99 of the refractory radionuclides on the Ca0-Ca(0H)o - CaCO, particle matrix which was deposited here. Despite the source of 234y and 238) measured in these sediments, a slight 235y enrichment is indicated for the 8-10 cm sediment section by the low 238))235, ratio measured. If either of the second two possibilities given are responsible for the observed uranium concentration differences with depth in the core, the inereased concentrations of 226 Ra and 210 Pb, which appear to be similarly enriched in upper sections of the core, can be explained by the same process responsible for the elevated uranium concentrations. Similarly, since it is difficult to envision an artificial pathway for the production of 2269,, the first possibility noted above is not consistent with increased concentrations of 226 Ra in the sediment. The third case above is no different than the primary fractionation of radionuclides first described by Freiling (1962) except that naturally occurring, rather than bomb produced, radionuclides are involved. Station B~2 Sediment Core The distribution of 210p, (21954) and 226 Ra concentrations measured in the Station B-2 sediment core are shown in Figure 24. The concentrations of 2105, in the surface sediment of the core is about four times higher than that which can be supported in situ by 2264 decay, again indicating an external source for the 210 Pb measured. The 2195, concentrations in the upper 12 cm of the core decrease at about the same rate as do the 24) a and 23942406, concen- trations. Although the rate of decrease in lower layers is not well defined, th e 21951, 7226p, ratio decreases to 1 at a depth somewhere in the 11 to 22 cm region of the core. Such concentration profiles for 210 Ph are typical of marine sediments accumulating 2105, from natural sources (Schell, 1974b). The concentrations of 226 Ra measured in the 2-4, 8-10 and 14-16 cm sections of