Lynx Group
Stratigraphic unit in Canada
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The Lynx Group is a stratigraphic unit of Late Cambrian (Dresbachian) age in the Western Canada Sedimentary Basin.[2] It is present in the Canadian Rockies of Alberta and British Columbia. It was originally described as the Lynx Formation by Charles Doolittle Walcott in 1913, based on and named for outcrops on the slopes of Lynx Mountain on the continental divide east of Mount Robson. It was subdivided into five formations and elevated to group status by J.D. Aitken and R.G. Greggs in 1967.[3] The name Lynx Formation continues to be used in areas where some or all of the subdivisions cannot be distinguished. All of the formations in the Lynx Group include fossil trilobites and some contain the stromatolite Collenia.[4]
| Lynx Group | |
|---|---|
| Stratigraphic range: | |
| Type | Formation or Group |
| Sub-units | Mistaya Formation Bison Creek Formation Lyell Formation Sullivan Formation Waterfowl Formation |
| Underlies | Survey Peak Formation |
| Overlies | Arctomys Formation |
| Thickness | up to 1,220 metres (4,000 ft)[1] |
| Lithology | |
| Primary | Carbonate rocks |
| Other | Shale |
| Location | |
| Coordinates | 53.1407°N 119.0492°W |
| Region | Canadian Rockies |
| Country | Canada |
| Type section | |
| Named for | Lynx Mountain |
| Named by | C.D. Walcott, 1913 |
Lithology and deposition
The Lynx Group is composed alternating zones of carbonate rocks, most of which are dolomitic, and shales.[1][4] It was deposited in shallow marine environments along the western margin of the North American Craton during Late Cambrian time.[2][5] In many areas it is subdivided into the five formations listed below.[4][6]
Subdivisions
Upper Lynx Group
| Formation | Lithology | Max. Thickness | Reference |
|---|---|---|---|
| Mistaya Formation | carbonate rocks, minor cherty layers | 158 m (520 ft) | [4] |
| Bison Creek Formation | green and grey shales, argillaceous limestone | 203 m (670 ft) | [4] |
| Lyell Formation | massive cliff-forming carbonate rocks | 519 m (1,700 ft) | [4] |
Lower Lynx Group
| Formation | Lithology | Max. Thickness | Reference |
|---|---|---|---|
| Sullivan Formation | grey, green, and brown shales, argillaceous limestone | 424 m (1,390 ft) | [4] |
| Waterfowl Formation | cliff-forming carbonate rocks, minor siltstone and sandstone | 183 m (600 ft) | [4] |
Distribution
The Lynx Group is present in the Canadian Rockies of Alberta and British Columbia. It is typically between 1068-1220 metres (3500-400 feet) thick in the front and main ranges. It extends as far north as the Monkman Pass area of British Columbia.[4]
Relationship to other units
The Lynx Group overlies the Arctomys Formation and the contact is gradational. It is overlain by the Survey Peak Formation and the contact is concordant but abrupt.[4]