Diagenetic modulation of the magnetic properties in sediments from the Northern Indian Ocean
| Type | Article | ||||||||||||
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| Date | 2013-09 | ||||||||||||
| Language | English | ||||||||||||
| Author(s) | Bouilloux Alexandra1, Valet Jean-Pierre1, Bassinot Franck2, Joron Jean-Louis1, 3, Blanc-Valleron Marie-Madeleine4, Moreno Eva4, Dewilde Fabien2, Kars Myriam5, Lagroix France1 | ||||||||||||
| Affiliation(s) | 1 : Univ Paris Diderot, Inst Phys Globe Paris, Sorbonne Paris Cite, UMR CNRS 7154, FR-75238 Paris 05, France. 2 : Lab Sci Climat & Environm CEA CNRS UVSQ, Domaine CNRS, Gif Sur Yvette, France. 3 : CEA Saclay, Lab Pierre Sue, F-91191 Gif Sur Yvette, France. 4 : Museum Natl Hist Nat, UMR CNRS 7207, F-75231 Paris, France. 5 : Univ Montpellier 2, Geosci Montpellier UMR 5243, Montpellier, France. |
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| Source | Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2013-09 , Vol. 14 , N. 9 , P. 3779-3800 | ||||||||||||
| DOI | 10.1002/ggge.20234 | ||||||||||||
| WOS© Times Cited | 11 | ||||||||||||
| Keyword(s) | paleomagnetism, paleoenvironment, goethite, magnetite, Indian ocean | ||||||||||||
| Abstract | Large changes in magnetic mineral concentration dependent parameters by more than 1 order of magnitude occur over 50-150 cm intervals in two marine sediment cores from the oxygen minimum zone in the Gulf of Aden. High-resolution sedimentological and chemical analyses indicate that these intervals are not associated with turbiditic events or sediment reworking, they do not result from changes in carbonate dilution or differences in sediment properties, and they do not correspond to volcanic layers. Magnetic mineralogical analyses reveal a change in magnetic mineral concentration from a magnetite-goethite assemblage to pure magnetite within the peak. The peaks almost disappear when the abundance of magnetic minerals is calculated after correcting for the magnetic moments of each magnetic mineral. Therefore, under the assumption that the variability of the magnetic parameters results from postdepositional mineralogical transformations, a relatively constant amount of magnetite was present at the surface of the sediment. Changes in redox conditions and nonsteady state diagenesis transformations have effectively been observed along both cores. Large values of total organic carbon coincide with poor preservation of biogenic and detrital magnetite, which reflects reductive dissolution of the finer magnetite grains. At the same levels, Fe2+ release from reductively dissolved magnetite favored precipitation of goethite. The susceptibility peaks coincide with episodes of magnetite preservation caused by reduced surface productivity and/or enhanced bottom-water ventilation accompanying northward extension of Glacial Antarctic Intermediate Water into the Indian Ocean. | ||||||||||||
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