MARYLAND GEOLOGICAL SURVEY 247 



This formation is composed of some of the older Coastal Plain 

 series of deposits, which are capped by a slight covering of late Plio- 

 cene and early Pleistocene gravels. The soils of this formation are 

 derived mainly from the series of stiff, impervious clays, for many 

 years grouped under the head of the Potomac formation. Although 

 the stiff clays are capped by a slight covering of gravelly loam, they 

 are sufficiently near the surface to give character to the soils. The 

 capping on the more level portions consists of from 6 to 10 inches of 

 loose gravel loam. On the slopes and on places where washing is 

 more pronounced the covering of gravel may be removed and the 

 refractory clays are exposed at the surface. Whether or not the 

 gravel is present, the soil of the Susquehanna clay is distinctive and 

 the condition of the countrv extremely desolate. 



Pew attempts have been made at cultivating these soils, and these 

 have generally been unsuccessful. The soil is usually considered too 

 worthless to pay the cost of clearing, and the few attempts made at 

 cultivation have proved decidedly discouraging to the farmer. In 

 some localities small fields of corn and wheat were observed, but the 

 yields are small and the stubborn clays difficult to get in condition. 

 "Wherever this clay is without a gravel covering it is so stiff that it is 

 plowed with the greatest difficulty. Generally clay soils are consid- 

 ered productive, but these prove a notable exception. They are 

 almost impervious to water, and it has been remarked * that so slowly 

 does the water move through them that the growing plant will suffer 

 for want of moisture in the midst of plenty. 



The timber growth of these soils is characteristic and distinct from 

 that of the Susquehanna gravel, with which this formation nearly 

 always comes in contact. Pine and oak constitute the growth, and 

 +he line of demarcation between the Susquehanna gravel and the 

 present formation is well shown by the presence of the pine on the 

 Susquehanna clay. The growth is thick, forming pine thickets rather 

 than heavy forests. The Pennsylvania and the Baltimore and Ohio 

 railroads pass through areas of this formation, the poverty of which 



1 Maryland Experiment Station, Bui. 21. 



