At the Highway 3 Roadcut showing, phosphorite, phosphatic shale, shale and limestone of the basal Jurassic Fernie Group unconformably overlie siltstone and shale of the Triassic Sulphur Mountain Formation (Spray River Group). A 1 metre thick pelletal phosphorite bed containing 15.75 per cent P2O5 immediately overlies a 0.7 metre thick shale bed of Triassic age (Open File 1987-16). Overlying the phosphorite is a 1.9 metre thick phosphatic shale unit containing 3.10 per cent P2O5.