piston cores collected from the head of Lydonia; the data show a near-linear 

 increase of age with depth, which suggests a constant and ongoing accumulation 

 of sediments at these locations over the last few thousand years (Figure 12). 

 The mean accumulation rate is 60 cm/1,000 yr or about 2 g/mVday. 



The carbon-14 age of the surface sediments is about 900 years, which 

 reflects the slow exchange of atmospheric and oceanic carbon dioxide and 

 bioturbation of the surface sediments. 



The calculated rate of sediment accumulation from piston cores is at 

 least an order of magnitude less that the rate of sediment accumulation in 

 traps. Although the efficiency of the traps is not known, this implies that 

 canyon sediments are subjected to numerous cycles of resuspension and 

 deposition before final burial. These cycles are thought to increase the 

 opportunity for scavenging of dissolved contaminants by particles. 



The rates of sediment accumulation have not been determined on the open 

 slope adjacent to Lydonia Canyon. The closest carbon-14-dated core on the 

 slope was taken south of Martha's Vineyard in 1,100 m of water, where a rate 

 of 13 cm/1,000 yr was reported (Anderson and others 1988). The rates of 

 sediment accumulation on Georges Bank are assumed to be nil. Redistribution 

 of materials is occurring, but because of its present isolation from 

 continental sources of sediment, the Bank as a whole is considered erosional. 



Transport of material from the continental shelf into the axis of Lydonia 

 Canyon is directly evidenced by the systematic increase with time in the 

 concentration of barium in sediment trap samples (Figure 13). The first 

 mooring deployment predated the exploratory drilling on Georges Bank and the 

 remaining four deployments included the period when eight wells were drilled, 

 the closest about 9 km away from mooring LCB. 



The barite component of drilling mud, the source of this barium increase, 

 was highly diluted by the time it was collected in Lydonia Canyon. It was 

 measurable only in the fine fraction (finer than 50 microns) of the trapped 



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