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Disentangling magnetic and environmental signatures of sedimentary 10Be/9Be records ArchiMer
Savranskaia, Tatiana; Egli, Ramon; Valet, Jean-pierre; Bassinot, Franck; Meynadier, Laure; Bourlès, Didier L.; Simon, Quentin; Thouveny, Nicolas.
Reconstructions of the global production rate of the cosmogenic isotope 10Be from sedimentary records of authigenic 10Be/9Be ratios have been successfully used to obtain independent estimates of geomagnetic dipole moment variations caused by field excursions or reversals. In this study, we assess the reliability of 10Be/9Be as a proxy for the cosmogenic 10Be production rate by evaluating two potential biasing sources represented by sediment composition and climatic modulation. For this purpose, we compare five high-resolution 10Be/9Be records of the Matuyama-Brunhes (M-B) field reversal from sediment cores of the Indian, West Pacific, and North Atlantic oceans. Significant increase of 10Be/9Be ratios at 774 ka is explained in terms of the dominant control...
Tipo: Text Palavras-chave: Cosmogenic nuclides; Beryllium; Authigenic; 10Be/9Be ratio; Geomagnetic field intensity; Matuyama-brunhes reversal.
Ano: 2021 URL: https://archimer.ifremer.fr/doc/00682/79399/81939.pdf
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Link between Indian monsoon rainfall and physical erosion in the Himalayan system during the Holocene ArchiMer
Joussain, Ronan; Liu, Zhifei; Colin, Christophe; Duchamp-alphonse, Stephanie; Yu, Zhaojie; Moreno, Eva; Fournier, Lea; Zaragosi, Sebastien; Dapoigny, Arnaud; Meynadier, Laure; Bassinot, Franck.
Mineralogical and geochemical analyses conducted on cores located on the active channel-levee system of the northern Bengal Fan are used to establish changes in the weathering pattern and the sediment transport of the Himalayan system, and evaluate the effect of Indian summer monsoon rainfall during the Holocene. Our data indicate that during the Holocene, sediments from the northern Bengal Fan originate mainly from the G-B river system without any significant changes in the relative contribution of these rivers. From 9.8 to around 6 ka, relatively low smectite/(illite+chlorite) ratios and relatively high K/Si* ratios indicate high physical denudation rates of the Himalayan highlands together with a rapid transfer of the detrital material to the Bengal...
Tipo: Text Palavras-chave: Bengal Fan; Chemical weathering; Sr and Nd isotopic compositions; Physical erosion; Clay mineralogy.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00393/50416/51143.pdf
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The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data ArchiMer
Tachikawa, Kazuyo; Arsouze, Thomas; Bayon, Germain; Bory, Aloys; Colin, Christophe; Dutay, Jean-claude; Frank, Norbert; Giraud, Xavier; Gourlan, Alexandra T.; Jeandel, Catherine; Lacan, Francois; Meynadier, Laure; Montagna, Paolo; Piotrowski, Alexander M.; Plancherel, Yves; Puceat, Emmanuelle; Roy-barman, Matthieu; Waelbroeck, Claire.
Neodymium isotopic compositions (143Nd/144Nd or εNd) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have updated a global seawater εNd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive εNd data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (< 10,000 years). At water depths ≥ 1500 m, property-property plots show clear correlations between seawater εNd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater εNd...
Tipo: Text Palavras-chave: Nd isotopes; Water mass tracer; Data compilation; Predicted seawater epsilon(Nd); Seawater-archive comparison.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00376/48768/49165.pdf
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When and why sediments fail to record the geomagnetic field during polarity reversals ArchiMer
Valet, Jean-pierre; Meynadier, Laure; Simon, Quentin; Thouveny, Nicolas.
We present four new records of the Matuyama–Brunhes (M–B) reversal from sediments of the Equatorial Indian Ocean, West Equatorial Pacific and North Atlantic Oceans with deposition rates between 2 cm/kyr and 4.5 cm/kyr. The magnetic measurements were performed using 8 cc cubic samples and provided well-defined reverse and normal polarity directions prior and after the last reversal. In three records stepwise demagnetization of the transitional samples revealed a succession of scattered directions instead of a well-defined characteristic component of magnetization. There is no relationship with changes in magnetic mineralogy, magnetic concentration and magnetic grain sizes. This behavior could be caused by weakly magnetized sediment. However the transitional...
Tipo: Text Palavras-chave: Geomagnetic reversals; Magnetization acquisition; Rock magnetism; Sediment; Demagnetization.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00347/45868/45561.pdf
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Yttrium and rare earth element partitioning in seawaters from the Bay of Bengal ArchiMer
Yu, Zhaojie; Colin, Christophe; Douville, Eric; Meynadier, Laure; Duchamp-alphonse, Stephanie; Sepulcre, Sophie; Wan, Shiming; Song, Lina; Wu, Qiong; Xu, Zhaokai; Bassinot, Frank.
The dissolved Yttrium (Y) and Rare Earth Element (REE) concentrations of seawater samples collected along a north-south hydrological transect within the Bay of Bengal (BoB) have been analyzed to estimate contributions of the Ganges and Brahmaputra (G-B) river inputs to the dissolved REE distribution of the Northern Indian Ocean. Surface water masses of the BoB are characterized by Y/Ho ratios (84) intermediate between the G-B river suspended sediment (41) and water mass from the South Indian Ocean (93). Co-variation of MREE (Middle REE, Sm) and LREE (Light REE, La) concentrations suggests that the dissolved REEs in surface waters (upper 100 m depth) of the BoB (Sm/La = 0.21) appear to derive mainly from the freshwater discharge of the G-B river system. In...
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Ano: 2017 URL: https://archimer.ifremer.fr/doc/00377/48845/49277.pdf
Registros recuperados: 5
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