Date of Award
Doctor of Philosophy (PhD)
This is a report of a reconnaissance study of the Quaternary geology of an area in northwestern Minnesota. Surface geology was studied in an area extending from Grand Forks, North Dakota, in the northwest to Bemidji, Minnesota, in the southeast, an area of 10 723 square kilometres (4140 square miles). Near-surface stratigraphy was studied in the area of surface study and an adjacent area of equal size to the south.
Surface materials mapped range in age from Pleistocene to Holocene and include glacial, glaciofluvial, lacustrine, bog, eolian, and alluvial sediments.
Sixteen power-auger test holes, two measured sections along the Red Lake River, two composite sections from earlier drilling pro grams and surface exposures were used to characterize seven near surface lithostratigraphic units in the area. From oldest to youngest they are unnamed unit 1, unnamed unit 2, the Marcoux Formation, and the St. Hilaire Formation. These units are largely glacial sediment and pre-Wisconsinan or Early Wisconsinan in age. The Red Lake Falls Formation and the Huot Formation are largely glacial sediment and Wisconsinan and latest Wisconsinan in age. The Sherack Formation is largely lacustrine sediment and is latest Wisconsinan and Holocene in age. The lithostratigraphic units present are differ entiated by means of their texture and coarse-sand lithology.
During the Pleistocene an unknown number of glaciations occurred before the deposition of the glacial sediments of the oldest litho stratigraphic unit observed, unnamed unit 1. Three pre-Wisconsinan or Early Wisconsinan glaciers deposited the glacial sediments of unnamed unit 1, unnamed unit 2, and the Marcoux Formation over the entire area. Wisconsinan glaciers advanced into the area, flowed around the Itasca Highland, and retreated twice, depositing the glacial sediment of the St. Hilaire and Red Lake Falls Formations. The late Wisconsinan and Holocene lake sediments of the Argusville, Wylie, and Sherack Forma tions were deposited in Lake Agassiz during the retreat of the glacier that deposited the Red Lake Falls Formation and the advance and retreat of the glacier that deposited the Huot Formation. Lake Agassiz drained at about 9500 BP.
Harris, Kenneth L., "Pleistocene geology of the Grand Forks-Bemidji area, northwestern Minnesota" (1975). Theses and Dissertations. 125.