ON THE LAKE SUPERIOR REGION 97 



between the two series become perfectly clear. Great blocks of 

 the Keewatin are included in the granite, the masses varying from 

 those of small size to others of enormous bulk. Also the two have 

 intricate relations, which have perhaps been best described as lit 

 par lit injection. In short, the relations are those so well described 

 by Lawson for this area. 



In the Thunder Bay district we visited especially the areas about 

 Loon Lake and Port Arthur. In the Loon Lake area the succession 

 is as follows: The top series is the Keweenawan, here consisting of 

 sandstone above and conglomerate below, with interbedded basic 

 igneous flows or sills. Below the Keweenawan is the Animikie. The 

 contact between the Keweenawan and the Animikie was seen at two 

 places. At one of these there is an appearance of conformity, but 

 at the other the eroded edges of the Animikie iron-bearing formation 

 are traversed by the Keweenawan beds. At one contact the base of 

 the Keweenawan rests on the Animikie slate, interstratified with the 

 iron formation, and at the other on one of the members of the iron- 

 bearing formation. At both localities the conglomerate at the base 

 of the Keweenawan bears detritus from the underlying series, includ- 

 ing both the slate and the iron-bearing formations of the Animikie. 

 The Animikie succession which we saw near Loon Lake includes 

 two phases of the iron-bearing formation with an interstratified 

 belt of slate. The x\nimikie here has in general rather flat dips, 

 although locally they become somewhat steeper. 



Near Port Arthur the higher slate member of the Animikie was 

 visited by a portion of the party, and on previous occasions had 

 been visited by the other members. This is the formation which is 

 agreed by all to rest upon the Animikie iron formation. It is notable 

 as containing the intrusive sills called by Lawson the Logan sills. 



At one place near Loon Lake a test pit has been sunk to the 

 bottom of the Animikie, and here at the base of the formation is a 

 conglomerate bearing fragments of the next underlying series — a 

 graywacke slate. This graywacke slate covers a large area, shows 

 cleavage at a high angle, and is evidently an important formation 

 in the district. 



The party has no doubt that there is considerable unconformity 

 between the Keweenawan and the Animikie, and a very important 

 unconformity between the Animikie and the graywacke slates. 



