DISCUSSION OF CORRELATION 707 



iron-bearing series of the Marquette district. In 19 14 Allen and 

 Barrett found that the Upper Huronian, as described by Van Hise 

 and Irving, on the east end of the Gogebic Range includes two uncon- 

 formable series separated by a profound unconformity. This dis- 

 covery has, in their judgment, opened the way for a revision of the 

 correlation of the Huronian group of the Lake Superior region in 

 which some of the difficulties and inconsistencies in the old classifi- 

 cation largely disappear. 



The new correlation places the Animikie series in the Middle 

 Huronian, rather than in the Upper Huronian as in former 

 correlations. Briefly stated, the steps in the argument are 

 these : 



1. The Animikie (iron-bearing) series of the Gogebic Range is 

 the equivalent of the Negaunee (iron-bearing) series which consti- 

 tutes the Middle Huronian of the Marquette Range; therefore, the 

 Animikie series of the other Michigan districts, Minnesota, and the 

 north shore of Lake Superior is also the equivalent of the Negaunee 

 series, i.e.. Middle Huronian. 



2. The Negaunee series of the Marquette Range is unconform- 

 ably overlain by the Upper Huronian. The Ironwood (Animikie) 

 series of the Gogebic Range is also overlain unconformably by a 

 series which is unconformably beneath the Keewenawan. This series 

 is equivalent to the Upper Huronian of the Marquette Range. 

 The Animikie is therefore Middle Huronian. 



CORRELATION OF THE ANIMIKIE SERIES AS MIDDLE HURONIAN 



Correlation of the Ironwood series with the Negaunee series. — 

 The Ironwood (Animikie) iron-bearing series of the Gogebic Range 

 is correlated with the Negaunee (Middle Huronian) iron-bearing 

 series of the Marquette Range because (i) these series occupy 

 identical positions in the Huronian succession of these districts, 

 (2) are essentially similar, (3) are underlain and overlain by essen- 

 tially similar series, (4) are in practically adjacent territory, and 

 (5) there is substantial evidence of their equivalence through direct 

 connection of the Negaunee series with the Vulcan (iron-bearing) 

 series of the Crystal Falls-Iron River district which bears the same 

 relation to a great granite bathoHth and its outliers as does the 



