A band of limestone of the Middle Devonian Dunedin Formation outcrops on the east arm of Williston Lake (formerly the Peace River), 6 kilometres east of the mouth of Clearwater Creek, and continues southeastward for 25 kilometres. Exposed widths vary up to 2.5 kilometres. The southern half of the band is folded about the crest of a northwest trending syncline.

The band is comprised of limestone and argillaceous limestone that is locally replaced by massive dolomite. Calcareous shale and minor sandstone are also present.