At the Deer Bay occurrence, a fault-bounded band of Pennsylvanian to Permian limestone (Buttle Lake Group) outcrops a kilometre north of Deer Bay at the head of Tofino Inlet, 58 kilo- metres west of Port Alberni. The band correlates with the Azure Lake Formation of the Buttle Lake uplift and the Mount Mark Formation of the Cowichan uplift, both units of the new Buttle Lake Group. See Cream 1,3 (092F 220) for a description of the revised stratigraphy nomenclature.

The band, up to 250 metres wide, strikes 091 degrees for 2000 metres and dips 60 degrees north. The unit is underlain by volcanic breccia, tuff and argillite and is unconformably overlain by basalts of the Upper Triassic Vancouver Group, Karmutsen Formation.