Minnes Group
The Minnes Group, originally named the Minnes Formation,[1] is a geologic unit of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin.[2] It is present in the northern foothills of the Canadian Rockies and the adjacent plains in northeastern British Columbia and west-central Alberta.[3] Its strata include natural gas reservoirs and minor coal deposits.[4] Fossil dinosaur tracks have been described from one of its formations.[5]
| Minnes Group | |
|---|---|
Stratigraphic range: | |
| Type | Group |
| Sub-units | Gorman Creek Formation Bickford Formation Monach Formation Beattie Peaks Formation Monteith Formation |
| Underlies | Cadomin Formation |
| Overlies | Fernie Formation |
| Thickness | maximum 2,100 m (6,890 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Siltstone, mudstone, coal |
| Location | |
| Coordinates | 54.1625°N 120.0667°W |
| Region |  British Columbia Alberta |
| Country | .svg.png.webp){kind=small} Canada |
| Type section | |
| Named for | Mount Minnes, British Columbia |
| Named by | W.H. Ziegler and S.A.J. Pocock[1] |
Stratigraphy and lithology
The strata of the Minnes Group were originally described as the Minnes Formation[1] which was revised to group status by D.F. Stott.[4] Stott subdivided the group into four formations in the north as shown below. South of the Pine River the upper three formations are not readily divisible and those beds are included in the Gorman Creek Formation.[4][3]
North:
| Formation | Age | Lithology | Maximum Thickness | Reference |
|---|---|---|---|---|
| Bickford Formation | Early Cretaceous (Valanginian) | interbedded sandstone, siltstone, and mudstone, with minor coal seams | 400 m (1,310 ft) | [4] |
| Monach Formation | Early Cretaceous (Valanginian) | quartzose sandstone, minor coal | 350 m (1,150 ft) | [4] |
| Beattie Peaks Formation | Early Cretaceous (Valanginian) | mudstone, siltstone, argillaceous sandstone | 460 m (1,510 ft) | [4] |
| Monteith Formation | Late Jurassic (Tithonian) to Early Cretaceous (Berriasian) | quartzose to argillaceous sandstone, with minor conglomerate, siltstone, mudstone, coal | 600 m (1,970 ft) | [4] |
South:
| Formation | Age | Lithology | Maximum Thickness | Reference |
|---|---|---|---|---|
| Gorman Creek Formation | Early Cretaceous (Valanginian) | argillaceous sandstone, siltstone, carbonaceous mudstone, and coal | 1,200 m (3,940 ft) | [4] |
| Monteith Formation | latest Jurassic (Tithonian) to Early Cretaceous (Berriasian) | quartzose to argillaceous sandstone, with minor conglomerate, siltstone, mudstone, coal | 600 m (1,970 ft) | [4] |
Environment of deposition
The formations of the Minnes Group were deposited in marine and nonmarine environments within and adjacent to the Western Interior Seaway. Depositional settings ranged from shallow marine to shoreline, coastal plain, deltaic, river channel, floodplain, and swamp environments.[4]
Paleontology and age
The age of the Minnes Group strata has been determined from their fossil fauna, primarily species of the bivalve Buchia. Ammonites, plant fossils, palynomorphs, and microfossils have also been described from the Minnes Group.[4] Dinosaur trackways are present on bedding surfaces in the Gorman Creek Formation of the Minnes Group near the Narraway River:
"More than 200 fossil footprints are preserved in at least 8 trackways... The majority of the footprints were made by small theropods, but the most dramatic trackway was made by a large biped whose feet were more than a half meter in length."[6]
Thickness and distribution
The Minnes Group can be seen in outcrops in the northern foothills of the Canadian Rockies and is present beneath the adjacent plains from the Prophet River in northeastern British Columbia to the Berland River in west-central Alberta. It reaches a maximum thickness of 1,200 m (3,940 ft) in the foothills and thins eastward, reaching zero at its erosional edge.[3]
Relationship to other units
The Minnes Group was deposited conformably over the marine shales of the Fernie Formation, and was eroded prior to the deposition of the Cadomin Formation of the Bullhead Group which unconformably overlies it. The Minnes strata grade into those of the Nikanassin Formation to the south in Alberta.[2][3]
Economic Resources
The Minnes Group contains natural gas reservoirs in the subsurface of the Peace River Plains and Deep Basin areas, where it is sometimes reported as "Nikanassin Formation". Coal seams and carbonaceous shales, which may have been the source for much of the gas, are also present in the Minnes Group, but none of the coal deposits have been found to be economically mineable.[4]
References
- Ziegler, W.H. and Pocock, S.A.J. 1960. The Minnes Formation. In: Second Annual Field Trip Guidebook, Rock Lake, August 1960. Edmonton Geological Society, p. 43-71.
- Mossop, G.D. and Shetsen, I. (compilers), Canadian Society of Petroleum Geologists and Alberta Geological Survey (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 18: Jurassic and Lowermost Cretaceous strata of the Western Canada Sedimentary Basin". Retrieved 2016-06-20.
{{cite web}}: CS1 maint: multiple names: authors list (link) - Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. ISBN 0-920230-23-7.
- Stott, D.F. 1998. Fernie Formation and Minnes Group (Jurassic and lowermost Cretaceous), northern Rocky Mountain foothills, Alberta and British Columbia. Geological Survey of Canada, Bulletin 516.
- Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.): The Dinosauria, 2nd ed., "Dinosaur distribution," pp. 517-607. Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.
- Currie, P.J. 1991. Dinosaur footprints of western Canada. In: Dinosaur tracks and traces, D.D. Gillette and M. Lockley (eds.), p. 294. Cambridge University Press, ISBN 9780521407885, 476 p.