20 C. R. VAN HISE THE PROBLEM OF THE PRE-CAMBRIAN 



it is impossible to separate the Paleozoic and pre-Paleozoic or the Meso- 

 zoic and pre-]\resozoic. In such cases the rocks may be called pre- 

 Mesozoic, pre-Paleozoic, or pre-Cambrian, as the case may be. 



It has been further objected that the classification of the pre-Cambrian 

 is largely based on studies in the Lake Superior and Lake Huron regions ; 

 this is true, but these regions are a part of the greatest pre-Cambrian 

 region of the world, and studies liave gone sufficiently far in other parts of 

 the great Canadian pre-Cambrian area to show that it is ai3plicable for a 

 large portion of the region, and, as will be seen later, to tlie other great 

 regions of the world in which the most extensive studies of the pre- 

 Cambrian have been made (see pages 21-27). 



Specifically it has been objected to the classification that it could not 

 be applied in eastern Canada, where the metamorphism is most extreme — - 

 that is, that it has not been determined to which group the Grenville be- 

 longs. However, if Miller and Knight are correct in their recent con- 

 clusions, it appears that as far east as the Hastings district the dual 

 division of the pre-Cambrian is applicable. In this district the Archean 

 group comprises the Laurentian and Keewatin. The upper series of 

 sediments, to which ]\Iiller restricts the term Hastings, belongs to the 

 Algonkian. The position of the Grenville series of the district below the 

 Hastings yet remains to be certainly determined, and this leaves open the 

 position of the Grenville, of the original Laurentian, and the Adirondack 

 districts. But, considering the rapidity of the progress of the last few 

 years, it is not too much to expect that we shall soon know where to place 

 the Grenville series, and thus be able to distribute all the rocks of these 

 districts between the Archean or Algonkian. 



A final point which may be raised against the dual division of the pre- 

 Cambrian is that we can not Icnow that the plane between the Archean 

 and Algonkian is at the same horizon in geological provinces far removed 

 from each other. This is imdoubtedly true within somewhat narrow 

 limits, but so characteristic are the features of the two groups that I have 

 come to believe that in almost any of the regions which have been closely 

 studied the rocks may be divided between the more ancient group, during 

 which the peculiar conditions resulted in the formation of Archean 

 rocks, and a later group, formed under ordinary circumstances. 



By the above it is not meant to imply that the Archean era ended in 

 all parts of the world at the same time, for this is extremely improbable. 

 But unquestionably the Archean as a whole represents a time the major 

 portion of which antedates the major portion of the Algonkian. We 

 have precisely the same difficulty as to exact correlation in reference to 

 the Paleozoic and Mesozoic, the separation of which is made upon the 



