SUBSIDENCE OF DELTAIC SAND SOURCE 



SUBSIDENCE 



t 



TRANSPORT 



SHOREFACE 

 EROSION 



15 20 25 



DISTANCE (km) 



Figure 4. Subsidence of distributary sand sources is the major mechanism 

 driving coastal barrier transgression and deltaic land loss. 



Basal Portion of Ancestral 

 Flanking Barrier Island 



500m -* 



Figure 5. An offshore seismic profile showing the basal portion of a spit 

 complex of an ancestral flanking barrier island of the Chandeleur Islands 

 that has been bypassed by the shoreface and is now preserved on the inner 

 continental shelf. The black line indicates the transgressive contact 

 between the overlying sandy barrier unit and the underlying St. Bernard 

 delta. The seismic line is shore-parallel. 



19 



