RECENT INVESTIGATION OF COASTAL PLAIN FORMATIONS 649 



Tertiary 



RELATION OF TERTIARY TO CRETACEOUS FORMATIONS 



The Tertiary formations overlie the Cretaceous formations unconformably, 

 and at times transgress them, the Tertiary strata in such instances resting 

 directly on the crystalline rocks of the Piedmont plateau. 



The Eocene deposits of New Jersey, known as the Shark River formation 

 (glauconitic beds), apparently overlie the Manasquan formation conformably. 

 The contained fossils show the beds to be of early Eocene age. Farther south 

 in Maryland and Virginia, but nowhere in contact with the Shark River beds, 

 is a series of younger and conformable Eocene deposits known as the Aquia and 

 Nanjemoy formations (glauconitic beds, clays, sands), which overlie the Cre- 

 taceous unconformably. Entirely discontinuous are the North Carolina Eocene 

 strata, which Miller has named the Trent and Castle Hayne formations (calca- 

 reous marls, clays), and which are of still later Eocene age. The latter are 

 apparently unconformable to each other, and likewise rest unconformably on 

 Cretaceous deposits. 



The Miocene deposits are best developed in the Chesapeake Bay region, where 

 four formations have been recognized, known as the Calvert (clays, sandy 

 clays, diatomaceous earth, shell marls), the Choptank (sandy clays, sands, 

 shell marls), the St. Mary's (sandy clays, sands, shell marls), and the York- 

 town (fragmental shell marls, sandy clays, sands). The Choptank does not 

 occur in Virginia, and the Yorktown is absent in Maryand. These formations 

 are evidently continued in part into New Jersey, as similar faunas have been 

 found there, but the relationships have not been fully worked out as yet. To 

 the southward the St. Mary's and Yorktown formations, transgressing the ear- 

 lier deposits, continue on into North Carolina, both being found over extensive 

 areas to the north of the Hatteras axis, where the Yorktown overlies the St. 

 Mary's unconformably. To the south of the Hatteras axis deposits very similar 

 to the Yorktown formation, both lithologically and paleontologically, but known 

 under the name of the Duplin formation, are found resting unconformably on 

 pre-Miocene formations. 



The Pliocene deposits are of two types : (a) the marine beds, called the Wac- 

 camaw formation (clays, sands, shell marls), and confined to a narrow belt on 

 the eastern margin of the Coastal plain of North Carolina; (&) the terrace de- 

 posits found along the higher portions of the Coastal plain, and known as the 

 Lafayette formation (gravels, sands, loams). The terrace is more dissected 

 than the later Pleistocene terraces. The Lafayette formation is most exten- 

 sively developed in Maryland and Virginia. In Delaware and Pennsylvania 

 on the north and North Carolina on the south it is very fragmentary. 



