color of the mud ranges from 5G4 5/1 to 5G4 6/1 (Munsell Color Code) and 

 is generally uniform; however, brown and yellow mottling is common. 



In most places the mud is massive, and some samples have a fissile 

 structure. Although soft when wet, the massive clays dry to a hard compact 

 mass which breaks readily leaving hackly fracture surfaces. The fissile 

 clays tend to become crumbly when dry and break into small fragments. 



Visually discernible characteristics of the greenish-gray mud vary 

 little from place to place. Residue from washing through a 0.062-milli- 

 meter mesh sieve shows variation in texture and composition. 



The most common constituent of the residue is clastic terrigeneous 

 particles ranging in size from very fine sand to granules and consisting 

 primarily of quartz with lesser amounts of other minerals and rock frag- 

 ments. Small amounts of plant and wood fragments and mica are also 

 present in most samples. Biogenic grains are generally very rare or non- 

 existent; where present they consist mostly of small unidentified cal- 

 careous fragments, echinoid spines, and foraminifera. 



In all but three samples the amount of foraminifera in the residue of 

 a 5-milliliter sample was less than five specimens. Contamination from 

 overlying deposits is possible with such small numbers of specimens. 

 However, the three samples contained enough specimens (more than 20) of 

 foraminifera to rule out contamination; most of the specimens were of a 

 single species (Elphidium olavatian Cushman) . 



c. Sand . Sand recovered in cores from the study area is widely 

 diverse in character. Sizes vary from very fine silty sand to very coarse 

 sand (Figs. 10 and 11); sorting values range from well sorted to poorly 

 sorted (App. A). Granules and pebbles occur in modest quantities, espe- 

 cially with coarser sands. 



Typically, sand occurs as the surficial layer; it rarely appears in 

 cores beneath a stratum of dissimilar material. In many places the sand 

 forms only a thin veneer less than 1 foot thick over clay, silt, or gravel. 

 The layer in most of the cores containing sand is less than 5 feet thick. 

 Most cores with a sand layer more than 5 feet thick are from area U3 off 

 Nantasket Beach (Fig. 5) and in the north and south reconnaissance areas. 

 Sand in the study area is chiefly detrital with a minor biogenic content 

 consisting primarily of the hard parts of foraminifera, ostracods, echi- 

 noids, and mollusks (Fig. 10). The dominant mineral constituent is 

 quartz. Rock fragments are common in the coarser sands. Mica is generally 

 present, but is usually very sparse, except in the northern reconnaissance 

 area where it is abundant in the finer sand facies. 



Foraminifera are generally more abundant in sand than in any of the 

 other sediment types. In most samples the dominant genus is Elphidium; 

 E. alavatum Cushman, E. disaoidale (d'Orbigny), and E. poeyanum 

 (d'Orbigny) are the common species. 



31 



