42 



The geological series represented in the vicinity are, 

 in descending sequence, according to the nomenclature of 

 Dr. Lawson: 



Algoman 



Irruptive contact. 

 Archaean \ Seine series 



Unconformity. 

 Keewatin. 



Keewatin. 



Exposures of this formation are rather rare in the imme- 

 diate neighbourhood, but occur a short distance north of 

 Atikokan river as part of a N.E.-S.W. belt. The rock 

 types represented are greenstone, gabbro, felsites (quartz- 

 porphyries) and their schistose equivalents. 



Seine Series. 



This consists of a group of rocks, which typically con- 

 sists of dark-coloured micaceous quartzites, quartz slates 

 and greywacke slates, grading into sericitic schists. Their 

 appearance, both on fresh and weathered surfaces is 

 decidedly sedimentary. In other localities they are found 

 to be unconformably above the Keewatin and Laurentian. 



Algoman. 



This is primarily a biotite granite of medium to coarse- 

 grained texture. It varies between granite and syenite types, 

 and usually contains phenocrysts of acid feldspar. Previous 

 to the summer of 191 1 it was mapped by Canadian geolo- 

 gists as part of the Laurentian. But now, in this locality, 

 a small oval-shaped area is differentiated, owing to the fact 

 that it intrudes a well-defined, water-deposited series. 

 It is believed that a considerable part of the rocks mapped 

 as Laurentian in this part of the province is really younger 

 than the Seine series and therefore of Algoman age. 



The area was mapped in 1897 by W. Mclnnes and the 

 late W. H. C. Smith for the Geological Survey as part of 

 the Seine River sheet. Since that time Dr. A. P. Coleman 

 and others have visited the region in connection with 

 studies of the Lake Superior iron ores. The most recent 

 work in the area was done by Dr. Lawson during a visit 



