A 500-metre-wide band of limestone of the Upper Triassic Quatsino Formation (Vancouver Group) trends west-northwest from the northeast end of Quatse Lake for 3.75 kilometres, 5 kilometres northeast of Coal Harbour and 10 kilometres southwest of Port Hardy. The limestone becomes overlain to the south by argillite of the Upper Triassic Parsons Bay Formation (Vancouver Group), while underlying basaltic volcanics of the Upper Triassic Karmutsen Formation (Vancouver Group) outcrop to the north.

Various exposures along a 300-metre section of a logging road near the northeast end of Quatse Lake reveal fine grained, light to dark grey, streaked limestone that strikes 115 degrees and dips 45 degrees south. A few scattered lenses of chert occur in the limestone. These become more common to the west. A sample of chips collected in 0.6 metre intervals along a 21-metre-long road cut contained 54.69 per cent CaO, 0.40 per cent MgO, 1.36 per cent insolubles, 0.33 per cent R2O3, 0.14 per cent Fe2O3, 0.039 per cent MnO, 0.05 per cent P2O5, 0.03 per cent sulphur, 43.11 per cent ignition loss and 0.18 per cent water (Minister of Mines Annual Report 1968, p. 318, Sample 2).