THE AECHEAN AEEA. 67 



VICINITY OF THE LAKE OP THE WOODS, KAINV LAKE, AND NORTHWARD. 



Belts of granite, gneiss, schists, quartzites, and slates, Ijeloiiging to the 

 Ai"chean group, alternate with one another, trending to the east or northeast, 

 along the international boundary from the Lake of the \yoods to Lake 

 Superior. Li the region about the Lake of the Woods the}' have been 

 described very fully by Dr. A. C. Lawson.^ The group is there divisilde 

 into two systems, the older being the Laurentian granitoid gneisses, and 

 the newer a series of schists, quartzites, and slates, named bv Lawson the 

 Keewatin series. In later puljlications by Dr. Lawson on the geologv of 

 the Rainy Lake region," his descriptions show that subsequent to the 

 deposition of a measured thickness of 2 miles of mica-schists afid granulitic 

 gneisses, named by him the Coutchiching series, Avell developed about 

 Rainy Lake, and of the Keewatin series north of Rainy Lake and about 

 the Lake of the Woods, the ■\'\'hole Archean g-roup in this district, comprismg 

 a vast thickness of sedimentary and volcanic rocks, and perhaps below 

 these including a part of the first-formed crust of the globe, was subjected 

 to metamorphism froni the heat of the earth's interior, whereb}' the lowest 

 beds observed, to •N^hlcli the name Laurentian is restricted bv Lawson, were 

 so fused that portions of them were extravasated through the overlving 

 Coutchiching and Keewatin beds. Such division remains vet to be worked 

 out for nearly all 'of the Archean area east and north of Lake Winnipeg, 

 but is reported and mapped by Dr. Robert Bell in the country bordering 

 the Hayes and Nelson rivers. 



BOUNDARY OF THE ARCHEAN TOWARD THE AVEST. 



Though the Avestern boundary of the Archean area in Minnesota is 

 mainly covered by drift and by remnants of Cretaceous beds beneath the 

 di'ift, it is somewhat definitely kuoAvn for a distance of 160 miles from New 

 Ulm west, northwest, and north, to the south end of Lake Agassiz. Cross- 

 ing- the Minnesota River from the north at New Ulm, it runs Avesterly about 

 40 miles, and thence northwesterly across Redwood, Yellow Medicine, and 



' Geol. and Nat. Hist. Survey of Canada, Annual Report, new series, Vol. I. 188.5, Part CC. 

 2Am. Jour. Sci. (3). Vol. XXXHI, pp. 473-480, June, 1887. Geol. and Nat. Hist. Survey of Can- 

 ada, Annual Report, Vol. Ill, for 1887-88, Part F. 



