A band of Upper Triassic Vancouver Group, Quatsino Formation limestone, up to 1500 metres wide, trends north-northwest for 8 kilo- metres, crossing Greenstone Creek 4.8 kilometres above its mouth, northwest of Upper Campbell Lake. The northeastward dipping limestone bed is bounded to the west by basalts of the Upper Triassic Vancouver Group, Karmutsen Formation and to the east by Lower Jurassic Bonanza Group volcanics and sediments. To the south, the band is truncated by a northeast trending fault.