42
ORIGIN OF THE PHYSICAL FEATURES

One of the most striking features of the area is the nearly flat charac-
ter of the uplands at elevations of 5,500 to 6,300 feet, the highest parts
being in the south-central area and the lowest in the northwestern. The
structure sections across the area (See Map 2046) show that a great
thickness of rock has been eroded from even the highest parts. The
rounded or gently rolling and flat-topped summits at nearly accordant
levels with a general northwest or west slope towards Fraser valley, show
that the area at one time was reduced by erosion to a gently rolling plain.
Across this plain streams flowed at no great depth below the present upland
surface. This old plain-like surface has been dissected in places to depths
of over 2,000 feet, and must have been uplifted to permit of such deep
dissection. In the eastern part of the area, in the bottom of the main valley
of Antler creek, there are narrow rock canyons 100 to 200 feet deep, which
indicate that a later, small amount of uplift, probably late Pleistocene,
also occurred. Between Barkerville area and Fraser river at Quesnel, the
general level of the surface is about 3,000 feet, but gradually decreases
towards the valley of the Fraser, which, at Quesnel, is several miles wide,
and nearly 1,000 feet below the plateau level, a part of the Interior Plateau
as defined by G. M. Dawson. <A few miles southeast of Quesnel, there is,
however, a mountain ridge, which appears to be nearly as high as the lower
summits in Barkerville area and, therefore, rises considerably above the
Interior Plateau level in the vicinity. Its top may represent an extension
mostly eroded away of the upland, plain-like surface in Barkerville area.
If this is so, the upland surface in Barkerville area is much older than the
Interior plateau and is about 3,000 feet higher.

In view of the immense time that has elapsed, it would be unreason-
able to contend that the nearly flat upland surfaces in Barkerville area
are actual remnants of an old peneplain; it is believed, rather, that they
represent a degraded form of the old surface. The remarkably flat sur-
faces, for example, on Bald mountain, are most likely due to glaciation.
The scantiness of drift on the uplands indicates that the surface of the
ice-sheet stood for a long period at about the level of the upland surface,
and that this surface was gradually degraded by frost and wind action
and by slow creep of the eroded material to the level of the ice-sheet.

The stream valleys of the region have a pattern that indicates a con-
trol by the structural features of the bedrock, but in places the pattern is
very irregular because of the results of stream capture and of reversal in
places of the direction of drainage. Several of the valleys trend in the
general direction of the axes of folding of the rocks; others are nearly at
right angles along the direction of cross-fracture of the rocks. The main
q valleys were formed for the most part by stream erosion in pre-Glacial
{ time, but there were many changes in the character of the valleys and in
the direction of drainage as the result of glaciation and of stream capture.
These changes are described in detail in Chapter III.