32

In the vicinity of Anyox several faults are known to have large dis-
placements. A northwesterly striking fault dipping steeply northeast is
followed by Bonanza creek. This fault has a vertical throw of at least
800 feet; the horizontal offset is not known. The northeast side has
dropped down. A northerly striking fault with a horizontal offset of 2,500
feet is followed for some distance by Falls creek. The east side has moved
south with reference to the west side. Two northerly striking faults with
smaller offsets are exposed in the workings of the Hidden Creek mine at
Anyox.

A fault in Marmot River valley offsets a bed of limestone at least 400
feet. Many straight, narrow valleys in the Bear River district follow
crushed zones but in most cases the total amount of differential movement
was not discovered. The belt of dykes already referred to is apparently
offset where it crosses Bear river. The contact of the Coast Range batho-
lith is offset similarly where it crosses Bear river. On the mountain side
east of Portland Canal in line with the above-mentioned points of offset-
ting the batholith contact is again offset but the extent of the movement
is not so accurately known. Apparently a large fault strikes along Bear
River valley from American creek to Stewart. The fault probably
branches at American creek, the main branch following the creek. The
apparent horizontal offset along this fault in Bear River valley is approxi-
mately 14 miles. The east side has moved southward or the west side
northward. In view of the fact that the apparent offset is measured by
the displacement of intrusive contacts and since such contacts may turn
sharply for no evident reason, it follows that the apparent offset along
Bear river does not necessarily prove the existence of a fault, It is very
likely, however, that a fault does exist. The fact that other faults in the
district with similar strike show horizontal movement lends weight to the
belief that movement along the big fault was chiefly horizontal. Evidence
on this point is also furnished by the mineral deposits on opposite sides of
the fault. As the fault offsets the Coast Range batholith it is also later
than the mineral deposits of the area. If the movement along the fault
had been essentially vertical marked differences should exist between the
mineral deposits on opposite sides of the fault and that is not the case.

The Bear River fault may branch at Stewart, one branch continuing
across Bulldog creek and along Georgia river, and the other branch, if
there is another, continuing along Portland canal. It is very likely that
the fault along Georgia river strikes south along the south fork of the river
and thence down along Falls creek. This would link up the Falls Creek
fault with the Bear River fault. If these faults are part of a single fault
the Bear River fault is then apparently 50 miles long.

Most of the faulting took place after the intrusion of the Coast Range
batholith but prior to the intrusion of most of the dykes, for though the
dykes are commonly offset by faults yet the offset is in general much
smaller than the total offset along the fault. Some of the faults preceded
some of the mineral deposits, but most of the known faults are later than
the mineral deposits.