MARYLAND GEOLOGICAL SURVEY Ixix 



and appears to occupy isolated areas throughout the Coastal Plain, 

 although it is possible it may be more continuous than at first appears. 

 The exposures of the Miocene are found along many of its principal 

 rivers. 



South Carolina 



The Miocene in South Carolina is not very well kno^vn and has not 

 been carefully differentiated from the overlying Pliocene. 



Gulf Coast 



In Florida the Aliocene is better known than in the Carolinas, and 



the beds probably continue around the southern borders of the Gulf 



States through Georgia, Alabama, Mississippi, Louisiana and Texas 

 into ]\[exico. 



The Chesapeake Group in Maryland 



The Miocene deposits of the Middle Atlantic slope have been de- 

 scribed under the name of the Chesapeake Group. In Maryland, the 

 materials which compose the formations of this group consist of clay, 

 sandy-clay, sand, marl and diatomaceous earth. The sandy-clay mem- 

 bers are, when freshly exposed, greenish to greenish-blue but slowly 

 change under the influence of the weather to a slate or drab color. 

 As the Miocene beds contain but little glauconite, it is not a difficult 

 task on the basis of lithologic criteria to separate them from the Eocene 

 deposits, and they are still more readily distinguished from the Cre- 

 taceous and Potomac beds beneath as well as from the Columbia loams 

 and gravels above. 



It has been found possible to separate the beds of the Chesapeake 

 Group into three formations, which are designated, beginning with 

 the oldest, the Calvert formation, the Choptank formation and the 

 St. Mary's formation. The areAl distribution of the several formations 

 is shown on the accompanying geological map. (Plate I.) 



the calyert formation. 



Calvert county has suggested the name for this formation because 

 of its typical development there. In the famous Calvert Cliffs along 

 the eastern border of this county the waves of Chesapeake Bay have 



