270 THE MARQUETTE IROX-BEARING DISTRICT. 



At the west, soutliwest, and south of the western ])hiti' of the Archean 

 of sec. 23 the basal conglomerate is well exposed in direct contact with 

 the xmderlying crystalline rocks. At the west foot of the hill is a solid 

 ledge of the white, inashed, schistose Archean granite. It is in contact 

 v/ith and mantled on l)()th sides l)y the conglomerate, which is mainly 

 composed of material exactly like the original rock. The fragments and 

 matrix of the conglomerate so closely resemble the granite that its recom- 

 posed character scarcely shows — so intensely mashed is the rock — except 

 upon the weathered surface, where may be seen rounded, protruding frag- 

 ments of the granite, varying in size from small ones to great blocks. In 

 passing eastward along the soutli slope of the bluft" the white granite of the 

 Basement Complex takes on a different character, here being less altered, 

 and containing pink augen of the original feldspar. In the field, as well 

 as from microscopical study, it is plain that it is a mashed granite. Adja- 

 cent to this granite the conglomerate contains predominant pebbles of a 

 corresponding kind. As further evidence of this unconformity, the white 

 and ])ink mashed granite is cut through and through Ija' veins of red granite, 

 Avhich are nowhere observed to cut the cong-lomerate. 



The contact is again seen in the valley to the .soutli, where the recom- 

 posed rock on a little ridge projects east as an arm into the area of the 

 Archean. Here the conglomerate has not been so much mashed. The 

 sparse clayey matrix is stuccoed with fragments of the red granite and the 

 white, kaolini(; (piartz-schist (maslied granite) from the Archean. Many of 

 these macroscopically closely resemble chert. The conglomerate appears 

 also to contain fragments derived from a slate or g-raywacke. The upper 

 part of the conglomerate contains, besides pebbles of granite and gneiss, 

 many pebbles of white quartz, some of which macroscopically appear to be 

 derived from a quartzite; also rare pebbles of chert and jasper, and many ot 

 a slaty or schistose rock. The matrix, usually white or pale-green, is ordi- 

 narily slate, graywacke, or quartzite, but oftentimes it is so fine-grained as 

 to have a novaculitic appearance. 



In sec. 22 also the actual contact between the gneissoid granite Archean 

 axis and the conglomerate is seen. Here are magnificent exposures of great 

 bowlder conglomerates, the granitic fragments of which, of varying sizes, 



