THE BARITE DEPOSITS OF MISSOURI 11 



a sand dune. The alluvial soils are mainly silts, which are in 

 places sandy. 



The smaller valleys contain a certain amount of alluvial soil, 

 but in the main their soils are thin and stony. The origin of the 

 soils is interesting as they are in large part due to side wash from 

 the slopes, which carries the finer materials down into the val- 

 leys. Here the water sinks into the coarse gravels, leaving the 

 fine articles of sand, silt, and clay behind to form the soil. To 

 this is added the material deposited by the stream in times of 

 flood. 



Residual soils 



Residual soils will be classified according to the formations 

 from which they were derived. This will enable the soils from 

 different types of rocks to be compared, and will permit of ready 

 reference to each type. 



Elvins soil. — The areas which were underlain by the Elvins 

 dolomite and shales are so limited that little is known as to the 

 character of the soils derived from them. Some of these areas 

 are along Fertile Creek and the soil is a grayish to reddish sandy 

 loam, but it is probable that it contains some transported material 

 and therefore does not represent the true character of the resi- 

 dual soil : ' .: "Il 



Potosi soil. — Since the Potosi dolomite underlies more than 

 half of the area there was ample opportunity to observe its soil. 

 Likewise the major part of the barite deposits as well as the old 

 lead diggings are found in the mantle rock from this formation ; 

 hence it was studied in detail. 



The surface layer over most of the area varies from dark 

 gray or black thru gray to reddish, while the deep red of the 

 lower part of the mantle rock is exposed at the surface in only 

 a few places. In those areas that have recently been cleared the 

 Potosi soil is usually an ash-gray. The underyling residual ma- 

 terial is everywhere red, usually of a very deep shade. The Po- 

 tosi soil may or may not contain the drusy quartz which is so 

 abundant in the dolomite. The mantle rock ranges in thickness 

 from nothing up to 20 feet, the average being about 10 to 12 

 feet. In most instances the upper foot or two is free from quartz 

 and chert, especially where the slope is gentle enough to prevent 



