714 C. K. LEITH AND R. C. ALLEN 



Vulcan (Upper Huronian). This seems to be an arbitrary classi- 

 fication and represents the necessity of making the change some- 

 where from the Negaunee of the Sturgeon trough to the Vulcan of 

 the Menominee Range. Lithologic similarity, proximity, and, 

 so far as known, similarity of succession were cast aside in favor of 

 the supposition that the Felch schist opens out and connects with 

 sediments to the west which had been correlated as Upper Huronian, 

 although the area in which the connection is indicated is deeply 

 drift-covered and devoid of rock exposures. But even if this 

 connection were a fact, as it may be, it constitutes in our opinion 

 merely an added reason why the Groveland iron formation should 

 be correlated with the Negaunee, since the Crystal Falls slate-iron 

 formation series has been shown to be more probably Middle 

 rather than Upper Huronian. 



As a matter of fact Smyth did correlate the Groveland with the 

 Negaunee formation in 1899, but after Seaman's discovery of the 

 unconformity at the base of the Ajibik quartzite necessitated the 

 correlation of the Negaunee series with the Middle Huronian (1904), 

 VanHise and Leith in 191 1 took the Groveland out of the Lower 

 Huronian and placed it in the Upper Huronian. In order to 

 make this change it was necessary to assign a highly metamorphic 

 quartzite-mica schist series which is unconformably above the Grove- 

 land to the Keweenawan or Paleozoic, for the reason that no place 

 was then left for it in the Huronian group. Smyth was obviously 

 right in correlating the Groveland with the Negaunee formation. 

 The quartzite-mica schist series above the Groveland bears no 

 resemblance to the Keweenawan or Paleozoic. It is Huronian, 

 and we believe it should be correlated with the Copps, part of the 

 Michigamme^ and the Princeton series. The quartzite which is 

 unconformably above the slate-iron formation series (Animikie) 

 of the Florence district is similarly correlated. 



3. Calumet trough. — -In the Calumet trough, about 4 miles 

 south of the Felch syncline, the situation is practically identical 

 with that in the Felch Mountain district, and the same arguments 

 for revision of the correlation apply here as in the Felch district. 

 In other words, the iron formation now assigned to the Upper 



' For division of the Michigamme series, see discussion below. 



