Landforms of British Columbia 1976 - Department of Geography

The plateau is a late Tertiary erosion surface of low relief extending across
Paleozoic and Mesozoic sedimentary and volcanic rocks intruded by granites.
The surface has been elevated, and has been dissected by the major streams,
Within the plateau large areas of flat to gently sloping upland lie at and below
5,000 feet. This level serves to differentiate the plateau from the highlands to the
west, in which the amount of undissected upland becomes progressively less as it
rises to higher elevations.
The Taku Plateau is very largely drained by the Taku River and its tributaries
flowing westward into the Pacific Ocean. The gradients of these rivers are very
much steeper than those of streams tributary to the Yukon River that drain the
Teslin Plateau on the north. As a consequence, the Nakina River has been able
to capture streams that formerly flowed northward across the Teslin Plateau into
Atlin or Teslin Lake.* The Nakina River has effected a considerable reversal of
drainage by incising steep-walled canyons in the bottoms of widely flaring valleys.
The Taku Plateau was covered by glacial ice, which smoothed the profiles of
upland surfaces and valleys. Cirque erosion at a late stage of glaciation sculptured
the northern slopes of high points projecting above the general upland surface in
the Menatatuline Range.
[References: Kerr F. A., “ Taku River Area,” GeoZ. Surv., Canada, Mem.
248, 1948; Souther, J. G., “ Geology, Tulsequah,” Geol. Surv., Canada, Map
6-1960.1
[Photographs: B.C. 899:74,91; B.C. 952:13,55,65,105.]
Kawdy PZateau
The Kawdy Plateau (see Plate. XVIB) lies on the west side of the headwaters
of the Tuya River between the Taku Plateau and the Cassiar Mountains. The
upland surface of the plateau is largely unwooded and, for the most part, is at about
5,000 feet elevation. The surface is largely an undissected late Tertiary erosion
surface which, between Jennings River and Kedahda River, was locally upwarped
to 7,000 feet, and subsequently dissected to form the Atsutla Range.
“ The surface of the Kawdy Plateau, 600 to 700 square miles in area, is a
gently rolling upland of low relief developed by erosion, mainly on highly folded
Pakeozoic rocks. A large area lying near the south-western flank of the Atsutla
Range has broad, flat summits. These extensive flat areas are the surface of a
peneplain and the gently sloping summit surfaces of the mountains in the south-
western part of the Atsutla Range may be relics of a peneplain.” Presumably the
peneplain was uplifted differentially and was subsequently eroded in places to give
rise to the larger-scale features of the present topography. The southwestern front
of the plateau may be situated along a fault or a sharp monoclinal fold.
“ On the Kawdy Plateau conical or flat-topped mountains of agglomerate,
tuff, and lava, of the Tuya formation built by central eruptions, rest on the pene-
plain. . . . Some of the volcanics of the Tuya formation are associated with glacial
deposits and at least a part of the volcanism is evidently of Pleistocene age.“?
A conspicuous feature of the Kawdy Plateau west and southwest of Tuya Lake
are the flat-toppecl, steep-sided volcanoes, called tuyas, which are built up on the
plateau surface. There are seven or more in the area, and the highest of them,
Kawdy Mountain (6,372 feet) (fee Plate XVIB), rises almost 2,000 feet above
the local plateau level.
* Gtd. SLWV., Canada, Mem. 307, 1959, pp. S-6.
t Watson, IL Dep., and Mathews, W. H., B.C. Dept. of Mines, Bull. No. 19,1944, p. 34.
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