ales
_ dips. about 70 degrees to the northwest.

Nor'thward nlone the Highwoy peyona mile 342, and near the
British Columbio-Yukon boundary, black and rusty shale outcrops in
Lierd River forming a canyon, ond very soft weathering shale and inter-
bedded limestone outcrop for about 800 yards ae the Beane The dip
here is about 28 degrees toward the southwest.

Northward, the Highway is some distance east of: the river and
traverses a rolling sandy terrain that is part of the river valley.
At mile 350 a branch road turns north to Watson Take Air Port.

Watson Iake is about 53 miles long and 13 miles wide. Its
elevation.is shown as 2,230 feet above. sea-level, and the adjoining !
plain rises about 10 to 15 feet above it. Only sand was noted in the ©
banks of the lake. Low, wooded hills aise 10 to 12 mel to the ©
northeast.

\

Old Land Forms

The composite skyline of the Rocky. Mountains is somewhat
above 7,000 feet in the front ranges near Summit Iake and somewhat ‘below
6,000 feet south of Liard-River. Individual peaks and groups of peaks
rise above the general level, where structure and rock. hardness have
resisted erosion. Elsewhere greater initial uplift may have been &
controlling factor. Softer rock formations have beén eroded’ into lower
mountain groups or into TERRES ae

Extending outward from the is ae Sapaciaiey toward the
eist, remnants of a plains surface-are préserved in numerous flat-topped
hills. This surface.is tangent to-the upper rounded mountain tops of
the Rocky’ “Mountains.and dips away with decreasing ‘slope: opproaching the
horizontal 50 miles from the mountains. The perfection of upland pre-
servation is dependent upon relation to stream channels, but more es-
pecially upon the structure and resistance of the underlying rocks. Thus
at mile 98, 15 miles from the Rocky Mountain front, folded Triassic sed=
imentary beds of little resistance to: erosion form rounded hills with an
elevation of about 5,400 fect. Near mile 94, similar formations rise to
5,000 feet. Thirty miles farther cast the resistant conglomerates of
Steamboat, Table, and Teepee Mountains rise to a maximum elevation of
4,800 feet, with surface slopes representing the attitude of the beds.
From these upland surfaces, flat-topped hills are conspicuous to the
Bouvheast and to some extent to the east and northeast.

Westward en the front range of the Rocky Mountains, the up-
land surface sags into the valleys of MacDonald Creek and Racing River, .
where rounded, forested mountains of little resistant, shaly rock have
preserved the former upland very imperfectly. the Rocky Mountains south
of Liard River preserve occasional level tops, and the isolated mountain
ridges and hills north of the Liard indicate the general downward slope
of the upland in that direction. From ® summit elevation of about 3,000
feet near Liard River, the uplands ote to about 2,000 fect farther to the
north. a

Well-defined benches are preserved on resistant sandstones
on Steamboat Mountain and nearby hills at elevations of 400 to 500
feet below the upland surfaces. Such benches may bé traced to the west-
ward where low flat-topped hills, or valley bottoms, now deeply en-
trenched, represent once widespread and weéll- established lowlands. These
lower surfaces are represented in the Rocky Mountains themselves’ north of
Summit Pass, where rocky terraces occur at. an elevation of about 5,000 .
feet. From the pass, the benches descend to the west dowm the valley ‘of
MacDonald Creek, where they lie only poorly preserved in the area of Devono-
Mississippian shaly rocks. Northward from Toad Valley are similar benches