28 C. E. VAX HISE THE PROBLEM OF THE PEE-CAMBKIAX 



It has also been suggested, but, so far as I kno-w, never in print, that 

 the term Proterozoic be extended to the bottom of the c-olimm, and that 

 the two divisions of the Proterozoic thus defined be Earlier and Later. 

 This proposal would amount to an indirect dual division of the pre- 

 Cambrian emphasized in this paper. Such usages would simply intro- 

 duce other terms for the major divisions of the pre-Cambrian having a 

 meaning equivalent to that of Archean and Algonkian. The only result 

 of the acceptance of the proposals, so far as I can see, would be the avoid- 

 ance of these terms. The ideas of those who as a result of many years' 

 work have formulated the fimdamental principles upon which the division 

 of the pre-Cambrian is based would be taken, but their terms rejected 

 and other terms introduced in their stead which, as terms merely, are 

 very objectionable. 



In closing I wish to express my strong belief that the dual division of 

 the pre-Cambrian into two great groups of rocks seems now as firmly 

 established as the division between an}- other two groups; indeed, the 

 major contrasts between the Archean and Algonkian, in the character of 

 the rocks and the earth conditions which they represent, are probaljly 

 greater than between any other two. The only other two which have 

 anything like such contrasts are the Algonkian and the Paleozoic, and 

 this diiference is not in the nature of tlie materials or the physical condi- 

 tions obtaining during their depositions, but in the absence of definitely 

 recognized life forms in the older and the presence of a highly developed 

 fauna in the newer. Also the division of the Archean into Laurentian 

 and Keewatin is firmly established, and Archean is entitled to a group 

 place in the geological column. 



It is also clear that the Algonkian should have the place of a group in 

 the geological column. The succession includes four unconformable 

 series for at least two regions, and. according to Sederholm, five in Fin- 

 land. If in the futiire it is possible to divide the Algonkian on a sys- 

 temic basis, as the Paleozoic has been divided into Cambrian, Silurian, 

 Devonian, and Carboniferous, this should be done. If this can be accom- 

 plished, the terms Huronian, Animikean, Keweenawan, etcetera, would 

 become S3'stemic terms. 



Finally, I may say that the working out of the criteria under which 

 the Algonkian may be divided into series which may be correlated from 

 province to province is the great problem immediately before the pre- 

 Cambrian stratigraphical geologist. Considering the progress which has 

 been made in the past, this problem should by no means be regarded as 

 hopeless. TThen solved the stratigraphy of the pre-Cambrian formation to 

 Archean time will be placed on as satisfactory basis as the post-Cambrian. 



