239+240 concentrations of Pu (120 pCi/q) and 24 Lam (103 pCi/q) measured in any samples, occur at the focus of the “ellipse” at a location in the northwest quadrant of the lagoon about 6 km SSE of the Bravo crater. The highest concentrations of 155 Eu (139 pCi/a) were measured in samples collected along the northern rim of the lagoon. correction is made for the 155 If a radiological decay Eu concentrations measured around the northern rim of the atoll, it is found that the distribution patterns fo r 239+240 241 Pu, Am and 155 Eu across the lagoon are very similar. To the east of the focus of the "ellipse", the concentrations of 2394240, > 241 Am an d 155 Eu decrease approximately exponentially to: 2-5% of the concentrations found near the focus. tration of 137 Cs 137 Although the highest concen- measured (29 pCi/g) also occurs near the focus, the Cs concentrations decrease at a rate about 3.5 times faster per km than the 239+240 Pu, 24} Am and 155 Eu concentrations measured. In the northwest quadrant of the lagoon, a layer of fine sediments from 8 to 11 cm in depth was found covering the normal sedimentary deposits. Measurements of 234,238 U and 226). Ra:~~ .234 U ratios in samples of these finely divided sediments show them to be very old corals, presumably from the detonation craters. In two cores collected from this region of high radionuclide concentrations, the concentrations of and 155 239+240 Pu, 241 Am Eu decrease linearly with depth at a rate of about 50% through the layer of finely divided sediment. Sedimentation rates measured in one of these cores (using the distribution of unsupported 210 Pb concen- trations) show that the layer of finely divided sediment collected was deposited at an uniform rate between the 1950's and 1972. However, large differences in the ratios of 2394240, Pu: 238 Pu across the northwest quadrant