Banff Formation, Geological formation in Alberta, Canada.

The Banff Formation is a Devonian stratigraphic unit of the Western Canada Sedimentary Basin, named after Banff, Alberta. It consists of shale and marlstone at the base, chert and limestone in the middle, and sandstone, siltstone and shale at the top. In the Rocky Mountains its thickness is about 400 feet (120 m), and it ranges in age from late Famennian to Tournaisian.

E.M. Kindle first described the Banff Formation in 1924 on the north-west slope of Mount Rundle, near the town of Banff, Alberta. The formation takes its name from that town. Its age spans the late Famennian to Tournaisian stages of the Devonian and Carboniferous periods.

The formation provides valuable scientific data for paleoenvironmental studies and serves as a natural laboratory for geologists and students studying carbonate and shale stratigraphy in the Canadian Rockies.

Outcrops of the Banff Formation are accessible around Mount Rundle and along road cuts, offering direct observation opportunities for geological research and educational purposes in Alberta's mountainous regions.

The formation contains distinct lithological transitions from basal shale and marlstone to middle limestone and chert layers, ending with upper sandstone and shale that illustrate ancient sea level changes.