Distribution:

North of Raspberry Pass (Souther, 1988).

Lithology:

The Tenchen Member embraces all the products of Nido volcanism that were erupted north of the Armadillo Highlands. Flows and pyroclastic deposits of Tenchen basalt are exposed on both the east and west sides of Mount Edziza north of Raspberry Pass. On the east, steep-walled valleys cut across the principal areas of Tenchen volcanism, exposing the proximal flows and thick piles of tephra as well as feeder dykes, necks and subvolcanism intrusions in the source region. Farther west, along Mess Creek Escarpment and in the canyon of Elwyn Creek the thin distal edge of the Tenchen pile is exposed in tiers of brown-weathering, columnar flows. The western exposures include the eroded remnants of at least three major eruptive centres, Alpha peak, Beta peak and Gamma peak, as well as isolated lenses of tephra and groups of flows from an unknown number of satellitic vents which have since been destroyed by erosion or buried beneath younger flows (Souther, 1992).

Relationship:

The Tenchen Member is a unit of the Nido Formation (Mount Edziza Complex). North of Armadillo Highlands most of the Tenchen basalt rests on the Armadillo Formation or on fluvial gravel carrying clasts of Armadillo rhyolite and trachyte. However, distal flows on the extreme northern edge of the pile extend beyond the apron of Armadillo colluvium and rest directly on pre-Tertiary basement. The upper contact is defined by the Pyramid rhyolite which overlies the Tenchen basalt along the eastern edge of Mount Edziza (Souther, 1992).

Other Citations:

Mihalynuk et al., 1996.

References:

Mihalynuk, M., Bellefontaine, K., Brown, D., Logan, J., Nelson, J., Legun, A. and Diakow, L., 1996. Digital Geology, NW British Columbia (94/E, L, M; 104/F, G, H, I, J, K, L, M, N, O, P; 114/I, O, P); Ministry of Energy, Mines and Petroleum Resources, Open File 1996-11.

Souther, J.G., 1988. Geology, Mount Edziza volcanic complex, British Columbia; Geological Survey of Canada, "A" Series Map no. 1623A, 2 sheets.

Souther, J.G., 1992. The Late Cenozoic Mount Edziza Volcanic Complex, British Columbia; Geological Survey of Canada, Memoir 420, 329 p.