208 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



erosion which must have gone on in this region would have removed a very 

 considerable amount of material, and it is not surprising that any traces of 

 red sediments have been removed and only the deeper material accumulated 

 below the level of ground-water left. 



E. INTERPRETATION OF CONDITIONS IN THE PLAINS PROVINCE. 



The condition of the upland in Missouri, which separated the Eastern 

 and Plains Provinces, has been well pictured in the quotation given on 

 page 82, from Hinds and Greene. The red deposits of the Plain sProvince 

 on its western side are undoubtedly due to climatic conditions very similar 

 to those which prevailed in the eastern province, but their base is at a 

 much higher stratigraphic level than middle Conemaugh. The migration 

 of the climatic change due to the gradual uplift did not make itself felt in 

 the Plains Province until the beginning of Permo-Carboniferous time, well 

 above the Missourian. The difference in depositional conditions in the 

 upper half of the Pennsylvanian in the eastern and western half of the 

 United States has long been recognized. Marine conditions prevailed much 

 longer in the West than in the East and such great swamp areas as char- 

 acterized the eastern basins were never developed. A glance at the typical 

 Kansas section of the western beds shows the successive series of limestones 

 and shales which occupy the same intervals as the shales and coals of the 

 eastern region. In the East the elevation affected a land of swamps and 

 the climatic change superimposed the deposits of semiarid glacial or subglacial 

 condition upon one of singular equable conditions of temperature and 

 humidity; in the west the elevation obliterated or reduced great areas of 

 epeiric seas and the semiarid and cool conditions came upon the surface and 

 the flats of a rapidly disappearing sea. It is easy to understand why the 

 shales and restricted coals of the western area have yielded so few remains of 

 vertebrate amphibian life in comparison with those of the eastern area. 



The source of the material of the red beds of the Plains Province was 

 largely the highlands of the Missouri region, the Ouachita Uplift in Okla- 

 homa, and the Rocky Mountain axis to the west. Schuchert is inclined 

 to think that there must have been a very considerable amount derived 

 from the great Columbia Positive Element of the extreme southwestern 

 part of the United States and the adjacent portion of Mexico. The northern 

 red beds of the Plains Province undoubtedly received a considerable part 

 of their material from the Rocky Mountain axis, but it is possible that some 

 portion came from the northern end of the land exposed in Missouri-Iowa. 

 This suggestion is borne out by the presence of the red deposits near Fort 

 Dodge, Iowa, which, though lower than the typical red beds of the south- 

 west, are at the upper surface of the Missourian. The greater part of the 

 northern portion of the Plains Province is buried under younger deposits 

 and only by inference can the whole of the region be restored. Something 



