REPORT ON LAKE SUPERIOR REGION 461 



(4) in lithological character, from the base of the Keweenawan to its 

 upper portion, in the direction of likeness to the Lake Superior sand- 

 stone. (5) The deposition of this immense series must have been 

 an era of subsidences, and the Lake Superior sandstone seems to 

 have been formed through an area of subsidence ; and outside certain 

 limited areas like that near the Keweenawan fault there appears to 

 have been no reversal of this subsidence between the Lake Superior 

 sandstone and the Keweenawan, for the Lake Superior sandstone has 

 but very little material that may be fairly supposed to have come from 

 erosion of the Keweenawan. Its lithological character may be best 

 explained as that of a bed mantling over the Keweenawan and 

 deriving its material (frequently microcline) from the Laurentian 

 granite bosses. But if the subsidence was not extensively broken and 

 the Keweenawan is not Cambrian, then where are the middle and 

 lower Cambrian ? 



The lithological character of the beds is such that fossils will 

 hardly be found to help us. Of course, if Winchell proves to be 

 right in saying that the Animikie is Cambrian, all the more would 

 the Keweenawan be. But the Animikie is the kind of formation in 

 which Cambrian fossils should be found, if present. I have never 

 found them. The distribution of the Animikie and Keweenawan is 

 quite discordant, and I think the Keweenawan much more closely 

 associated with the Lake Superior or Potsdam sandstone. 



Still, the argument above is not a coercive one. The true correla- 

 tion of the Keweenawan is still an open question. And as the U. S. 

 Geological Survey has consistently classed the Keweenawan as pre- 

 Cambrian, I should not expect those at present in charge to change 

 until convinced beyond question that in changing they were right. 

 On the other hand, as my predecessors have classed the Keweenawan 

 as Cambrian, and I believe them right, I cannot change. The only 

 thing to do is to use the term "Keweenawan" or "copper-bearing," 

 which is unambiguous, and avoid committing oneself, except in those 

 formal classifications, where a formation must be placed in one pigeon- 

 hole or the other, and then only with due reserve. 



