Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

W.M. Laird


The thesis here abstracted was written under the direction of Wilson M. Laird and approved by John R. Reid and Alan M. Cvancara as members of the examining committee, of which Dr. Laird was Chainnan.

During the summer of 1964 a study of the Turtle, Forest, and Park river valleys was undertaken to find evidence of former changes in river regimen. The regimen of rivers once draining into glacial Lake Agassiz was probably affected by changes in base level associated with fluctuations of that lake. The Turtle, Forest, and Park rivers, which presently flow eastward across the bed of Lake Agassiz, show little irrefutable evidence of base level fluctuations.

Numerous terrace-like surfaces are found in these valleys from the area of the beaches headward. The lowest and most prominent surface is about 8 to 12 feet above river level. Overbank deposition occurs on this surf ace during periodic floods. It is the ref ore a product of the present river regimen and is an active floodplain. Other, higher, surfaces in these valleys are, however, true terraces. Most are unpaired and none can be traced for more than one mile. None can be directly related to a particular stand of glacial Lake Agassiz.

Twenty-five feet of sandy silt exposed in a cutbank in the Park River valley suggests fluctuations in base level. Erosion of the valley may have occurred during the Lake Agassiz I-II interval, followed by aggradation as base level rose during Lake Agassiz II time. Sub sequent to drainage of the lake, the river has eroded this fill.

Seven mussel species were collected from cutbanks on the Turtle River. They represent essentially a small river or creek fauna. Three of these species do not presently inhabit the river.

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