550 THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



speak of " sandstones," including thosa of all geological ages, but in 

 such connection as would make the fact that the rock was sandstone the 

 only point of importance with reference to the question under mvosti- 



gation. , 1 A • ;i 



We would then call the eruptive rocks associated with tho Azoic, and 



which took their position in that formation before the deposition of tho 



Pala)ozoic formation upon, them, Azoic eruptive, designating the special 



rock by its lithological name. To the eruptive rocks of later date, we 



would respectively give the designation corresponding to that of the 



age or period when those rocks assumed their present position. 



The granitic axis of the Sierra Santa Monica, therefore, is not an 



ArchKan rock, but is a Tertiary eruptive, granitic, intrusive or axial 



rock, because it took the position in which we now see it during tho 



Tertiary epoch.* 



We come now to the second branch of our inquiry ; namely, to the 



consideration of the question whether the Azoic series can properly be 

 separated into two or more divisions, as has been done by the Canada 

 Survey and by those who have followed its lead. 



If we adopted the views and nomenclature of Dana we should at onm 

 admit that a division of the Azoic (Archaean) into two distinct groups 

 was not only desirable, but imperatively necessary, since we can conceive 

 of nothing more unphilosophical than placing stratified fossiliferous rocks 

 in the same category with non-stratified and necessarily non-fossdiferoua 

 ones. To designate by the same term the stratified deposits of Lake. 

 Superior, which have remained as they now are since a time prior to 

 tho deposition of the Lower Silurian, and the eruptive granitic axis of a, 

 range which was not in existence until after the close of tho Miocene 

 Tertiary, seems to us entirely unreasonable, even from our own point ot 

 view, namely, that the Lake Superior rocks are in fact Azoic : how much 

 more so, then, from the standpoint of Dana, who considers these same 



rocks to be fossiliferous ! 



If tho Azoic rocks are really azoic, as we believe, then it follows, as, 



* Altliougli some geologists and lithologists are unwilling to accept the fact of 

 the occnrrenee of an axial niasB of gr.nitic rock uplifting rocks of Tertiary ngo 

 yet it is ncvertliclcss true. Every feature which ought theoretically to charact nzc 

 such an occurrence, if it had really taken place, is present in the -«*-" ""^^"'..Jf 

 the Santa Monica range. The sharp uplifting of the stratified beds m tjc in u d 

 ate vicinity of the intrusive mass, the remarkable rnetamorphic action «f tl>« g™ ^ " 

 central axis on the adjacent stratified de,,osits, and the return ot them to thai nor 

 mal conditions at a distance from the cause of the uplift : all this is p^ain^y to be 

 seen, and there is hut one explanation for the enscmhU of the facts. - J . D. w . 



