DISCUSSION OF CORRELATION 717 



area, the north edge of which was bounded by dark colored hornblendic and 

 micaceous schists of Huronian age, which I have since concluded are equiva- 

 lents of the youngest member of that series yet observed in the Marquette 



iron region The lithologic character of this wide granite belt bore so 



much resemblance to the Laurentian rocks, which are extensively developed 

 on the waters of the Sturgeon River in Michigan, 10 to 20 miles to the north- 

 east, that we were disposed at the time to believe that some phenomena of 

 folding or faulting had brought rocks belonging to that system to the surface 

 in an unexpected quarter. Professor Pumpelly and myself, several years 

 previously, had observed, farther to the north and west, similar granitic rocks 

 crossing the Michigamme and Paint rivers (branches of the Menominee), 

 presenting similar puzzling relations with beds known to be Huronian, and 

 younger than as well as lithologically different from any rock then known to 

 be of that period. 



A careful consideration of all of the facts to be observed in the Menominee 

 region confirms me in this hypothesis ^ 



The conclusion of Brooks is confirmed by the work of Hotch- 

 kiss in the Florence district of Wisconsin in 1910.^ 



In 1911-14 the writer and assistants, through field mapping 

 and diamond drilling, traced what appears to be this same granite 

 from the Iron River district westward through the Animikie series 

 of the Vieux Desert-Conover district and Manitowish, Turtle, 

 and Marenisco ranges, in all of which it is in intrusive relation 

 with the sediments, and connected it with the "Eastern Laurentian 

 area" of Van Hise and Irving on the eastern Gogebic Range, which 

 was considered by these geologists to form a part of the Archean 

 basement complex, whereas it actually intrudes the Lower and 

 Middle Huronian series and is unconformably overlain only by the 

 Upper Huronian (Copps) series. Thus the great granite hatholith of 

 northern Wisconsin has been fairly demonstrated to he, not only in 

 intrusive relations with the Animikie sediments over several thousands 

 of square miles, hut also to he overlain unconformahly by. a pre- 

 Cambrian series which is unconformably below the Keweenawan. 



Inasmuch as the Vulcan (Animikie) series of the Crystal Falls, 

 Iron River, Menominee, Florence, and other Michigan districts 

 has been shown to be very probably equivalent to the Negaunee 



^ T. B. Brooks, "On the Youngest Huronian Rocks South of Lake Superior and 

 the Age of the Copper Bearing Series," Am. Jour. Sci., Vol. II (1876), 206-7. 

 2 Unpublished manuscript. 



