sediment. The chief difference between Types A and B is the color of 

 Type B constituent particles which range from white through gray to 

 black (contrasted to the predominant reddish and brown colors of Type A 

 material) . 



Some finer samples of Type B material resemble the fine, well-sorted, 

 carbonate sand described below as Type D, and a relationship may exist. 

 In many places, however, where both types B and D occur in the same core, 

 they are separated by a silty, sandy shell gravel (Type C) and the B 'sedi- 

 ment is darker in color, less well sorted and richer in barnacle plates 

 than the D material. 



Type C sediment is characteristically gray, silty, very coarse 

 skeletal sand to sandy shell gravel (Figure 18). Usually, it is slightly 

 cohesive when wet, and dries to friable lumps of silt, sand and shells. 

 Quartz particles, present in small quantity, range from silt-size to very 

 coarse, irregular, but well rounded grains. Size analysis of insoluble 

 residues from typical Type C sediment are contained in Appendix B. 



Biogenic remains in Type C sediment show close similarity to the 

 Type A assemblage. Anadara transversa , Anomia simplex , Chione grus , 

 Crassinella lunulata , and Crepidula fornicata common in Type A sediment, 

 are also well represented in Type C. Barnacle plates are abundant (25 

 to 50 percent) but less so than in Type A. Venericardia perplana and 

 fragments of Chione intapurpurea appear to be more common than in other 

 sediment types. The condition of shell fragments varies from relatively 

 "fresh" to gray or black well-worn pieces, often pitted by sponge and 

 algal borings. Dark colors predominate. Nonskeletal carbonate material 

 consists mostly of sparse pelletoid and oolitic-shaped grains which occur 

 in some cores. Type C sediments are common throughout the inner-shelf 

 area, but are rarely exposed at the surface. 



Type D sediment is light gray or pale brownish gray, fine-to-medium, 

 well sorted calcareous sand (Figure 19). Locally, it contains shells and 

 shell fragments in sufficient quantity to constitute a second size mode, 

 but most often the sediment has few large inclusions. Constituent par- 

 ticles are generally rounded and sometimes polished. White, gray or black 

 colors predominate, and the contrasting light and dark colors often impart 

 a "salt and pepper" aspect to this sediment. 



Most Type D particles are calcareous and of probable organic origin, 

 although few are identifiable except for small foraminifers . These 

 foraminifers are relatively abundant in the finer fraction, and are of 

 diagnostic value since small species rarely occur in other sediment types 

 of the study area. 



Crepidula fornicata is probably the most common mollusk overall in 

 Type D sediment; however, at least locally, Mulinia lateralis is most 

 abundant. Venericardia perplana and a small species of Olivella are also 

 common. Crassinella lunulata an ubiquitous species in all other sediment 



36 



