It is a well known fact that water content In marine sediments may vary with 

 depth of burial; an inverse relationship Ss most common. It is less well known that 

 the length of the core sample measured affects this relationship to some extent; as 

 the sample size increases, variations in water content may be reduced or entirely 

 concealed. An experiment to investigate the effect of sample length in core G 5 

 is described by Richards and Keller (1962). They concluded that within a 10 cm 

 (4 in) sample length of relatively homogeneous sediment, variations of water content 

 were less than £4 percent from the 10 cm value when sand layers of small thickness 

 were absent. Actual variations in the upper 215 cm of core G 5 are shown in Figure 

 9. 



Results -- The least water content measured was 50.7 percent porosity In core 

 F 6, and the maximum 85.7 percent in core G 3. Surface porosities ranged between 

 56.0 percent, core C 16, and 86.5 percent, core G 2 (Table 3); the latter value was 

 computed from equations 12 and 14 with an assumed particle specific gravity of 2.73. 

 Average surface porosities by area are given in Table 3; they range from 71 .6 percent 

 in Area B to 85.5 percent in Area G. 



Porosity in general is inversely related to depth in all cores, except those from 

 Area F; cores from Area H and D Ip show only a very slight decrease of porosity with 

 increasing depth. The porosity profile in core F 6 is variable with depth. In the 

 remaining Area F cores, the porosity profile decreases down to an intermediate depth 

 and then increases to the bottom of the core. At an unknown greater depth, an inverse 

 relation presumably again is established. The reason for the change appears to be re- 

 lated to the decrease in the percentage of the clay-size fraction at mid-depth and the 

 resulting increase in particle median diameter. 



Relation of porosity to most other parameters is considered elsewhere in this report. 

 Porosity also is directly related to percentage of the clay-size fraction (Fig. 10). 



Discussion — The fine-grained fraction in marine sediments usually is predomi- 

 nantly composed of minerals, particularly the platy clay minerals and/or skeletons of 

 micro-organisms. An inverse relation of mineral particle size to surface area is well 

 known; however, that skeletal remains of micro-organisms, particularly diatoms, have 

 large surface areas is somewhat less well known. Electron photomicrographs of siliceous 

 diatom shells by Helmcke (1951) and Helmcke and Krieger (1951, 1952) show that the 

 surface area of diatoms Ss enormous. In a clay-mineral investigation of selected Area 

 C samples, J . C Hathaway (report in preparation) determined the amount of skeletaS 

 remains of diatoms, coccoliths, and other micro-organisms by electron microscopy of 

 the fine silt- and clay-size fraction. He found that the high water contents of these 

 samples correlated with large concentrations of skeletal remains. In samples possessing 

 essentially identical clay mineralogy, water content appears more closely related to 



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