100 the core decrease steadily with increasing depth in the core. Because none of the 226n4 concentrations measured in these, or deeper, layers, differed ty an amount greater than 2 S.D. counting errors, it is not clear whether any real) (significant) concentret‘on differences exist between the three sections. Along with the 226 Ra and 210 Po concentrations measured in surface sedi- ments at Station B-2, the concentrations vs. depth in the core were used to determine the "sedimentation rates" based on the 2105, age dating technique. Typical resolution of the supported and unsupported 210 Pb in the core, using the available 2105, (224) concentrations and an average 226p4 concentration of 0.138 pCi/g, gives a "sedimentation rate" of 0.32 cm/yr in the upper 20 cm. This rate is clearly not possible, since only 18 years have elapsed since testing in 1954 and this rate would predict 63 years to accumulate the sedi- ment (20 cm?0.32 cm/yr = 63 yrs.). However, two observations suggest that the sediments below the 9-11 cm region in the core were deposited differently from those above this depth. The first is that the appearance of the sediments changed from entirely pulverized material to pulverized material and a small amount of Halimeda in and below the 8-10 cm section of the core, as discussed in Section 5.3-2. Second, the unsupported 210 Pb concentrations measured in 0-2, 4-6, 6-8 and 10-12 cm sections decrease exponentially with depth, indicating a constant sedimentation rate for the upper sediment layers. Below this depth the 2105, concentrations are not significantly different from the 226p, concentrations measured, indicating no unsupported 21054, rates" were thus calculated, using the four 2105), the upper 11 cm of sediment. The “sedimentation concentrations measured in Both the 0.138 pCi/g average, and best fit values of the 226pa concentration in the 0-16 cm layers of the core were used to calcu-~ late the concentrations of unsupported 21054, With the average 226 pa concen- trations, a rate of 0.56 cm/yr. is indicated for the upper 11 cm of sediment;