400 



THE VERMILION IRON- BEARING DISTRICT. 



to differences in composition where such exist. For example, the anorthosite 

 masses usually stand out conspicuously from the surrounding' more basic 

 and less resistant portions of the gabbro. 



The lakes of the gabbro area are, as a rule, shallow, and they are also 

 very irregular, and can not be said to possess uniformity of long extension 

 in any one direction, as is so markedly the case in the lakes of the other 



Fig. 22. — Section through the Rove slates, with intercalated Logan sills south of Gunflint Lake. 



portions of the Vermilion district. On the contrary, they spread out in all 

 directions, sending off numerous bays, some of which are very long and 

 narrow, and all very irregular in shape. 



The Logan sills exercise a very material influence upon the topography 

 of that portion of the district north of the gabbro in which they occur. It 

 will be recalled that the Upper Huronian (Animikie) sediments in this vicin- 

 ity have a monoclinal dip to the south. The sills have been injected essen- 



