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Sedimentary processes in the Thau Lagoon (France): From seasonal to century time scales

Schmidt, Sabine and Jouanneau, Jean-Marie and Weber, Olivier and Lecroart, Pascal and Radakovitch, Olivier and Gilbert, Franck and Jézéquel, Didier Sedimentary processes in the Thau Lagoon (France): From seasonal to century time scales. (2007) Estuarine, Coastal and Shelf Science, vol. 72 (n° 3). pp. 534-542. ISSN 0272-7714

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Official URL: http://dx.doi.org/10.1016/j.ecss.2006.11.019

Abstract

As a part of the MICROBENT programme, an investigation of the sedimentation framework was carried out at the water-sediment interface in the Thau Lagoon (French Mediterranean coast). Two main sites, C4 in the middle of the lagoon and C5 near oyster farms, were visited six times between December 2001 and May 2003. Interface sediments were studied using classical sedimentology parameters (radiography RX, grain size distribution) and analysis of selected radionuclides (234Th, 7Be, 210Pb, 226Ra). On a century time scale, excess 210Pb (210Pbxs) presents classical profiles with an upper mixed layer, followed by an exponential decrease of activities to undetectable levels below 20 – 30 cm. At the central site, C4, cores seem to register episodic changes in mean grain size, presenting recurrently peaks. The upper 10 cm of 210Pbxs profiles at site C5 exhibit a mixed layer associated with coarser sediments: this could be related to biological activity. Sedimentation rates derived from 210Pbxs varied from 0.15 cm y−1 at the edge of the basin, to 0.25 cm y−1 at the central site. On a seasonal time scale, 234Th and 7Be both show significant variations in activities and in penetration within the sediment. Bioturbation rates derived from both radionuclides agree well and range between 1–10 cm2 y−1 at site C4 and 1–31 cm2 y−1 at site C5. 234Th and 7Be fluxes at the water-sediment interface show too seasonal variations, more pronounced for site C5. This latter site presents especially a higher variability that is well marked with season, probably in relation with its position near oyster farms.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com/science/article/pii/S0272771406005385
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Other partners > Institut de Physique du Globe de Paris - IPGP (FRANCE)
French research institutions > Institut de Recherche pour le Développement - IRD
Other partners > Université de Paris Diderot - Paris 7 (FRANCE)
Other partners > Université de Bordeaux 1 (FRANCE)
Other partners > Université de Provence - Aix-Marseille I (FRANCE)
Other partners > Ecole Pratique des Hautes Etudes - EPHE (FRANCE)
Other partners > Université de la Méditerranée - Aix-Marseille II (FRANCE)
Other partners > Université Paul Cézanne - Aix-Marseille III (FRANCE)
Other partners > Université Montesquieu - Bordeaux 4 (FRANCE)
Laboratory name:
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Deposited By:Franck Gilbert

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