At the Summit Lake showing, an approximately 3 metre thick sandstone of Permian age overlies Kananaskis or possibly Tunnel Mountain formations strata of the Pennsylvanian Spray Lakes Group. Within the sandstone is a nodular phosphate horizon approximately 1 metre thick. Nodules are 2 to 5 centimetres in size and contain 25.7 per cent P2O5. A grab sample of siltstone with abundant nodules contained 14.5 per cent P2O5 (Open File 1987-16).