138 



THE SOILS OF CALVERT COUNTY 



to the sequence of the formations. Thns the grand divisions of Archaean, 

 Algonkian, Paleozoic, Mesozoic, and Cenozoic are sub-divided again 

 and again. Only strata of the Cenozoic age are represented in Calvert 

 County, so only their sub-divisions will be considered. 



Era. 



Period. 



Group. 



fPIeistocene. . . . Columbia. 



Cenozoic. 



Miocene Chesapeal^e. 



Formation. Soil type. 



Talbot ^ Meadow soil. 



j Sassafras sandy loam. 



Wicomico j Norfolk sand. 



Sassafras loam. 



l-Sunderland . 



Norfolk loam. 

 Leonardtown loam. 

 • •-! Susquehanna gravel. 

 Windsor sand. 

 Norfolk sand. 



.Eocene Pamunkey. 



St. Mary's No soil areas. 



Choptank .| Windsor sand. 



I Norfolk sand. 



Calvert j Sassafras loam. 



Basal clays. 



Nanjemoy No soil areas. 



Aquia No soil areas. 



The oldest strata found belong to the Pamunkey Group of the Eocene. 

 They consist of greensands, which outcrop along the Patu.xent River 

 and its tribiitaries from the vicinity of Ferry Landing northward to 

 the county line. They reach the surface as outcrops which form no 

 surface features and no soils. Over this group is found the Chesa- 

 peake (of Miocene age) which is sub-divided into three formations. The 

 lowest, the Calvert, occurs at the surface in the form of a modified type of 

 Sassafras loam. For the most part its chief role is to form the basal 

 structure upholding the soil proper of the county. 



Tlie next formation, the Choptank, is composed of fine and medium- 

 grained sands and contains marl beds. The surface exposures con- 

 tribute to the Windsor sand and form the main part of the Norfolk sand. 

 Above the Choptank occur the St. Mary's strata, which form no extensive 

 surface feature and thus give rise to no soil type. 



