1 The 200-meter isobath is again in blue, which is a good indicator 



2 .of the rims of the canyon. The point I want to make from this slide is 



3 that around the heads of each one of the canyons, even on the shelf, 



4 there is an accumulation of finer-grained silts and clays. 



5 This was a fairly thin veneer, only a few meters thick at the 



6 outer edge of this, but both around the head of Lydonia and the head of 



7 Oceanographer, and on the shelf itself, there is indication of a 



8 depositional environment. 



9 It's not clear whether this is happening as the result of current 



10 processes or past processes, but there are finer-grained sediments 



11 around the canyon heads than on the adjacent shelf a few tens of 



12 kilometers away. 



13 If you look down the axis of the canyon, this is a section from 



14 the southern flank of Georges Bank, to 1,500 meters in Lydonia Canyon. 



15 Here is the depth profile and the ticks on this axis show the locations 



16 of the samples. This was retained by Alvin in the axis along the floor 



17 of the canyon. 



18 I've just shown very crudely, broken the texture into three 



19 categories, silt-plus-clay, sand, and gravel. You can see, as you go 



20 down the axis of the canyon, the overall trend is for increasing amounts 



21 of silt-plus-clay or increasing depositional environment, but there is 



22 an area near the head of the canyon in about 300 to 400 meters of water 



23 depth, where there is an excess on the order of 30 to 40 percent silt- 



24 plus-clay. 



25 The sediments then coarser at about 500 meters, and then get finer 



26 again. We'll see that the current strengths mirror this sediment 



27 distribution along the axis where they are weaker here, stronger here, 



28 and weaker still again in the deeper part of the canyon. 



29 The canyon is really complex topographically. At the moment, 



30 disregard the current meter stations on this base map. I just wanted to 



31 show you the morphology. Lydonia Canyon is about 5 kilometers wide at 



32 the mouth, where it cuts back into continental shelf at the 200-meter 



33 isobath. 



21 



