20 19 (pCi/g) associated with the fine material at various depths in the sediment column exceeds the concentrations associated with the coarse components in both cores, the inventory of the radionuclide (pCi/em) within any depth interval assocfated with the fine and coarse components can be variable throughout the sediment colum. Areal transuranic deistributions like those shown in Figs. 2 and 3, but associated with only the fine or only the coarse component of sediment, would differ. The vertical distributions of the transuranics in the Lagoon sediment are very complex. No generalization about the shape of the concentration profile in any region can be made. shows a 241 Table 2, for example, Am peak associated with the fine components of core 6 at depths of 25 to 30 cm with little 2a associated with the coarse components at these depths. In core 1, the highest 24d concentrations are associated with the fine components between depths of 8 to 10 cm in the sediment column, The 24d concentrations associated with the coarse component in both cores generally decrease gradually with depth. fransuranic concentrations increase, decrease, or remain constant with depth in sediment cores from other lagoon locations (No78a). The concentrations of 23942405, and 241, associated with the carbonate components in four cores taken along a 1,5-km transect across Mike and Koa Craters are shown in Fig. 6, The concentrations in the sediments from the Atolls’ largest craters are surprisingly nonhomogenous,. Turbulence and large scale mixing of the sediments during and after testing should have produced a much more uniform distribution than that found. The 239-240 Pu concentration in the sediment column at station 17E is fairly uniform to a depth of 50 cm, At station 16E, concentration increases with depth to 35 cm. The 241 the Am concentration in the sediment column at station 16E decreases with depth. No correlation igs obvious between the PALay and 2394240Pu concentrations associated with the components of these crater sediments. The craters should act as natural sediment traps but little sedimentation in the Mike and Koa craters has occurred since the bottom depths were redetermined in 1964. In 1964 the maximum bottom depth of Mike Crater was 27.4 1 below sea level (Ne73), We have found no measurable change in the depth of the crater bottom during the period 1972-1977. Only small quantities of resuspended or reef-generated particulate material are then transported in the water masses to the western reef. Very little sedimentary material therefore escapes from the lagoon and any resuspended bottom material probably settles out again on the lagoon floor close to its origin. The complex areal and vertical patterns of transuranics detected in this relatively small region of the lagoon where the distributions are expected to be more uniform are but examples of the complex patterns in the lagoon. Halimeda, shells, coral, and foraminifera fragments were sorted from the coarse fraction of several sediment samples by hand. Table 3 shows the 23942405, concentrations associated with each component in the surface layer from two locations in Enewetak Lageon and at various depths in a core from Bikini lagoon. The 23942405, concentration associated with Halireda fragments at station 40C only slightly exceeds those in fragments from station 3D. The concentrations associated with por ARCHIVE