IjAWSON.] 



The Eparchcean Interval. 



61 



from the adoption of the correlation here suggested, it may be 

 simply remarked that Upper Keewatin would have to give way 

 to Huronian, while Keewatin has priority over Loiver Huronian. 

 The following tabulation expresses my understanding of the 

 standard time sequence of the more important groups of rocks 

 of the Lake Superior province, with appropriate designations 

 and indications .of the essential features of the correlation, cer- 

 tain granites that are intrusive in the Huronian being omitted 

 from the scheme. It is not supposed that the scheme is complete ; 

 other rock groups will doubtless be discovered and necessitate 

 its enlargement. But it is a fairly consistent statement of what 

 I conceive to be our knowledge of the relationships of the rock 

 groups of the region. 



Cambrian (Upper division or Potsdam only) 

 Unconformity. 



PALEOZOIC I Keweenawan. 



^Algonkian \ Unconformity. 



( Animikie - Penokee = Upper Marquette. 



EPARCEL3EAN INTERVAL. 



/Huronian = Upper Keewatin = Lower Marquette, etc. 

 Unconformity. 



\Laurentian, so called, granite gneisses, etc., (intrusive 

 ARCH E AN ( in the Ontarian)and the Carltonian anorthosites. 



C Keewatin - Lower Huronian = Crystalline 

 ' schists of south shore invaded by 



Ontarian -( Unconformity. [granite-gneisses 

 \ Coutchiching. 



In conclusion, I rejoice to see that the Algonkian wave is 

 beginning to break. Professor Van Hise, in a paper which has 

 not yet reached me, but which is quoted with very pertinent 

 comment by Willmott,* announces the discovery that the Algon- 

 kian, comprehensive as it is by definition, does not embrace all 

 of the pre-Cambrian elastics. This is an important admission, 

 and implies the abandonment of the definitions of both Archaean 

 and Algonkian which have been promulgated by the publications 



*loc. cit. 



