4 8 



distance south of the lake, and along the Canadan Northern 

 Railway line in the vicinity of Atikokan. 



Structure of the Area. — A good partial cross-section 

 of the Steeprock series is exposed along a line from the 

 west side of Strawhat lake to the east side of East bay. 

 In this section, a twofold repetition of the same set of 

 beds in reverse order is evident. The general strike is 

 N.W.-S.E. On the east, the conglomerate is in visible 

 contact with the Laurentian, while on the west it rests on 

 the Keewatin basement. The structure which has been 

 worked out for the area by Dr. Lawson is that of a simple, 

 closely folded syncline, whose axis is parallel to East bay, 

 and whose trough covers the contact of the Laurentian 

 and Keewatin. 



In contrast with the folded condition of the Steeprock 

 series is the uniform monoclinal attitude of the Seine 

 quartzites and quartz slates. This stratigraphical and 

 structural relationship indicates that the folding, which 

 involved the Steeprock series as a sharp trough sunk 

 down into the older Archaean, had taken place anterior 

 to the deposition of the Seine series. It is therefore inferred 

 tentatively that the Steeprock series is older than the Seine 

 series. 



The distribution of the Steeprock series and of its lime- 

 stone and basal conglomerate members, as far as they have 

 yet been differentiated from the Keewatin, is shown on 

 the accompanying map. The exposures in the southwest 

 corner on Seine river are a brownish calcareous schist, 

 not unlike that on the south shore of Falls bay. They are, 

 however, very closely associated with Keewatin felsites, 

 and may be either Keewatin in age or infolds of the Steep- 

 rock limestone. 



The areal geology, indicated on the map, is only approxi- 

 mate, as detailed surveys have not yet been made. 



Progress of Exploration. The geology of the area, on 

 account of the features of especial interest which it presents, 

 has received considerable attention from the Geological 

 Survey of Canada and other sources. In 1891, H. L. 

 Smyth (10) published an interesting set of results obtained 

 from an examination of the area. W. Mclnnes and the late 

 W. H. C. Smith (4) of the Survey mapped the region as 

 part of the Seine River sheet in 1897. Dr. A. P. Coleman 

 visited the area and published an interesting account of the 

 geology in 1898 (2). In 191 1, Dr. Lawson spent some time 



