SECT. 3] 



TURBIDITY CURRENTS 



749 



current and provide additional evidence of the mode of emplacement of the 

 Mediterranean deep-sea sands which Bourcart (1953) had previously inter- 

 preted as turbidity- current deposits. 



Bourcart and Glangeaud (1956, 1958), however, objected to the interpretation 

 claiming that turbidity currents had broken only the cables on the steep slopes. 

 To explain the later breaks out on the nearly level ocean floor they suggested 

 that undetected or at least unlocated aftershocks had caused the breaks. 



•5 



in 

 a. 



o 



3 

 CC 



10 20 30 40 50 60 70 80 

 NAUTICAL MILES RUN 



Fig. 8. Time-distance furve for the 1954 Orleansville turbidity current. Note that the 

 velocities determined are of the same order of magnitude as those determined for 

 the 1929 Grand Banks turbidity current (shown in Fig. 3). (After Heezen and Ewing, 

 1955.) 



Apparently impressed by Kullenberg's objections to the computed velocities 

 for the Grand Banks turbidity current, they sought an alternative interpreta- 

 tion not requiring such high velocities. Also misled by bad soundings, they 

 denied the existence of an abyssal plain in the area. Precision soundings, 

 however, have confirmed the existence of the Balearic Abyssal Plain. 



3. Alternative Explanations 



A number of novel explanations had been offered in an attempt to provide an 

 alternate explanation of the events following the Grand Banks earthquake, 

 Shepard (1954) now admits that turbidity currents transport sediments, but 



