1 winnowed, to other canyons where fine-grained sediments are being 



2 deposited. 



3 This is the outer shelf/upper slope area east of Oceanographer 



4 Canyon. These show our sediment sample sites here. As you proceed from 



5 outer shelf to the upper slope, in this region the rather course shelf 



6 sand becomes somewhat finer-grained in this area, picks up some silt and 



7 clay, but then from about 200 to 300 meters, the silt and clay is absent 



8 and we have a course band of sediment in this region. 



9 Below 300 meters down into the heads of these gullies, the finer- 



10 grained component increases to about 30 to 40 percent silt and clay. We 



11 have the same scenario to the west of Heeltapper Canyon. So, we know 



12 this occurs at least in two regions. 



13 We hypothesize that the fine-grained sediment is being eroded from 



14 this 200 to 300 meter water depth band by warm-core ring currents, which 



15 flow here at speeds up to 50 to 60 cm/sec, based on current-meter 



16 observations from Brad's data to the east of Lydonia Canyon. 



17 This is a depiction of the warm-core rings in July, 1985. 



18 Basically they are packets of warm Gulf Stream water that pinch off the 



19 Gulf Stream and drift to the west and southwest and basically bump up 



20 against the continental margin and drift to the southwest and are 



21 eventually reabsorbed by the Gulf Stream. 



22 During this month there were four warm-core rings affecting the 



23 margin of Georges Bank. These rings can be from 50 to 150 kilometers 



24 across and they drift 5 to 8 kilometers per day, and can remain for many 



25 weeks in one area. 



26 This is a summary of 8 years of satellite tracking data of warm- 



27 core rings, and shows the margin has compartmentalized into segments 



28 here. The first number you see here is the number of warm-core rings 



29 during the 8 year period that affected the margin. 



30 The second number is the total number of months rings were present 



31 in that segment. So, that around Oceanographer and Lydonia Canyon, 



32 there were 19 rings present during that 8 years and they were present in 



33 that segment for 17 months, or on the average about 2 months a year. 



36 



