62 A. p. COLEMAN 



the basement complex is looked on by American geologists as over- 

 whelmingly eruptive in origin. This is by no means the case, however, 

 in the Rainy Lake and Wabigoon regions of Ontario, where in some 

 places the Couchiching sediments cover many square miles and are 

 thousands of feet thick. 



Logically the basal formation should be called the Couchiching, 

 since our time subdivisions in all later formations are founded on sedi- 

 mentary rocks, the eruptives being looked on as, in a sense, accidental. 

 Still we may follow the committee in using the pleasant-sounding name 

 Keewatin, which was given first and has been widely used by other 

 writers since Lawson introduced it, in place of the uneuphonious 

 Couchiching. 



Turning to another point, the suggestion of the committee that the 

 name Laurentian should preferably be confined to granite and gneiss 

 older than the lower Huronian will not commend itself to many Cana- 

 dian geologists. As shown by Professor Willmott and the present 

 writer in the Michipicoten and other districts of northern Ontario, 

 this would cut out the majority of the areas of gneiss and granite named 

 and mapped by Logan and his successors as Laurentian. As they are 

 in some cases the actual rocks which received the name from Logan, 

 and as they occupy an enormously greater area than the similar rocks 

 in the United States, one fails to see why the recognition of the later 

 age of most of these granites and gneisses should be so grudgingly 

 allowed. Why should it be permissible only "in certain cases" and 

 "preferably with an explanatory phrase" to call these rocks Lauren- 

 tian ? Should not the usual relationship be accepted as typical, and 

 the explanation be applied to the older granites and gneisses found 

 in the comparatively insignificant basal complex south of the Great 

 Lakes ? 



This question of the relative age of the Laurentian and the basal 

 sedimentary rocks is evidently rising in other quarters also, as may be 

 seen from Professor Keyes's article on "The Fundamental Complex 

 of the Southern End of the Rocky Mountains,"^ where he evidently 

 looks on all sedimentary rocks as necessarily later than the Laurentian 

 or Archaean. Now that it has been proved that water-formed sedi- 

 ments, sometimes in large amounts, belong to the basal complex and 



^American Geologist, Vol. XXXVI, No. 2, p. 116. 



