LoGan. | The Upper Cretaceous. 225 
feet. The Blue Hills rest upon the Ostrea beds and are composed 
of the Blue Hill shale, capped by a layer of Ft. Hays limestone. The 
surface rises gradually from Glen Elder westward and the prin- 
cipal exposures are of the Ostrea shales. The Niobrara is reached 
near the confluence of Oak creek and the Solomon river numerous 
nodules of the Septaria horizon being found along its bed. In the 
neighborhood of Kirwin Pteranodon outcrops become more numer- 
ous. These Pteranodon beds contain Inoceramus deformis and 
Ostrea congesta. ‘The plains marl of the Tertiary is also found to the 
north and south, but there are no outcrops of the mortar beds. 
Ajiong the Solomon river the outcrops of the Pteranodon beds are © 
numerous, but disappear under the Tertiary formation in Norton 
county. 
The Tertiary—The thickness of the Tertiary formation is 
measured by the depth of the weels. The mortar beds are found 
resting upon the chalk beds of the Niobrara in the eastern and 
central portions of the Tertiary area, and toward the western line of 
the state upon the shales of the Ft. Pierre formation. The mortar 
beds consist of coarse sands cemented by a calcium carbonate 
cement. The plains marl is composed principally of clay, mixed 
with calcium carbonate. The maximum thickness of the Tertiary 
is about three hundred feet. The composition of the water-bearing 
stratum differs with this locality. In many places it is a fine grained 
sand, while in other localities it is found to be either coarse gravel, 
or gravel and sand mixed. The mortar beds are wholly wanting in 
some places. In Jewell county a narrow tongue of the plains mar! 
extends between the White Rock and the Republican to the eastern 
border of the county, but the mortar beds are not found in the 
county. The sheet water here flows over a stratum of the imper- 
vious shale, or chalk, the dip of the surface of which is toward the 
northeast and, consequently, the flow of water is in that direction. 
In many places where the streams have cut down below the levei 
of the shale bed, the sheet water flows out in the form of springs. 
