Uranium in pore waters of two southern ocean cores
References Anderson, J . B. 1 972. Nearshoi'e glacial-marine deposition from modern sediments ofthe \Veddell Sea. Nature, 240: 189-192. Anderson, J . B. Inpress a. Distribution and ecology of braminif'era from the Weddell Sea, Antarctica. Micropaleontology. Anderson, J . B. In press h. Factors controlling CaCO3 dissO lution in the Weddell Sea from boramiiiiberal distribution patterns. Marine Geology. Berger, W. H. 1970. Biogenous deep-sea sediments: fractionation by deep-sea circulation. Bulletin of the Geological Society of America, 81: 1385-1402. Carey, S. W., and N. Ahmad. 1961. Glacial marine sedimentation. First International Symposium on Arctic Geology. Proceedings, 2: 865-894. Kennett, J . P. 1966. F'oratniiiileral evidence of a shallow calcium carbonate solution boundar y , Ross Sea, Antarctica. Science, 153: 191-193. Kennett, J . P. 1968. Ecolog y and distribution of foraminifera. The fauna of the Ross Sea, part 6. Bulletin of the N.Z. Department of Scientific and Industrial Research, 186: 1-48. Li, Y. H., T. Takahashi, and W. S. Broecker. 1969. Degree of saturation of CaCO 3 in the oceans. Journal of Geophysical Research, 74: 5507-5527.
.70
E49-28 -. E50-/-
I.60 -All errors are counting errors.
CD ('5
(1.0±0,1)
50 2.005Y
('5
1.400
i T
±0.2)
8±0.3)
±2.6)
.30 >> 1,20-±0.2) F0 1.101-
(11.9±0.7)
-'i'
k
LI5-C.1..)
(5.0±0.2) I 1.00
0 200 400 600 800 1000 DEPTH IN CM
Graph showing relationship between uranium-234/uranium238 activity ratio and depth in centimeters of pore water in two Eltanin piston cores. Concentrations of uranium in parts per billion are also shown parenthetically.
Uranium in pore waters of two southern ocean cores and J . K. OSMOND Antarchic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306
J . F. DYSART
A new method of extracting pore water from deep sea cores using silica gel as a dehydrating agent has been applied to two USNS Eltanin piston cores from the southern ocean. The pore water obtained, averaging 60 percent of the total sediment weight, has been analyzed from uranium isotopes to test the uraniurn-234 diffusion hypotheses of Ku (1965). Uranium concentrations in pore water from core E50-1, a pelagic mud (F'rakes, 1973), are greater (11.9 to 21.6 parts per billion) than those from core E49-28, a siliceous ooze (1.0 to 6.8 parts per billion). Uranium-234/uranium-238 activity ratios for both of these cores average about 1 .3, but the variation is greater for the siliceous ooze (1.04 to 1.58). Activity ratios for both cores appear to diminish from near the core top to about 500 centimeters, but then the ratio climbs to much higher September/October 1975
values in the siliceous ooze while continuing to decrease in the pelagic mud (figure). A simple diffusion model is apparently not supported by these data since a value near the activity ratio of 1. 15 for seawater would be expected near the core top with slightly increasing values at depth. Conversely, the high activity ratios measured by Immel (1974) in micromanganese nodules, and hypothesized by him to be characteristic of immobile uranium in pore water, are not observed. More analyses of uranium in solids and leachates from these two cores, as well as related studies of other Eltanin cores, are in progress. This research was partially supported by National Science Foundation grant (;V-25786. References Frakes, L. A. 1973. USNS Eltanin sediment descriptions, cruises 4-54. Tallahassee, Florida State University, Scdimentology Research laborator y , Department of Geology. Contribution, 37. 259p. Immel, R. L. 1974. Origin of micromanganese nodules deuranium-234/uraniuni-238 ratios. Antarctic termined Journal qj the U.S., IX(5): 259-260. Ku, T. L. 1965. An evaluation of the uranium-234/uranium-238 methods as a tool for dating pelagic sediments. Journal of Geophysical Research, 70: 3457-3474. 1m111
255
