PRE-CAMBRIAN FORMATIONS— ONTARIO AND MANITOBA 465 



No evidence is given for considering these rocks as volcanic 

 fragmental types, and judging from the description they seem to 

 be normal fine-grained clastic sediments. 



Along the Canadian Northern Railway east of Lake Nipigon,* 

 Burrows found a complex of igneous and clastic rocks, all of which 

 he grouped tentatively as Keewatin. Concerning them he says: 



The age relationship between the mica and quartzose schists of sedimentary- 

 origin and the pillow lavas and other igneous rocks is not known. For the 

 most part the sedimentary rocks stand so nearly in a vertical attitude that 

 their relationship cannot be determined. It seems advisable to group all 

 these rocks with the Keewatin until information is available to show that the 

 sedimentary rocks may possibly be older than the lavas.^ 



Both Burrows and Hopkins classify certain other conglomerate 

 rocks as Temiskamian, but in neither area are the conglomerates 

 found definitely unconformable with the lavas. The correlation 

 is a lithological one in both cases, the later age being assumed from 

 the presence of pebbles of Jasper, greenstone, and granite in the 

 conglomerate beds. 



PEE-CAMBRIAN SECTIONS IN MANITOBA 



Various sections in northern Manitoba have been examined in 

 some detail, and a strip of country extending almost across the 

 province has been mapped. Beginning at the Saskatchewan 

 boundary, where the pre-Cambrian basement emerges from beneath 

 the Paleozoics, a series of three map sheets extends eastward to 

 the Hudson's Bay Railway. Northeast of Lake Winnipeg two 

 areas — the Cross Lake district and the Knee-Oxford Lake district- 

 have been studied. 



Li the most westerly section the oldest rocks are ellipsoidal 

 greenstone and derived schists.^ Supposedly later than these is a 

 thick series known as the Kisseynew gneiss, a garnetiferous, quartz- 

 biotite gneiss apparently sedimentary in origin. There is also a 

 group of slates, quartzites, and conglomerates. The latter are 

 quite evidently the result of torrential deposition probably in 



I Ann. Kept. Ont. Bureau of Mines, Vol. XXVI (1917), p. 232. 



^ Ibid., p. 239. 



3 Mem. 105, Geol. Survey of Canada. 



