MAKYLAXD GEOLOGICAL SURVEY 155 



sources. The lowest member of the Chesapeake Group, the Calvert, 

 is made up of beds of diatomaceous earth and clay, and where these 

 reach the surface the resulting soil is a slightly sandy loam derived 

 directly through the action of atmospheric agencies upon the clay and 

 diatomaceous earth. The areas of soil tluis formed arc found along 

 the slopes of stream valleys and are usually merely long narrow 

 strips of a heavier soil separating the higher, sandy soils from low, 

 sandy terraces, or from meadow lands in the stream bottom. Frequently 

 the horizon which would be occupied by this soil type forms a steep 

 cliir of clayey material unadapted for agricultural purposes. This zone 

 of Sassafras loam does not alwavs show tlie soil formation in its most 

 typical character, since it lies in a position to catch much of the sandier 

 material washed down by rains from higher levels. In these cases 

 the soil is more sandy than in type localities, but the subsoil is the 

 usual heavy clay found elsewhere throughout this formation. 



Lying along the stream valleys and along the Patuxent slope are 

 flat-topped terraces built up in recent geological times from materials 

 which have been derived from the Calvert clays and reworked into 

 later deposits. So far as soil values are concerned, these materials 

 form the same soil types as when they composed part of the Miocene 

 strata, though they now occur as terrace forms. A terrace of this 

 character is well developed at about 80 feet elevation just west of 

 the head of tide water on St. Leonard Creek, another is foimd just 

 southwest of Dares Wharf, and many more examples could be cited 

 from localities along the Patuxent. The region l\ing just cast of Lower 

 Marlboro presents an area where the Sassafras loam terrace of later 

 age rests against the outcrop of Miocene material, giving rise to the 

 same soil type and the resulting occurrence of Sassafras loam is one 

 of the largest to be found in Calvert County. 



The influence of this heavy clayey material as it occurs at Miocene 

 horizons is felt in the northern areas of Norfolk sand. The clay comes 

 near the surface, under the covering of sandv soil, and in some cases 

 forms sticky bands of small extent in fields otherwise uniformly cov- 

 ered by the sands of the Norfolk sand. 



