27(3 THE MARQUETTE IRON-BEARING DISTRICT. 



slate and <iTav\vacke, Avitli occasional iiiterstratified conglomeratic phases. 

 The hrst and larg-est of these islands is tliat near the center of sec. 23. 

 This is an oval area, with its greater diameter in a northwest-southeast 

 direction. It is almost entirely surrounded by abundant exposures of the 

 Wewe formation, but those of the greatest interest are along the southwest 

 laorder. Just north of the quarter line is a great basal conglomerate, in 

 contact with and resting iipon a white schistose granite microscopically 

 resembling quartz-schist. The fragments and matrix of the conglomerate 

 are almost wholly from the granite, and the rock is so firmly cemented that 

 fresh fractures break across the matrix and pebbles, so that its recomposed 

 character scarcely shows, except iqxm the weathered surface. Where 

 weathered, there may be seen well-rounded fragments of tlie granite, from 

 those of small size to great bowlders, protruding from the matrix. A thin 

 belt of this conglomerate mantles the gi-anite for some distance along the 

 brow of tlie bluff, and here, besides the white granite, are also found 

 fragments of granite bearing pink feldspar crystals and fragments of red 

 granite. The matrix of the conglomerate is an ordinary quartzite. In the 

 -core area the pink feldspar-bearing granite was found associated with the 

 ■white granite, and the red granite cuts both. 



A short distance south of the quarter line of the section, on the south- 

 west slope of the bluff, great exposures of conglomerate are again found in 

 contact with and immediately adjacent to the granite. Here, on close 

 examination, it is perfectly clear where the schistose granite ends and the 

 schistose conglomerate begins. The latter varies from a coarse conglom- 

 erate, bearing abundant granitic debris, to a fine-grained conglomerate in 

 which the fragmental particles are mainly siaigle quartz and feldspar grains. 

 This conglomerate in its upper part is interlaminated with slate and gray- 

 wacke phases. As a consequence of the intense folding to which the rock 

 has been subjected, it has become brecciated, so that with the genuine 

 detrital fragments derived from the granite are also angular to subangular 

 fragments of the slate and graywacke. 



Farther to the southeast is a small creek, and across this to the south- 

 west, on the slope of a great bluff, is again found the sericitic schistose 

 granite, which is directly overlain by conglomerates containing pebbles of 



