QUATERNARY AGE. 265 



CHAPTER VIII. 



THE QUATERNARY AGE, AND SUPERFICIAL 

 DEPOSITS, CONTINUED. LOESS PERIOD. 



Name. Extent. Thickness. Homogeneous Character. Chemical Char- 

 acter. Analyses. Drainage. Physical Character. Example. Cause of 

 these Peculiarities of the Loess. Fruit on the Loess deposits. Scenery 

 produced by the Loess. Origin of the Loess. Kichthofen's Theory. Recent 

 Advocates of this Theory. Facts bearing out this Theory in the -Nebraska 

 Loess. Objections to this Theory. Root Marks and their depth in the Ne- 

 braska Loess. How Explained on the Subaqueous Theory. Facts learned 

 from Sections in the Republican Valley and South of Plum Creek. Changes 

 of Level Proved, by Fossil Soils in the Loess. Differences in the Present 

 Level of Loess Districts, and its Causes. Land and Fresh Water Shells in 

 the Loess, and How Explained. Stratification of Loess, and its Lessons. 

 True Origin of the Loess. Resume of its History. Missouri Mud, its 

 Analysis and Identity with the Loess. Length of the Loess Period. Re- 

 mains of Man. Climate. List of Shells in the Loess. ^ 



THE LOESS DEPOSITS. 



The Loess deposits first received the name from Lyell, who ob- 

 served it closely along the Mississippi in various places. Hayden 

 frequently calls it the bluff formation, because of the peculiar config- 

 uration that it gives to the uplands which border the flood plains of 

 the rivers. He also frequently calls them marl-beds. This deposit, 

 although not particularly rich in organic remains, is in some re- 

 spects one of the most remarkable in the world. Its value for agri- 

 cultural purposes is not exceeded anywhere. It prevails over at 

 least three-fourths of the surface of Nebraska. It ranges in thick- 

 ness from five to one hundred and fifty feet. Some sections of it 

 in Dakota County measure over two hundred feet. At North 

 Platte, 300 miles west of Omaha, and on the south side of the 

 river, some of the sections that I measured ranged in thickness 

 from one hundred and twenty-five to one hundred and fifty feet. 

 From Crete, on the Burlington & Missouri River Railroad, west 

 to Kearney, on the Union Pacific Railroad, its thickness for ninety 



