SECT. 1] 



CONTINUOUS KEFLECTION PROFILING 



65 



reflectors except where it protrudes to form abyssal hills. The identity of the 

 rough surface and the shallower layers has not been firmly established, but it 

 seems certain that the rough surface is either the top of the deepest crustal 

 layer having a velocity close to 6.5 km/sec (sometimes called layer 3) or the 

 top of one of the layers of intermediate velocity, 3.0 to 5.5 km/sec, sometimes 

 called layer 2. In the short time we have been recording reflections continuously 

 in the deep ocean several recordings, widely distributed in location, have 

 shown multiple layering, as in Figs. 12, 13 and 15. One is led to wonder whether 

 generalizations like layers I, 2 and 3 are not now over-simplified as means of 

 classifying oceanic structures. 



Echo - sounding - 

 receiver 



^i^^te 



Ship drifting 



Telemetering 

 (well logging cable) 



Comera ond 

 hydroptione or source 



Buoyant line 



Source or liydrophonc 





Fig. 17. Bottom seismic gear for deep-water use. 



E. Seismic Refraction Observations 



Scientists from both the Lamont Geological Observatory and Woods Hole 

 have recorded refraction arrivals during oblique reflection profiles. Fig. 16 is 

 representative ; refraction arrivals recorded in this manner with high enough 

 signal-to-noise ratio will be invaluable in supplementing present refraction 

 techniques with explosives. Continuous refraction profiling should prove 

 especiaUy valuable in the study of unconsolidated sediments in deep water 



