113

HALFWAY RIVER TO STEAMBOAT MOUNTAIN

The structure in Halfway River Valley, where this river flows across
the Plains, has not been recorded in any publication. Possibly some gentle
folds are to be found there.

In Sikanni Chief and Buckinghorse Valleys, adjacent to, and west of,
the Highway, small folds have been noted. They are recorded under
‘Foothills’, page 121 (See also Figure 3).

On the western border of the Plains, on and east of Minaker River,
several small folds have been observed and carefully studied. On Minaker
River, east of the Pocketknife anticline, Hage (1944) has indicated a small
putieline or ‘roll’. A few miles to the northeast is the Minaker River
anticline.

The axis of the Minaker River anticline, trending about north 14
degrees west, crosses the Alaska Highway at latitude 57°45’ and Minaker
River less than 2 miles west of the Highway (Hage, 1944). Dips vary from
3 to 15 degrees. Hage notes that, because exposures are few, this structure
is not fully understood. On the same river, below the mouth of Beaver
Creek, several minor folds were observed on the east limb of this anticline;
these small folds, however, were not seen in exposures along the Highway
(Hage, 1944).

East of the Alaska Highway and not far from the mouth of Bear Creek,
near the western border of the Plains, the shales of the Buckinghorse
formation are folded into the Bear Creck anticline (Hage, 1944). The dips
are low, 5 to 6 degrees. The extent of this structure is unknown. Hage,
however, notes that a “few outcrops on the creek above and below the
Highway bridge (about a mile south of Indian Creek) . . . are suggestive of
an anticline that may be a continuation of the one on Bear Creek’’.

Williams (1944) has described the structure of the Plains along the
Alaska Highway west of Fort Nelson. For more than 50 miles, the Lower
Cretaceous sandstones and shales are flat-lying or have a gentle east dip.
The crest of a low, asymmetric anticline is situated about 51 miles west of
Fort Nelson. Farther west is a broad syncline, the axis of which lies about
on Tepee Mountain. Dips on the northeast limb are said to vary from 5
to 8% degrees southwest, and those on the southwest limb 53 to 10 degrees
northeast. No other structure has been reported between Tepee Mountain
and the Foothills, where the Triassic is brought to the surface on the axes
of several anticlines.

Nothing is yet known of the structure on the Plains east of the Alaska
Highway between Fort St. John and Fort Nelson.
FOOTHILLS
PINE AND PEACE RIVER FOOTHILLS

Portage-Butler Structural Zone
(See Figure 11)

The Portage-Butler structural zone on the eastern border of the Peace
River Foothills trends from north to northwest, and is described as an
‘anticlinorium’ by Beach and Spivak (1944). The resistant conglomerates