MARYLAND GEOLOGICAL SURVEY 81 



its attitude can be secured by comparing the various elevations of its 

 surface rather than those of its base. Yet it must be taken into account 

 that the areas back on the Piedmont Plateau are not as thick as they were 

 originally, but have lost perhaps five or ten feet of surface loam through 

 processes of subaerial erosion. The central portions of the divide in 

 southern Maryland, however, seems to have lost little or nothing through 

 this process. By comparing surface altitudes in various places (Plate 

 XXIII), it has been found that the Lafayette formation was developed 

 as a plain which showed practically no change in elevation from north- 

 east to southwest along the Piedmont border, but had a very gentle 

 decline in a southeasterly direction across the Coastal Plain toward the 

 Atlantic ocean. Between the outliers at Woodlawn and those near Elk 

 Neck, the slope is greater than elsewhere within the Coastal Plain. The 

 distance between these two areas is ten miles and the total difference in 

 surface elevation is 170 feet. The average slope then amounts to 17 feet 

 per mile. It must be remembered, however, in comparing this with other 

 observations that the distance separating the two localities is not great 

 and the slope consequently averages more to the mile than if the same 

 difference in elevation was separated by a greater distance. This is well 

 shown in the southern part of the area where a difference in elevation 

 of 200 feet occurs between the surface of the Lafayette in the District 

 of Columbia and at Charlotte Hall. These two localities are separated 

 by a distance of 36 miles, which gives to the formation a slope of 5.5 feet 

 per mile. This slope should be considered as more nearly normal for the 

 formation than that at the head of the Bay in Cecil county. 



It will be noticed that the structure has been referred to as slope 

 rather than dip. There are, in fact, two elements to be considered in 

 discussing the structure of this formation; for it must be remembered 

 that the Lafayette is a deposit which has not been covered by another, but 

 has been raised nearly parallel to its former position from beneath the 

 sea. One of these elements is the original slope which the formation 

 possessed as it was deposited on the ocean bottom and gently declined 

 from the shore out towards deeper water. This appears to be the 

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