FOLDING OP THE SIAMO SLATE. 



315 



sees. 3, 4, .5, 8, and 1), T. 47 X., R. 26 W., are very numerous. The formation 

 here contains much graywacke, and is therefore resistant, and we have a 

 rough and elevated area surrounded by the less resistant iron formation. 

 In the southwesterly extension of the belt prominent exposures occur in 

 the center of sec. 20. In the arm which swings southwesterly from sec. 2, 

 around the Ajibik quartzite, to the sand plain, the outcrops are few, and 

 the land occupied by the belt is low. In sees. 19 and 30 there are numerous 

 exposures, and the area, as a whole, is one of elevation. 



FOLDINO. 



Beginning at the Avest, the northern belt of the formation has, upon 

 the whole, a southern dip. However, when the ledges are examined in 



Fig. 15.— Minor ovtrturneil lolda in Sniniu slate. 



detail, it is found that the rocks are in a set of minor rolls, the dips some- 

 times being to the north, sometimes to the south. The latter are more 

 persistent because of the general south dip of the formation, and therefore 

 more conspicuous (fig. 15). Also, in places where the folds are overturned, 

 the horizontal or northern dips upon the tops of the anticlines and the 



Fig. 16.— Relations of schistosity ami beddiDg in Slamo slatf. 



bottoms of the synclines turn so quickly to the general southwest direction 

 as to be easily overlooked. This is especially true where there is a schis- 

 tosity parallel to the prevalent dip (fig. 16). To the subordinate folding 

 is doubtless due the very greatly varying width of the formation. These 

 minor rolls may be particularly well seen south of the west end of Teal 



