I s '-' L C. LAWSON — RELATIONS 01 I II I IRCHE AN OF CANADA. 



conformable upon the Laurentian; the assumption being always that both 

 assemblages of rocks were composed of metamorphosed sediments. The 

 answer was held to binge upon the parallelism or absence of parallelism 

 between the foliation of the Laurentian granites and syenites and the planes 

 • it' bedding and schistosity of the rock- which are in contact with them. Bell, 

 Dawson, Selwyn, and McKellar contended for a conformable sequence. 

 ! . gan is silent on this question, hut seems to have been in no doubt as to the 

 unconformable superp isition of the true Huronian of Lake Huron upon the 

 Laurentian. limit has always contended for an unconformity, hut as he 

 also had in mind the true Huronian, which he once regarded as Cambrian, 

 his contentions do not seem to apply to such rocks as are clearly Archean 

 and intimately involved with the Laureutian gneisses. It is therefore fair 

 to say that the drift of opinion in Canada, and probably also in the United 

 States, is in the direction of conformable sequence throughout the Archean, 

 without a break between the lower (Laurentian) and upper (Ontarian) 

 systems. This \ iew has recently been emphatically endorsed by Professor 

 Alex. Winchell a- a result of his observations in northern Minnesota. 

 Dawson ha- recently, as a result of his studies of analogous conditions on 

 the Pacific coast, thrown over his earlier opinion- ;i- to the conformable 

 lence between these two divisions of the Archean on the Lake of the 

 Woods, and i- now in accord with the writer as to the natureof the relation- 

 which obtain there, and which will be set forth in the sequel.f 



Irruptivt Contact on Lake of the Woods. — Up to the date of the publication 

 of the writer's report on the geology of the Lake of the Woods I s " 

 the possibility of any other relationship between the two greal divisions of 



the Archean than those of ( fortuity or unconformity do not seem to have 



been entertained. In that report the writer pointed out that the relation- 

 ship was one of neither i formity nor unconformity, hut id' an entirely dif 



ferenl order. Evidence was adduced in some detail to show that the condi- 

 tions of the eoni act I >et ween the | j\\ w rei 1 1 ja ii a n d t he I\ eew a t i n are essentially 

 those which obtain between any Paleozoic or later intrusion of granite and 

 the bedded rocks through which ii breaks. The contact was shown to be 

 a brecciated one, the granitoid gneiss ramifying through the schists in 

 apophyses, h >th transverse and parallel to the strike of the schist, and hold- 

 ing in abundance fragments from tin Keewatin formations, which had clearly 



■ 



been broken off from thi latter while it was in a hard and brittle state and 

 had found their way into the Laurentian often for considerable distances 

 from the contact, as well as rn »re n itably in it- proximity. The conditions 

 observed indicate clearly that we had no question of conformity or uncon- 

 formity to deal with, hui with ih" contact of an irruptive L r u sous mass, of 



pp, 181, 1 lOth An- 



il ii ii I 



\ '.i it 



