TERTIARY EROSION INTERVALS NORTH CAROLINA AND VIRGINIA 675 



Augusta, Georgia. The Trent formation rests on underlying strata of Creta- 

 ceous age along the Neuse and Trent rivers, and farther west is found in imme- 

 diate contact with the underlying crystalline rocks of pre-Cambrian age. So 

 far as known at present, the Trent formation has a wider inland distribution 

 in North Carolina than any other Coastal Plain deposit. Isolated patches are 

 known far to the west of the present "fall line," one of these occurring a few 

 miles from Raleigh, and another one near Spout Springs, in Harnett county, 

 while still other areas have been reported from Moore county, in all of which 

 they overlie directly the crystalline rocks. 



The second formation of the North Carolina Eocene has received the name 

 of Castle Hayne because of its development in the vicinity of Castle Hayne on 

 the northeast Cape Fear river. The lithologic characteristics of this formation 

 are, as in the case of the Trent, distinctly calcareous, with little or no glau- 

 conite present, thus making it distinctly unlike the Eocene deposits of Virginia 

 and Maryland. The fossils of this formation have not as yet received careful 

 study, though Doctor Vaughan states that they form an entirely distinct fauna, 

 unlike any known in South Carolina or in the Atlantic Coastal plain to the 

 northward. The Castle Hayne formation outcrops in a very limited area in 

 the southeastern part of the state, and wherever observed rests directly on 

 Cretaceous strata belonging to the Peedee formation, and, further, it contains 

 many Cretaceous shells that have been derived from these deposits. Several 

 articles have already appeared in which the commingling of the Cretaceous 

 and Eocene species in this formation at Castle Hayne and Wilmington have 

 been described. 



The distribution of the Trent formation in small isolated patches over such a 

 wide area indicates extensive post-Trent erosion, and the fact that we find tbe 

 Castle Hayne formation resting on Cretaceous strata proves that at least a 

 part of the intervening Trent strata must have been removed before the depo- 

 sition of the Castle Hayne formation. 



Post-Eocene Interval 



When we come to the Miocene we find that throughout the entire Coastal 

 plain there is evidence of a considerable gap between the Eocene and the 

 Miocene, though in Maryland it is scarcely possible to determine this uncon- 

 formity except by overlap. In Virginia the same conditions exist, and there we 

 find the Miocene gradually transgressing the Eocene to the westward until it 

 comes to rest on the Piedmont crystalline rocks, entirely concealing the Eocene. 

 In North Carolina the unconformity is much more pronounced, and there we 

 find in many places Miocene beds resting on the Eocene deposits that occupy 

 depressions in the irregular surface of the Cretaceous. Thus we find the 

 Miocene resting on the Eocene in one locality, while a short distance away, at 

 almost the same level, the Miocene is found in contact with the Cretaceous. 

 The occurrence of Eocene deposits in pockets proves in a better way than in 

 the case of the Maryland deposits an extensive erosion period separating the 

 Eocene and Miocene. There is little doubt but that in the interstream areas of 

 North Carolina beneath the covering of Pleistocene and Miocene strata there 

 ai'e many other patches of Eocene that have so far escaped observation. 



