MARYLAND GEOLOGICAL SURVEY 115 



The Lafayette formation, which is represented in this county by 

 several small outliers in the vicinity of Charlotte Hall, usually contains 

 a surface cai^ping of clay loam which, elsewhere in the Coastal Plain, 

 has been quite extensively used for brick. However, in this region, its 

 small areal extent renders it of little value. 



Quaternary Clays. — The clays of the post-Lafayette of the county 

 greatly exceed in value those of the underlying deposits and are 

 found in each of the three Pleistocene members. Their mode of occur- 

 rence is very similar in the 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 ejioch, 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 St. Mary's County, while in 

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



The Sunderland formation contains a greater development of clay 

 loam than it does in Calvert County, and for this reason the upland roads 

 which are generally located on the Sunderland-covered divides are less 

 sandy than in Calvert Count}'. The clay loam of the Sunderland con- 

 stitutes 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 cani 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. 



