Journal of the Iowa Academy of Science: JIAS Volume 95 Number Article 3 1988 Reevaluating Evidence for the Pre-lllinoian Entrenchment of Northeastern Iowa River Valleys Curtis M. Hudak University of Iowa Let us know how access to this document benefits ouy Copyright © Copyright 1989 by the Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/jias Part of the Anthropology Commons, Life Sciences Commons, Physical Sciences and Mathematics Commons, and the Science and Mathematics Education Commons Recommended Citation Hudak, Curtis M. (1988) "Reevaluating Evidence for the Pre-lllinoian Entrenchment of Northeastern Iowa River Valleys," Journal of the Iowa Academy of Science: JIAS, 95(4), 109-113. Available at: https://scholarworks.uni.edu/jias/vol95/iss4/3 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Journal of the Iowa Academy of Science: JIAS by an authorized editor of UNI ScholarWorks. For more information, please contact
[email protected]. ]our. Iowa Acad. Sci. 95(4): 109-113, 1988 Reevaluating Evidence for the Pre-lllinoian Entrenchment of Northeastern Iowa River Valleys 1 CURTIS M. HUDAK2 Department of Geology, University of Iowa, Iowa City, Iowa 52242 Previous workers have proposed a pre-Illinoian age for the deepest bedrock entrenchment of northeastern Iowa valleys. Lines of evidence used ro support a pre-Illinoian age of entrenchment are: ( 1) deep bedrock-entrenchment interpreted ro 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 ro the west and south.