Cores 62-27 and 62-57 show a very sharp break In color at various depths in the 

 core. Core 62-37 changes abruptly from a yellowish gray clayey silt to a pure white 

 clayey silt with no apparent change in grain size or constituents. The white area is 

 underlain by material similar to that above it, and the pattern is repeated within a 

 few centimeters depth. The white area is far more cohesive than the material above 

 and below it. 



Cores 62-36, 62-38, and 62-39 ore similar in most respects to the normal near- 

 flank sediments, except for one or two zones of relatively coarse particles intermixed 

 and separated from each other by finer material. These zones do not resemble layers 

 which might have originated through turbidity current deposition but appear more like 

 the result of sand "falls"; however, reworking oFthe material by organisms may have 

 destroyed the original bedding, although other evidence of such activity is lacking. 

 Sample 62-6, a grab sample, consisted of very coarse reef detritus, apparently from 

 the nearby Andros Island barrier reef, and displayed the coarsest grained material of 

 any taken from the channel. 



Particle Size : Table 1 gives quartiles, median diameter^ quartile deviation 

 (QDj^ and skewness (Skq^ values of subsamples from cores and grab samples in the 

 near-flank area. Some general relationships are given below: 



Ql/and Q3/ = 1st and 3rd quartiles, respectively, 

 Md/ = Median diameter, 

 QD/ = i (Q3 - Ql), and 

 Skq/= i (Ql Q3 - 2Md). 



In all samples (except three) the median diameter is within the range of silts, 

 end, as well be shown later, this is by far the predominant particle size of the bottom 

 sediments throughout the channel. The average grain-size distribution of near-flank 

 sediments is 14 percent sand, 61 percent silt, and 25 percent lutite. 



The quartile deviation (QDx^) is a measure of the average spread of points around 

 the median (sorting), and when perfect sorting is obtained QD/i is equal to zero. The 

 sorting values in Table 1 show an almost equal number of poorly-sorted and normally- 

 sorted samples. This Is in sharp contrast to 1 1 ling (1954), who found sorting values for 

 the adjacent bank sediments to be so uniformly low that it was necessary to break down 

 the well -sorted category into smaller increments In order for the values to be meaningful, 



Quartile skewness (Skqiii) is a measure of the symmetry or asymmetry of the curve of 

 particle-size distribution. If the curve is perfectly symmetrical, then Skq<^ is equal to 

 zero. If the spread of particle size is greater on the fine side (positive values) of the 

 median diameter, then Skqi^ is positive, or if greater on the coarse side, then the value 

 is negative. The greater spread of particle sizes on the fine side of the median diameter 

 in these sediments shows the dominance of fine material In the near-flank area and may 

 be the result of sediment winnowing by waves and currents on the shallow banks adja- 

 cent to and above this area. Water movement on the bank may stir up the bottom ma- 

 terial and allow the coarser grains to resettle while maintaining the finer debris In 

 suspension. The fine material is then carried to the edge of the bank, and, due to a 



16 



