Type Locality:

The type area is near Nakina Lake, which lies within the western margin of the largest area of such basalt in the Atlin Terrane (southwestern facies belt) (Monger, 1975).

Distribution:

The formation is exposed elsewhere in the southwestern facies belt near Mount O'Keefe, Sentinel Mountain and Tagish Lake. The thickness of the formation is not known but is probably in the order of several thousand feet (Monger, 1975).

Lithology:

The lithology is very uniform. Commonly it is tan or brown to green weathering, grey green or rarely maroon, very fine grained altered basalt, in places with small chlorite amygdales and calcite veins. The rocks are generally massive and the only planar structures recognizable are fractures and faults with slickensided surfaces. Other less common rock types are diabase and fine-grained basalt porphyry with small feldspar phenocrysts and very rarely, fine-grained gabbro, basaltic flow breccia and tuff (Monger, 1975).

Relationship:

Part of the Cache Creek Complex. The Nakina Formation is overlain by and locally intercalated with the Kedahda Formation (Nassichuk, 1977). It has been suggested that the Nakina Formation rocks form the base of the Cache Creek stratigraphic succession (Monger, 1975). These rocks are directly correlative with the Conrad Member of Hart and Pelletier (1989a). In the Tagish area, a consistent stratigraphic position is not apparent (Mihalynuk, 1999).

History:

Massive altered basalt of probable Mississippian age was designated Nakina Formation by Monger (1975).

References:

Hart, C.J.R. and Pelletier, K.S., 1989a. Geology of the Carcross (105D/2) and part of Robinson (105D/7) map areas; Indian and Northern Affairs Canada: Yukon Region, Open Fie 1989-1.

Mihalynuk, M.G., 1999. Geology and mineral resources of the Tagish Lake area (NTS 104M/8,9,10E, 15 and 104N/12W), northwestern British Columbia; British Columbia, Geological Survey Branch, Bulletin 105.

Monger, J.W.H., 1975. Upper Paleozoic rocks of the Atlin Terrane, northwestern British Columbia and south-central Yukon; Geological Survey of Canada, Paper 74-47, 63 p.

Nassichuk, W.W., 1977. Upper Permian Ammonoids from the Cache Creek Group in Western Canada; Journal of Paleontology, Vol. 51, No. 3 (May, 1977), pp. 557-590.