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