Landforms of British Columbia 1976 - Department of Geography

Devonian limestones that are thrust up and over younger rocks. The ranges
comprise castellated limestone peaks facing northeastward with dip slopes on their
southwestern sides. The eastern side of Munch” Lake valley presents a remarkable
dip slope on southwesterly dipping limestone beds, Between the two ranges is an
area of low to moderate relief along Nonda Creek and Racing River, eroded in
soft upper Devonian shales and Lower Triassic shales and sandy limestone lying
above the cliff-forming Ramparts Formation.
The crossing of the northern Rocky Mountains along the Alaska Highway,
although scenic and most interesting, lacks the overwhelming grandeur of the high
country around Mount Churchill between the heads of the Gataga, Toad, Tuchodi,
Kwadacha, and Muskwa Rivers,
Longitudinal valleys of considerable width and length are prominent features
of the Muskwa Ranges, They are eroded parallel to the structural trend along lines
of faulting or along belts of softer, more easily eroded rock. These longitudinal
valleys give the drainage a pronounced trellis pattern which varies from region to
region, depending upon the character and distribution of the underlying formations.
Glaciation in the northern raoges was uneven in intensity. The high area
around Mount Churchill evidently was a local centre of accumulation from which
valley glaciers moved outward along the several major valleys, and late-stage alpine
and valley glaciation has left its mark open the topography. Some areas withii
the Muskwa Ranges show little or no evidence of glacial erosion-continental ice
did not erode them nor was there late-stage cirqne or alpine glaciation. However,
the former presence of an ice cover is revealed by the almost universal veneer of
drift.
The Robbit Plufeau is an area of gradually diminishing summits transitional
between the Muskwa Ranges and the Liard Plain. It is the topographic equivalent
of the Dease Plateau that occupies a similar transitional position between the
Cassiar Mountains and the Liard Plain.
The Rabbit Plateau is triangular in shape and extends for about 50 miles
between Fishing Lake and the Kechika River, with a maximum width of about
20 miles. It is bounded on the northwest by the Liard Plain and on the southeast
by the Rocky Mountains along a southwesterly line between Fishing Lake and the
Rocky Mountain Trench just south of Horneline Creek.
The plateau (see Plate XXXIIA) consists of low wooded ridges rising to an
even skyline elevation of 4,000 to 5,000 feet and has a relief of 2,500 to 3,000
feet, The area is drained by the Rabbitt and Vents Rivers, and tributaries of the
Kechika River.
The plateau is underlain by northwesterly plunging folded sedimentary rocks
of lower Palzeozoic (Cambrian) to Devonian and Precambrian age. The plateau
is geologically the same as the Muskwa Ranges directly southeast, but is lower in
swnmit elevation because the late Tertiary erosion surface was tilted northward
and merges in the Liard Plain.
[References: Williams, M. Y., “ Geological Investigations along the Alaska
Highway between Fort Nelson and Watson Lake,” Gal. ,Surv., Cmada, Paper
44-28; Gabrielse, H., “ Geology, Kechika,” Gtd. Surv., Canada, Map 42-1962;
Gabrielse, H., “ Geology, Rabbit River,” GeoJ. Surv., Canada, Map 2-1961; Irish,
E. J. W,, “ Geology, Halfway River,” CkoJ. Surv., Canada, Map 22-1963; McLean,
F. H., and Kindle, E, D., “ Geology of Northeastern British Columbia,” GeoJ.
Surv., Canada, Man, 259, 1951; Laodon, L. R., and Chronic, B. .I,, “Palzozoic
Stratigraphy,” A: ,4. P. G., Bull. Vol. 33, No. 2, 1949, pp. 189-222; Odell, N. E.,
Can. Geogr. Jour., Feb., 1949.1
[Photographs: B.C. 187:104; B.C. 194:54; B.C. 955:103, 120.1
92