Surface sediments in both Brenton-A and Brenton-B were 

 composed of sand, gravel, and boulders derived from wave and 

 current reworking of the glacial drift deposits. Coarse, gravelly, 

 boulder-strewn areas (units 3 and 4) were found adjacent to areas 

 characterized by a thin (< 3 m) , patchy sand veneer (units 1, 2, 

 and 5) . Depressions or "windows" in this veneer revealed that the 

 sand overlies the coarse, gravelly surface. Megaripples and 

 sandwaves, which occur in response to current speeds in excess of 

 50 cm/ sec (1 kit) , were observed in both areas, but were more 

 widespread in Brenton-B. These forms are capable of reworking the 

 upper 30 cm (megaripples) to 1 m (sandwaves) of surface sediment. 

 Bedform orientation indicated a net transport direction to the 

 south-southwest. It is believed that these forms developed in 

 response to northeasterly storm winds. Subtle differences in 

 relief, producing subtle differences in hydraulic regime, or the 

 resolving capability of the side scan system may account for the 

 disparity between bedform observations in the two locations. 



The historic dredged material disposal site southeast of 

 Prudence Island lies in the East Passage trunk valley, a prominent 

 branch of the pre-glacial drainage system. Glacial drift and 

 Holocene estuarine sedimentation have infilled the valley. Data 

 indicated that at least the upper 8 m of sediment consisted of silt 

 and sand, of which the top 1.5 m had been highly disturbed (mixed) . 

 Side scan data revealed mound-like features (< 2 m in height; 10 - 

 20 m in diameter) on an otherwise uniform surface. These forms did 

 not appear to be wave- or current-generated. Trawl marks and fish 

 pots observed on the sonographs were evidence of man's activity in 

 this area. 



Based on these results, it appeared that areas Brenton-A 

 and Brenton-B did not contain any "quiescent" silt-clay 

 depositional basins; these were found only in the historical 

 Prudence Island Disposal Site. There appeared to be a silt-clay 

 facies to the south of the existing disposal mound at the Brenton 

 Reef site, but the steep gradient in bathymetry, grain-size, and 

 biological community type on the historical mound indicated that 

 the seafloor would experience a different hydraulic regime with a 

 3-5 meter elevation above ambient depths (33 meters) . 



The benthic communities around the Brenton Reef disposal 

 mound showed a full recovery in population density since the 

 cessation of disposal operations. Dense ampeliscid beds were 

 observed on the ambient seafloor within and outside the site as 

 well as on the edge of the mound; a mobile sand community dominated 

 the mound central area where a distinct transition in sediment 

 grain size occurred. The density of lobster traps on and around 

 the disposal mound attested not only to the benthic community 

 recovery but to the enhanced fishery resource which exists at the 

 site. 



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