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STRUCTURAL GEOLOGY OF NORTH AMERICA 



SECTION )S 



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Fig. 10.3. Crojs sections of the Atlantic Coastal Plain, after Richards, 1945. Section 33, 

 Richmond, Va., to Norfolk, Va. Section 35, Wilmington, N. C, to Parris Island, S. C. See 

 index map. Fig. 7.1. 



SECTION J6 



Fig. 10.4. Section of the Atlantic Coastal Plain from Virginia to Long Island, N. Y., after 

 Richards, 1947. 



Evidently, therefore, an unconformity of considerable magnitude exists 

 between the Tertiary and Cretaceous systems. 



The absence of Oligocene beds, except in the south, suggests an un- 

 conformity between the Miocene and Eocene. In most of Richards' sec- 

 tions, however, the Miocene seems conformable on the Eocene. One ex- 

 ception is noted near Summerville, South Carolina. A break, however, 

 occurs between Lower and Upper Miocene in the area between Norfolk, 

 Virginia and Wilmington, North Carolina, where the Yorktown-Duplin 

 formation rests across the entire Lower Miocene, Eocene, and most of 

 the Upper Cretaceous succession. The Geologic Map of the United States 

 shows very clearly the unconformity between the Yorktown beds and the 

 entire Upper Cretaceous, Eocene, and Lower Miocene succession in the 

 region adjoining the states of North and South Carolina. Inspection of the i 

 map also reveals an unconformity between the Pliocene beds and older 

 ones in this region. 



Cape Fear Arch. The most conspicuous feature of the Coastal Plain 

 is the Cape Fear arch of North and South Carolina. See index map, Fig. 

 7.1, and the Geologic and Tectonic Map of the United States. Structure 

 contours on the top of the Cretaceous bulge outward at this place and 

 reveal a very broad nose on the regional seaward dip, so the structure is 



