SURVEYS BY THE UNITED STATES BUREAU 123 



LIMESTONE VALLEYS AND UPLANDS 



The limestone soils are among the most extensively developed of any in the 

 United States and occur in both broad upland and inclosed narrow valley areas. 

 The greatest upland development is seen upon the Cumberland Plateau in 

 eastern Tennessee and Kentucky and upon the Carboniferous formation in 

 central Tennessee and Kentucky, northern Alabama and Georgia, and in 

 Missouri. The valley soils are found principally in Pennsylvania, Maryland, 

 and Virginia, and in the mountain section of eastern Tennessee and Kentucky 

 and northern Alabama and Georgia. The topography of the plateau soils 

 varies considerably. In the Cumberland Plateau and Highland Rim the sur- 

 face is undulating ; in the region of the Ozark uplift in Missouri and Arkansas 

 it is quite rough and hilly, and where there is an elevation of the surface, or 

 where the plateau is deeply dissected by erosion, it presents a quite mountain- 

 ous topography. The valley soils of the Appalachian region also show consider- 

 able topographic relief, sometimes exhibiting mountainous surface features. 



The limestone soils are residual in origin, being derived from the weather- 

 ing in place of limestone of differing age and composition. This is accom- 

 plished by the removal through solution of the calcium carbonate of the lime- 

 stone, leaving behind the more resistant siliceous minerals. These soils are 

 remarkable for the fact that they contain but a very small percentage of the 

 original limestone rock, the larger part having gone into solution. It has 

 thus required the solution of many feet of rock to form a single foot of soil. 

 Thus far the limestone soils east of Kansas and Texas and north of central 

 Alabama and Georgia have been grouped in two important series, known as 

 the Hagerstown and Clarksville. 



Clarksville series. Light gray to brown soils with yellow to red subsoils, 

 derived mainly from the St. Louis limestone. While not as strong as the 

 Hagerstown soils, this is a valuable series. Apples and peaches are commer- 

 cially important. Tobacco is a leading product. General farming is firmly 

 established in many extensive regions. 



Cumberland series. Brown surface soils, derived from thin deposit of 

 sedimentary material overlying residual limestone subsoils. Used for cotton 

 and other general farm crops, truck and fruit. 



Decatur series. Reddish brown to red soils with intensely red subsoils. 

 Intermediate in value between the two series just described. Cotton, corn, 

 wheat, oats, forage crops, blue grass, and peaches are the leading crops. 



Hagerstown series. Brown to yellowish soils with yellow to reddish sub- 

 soils, derived from massive limestone. Among the most productive soils of 

 the eastern United States. Fine wheat and general farming soils, and the 

 seat of important apple orcharding interests. Blue grass is indigenous. 



GLACIAL AND LOESSIAL REGIONS 



The soils of the glaciated part of the country constitute one of the most 

 important groups in the United States. The group includes all soils derived 



