110 THE VERMILION IRON-BEARING DISTRICT. 



which are gently slopmg on the south sides, and steep on the north. 

 This topography has led Lawson to the conclusion that the apparent 

 large number of sills is due to monoclinal faulting of fewer layers, 

 but of this there is no evidence. The Animikie strata are divided as 

 follows: An upper or graywacke-slate member, 1,900 feet thick, com- 

 posed of slates and graywackes, with fine-grained quartzites and quartz- 

 slates; a middle or black slate member, 1,050 feet thick, composed mainly 

 of black slates, apparently carbonaceous, with a fine-grained, siliceous and 

 flint}^ layer at the base 60 feet thick; and a lower or iron-bearing member, 

 composed largely of jaspery, actinolitic, siliceous, and magnetitic slates, 

 usually thinly laminated, and some beds of cherty iron carbonate. 



The Akeley Lake rocks, first called Pewabic quartzite, are similar to the 

 Gunflint iron-bearing rocks, and different from the Pewabic quartzite and 

 conglomerate found at the base of the Animikie farther west on the Mesabi 

 range. From the new data obtained, the Akeley Lake iron-bearing rocks, 

 which rest directly upon the Keewatin, are placed as the iron-bearing 

 member above the Pewabic quartzite. 



Elftman, a. H. Preliminarj^ report of field work during 1893 in northeastern 

 Minnesota: Twenty-second Ann. Rept. Geol. and Nat. Hist. Survey of Minn., for 

 1893, 1894, pp. lil-180. 



This contains many details concerning the structure and character of 

 the rocks north and west of Snowbank Lake. A section is given from 

 Moose Lake to Snowbank Lake, showing relations of rocks in the 

 intervening area as determined by him. 



Interest centers in the porphyry and granite. The porphyry is the 

 oldest eruptive. It is found sending long apophyses across the strike of 

 the Keewatin rocks, and contorting and metamorphosing them. On Snow- 

 bank Lake there are two granites, a red hornblende- and a gray augite- 

 granite, formerly known as red syenite and gray syenite, respectively, 

 which are considered as having been derived from parts of the same 

 magma. The gray augite-granite is not found in contact with the sedi- 

 ments. This augite-granite, the poi'phyry referred to above, and also the 

 sediments are cut by the hornblende-granite. Where the sediments are 

 cut by the granite they are metamorphosed to schists. 



In connection with the preceding it might be of interest to note that, the 

 hornblende and mica schists of Snowbank and White Iron lakes grade into argilla- 



