14 



University of California Publications in Geology [Vol. 10 



in which the table differs from the views held by other geologists, and 

 to these brief reference may now be made. 



As to sequences, it is first to be noted that Leith 11 is of the opinion 

 that in the Mesabi district there is a third granite which cuts the 

 Animikian. I have, however, in a former paper 12 pointed out how 

 doubtful the evidence of the age of this granite is and, as my skepti- 

 cism has deepened, I have omitted it from the table. 



In the Lake Huron section, also, I have taken the liberty of differ- 

 ing with Collins in his interpretation of the sequence. In doing this 

 I feel that I have not done violence to any direct evidence which he 

 has adduced as to the superposition of the Bruce series upon the 

 Temiskamian. The hypothesis of two and only two periods of granitic 

 invasion has been used to determine what the real sequence is. I have 

 placed the Bruce series earlier than the Killarney granite and the 

 Cobalt series later, and suggest that the Bruce series lies below the 

 Temiskamian, there being no very satisfactory evidence to the con- 

 trary. 



In southeastern Ontario there is doubt as to whether the Hastings 

 Series is the correlative of the Bruce or the Temiskamian. In the table 

 I have followed Miller and Knight who correlate it with the Temis- 

 kamian. 



My most serious difference, however, is with Allen and Barrett, not 

 as to the sequence on the south side of Lake Superior, but as to the 

 correlation of the rocks there with those on the northwest side. As 

 a result of some excellent field studies these geologists found 13 that in 

 the Gogebic district the rocks heretofore referred to the Animikian 

 really comprise two series separated by a major unconformity, involv- 

 ing the uncovering and degradation of the Presque Isle granite. This 

 granite is the second of two granites which occur in the district and 

 the major unconformity corresponds to the Eparchean Interval. Ac- 

 cording to the principle of correlation here advanced, the rocks which 

 follow the Eparchean Interval, namely, the Copps formation, should 

 be correlated with the Animikian of Thunder Bay. Allen and Barrett, 

 however, correlate the Tyler slate, etc., into which the Presque Isle 

 granite is intrusive, with the Animikian, and make the Copps forma- 

 tion and its equivalents post-Animikian, separated by a major uncon- 

 formity. This correlation involves the notion of three great granitic 



u U. S. G. S., Mon. 43, p. 411. 



i- Comptes Bendus Cong. geol. internat. XII, 1913, p. 367. 

 is Jonrn. Geo!., vol. 23, no. 8, 1915. 



