64 



SOIL PHYSICS AND MANAGEMENT 



to dry. It was then picked up by the wind and carried over the 

 upland. This lowan loess was very extensive, reaching as far east 

 as southwestern Ohio, north into Wisconsin, and as far south as 

 Louisiana on hoth sides of the Mississippi Jiiver. 



Loess is quite uniform in texture, consisting primarily of par- 

 ticles of silt mixed with fine sand and a small amount of clay. Since 

 much limestone was ground up by the glaciers, the loess contains a 

 large proportion of carbonates, as much as 28 per cent in some 

 cases. The percolating carbonated water has dissolved the car- 

 bonate from the upper part and carried it downward, depositing it 

 in the form of concretions of various sizes and shapes as shown in 

 figure 61. Some of these are tubular. It is probable that these were 

 formed in the openings left after roots had decayed. Concretions 

 of iron are formed occasionally. 



The deeper loess deposits show characteristic vertical cleavage 

 and cuts through this maintain vertical walls for long periods of 

 time (Fig. (52). Terrestrial shells, such as snails, are frequently 

 found in the deeper deposits, with an occasional fresh water shell. 



The following table gives the analysis of loess from different 

 sources for comparison with a dust fall in Indiana: 



Physical Analysis of Loess ami Dust * (Grades of Bureau of Soils) 



The chemical analysis of five samples from different places is 

 given in the next table. Note the amount of lime and magnesia. 

 The deposit is usually characterized by a large amount of car- 

 bonate. 



