Fine scale distributions of porosity and particulate excess210Pb,organic carbon and CaCO3 in surface sediments of the deep equatorial Pacific |
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| Institution: | 1. Scripps Institution of Oceanography, A-020, University of California at San Diego, La Jolla, CA 92093 U.S.A.;2. School of Oceanography, WB-10, University of Washington, Seattle, WA 98195 U.S.A.;3. Marine Sciences Research Center, State University of New York at Stony Brook, Stony Brook, NY 11794 U.S.A.;1. V.I. Il''ichev Pacific Oceanological Institute FEB RAS, 43 Baltiyskaya St., Vladivostok, 690041, Russia;2. GEOMAR Helmholtz Centre for Ocean Research, Wischhofstrasse, 3, Kiel, Germany;3. V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, Moscow, Russia;4. Far East Geological Institute FEB RAS, Pr. 100 let Vladivostok, 159, Vladivostok, 690022, Russia;5. NEISRI FEB RAS, North-East Interdisciplinary Science Research Institute FEB RAS, Portovaya St., 16, 685000, Magadan, Russia;6. First Institute of Oceanography, SOA, Xian-Xia-Ling Road, 6, Qingdao, 266061, China;1. University of Ghana, Ghana;2. Moss Landing Marine Laboratories, CA, United States |
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| Abstract: | Sediment samples were recovered from the central equatorial Pacific Ocean, sectioned at 1-mm intervals, and analyzed for porosity, organic carbon, excess210Pb and CaCO3. Steep porosity gradients were measured in the upper 1 cm of the sediment column with extremely high values observed near the sediment surface. Similarly, particulate organic carbon contents are highest at the sediment surface, decrease sharply in the upper 1 cm, and are relatively constant between 1 and 5 cm. CaCO3 values, on the other hand, are lowest at the sediment surface and increase to a constant value below 5–10 mm depth. At the carbonate ooze sites, excess210Pb is present throughout the upper 5 cm of the sediments suggesting relatively rapid particle mixing rates. However, extremely high excess210Pb activities (> 100 dpm/g) are observed at the sediment surface with sharp gradients present in the upper 1 cm which would suggest slow rates of mixing. This apparent contradiction along with the major features of the CaCO3 and particulate organic carbon profiles can be explained by a particle-selective feeding mechanism in which organic carbon, excess210Pb-enriched particles are preferentially maintained at the sediment surface via ingestion and defecation by benthic organisms. |
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