A belt of Permian limestone extends discontinuously from the headwaters of Sphaler Creek northwestward along the South Scud River to Ambition Mountain for 50 kilometres. The limestone is also exposed for 15 kilometres northwestward along the Scud River. The unit is estimated to be 800 to 1000 metres thick. The limestone has undergone extensive folding and faulting.

The lower 75 metres of the formation is comprised of dark grey, thin bedded limestone interbedded with pyritic argillite, which grades upward into 350 metres of pale grey to buff coloured, thin to medium bedded limestone intercalated with amorphous chert. This is followed by a hundred metres of tan to very light grey weathering bryozoan rich limestone that is overlain by at least 300 metres of massive to bedded, white to buff, bioclastic limestone with minor argillite and tuff. This purer limestone is contaminated with some siliceous layers and pods. The entire section is overlain by shales of Middle Triassic age.