Type Locality:

On the shoulder of a ridge at 58 deg 48'N, 125 deg 37'W, just east of a deep canyon about 3.2 km (2 mi) northwest of the Toad River bridge on the Alaska Highway in British Columbia.

Distribution:

The unit ranges from 138 m (452 ft) thick through 295 m (969 ft) thick at the type locality to 612 m (2,008 ft) thick at Gibault Creek (west of Fort St. John). It is 344 m (1160 ft) south of the Liard River on the north and 290 m (950 ft) at the south end of the Caribou Range. It is present in a linear belt extending from southwest of Fort St. John, at about 55° N, 123° 15'W, extending northwestward into southern Yukon at about 126 deg W and in the Caribou Range (125° 35'W). To the east of the mountains the Nonda is absent in the subsurface, with Devonian rocks resting on mid-Cambrian and older strata. In the Coal River map area of the Yukon the formation is probably less that 305 m (1,000 ft) thick and is present on Coal River, Otter River, Spruce Creek and Siwash Creek.

Lithology:

Dominantly siliceous dolomite with chert nodules, with lesser amounts of quartzite, quartzitic sandstone and limestone near the base. The base of the formation is southward thinning quartzite and quartzitic sandstone north of Keily Creek; south of this locality it is a dark dolomite. Quartzites and quartzitic sandstones are most abundant at the base of the formation; the upper part is dominantly siliceous dolomite with chert nodules. In the southern Yukon the basal beds of the Nonda Formation consist of very well-bedded, homogeneous, fine-grained, strongly cross-bedded, buff, dolomitic siltstone and sandstone 30+ m (100+ ft) thick. This is overlain by medium- to thick-bedded, flaggy, locally with lenses and layers of black chert, medium- to dark grey, fine-grained, commonly fetid dolomites, probably less than 305 m (1,000 ft) thick.

Relationship:

The Nonda Formation unconformably overlies Precambrian or Cambrian and Ordovician strata, and is unconformably overlain by the Muncho-McConnell Formation. The contact between Cambrian quartzites and quartzites of the Nonda Formation is difficult to recognize. The unit was referred to as the Ronning Formation in northern British Columbia by Laudon et al. (1949). In the Yukon the Nonda Formation unconformably overlies unnamed ?Middle Cambrian to Lower Ordovician strata and the Sunblood Formation and is overlain by unnamed Silurian to Middle Devonian dolomites and limestone.

References:

Laudon, L. R., Deidrick, E., Grey, C.E., Hamilton, W.B., McBee, W.D., Spreng, A.C., and Stoneburner, R., 1949. Devonian and Mississippian stratigraphy, Wapiti Lake area, British Columbia, Canada; American Association of Petroleum Geologists (AAPG), AAPG Bulletin, v. 33, p. 1502-1552.

Norford, B.S., Gabrielse, H., and Taylor, G.C., 1966. Stratigraphy of Silurian carbonate rocks of the Rocky Mountains, northern British Columbia; Canadian Society of Petroleum Geologists, Bulletin of Canadian Petroleum Geology, v. 14, p. 504-519.