eustatic fluctuations in sea level that resulted in alternating submergence 

 and emergence of the landscape. The sequence of events forming each terrace 

 was similar. Sea level rose to some maximum altitude during a period of 

 submergence (transgression) . Submergence resulted in formation of a barrier 

 island chain with associated lagoonal/marsh sediments on the landward side, 

 similar to the present coastline. Inlet deposits, estuarine and channel sedi- 

 ments, and a seaward thinning wedge of offshore sediments were also deposited 

 much as present day. This cycle was terminated by climatic changes that 

 resulted in shoreline emergence (regression) . When climate once again 

 shifted, a new cycle of submergence began, with sea level stabilizing at an 

 altitude slightly lower than a previous cycle. The new barrier complex (ter- 

 race) formed seaward and lower than the first one. Geological evidence indi- 

 cates that from North Carolina south into Georgia, these cycles of submergence 

 followed by emergence occurred at least three times over the Middle Coastal 

 Plain and six times over the Lower Coastal Plain. Present barrier/marsh/ 

 lagoon sequences constitute a seventh cycle. Advance of the sea landward in 

 each instance was less than prior cases, thus preserving the old shoreline. 

 Likewise, withdrawals of the sea were probably not of similar magnitude. Some 

 may have been relatively minor. Field recognition of terraces in the Middle 

 Coastal Plain is made difficult by long exposure to erosive forces. 



23. The Middle Coastal Plain is separated from the Upper Coastal Plain 

 by the Orangeburg Scarp (Colquhoun 1965) , which is the landward margin of the 

 Duplin Formation. The Duplin Formation was deposited during a marine trans- 

 gression; the Duplin shoreline has a maximum altitude of 65 m above MSL. 

 According to Colquhoun (1974) , subsequent overall slow recession with episodic 

 transgressions or still stands resulted in formation of the Coharie (65 m 

 above MSL), Sunderland (52 m) , and Okefenokee (41 m) terraces. Colquhoun 

 assigns the transgressive Duplin and terrace deposits to late Miocene age. 

 The Miocene sea level rise was followed by a slow emergence during Pliocene. 



24. Tertiary sediments of the Middle Coastal Plain are separated from 

 Quaternary sediments of the Lower Coastal Plain by the Surry Scarp. Terraces 

 formed during early Pleistocene include the Wicomico (33 m) and the Penholoway 

 (21 m) of Colquhoun (1974). The Talbot (12 m) , Pamlico (8 m) , and Princess 

 Anne (5m) appear to have formed during the Sangamon inter -glacial period of 

 late Pleistocene. The youngest Pleistocene terrace is the Silver Bluff (3 m) , 

 which is assigned to Sangamon age by Colquhoun (1974) and to mid-Wisconsin by 



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