sized nodules. These are indicative of 

 slow rates of deposition in these areas. 



Along the edge of the shelf, the 

 foraminiferal sands and silty sands 

 contain the mineral glauconite which 

 is an indicator of slow sedimentation 

 rates. These are also indicated by high 

 potassiunn values in the tabulated chem- 

 ical data. 



Some of the shelf sediments are 

 iron-stained. Others contain some 

 small phosphorite grains. All indicating 

 that the present sediment surface is 

 either one of slow accumulation or is 

 an old pre -Recent sediment cover. 



The association of foraminiferal 

 sands and the more normal shelf sedi- 

 ments is strikingly similar to patterns 

 along the shelf and slope of the South 

 and East China Sea, along which the 

 great Japanese Current flows. Niino 

 and Emery (1959) have illustrated pat- 

 terns from that area which are almost 

 identical with those of the area covered 

 by the Gill cruises. 



The chennical data tabulated in this 

 report reflect the generally simple 

 composition of the sediments. Much of 

 the insoluble material is silica in the 

 form of detrital quartz. The carbonate 

 is predominantly in the form of shell 

 fragments and other organic debris. 

 Calcareous rock fragments of older 

 terrains are negligible or absent. Some 

 rock fragments are present in two or 

 three samples from the northern inner 

 shelf. Heavy mineral percentages are 

 usually less than 1 percent and rarely 

 as much as 2 percent. 



The principal sources of the iron 

 and phosphorus is apparently the shell 

 debris. In the samples in which iron 

 staining and phosphorite are present 

 these values are markedly increased. 

 Potassium is low except where glau- 

 conite occurs. Alumina, strontium and 

 manganese are all present in very 

 small quantities in the organic debris 

 except in the samples containing man- 

 ganese nodules in which the manganese 

 percentages beconne very large por- 

 tions of the total sample composition. 

 In general, the strontium contents are 



highest in areas of shell debris and 

 authigenic mineral concentrations, and 

 low in the foraminiferal sediments. 

 Magnesium is highest in the shell frag- 

 ment sands and low in the calcareous 

 foranniniferal sediments. 



Modern sedimentation appears to be 

 active in the inner shelf and in the 

 slope areas but is absent or very slow 

 over the outer shelf, the inner Blake 

 Plateau and in the areas of authigenic 

 mineral formation at the shelf edge 

 and the central Blake Plateau. 



STATION AND SAMPLE 

 LOCATIONS 



The positions of the samples of 

 bottom sediments tabulated in this 

 report are shown in figures 5 through 

 7. When positions are identical for 

 several different samples, all are 

 shown in bold type immediately above 

 the station position. Sample data are 

 tabulated in order of station num- 

 ber in the data section of the 

 report. 



The precision of station location is 

 not sufficient to place the individual 

 samples within an area smaller than a 

 3- to 5-mile circle; therefore, when 

 considerable variability is present in 

 sample textures it is not possible to 

 show these variations in their true 

 relationship. The variations are real 

 and are all larger than the margin 

 of error in the analytical procedure. 

 In those examples where the variabil- 

 ity is quite small, it will probably be 

 permissible to assign variability in 

 other parameters to seasonal changes. 

 At stations where textural variability 

 is large, seasonal variations will be 

 obscure and should be made with great 

 caution. 



One additional caution with respect 

 to the interpretation of the tabulated 

 data is that patterns of sedimentological 

 characteristics should be described 

 in no greater detail than the mini- 

 mum sample spacing. It is not valid 

 to draw detailed or definite lines of 



19 



