So REVIEWS 



The greenstone, designated the Kawishiwin, is the oldest known 

 rock in the state, and is supposed to represent a portion of the original 

 crust of the earth. With its associated volcanic rocks it occurs in two 

 main belts. The southern belt begins in the vicinity of Gunflint Lake 

 and extends westward by way of Gobbemichigamma Lake, the Kawi- 

 shiwi River, and White Iron Lake, to Tower, and indefinitely westward. 

 The northern belt of greenstone enters the state from Hunters' Island, 

 appearing conspicuously at the south side of Basswood Lake. At 

 Pipestone Rapids and Fall Lake it widens southward and apparently 

 unites at the surface with the southern belt, the overlying Upper Kee- 

 watin being absent for a distance of a few miles. But further west it 

 is again divided by the Stuntz conglomerate, the northern arm running 

 to the north of Vermilion Lake, west of which its extension is unknown, 

 and the southern one running south of the lake. 



The fragmental stratified rocks of the Lower Keewatin are most 

 important toward the western part of the area of exposure of crystal- 

 line rocks. They occupy a wide area, south, west, and north of Tower. 

 The iron ores of Tower and Ely on the Vermilion iron range occur in 

 the upper part of the Lower Keewatin. It is probable that the imme- 

 diately enclosing rock is a sedimentary one, although composed of the 

 elements of a basic eruptive. 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, although 

 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 frag- 

 mental rocks of the Lower Keewatin doubtless also underlie most of 

 the central and southwestern part of the state as far as the Minnesota 

 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 occur also, but as they are 

 covered by the gabbro and Animikie toward the east and the drift 

 deposits of the St. Louis valley toward the west their geographic 

 boundaries are mostly unknown. They appear in the central and 

 western portions of Carlton county, 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 



