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EMERGED QUATERNARY SHORE LINES 

 IN THE MISSISSIPPI EMBAYMENT 



By C. WYTHE COOKE 



Honorary Research Associate 

 U. S. National Museum 

 Smithsonian Institution 



ABSTRACT 



Borings through the alluvial deposits of the Mississippi Embayment 

 reveal steep-walled valleys entrenched in the underlying Tertiary and 

 Cretaceous formations. Repeated fluctuations of sea level during the 

 Quaternary Epoch drowned the valleys to a maximum height of 

 360 feet. Emerged shore lines at this and nine lower levels remain 

 horizontal. They stand at the same heights as horizontal shore lines 

 in Alabama and along the Atlantic seaboard. The altitudes of the 

 shore lines and the names of the terraces bounded by them follow : 





altitude in 





terrace 



feet w 



teter 



Morley 



360 



110 



Hazlehurst 



275 



84 



Coharie 



215 



66 



Sunderland 



170 



52 



Okefenokee 



145 



44 



Wicomico 



100 



30 



Penholoway 



70 



21 



Talbot 



42 



13 



Pamlico 



25 



8 



Silver Bluff 



6 



2 



Alluvial deposits accumulated at tidal flats and bayhead deltas 

 during each of these ten stages in tidewater that was kept fresh or 

 only slightly brackish by the inflow of the Mississippi and other great 

 rivers that emptied into the bays. At each stage the rivers meandered 

 across the tidal flats built during the preceding higher stages and laid 

 on them a veneer of floodplain alluvium, obscuring but not completely 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 149, NO. 10 



