Archean 



394 E. M. BURWASH 



discussion of the relations of the two areas with one another and 

 with the surrounding regions. 



Lawson's general statement of the geological sequence of the 

 Lake Superior region is as follows: 



f Keweenawan 

 Algonkian < Unconformity 

 [ Animikie 



Eparchaean Interval 



Algoman granites, gneisses, etc. 



Irruptive contact 

 Upper Huronian 



Unconformity 

 Lower Huronian 



Unconformity 

 Laurentian granites, gneisses, etc. 



Irruptive contact 

 Keewatin \ r\ ^ • 



iCoutchiching jOntarian 



The Algonkian formations need not concern us for the purposes 

 of this paper, although dikes exist in some of the areas considered 

 which may be of Keweenawan age. 



The region around Lac Seul and northward as interpreted by 

 the writer from data collected in 1919 includes the following geo- 

 logical sequence:^ 



4. Younger porphyritic granite (Birch Lake River). 



3. Older red and gray, sometimes gneissoid granites. 



2. Upper sedimentary and schist series, including a (basal?) 

 conglomerate, hornblende schist and other schists and possibly 

 limestones and quartzites.^ 



Lower volcanic and schist series, including more or less altered 

 volcanic rocks of rhyolitic, andesitic, and basaltic types, frequently 

 ellipsoidal in structure, hornblende schists, in part ferruginous, 

 and some jaspylite. 



I. The lowest member of this succession is correlated with some 

 confidence with the Keewatin of Lawson on account of its litho- 



^ But see the Report of the Department of Mines of Ontario, Vol. XXIX, Part i 

 (1920), p. 181, for an alternative classification. 



^ The two last were not seen by the writer. See C. B. Dowling, Geol. Siirv. Can., 

 Vol. VII, Part F. 



