60 



HISTORY OF THE OCEANS 



Table I. Consolidation of Clay and Shale (curves from Skeels, 1950; 



Skempton, 1953)° 



"Assumption: 300 m of clay overlie shale with 100% hydrostatic uplift effective. 

 Properties: density of solids, 2.31 gr/cc; water density, 1.05 gr/cc; initial porosity, 72%. 



which illustrate the variations of the various properties with 

 depth. In Figure 4 there are several noteworthy points: (1) a fast 

 decrease in porosity to 'i'^ to 45% at depths between 150 and 300 

 m; (2) little difference between the curves computed for clay with 

 a grain density of 2.70 gr/cc and that for a clay with 2.31 gr/cc 

 based on the average of 18 determinations on Pacific red clay; 

 (3) the very close likeness of the computed curves to the actual 

 conditions in the Tertiary of the Gulf Coast area; (4) the marked 

 difference between the porosities of clay at depth and that for a 

 calcareous ooze. 



