720 C. K. LEITH AND R. C. ALLEN 



The contrast is so marked that in 1 910 1 described these graywackes 

 under the distinct formation name^ of Paint slate and called atten- 

 tion to the structural evidence indicating that they are strati- 

 graphically above the Vulcan (Animikie) series. 



The correlation of the Paint formation presents a difficult 

 problem. It constitutes a large part of the Michigamme series 

 heretofore correlated with the Upper Huronian. We have seen that 

 there is strong evidence that the Vulcan slate-iron formation series 

 of the Iron River-Crystal Falls district, which has been described 

 as a part of the Michigamme, is Middle Huronian. That part of 

 the Michigamme slate which is known to be Upper Huronian is con- 

 fined to a limited area adjacent to the western part of the Marquette 

 iron range and the northern part of the Crystal Falls district where 

 it is plainly unconformably above the Negaunee iron-bearing series. 

 If the Paint slate is conformable with the Negaunee-Vulcan, it 

 follows that the part of the Michigamme slate which is Upper 

 Huronian must rest unconformably on it, and from the areal 

 distribution of these formations it appears that the plane of 

 the unconformity should intersect the erosion surface somewhere 

 north of the Paint formation north of the Iron River district. Un- 

 fortunately, a general scarcity of exposures in the area where the 

 unconformity may be expected to occur and the difficulty of 

 identif3dng horizons over any considerable distance in formations 

 of these kinds will render the discovery and mapping of this uncon- 

 formity, if it exists, difficult. It is being searched for at the present 

 time. 



As bearing on the probable age of the Paint formation it may be 

 said here that the Wolf Lake granite, north of Watersmeet in 

 T. 46 N., R. 39 W., is intrusive in quartz-mica schist which, judging 

 from lithology and areal relationships, is a metamorphic equivalent 

 of the Paint slate. The Wolf Lake granite is correlated with the 

 Presque Isle granite of the Gogebic Range and that in the inter- 

 vening territory and is beheved to be an outher of the great granite 

 bathohth of northern Wisconsin. The Presque Isle granite intrudes 

 the Middle Huronian (Animikie) and yields detritus to the Upper 



' R. C. Allen, "The Iron River Iron Bearing District of Michigan," Publ. 3, 

 Mich. Geol. and Biol. Survey, 1910. 



