Figure 16. Manganese-encrusted sym- 

 metrical ripple marks in calcareous sand 

 on southwest slope of Eniwetok Atoll. 

 Depth: 1650 m. Photo area: 1 .2 m x 

 1.8 m. Type I camera. 2.4 m target 

 distance. 



Deep-sea ripple marks show as great a variety of 

 forms as those in shallow water. Variations in wavelength, 

 crest length, amplitude, and symmetry occur over very 

 short distances. 11 



Lack of ripple marks does not necessarily mean a 

 lack of water motion; it could mean merely an absence of 

 grains capable of being rippled by the moving water. Fine- 

 grained silts and clays in abyssal deeps will not ripple 

 regardless of the strength of the current. But scour marks 

 can result, providing evidence of currents in such areas. 

 Dzulynski and Sanders 38 hold that such marks are the result 

 of scour of a cohesive mud bottom (clay) by turbulent eddies 

 of sediment-laden water, and also that current marks can 

 be made in any depositional environment where sand is 

 transported over a cohesive mud bottom. These authors 

 also consider that "tool" marks result from fractional 

 movement of larger particles. Where the latter are lacking 



39 



