38 PLANT LIFE IN OKLAHOMA. 



and limestone which extend southeastward nearly parallel with the general 

 course of Rcil River for about 60 miles, gradually increasing ■ in 

 elevation to the east Snd of the range, where the greatest height is at> 

 tained in Mt. Scott, some 1,500 feel in elevation. The pther portions of 

 the State have few local elevations except the conspicuous ranges of 

 gypsum hills through several counties in the western part of the main 

 body of the State (PI. XI). These bluffs and butts often stand con- 

 spicuously above the surrounding regions, but thedr elevations do not 

 exceed that of the more level country lying west of them. 



West of the Gypsum Hills region, the surface is higher and more 

 nearly even, except where cut into valleys and canyons iby the nearly 

 parallel rivers, and the surface of the region passes gradually into the 

 Great Plains at about the 100th meridian. 



Lying along the north side of the valleys of four rivers in the north- 

 western part of the State axe belts of sand hills, ranging from 2 to 18 

 miles in width (PI. A^II). In the counties along the 100th meridian, the 

 sandy regions, in some places, extend on both sides of the valleys, occasion- 

 ally crossing the divides. 



The surface of the strip 15 to 40 miles broad, extending from the 

 southeastern corner of the State westward to about the middle of the 

 south side, is a part of the Gulf Coastal Plain and consists of Cretaceous 

 formations. The surface rocks of some areas in the Panhandle part of 

 the State, and the western parts of Cimarron County, are also Cretaceous. 

 The eastern half of the State, with the exception of the Ouachita and 

 Arbuckle mountain uplifts, and the CretaceoTis area along Red River, is 

 included in the Carboniferous formationsi. The extreme northeastern 

 part of the State, north of the Arkansas and east of Grand River, ia 

 composed of rocks chiefly of Mississippian age, while the remainder of 

 the area designated consists of rooks of Pennsylvanian age. From about 

 the middle line of the State, westward, with the exception of the Wichita 

 Mountain region, and the High Plains area, the rooks belong to the 

 Permian Redbeds. The surface rocks of the High Plains region consist 

 principally of Cretaceous and Tertiary formations, with considerable 

 areas covered by sands of recent age. 



SALT PLAINS. 

 Low lying level sandy tracts varying from one acre to 50 square 

 miles in area and having salt springs at or under the surface are known 

 as salt plains. These are all in the western third of the State, and are 

 mostly located far apart, although in three instances two or three are 

 grouped in rather close proximity. The saline condition of these plains 

 is due probably in all cases to the presence of salt springs.* However, the 

 existence of such springs has not been demonstrated in the Great Salt 

 Plains or United States Saline Reserve, in Alfalfa County ; but the con- 

 stant presence of salt water in the sandy floor even in the summer when 

 evaporation is very great, strongly suggests the presence of saline springs 

 *Okla. Oeol. Sui-vey Bull. No. 11, Chap. VI. page 202. 



