50

both of which strike northwesterly and dip northeasterly, and its presence
is inferred by the fact that the Takla strata dip towards those of the
older Cache Creek beds. The apparent displacement is that of an uplifted
northeast block, and the dip of the fault is unknown.

Omineca Fault

The Omineca fault extends northwesterly from Omineca River at the
east border of the map-area to Niven River at the west border. It enters
the map-area from the southeast as the single northwesterly counterpart
of the Pinchi fault zone of the Takla area (Armstrong, 1946), but has
several branches in McConnell Creek map-area, as shown on the accom-
panying map. It marks the approximate northeastern limit of recognized
major faulting.

The most southeasterly exposures of the fault were found at, and 1 mile
northwest of, its intersection with Genlyd Creek. The isolated exposures
of brecciated, buff weathering, carbonated rock noted there display many
well-developed slickensided surfaces and a little bright green mineral,
possibly mariposite, and are interpreted as altered rock of the fault zone.
The wall-rocks were not seen.

On the east side of Carruthers Creek, about 5 miles from its mouth,
purplish red, andesitic, pyroclastic rocks of the Takla group have been
involved in the fault zone and now occur as a heterogeneous assemblage
of comparatively unaltered material and buff to rusty weathered, car-
bonatized rock, the whole traversed by a network of carbonate veinlets
and steeply inclined fractures displaying highly polished surfaces. Within
this assemblage were seen several outcrops of, probably, a tabular body
of light grey feldspar porphyry closely resembling a phase of the Kastberg
intrusions. Although somewhat fractured, it is probably less disturbed
and altered than the enclosing rock, and perhaps later than at least some
of the movement and alteration along the Omineca fault zone. Thin-bedded
carbonaceous Cache Creek strata on the west side of the creek are crumpled,
sliced, and at one place cut by a seam, about 2 feet thick, of soft, sticky,
light grey gouge with a steep southwesterly dip. The width of the fault
zone here is probably several hundred feet.

Small scattered exposures of thoroughly carbonatized rock mark the
postulated course of the fault between the above described point on Car-
ruthers Creek and Asitka River.

About 3 miles northwest of Asitka River the fault separates Asitka
and Takla strata on the southwest from younger voleanic members of the
Takla group on the northeast. It is exposed at a point 34 miles northwest
of the river and, although viewed only from a distance, appears to dip
steeply southwest and to comprise a crumpled, rusty, and reddened zone,
1,000 feet or more in width.

It was again located in the bed of a northerly flowing creek that enters
Niven River about a mile east of longitude 127 degrees. Here, Sustut sand-
stones lie southwest of the fault and are gently inclined except within
about 50 feet of the fault where they have been dragged to a nearly vertical
position, sheared, fractured, and intersected by many white carbonate
seams. The red and green Takla andesitic rocks that adjoin them and lie