The early Wisconsinan falling sea- level and subsequent lowstand caused 

 upstream river entrenchment and downstream deltaic progradation beyond the 

 shelf edge. Later, deltaic sedimentation shifted landward in response to a 

 middle Wisconsinan sea-level rise and then seaward in the late Wisconsinan as 

 sea-level fell to its lowest position. Carbonate reefs grew on a broad 

 terrace between the major deltas during the initial postglacial rise in sea- 

 level. The continued sea- level rise (Holocene) and highstand resulted in 

 erosion and retreat of deltaic headlands, progradation of interdeltaic 

 barriers and strandplains , and aggradation of alluvial valleys, bays, and the 

 inner shelf. Modern patterns of shoreline deposition resemble those of the 

 preceding (Sangamonian) highstand. 



Local and regional structures controlled the position and thickness of 

 some late Wisconsinan and early Holocene deposits, such as river channels, 

 sand ridges, and carbonate reefs. Lowstand deltas along the basin margin are 

 several times thicker than their updip counterparts because of rapid 

 subsidence and progradation into relatively deep water at the shelf edge. 

 Landward of the shelf edge, however, thicknesses of depositional sequences and 

 individual fluvial, deltaic, and barrier island sand bodies are comparable 

 regardless of whether they were deposited under static or falling sea-level 

 conditions. Apparently, thicknesses of these stable-platform deposits 

 depended nearly equally on subsidence and water depth. (Authors). 



228 MOSLOW, T. F. , and COLGUHOU, D. J. 1981. "Influence of Sea-Level 

 Change on Barrier Island Evolution," Oceanis . Vol 7, No. 4, pp 439-454. 



A detailed stratigraphy examination of Holocene coastal deposits from 

 the southeast Atlantic coast of the United States has documented the over- 

 riding influence of eustatic sea- level fluctuations on barrier shoreline 

 evolution. Sediment supply, pre-Holocene topography and shoreface profiles 

 are other important controls in Late Holocene barrier island development along 

 depositional shorelines adjacent to broad gently sloping, tectonically stable, 

 sandy coastal plains around the world. 



The Holocene stratigraphy of two progradational , beach ridge barriers on 

 the South Carolina coast contains a well-preserved record of transgressive 

 (5,800-4,000 B.P.) and regressive (4,000 - B.P.) phases as follows: 

 1) origin of a primary barrier and initiation of back-barrier sedimentation 

 from 5,800 - 4,500 B.P.; 2) rapid sea-level rise from 4,500 - 4,000 B.P.; 

 migration of the primary barrier to its most landward position and deposition 

 of a shoreface transgressive lag; 3) initiation of barrier progradation from 

 4,000 - 3,500 B.P., by shoreface accretion as a series of beach ridges; and 4) 

 episodic seaward growth of the barrier complex since 3,500 B.P. This sequence 

 of events is directly correlatable to a separately derived late Holocene 

 eustatic sea-level curve of the South Carolina coast. 



Comparison to other beach ridge complexes from around the world suggests 

 an origin for most barrier islands in a primary transgressive phase from 5,800 

 to 4,000 B.P. Major impetus in barrier genesis is a sharp eustatic sea-level 

 rise around 4,200 - 4,000 B.P. (Authors). 



104 



