Date of Award
Doctor of Philosophy (PhD)
Southern Nelson County occupies 576 square miles in northeastern North Dakota (Twps. 149-152 N., Rgs. 57-62 W.). Its surface is mantled with glacial drift resting unconformably on the Cretaceous Pierre Shale, which is exposed along the Sheyenne River Valley and the Stump Lake Basin. The entire mantle of glacial drift is part of the Coleharbor Formation, which, in southern Nelson County, averages 45 feet thick with a maximum thickness over 200 feet. Drill-hole data and missile site excavations provide good evidence for the existence of multiple drift sheets, including layers of till separated by more than 25 feet of outwash, several buried oxidized zones, and buried soil horizons. Evidence for pre-Wisconsinan drift is based on the discovery of com pact and jointed till in the Minuteman Missile site excavations. The primary lithologies of the Coleharbor Formation include non-bedded diamicton, indistinctly bedded gravel, poorly bedded sandy silt, ·cross bedded sand and horizontally ledded silt. Most of the units contain an abundance of shale particles with some having shale cobbles 6- to 8-inches in diameter. The maximum thickness of the Coleharbor Formation occurs in two preglacial "alleys, the Hamar Valley and the McVille Channel, both in the southwestern corner of the county. The McVille Channel is more than 200 feet deep along its entire length, but its gradient direction is yet unknown. The Hamar Valley is a much broader valley than the McVille Channel. It has a northward gradient and is also more than 200 feet deep along most of its extent in southern Nelson County. Because of the, Northward gradient of the Hamar Valley and other buried channels west of Nelson County, the gradient of the McVille Channel is also assumed to be northward.
The surface drift of Nelson County was deposited during the retreat of the Leeds Lobe in late Wisconsinan time. Deglaciation of the county began about 13,000 radiocarbon years B.P. upon the retreat of the ice from the McHenry and Cooperstown moraines in the south western corner of the county. The next prolonged stand of the glacier margin occurred at about 12,900 radiocarbon years B.P. depositing the North Viking and Kloten moraines. The Kloten Moraine may be the northward extension of the Luverne Moraine, previously mapped in the counties to the south. Neither the North Viking Moraine nor the Kloten Moraine is a very striking feature. Relief increases only gradually over fairly broad areas and both moraines have doughnut shaped ridges, indicating stagnant ice deposition. Such ridges are especially abundant in the northern part of the Kloten Moraine.
During the deposition of the North Viking and K1oten moraines the glacial Sheyenne River was formed. It originated as a small proglacial stream whose headward erosion captured the overflow of glacial Lake Souris, enlarging its channel to a width of 3000 feet and a depth of 100 feet. The resulting average annual discharge of the glacial Sheyenne River is estimated to have been about 500,000 cubic feet per second.
The retreat of the glacier from the North Viking Moraine initiated the formation of the glacial ancestors of two of the largest lakes in North Dakota, Devils Lake and Stump Lake. During maximum lake levels water probably reached an elevation of about 1460 fee.t, although little evidence of this strandline remains. The highest strandline presently common to both takes is 1450 feet, 8 feet below the Big Stony Spillway threshold.
Reede, Roger J., "Geology of southern Nelson County, North Dakota" (1972). Theses and Dissertations. 240.