Physical Features

the mountains are composed almost entirely of granitoid rocks. The peaks
in this part are not as high as those to the east but the terrain is more rugged
and the relief greater. The valleys are much more deeply incised and
drainage is well established, all major valleys being eroded to about the
same level.

Kemano and Kitlope River valleys are also longitudinal valleys, carrying
drainage to the Gardner Canal from the western slope of this same line of
hills. These longitudinal valleys form the trunk drainage arteries in this
part of the Coast Mountains, and a series of tributary, transverse valleys,
trending generally northeast, form a rectangular pattern with the longitudinal
lineaments. The transverse valleys and lineaments cross the divide and are
marked on the eastern slope by the long narrow lakes that characterize the
area. They are also apparent in the fiord system farther west on the coast.

Transitional Zone

East of the height of land the character and composition of the
mountains change perceptibly. The rocks are mainly volcanic and sediment-
ary types, cut by local stocks and cupolas of granitoid rocks. The sedimentary
and volcanic rocks are commonly highly metamorphosed. Main valleys
are 2,000 to 2,500 feet higher than on the western side of the divide and
yet the mountains are only slightly higher. The relief therefore is not so
great or the terrain so rugged. The main ranges, such as Chikamin, White-
sail, Tahtsa, Kasalka, and Sibola, trend northeasterly transverse to the
general trend of the Coast Mountains. They are parallel to, and separated
by, the transverse valleys occupied by the long narrow lakes and each is
characterized near its western extremity by a main peak just over 7,000
feet high, and towards its eastern end by a plateau-like area 4,500 to 5,000
feet high that merges into the general configuration of the main plateau area.
It is proposed to refer to these as ‘Transitional Ranges’.

The sedimentary and volcanic rocks composing the transitional ranges
trend northwesterly parallel with the trend of the Coast Mountains rather
than with the direction of the transverse valleys. Therefore, it appears that
these valleys are a result of erosional forces rather than orogenic factors.
Erosion, at least in its initial stage, did follow joints or fractures in the
batholithic rocks that are part of the regional fracture system. As erosion
continued the valleys were widened and deepened leaving highland areas
between them. There is some evidence that these valleys were well esta-
blished by early Tertiary time and that they were main ice channels during

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