THE LOWER HURONIAN ICE AGE 



155 



are apt to run impartially through pebble and matrix. One cannot 

 but be struck by the close resemblance the two rocks have to one 

 another in every particular. Every argument which goes to prove the 

 glacial origin of the Dwyka conglomerate applies equally well to the 

 Lower Huronian conglomerate of northern Ontario, with one exception. 

 No underlying striated surfaces or roches moutonnees have been 

 found beneath the Lower Huronian tillite ; while beautifully glaciated 

 surfaces are displayed beneath the northern Dwyka. It should be 

 remembered, however, that no such surfaces have been found under 

 the southern Dwyka, where the conglomerate passes downward into 



Fig. 5. — Dwyka tillite to left, Lower Huronian to right. 



shale, e. g., near Matjesfontein. It may be recalled also that at many 

 points in North America no ice-smoothed surfaces are found under 

 Pleistocene bowlder clay. This is the case at Toronto, where the 

 underlying Hudson shale is never polished or striated but seems 

 almost to blend upward into the lowest sheet of bowlder clay. The 

 absence so far as known of roches moutonnees under the Lower 

 Huronian conglomerate is then no valid argument against its glacial 

 origin. 



EXTENT OF THE LOWER HURONIAN GLACIATION 



The striated stones referred to earlier in this paper were obtained 

 at two points three or four miles apart, in a cutting on the Temis- 



