PRE-CAMBRIAN NOMENCLATURE 63 



are older than the Laurentian eruptives in the Great Lakes region, 

 where these rocks have been most widely studied, should not the 

 western geologists revise their point of view and drop either the 'Tro- 

 terozoic" or the "Azoic," or both, from their nomenclature? 



A third point in the report requires comment, viz., the separation 

 of the Keweenawan from the Huronian as an upper pre-Cambrian 

 formation. The break between the Keweenawan and the Animikie 

 is certainly not more important than that between the Animikie and 

 the next lower formation, the Middle Huronian of the new classifica- 

 tion, Logan's Upper Huronian. If the Animikie, which was not 

 included by Logan in the Huronian, is now placed within it, why not 

 close up the gap and include the Keweenawan also as a provisional 

 fourth division of the Huronian ? Probably most geologists who have 

 studied the Keweenawan would be inclined to place it with the Cam- 

 brian, and some have suggested that the Animikie also is early Cam- 

 brian. Certainly the two formations should go together. 



Since the Huronian as mapped by Logan and Murray included 

 some areas now called Keewatin, the new definition has shifted the 

 use of the term upward, omitting part of the lower rocks, but adding 

 the Animikie above. Logan intended that the Huronian of the upper 

 Lakes should include all the rocks between the base of the Cambrian 

 and the Laurentian, since he suggests that the two divisions of the 

 upper copper-bearing rocks (now known as the Animikie and the Kee- 

 weenawan) are probably equivalent to the Potsdam and the Chazy.^ 



If the Huronian is defined as including all between the Cambrian 

 and the Keewatin, the term "Algonkian" becomes unnecessary and 

 should be dropped, at least in the Lake Superior region. Possibly its 

 use might be continued in the west, where the equivalence of the pre- 

 Cambrian beds with those of the east is not certainly proved, but the 

 law of priority should undoubtedly reinstate the name Huronian in 

 the east. However, the term Algonkian is carefully omitted from the 

 committee's report, perhaps in order not to raise a fresh subject for 

 controversy. It may be taken for granted, I suppose, that Canadian 

 geologists will continue to use the name Huronian instead of Algon- 

 kian ; and it is to be hoped that if American geologists prefer to retain 



^Geology of Canada, 1863, p. 86. 



