UNCONFOKMITY AT TOP OF LOWER MARQUETTE SERIES. 563 



Basement Complex. This particularly occurs in the west and southwest 

 parts of the district, west of Champion and along the Republic tongue, 

 where but few members of the Lower Marquette series Avere deposited. 

 Even within a short distance the differential erosion was considerable. For 

 instance, at the south end of the Republic tongue the variation was more 

 than 1,500 feet. 



To just what extent the Lower Marquette series was altered during 

 this period of folding and erosion it is impossible to say. It is probable 

 that the upper formation, cQusisting of the readily altered iron carbonate, 

 suffered the most, and there are indications that ferruginous chert and jasper 

 were formed in the upper part of the formation. At least fragments of such 

 materials are found in the succeeding formation, and either these rocks were 

 produced from the iron carbonate during this folding and erosion or else 

 the iron-carbonate bowlders and fragments, in common with portions of the 

 Negaunee formation, were at a later time altered in a like manner, so as to 

 produce the same mineral combinations in the fragments and in tlie 

 Neo-aunee formation itself. It is probable that such subsequent modifi- 

 cation has occurred to some degree, but many would doubt whether it 

 were possible for such exactly similar changes to have occun-ed as to make 

 the bowlders and fragments of cherty siderite and the siderite of the under- 

 lying Negaunee formation into precisely similar chert and jasper. 



THE rPPER MARQUETTE SERIES. 



DEPOSITION OF THE UPPER MARQUETTE SERIES. 



The Upper Marquette history begins with the second transgression of 

 the sea, as a result of which the Ishpeming formation was deposited. If we 

 may judge by the greater thickness of the Goodrich quartzite of this forma- 

 tion at the eastern part of the district, and the greater erosion of the Negaunee 

 formation at the western part, an anticline had formed to the west, and the 

 transgression of the sea was again from the east or northeast. Thus, the 

 Negaunee formation in the eastern part of the area was more quickly buried. 

 In other words, the western part of the formation was liigher and was sub- 

 jected to longer erosion. Therefore, in the eastern part of the district the 

 sediments of the Goodiich quartzite first began to form. The western part 



