724 



EIGHTH PACIFIC SCIENCE CONGRESS 



dicative of variations in particle size distribution from samples only 

 one foot apart. 



Differences in Grade Size Percentages * 



♦ These are approximations based on the analysis of cores from .36 of the 60 locations. 



Very often the data from sediment size analysis are reported in terms 

 of major fractions; such as sand-silt-clay ratios. Coarse, medium and fine 

 classifications are often used where coarse material includes coarse sands 

 and larger,, medium material represents a composite of medium and fine 

 sands and the fine matter is a summation of the amounts of silt and clay. 

 Using such a coarse-medium-fine differentiation for the sediments in 

 this study, the variations in frequency percent between categories of any 

 two adjacent samples is markedly increased. The slope area presents a 

 maximum variation of 33 percent for both the medium and fine frac- 

 tions. The base of the slopes shows a maximum variation between ad- 

 jacent samples, using this type of classification, is also significant in- 

 maximum variation for the mid-channel is 10 percent in the medium and 

 fine ranges. The average variation between the same categories of ad- 

 jacent samples, using this type of classification, is also significantly in- 

 creased. The slope area has an average variation of 10 to 12 percent, 

 the base of the slopes 6 percent, and the niid-channel region 4 percent.^ 



Sediments are often described and/or classified according to statis- 

 tical characteristics such as mode, median and quartile deviation. In 

 view of this a few examples of the similarities and differences in these 

 factors between immediately adjacent samples shall be presented. 



Figure 4 graphically presents the data from two sample locations. 

 Sample 6L1 is located on the east slope at about 560 feet below sea level. 

 Sample 1P2 is from the west slope, approximately 600 feet below sea 

 level. The first sample presents an exceptionally good match between 

 the three adjacent cores. The modes are the same, while the maximum 

 difference between the median diameters is very small, only 0.046 mm. 



* The approximate variations given here are the averages of the numerical differences in 

 the per cent of each individual category. For example: Core A — 40 per cent fine sand; Core 

 B — 20 per cent fine sand; the variation in the fine sand is thus 20 per cent. 



