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Document Type

Research

Abstract

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.

Publication Date

1963

Journal Title

Proceedings of the Iowa Academy of Science

Volume

70

Issue

1

First Page

295

Last Page

306

Copyright

© Copyright 1963 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf

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