Minnes Group


The Minnes Group, originally named the Minnes Formation, is a geologic unit of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin. It is present in the northern foothills of the Canadian Rockies and the adjacent plains in northeastern British Columbia and west-central Alberta. Its strata include natural gas reservoirs and minor coal deposits. Fossil dinosaur tracks have been described from one of its formations.

Stratigraphy and lithology

The strata of the Minnes Group were originally described as the Minnes Formation which was revised to group status by D.F. Stott. 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.
North:
FormationAgeLithologyMaximum
Thickness		Reference
Bickford FormationEarly Cretaceous interbedded sandstone, siltstone, and mudstone, with minor coal seams
Monach FormationEarly Cretaceous quartzose sandstone, minor coal
Beattie Peaks FormationEarly Cretaceous mudstone, siltstone, argillaceous sandstone
Monteith FormationLate Jurassic to Early Cretaceous quartzose to argillaceous sandstone, with minor conglomerate, siltstone, mudstone, coal

South:
FormationAgeLithologyMaximum
Thickness		Reference
Gorman Creek FormationEarly Cretaceous argillaceous sandstone, siltstone, carbonaceous mudstone, and coal
Monteith Formationlatest Jurassic to Early Cretaceous quartzose to argillaceous sandstone, with minor conglomerate, siltstone, mudstone, coal

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.

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. 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."

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 in the foothills and thins eastward, reaching zero at its erosional edge.

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.

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.