These depressions acted as "windows" to the underlying substrate as 

 the sand cover appeared to consist only of a thin (< 3 m) veneer. 

 Along the two northernmost survey lines, some depressions were 

 noted to exhibit a pattern subtly suggestive of bedform development 

 (Figure 3-28) . Sandy gravel to gravelly sand patches with 

 occasional boulders characterized Unit 3, found primarily in one 

 area to the southeast. Along the southeast perimeter of Brenton-A, 

 a coarser unit was observed. Unit 4 consisted of gravel, sand and 

 boulders with occasional megarippled sediment patches and sandwave 

 forms (note the classification used herein, after Boothroyd and 

 Hubbard, 1975, defines megaripples as bedforms with spacing of 0.6 

 - 6.0 m; forms of spacing >6 m are sandwaves) . Bedform crest 

 orientations, mapped where observed, aligned predominantly west- 

 northwest to east-southeast (Figure 3-28) . Location of stations 

 and results of grain size analyses (Figure 3-29 and Table 3-6) 

 confirmed the side scan interpretation; the major mode for most 

 stations was sand or gravel, with the exception of the furthest 

 station to the south (50% sand, 50% silt-clay) . 



Brenton-B : Five textural bottom types were observed on 

 side scan sonographs from the Brenton-B area (Figure 3-30 and Table 

 3-5) . Bedforms characterized all but two of the bottom types 

 mapped. Unit 1, comparable in texture to Unit 1 in Brenton-A, 

 represented a megarippled sand field. Bedform distribution was 

 fairly ubiquitous; forms averaged 1 m in wavelength (spacing) . 

 This pattern was observed along the axis of the 35 m closed contour 

 depression in the northern half of the survey area. Unit 2 was 

 marked by sand with megarippled, gravelly sand depressions. This 

 unit was comparable to Unit 2 in Brenton-A; however, the coarse- 

 grained "windows" consistently exhibited bedforms. This bottom 

 type was found primarily in the northwest corner of the area, along 

 the flanks of the surface depression. Brenton-B Unit 3, observed 

 in the southeastern corner, exhibited the same texture as Unit 3 in 

 Brenton-A: sandy gravel to gravelly sand patches with occasional 

 boulders. Unit 4 in Brenton-B was also analogous to that mapped in 

 Brenton-A; however, bedform development was more widespread in 

 Brenton-B. This surface unit (Unit 4) predominated, and was 

 observed in the northeast corner on a bathymetric high and 

 throughout much of the southern half of the area. Unit 5 

 represented uniform sand (no bedforms) and characterized a 

 depression in the southeast quadrant of the surveyed region. 

 Bedform crest orientations in Units 1, 2, and 4 were aligned 

 similarly to those observed in Brenton-A (Figure 3-30) . Results of 

 grain size analyses (Figure 3-31 and Table 3-7) again confirmed the 

 major modal sediment grain size to be sand or gravel; only one 

 station had a predominant silt-clay fraction (53%) with a sizeable 

 sand component (46% sand, 1% gravel) . 



Prudence : Side scan observations revealed four different 

 bottom types within the historic disposal site off Prudence Island 

 (Figure 3-32 and Table 3-5) . However, as will be discussed, the 

 differentiation appeared unrelated to depositional history or the 



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