GLACIAL ORIGIN OF HURONIAN ROCKS 467 



therefore that the conglomerate was formed under water and that there 

 was carbonate in solution. If the larger erratics were brought by 

 ice it was probably not land ice. 



SUMMARY 



In appearance the conglomerate-quartzite-shale series of the 

 Huronian represents nothing so closely as compacted glacial and 

 glacio-fluvial debris. The finding of striated and soled pebbles 

 confirms the supposition of such an origin. The character of the 

 contacts thus far found do not disprove that glaciers placed the basal 

 conglomerate, though they suggest that such was not the case. 



There are some sudden transitions from shale to coarse conglomer- 

 ate which suggest that the earlier deposits may have been overridden 

 by land ice. It seems probable however that part of the material 

 was deposited under water and that floating ice contributed its load 

 of glacier-derived material. 



There is no reason for supposing that the thick bowlder-free beds 

 of shale and graywacke are not ordinary water-laid sediments, though 

 they may contain glacial floor. 



