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ranges’ are said to be much disturbed. Later, Bocock (1929) stated that
beds near and west of the summit in the mountains along Pine River occur
in thrust blocks; for example, the Misinchinka shales are said to be over-
thrust on Devonian limestones.

It is remarkable that the section exposed along Peace River, in the
Rocky Mountains, so easily accessible by canoe or small boat, has not yet
been studied systematically. Selwyn (1877), in his report on a reconnais-
sance examination of Peace River Valley in 1875, merely noted that the beds
on Mount Selwyn have a high southwest dip. Later, McConnell (1896)
observed west and southwesterly dipping strata, reverse faults, and sub-
ordinate folds. He also noticed that the age of the rocks outcropping
along this river, in the mountains, increases from east to west; Precambrian
and probably Cambrian strata outcrop in the west, and Devonian, Mis-
sissippian, and Triassic beds have been located in the eastern part of
the section. It is inferred that overthrusting in the west is more intense
than in the east, and, consequently, older rocks have been brought nearer
the surface in the west than in the east.

The structure of the mountains between Peace River in the south and
the Alaska Highway in the north has not been recorded in any publication.

SUMMIT LAKE TO MUNCHO LAKE

The structure of the eastern half of the Rocky Mountains along the
Alaska Highway, between Summit and Muncho Lakes, has been studied in
detail by Laudon and Chronic (1949), who have published a structure
He Some notes on the structure have also been provided by Williams
(1944).

Williams states that the structure is similar to that in the south, and
that compression from the west has produced overturned folds and thrust
faults. The mountain front lies just east of Summit Lake, and is said to
be marked by a major thrust, where grey limestone, presumably of Silurian
age, is faulted against Triassic shale. The mountain front is said to be
straight and well defined for miles to the northwest and southeast of
Summit Lake.

The same mountain front is displayed in Laudon and Chronic’s
structure-profile. In what they call the Stone Range, Precambrian (pre-
Silurian), Silurian, and Devonian formations dip west or southwest at a low
angle. The eastern front of this range is defined by a west-dipping fault
where Precambrian beds are thrust upon Devonian shales. Farther west,
in Racing Creek Valley, Devonian, Mississippian, and possibly Triassic
terrains are folded into several low, broad anticlines and one narrow anti-
cline.

West of Racing River Valley and in the high Sentinal Range, Pre-
cambrian to Devonian formations occur in several large thrust blocks,
separated by west- or southwest-dipping thrust faults. Within the thrust
blocks, dips are low to moderately steep. ‘These structures extend to
Muncho lake (Laudon and Chronic, 1949).

A prominent feature of Laudon and Chronic’s structure-section is the

angular unconformity between the Precambrian (pre-Silurian) strata and
the Silurian limestones. The undulating, well-folded structure below the