Inner Shelf Stratigraphy 



Cross-shore stratigraphic sequences 



Numerous authors (see Appendix B, "Sedimentary Features and Strati- 

 graphy References") have identified cross-shore sequences of sedimentary 

 structures and resulting stratigraphy. Clifton (1976) documents the follow- 

 ing typical sequence of sedimentary structures for the Oregon coast inner 

 shelf resulting from wave-induced oscillatory flow (Figure 16), beginning 

 offshore and moving landward: 



a. Inactive zone. 



h. Active asymmetric ripples. 



c. Long-crested asymmetric ripples. 



d. Irregular asymmetric ripples. 



e. Asymmetric cross-ripples. 

 /. Megaripples. 



g. Flat bed. 

 Similar sequences were also found in Australia by Boyd (1981). 



Land 

 -■ — Symmetric Asymmetric 



Inactive Active Long-Crested Irregular Cross— Ripples Lunate Megoripples Flat Beds 



■ / 



\\V Y ' If! 



! 1 l)(i'/^, 



Figure 16. Cross-shore sequence of structures commonly found off the coast of southern 

 Oregon (after Clifton (1976)) 



Chapter 4 Sedimentary Features/ Stratigraphy of the Inner Shelf 



55 



