SOME D YNAMIC PHENOMENA . 3 5 I 



same succession is seen on both sides of the fault, and if beds 

 of like character correspond, the amount of the throw is twenty 

 to thirty feet, and the south side has dropped relative to the 

 north side. In other words, the faulting is in the right direction 

 to reduce the theoretical thickness of the sediments as given by 

 Irving. The district has not been closely examined for other 

 faults, but the existence of one fault, even of a minor character, 

 suggests that a careful study of the whole area with reference to 

 faulting should be made, in order to determine what deductions 

 may possibly be made from Irving's estimate of the probable 

 thickness of the quartzite. 



At the upper narrows of the Baraboo, near Ablemans, we 

 are on the north leg of the anticline. The dip is throughout 

 from seventy to ninety to the north, and in some places the 

 layers are slightly overturned. The slipping along the bedding 

 has here been much greater. While in this area there are heavy 

 beds of quartzite which have not suffered great interior move- 

 ment, other beds have been sheared throughout, being transformed 

 macroscopically into a quartz-schist, but the foliation is strongly 

 developed. In other places, as described by Irving,^ where the 

 rock is a purer quartzite, for a distance of 200 feet or more 

 across the strike, the rocks have been shattered through and 

 through, and re-cemented by vein quartz. 



For the most part the rock is merely fractured, the quartz 

 fragments roughly fitting one another, but there are all grada- 

 tions from this phase to a belt about ten feet wide of true 

 friction conglomerate, the fragments having been ground against 

 one another until they have become well-rounded (a Rei- 

 bungs breccia). Between the boulders of this zone is a matrix, 

 composed mainly of smaller quartzite fragments. The whole 

 has been re-cemented, so that now the mass is completely vitreous. 

 This belt of friction conglomerate at first might not be discrim- 

 inated from the Potsdam conglomerate, immediately adjacent, 

 but a closer study shows how radically different they are. In 



'The Baraboo Quartzite Ranges, by R. D. Irving. In Vol. II., Geol. of Wis., 

 P- 5i6- 



