THE GEOLOGY OF ST. MARYS COUNTY 



BY 



GEORGE BURBANK SHATTUCK 



Introductory. 



Special attention is given in the following pages to the stratigraphy, 

 structure, and areal distribution of the various deposits which are 

 found within the borders of St. Mary's County. These deposits 

 are all unconsolidated except where the local conditions have pro- 

 duced unimportant indurations. The deposits of St. Mary's County are 

 among the youngest deposits in Maryland. They do not date back 

 further than the Miocene and extend with occasional breaks down to 

 the present. The geologic history of St. Mary's County is complex, how- 

 ever, and was frequently interrupted by erosive intervals, so that por- 

 tions of the geologic history have been destroyed and lost. These breaks 

 are made manifest by the existing unconformities between the beds 

 of different materials. 



The various formations of St. Mary's County in their regular sequence 

 of superposition arc as follows: 



Age. Formation. Group. 



[■Talbot -) 



PleistoceDe J Wicomico L Columbia. 



[Sunderland J 



Pliocene Lafayette 



rSt. Mary's "| 



Miocene J Choptank L Cbesapeake. 



[Calvert J 



The oldest deposits of St. Mary's County are the three formations of 

 the Chesapeake Group, which are Miocene in age. They are, beginning 

 with the oldest, Calvert, Choptank, and St. Mary's. In this county, if 

 the geological relations are the same as elsewhere, the Calvert formation 

 rests unconformably on the Eocene, although the contact is not visible ; 



