70 



HISTORY OF THE OCEANS 



Stone. With the curve of Wyllie et al. (1956) the velocity was pre- 

 dicted within less than 2% prior to the actual determinations. 

 Randomly oriented calcite grains in a pure rock of zero porosity 

 would have a velocity of about 6.8 km/sec, which represents the 

 highest theoretical value for velocity in a limestone (Wyllie et al., 

 1956). Field and laboratory data, however, show that the highest 

 value normally to be expected should be about 5.9 km sec, al- 

 though a few velocities of the range 6.1 to 6 45 km,/ sec have been 

 reported by Birch et al. (1942) and Hicks and Berry (1956). 



Discussion 



We are principally interested, here, in the actual held variations 

 of velocity with depth (Fig. 8). Faust (1951), in his study of these 



VELOCITY, KM/SEC 

 2.5 



Fig. 8. Variation of velocity with depth. Shale sections (Faust, 1951; West, 

 1950) and unlithified sea floor sediments to 300 m (Nafe and Drake, 1957) com- 

 pared with seismic refraction information of Ofificer and Ewing (1954) and Ewing 

 and Ewing (1959). These field determinations are contrasted with laboratory ex- 

 periments on terrigenous mud (Laughton, 1957). 



