MARYLAND GEOLOGICAL SURVEY 125 



of its large percentage of sand, iron, and lime. The lime is derived from 

 the numerous fossil shells which are either generally distributed through- 

 out the sandy clay or massed in definite shell beds within it. 



Quaternary Clays. — The clays of the surficial formations of the 

 county greatly exceed in value those of the underlying deposits and are 

 found in each of tlie lliroe Pleistocene members. Their mode of occur- 

 rence is very similar in tlie different formations as is also their general 

 character. The clays occur in the form of a surface capping of clay 

 loam representing the last stage of deposition in each epoch, and as lenses 

 of light drab to dark brown clay contained in the body of the deposits. 

 In all probability the surface loam was not everywhere developed and 

 often where it was once present it has since been removed by erosion, so 

 that it is by no means co-extensive with the various Pleistocene forma- 

 tions of which it forms a part. It is extremely variable in thickness, 

 ranging from a few inches to 6 or 8 feet in Calvert County, while in 

 other parts of the Coastal Plain it is often much thicker. 



The Sunderland formation contains less clay loam than it does in 

 other parts of the State and for this reason the upland roads which are 

 generally located on the Sunderland-covered divides are so sandy. 

 The clay loam of the Sunderland constitutes the greater portion of the 

 Leonardtown and Norfolk loams whose distribution is shown on the 

 soil map of the county. In many places the materials mapped as loam 

 are entirely too sandy for the manufacture of brick, but in many other 

 places in these areas clay suitable for common brick can be obtained. 

 Where the clay can be used the cost of removal entails only a slight 

 expense because of the small amount of stripping required. Similar 

 clays, utilized in Virginia are obtained by merely removing the few- 

 inches of surface material which is filled with plant roots. 



Beside the surface clay loams, lenses of plastic drab clay are fre- 

 quently found near the base of the Sunderland deposits. These can be 

 seen outcropping in many places on the steeper slopes. In general, 

 these lenses are of small extent but some are sufficiently thick and 

 extensive to be 'worked, although in places they contain considerable 

 vegetable material which renders them less serviceable. Clays of this 



