578 THE MARQUETTE IKOX-BEAKIXG DISTEICT. 



The cliief point upon whitJi more oA-idence is necessary is the relation 

 of the slates bearing- the rich iron ores in the Menominee district proper 

 to the slates associated with the volcanics iarther north in the connecting 

 district. If the Menominee slates are different from those to the north and 

 belong above them, the succession in the two districts would be very closely 

 analogous. Using the succession for the entire JIarquette district Avhich we 

 have made out, and comparing it with Smyth's succession in his Menominee 

 district, we have the following parallel descending succession: 



rpj)cr Marqiuite. Upper Menominee. 



Unconformity. 

 Loirer Marquette. Lower Menominee, 



Kejrauuee iron formation, 1,000 to l,.jOO[Micbigamme jasper, 

 feet [Slates bearing rich ores. 



Siamo slate, in places including inter- 

 stratified aniygdaloids, 200 to 625 feet 

 thick 



A.jibik qnartzite. 700 to 900 feet 



Wewe slate, 550 to 1,050 feet 



Koua dolomite, 550 to 1,375 feet Crystalline dolomite, 700 to 1,000 feet. 



Mesnard quartzite, 100 to 670 feet Basal quartzite, 700 to 1,000 feet. 



The succession for the lower series would tluis be very closely parallel 

 in the two distiicts, with the following exceptions: 



(1) The "We we slate, the Ajibik quai-tzite, and the Siamo slate are 

 placed opposite one member of the Menominee series. These thi-ee forma- 

 tions are, however, all fragmental and are equated witli a fragmeutal 

 formation. Together they mark a time of mechanical deposition in each 

 district between the nonfragmental limestone and the nonfragmental iron 

 formation, and thus include the physical change involved in passing from a 

 nonfi'agmental to a fragmental and then again to a nonfragmental forma- 

 tion. The chief difference is that in the Marquette district two layers of 

 mud were separated by a layer of sand. Another difference is that in the 

 Menominee district volcanics are much more important, and tliis may 

 account for the absence of conditions favorable to sand deposits. However, 

 it is interesting to note that amygdaloids are found in the Lower Marquette 



Slates and altered volcanics, maximum 

 thickness, 2,000 feet. 



