Glacial Lake Souris
Encyclopedia
The Glacial Lake Souris occupied the basin of the Souris River
Souris River
The Souris River or Mouse River is a river in central North America. It is about 700 km in length and drains about . It rises in the Yellow Grass Marshes north of Weyburn, Saskatchewan...

 from the most southern portion of this river's loop in North Dakota
North Dakota
North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....

 to its elbow in Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...

, where it turned sharply northward and passed through the Tiger Hills. The length of Lake Souris was about 170 miles, from latitude 48°
48th parallel north
The 48th parallel north is a circle of latitude that is 48 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....

 to latitude 50°35', and its maximum width, north of Turtle Mountain
Turtle Mountain (plateau)
Turtle Mountain, or the Turtle Mountains, is an area in central North America, in the north-central portion of the U.S. state of North Dakota and southwestern portion of the Canadian province of Manitoba...

, was nearly 70 miles. It was situated near the far southeast corner of the large glacial Lake Agassiz
Lake Agassiz
Lake Agassiz was an immense glacial lake located in the center of North America. Fed by glacial runoff at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined, and it held more water than contained by all lakes in the world today.-Conception:First...

, separated from it by another small glacial body, Glacial Lake Hind.

North of the Souris basin, an arm of this lake extended along the Assiniboine River
Assiniboine River
The Assiniboine River is a river that runs through the prairies of Western Canada in Saskatchewan and Manitoba. It is a tributary of the Red River. The Assiniboine is a typical meandering river with a single main channel embanked within a flat, shallow valley in some places and a steep valley in...

 from Griswold and Oak Lake
Oak Lake, Manitoba
Oak Lake, Manitoba is a town in the south-western "Westman region" of Manitoba, Canada. It is located west of Brandon along the Trans-Canada Highway....

 to some distance above the mouth of the Qu'Appelle River
Qu'Appelle River
The Qu'Appelle River is a Canadian river that flows 430 km east from Lake Diefenbaker in southwestern Saskatchewan to join the Assiniboine River in Manitoba, just south of Lake of the Prairies, near the village of St. Lazare....

 in Saskatchewan; and the main body of the lake was deeply indented on the east by the high oval area of Turtle Mountain, and forms, with overlying drift deposits, the massive terrace of the Coteau du Missouri
Coteau du Missouri
The Coteau du Missouri, or Missouri Plateau, is a large plateau that stretches along the eastern side of the valley of the Missouri River in central North Dakota and north-central South Dakota in the United States...

 on the west.

The mouth of Lake Souris, where it first outflowed to Lake Agassiz
Lake Agassiz
Lake Agassiz was an immense glacial lake located in the center of North America. Fed by glacial runoff at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined, and it held more water than contained by all lakes in the world today.-Conception:First...

 by the Big Coulée River and the Sheyenne River
Sheyenne River
The Sheyenne River is one of the major tributaries of the Red River of the North, meandering across eastern North Dakota.The river begins about north of McClusky, North Dakota, and flows generally eastward before turning south near McVille. The southerly flow of the river continues through Griggs...

, was approximately 1,600 to 1,500 feet above the present sea-level, being gradually cut down about 100 feet by the stream. Because of subsequent changes which are known to have taken place in the relative elevation of the land and water surfaces in this district, the shore-line of the northern part of the lake at the end of its time of outflow to the Sheyenne would now have an elevation of about 1,600 feet at Langs Valley. Therefore, when its channel of discharge was transferred to the new course by Pelican Lake
Pelican Lake (Manitoba)
Pelican Lake is the largest navigable lake in south western Manitoba, Canada. It is 14 miles long and 1 1/2 miles wide. The lake is suitable for sailing, water activities, cottagers and home owners. The town of Ninette is at the north end of the lake. Ninette is less than a one hour drive to...

 and along the Pembina River
Pembina River
Pembina River can refer to:*Pembina River , a river in southern Manitoba, Canada and northern North Dakota, United States*Pembina River , a river in central Alberta, Canada...

