the south up to 6 nautical miles seaward of the shoreline (Figs. 40 and 41). This sand is 

 mostly interbedded with clays, particularly in the region north of St. Johns River Entrance. 

 Because of the presence of fine sand and its often silty character, and the common 

 occurrence of clay layers, this zone is unpromising for location of any extensive deposits of 

 clean sand which would be potentially usable for replenishment of nearby beaclies. 

 However, some locales within the zone have potential and therefore warrant further 

 investigation. A summary of the more promising locals in the region follows. 



(1) Area A-1. This area is a low linear shoal trending northeast. Core 194 near the 

 southwest end recovered 9 feet of clean fine to medium quartz sand with thin layers of 

 varying size. Composite sand borrowed from this site may prove satisfactory for use on 

 nearby beaclies. Since the site appears to afford the only reasonable prospects in the 

 Fernandina grid it warrants further investigation. 



(2) Area A-2. Core 76 at the northwest edge of this low Unear ridge atop a bank 

 shoal contains clean quartz sand with a median diameter range of 0.330 to 0.268 

 millimeters (1.6 to 1.9 phi). Since core 76 was only 3 feet long it is not known if the ridge 

 contains similar material in depth. Seismic evidence suggests that the sand is 10 feet or more 

 thick. 



(3) Area A-3. Core 191 at the extreme end of a long low ridge contains suitable sand 

 with a mean diameter of 0.380 millimeters (1.4 phi), in the upper 2 feet. If the ridge is 

 covered by similar material it would provide a usable offshore borrow site but details are 

 lacking. The material in core 191 is fine grained below —2 feet and it is doubtful if any but 

 the surficial material will be suitable. 



(4) Area A-4. Cores taken throughout this extensive area off Jacksonville Beach 

 generally contained a thin surficial layer of clean, medium to coarse quartz sand. In general, 

 the upper 2 feet were coarser than deeper material. Suitable borrow sites probably exist at 

 several places witliin tliis area; however, indications are that the sand is probably too thin in 

 many places for a desirable borrow site. The best material was contained in cores 78, 79, 

 and 185 in the eastern part of the area. There is not enough information from this area to 

 estimate the volume of suitable sand that may be available, but further study is warranted. 



(5) Area A-5. Cores 48 and 65 located over the "ancient channel" of the St. Johns 

 River contained reasonably clean, medium to coarse quartz sand under a shallow overburden 

 of type F sand. Tliis material may represent a deposition in the old channel and further 

 exploration of the channel area outlined in Figure 17 would be warranted, especially since 

 this site is closer to shore than most potential sites in the Fernandina-Jacksonville area. 

 Further exploration would probably be most productive along the central part of the 

 channel area southeastward of core 48; cores to tlie northwest indicate that the channel in 

 that area is probably filled, by silty sand and clay. There are insufficient data available for a 

 reUable estimate of the sand volume, but there may be over 5.0 X 10^ cubic yards of clean 

 sand in the channel deposit. 



94 



