12 C. R. VAN HISE THE PROBLEM OF THE PRE-CAMBRIAN 



highly probable that the Keweenawan is pre-Cambrian ; but from this 

 view Lane dissents. 



REPORT OF THE INTER?fATIONAL COMMITTEE 



The results of the above studies in the Lake Superior region, largely by 

 the United States geologists, were accepted in 1904 by the Joint Commit- 

 tee of Canadian and United States Geological Surveys, consisting of 

 Messrs Adams, Bell, Lane, Leith, Miller, and Van Hise. After visiting 

 the Lake Superior and Lake Huron regions, they recommended the recog- 

 nition of tlie succession, structure, and nomenclature given below : 



Cambeian — Upper sauclstoues, etcetera, of lake Superior. 



Uncoufo^mit5^ 

 Pke-Cambrian. 



Keweenawan (Nipigon). 

 Unconformity. 



r Upper (Animikie). 

 I Unconformity. 



Huronian .... J Middle. 



Unconformity. 

 Lower. 

 Unconformity. 

 Keewatin. 



Eruptive contact. 

 Laurentian. 



The report of the International Committee gave no major groujsing of 

 the above series. In this paper the Keweenawan and tlie Huronian are 

 together included in the Algonkian, and the Keewatin and Laurentian in 

 the Archean. This grouping will not be discussed at this point, except 

 in relation to the magnitude of the unconformity between Huronian and 

 the Keewatin. Already it has been indicated that the field studies of the 

 United States geologists show this unconformity to be more conspicuous 

 and widespread than any of the others. This conclusion, largely based 

 upon studies in the Lake Superior and Lake Huron regions, upon both 

 sides of the boundary, has been confirmed by studies over extensive areas 

 Ijy W. G. Miller, provincial geologist of Ontario, and E. W. Brock, the 

 recently appointed director of the Canadian Geological Survey. IMiller 

 has recognized tliis break at many localities and has empliasizcd it in his 

 various papers. Brock in a recent repoz't upon the Larder Lake district 

 recognized a great break at this horizon. He says in reference to rock 

 systems on opposite sides of the break :' 



"It is interesting to find at such widely separated points as lake Superior, 

 lake Huron, Cobalt, and the Height of Land, the same rocks, showing the same 



'Sixteenth Keport of the Biii-eau of Mines, part i, 1907, p. 20G. 



