SECONDARY STRUCTURES OF BARABOO QUARTZITE 261 



parallel to the bedding are the more important. The diagonal 

 strike joints of the North Range are nearly horizontal, owing to the 

 vertical attitude of the beds. 



The effect which proximity to a contact has upon the abundance 

 of joints related to the folding is well illustrated on the South Range 

 near Devil's Nose, where the quartzite comes in contact with the 

 granite porphyry to the south. At this place, both bedding and 



> South 



Fig. I. — Vertical section, normal to the strike on the South Range, showing the 

 relation of the joints connected with the folding in weak, thin beds interstratified with 

 thick, strong beds. 



Strike joints are so closely spaced as to break the quartzite into a 

 rubble. Away from this contact, the zone of intense fracturing rap- 

 idly disappears. 



Strong beds have fewer joints related to the folding than weak 

 beds. Throughout the quartzite formation, weak, thin beds of 

 slaty quartzite are intercalated between massive, strong beds of 

 quartzite. Near the site of the old Cliff House on the east bluff 

 at Devil's Lake, there are two such weak beds, each about a half- 



