QUATERNARY AGE. 253 



Glacial Period. 



The monuments of this period are undoubted. Along the Mis- 

 souri River, from Fort Calhoun to the Kansas line, wherever the 

 superficial deposits are removed and hard limestones constitute the 

 surface rocks, they are worn as smooth as mirrors, except diamond- 

 like scratches which cross them in a direction averaging about 17 

 degrees east of south. Below Plattsmouth at one point they run 27 

 degrees east of south. On the Platte, as far west as the limestone 

 extends, the direction east of south averages about 19 degrees. 

 At Stout's former stone quarry, twelve miles southeast of Lincoln,, 

 the direction is 13^ degrees east of south. These markings at 

 this quarry seem to cross fainter lines whose direction was a little 

 more easterly. In other places these slightly divergent lines are 

 found, as if the ice in glacial times had moved at first more easterly 

 than it did later. Where the rocks are of a soft, yielding nature, 

 as in the Cretaceous and Tertiary these lines have long since been 

 effaced. That they once existed is more than probable. On the 

 Niobrara at a few points where a hard, silicious layer of Cretaceous 

 rocks but recently was exposed to the surface, faint glacial lines 

 were visible. As such markings are now made by existing gla- 

 ciers, all geologists refer these scratches to a similar origin. 



The materials lying on the country rock over the greater part of 

 the State are additional evidences of the former presence of glaciers 

 on our plains. The following section, taken on Oak Creek, Lan- 

 caster County, shows the character of the materials laid down dur- 

 ing this age. The section begins at the top. 



1 . Black surface soil ... 4 feet.. 



2. Loess 21 " 



3. Calcareous sand 7 " 



4. Gravel, sand and drift boulders 5 " 



5. Black soil, with silicifled wood 2 " 



6. Gravel and boulders 4 " 



7. Modified drift-gravel and clay 9 " 



8. Blue clay .JL7 " 



69 feet. 



Farther up the valley of Oak Creek a bed of blue clay exhibited 



the following characters. It lies on the deposits of the Dakota Group. 



1 . Blue clay 5 feet. 



2. Sand 1 " 



3. Blue clay 13 " 



4. Fine sand and gravel y 2 " 



5. Blue clay .11 " 



30^ feet. 



