IV. RESULTS 



General 



A total of 1243 photos were taken at the 

 fifty-four stations shown on Fig. 3. Of these, 

 approximately two thirds, or about 800 frames, 

 were close enough to the bottom to show some 

 evidence of lithology, current activity or or- 

 ganisms. About one sixth or 200 of the frames, 

 generally taken close to the bottom (within 1 

 fathom) could be categorized as good to excel- 

 lent. The photographic information collected at 

 each station is summarized in Table II. 



This table includes the following data for 

 each station studied : film roll and frame num- 

 ber, quality of photographs, bottom surface 

 area covered, bottom textural types, ripple 

 marks and other current indicators, organisms, 

 and other pertinent observations. Selected rep- 

 resentative photographs of the bottom at most 

 of the stations are presented in Plates 1 to 34. 

 A brief summary highlighting sediment tex- 

 ture, inferred bottom current directions, and 

 organisms recorded on film is presented below. 

 Figures 7 to 10 have been compiled by plotting 

 data summarized in Table II. 



Sediment Texture 



The contoured regional distribution of major 

 sediment textural types (sediment grain size 

 mixtures) is shown in Fig. 7. The textural 

 terms used are those employed by sedimentolo- 

 gists (Pettijohn, 1957). Textural interpreta- 

 tions were verified by coring, where possible, 

 and by comparison with sediment notations of 

 Stetson (1949) and Hathaway (1966, 1967). 

 Coarse to medium sand occurs near the outer 

 shelf margin and the head of the Wilmington 

 Canyon to depths somewhat in excess of 50 

 fms. Sandy silt and silty sand actually drapes 

 the shelf edge and uppermost continental 

 slope. This material also fills the upper canyon 

 head and extends as a tongue down the axis to 

 about 500 fms. Greater photographic coverage 

 in the canyon could indicate that this tongue 

 actually extends further downslope. Silt and 

 clay admixtures (material finer than 0.0625 



mm) increase and the relative percentage of 

 sand (0.0625-2.0 mm) decreases substantially 

 below 50 fathoms. However, local concentra- 

 tions of sandy sediment are noted at greater 

 depths, particularly on the Nyckel Ridge (Sta- 

 tions 43, 48, 50 and 52) , to about 1500 fms. 



Pebble and cobble-sized material (coarser 

 than 2.0 mm) appear to be concentrated in 

 three areas. A tongue of coarse material on the 

 steep east wall of the canyon head extends 

 from the shelf edge to depths exceeding 300 

 fms. Boulders, some exceeding 1 m. in diame- 

 ter, occur near the axis at Stations 13 and 17. 

 An isolated gravel location (Station 29) was 

 encountered on the southwest canyon wall at a 

 depth of about 150 fms. Gravel, with sand and 

 mud, also occur on the upper rise near the Ny- 

 ckel Ridge at Station 49 and north of the can- 

 yon axis at Station 52. 



Below about 100 fms silt and silty mud cov- 

 ers the canyon proper and the continental slope 

 and rise. The slope east and north of the can- 

 yon tends to be covered with soft clayey mud. 

 Stiff clay is noted at several deep stations par- 

 ticularly those on or near the Nyckel Ridge in- 

 cluding Station 41 at 930 fms. Small muddy 

 lumps of granule size in silt and clay sedi- 

 ments, common in some slope and rise stations, 

 are probably of organic origin and may be fae- 

 cal pellets (Table II). 



A rock outcrop was noted at Station 43 on 

 the Nyckel Ridge at the base of the slope. This 

 large, parallel-bedded ledge is more than one 

 meter thick and displays a series of distinct 

 linear fractures (Plate 27, fig. A). Angular 

 rock fragments broken from the leading edge 

 of the ledge lie at the base of the outcrop 

 (Plate 27, figs. B-D) . The presence of a thin ve- 

 neer of silt on the rock slabs in shown in Plate 

 28 (fig. A). 



Inferred Bottom Currents (Neocurrents) 

 and Sediment Movement 



The photographic survey makes it possible 

 to detect the evidence of recent bottom current 



81 



