion common to all three regions prevents their unequivocal correlation.
Proceedings of the Iowa Academy of Science
©1963 Iowa Academy of Science, Inc.
Hedges, James and Jr., George W. Darland
"The Scotch Grove Strath in Maquoketa River Valley, Iowa,"
Proceedings of the Iowa Academy of Science, 70(1), 295-306.
Available at: https://scholarworks.uni.edu/pias/vol70/iss1/54