CLIMATE AND PHYSICAL CONDITIONS OF KEEWATIN 13 

 CONCLUSIONS 



It has been shown in the foregoing pages that the oldest known 

 rocks in Canada, the Keewatin in the west, and the Grenville and 

 Hastings series in the east, stretching for 900 or 1,000 miles across 

 the country, include large amounts of sedimentary materials. 

 Among these rocks are limestones and dolomites, slate of ordinary 

 kinds and also slate charged with carbon, mica schist, and gneiss 

 having the composition of clayey sandstones, arkoses with angular 

 bits of quartz and feldspar, and in a few places also coarser frag- 

 mental rocks. In the east the seas were clearer and deeper, so 

 that limestone predominated. In the west volcanic activity was 

 very pronounced and lava streams, lapilli, and ashes occur on a 

 large scale, either mixed with the water-formed sediments or making 

 up thousands of feet of rock in themselves. 



There must have been great land surfaces from which rivers 

 flowed, bringing down sand and clay. Much of the material sug- 

 gests well-weathered products derived from granite and gneiss; 

 but the arkoses, which are widespread and thick, probably imply 

 a cool and moist land surface. The sea contained plants to fur- 

 nish the carbon, often reaching several per cent in slates, gneisses, 

 and limestone; and the limestones hint at calcareous algae or 

 animals having hard parts. 



All varieties of geological work seem to have been under way 

 in pre r Huronian times as they have been ever since; and there is 

 no evidence of special primeval conditions different from those 

 known to later geology. 



In this paper the earliest Canadian sediments have been dis- 

 cussed from the point of view of climate and physical conditions, 

 and no attempts have been made to marshal the evidence from 

 other lands; but the Canadian Keewatin and Grenville are probably 

 as old as any known rocks, and the same conclusions have been 

 reached from a study of the Archaean rocks of Europe and other 

 continents. Similar sediments penetrated by granites and gneisses 

 occur in the Lewisian of Scotland and the Ladogian of Finland 

 and other parts of Scandinavia. Last summer in Sweden I had 

 the opportunity to study Archaean sediments exactly like our 

 Keewatin, so that the conclusion reached in this paper may be 



