Landforms of British Columbia 1976 - Department of Geography

margin of the Rocky Mountains% it should be possible to outIine a belt of Front
Ranges for a considerable distance northwestward from their presently known
limit northeast of Mount Robson.
The hfkinchinka i?anges lie between Azouzetta Lake and the Rocky Mountain
Trench and extend from the Peace River southeastward for 150 miles, at least as
far as Fontoniko Creek. They have a width of 15 miles and constitute an important
division of the Rocky Mountains. The ranges coincide in position with the
Misinchinka schists, of late Precambrian and Cambrian age, which lie in a belt
along the east side of the Rocky Mountain Trench, and the subdued topography
of the ranges is a direct reflection of the character of these rocks.
The thick quart&e and limestone formations that give character to the Park
Ranges diminish in thickness in the vicinity of Mount Sir Alexander, and north-
westward their place is taken by the schistose rocks of the Misinchinka Group.
These rocks are unable to support the precipitous slopes and cast&&d forms
that are chamcteristic of the ranges to the southeast, and as a consequence the
whole aspect of the mountains has changed.
The Misinchinka Ranges characteristically have rounded wooded summits
ranging up to 6,500 feet (see Plate XXXVIB). They are drained by creeks flowing
westward into the Parsnip River and by creeks flowing eastward into tributaries
of the Peace. A characteristic of the westward-flowing creeks is their parallelism,
and theix trend of south 30 to 40 degrees west, a direction which is oblique to the
Trench. This direction, which is structurally controlled, appears consistently along
the Trench wherever the Misinchinka schists occur.
The upper surface of the continental ice-sheet during the Pleistocene stood
between 6,000 and 7,000 feet in the region between Mount Sir Alexander and the
Peace River. Unquestionably some of the rounded summits were overridden by
northeastward-moving ice, and some were little affected by alpine and valley
glaciation.
The combination of greatly lessened elevation and relief, of different lithology
and structure, and of reduced aIpine and valley glaciation have resulted in a
subdued alpine topography which is most unlike the familiar Rocky Mountains
of the south.
[References: Stott, D. F., “ Cretaceous Rocks between Smoky and Pine
Rivers,” Geol. Surv., Cmadu, Paper 60-16; Muller, J. E., “ Geology, Pine Pass,”
Geol. Surv., Canada, Map 11-1961; Tipper, H. W., and Muller, .I. E., “Geology,
McLeod Lake,” Geol. Surv., Canada, Map Z-1962.]
[Photographs: B.C. 759:108; B.C. 761:9; B.C. 763:96, 102; B.C. 767:13;
B.C. 1949:19.]
Muskwa Ranges
From the Peace River the Rocky Mountains extend northwestward to their
termination at the Liard River. These are the Muskwa Ranges, which have a
length of 260 miles and widths of 20 miles at the Peace River and 70 miles at
Sifton Pass. Their western edge is along the northwest-trending Rocky Mountain
Trench, and their eastern edge runs almost north from the Peace River, being
controlled by northerly trending bedrock structures and an in echelon expansion
eastward of the eastern ranges. This divergence results in the greatly expanded
width between Sifton Pass and Mount St. Paul.
From the Peace River, summit elexitions increase gradually to Mount
McCusker (8,393 feet) at the head of the Sikanni Chief River. Farther north a
number of high peaks include Mount Redfern (8,879 feet), Lombard Peak (8,300
90