61G E. O. ULRICH KKVISION OF THE PALEOZOIC SYSTEMS 



sufficient length in preceding parts of this work. (See especially pages- 

 54() io 550.) From these statements and otliers tluit are to tollow it is 

 clear that the Ozarkian in this province is not only sharply distinguish- 

 able from the Cambrian below, but also from the Canadian, or, if this is 

 absent, from the Ordovician above it. It should be apparent further that 

 the importance of the Ozarkian, as determined by such criteria as rela- 

 tive volume of sediments, their time value, and areal distribution, is 

 scarcely if at all inferior to that of the Cambrian or, indeed, any other 

 system found in America. Counting up the maximum thickness of tho- 

 several formations assigned to the Ozarkian in the Appalachian region,, 

 the aggregate is certainly not less than 6,000 feet. Considering that all 

 of this great thickness of sediment is composed of dolomites and lime- 

 stones, it surely seems that on this ground alone the Ozarkian is entitled 

 to rank as a distinct system. That is has its own well marked fauna 

 has been stated above. We need but to add that its diastrophic history 

 is complete in itself, and, though different in details, comparable in its 

 stages to those recognized in other fully developed systems. Besides, it 

 is separated from the Cambrian below and the Canadian above by long- 

 emergent stages that are indubitably recorded in every competent sec- 

 tion that I have had an opportunity to study. If these features are not 

 the attributes of a geological system, then stratigraphy is less of a science 

 than 1 think it. 



Major dirisioiifi of f/ic Cniiihrian. — Tlie (^uubrian system in America 

 is usually divided into three series: (1) the lower Cambrian, rather 

 generally known as the Georgian; (2) the middle Cambrian or Acadian, 

 and (;0 the upper Cambrian, for which the geographic term Sara- 

 togan, on the grouiulless belief of their equivalence, has in recent years 

 gained wide acceptance. The loAver Cambrian, for which 1 hesitate 

 to use the alternative term Georgian, because the same name was orig- 

 inally proposed, and is even now in use, for a subordinate part (Georgia 

 slate) of the lower Cambrian,*^^ evidently attained its greatest known 

 development in the Cordilleran trough. Walcott has measured and 

 published descriptions of a number of good sections in Nevada, Cali- 

 fornia, Utah, and British Columbia,"^* the series in each case being sub- 

 divided into formational units based on lithologic criteria. As yet the 

 stratigraphic and faunal histories of tliese several outcrops are insuffi- 



"•' 1 liad considered the advisabiUt.v of using Taoonian in place of Georgian, but found 

 many vaUd objections to the revival of Emmons's term Taconic in any sense. Doubtless 

 a much better name for the series would be Saflford's term Ohilhowee. 



'"* C. L). Walcott : Cambrian sections of the Cordilleran area : Smithsonian Miscella- 

 neous (Collections, vol. liii. lOOS. 



