Geological Papers. 63 



Ozarks, Arbuckle and Wichita mountains, and probably ele- 

 vated some of the ranges of the Rocky Mountains above the 

 level of the sea. 



About this time middle Kansas experienced the greatest 

 drouth of its history. The water of several great interior seas 

 evaporated, the basins were filled with salt water, the water 

 again evaporated, the basins were filled again with salt water, 

 the water once more evaporated — this process being repeated 

 till hundreds of feet in thickness of rock salt accumulated, and 

 many feet of gypsum, in deposits which extend from King- 

 man to Kanopolis. Next, all that remained of the Kansas- 

 Oklahoma basin was filled with sand and some gypsum, prob- 

 ably from the Wichita mountains and some mountains in 

 Colorado and New Mexico, and the work of the Paleozoic era 

 in Kansas was completed. 



THE AGE OF REPTILES. 



For more than four million years Kansas w^as as level as 

 Iowa is to-daj', and as free from ocean water. Reptiles fought 

 in her swamps and rivers and cycads dominated in her forests. 

 The life of the coal period had largely vanished. Ferns con- 

 tinued in the swampy places, but the great lepidodendrons, 

 sigillaria and calamites, whose fossilized trunks we find in 

 eastern Kansas, are represented by very different descend- 

 ants. The amphibians of the coal swamps of the preceding 

 period had likewise changed to adapt themselves to new con- 

 ditions. The ocean life, also, kept pace with the land life in 

 a general advance to higher structures. 



This Jura-Trias period of three and one-half million years 

 closed in America with the fifth period of mountain-making, 

 this time on the Pacific side. The Sierras, Cascades and 

 several ranges of the Rocky Mountain region were squeezed 

 above sea level. 



For many thousand years after the close of this period of 

 mountain-making the entire plains belt from North Dakota 

 to Texas was covered with a sea of shifting sand that must 

 have drifted from the old Rocky Mountains. This sand became 

 cemented into a sandstone known as the Dakota. 



The Cretaceous system of rocks in Kansas, of which the 

 Dakota sandstone is the first member, consists of the usual 

 alternation of shale, sandstone and limestone, all salt-water 

 formations except the Dakota, The shales associated with the 



