MARYLAND GEOLOGICAL SURVEY 79 



the Choptank formation is very fossiliferous, and may be seen at the 

 base of a low cliff wliich borders the stream for some distance. 



Areal Distrihuiian. 



The Choptank formation, which constitutes the second member of 

 the Chesapeake Group in Maryland and lies immediately above the 

 Calvert formation, is found in Caroline, Talbot, and Dorchester counties, 

 on the Eastern Shore, and Anne Aiuiiilcl, Calvert, Prince George's, 

 Charles, and St. Mary's counties on the Western Shore. On botli the 

 Eastern and Western Shores- it is very much obscured by younger deposits 

 which overlie it. In Calvert County the Choptanlc formation extends 

 from Mt. Harmony southward to a line running from Point of Rocks 

 to the mouth of Hellen Creek. Througliout the region it lies uncon- 

 formably on the Calvert formation and is itself overlaid conformably 

 by the St. Clary's formation or unconformably by the various formations 

 of the Columbia Group. This cover of surficial deposits is so extensive 

 that the Choptank formation is nowhere exposed on the divides but 

 is met witli in nearly all the stream valleys throughout the area desig- 

 nated. Near Mt. Harmony the Choptank formation is found lying 

 on the Calvert at an elevation of about 100 feet. From here it sinks 

 very gradually to the vicinity of Parker Creek and then more rapidly 

 till it disappears below tide in the southern part of the county. In 

 the headwaters of Fishing Creek on the east and Cocktown and Hunting 

 Creeks on the west the Choptank formation lies high in tlie valley 

 walls and the Calvert formation appears beneath it. In the southern 

 part of the county in tlio headwaters of St. Leonard Creek and associates 

 the Choptank formation occurs in the bottoms of the valleys and younger 

 formations lie above it. By far the best exposures are to be seen 

 along the Calvert Cliffs from Parker Creek southward to Point of 

 Rocks and along the Patuxent River in the vicinitv of St. Leonard 

 Creek. 



Strike, Dip and Thickness. 



The strike of the Choptank formation is in general from northeast 

 to southwest; but because of erosion, particularly on the Western Shore, 



