A 46 to 60 metre thick bed of grey argillaceous limestone of the Permian to Pennsylvanian Nanoose Formation (Sicker Group) possibly correlative with the Fourth Lake Formation (Buttle Lake Group) out- crops on the North and South Ballenas Islands, 25 kilometres north- west of Nanaimo. The limestone contains crinoids, brachiopods, corals and fusilinids and is underlain by brown argillite and grey- wacke, which grade downward into green and grey bedded tuffs. The entire sequence is folded into a northwest plunging syncline. The limestone is partially silicified and displays a well developed slaty cleavage. In places the limestone contains up to 10 per cent albite grains.