predictably with elevation. The combination of previous 

 experience, precision bathymetry, and REMOTS® photography made it 

 possible to place each station in the context of major gradients. 



3.2 Brenton-A, Brenton-B, and Prudence Areas 



3.2.1 Bathymetry 



Depths at the Brenton-A area ranged between 34 and 40 

 meters (Figure 3-23) . The western portion of the area surveyed 

 contained a closed depression having a maximum depth of 39.5 

 meters; it appears that this depression was formed by the 37 meter 

 contour, even though the survey did not extend far enough to the 

 southwest to confirm this. Smaller and shallower depressions 

 having maximum depths of 38.5 and 40 meters occurred in the eastern 

 portion of the region. 



The range in depths at the Brenton-B area was between 26 

 and 36 meters (Figure 3-24) . The northern half of this region 

 consisted of a relatively large, elliptical depression which 

 appeared to be formed by the 32 meter contour and which had a 

 maximum depth of 36 meters. In the southern half of the area, 

 there was a much shallower, irregularly-shaped depression which 

 appeared to be formed by the 35 meter contour. 



Depths at the Prudence historic disposal site ranged 

 between 17 and 31 meters (Figure 3-25) . This area was 

 characterized by a relatively long (roughly 2500 meters) and narrow 

 elliptical depression which trended northeast-southwest, roughly 

 parallel to the eastern shoreline of Prudence Island. The 

 depression, formed by the 21 meter contour, had a maximum depth of 

 31 meters. The walls of this depression were much steeper on the 

 seaward (i.e., eastern) side compared to the landward (i.e., 

 western) side. 



3.2.2 Seismic Stratigraphy 



Rhode Island Sound : In the vicinity of areas Brenton-A 

 and B, sub-bottom profiles revealed two major acoustic units in the 

 upper 40 m of section (maximum depth represented by the width of 

 the record) . The lower unit, >20 m thick, exhibited a diversity of 

 acoustic reflector patterns from chaotic to laminated (Figure 3- 

 26) . This unit, exposed at the seafloor over half of the survey 

 area, was inferred to be glacial drift and has been recognized by 

 other workers including Needell et al. (1983a and b) . The chaotic, 

 discontinuous reflector pattern may represent one or more of the 

 following: till, moraine, or ice-deformed drift. Continuous, 

 flat-lying to gently-dipping reflectors suggest stratification 

 characteristics of glacial outwash or glacial lake deposits. Where 

 not exposed, the top of this unit was marked by a high-amplitude, 



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