Landforms of British Columbia 1976 - Department of Geography

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.