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unconfromity is in marked contrast with the little folded structure above
it. This angular unconformity was also observed by Williams (1944).

MUNCHO LAKE TO LIARD RIVER BRIDGE

Very little is known of the structure along the Alaska Highway north-
west of Muncho Lake. In or near Liard River Valley, not far from the
Liard River bridge, Williams has observed some east-west faults, which he
considers are connected with the abrupt, northern termination ot the eastern
Rocky Mountains.

EAST OF SIFTON PASS

Hedley and Holland (1941) state that slates, argillites, limestones, silt-
stones, and rare volcanic rocks occur in the Rocky Mountains immediately
east of Sifton Pass. Sufficient field work was not done to determine the
structure, but steep dips suggested close folds.

LIARD PLAIN

Limestone outcropping on the west bank of Coal River above the
Highway bridge (over Coal River) is said by Williams to have, on the
average, a northwest strike. The dips suggest to Williams a series of sharp
anticlines and synclines. Limestone beds west of Coal River are said to
have high dips and variable strikes.

ROCKY MOUNTAIN TRENCH

The northern part of the Rocky Mountain Trench separates the north-
ern Rocky Mountains on the east from the Omineca and Cassiar Mountains
on the west. It is probably a surface manifestation of a structural zone in
which faulting is an important feature. This zone is narrow, long, almost
straight, and trends northwest.

Hedley and Holland (1941) state that some of the faulting in the
Trench may be as recent as late Tertiary. The Sifton formation in the
Trench is said to be strongly detormed, showing high dips, drag-folds, and
shear zones and faults. The direction of the Trench is said to be at an
angle of about 10 degrees with the trend of the Rocky Mountains structures.

EASTERN PART OF OMINECA AND CASSIAR MOUNTAINS

West of the Rocky Mountain Trench, in the eastern part of the Omineca
Mountains, rocks of the Ruby (Proterozoic) and Ingenika (Lower Cam-
brian) groups are folded into two, northwesterly trending anticlinoria on
which open subsidiary folds are superimposed (Roots, 1948).

Farther north, in the eastern part of the Cassiar Mountains, between
the Cassiar batholith and the Trench, sedimentary rocks of probable
Palxozoic age are folded into anticlines and synclines. Hedley and Holland
(1941) state that this folding is not so uniform as in the RockyMountains
east of the Trench. Individual folds are interrupted by cross flexures and
complicated by drag-folds and thrust faults.