HR: 0830h
AN: PP11A-0197    [PDF]
TI: Microanalysis of O-C-B Stable Isotopes in Deep Sea Corals by SIMS
AU: * Blamart, D
EM: dominique.blamart@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS, Domaine du CNRS, Bat 12, 4, Avenue de la Terrasse, Gif sur Yvette, 91198 France
AU: Rollion-Bard, C
EM:
AF: CRPG-CNRS, BP 20, 15, rue Notre-Dame des Pauvres, Vandoeuvre les Nancy, 54500 France
AU: Juillet-Leclerc, A
EM:
AF: Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS, Domaine du CNRS, Bat 12, 4, Avenue de la Terrasse, Gif sur Yvette, 91198 France
AU: Cuif, J
EM:
AF: Universit‚ de Paris XI, Facult‚ des Sciences,, Bat 504 G‚ologie, ORSAY, 91405 France
AB: We measured the O-C and B isotope composition of deep sea coral (DSC) ({\it Lophelia pertusa}) at a micrometre scale by ion microprobe (SIMS - Secondary Ion Mass Spectrometry). Coral skeletons are composed of two different microstructures: (1) centres of calcification and (2) surrounding fibers. In ({\it Lophelia pertusa}) centres of calcification are arranged in lines of centres of calcification (LCC), large enough (50 microns) to be measured using the SIMS technique. Our results show clear patterns between the LCC and the surrounding fibres. LCC have a restricted range of variation in $\delta^{18}$O (-2.8 $\pm$ 0.3$\permil$ (PDB)), a larger range in $\delta^{13}$C (-14.3 to -10.9$\permil$ (PDB)) and $\delta^{11}$B (24.8 to 35.8$\permil$) with most of the values at 30$\permil$ (NBS951). The $\delta^{11}$B variation corresponds to a pH variation of 1 unit from 8.4 to 9.4. Surrounding skeletal fibres exhibit large isotopic variation both for O and C and (up to 12$\permil$), and B (up to 17$\permil$). $\delta^{13}$C and $\delta^{18}$O are positively correlated. At the lightest $\delta^{18}$O values of the surrounding fibers, the C and O isotopic composition of the centres of calcification deviate from this linear trend. The variation of $\delta^{18}$O at a micrometre scale is probably the result of two processes: (1) an isotopic equilibrium calcification with at least 1 pH unit variation in the calcification fluid at the site of LCC and (2) a kinetic fractionation. The d13C apparent disequilibrium in {\it Lophelia pertusa} may be the result of mixing between depleted d13C metabolic CO$_{2}$ (respiration) and DIC coming directly from seawater.
DE: 1040 Isotopic composition/chemistry
DE: 4267 Paleoceanography
DE: 4835 Inorganic marine chemistry
DE: 4850 Organic marine chemistry
DE: 4870 Stable isotopes
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting