550 THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



speak of " sandstones," including those 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 investi- 

 gation. 



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

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

 Palfcozoic 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 

 Archaean rock, but is a Tertiaiy eruptive, granitic, intrusive or axial 

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

 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 once 

 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-fossiliferous 

 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 

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

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

 Tertiary, seems to us entireh^ unreasonable, even from our own point of 

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



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

 the occurrence of an axial mass of granitic rock uplifting rocks of Tertiary age, 

 yet it is nevertheless true. Every feature which ought theoretically to characterize 

 such an occurrence, if it had really taken place, is present in the section offered by 

 the Santa Monica range. The sharp uplifting of the stratified beds in the immedi- 

 ate vicinity of the intrusive mass; the remarkable metamorphic action of the granitic 

 central axis on the adjacent stratified deposits, and the return of them to their nor- 

 mal conditions at a distance from the cause of the ujilift : all this is plainly to be 

 seen, and there is but one explanation for the enacmble of the facts. — J. D. W. 



