Station 45 (Georges Bank) 



Sediment surface is uneven with numerous 

 small pocket-like depressions, ridges, and 

 mounds (fig. 6). A varied and unkempt ap- 

 pearance of the sea floor results not only 

 from microtopographic irregularities but also 

 from the patchy distribution of large mollusk 

 shells and several groups of living animals. 

 Tracks and trails are present but are not 

 particularly noticeable because of the generally 

 disturbed surface. Among the more distinctive 

 trails evident in the photographs from this 

 station are those of the sand dollar. This 

 species crawls on or through the sediment 

 with the aid of tube feet and the movement 

 of spines. Its progression along the ocean 

 bottom leaves a smooth flattened path with low 

 rounded ridge on each side (fig. 6, upper left). 

 Width of the path equals the body diameter. 

 Other common tracks are those of hermit 

 crabs and gastropods. 



The sediment appears to be primarily sand 

 containing a small amount of silt. Color ranges 



from dark to moderately light. Mollusk shells 

 are common; the small fragments are rather 

 uniformly distributed, in contrast to localized 

 aggregations of the large shells. The ocean 

 quahog and northern cardita, Venericardia 

 borealis , are the principal species whose shell 

 remains are identifiable. About half the large 

 pelecypod shells have the convex (outside) 

 face downward on the sediment, and the other 

 half have the concave (inside) face downward. 

 Shells with the convex face downward are 

 partially or completely filled with sand. 



Sediment taken with a grab sampler was 

 coarse to medium brown sand. 



Ripples in the sediment are relatively un- 

 common, but their conformation suggests they 

 are formed by the oscillatory action of waves 

 (see following section on Water Movement). 



Water Movement 



Evidence of water movement is revealed by 

 sand ripples sculptured in the sea floor 

 sediments in photographs at the three locations 



Figure 6.~Sea floor at station 45, southeastern Georges Bank, water depth 82 m. Identifiable animals: A. green sea 

 urchin, Strongylocentrotus drobachiensis ; B.Acadian hermitcrab, Pagurus acadianus ; C.Stimpson's distaff shell, 

 Colus stlmpsoni ; D. ocean quahog; E. sand dollar. Scale bar is 10 cm. long. 



S 



