CHAPTER XI. 



THE PERMIAN PERIOD. 1 



Formations and Physical History. 



After the formations of the Carboniferous group had reached the 

 development already sketched, a general withdrawal of the sea set 

 in, resulting at length (1) in the exposure of those portions of the cen- 

 tral and eastern United States that had been covered by it, at least 

 occasionally, and (2) in the restriction of the submerged area in the 

 western part of the country, an area which had been somewhat gen- 

 erally and constantly covered by the sea during the preceding period. 

 With the beginning of the Permian period, the waters which lay upon 

 the continent were partly in the form of lakes and inland seas, and 

 partly connected with the open ocean. Even the areas which the 

 sea overspread at the beginning of the period were largely abandoned 

 by it before the close. As already noted, the deformative movements 

 which finally resulted in the folding of the Appalachian and Ouachita 

 mountains seem to have been inaugurated at about the close of the 

 Carboniferous period, and these movements were doubtless a main 

 cause of the general withdrawal of the sea. These movements appear 

 to have been more profound than those which shifted the epiconti- 

 nental seas in the preceding periods. 



These movements reflected themselves both in the distribution 

 of the Permian formations and in their character. While fresh- water 

 sedimentation continued much as before in some parts of Penn- 

 sylvania, West Virginia, 2 Maryland, 3 and Ohio, 4 giving rise to the 

 " Upper Barren Coal Measures" — a name which suggests the close 

 connection of these formations with those which preceded — the Appala- 

 chian belt farther south seems not to have been the scene of deposi- 



1 The Permian is often regarded as a part of the Carboniferous. For recent 

 advocacy of this view, see Jour, of Geol., Vol. VII, pp. 321-41. 



2 White, West Virginia Geol. Surv., Vol. II, pp. 100-123. 



3 Martin, Maryland Geol. Surv., Garrett County, p. 144; O'Hara, Allegany County, 

 p. 128, and Prosser, Jour, of Geol., Vol. IX, p. 428. 



4 Prosser, Jour, of Geol., Vol. XI, p. 523. 



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