The Kotcho Formation is a

stratigraphical Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostrat ...

unit of middle

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used ...

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming olde ...

in the

Western Canadian Sedimentary Basin The Western Canadian Sedimentary Basin (WCSB) underlies of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary ...

. It takes the name from

Kotcho Lake Kotcho Lake is a lake in north-eastern British Columbia, Canada. It is located east of Fort Nelson, in the Greater Sierra Oil Field, at an elevation of . It is recognized as a Canadian Important Bird Area. The Kotcho Lake Village Site Provinc ...

and was first described in the ''

Imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imperial, Nebraska * Imperial, Pennsylvania * Imperial, Texas ...

Island River No. 1'' by H.R. Belyea and D.J. McLaren in 1962.Belyea, H.R. and McLaren, D.J., 1962. Upper Devonian formations, southern pan of Northwest Territories, northeastern British Columbia and northwestern Alberta.

Geological Survey of Canada The Geological Survey of Canada (GSC; french: Commission géologique du Canada (CGC)) is a Canadian federal government agency responsible for performing geological surveys of the country, developing Canada's natural resources and protecting the e ...

, Paper 61-29.

Lithology

The Kotcho Formation is composed of green-grey

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especia ...

, locally

bituminous Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

, with thin argillaceous

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

beds or lenses.

Distribution

The Kotcho Formation reaches a maximum thickness of .It is up to thick in the

Fort Nelson Fort Nelson may refer to: Canada *Fort Nelson, British Columbia, a town *Fort Nelson River, British Columbia *Fort Nelson (Manitoba) (1670–1713), an early fur trading post at the mouth of the Nelson River and the first headquarters of the Hudson' ...

area, and thins down southwards, disappearing completely on the northern flank of the

Peace River Arch Peace is a concept of societal friendship and harmony in the absence of hostility and violence. In a social sense, peace is commonly used to mean a lack of conflict (such as war) and freedom from fear of violence between individuals or groups. ...

Relationship to other units

The Kotcho Formation is overlain by the

Exshaw Formation The Exshaw Formation is a stratigraphic unit in the Western Canada Sedimentary Basin. It takes the name from the hamlet of Exshaw, Alberta in the Canadian Rockies, and was first described from outcrops on the banks of Jura Creek north of Exshaw by ...

and conformably overlays the

Tetcho Formation The Tetcho Formation is a stratigraphical unit of Famennian age in the Western Canadian Sedimentary Basin. It takes the name from Tetcho Lake, and was first described in the ''Imperial Island River No. 1'' well (located south of Trout Lake by ...

. To the east, it grades into the upper

Wabamun Group The Wabamun Formation is a stratigraphic unit of Late Devonian (Famennian) age in the Western Canada Sedimentary Basin. It takes the name from Wabamun Lake and was first described in the ''Anglo Canadian Wabamun Lake No. 1'' well (located between ...

carbonate, and to the south-west into the

Palliser Formation The Palliser Formation is a stratigraphic unit of Late Devonian (Famennian) age in the Western Canada Sedimentary Basin. It is a thick sequence of limestone and dolomitic limestone that is present in the Canadian Rockies and foothills of western A ...

. To the east it is replaced by the

Besa River Formation The Besa River Formation is a stratigraphical unit of Devonian age in the Western Canadian Sedimentary Basin. It takes the name from Besa River, a tributary of the Prophet River, and was first described in outcrop near the Muskwa River, in the ...

shale.

References

{{Western Canadian Sedimentary Basin, Fort_Nelson=yes, Liard_River=yes Geologic formations of British Columbia Geologic formations of the Northwest Territories Shale formations Limestone formations of Canada Devonian British Columbia Devonian Northwest Territories