AREAL GEOGRAPHY OF NORTH AMERICA IN THE LATE PALEOZOIC 257 



The topographic changes resulting from the broad uplift initiated on 

 the eastern side of the continent were accompanied by climatic changes 

 fully as important. Though the continued subsidence of the eastern half 

 of the southern basin may in part have maintained the humid and singularly 

 equable climate, as a local phase, the incursion of the red sediments from 

 the east show that on the higher land a cooler, variable climate, with alter- 

 nate periods of drought and humidity, had set in. The vegetation of the 

 upper Pennsylvanian which is recorded in this basin was very possibly a 

 persistent phase holding over in a locally favorable environment, while the 

 general environment had changed to the new " Permo-Carboniferous condi- 

 tions." Farther west, beyond the limit of red sediments transported from 

 Appalachia, the land gradually rose and the changed climate is only recorded 

 in a few and scattered evidences of erosional activity, terrestrial accumula- 

 tion, and evidences of decreased humidity. Due to the direction of the tilting, 

 sedimentation continued for a longer time in the West under the conditions 

 prevailing in Pennsylvanian time, but in Indiana and Illinois ceased before 

 the "Permo-Carboniferous conditions" had migrated that far west. The 

 result was that the line of changed sediments marking the advance of the 

 climatic change rises toward the \vest across the stratigraphic column and 

 if continuous would lie above the plane of deposition in Illinois and Indiana. 

 (See fig. 7, p. 192.) 



South of the elevation in Missouri, sedimentation terminated within 

 the limits of the Pennsylvanian. No evidence of conditions during Permo- 

 Carboniferous time has been discovered in that region. 



West of the Missouri land and surrounding the southwestern extension 

 of Ozarkia, "Permo-Carboniferous conditions" were coincident with Permo- 

 Carboniferous time. At the close of the Missourian period, which corre- 

 sponds to the upper half of the Pennsylvanian in the Eastern Province, the 

 sea still covered a good part of the Plains Province, and was bordered on 

 the east by the terrestrial deposits and coal swamps which lay on the 

 western slope of the Missouri land. The movements of the sea over this 

 land and its final retreat have been detailed on pages 82-84. To the 

 south the sea bordered on the northern, western, and eastern sides of the 

 southwestern extension of Ozarkia, a good portion of which was finally 

 buried by marine and terrestrial deposits, leaving exposed only the portion 

 now occupied by the Wichita Mountains and the Arbuckle Hills. The 

 eastern side of this portion of Ozarkia was in imperfect connection with the 

 highland of Missouri and northern Arkansas. Coal swamps and narrow 

 stretches of sea covered the lower land at alternate intervals. 



As Permo-Carboniferous time progressed, the sea contracted, and gradu- 

 ally retreated toward central or north central Kansas, where limestone and 

 marine shales continued to be deposited long after terrestrial conditions 

 were established all around the last remnant of the sea. The Plains Province 



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