Provincial Carboniferous Terranes. 309 



In point of the time taken for its formation, the Missourian 

 series may be regarding as ranking with the Mississippian. 



The so-called Permian of the Western Interior basin (Okla- 

 homan and Cimarron, the latter generally known as the Red 

 Beds) is composed largely of shales and shaly sandstones. 

 Unusual conditions prevailed during the formation of these 

 beds. In the main, the deposits indicate the presence of shal- 

 low waters, in strong contrast to the marine conditions which 

 prevailed previously in the same region. The sediments were 

 laid down largely in more or less closed basins, which may 

 have often had access to the sea, but which finally became 

 altogether dry. 



The conditions existing were identical with those under 

 which the original Permian beds of Russia were formed.* 

 IS r oth withstanding the comparatively great development of the 

 beds of these series, the formation of them was evidently rapid. 

 The time occupied was probably not more than twice as long 

 as that of the Missourian. 



Careful comparison of all available data indicates that the 

 actual time ratios for all the series is very nearly equal. All 

 things considered, this appears quite remarkable. The values 

 seem best to accord with the following figures : 



Cimarron 1 



Oklahoman 1 



Missourian 1^ 



Des Moines ._ 1 



Arkansan 1 



Mississippian 1^ 



* Journal Geology, vol. vii, 1899, p. 320. 



