SECT. 3] 



TURBIDITY CURRENTS 



763 



modern turbidity-current deposits have been compared by them to those 

 described by Natland and Kuenen (1951) and others from the filled sedimentary 

 basins of southern California. Consideral)le attention has been given to these de- 

 posits since the analogous deposits in the filled basins are productive of petroleum. 

 Menard (1955) has employed the turbidity-current hyj)othesis to explain the 

 smooth topography, and the canyons, and the deep-sea channels of the North 

 Pacific. Locher (1954) and Phleger (1951), who studied the lithology and 

 fauna of the deep-sea sands from the equatorial Atlantic, became convinced of 

 their turbidity-current origin. Bourcart (1953) and Duplaix and Calleux (1956) 

 described deep-sea sands from the abyssal plains of the Mediterranean which 

 they identified as the deposits of turbidity currents. The concept has found an 



" ^^^v^ik 



AREAS INACCESSIBLE 

 TO SHALLOW-WATER 

 TURBIDITY CURRENTS 



HISTORICAL TURBIDITY 

 CURRENTS 



Fig. 17. Historical turbidity currents (since 1880). Each arrow denotes one or more 

 turbidity currents. With the exception of two off southern California, all are based on 

 submarine cable breakage. (After Elmendorf and Heezen, 1957.) 



increasingly greater application in paleogeographical reconstruction and a host 

 of recent papers have appeared which we will not attempt to review here. It 

 will suffice to say that Kuenen, his associates, and his students, as well as many 

 other independent workers, have had considerable success in identifying ancient 

 turbidity-current deposits throughout the world. 



There is now little doubt that turbidity currents play an important part in 

 the deep sea (Fig. 17). Their velocities have been determined by sequences of 

 cable breaks. The distribution of sands and silts in the deep-sea basins has 

 conclusively shown that the abyssal plains, archipelagic plains and smooth 

 continental rise areas owe their existence to the smoothing activity of turbidity 

 currents. The deep-sea sands, long an enigma of geology, are adequately ex- 

 plained by this process. It is clear that turbidity currents occur both as broad, 



