654 EDWARD STEIDTMANN 



of the Rainy Lake area, and in consequence of the examination of 

 the Coutchiching series on the east end of Shoal Lake and along 

 parts of the Seine River by the International Committee of 1898. 

 The International Committee found that the so-called Coutchi- 

 ching of Lawson on the east end of Shoal Lake consisted of con- 

 glomerates and other clastic sediments which unconformably 

 overlie the Keewatin. They then concluded that all of the rocks 

 mapped by Lawson as Coutchiching are not below the Keewatin. 



In consequence of Lawson's restudy of 1911, he persists in 

 classifying the rocks of the Rainy Lake area as Archean. He 

 holds to this classification because he regards it as historically 

 correct, having been, he claims, the usage of Logan in his map of 

 the north shore of Lake Huron, and furthermore, he believes that 

 the erosion interval which intervenes between the rocks of the 

 Animikie series and those which precede it is the most conspicu- 

 ous in the pre-Cambrian rocks of the Lake Superior region. He 

 believes that the rocks oh the far side of this erosion interval show 

 greater metamorphism and more intense folding and a larger 

 number of intrusions than those on the near side of this interval. 



On re-examining the Coutchiching rocks on the east side of 

 Shoal Lake, he finds that the conclusions of the International 

 Committee are correct for this particular locality. He finds no 

 evidence, however, to change his original conclusion regarding the 

 Coutchiching which is wrapped around domes of intrusive granite 

 and which dips under the Keewatin at a low angle in the region 

 of Rice Bay and around Bear's Passage. Lawson's classification 

 of the rocks of the Rainy Lake district follows. 



Keweenawan — Diabase dikes 



. , / Granite, porphyritic, and syenite gneisses, and a basic fades of 



^*^"^ \ syenite 



f Lamprophyric rocks 

 Huronian \ Quartzite and slate, and schists 

 (Seine series) [ Conglomerate 

 Laurentian — Granite and granite gneiss 



Anorthite 

 Arrhean Hornblende gabbro 

 Arcneau ^ Lij^gstone (one seam) 

 js^eewatm Qj-gg^stone, greenstone schists, felsite, sericite schist, ash beds, 



agglomerate, sihceous slates and schists, chert, mica schist 

 Coutchiching mica schist, paragneiss, and phyllite 



