DISCUSSION OF CORRELATION 723 



now correlates with the Negaunee and refers to it as "distinctively 

 Negaunee type." If the Hemlock iron formation and the Vulcan 

 were considered the same in 1911 and prior years, what new evi- 

 dence may be cited on which they may be separated now? The 

 only new evidence is the discovery of the fact that the iron formation 

 at the Hemlock mine and for several miles north and south of it is 

 Negaunee, and this is therefore precisely the evidence to which Dr. 

 Leith refers as damaging to the new hypothesis and in confirmation 

 of the old correlation. 



Dr. Leith has also laid emphasis on the fact that the uncon- 

 formity at the Hemlock mine has not been traced across the 

 northern part of the Iron River district and therefore that proof 

 is lacking that any part of the Michigamme slate occupies an 

 inferior position with reference to this unconformity. This is a 

 weakness in the new hypothesis, but it is certainly not greater than 

 the weakness in the argument which has been advanced that this 

 unconformity cuts out the Negaunee formation in the northern 

 part of the Crystal Falls district and in some unknown place passes 

 beneath the Vulcan formation of the southern part of the district. 

 if the greenstone belt north of the Iron River district is Hemlock 

 (Middle Huronian) as correlated by Clements as well as by Van 

 Hise and Leith (1911), there is an anticlinal structure here which 

 demands that the unconformity turn "back on itself at some place 

 south of Amasa" and carry "out westward to the north of the 

 Iron River-Crystal Falls district" (see Fig. 3). This would 

 seem a necessary consequence of Dr. Leith's published inter- 

 pretation of the structure with which I agree (in reversal of my 

 opinion in 1909) because of the discovery of the unconformity in 

 question and the evidence based on the recent drilHng in the 

 vicinity of Crystal Falls. In brief, the structural facts point to a 

 closely compressed S3nicline between the two masses of volcanics, 

 similar to those northeastward including the Republic trough, with 

 the formations involved sharply upturned on its opposite limbs. 



GENERAL REMARKS ON THE CORRELATION OF THE ANIMIKIE SERIES 

 WITH THE MIDDLE HURONIAN 



The correlation of the Animikie series with the Middle Huronian 

 eliminates what would otherwise be the necessity of assuming a 



