A 120 to 900 metre wide band of limestone of the Silurian (?) to Carboniferous "Pend d'Oreille Sequence" trends east-northeast along the north side of the Pend d'Oreille River for 7.9 kilometres. The band is bounded to the north and south by argillite, slate and phyllite. The entire sequence lies in fault contact with andesite, basalt, tuff and breccia of the Lower Jurassic Elise Formation to the north. The limestone member dips approximately 50 degrees south. The Pend d'Oreille Sequence is correlated to the Attwood Formation of the Greenwood area to the west.

The carbonate is generally composed of massive, light grey, white to light blue weathering limestone. The limestone is commonly siliceous. In places, buff weathering dolomite masses, up to a hundred metres in diameter are present. A sample of chips collected at random over a 4 square metre area along the limestone bluffs near the Nelway-Waneta road, 317 metres west of Charbonneau Creek contained 52.90 per cent CaO, 2.36 per cent MgO and 0.84 per cent insolubles (J.T. Fyles, 1956, Sample 9230). A similar sample 712 metres east of the creek contained 53.80 per cent CaO, 1.83 per cent MgO and 0.56 per cent insolubles (J.T. Fyles, 1956, Sample 9231).