Kotcho Formation

The Kotcho Formation is a stratigraphic unit of middle Famennian age in the Western Canadian Sedimentary Basin.

Kotcho Formation
Stratigraphic range: Middle Famennian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Underlies	Exshaw Formation
Overlies	Tetcho Formation
Thickness	up to 210.9 metres (690 ft)[1]
Lithology
Primary	Shale
Other	Limestone
Location
Coordinates	60.15500°N 121.30444°W / 60.15500; -121.30444 (Kotcho Formation)
Region	British Columbia, Northwest Territories
Country	Canada
Type section
Named for	Kotcho Lake
Named by	H.R. Belyea, D.J. McLaren, 1962

It takes the name from Kotcho Lake and was first described in the Imperial Island River No. 1 by H.R. Belyea and D.J. McLaren in 1962.^[2]

Lithology

The Kotcho Formation is composed of green-grey shale, locally bituminous, with thin argillaceous limestone beds or lenses.^[1]

Distribution

The Kotcho Formation reaches a maximum thickness of 210.9 metres (690 ft).^[1]It is up to 30 metres (100 ft) thick in the Fort Nelson area, and thins down southwards, disappearing completely on the northern flank of the Peace River Arch.

Relationship to other units

The Kotcho Formation is overlain by the Exshaw Formation and conformably overlays the Tetcho Formation.^[1]

To the east, it grades into the upper Wabamun Group carbonate, and to the south-west into the Palliser Formation. To the east it is replaced by the Besa River Formation shale.