A Comparison of the Late Wisconsinan Molluscan Fauna of the Missouri Coteau District (North Dakota) with a Modern Alaskan Analogue
Study of forty fossiliferous sites in late Wisconsinan sediments from the Missouri Coteau district in central North Dakota has defined the molluscan fauna of the period of geologic time between 12,000 and 9,000 C14 years before the present. The fauna includes twenty-eight taxa of nonmarine gastropod...
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UND Scholarly Commons
1969
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| Online Access: | https://commons.und.edu/theses/302 https://commons.und.edu/context/theses/article/1301/viewcontent/Tuthill__Samuel__J.__PhD_Thesis_1969.pdf https://commons.und.edu/context/theses/article/1301/filename/0/type/additional/viewcontent/Tuthill_Plates_1969.zip |
| Summary: | Study of forty fossiliferous sites in late Wisconsinan sediments from the Missouri Coteau district in central North Dakota has defined the molluscan fauna of the period of geologic time between 12,000 and 9,000 C14 years before the present. The fauna includes twenty-eight taxa of nonmarine gastropods and bivalves and is dominated by branchiates. The modern molluscan fauna of the Missouri Coteau district in North Dakota lacks four species which were resident in the late Wisconsinan and contains no unionids, one additional aquatic species, and is strongly dominated by pulmonate gastropods. The geology of the Missouri Coteau has been interpreted as being the sedimentary result of the stagnation of the marginal fifty to one hundred miles of the Wisconsinan ice sheet. The interpretation of the paleoecology of the late Wisconsinan molluscan fauna derives from geologic, paleoautecologic, and paleosynecologic data. It is hypothesized that at the time the late Wisconsinan continental ice sheet stagnated in central North Dakota, the climate was less extreme and more humid than at present. Ponds and streams existed on the ice-cored topography of the Missouri Coteau. They were connected by a drainage system tributary to the Missouri River and populated by an abundant, branchiate-dominated molluscan fauna. Fishes, probably of the families Percidae and Centrarchidae, lived in the ponds and rivers and unionid bivalves successfully populated many of the water bodies. Calcareous algae (Chara) and undoubtedly other species of aquatic vegetation colonized the clear, warm water of the drainage system. The ice-basined, drift-insulated lake was the most common lithotope in which fossil mollusks were preserved. The entire drainage system was supplied by greater rainfall and snowmelt than now occurs on the Missouri Coteau (probably in the order of 20 to 30 inches per year) and the precipitation - evapotranspiration ratio was positive. The humid climate changed toward the more arid climate of today before the ice core of the Coteau ... |
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