are: (a) an unstable heavy mineral assemblage similar to that of Georgia coastal sediments 

 and reflecting a metamorp hie -igneous source region, and (b) a fine-grained low carbonate 

 nature suggesting modern fluvial derivation. 



The Georgia coastal region is a likely source for the north Florida shelf quartz sands. No 

 large rivers draining Piedmont formation discharge to the Florida Atlantic coast, whereas 

 Georgia contains numerous streams and rivers with headwaters in the Piedmont province 

 carrying sediment to the coast. In particular, the Savannah and Altamaha Rivers, according 

 to Meade (1969), are among the rivers on the east coast highest in suspended sediment 

 discharge. 



Since north Florida sands (shelf and beach) are finer and less calcareous than sediment 

 adjacent to and South of Cape Canaveral, investigators have suggested a Georgia fluvial 

 source for "modern" shoreface sands and "relict" inner shelf deposits. Henry and Hoyt 

 (1968) mapped gray fine quartz sands in the nearshore Georgia shelf and ascribed their 

 origin to reworking of coastal sands during the last transgression. Seaward of approximately 

 the —50-foot contour lie coarser iron-stained Pleistocene sands. The sharp break between 

 the two sediment types has been reported by many investigators (Hpward, 1972; PUkey and 

 Frankenberg, 1964) and referred to as the "rehct-recent boundary." 



Milliman (1972) has characterized the fine sand lying within 4.4 nautical miles off the 

 coast (Type F) as possibly modern fluvial deposits and considered the belt to be continuous 

 between Cape Fear, North Carolina and Cape Canaveral. Seaward of the possibly modern 

 fluvial deposits lie relict shallow water terrigenous deposits. However, nearshore sands off 

 Georgia are classified by MiUiman as subarkosic, whereas those off north Florida are 

 orthoquartzitic. Field and Pilkey (1969), also reported similar discrepancies between 

 feldspar values for Georgia shelf and Florida shelf sand. Other mineralogical aspects of the 

 two shelf areas are equally incongruent. Heavy mineral assemblages in Georgia rivers and 

 shelf sands are unstable, i.e., they reflect derivation from Piedmont rocks without having 

 passed through a sedimentary cycle of deposition, hthification, and subsequent erosion. 

 Heavy minerals of Florida shelf sands are both unstable and stable (Pilkey, 1963, 1968) 

 which may indicate different source areas or a single source followed by weathering during 

 lower sea level or resorting. Within a small area north of Cape Canaveral, Tyler (1934) found 

 large variations in mineralogy of surface samples, but gave no explanation. More recently 

 Carver (1971), studied samples along a shore-normal shelf transect off Georgia and noted 

 large variations in mineralogy, particularly hornblendes, which he attributed to differing 

 fluvial sources during the Holocene transgression. These discrepancies in mineralogy 

 (feldspars and heavy minerals) suggest that although Piedmont-draining streams in Georgia 

 may have been the original and perhaps most significant source, other secondary sources 

 have been interjecting material into the inner shelf surficial deposits. 



(2) Residual Shelf Contributions. The large extent of surface exposures and 

 near-surface occurrences (less than 10 feet) of Tertiary strata lias been well documented in 



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