A PECULIAR BELT OF OBLIQUE FAULTING 607 



the belt the fracturing has occurred on the north flank of another 

 distinct uplift. In the area between the two uplifts there has been 

 some but noticeably very much less faulting than on the imme- 

 diate flanks of the two uplifts. In the process of doming, the 

 strata near the west end of the faulted strip were uplifted on the 

 north and given a southerly tilt, while near the east end of 

 the zone of faulting the strata were uplifted on the south and thus 

 given a northerly tilt. Thus the two ends of the faulted area were 

 tilted in opposite directions. Such an opposite movement in- 

 volves a certain amount of twisting, or torsion. The axis of the 

 twist would coincide with the long axis of the present fault belt. 

 If the strains developed in this adjustment between the oppositely 

 tilted areas were sufficiently great, they would produce fracturing 

 along planes inclined approximately 45° to the axis of torsion, or 

 long dimension of the present faulted belt. Daubree's experiment 

 would suggest that these fractures should occur in two sets crossing 

 each other at right angles. One such set, to the number of more 

 than 90 faults, is in just the position to meet the requirements, but 

 the complementary set, with the exception of two very short 

 faults northeast of the Broadview dome, is lacking. 



The explanation of the failure of the cross-fractures to open 

 is sought in the trend of the axis of torsion, whose general direction 

 hovers around N.8o°W. The fractures of the set which actually 

 did form have a N.E.-S.W. trend. If the complementary set of 

 fractures had developed, they also should have opened in planes 

 inclined 45° to the axis of torsion and at right angles to the first 

 set, which would place them in the neighborhood of N.35°W. 

 It will be observed that this last figure is not far from the general 

 trend of the adjacent portion of the Rocky Mountains. The 

 Rocky Mountains owe their formation, for the most part, to com- 

 pressive stress. While the exact stress-strain relations involved 

 in the development of this portion of the Rocky Mountains are not 

 known with certainty, it is, however, certain that an effective 

 component of compressive stress (whether the strain were rotational 

 or non-rotational) has operated at right angles to their long dimen- 

 sion, and so also in a direction at right angles to the postulated 

 possible cross-fractures. Hence any such N.W.-S.E. fractures, 



