GEOLOGICAL OBSERVATIONS FROM THE BATHYSCAPH TRIESTE NEAR THE EDGE OF THE CONTINENTAL SHELF OFF SAN DIEGO, CALIFORNIA
Two bathyscaph dives were made crossing the outer continental shelf, the break-in-slope, and the upper basin slope off San Diego. Dive traverses were along previous survey lines made with acoustic reflection profilers, and observed rock attitudes and sediment thicknesses verified the geophysical data. Outcropping rock on shelf and slope and very steep (35°) sediment-covered slopes were observed. Variations in benthic organism populations at different localities suggest environmental control of organic transport of sediment. Continuous observations along traverses showed gradational textural contacts in sediments with coarsest silty sand flanking the shelf break. Wave induced orbital currents, sufficient to maintain a turbid layer of suspended fine sediment, were seen over the bottom. This wave motion, together with other current, must be more effective in preventing permanent deposition in the zone flanking the shelf break than in shallower or deeper zones of the shelf and slope.