outcrop there may be up to 4 or 5 joint orientations. Only
1 or 2 of these will be prominent. There is a difference
in modal joint orientations between the Cariboo and Slide
Mountain terranes.

As with cleavage orientations, joints have been plotted
by stratigraphic group and domain (Fig. 31 and 32). The
modes are well defined for the Cariboo Group in all
domains. For the Black Stuart Group and Guyet and
Greenberry formations the data have more scatter. The
modal attitudes of the poles to joints and the fold axes
are similar enough to suggest that the joints are primar-
ily of the ‘ac’ type.

Pre-Columbian palinspastic reconstruction

Palinspastic reconstructions removing effects of the
Columbian Orogeny show possible configurations of the
unconformity at the base of the Black Stuart Group prior
to Columbian deformation. Cross-section E-E’ and the
Kimball Mountain area from cross-section D-D’ were
used to make the palinspastic sections of Figure 33.

Two reconstructions are presented, each with a dif-
ferent horizontal datum. Figure 33B has the horizontal
datum at the base of the Mural Formation to satisfy the
hypothesis of no pre-Black Stuart deformation. Pre-Black

0-4%

4-8%

8=12%

12-10%

16-20%

>20%

Figure 31. Equal area net plot of the poles to joints within rocks of the Kaza and Cariboo groups
of the Cariboo Terrane. A, B and C are averaged plots from domains 2, 3 and 4 (Fig. 25) with

22, 31 and 26 points respectively.

44