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Reevaluating Evidence For The Pre-Lllinoian Entrenchment Of Northeastern Iowa River Valleys, Curtis M. Hudak
Reevaluating Evidence For The Pre-Lllinoian Entrenchment Of Northeastern Iowa River Valleys, Curtis M. Hudak
Journal of the Iowa Academy of Science: JIAS
Previous workers have proposed a pre-Illinoian age for the deepest bedrock entrenchment of northeastern Iowa valleys. Lines of evidence used to support a pre-Illinoian age of entrenchment are: (1) deep bedrock-entrenchment interpreted to take "long" periods of time, (2) "valleys" filled with "red-weathered drift", which was interpreted as "old", (3) differences in cross-valley profiles supposedly related to glacial advances, (4) thick beds of gravel could only be deposited by outwash streams, and (5) glacially buried (drift-filled) bedrock valleys exist outside of the Paleozoic Plateau to the west and south. These inferences are questionable because: ( 1) erosion (entrenchment) rates are …