DISCUSSION OF CORRELATION 715 



Huronian is believed to be really an equivalent to the Negaunee of 

 the Middle Huronian. Rocks similar to the quartzite-mica schist 

 series of the Felch syncline are exposed at the old Hancock explora- 

 tion in T. 41 N., R. 27 W., and in at least one or two places near the 

 southern edge of the Calumet trough. Each of the three Huronian 

 series seems to be represented here exactly as in the Felch syncKne 

 a few miles north. 



4. Menominee Range. — -The general similarity of the iron- 

 bearing series of the Menominee district with that in the Sturgeon, 

 Felch, and Calumet troughs and in turn with certain phases of the 

 Negaunee formation of the Marquette district, its similarity in 

 relation to the underlying Lower Huronian, and its areal connections 

 with the great slate-iron formation series of the Florence-Crystal 

 Falls district determine that the Vulcan of the Menominee Range 

 is probably of Negaunee age, and that if the iron formation in the 

 districts intermediate between the Menominee and the Marquette 

 ranges is Negaunee there is no basis on lithological, structural, 

 or other grounds for assigning the iron formation of the Menominee 

 Range to any horizon other than Negaunee, i.e.. Middle Huronian. 



Leith has described a remnant of cherty quartzite, of a maximum 

 thickness of 70 feet, lying apparently unconformably between the 

 Randville dolomite below and the Traders member of the Upper 

 Menominee series above in the vicinity of Norway,^ but he places 

 no emphasis on it so far as concerns its significance in the correla- 

 tions. This formation, according to the more recent opinion of 

 Dr. Leith,^ is a remnant of regolith unremoved by erosion in Lower- 

 Middle Huronian time. 



CORRELATION OF THE IRONWOOD SERIES (aNIMIKIe) OF THE 

 GOGEBIC RANGE WITH THE VULCAN (MIDDLE HURONIAn) 

 series of the crystal FALLS-IRON RIVER-FLORENCE- 

 MENOMINEE DISTRICT ON THE BASIS OF SIMILAR RELATIONS 

 TO INTRUSIVE GRANITE 



Area southeast of the Gogebic Range including Marenisco, Turtle, 

 Manitowish, Vieux Desert, Conover, Iron River, Crystal Falls, and 

 Menominee districts. — Probably the most striking feature of the 



^ Monograph 52, U.S. Geol. Survey, pp. 234-35. 

 2 As expressed in conversation with the writer. 



