HR: 09:30h
AN: PP11A-07    [Abstracts]
TI: Radiogenic isotope signatures of sediment sources vs. water masses in Late Holocene sediments from Fram Strait
AU: * Maccali, J
EM: jmaccali@crpg.cnrs-nancy.fr
AF: CRPG, 15, Rue Notre-Dame-des-Pauvres, Vandoeuvre-lès-Nancy, 54501, France
AU: * Maccali, J
EM: jmaccali@crpg.cnrs-nancy.fr
AF: GEOTOP-UQAM-McGILL, GEOTOP Université du Québec à Montréal C.P. 8888, Succ. Centre-Ville, Montreal, Qc H3C 3P8, Canada
AU: Carignan, J
EM: carignan@crpg.cnrs-nancy.fr
AF: CRPG, 15, Rue Notre-Dame-des-Pauvres, Vandoeuvre-lès-Nancy, 54501, France
AU: Reisberg, L
EM: reisberg@crpg.cnrs-nancy.fr
AF: CRPG, 15, Rue Notre-Dame-des-Pauvres, Vandoeuvre-lès-Nancy, 54501, France
AU: Hillaire-Marcel, C
EM: chm@uqam.ca
AF: GEOTOP-UQAM-McGILL, GEOTOP Université du Québec à Montréal C.P. 8888, Succ. Centre-Ville, Montreal, Qc H3C 3P8, Canada
AB: Exchanges of water-masses between the Arctic and the North Atlantic Ocean occur through Fram Strait and the Barents Sea. Here, we investigate geochemical signatures in the Fram Strait area based on radiogenic isotope measurements of i) surface sediments recovered along an E-W transect, and ii) two late Holocene sequences recording sediments supplied by the incoming North Atlantic waters (multicore MC-04) and the outflowing Arctic waters (MC-16), respectively located in the east and west of the Strait. Sediments <100μm were leached in order to separate their "authigenic" fractions, which carry a water-mass signature scavenged mostly by Fe-Mn oxyhydroxides, from the "inherited" detrital fractions that reflect sediment sources. Authigenic leachates and initial bulk sediments were analysed for their major and trace element concentrations as well as for their Pb and Nd isotopic compositions. The mass budget of the leaching procedure is approximately balanced, both in content and isotopic composition, within ±15% uncertainty (2σ). The fraction of each element removed by leaching varies between elements. Particle-reactive elements such as Pb, Nd and Th display relatively similar behaviour (although Pb is 3 times more easily leached than Nd and Th), in comparison with that of Fe and Mn. Isotopic compositions of surface sediments show three clusters representative of, respectively, the western, central and eastern Fram Strait areas. In the east, MC-04 displays nearly constant detrital isotopic compositions during the last 2.5 ka, not unlike those reported in the Yermak Plateau by Tutken et al. (2002). These isotopic compositions suggest variable mixing between two major end-members, the Atlantic Crust (Abouchami et al. 1999) and the European PanAfrican Crust (Fagel et al. 2004). Pb isotopes in the western core, MC-16, as well as in surface sediments from the central area of the Strait, suggest mixing between an Arctic source (cf. Alpha-Ridge; Winter et al. 1997) and the North Atlantic component, suggesting either some water-mass mixing in the central Fram Strait, and/or the superimposition of an Arctic imprint provided by the gyre of the North Atlantic Water mass in this basin.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1040 Radiogenic isotope geochemistry
DE: 1065 Major and trace element geochemistry
DE: 4825 Geochemistry
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2009 Joint Assembly