Red River Formation | |
---|---|
Stratigraphic range: | |
Type | Geological formation |
Sub-units | Fort Garry Member Selkirk Member Cat Head Member Dog Head Member |
Underlies | Stony Mountain Formation |
Overlies | Winnipeg Formation |
Thickness | up to 215 metres (710 ft)[1] |
Lithology | |
Primary | limestone, dolomite |
Other | Breccia |
Location | |
Coordinates | 51°56′54″N 98°03′23″W / 51.9482°N 98.0563°W |
Region | WCSB Williston Basin |
Country | ![]() ![]() |
Type section | |
Named for | Red River of the North |
Named by | A.F. Foerste |
Year defined | 1929 |
The Red River Formation is a stratigraphical unit of Late Ordovician age in the Williston Basin.
It takes the name from the Red River of the North, and was first described in outcrop in the Tyndall Stone quarries and along the Red River Valley by A.F. Foerste in 1929.[2][3]
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What is a meander - Geologist describes meandering streams, rivers and oxbow lakes.
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River Meanders: Red River: Oklahoma-Texas Boundary
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Six Days in the Gorge, Pt. IX, "Double Arch"
Transcription
Hello Young People. Entrenched Meander. This is the Yakima River just south of Ellensburg, Washington. Meanders are a feature of old age. These sweeping curves of the river. As rivers age they develop more and more exaggerated meanders. We know this by flying over the Mississippi River system. And we see all stages of meander development back there. Eventually, the meander become so exaggerated that that curve is abandoned and an oxbow lake is formed. And the channel becomes straight again. We can only develop these curves when an area is flat like back east at the Mississippi. And here we've got these exaggerated curves as well which means central Washington used to be flat. But there's a twist. This place isn't flat anymore. This is a deep canyon system. So to understand that twist, how 'bout we get up on that rim and get a big picture view of the Yakima River Canyon. Let's go up there. High up above the Yakima River on the rim of the canyon looking down. There's one of our meanders. We know about meanders. The meanders got established when the area was flat. A subtle curve becoming a more exaggerated curve. But then we froze the position of this meander, and we entrenched it. Entrenched meanders tell us that the land is lifting against the river. The river wasn't up here and was cut down. We're sure that the river has been down there for millions of years and the land has been lifting against the meander - against the river. The river's been cutting, matching an uplift rate of the bedrock. Basalt layer after basalt layer exposing themselves on the way up. The future of this meander is not more exaggerated meander. Development of an oxbow lake. Instead, the future of this curve is more cutting. Because the uplift continues here in central Washington. Entrenched Meanders. Just south of Ellensburg, Washington.
Lithology
Subdivisions
The Red River Formation is composed of the following subdivisions from top to base: [1]
- Fort Garry Member: crystalline and micritic dolomite with an argillaceous dolomite breccia in the middle
- Selkirk Member: fossiliferous, dolomitic limestone
- Cat Head Member: cherty dolomite, becoming calcareous to the south
- Dog Head Member: fossiliferous dolomitic limestone
Distribution
The Red River Formation reaches a maximum thickness of 215 metres (710 ft) in the center of the Williston Basin. At the along the Manitoba outcrop belt, it is 150 metres (490 ft) thick and thins out northwards.[1]
Relationship to other units
The Red River Formation is slightly unconformably overlain by the Stony Mountain Formation and sharply overlays the Winnipeg Formation in Manitoba, the Deadwood Formation in western Saskatchewan and the Canadian Shield in northern Manitoba.[1]
The lower Red River Formation is equivalent to the Yeoman Formation, while the Fort Garry Member correlates with the Herald Formation.
References
- ^ a b c d Lexicon of Canadian Geologic Units. "Formation". Archived from the original on 2009-04-16. Retrieved 2010-02-01.
- ^ Foerste, A.F., 1929. The Ordovician and Silurian of the American arctic and sub-arctic regions. Denison Univ. Sci. Lab J., v. 24, p. 27-79.
- ^ Foerste, A.F., 1929b. The cephalopods of the Red River Formation of southern Manitoba. Denison Univ. Sci. Lab J., v. 24, p. 129-235.
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