410 THE MARQUETTE lEON-BEARING DISTRICT. 



The prominent exposures of the formation are usually near its base. 

 The rocks are here conglomerates. These grade into quartzites. At many 

 places in passing upward the quartzite approaches a graywacke, is conse- 

 quently softer, and therefore not so frequently seen. Exposures are partic- 

 ularly abundant in the Palmer and Negaunee areas, about the Ishpeming 

 basin, and as far west on the southern belt as the Fitch mine, sec. 24, 

 T. 47 N., R. 28 W. For the last 3 miles of this distance it constitutes 

 a rather [jrominent range. West of this place exposures are infrequent 

 iintil Humboldt is reached. Here are numerous outcrops north of 

 Mount Humboldt. At Republic are large and fine exposures. Many 

 outcrops are found iu the northern belt south of the Michigamme and 

 SpuiT mines. 



FOLDING. 



Broadly considered, the Goodrich quartzite is folded into a great 

 westward-plunging- synclinorium, the eastern end of the U extending from 

 Ishpeming southward. This eastern border of the fonnation comprises a 

 series of reentrants and salients — reentrants where there are minor syn- 

 clines, and salients where there are minor anticlines. On account of the 

 flat dip, corresponding to the Avestward plunge of the syncline, the forma- 

 tion here occupies a broad belt. On the south side of the formation at one 

 jalace the Goodrich quartzite and Negaunee iron formation are infolded and 

 overturned, having northward dips (Atlas Sheet XXVI). At this point 

 the Goodrich quartzite has a tongue running east into the iron fonna- 

 tion, being l)ounded both to the north and to the south by the rocks of the 

 Negaunee formation, which dip in the same direction as the quartzite. 

 The area at Negaunee is in general an east-west oval sjniclinal basin. 

 Here again there is minor folding, so that the formation terminates both to 

 the east and west iu a number of fingers. At the west end of the Jackson 

 mine the Goodrich quartzite and the Negaunee iron formation are folded 

 into a set of isoclinal overfolds, so that a north-south section passes three 

 times from one formation to the other. The Palmer belt is another 

 east-west synclinal basin, with a short arm extending to the southeast at 

 one place, due to the appearance of a central anticline. The Republic 

 tongue and that to the west are two closely compressed isoclinal synclines. 



