260 THE MARQUETTE IRON-BEARING DISTRICT. 



ph?ises. As the result of the compacting and modilicatioii of these beds 

 we have shale, slate, novaculite, and graywacke. The color of these rocks 

 varies from red to black, with various shades of buff and brown, depending 

 upon the quantity and condition of the iron oxide. While many minor 

 alternations occur, one part of the Wewe formation may be as a whole finer- 

 grained than another part. For instance, at the exposures in the southeast 

 part of sec. 13, T 47 N., R. 2G W., the black, . finer-grained phases of the 

 slates occupy a higher horizon than the coarser, novaculitic-looking phases. 



As a consequence of the folding, certain of the slates, and especially 

 those that are fine-grained, have had develo2:)ed in them a slaty cleavage. 

 Also, along the zones of sharpest folding and of mashing, the rocks jiass into 

 mica-slate, or even into a rock approaching a mica-scliist. In some cases 

 they approach knotenschiefer in appearance. As a consequence of the 

 slaty cleavage and schistosity, in many ledges it is difficult to determine 

 the true strikes and dips. Howe-\-er, the true bedding is usually indicated 

 hj frequent alternations of darker and lighter colored materials. Often 

 parallel t<i the l)edding are cherty-looking layers, which frequeutl}' have a 

 lenticular character, the oval areas lying end to end, with intervening slate, 

 or overlapping. When followed closely, they are found in places to cut 

 in a minor way across the Ijedding. Often they brancli into two or more 

 parts, or send out stringers into the slate. In other cases the chert>- or 

 quartzose layers follow the schistosity rather than the bedding. Finally, 

 the slates and graywackes are usually cut by numerous veins running in 

 all directions. A close examination shows that whether these cherty parts 

 follow the bedding or the schistosity, or cut the rock at random, they are 

 secondary infiltrations. 



In man}' places the orogenic movements have been so powerful as to 

 shatter the rock through and through (fig. 12, p. 263, and PI. IX, fig. 1), or 

 even to produce breccias (fig. 13, p. 263, and PI. IX, fig. 2), the fragments 

 of which are in some places tolerably well rounded by dynamic action, 

 so as to form pseudo-conglomerates. The fragments vary in size from 

 minute ones to great blocks several feet in diameter. The shattered rocks 

 have been cemented by vein quartz, jaspery quartz, and hematite, some- 

 times one and sometimes two or tlu-ee together (PI. IX, fig. 1). 



