508 



W. H. Hohhs — Post-glacial Faulting. 



moutonnees which are everywhere, tell the same tale of 

 the tremendous grinding efficiency of the continental 

 glacier which first advanced and later retreated across 

 this region. 



The pattern of the channels whose rectilinear elements 

 are so clearly revealed by the drainage map and to Avhich 

 the writer has already called attention,^ is reproduced 

 on a smaller scale in the individual zigzags of the canoe 

 routes. Some of the fractures which have exercised the 

 control w^ould appear to be pre-giacial, for the glacial 

 modelling of the surface extends down to and beneath the 

 water surface ; but in other cases movement along these 



Fig. 2. — Post-glacial fault in gneiss. French river district. 



fractures has been subsequent to the retreat of the gla- 

 cier from the district, and escarpments are found on which 

 no trace of the elsew^here dominant glacial polishing and 

 scoring is to be seen. Such escarpments generally run 

 closely parallel to the stream channels and rise to esti- 

 mated heights in some instances in excess of one 

 hundred feet. Distinct rifts have also been noticed and 

 in such cases the channel is bordered on opposite banks 

 by parallel escarpments. A fault of this sort is shown in 

 ^g. 2 and a larger one lined by high escarpments 

 extends for more than a mile. In such cases I have found 



^ Bull. Geol. Soc. Am., vol. 22, p. 151, fig. 26, 1911. 



