THE PERMIAN PERIOD 661 



sas. 1 The marine Permian of Kansas is overlain by beds containing 

 gypsum and salt, and possessing other features which show that 

 the open sea of the region was succeeded by dissevered remnants, 

 or by salt lakes whose supply of fresh water was exceeded by evapo- 

 ration. With the saline and gypsiferous deposits and above them 

 are the "Red Beds" formerly referred to the Trias; but most of 

 them are now classed as Permian, as are most (though not all) of 

 the Red Beds east of the mountains. Some of the Red Beds in 

 western Texas, New Mexico, and elsewhere are perhaps later than 

 Permian, and some in Oklahoma, Kansas, Colorado, 2 and perhaps 

 elsewhere, are probably older. 



In the Staked Plains of Texas the system has its greatest devel- 

 opment. The oldest part (Wichita formation) indicates that the 

 critical attitude which characterized the surface farther east during 

 the Pennsylvanian period, now affected Texas, for the beds are 

 partly of marine and partly of fresh-water origin. These beds are 

 succeeded by a formation of limestone (the Clear Fork) of marine 

 origin, which overlaps the Lower Permian. The Upper Permian 

 (Double Mountain formation) which follows, indicates a reversal of 

 relations, for much of Texas was again cut off from the ocean, and 

 converted into an inland sea, or into inland seas, in which the 

 phases of deposition common to such bodies of water took place. 

 Occasional beds of limestone with marine fossils point to occasional 

 incursions of the sea, while deposits of salt and gypsum point with 

 equal clearness to its absence, or to restricted connections, and to 

 aridity of climate. 3 



Throughout much of the area west of the Rocky Mountains, 

 the Permian has not generally been differentiated. There is often 

 conformity between the Carboniferous below and the beds classed 

 as Trias above, suggesting the presence of unseparated Permian 

 between. In northern Arizona, however, and in southwestern 



1 For an account of the Permian of this region, see Prosser, Geol. Surv. 

 of Kansas, Vol. II, 1897, pp. 55-97; Knight, Jour. Geol., Vol. VII, pp. 35-74, 

 and Bull. 45, Wyo. Experiment Station, and Jour. Geol., Vol. X, pp. 413-422; 

 Barbour, Nebraska Geol. Surv., Vol. I, p. 129, and Darton, 19th Ann. Kept., 

 U. S. Geol. Surv., Pt. IV. 



2 Cross, Jour. Geol., Vol. XV, p. 633. 



3 For Permian of Texas, see Cummins, Geol. Surv. of Texas, 2d Ann. 

 Kept., pp. 394-424. Ibid., 4th Ann. Kept., 212-232. 



