V. SUMMARY AND CONCLUSIONS 



Measurements of mass physical properties were made In the laboratory on 35 

 gravity- and plston-type sediment cores, ranging in length from 30 to 511 cm, col- 

 lected from ocean depths of 400 to 5120 m. Sample composition was predominantly 

 silty clay- and clayey silt-size material/ chiefly of terrigenous origin. 



The M.I.T. grain-size scale was used in classifying sediments instead of the 

 Wentworth scale because a silt and clay particle division at 9 / or 2/x appears more 

 significant in mass studies. A plasticity chart is applicable to deep-sea sediments; its 

 use, together with a triangular diagram, is recommended to marine geologists. Terrig- 

 enous inorganic sediments plot above and parallel to the empirical A-line on the plas- 

 ticity chart. Mixtures of terrigenous and calcareous sediments either plot below the 

 A-line or above it on a distinctly different axial slope from that of terrigenous inor- 

 ganic sediments. 



Grain-size was measured to 9 / and estimated to 10/. Statistical measures other 

 than median diameter were not applicable, because the size fraction finer than 10/ 

 was greater than 25 percent in most samples. Median diameter of particles showed a 

 variable relation with depth, in certain cores increasing and in others decreasing or 

 fluctuating with depth. Void ratio was found to be directly related to median diameter 

 for all 8 areas, although values scattered widely about the averages. When porosity 

 and median diameter data from other investigations were added to that of the present 

 one, the only clear relationship resulting was that low porosity sediments do not have 

 small median diameters. It was demonstrated that the field below a curvilinear line 

 extending from 7.5 /at 50 percent porosity to 10 /at 75 percent porosity, in an 

 arithmetic plot of porosity related to median diameter, was devoid of values. 



Corrections for salt content of interstitial water were not made in determining the 

 specific gravity of solids, wet unit weight (corresponding to in-place bulk density), 

 or measures of water content, because of the uncertainty of the magnitude of variations 

 in submarine sediments. Unfortunately, measurements of the salinity of interstitial 

 waters were not made. Specific gravity of solids for nearly 500 samples varied between 

 2.68 and 2.89, with an approximate average about 2.765. A first report is made of a 

 tendency for specific gravity of solids to be directly related to wet unit weight and 

 inversely related to porosity. 



Sediment wet unit weight ranged from 1 .23 to 1 .86 g/cm^ and increased with 

 increasing depth in most of the cores. Porosity was found to be inversely related to 

 wet unit weight, with values corresponding to those previously cited by others. The 

 different relationship of water content (porosity in water -saturated sediments) to wet 

 unit weight reported by Ratcliffe (1960) is not corroborated. 



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