242 THE MAKQUETTE IRON BEARING DISTRICT. 



FOLDING. 



The major folding (Atlas Sheet IV) of the formation will be considered 

 in connection with the general geology of the district. It may be said here 

 that the formation has been affected by both east-west and north-south 

 thrusts. In some cases the east-west folds are more conspicuous, in others 

 the north-south, while in still other areas the folds are about equally prom- 

 inent in both directions, although even here the folds of one set have less 

 amplitude and less length than those of the other As a consequence of 

 the above, each fold has a pitch, which may be slight or veiy steep. Still 

 further to complicate the structure of the area, the major folds in each 

 direction have superimposed upon them secondary folds, and upon these 

 are tertiary ones. In some cases, as in the largest belt east of Goose Lake, 

 the pressure has not been so great as to give the beds very steep inclina- 

 tions, the dips usually being not more than 20°, although occasionally as 

 high as 50°. As a consequence of the nearly equal power of the folding 

 forces in each of the directions in this broad area, the ledges give strikes in 

 all directions. 



From the above it is clear that the deformation of the Kona formation 

 is a beautiful illustration of complex folding.^ 



To the pressure of folding the dolomite has usually yielded without 

 prominent fractures or cleavage. The same can not be said of the inter- 

 laminated slates, graywackes, and quartzites. In many places a bed of slate 

 has had developed across it a diagonal cleavage, which stops abruptly at 

 the limestone layers (fig. 9). In other cases the cleavage passes into the 

 dolomite itself, as, for instance, at the exposure back of the railroad section- 

 house near Goose Lake. In some places the dynamic movements have 

 produced a fissility in two directions, so that the rocks break into polygonal 

 blocks." In numerous instances the layers of chert and quartzite have been 

 fractured through and through by folding, so as to change them into breccias 

 resembling conglomerates (P! VII, fig. 2, and PI. VIII). Along the con- 

 tacts of the dolomite beds and the quartz layers accommodation Avas 

 necessary, and in places a bed of limestone may be seen bent into a series 



I Principles of North American pre-Cambrian geology, by C. R. Van Hise: Sixteenth Ann. Kept. 

 U. S. Geol. Survey, Part 1, 1896, pp 626-631. 

 ■ Ibid., pp. 643-646. 



