78 1965), the 226p, initially accumulated by coral gradually decays with time in the sediment column as it is buried, and then later slowly increases to equilibrium with 2307), and 234y as 2307), grows in from 234), Thurber et al. sp. cit.) found that this equilibrium was establisned at a depth of about 24 meters in drilling cuttings from an island at Eniwetok Atoll. The results of the measurements of uranium and 226p, concentrations in lagoon surface sediments are shown in Table 13. Unfortunately, the uranium analysis made on this batch of samples resulted in low chemical yields and th e 239+240 Pu background peak, previously described, could not be resolved and subtracted from the 232) tracer peak; therefore, the uranium concentrations in Table 13 may be systematically low by up to 10%. Because the total number of counts measured in these samples was small (note the concentration error term), the uranium concentrations given should be viewed only as preliminary observations. Despite the uncertainties noted above, the 238) concentrations measured (with the exception of the concentration measured at Station B-20) fell within a concentration range of 0.68-1.2 pCi/g which is similar to the 1.1 - 1.2 pCi/gm values reported in Eniwetok Atoll soil-sediment (before the beginning of nuclear testing) by Thurber et al. (op. cit.). The spread of the uranium concentrations measured is similar to the variations found by other investigators in different types of carbonate secreting organisms (Sackett, 1972; Sackett and Potratz, 1963). The distribution of the radionuclide activity ratio 226,. Ra/-~ ,234 “U in several of these Bikini sediments (Table 13) show significant departure from the value of 0.09 which is characteristic of recent Eniwetok corals (Thurber et al.,op. cit.). With the exception of the intermediate ratio at Station B-3, the sedi- ments from stations previously found to be outside of the regions of greatest radionuclide contamination (the stations above the dotted line in Table 13)