tight and rarely isoclinal. Their fold axes orientations plot
on a great circle and not as a single average direction
(Fig. 56). Cleavage is axial planar to the folds (Fig. 56)
and parallel to bedding. Sericite and dissolution selvages
which define the cleavage surfaces, increase in abundance
with the decrease in silica. Pure cherts display no cleav-
age and pelites the most. Dissolution selvages that form
cleavage surfaces may be planar-parallel, in ‘‘hourglass’’
form about pinching points, or stylolitic. The coarsest
selvages are irregular. Selvages form along impurity-rich
lenses and beds and are generally layer-parallel. Stilpno-
melane and pumpellyite randomly grow within the Antler
Formation rocks. Conodonts extracted from the chert
have alteration indexes (Epstein et al., 1977) of 3 to 5,
denoting maximum regional paleotemperatures of 200 to
350°c.

The fold axes lie along the great circle that is the aver-
age orientation to the ductile folds within the Cariboo
Terrane. They therefore could be related to the same
structural history. Such a configuration is caused by fold-
ing of nonparallel surfaces, suggesting the rocks of the
Antler Formation were deformed prior to folding.

Brittle shortening and extension

The sedimentary rocks of the Antler Formation locally
have crenulations and kinks that fold cleavage. The
crinkle axes parallel the semiductile fold axes, whereas
the orientation of the kinks is highly variable.

Upright faults have northeast and northerly trends,
and transect the formation and its boundaries (for exam-
ple, the Antler Creek fault). Joint sets throughout the vol-
canic rocks are well developed and are generally perpen-
dicular to the strike of the cleavage (Fig. 57). All upright
faults appear to postdate the emplacement of the Antler
Formation.

Crooked Amphibolite

Unlike the Antler Formation the Crooked Amphibolite
is dominated by shear foliation which parallels the con-
tact with the Barkerville Terrane. It pervades every rock
type in the unit except serpentinite. The shear fabric has
no associated folds. Metamorphic chlorite, actinolite and
hornblende grow with long axes in the shear surface.
There are no randomly orientated metamorphic minerals.

The shear foliation formed during thrusting of the
Crooked Amphibolite. The thrusting may have had mul-
tiple episodes of movement, as deduced from the lack of
Overgrowing metamorphic minerals.

Figure 56. Equal area net plots of the poles to cleavage
and the trend of fold axes from the Slide Mountain Ter-
rane Antler Formation. 1S-S, 2S-S and 3S-S are plots of
the poles to cleavage from the 1S, 2S and 3S structural
domains as shown on Figure 25. These three plots are
combined in 1/3S-S. 1S-F, 2S-F and 3S-F are plots of the
trends of the folds from the 1S, 2S and 3S structural
domains as shown on Figure 25. These three plots are
combined in 1/3S-F.

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