RESUME OF LITERATURE. 119 



of Tower and Ely on the Vermilion iron range occur in the upper part of 

 the Lower Keewatin. It is probable that the immediately inclosing rock 

 is a sedimentary one, although composed of the elements of a basic erup- 

 tive. The sediments extend south to the Giants range of granite, where 

 they are metamorphosed to mica- schists by the granite. Toward the west 

 they extend as far as the Mississippi River and its northern tributaries and 

 across the Bowstring, althoug-h the drift prevents the delimitation of the 

 belt. To the northwest they extend toward Rainy Lake, in this direction 

 being converted into mica-schists and gneisses by the intrusion of granite; 

 in unmodified form they are found at one point only on Rainy Lake. 

 These fragmental rocks of the Lower Keewatin doubtless also underlie 

 most of the central and southwestern part of the State as far as the Minne- 

 sota River. Here they dip beneath the later formations in the southwestern 

 portion of the State, and probably occupy a wide patch in South Dakota. 

 South of the Giants range they occm- also, biTt as they are covered by the 

 gabbro and Animikie toward the east and the di'ift deposits of the St. Louis 

 Valley toward the west their geographic boundaries are mostly unknown. 

 Thev appear in the central and western jiortions of Carlton Coimty, where 

 their line of separation from the Upper Keewatin is quite obscure, and in 

 the central and western portions of Morrison County. The Lower Keewatin 

 marble is seen at Ogishke Muncie Lake and at Pike Rapids on the 

 Mississippi. 



The Lower Keewatin was terminated by a period of extensive folding 

 and intrusions of granite and basic rocks. 



The Pewabic quartzite belongs with the Keewatin, but whether to the 

 Lower or Upper Keewatin is not known. This formation includes altered 

 quartzites and iron ores between the granite and gabbro in the immediate 

 vicinity of Birch Lake and small patches of similar i-ocks in sec. 30, T. 62 

 N., R. 10 W.; on the soiith shore of Disappointment Lake; on the north 

 shoi'e of Fraser Lake; on the south shore of Gobbemichigamraa; at Akeley 

 Lake, forming the so-called Akeley Lake series extending from the west side 

 of sec. 34, T. 65 N., R. 5 W., to the eastern part of sec. 27, T. 65 N., R. 4 W. 



The Upper Keewatin occui-s in troughs in the Lower Keewatin, and 

 particularly in one main trough the axis of which is traceable from Vermil- 

 ion Lake to Saganaga Lake. The northern arm of this syncline, consist- 

 ing of granites, gneisses, associated mica-schists, and in some places earlier 



