Date of Award
Doctor of Philosophy (PhD)
Lake Agassiz occupied the Red River Valley between about 13,800 and 9,000 years ago. The Late Wisconsinan ice sheet that covered the Red River Valley retreated far enough to expose the drainage divide in northern South Dakota and south-central Minnesota sometime after 14,000 B.P. and meltwater ponded behind this divide in Richland County. Before 13,800 the ice readvanced over this area and then retreated again. As the ice margin retreated northward, deposition of the Argusville and Wylie Formations took place. Sometime before 12,800 the ice advanced again into the Red River Valley as far as Traill County; the terminus of this advance is marked by the clay rich pebble-loam of the Huot Formation, and the Falconer Formation was deposited behind the Huot. Deposition of the Argusville Formation continued in the southern part of the basin. Deposition of the Brenna Formation began when the ice margin began retreating out of the Red River Valley. About 11,000 B.P. an eastern outlet into the Lake Superior basin was opened, and Lake Agassiz dropped from the Campbell level to below the Ojata level. During the period between 11,000 B.P. and 9,900 B.P. the lake level fluctuated several times, but most of the time the lake floor was subject to erosion. A stream network similar to that of the present day developed, depositing the Poplar River Formadon. About 9,900 B.P. the eastern outlets were plugged by ice and Lake Agassiz rose back to the Campbell level. The lake stood at this level for about 900 years; during this time the Sherack Formation was deposited.
The engineering properties of the Sherack Formation include low to moderate water content (17% to 56%), wide range of liquid limit (27% to 92%), and wide range of consistency index (22% to 86%). The northern part of the Brenna Formation has high water content (62% to 88%), a high liquid limit (63% to 104%), and very low penetration resistance (4 to 7 blows per foot). The southern part of the Brenna Formation and the Wylie and Argusville Formations have similar engineering properties. The range in water content (38% to 69%), liquid limit (39% to 93%), and penetration resistance (4 to 16 blows per foot) for these units are similar. The Poplar River Formation is under confined piezometric conditions, and pilings or footings in it are subject to failure. The Falconer and Huot Formations have engineering properties similar to the Sherack, Wylie, and Argusville Formations. The glacial sediments underlying the Lake Agassiz sediment provide a suitable foundation for nearly all types of construction.
Arndt, Michael B., "Stratigraphy of offshore sediment of Lake Agassiz, North Dakota" (1975). Theses and Dissertations. 7.