Landforms of British Columbia 1976 - Department of Geography

The second most prominent lineament is the Peliy Creek lineament (2.)) which
diverges from the Rocky Mountain Trench and follows valleys occupied by the Omineca
River, Mesilinka River, Pelly Creek, and Obo River and Lake. North of
Johiah Lake it appears to join the Dull Lake linearnew (3 ) , which leaves the Rocky
Mountain Trench at Sifton Pass and follows valleys occupied by Frog River, Denetiah
Lake, Dal1 Lake, and Deadwood Lake to the north end of the Horseranch Range,
a distance of almost 150 miles.
The Pelly Creek lineament between the Parsnip River and the intersection with
the Dal1 Lake lineament has a length of 200 miles. In the Aiken Lake area “ the
Pelly Creek lineament represents an east-dipping plane of weakness which has formed
the axial plane of an overturned fold, or, where movement is greater, an underthrust
fault which meets the major faults of the Rocky Mountain Trench at depth.“*
The White River lineament (4) diverges southeast from the Trench at the
mouth of the Bush River and follows valleys occupied by Succour and Blackwater
Creeks and the Beaverfoot, Kootenay, and White Rivers for a distance of 110 miles.
The White River lineament is localized along the White River Break, which is a
“ major longitudinal fault zone that limits the Western Ranges sub-province [of the
Rocky Mountains] on the northeast.“t Throughout its length the fault zone lies
entirely within Cambro-Ordovician shale of the McKay Group and is marked by
a wide belt of highly sheared calcareous phyllite.
Topographic maps and aerial photographs of the Rocky Mountains and Rocky
Mountain Foothills reveal the close relationship between stream patterns and bedrock
structures. Minor structures, such as joints in the Misinchinka schists, are
reflected in the drainage pattern of southwesterly flowing tributaries of the Parsnip
River (see N.T.S. Sheet 93 o) while the major overthrusts which separate the several
Front Ranges appear as topographic lineaments. Sheet 93 o shows a prominent
lineament (5), at least 75 miles long, followed by Clearwater and Callazon Creeks,
Link and Mountain Creeks, and Burnt River, which marks the trace of a westerly
dipping overthrust that bounds the Murray Range on its northeast side.
The Bovie lineament (6) is the only prominent lineament in the Fort Nelson
Lowland (see N.T.S. Sheet 94 0). It is a north-northeasterly trending alignment of
cues&s extending for 50 miles between the Fort Nelson and Petitot Rivers. The
Bovie lineament has resulted from the thrusting of thick, hard Permian chert and
Mississippian limestone eastward over the softer Buckinghorse Formation by the
Bovie fault. The west-dipping chat and limestone form the cuestas, whose eastern
faces are fault-line scarps parallel to the Bovie fault.!:
The southeast side of the Nass Basin at Dragon Lake is delineated by a northeasterly
trending lineament (7), well shown on Plate XXIA and having a length of
at least 18 miles. The lineament is emphasized by the erosion by glacial ice which
flowed outward from the basin and westward down the Nass River valley. The controlling
structure is not known, but its trend is parallel to prominently developed
northeasterly lineaments, such as those followed by the Iknouk and Kincolith Rivers
and Observatory Inlet, that are well displayed on N.T.S. Sheet 103 P and in photograph
B.C. 469:96. These lineaments follow a major joint direction in the granitic
rocks of the Coast Intrusions.
Erosion along the Takla fault,8 which is about 40 miles long, has produced a
northerly trending lineament (8), which is not recognizable on topographic maps
at 4 miles to the inch, but which is recognizable on aerial photographs of the region
(see B.C. 460:70).
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