MARYLAND GEOLOGICAL SURVEY Gl 



Cliffs, an almost unbroken exposure for more than 30 miles. Southern 

 Maryland is, therefore, the type locality for the study of the Miocene beds 

 of the Middle Atlantic slope. 



In Virginia again, as in Delaware, the underlying formations have been 

 so concealed by younger gravel and sand deposits that they are seldom 

 met with except along river courses. The best of these sections occurs 

 at the famous Nomini cliffs on the Potomac river. These cliffs, although 

 only two miles in extent, surpass the Calvert cliffs in height and yield the 

 most comprehensive Miocene section in Virginia. Other sections are to 

 be found along the Eappahannock, Pamunkey, York, and James rivers. 

 Bellfield and Yorktown on the York river and Kings Mill on the James 

 are classic fossiliferous localities. In Forth and South Carolina the state 

 of knowledge regarding the Miocene is very imperfect. The beds are 

 much obscured by a cover of younger material and appear to occupy 

 isolated areas throughout the Coastal Plain, although they may be found 

 to be more continuous than at first supposed. On reaching Florida the 

 Miocene beds again become more prominent and continue so around the 

 southern borders of the Gulf States, through Georgia, Alabama, Missis- 

 sippi, Louisiana, and Texas into Mexico. 



pliocene ( ?) . 



Above the Miocene and unconformable with it occurs the Lafayette 

 formation. This is a mantle of poorly-sorted gravel, sand, and loam 

 which covers the highest divides of the Coastal Plain and stretches as a 

 broad belt from the Delaware river southward into Mexico. By far the 

 most extensive area north of the Potomac river occurs between Washing- 

 ton and Charlotte Hall. North of this region the Lafayette is repre- 

 sented only in small isolated outliers, while south of the Potomac the for- 

 mation, although not so thoroughly known, has suffered less from erosion 

 and is believed to occupy a broad belt along the inner margin of the 

 Coastal Plain. 



On account of the lack of sufficient paleontological material, the age of 

 the Lafayette formation is somewhat in doubt, but it has been provision- 

 ally referred to the Pliocene until sufficient evidence is at hand to precisely 

 fix its stratigraphic position. 



