SECT. 3J 



PHYSICAL PROPERTIES OF MARINE SEDIMENTS 



807 



serve to provide estimates of density from velocity in the absence of any other 

 information. Cracking of samples or the presence of small amounts of gas in 

 samples of ocean sediments will have the effect of reducing velocity for a given 

 density, and anhydrites have exceptionally high densities for a given velocity. 

 In drawing the curve of Fig. 4, therefore, relatively less weight was given to 

 observations for which velocity reduction or density increase from such causes 

 is a possibility. 



Density (g/cm^) 



Fig. 4. Conipressional velocity as a function of density. Most observations on ocean sedi- 

 ments lie below 2 km/sec in velocity. 



All points plotted in Fig. 4 represent observations on water-saturated 

 materials. Those published values for which the degree of saturation was not 

 indicated have been omitted. 



It is interesting to note that when data for igneous and metamorphic rocks 

 are plotted together with those for sedimentary rocks the velocity-density 

 curve may be continued upward to higher velocities with no noticeable offset, 

 though the curve has a slight decrease in slope. 



D. Shear-Wave Velocities and Poisson's Ratio 



The information that exists on shear-wave velocities in marine sediments 

 consists mainly of direct measurements by Laughton (1957) on artificially 