, Lake Souris was suddenly lowered about 125 feet to the level of the top of the bluffs of Langs Valley, and a further lowering of 110 feet was afterward effected by the gradual erosion of this valley. The lake was wholly drained by this outlet.

The "North Dakota Gold Rush" and Lake Souris

Since the early 1900s, gold has also been known to occur in the sand and gravel deposits associated with glacial Lake Souris in McHenry County
McHenry County, North Dakota
-National protected areas:*Cottonwood Lake National Wildlife Refuge*J. Clark Salyer National Wildlife Refuge *Wintering River National Wildlife Refuge-Demographics:...

, Bottineau County, and Pierce County
Pierce County, North Dakota
-National protected area:*Buffalo Lake National Wildlife Refuge-Demographics:As of the census of 2000, there were 4,675 people, 1,964 households, and 1,276 families residing in the county. The population density was 5 people per square mile . There were 2,269 housing units at an average density...

 in North Dakota. The first discovery of gold there likely dates to May, 1908, when mining claims were recorded about three miles east of the town of Denbigh in McHenry County.

Later in 1908, the Eldorado Gold Mining Company was organized to "cooperate and purchase a dredge
Dredge
Dredging is an excavation activity or operation usually carried out at least partly underwater, in shallow seas or fresh water areas with the purpose of gathering up bottom sediments and disposing of them at a different location...

 or mining boat of sufficient capacity to do the work in the best possible manner." Several other similar companies were formed at about the same time. However, the search for gold was ultimately fruitless, and the companies soon closed and exited the region.

The gold-bearing deposits associated with the glacial Lake Souris sediments in McHenry County were "rediscovered" in 1931 when reports from Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

 claimed that gold nuggets had been taken from the crops of turkeys grown near Denbigh. Individuals and organizations filed placer
Placer mining
Placer mining is the mining of alluvial deposits for minerals. This may be done by open-pit or by various surface excavating equipment or tunneling equipment....

 claims and took mining leases until virtually all of the ground over a large area surrounding Denbigh and Towner
Towner, North Dakota
As of the census of 2000, there were 574 people, 295 households, and 158 families residing in the city. The population density was 694.0 people per square mile . There were 335 housing units at an average density of 405.0 per square mile . The racial makeup of the city was 97.91% White, 0.35%...

 was covered.

The gold contained in the Lake Souris gravel deposits was apparently derived from rocks of the Canadian Shield
Canadian Shield
The Canadian Shield, also called the Laurentian Plateau, or Bouclier Canadien , is a vast geological shield covered by a thin layer of soil that forms the nucleus of the North American or Laurentia craton. It is an area mostly composed of igneous rock which relates to its long volcanic history...

 to the north. The glaciers that transported the gold to north-central North Dakota flowed over what are today the Gods Lake
Gods Lake
Gods Lake is a lake in northeastern Manitoba in Canada. The lake covers an area of , making it the 7th largest lake in the province. It lies north of Island Lake at an elevation of , approximately east of Thompson, Manitoba. It has a perimeter of . The First Nations communities of Gods Lake, Gods...

, Flin Flon
Flin Flon
Flin Flon is a Canadian mining city located on the border of Manitoba and Saskatchewan, with the majority of the city located within Manitoba.- Founding :...

, and Lac La Ronge
Lac la Ronge
Lac la Ronge is a glacial lake in Saskatchewan, Canada. It is the fifth largest lake in the province.It is approximately 250 km north of Prince Albert, on the edge of the Canadian Shield. La Ronge, Air Ronge and the Lac La Ronge First Nation are on the west shore. The lake is a popular...

 mining districts of northern Manitoba and Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

. This part of the Canadian Shield is situated about 500 miles (804.7 km) straight north of the Denbigh area and, based on flow directions believed to have occurred during the glacial ice, it is in a likely position to serve as a source for the gold. After glacial sediments were dropped by melting ice, they were washed by streams of meltwater, which helped to concentrate the gold by removing the lighter weight material. Gold-bearing sediments were deposited on the floor of Lake Souris as undercurrent fans at the mouths of the Souris and other rivers.
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