354 THE JOURNAL OF GEOLOGY. 



than the belts of schist. Consequently, at the upper narrows of 

 the Baraboo no evidence was found of faulting which could 

 reduce the estimated thickness of the quartzite as given by 

 Irving. 



As Irving clearly saw, bearing strongly in favor of the theory 

 of a great fold, is the increasing steeper dip of the layers in 

 passing north. The phenomena of movement and metamorphism 

 corresponding so exactly to those required by a simple fold, the 

 question may be asked if these are not evidence of some weight 

 in favor of the general correctness of Irving's conclusion as to 

 the structure. Had monoclinal faulting extensively occurred, it 

 would not have been necessary to have had so great a readjust- 

 ment of the beds as has been shown to occur by the schists, 

 cleavage, and the exceedingly intricate macro -fracturing and 

 micro -fracturing of the rock beds and their constituent par- 

 ticles. 



In addition to the phenomena described by Irving, 

 in summary, the Baraboo quartzite ranges show results of 

 dynamic metamorphism as follows : A fine example of the 

 Reibungs Breccia may be seen. A fault zone of limited throw 

 exists. All phases are exhibited, between a massive quartzite, 

 showing macroscopically little evidence of interior movement 

 through a rock exhibiting in turn fracture and cleavage, to a 

 rock which macroscopically is apparently a crystalline schist. 

 The foliation of the schists is parallel to the original stratifica- 

 tion, being consequent upon the movements of the beds over 

 one another, readjustments occurring mainly in the softer layers. 

 In thin sections the schists still give clear evidence of their 

 fragmental origin, but also show the mechanical effects of 

 interior movement. These same effects are apparent within the 

 heavy beds of quartzite, some readjustment of the particles to 

 their new positions being here also necessary. There is no evi- 

 dence that the semi -crystalline character of the schist and 

 quartzite are due to high heat. Nowhere are the particles fused. 

 So far as they are destroyed it is by fracture, and the rock is 

 again healed by cementation. 



