Dissertations and Theses @ UNI
Availability
Open Access Thesis
Keywords
Karst--Iowa; Geology--Iowa; Geology, Stratigraphic--Silurian; Geology; Geology, Stratigraphic; Karst; Silurian Geologic Period; Iowa; From 405 to 425 million years ago;
Abstract
This research investigates the spatial distribution of surface karst features along the Silurian Escarpment in northeastern Iowa. A 30 square mile area of Elk Townships in Cla:rton and Delaware Counties was selected for intensive investigation. All surface karst features within the study area were located in the field and plotted on a 7.5 minute topographic map. A generic model is presented to explain the process, causation, and geologic time period of active karstification. Field evidence supports the hypothesis that the karst landforms along the Silurian Escarpment in northeastern Iowa are not solutionnl in nature, but rather mechanically induced features. The massive Silurian materials of the escarpment rest upon a weak Ordovician shale known as the Maquoketa Shale. Upon saturation, this material weathers to a plastic blue clay and becomes deformed from the weight of the overlying Silurian dolomites. The failure of the Maquoketa Shale has resulted in tension fracturing in the Kankakee and Edgewood Formations of the Silurian. Large joint-defined blocks of dolomite have been displaced vertically and horizontally along the Silurian Ordovician contact by gravity sliding. Fracturing of the uppermost Silurian unit, the Hopkinton Formation, has also occurred. Along the edges of the escarpment where the Hopkinton Formation has been most deformed by fracturing from unstable conditions beneath, surface drainage has been diverted underground and surface karst features are manifested.
Year of Submission
1976
Degree Name
Master of Arts
Department
Department of Geography
First Advisor
John Gunter
Second Advisor
Basheer Nijim
Third Advisor
Stanley Grant
Date Original
1976
Object Description
1 PDF (112 leaves)
Copyright
©1976 Ardith K. Hansel
Language
en
File Format
application/pdf
Recommended Citation
Hansel, Ardith K., "Mechanically Induced Karst Development Along the Silurian Escarpment in Northeastern Iowa" (1976). Dissertations and Theses @ UNI. 2868.
https://scholarworks.uni.edu/etd/2868
Comments
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