F-27 



the macro-benthic community only along the individual tracks. 

 Furthermore, the sled is difficult to maintain in bottom 

 contact on the particularly steep slopes where most of the 

 outcrops occur. The photography is thus somewhat biased 

 against recording outcrop and may overemphasize the sub- 

 strates lacking outcrops. 



The outcrop as mapped acoustically, is much more ex- 

 tensive than the outcrop mapped photographically (which may 

 be covered by only a thin veneer of sediment) . The acoustic 

 outcrop has been verified only locally by dredging, by the 

 few submersible transects particularly along the thalweg 

 edge, and by sled photography. The distribution pattern of 

 the present outcrop is that which was produced by the recent 

 phase of axial cutting. 



Slumping of surficial thin sediment aprons is not pre- 

 valent within the canyon proper, probably because of the 

 presence of indurated older material at shallow burial 

 depths. Large-scale surficial slumping has been detected 

 only near the mouth of Oceanographer Canyon and along the 

 adjacent external slope. Tear-shaped patches of small-scale 

 roughness occur here at depths below 1000 m. They are 

 interpreted tentatively as slump scars and have the associa- 

 ted chaotic debris flow deposits. Their locations correlate 

 with those parts of the margin where the younger sediments 

 have their thickest expression. The largest slide blocks 

 in Baltimore Canyon also correlate with the presence of 

 exclusively young and more loosely-consolidated materials. 



