Pamlico Sound 



Hatteras Flats 



Rodarvthe 

 Outer Banks 



WimJble Shoals 



Plei»toeen« wrth weothering profile on surfoee 

 (PIsrCB ic Colqutioun, 1970) 



Modem borrier 

 Island complex 



Pl«l«tac«n< 

 cooatal complex 



Ptolctoc«n« 

 cooslol complex 



Auger hole 



(Pi«rc« & Colquhoun, 1070) 



Figure 7. Geologic cross section tiirougii the Outer Banks at Rodanthe showing the 

 Pleistocene units cropping out on the inner shelf forming Wimble Shoals 

 (after Pilkey et al. (1993)) 



c. They are not in equilibrium with incoming wave energy, suggesting 

 that these features erode. 



d. They have dramatic impacts upon the energy regime affecting the 

 adjacent inner shelf through wave refraction and setup. 



In addition, the geomorphic nature of an area must also be considered 

 when determining mechanisms and resulting shelf sediment transport. In 

 examining patterns of sedimentation on the continental shelf. Swift (1976) 

 examined the mechanisms by which the nearshore is penetrated (at the in- 

 ner shelf/oceanic process boundary and at river mouths) and how sedi- 

 ment is injected into the shelf system. He found that the original mode of 

 formation of the coast and surrounding areas had a large effect on present 

 day sedimentation patterns. Swift (1976) differentiated between 

 allochthonous and autochthonous settings. Allochthonous shelves 

 (shelves presently composed of sediment formed elsewhere and sub- 

 sequently deposited on the shelf) are typically floored by fine sands to 

 muds (due to the introduction of riverine sediment through river-mouth by- 

 passing) and are usually featureless, as these fine sediments travel in sus- 

 pension. In addition, there is little bed form formation, as fine sediments 

 have low angles of repose. Autochthonous shelves, or shelves presently 

 composed of sediment originally derived from previous erosion of the 

 shelf in its present location, are covered by coarser- grained sand of local 

 origin. 



18 



Chapter 2 Inner Shelf Concepts 



