Date of Award


Document Type


Degree Name

Master of Arts (MA)



First Advisor

F.D. Holland, Jr


This thesis here abstracted was written under the direction of Frank D. Holland, Jr. and was approved by Wilson M. Laird and George C. Wheeler as members of the examining committee, of which Dr. Holland was Chairman.

Geologic and paleontologic evidence indicates that numerous mesotropic, temperate, water bodies were present while drift-covered bloacks of stagnant glacier ice, unplaced during Woodfordian (late Wisconsinan, Pleistocene) time, underlay the Missouri Coteau district (approximately 50 by 300 miles in extent) in central North Dakota.

Fossil mollusks, contained in sediments deposited in contact with the stagnant ice at 40 sites, are represented by 23 species including polecypods of the families Unionidae and Sphaeriidae and gastropods of the families Valvatidae, Hydrobiidae, Physidae, Lymnaeidae, Planorbidae, Ancylidae, Succineidae, and Pupillidae. ____ shells have provided material for five radiocarbon dates in the Missouri Coteau district which indicate the melting of the stagnant ice may have required 2,100 years.

The fossil mollusks, as now known, do not serve as stratigraphic indicies to the late Pleistocene deposits of the region, but the species composition of fossil Mollusca communities dominated by the branchiate genera Valvata and Amnicola is required as tentative evidence of the pre-_____ age of the Missouri Coteau sediments. The mollusks also indicate the climate of the region to have been mild and humid as early as 12,000 and as late as 8,700 radiocarbon years before the present.

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