Date of Award
Master of Science (MS)
Abundant and well-preserved Late Quaternary fossils were exposed at the McClusky Canal Site in the Missouri Coteau district of central North Dakota during the late summer and fall of 1976. Strati graphic units, in ascending order, are: (l) pebbly, clayey sand; (2) unlaminated, organic claystone; (3) laminated, organic claystone; (4) pebbly, sandy claystone; (5) laminated, organic claystone; (6) gypsiferous claystone; and (7) silty claystone. Units 1 and 4 are inter preted to be till, and the remainder are lacustrine sediments. Total thickness of the section is 6.0 m.
Radiocarbon dates of 12,595 ± 375 radiocarbon years B.P. (from the boundary between units 2 and 3) and 10,955 ± radiocarbon years B.P. (from the base of unit 5) indicate that the average rate of sedimentation for unit 3 was 32 cm per thousand years. Assuming constant sedimentation rates, the highly organic units were deposited approximately 13,000-9600 years ago.
Sediment samples yielded at least 4 species of sphaeriid bivalves, 9 species of gastropods, 17 genera of plants, and 13 taxa that were identified only to the family level or above. Both mollusc and plant macrofossils are most abundant and diverse in units 2 and 3. The fossil assemblage of these units resembles modern com munities in northern Minnesota lakes. Spruce seeds, cones, and needles indicate that the lake was surrounded by spruce forest during the deposition of units 2 and 3. The decline of the spruce forest, which can be used to mark the Pleistocene-Holocene boundary, occurred at the McClusky Canal Site about 10,500 B.P.
Fossil assemblages in units 6 and 7 indicate a climatic trend of increasing warmth and dryness, accompanied by an increase in the concentration of dissolved salts. An increase in the proportion of sand in the sediment in the lower part of unit 7 may be evidence for the Hypsithermal episode, approximately 8200-5500 years ago.
Okland, Linda E., "Paleoecology of a late quaternary biota at the McClusky Canal Site, central North Dakota" (1978). Theses and Dissertations. 218.