boring J-1 (Fig. 2) of the Joint Oceanographic Institutes Deep Earth Sampling Program 

 (JOIDES) was collected. This boring is described in Schlee and Gerard (1965), Charm, 

 Nesteroff, and Valdes (1969), and Hathaway, McFarhn, and Ross (1970). Line profiles 

 based on the two seismic records are presented in Figures 20 and 21. 



Few primary reflectors identified in tlie main study area can be traced with confidence 

 along these two profiles as far as the site of J-1 because there are extensive discontinuities in 

 most reflectors. Projections along the general trend of the reflector surface suggest probable 

 connections in most cases. The reflector patterns show that the gentle seaward dip of strata 

 in the Neogene section underlying the study area persists as far as J-1 with occasional 

 sections where they are flat-lying or the dip is reversed. 



In terras of gross lithology, tlie Neogene section at J-1 does not sliow close similarities to 

 the succession constructed from cores and borings in tlie study area. In particular, the 

 pronounced Uthologic division between quartz sand which appears to be characteristic of 

 units A, B, and C, and the silt-clay of underlying unit D, are not apparent in the Neogene 

 section of J-1 which is logged as predominantly silt with some sandy intervals. 



The purple reflector, wliich in this part of the study area separates unit C and D, was 

 tentatively traced to a position about 171 feet below the sea floor at J-1; there are some 

 Uthologic changes at this depth but not as marked as the changes observed inshore. 

 According to Charm, Nesteroff, and Valdez (1969), at about 167 to 151 feet downhole in 

 J-1, there is a sharp decrease in phosphate content where quartz increases substantially in 

 particle size and abundance. The white reflector at the base of unit B is also traceable with 

 fair assurance on the Jacksonville J-1 line but cannot be traced back to Fernandina. At J-1, 

 this reflector lies about 98 feet beneath the sea floor near a horizon in J-1 above which there 

 is a marked increase in planktonic foraminifera and a decrease in quartz. The increase in 

 planktonic fauna may be roughly correlative with unit B which contains abundant 

 planktonics; however, the low quartz content is lithologically dissimilar to unit B as closer 

 inshore. 



III. SURFACE AND SUBBOTTOM SEDIMENT CHARACTERISTICS 

 AND DISTRIBUTION 



I. Inner Shelf Sediment Characteristics. 



a. General. Sediment data are based on macroscopic and microscopic examination of 

 about 1,200 samples from 197 vibratory cores of 3-inch diameter and averaging 10 feet in 

 length. Numbered core locations are plotted in Figures 2 through 4. Sediment samples were 

 collected at 1-foot intervals from each core; selected cores were split and samples collected 

 at closer intervals for examination. Textural parameters of sands visually ascertained to be 

 suitable for beach nourishment were determined by sieving and fall velocity; results are 

 given in Appendix B. 



Sediments of the north Florida inner Continental Shelf are highly variable in both size 

 characteristics and in particle shape and mineralogy. These variations are mappable over 



41 



