Landforms of British Columbia 1976 - Department of Geography

The northward movement of ice across the plateau is shown by the drumlinlike
forms along the Sheslay Valley north of Sheslay and northeast and east of
Level Mountain.
[References : “ Stikine River Area,” Geol. Surv., Canada, Map g-1957;
Watson, K. Dep., and Mathews, W. H., “ The Tuya-Teslin Area, Northern British
Columbia,” B.C. Dept. of Mines, Bull. No. 19, 1944.1
[Photographs: B.C. 698:36, 44, 76.1
Tanzilla Plateau
The Tanzilla Plateau lies east of the Tuya River, north of the S’tikine River,
and west of the Cassiar Mountains. The plateau is a partly dissected erosion
surface (see Plate XIXA), which reaches heights of 6,200 feet west of Dease Lake
and of 6,348 feet at Snow Peak. The erosion surface was one of low relief and
was formed on closely folded sedimentary and volcanic rocks. The plateau is
partly dissected by tributaries of the Dease River flowing northward to the Liard
and by the Tuya, Tanzilla, and Stikine Rivers. The elevation of Dease Lake and
the head of Tanzilla River at about 2,500 feet creates a maximum relief of about
3,850 feet at Snow Peak.
The Tanzilla Plateau represents a transition between the thoroughly dissected
Cassiar Mountains on the east and the little dissected Kawdy and Nahlin Plateaus
to the west. It is an area of widely flaring valleys, and rounded ridges and peaks
passing eastward into the serrate peaks and higher uplands of the Cassiar Mountains.
The high peaks west of Dease Lake extending from Mount Coulahan (6,191
feet) southward to Snow Peak (6,348 feet) constitute the French Range.
Between the Tanzilla River and Stikine River is the Hotailuh Range, whose cirqued
peaks reach 6,100 feet at Thenatlodi Mountain and 6,256 feet at a nearby unnamed
mountain.
[References: Kerr, F. A., “ Dease Lake Area,” GeoZ. SW-V., Canada, Sum.
Rept., 1925, Pt. A, pp. 75-99; “ Stikine River Area,” Geol. Surv., Canada, Map
g-1957; Gabrielse, H., Souther, J. G., and Roots, E. F., “ Dease Lake,” Geol.
Surv., Canada, Map 21-1962.1
[Photographs: B.C. 695:73, 81.1
Klastline Plateau
The Klastline Plateau (see Plate XVIII) lies south of the Stikine River and is
bounded on the west by the Tahltan Highland and on the south by the Klappan
Range of the Skeena Mountains. The plateau is separated from the Spatsizi Plateau
to the east at the constriction between the Eaglenest Range and Three Sisters
Range by a line running northward from Mount Brock (6,971 feet).
The rolling upland surface of the Klastline Plateau represents the late Tertiary
erosion surface, which is so widespread in the Stikine Plateau. The surface was
formed by late Tertiary time on Paheozoic and Mesozoic sedimentary and volcanic
rocks, with only a few small intrusive stocks known. Much of the plateau surface
is unwooded or is only sparsely covered with clumps of spruce and willow.
The plateau lies above 5,000 feet elevation and rises to peaks over 6,000 feet.
It has been incised to below 2,500 feet by Mess Creek, to 2,654 feet in the valley
of Kinaskan Lake, below 3,000 feet by Klappan River, and below 2,500 feet by
the Stikine River.
The Klastline Plateau passes by transition into the Klappan and Eaglenest
Ranges on the southeast and east (see Plate XIXB), where some large, gently
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