Landforms of British Columbia 1976 - Department of Geography
Landforms of British Columbia 1976 - Department of Geography 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). I P J ,
The Pinchi fault and its northwesterly continuation, the Omineca fault, has been mapped as a geological feature from Pinchi Lake northwestward for 180 miles to the Niven River. It has produced a lineament (9) which extends as a rather sinuous line of depressions and valleys. The controlling structure is a southwesterly dipping overthrust fault which has moved Permian rocks upward on the west side with respect to Mesozoic formations on the east. * This overthrust eventually may be found to link with a comparable thrust along the southwestern side of the Spatsizi Plateau. Its extension has been mapped for about 180 miles southeastward to the vicinity of Horsefly River. Its known length of 350 miles makes this fault one of the major structural features of the Province. A trellis drainage pattern is prominently developed in the sedimentary and metamorphic rocks in the Monashee Mountains east of the head of Seymour Arm of Shuswap Lake (see N.T.S. Sheet X2 M). Several conspicuous southerly trending lineaments are present, one of which (lo), well shown in photograph KC. 489:60, comprises the aligned valleys occupied by the head of Ratchford Creek, Myoff Creek, and Perry River. Many of these northerly lineaments are Tertiary faults along which and&tic and rhyolitic dykes have been introduced. A northwesterly trending lineament (11) along the northern wall of the Lil- looet River valley (see photo B.C. 566:X) lies upstream from Pemberton Meadows and extends for about 20 miles. It is the northernmost of several in the locality and may “represent a fault zone along which there may have been movement of Recent age. The Fraser River fault zone has been mapped along the Fraser River as far north as Big Bar. It has several strands, one of which runs up the Yalakom River, and is represented by a well-defined lineament (12) that is visible on topographic maps as well as on aerial photographs of the region (see B.C. 498:41). The over- all movement along the fault zone was to elevate the western side (Coast Moun- tains) with respect to the eastern side (Marble, Clear, and Hozameen Ranges).t A well-defined northerly trending lineament ( 13) which lies within the Fraser River canyon and extends southward from Spuzzum for 22 miles to Hope is clearly seen on photograph B.C. 589: 18. It continues over Silver Peak to the north end of Chilliwack Lake, a further 20 miles. It is a dip-slip fault whose trace south of Hope has been partly obliterated by the intrusion of the Chilliwack batholith.* A southeasterly trending fault-controlled lineament (14) extends 20 miles from Three Valley Lake to the head of the Shuswap River.5 The lineament is occupied by Wap Creek, the head of Shuswap River, and the lower part of Vanwyk Creek. An extremely well-defined lineament (15) follows the trace of the north- westerly trending Louis Creek fault zone, 11 which extends from the north end of Okanagan Lake to the North Thompson River at Barr&e, a distance of 70 miles. The lineament is marked largely by the valleys of Louis and Bolean Creeks and by minor topographic features. There are several major northwesterly lineaments on Moresby Island, The longest (16) is localized along a fault that extends,partly submerged from Lous- coone Inlet in a northwesterly direction through Burnaby Strait and east of Tanu to Louise Island, a distance of 60 miles. A second lineament, which may be con- * Lord, c. s., Gd. SW”., conmi.7, Mern. 251. 1948, P. 50: .4rlnstrong, J. E., Gee,. surv., Canada, Msm. 252, 1949, &I. 117.
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The Pinchi fault and its northwesterly continuation, the Omineca fault, has<br />
been mapped as a geological feature from Pinchi Lake northwestward for 180 miles<br />
to the Niven River. It has produced a lineament (9) which extends as a rather<br />
sinuous line <strong>of</strong> depressions and valleys. The controlling structure is a southwesterly<br />
dipping overthrust fault which has moved Permian rocks upward on the west side<br />
with respect to Mesozoic formations on the east. * This overthrust eventually may<br />
be found to link with a comparable thrust along the southwestern side <strong>of</strong> the Spatsizi<br />
Plateau. Its extension has been mapped for about 180 miles southeastward to the<br />
vicinity <strong>of</strong> Horsefly River. Its known length <strong>of</strong> 350 miles makes this fault one <strong>of</strong><br />
the major structural features <strong>of</strong> the Province.<br />
A trellis drainage pattern is prominently developed in the sedimentary and<br />
metamorphic rocks in the Monashee Mountains east <strong>of</strong> the head <strong>of</strong> Seymour Arm<br />
<strong>of</strong> Shuswap Lake (see N.T.S. Sheet X2 M). Several conspicuous southerly trending<br />
lineaments are present, one <strong>of</strong> which (lo), well shown in photograph KC. 489:60,<br />
comprises the aligned valleys occupied by the head <strong>of</strong> Ratchford Creek, My<strong>of</strong>f Creek,<br />
and Perry River. Many <strong>of</strong> these northerly lineaments are Tertiary faults along<br />
which and&tic and rhyolitic dykes have been introduced.<br />
A northwesterly trending lineament (11) along the northern wall <strong>of</strong> the Lil-<br />
looet River valley (see photo B.C. 566:X) lies upstream from Pemberton Meadows<br />
and extends for about 20 miles. It is the northernmost <strong>of</strong> several in the locality and<br />
may “represent a fault zone along which there may have been movement <strong>of</strong> Recent<br />
age.<br />
The Fraser River fault zone has been mapped along the Fraser River as far<br />
north as Big Bar. It has several strands, one <strong>of</strong> which runs up the Yalakom River,<br />
and is represented by a well-defined lineament (12) that is visible on topographic<br />
maps as well as on aerial photographs <strong>of</strong> the region (see B.C. 498:41). The over-<br />
all movement along the fault zone was to elevate the western side (Coast Moun-<br />
tains) with respect to the eastern side (Marble, Clear, and Hozameen Ranges).t<br />
A well-defined northerly trending lineament ( 13) which lies within the Fraser<br />
River canyon and extends southward from Spuzzum for 22 miles to Hope is clearly<br />
seen on photograph B.C. 589: 18. It continues over Silver Peak to the north end<br />
<strong>of</strong> Chilliwack Lake, a further 20 miles. It is a dip-slip fault whose trace south <strong>of</strong><br />
Hope has been partly obliterated by the intrusion <strong>of</strong> the Chilliwack batholith.*<br />
A southeasterly trending fault-controlled lineament (14) extends 20 miles<br />
from Three Valley Lake to the head <strong>of</strong> the Shuswap River.5 The lineament is<br />
occupied by Wap Creek, the head <strong>of</strong> Shuswap River, and the lower part <strong>of</strong><br />
Vanwyk Creek.<br />
An extremely well-defined lineament (15) follows the trace <strong>of</strong> the north-<br />
westerly trending Louis Creek fault zone, 11 which extends from the north end <strong>of</strong><br />
Okanagan Lake to the North Thompson River at Barr&e, a distance <strong>of</strong> 70 miles.<br />
The lineament is marked largely by the valleys <strong>of</strong> Louis and Bolean Creeks and by<br />
minor topographic features.<br />
There are several major northwesterly lineaments on Moresby Island, The<br />
longest (16) is localized along a fault that extends,partly submerged from Lous-<br />
coone Inlet in a northwesterly direction through Burnaby Strait and east <strong>of</strong> Tanu<br />
to Louise Island, a distance <strong>of</strong> 60 miles. A second lineament, which may be con-<br />
* Lord, c. s., Gd. SW”., conmi.7, Mern. 251. 1948, P. 50: .4rlnstrong, J. E., Gee,. surv., Canada, Msm.<br />
252, 1949, &I. 117.