Landforms of British Columbia 1976 - Department of Geography

Moose Valley. North of Bear Lake the ranges are flanked by the Skeena Moun-
tains, and south of it by the Nechako Plateau. Between Thutade Lake and the
south end of Takla Lake, the Hogem Ranges are 140 miles long and have a maxi-
mum width of 30 miles.
At the northern end the Axelgold Range is eroded from Paleozoic and
Mesozoc volcanic and sedimentary rocks; the Connelly Range, however, is com-
posed of Upper Cretaceous or Paleocene sedimentary formations lying on the
eastern limb of a syncline. Erosion of the gently dipping beds has resulted in gently
sloping ridges and in mountain slopes parallel to the dip, with abrupt cliffs cutting
across the dip slopes. In the south the Sitlika, Vital, and Mitchell Ranges are
underlain essentially by limestone and argillite of late Paheozoic (Permian) age,
intruded by granitic rocks of the Omineca Intrusions.
The highest peaks are Sustut Peak (8,100 feet), west of Sustut Lake near the
northern end, and Tsitsutl Mountain (6,600 feet), west of the south end of Takla
Lake. All the peaks are circlued on their northern sides and stand sharply above
widely flaring valleys.
The Hogem Ranges differ only in degree from the Swannell Ranges by having
topographic forms less influenced by granitic rock. Because they are flanking
ranges and lateral to the axis of greatest uplift, their summit elevations are generally
not so high as those in the Swannell Ranges.
[References: Lord, C. S., “ McConnell Creek Map-area,” GeoZ. Surv., Canada,
Mem. 251, 1948; Armstrong, J. E., “Fort St. James Map-area,” GeoZ. Surv.,
Canada, Mem. 252, 1949; Roots, E. F., “Geology and Mineral Deposits of Aiken
Lake Map-area,” Geol. Szuv., Canada, Mem. 274, 1954.1
ROCKY MOUNTAIN TRENCH
The Rocky Mountain Trench (see Plates XXII, XXIVA, and XXXIVB) is a
remarkable topographic feature which extends northwestward from the 49th parallel
almost to the Liard River, a total distance of almost 900 miles. For the first 450
miles, from the Montana Border to the McGregor River, the Rocky Mountain
Trench is a continuous, somewhat sinuous valley lying between the Columbia
Mounta$s on the west and the Rocky Mountains on the east. This valley is
from 2 to 10 miles wide and is occupied by the southward-flowing Kootenay
River, northward-flowing Columbia River, southward-flowing Canoe River, and
northward-flowing Fraser River. The divides between the headwaters of these
rivers are low. In this southern stretch the eastern wall of the trench is the western
front of the Rocky Mountains, and the western wall of the trench is the eastern
front of the Columbia Mountains.
At the McGregor River, however, the line of the Rocky Mountains is breached,
and the bold mountain front on the eastern side of the trench is offset about 15
miles northeast. At the same place the western wall of the trench disappears, and
the trench merges in the Fraser Basin at an elevation of 2,000 feet. The southern
half of the Rocky Mountain Trench, which for 450 miles was continuous and clearly
defined, ends here, even though the structure which it follows may continue north-
westward past Mount Averil and McLeod Lake as the McLeod Lake fault zone.*
The northern half of the Rocky Mountain Trench begins on the north side of
the McGregor River, at the divide between James Creek and the Parsnip River,
and continues northwestward to the point where, at the junction of the Kechika
and Turnagain Rivers, the trench merges in the Liard Plain. The northern seg-
ment of the trench is flanked on the west at its southern end by the McGregor
* Mulkr, J. E., and Tipper, H. W., C&A. Swv., Canada, Map Z-1962.
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