Fluxes of uranium and thorium series isotopes in the Santa Barbara Basin |
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| Authors: | Willard S Moore Kenneth W Bruland Jacqueline Michel |
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| Institution: | 1. Geology Department, University of South Carolina, Columbia, SC 29208U.S.A.;2. Marine Studies, Division of Natural Sciences, University of California, Santa Cruz, CA 95064U.S.A. |
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| Abstract: | Samples from the MANOP Santa Barbara Basin sediment trap intercomparison were analyzed for the isotopes of uranium, thorium, radium, lead, and polonium. All of the traps showed approximately the same compositions and isotopic ratios, indicating that they trapped similar materials. The234Th flux via falling particles was very close to the flux predicted from the production and scavenging rates of234Th from the water column. The210Pb content of the trapped particles and the surface sediments were the same, however, the measured flux of210Pb was seven times greater than the predicted flux. Predicted and measured fluxes of228Th and210Po were similarly out of balance. To explain this apparent inconsistency, we suggest (as others have done) that the Santa Barbara Basin is an area where scavenging from the water column is intensified and where sediments deposited initially on the margins may be physically remobilized on a short time scale. These two effects increase the apparent area from which the basin derives the longer-lived isotopes but does not increase significantly the supply of the short-lived234Th. |
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