common factors creating similarity in sediment type are: 1) age of 

 deposit; 2) sediment source; 3) environment and circumstances of de- 

 position; and 4) post-depositional history. Interpolations of sediment 

 distribution patterns between core sites have been based partly on the 

 assumption that these apparent relationships are real. 



A small number of sediment samples from Fort Pierce grid cores do 

 not fit into a classification. These sediments have been designated "U" 

 (unclassified) in the core descriptions of Appendix C. Most of the un- 

 classified sediments are either quartzose fine sands, found only in the 

 shoreface area, or silty cohesive very fine sands which are more widely 

 distributed (Wentworth classification is used throughout). 



All sediments within the Fort Pierce grid area having a brown colora- 

 tion and devoid of silt or clay are classed as Type A (Figure 16) . The 

 group is variable in nature, but in most places is medium to very coarse, 

 poorly sorted calcareous sand. Quartz is present in all samples, but the 

 content ranges widely from a few percent to over 40 percent (Appendix B) . 

 The quartz grains are clear and colorless with a great variety of shapes. 

 Large, well-rounded grains with frosted surfaces occur in many samples 

 where they are mixed with the more common subangular to subrounded 

 particles of quartz. Size analysis of insoluble residues from selected 

 samples of Type A sediment are presented in Appendix B. 



Type A sediment contains the largest variety of organisms; most 

 species listed in Table II are represented. Barnacle plates are very 

 abundant, making up 50 to 70 percent of the identified fragments. 

 Crassinella lunulata , Chi one grus , Anomia simplex (usually fragmented) , 

 Anadara transversa , and Crepidula fornicata are best represented. The 

 skeletal fragments are mainly shades of brown, pink, white or gray with 

 both rounded and freshly broken fragments mixed. Dark gray and brown 

 well-worn shell fragments, with boring and solution holes, are scattered 

 throughout, but not in large quantities. Foraminifers are rare. 



Nonskeletal carbonate material in the form of ooliths and pellets 

 occur in Type A sediments, and locally in large quantities. Ooliths are 

 especially common in samples from shoals near the seaward edge of the 

 inner shelf. 



Although ubiquitous throughout the inner shelf area. Type A sediments 

 have not been recognized in the few cores obtained from the outer shelf 

 area (-70 to -230 feet MLW) . Where found. Type A sediment is always upper- 

 most in the column. Over the flats-, it usually occurs as a relatively thin 

 blanket deposit less than 5 feet thick. Over shoals, it thickens appreci- 

 ably, and seismic data indicates that some sm^aller shoals are entirely 

 composed of this material. 



Type B sediment is a gray calcareous sand usually fairly well sorted, 

 but may be silty or poorly sorted in some places (Figure 17) . This mate- 

 rial underlies Type A sediment where found. The position, size similarity, 

 and composition of Type B material suggests that it is a facies of Type A 



33 



