1 to rise some 12,000 to 15,000 years ago. He also surmised, however, 



2 based pretty much on intuition, that these accumulations would be 



3 continuing in the present. 



4 He used, as I say, the basis for this hypothesis that the 



5 morphology of the deposits related to little channel cuts and so forth, 



6 and the fact that the current measurements were suggesting that Lydonia 



7 Canyon could be a trap for material coming off the shelf. 



8 Well, I'm here to say that the more recent geochemical evidence 



9 implies that there is still a place for intuition in marine geology, 



10 because we cored the upper regions of the canyon, we measured the 



11 carbon-14 activity as a function of depth in these cores, and we found, 



12 in fact, that there is a fairly linear increase in age, which suggests a 



13 fairly continuous rate of sediment accumulation at two locations in the 



14 head of Lydonia Canyon at about 150 meters water depth. 



15 The rates of accumulation in this particular area are on average 



16 60 centimeters per 1,000 years. That represents about 2 grams/meter^ 



17 per day. That's at least on an order of magnitude less than what we can 



18 catch in our sediment traps, which I will remind you does not have good 



19 information about the efficiency. 



20 If you assume that the efficiency is okay, that tells you that 



21 there's recycling a number of times before this material actually ends 



22 up in a sedimentary record at the head of Lydonia Canyon. 



23 I'll go to the next slide, which shows something about where the 



24 sediments are coming from. Our sediments in Lydonia Canyon, this is at 



25 LCB at 300 meters. The deployments were carried out before drilling 



26 began on Georges Bank and continued throughout the entire drilling 



27 period. 



28 We measured the fine fraction of the material collected in the 



29 sediment traps near the bottom, and found that the concentration of 



30 barium in these sediments started off at a low level, which we assumed 



31 to a consistent representation of background, and then increased 



32 systematically with time as the drilling progressed. 



65 



