1 Lydonia Canyon. This was documented with side-scan sonar by Brad and 



2 his colleagues. 



3 He deployed a current meter there that documented this strong 



4 westward current. We dived on that gravel patch to confirm that it was 



5 actually gravel. It's very similar to what we saw in Oceanographer 



6 Canyon. 



7 This is the head of Oceanographer Canyon, the green areas are 



8 gravel patches, we can show areas where currents are fairly strong. The 



9 point of this slide is to show depositional areas of very fine sand, 



10 which is 4-fee [phonetic] size sand, which is just about the silt size. 



11 This sand travels in suspension when it travels. So, the yellow 



12 color indicates areas where there's less than 10 percent of very fine 



13 sand. Those are areas of the canyon axis and of the west arm here, and 



14 of the east arm where currents are vigorous. 



15 The blue and the purple show areas of increasing concentration of 



16 very fine sand so that the purple areas of 40 to over 50 percent very 



17 fine sand. 



18 Now, these appear to be areas where currents are weaker around the 



19 canyon, we've seen that there are strong currents around other parts of 



20 the canyon. 



21 These two areas appear to have weakened currents, and it's 



22 possible that this very fine sand is partly coming from the shelf, but 



23 could also partly be coming from the canyon, since Oceanographer Canyon 



24 has a very vigorous axial currents, which I'll describe in a minute. 



25 The walls of all of these canyons are underlain by a Pleistocene 



26 silt and clay, which is fairly stiff, but it's not hard or rocky in any 



27 sense. This shows a bioeroded segment of the canyon wall. 



28 Some canyons have more exposures of this silt than others, and 



29 thus are more bioeroded than others. The fragments that are eroded by 



30 these organisms are mixed with the shelf sand coming over the rims of 



31 the canyons. 



32 This combination makes it way down the walls and onto the canyon 



33 floor. This is looking up the west wall of Oceanographer Canyon, 



34 looking up the slope of wall, so that these ripples are oriented 



38 



