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due east of the outlet of Uslika Lake, where outcrops distributed over more
than a mile show the contact to be a curving fault whose plane is nearly
parallel with the bedding of the conglomerate. The conglomerate is highly
sheared along the fault, and pebbles have been deformed into elliptical
disks and cigar-shaped bodies, for widths of 3 to 20 feet from the contact.
The deformation of the pebbles and the direction of slickensides on the
fault planes show that the last important movement was one in which the
Uslika formation moved upward and to the east-southeast relative to the
older rocks to the northeast.

Any postulated sequence of rock movements that would produce the
structural relations shown by the Uslika formation appears to involve two
separate fault movements, with the plane of the later fault intersecting
that of the earlier one. The following explanation is hypothetical, but is
compatible with the geometry of the structures and the observed evidence
of faulting (See structure-section G-H). It is suggested that the con-
glomerate, previously folded into a synclinal structure, was carried bodily
eastward and stratigraphically lower across the tilted Takla group strata
and onto the late Paleozoic rocks by a flat thrust from the southwest. This
thrust curved up more steeply at its eastern end to form the present exposed
east and northeast contact of the conglomerate, and placed the beds of
both units in a roughly parallel position. After the movement on the first
thrust fault had ceased, a steeper fault, whose plane crossed that of the
older break, developed. Motion on tthe later fault relatively raised the
entire region west of Conglomerate Mountain, and moved the late Pale-
ozoic strata onto the west side of the Uslika formation, where again the beds
are roughly parallel. This later, relatively steeply dipping reverse fault
may be related to the subparallel faults that separate the divisions of the
Cache Creek group to the east. According to this hypothesis, the Uslika
formation must represent an isolated mass, a klippe, underlain by a spoon-
shaped thrust plane whose extension to the west, in a block now relatively
uplifted, has not been recognized or has been removed by erosion. The
klippe, if such it is, has been complicated by at least two later periods of
faulting.

Alternative hypotheses, based on a normal movement on ‘the eastern
contact of the conglomerate, bringing the Uslika formation down to its
present position from the northeast, may be made to explain the observed
structural relations of these rocks. Such hypotheses, however, involve
movement in a direction opposite to the observed evidence of the direction
of the last movement of the eastern contact. The size and abundance of
granitic pebbles in the conglomerate suggest that the formation was
deposited relatively close to the Hogem batholith, which must have been
less widely exposed when the Uslika formation was laid down than it is at
present. For these reasons it is considered more probable that the Uslika
formation was brought to its present position by a warped thrust from the
southwest than by a normal fault from the northeast.