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| Simon, Quentin; Thouveny, Nicolas; Bourles, Didier L.; Valet, Jean-pierre; Bassinot, Franck; Menabreaz, Lucie; Guillou, Valery; Choy, Sandrine; Beaufort, Luc. |
| Geomagnetic dipole moment variations associated with polarity reversals and excursions are expressed by large changes of the cosmogenic nuclide beryllium-10 (10Be) production rates. Authigenic 10Be/9Be ratios (proxy of atmospheric 10Be production) from oceanic cores therefore complete the classical information derived from relative paleointensity (RPI) records. This study presents new authigenic 10Be/9Be ratio results obtained from cores MD05-2920 and MD05-2930 collected in the west equatorial Pacific Ocean. Be ratios from cores MD05-2920, MD05-2930 and MD90-0961 have been stacked and averaged. Variations of the authigenic 10Be/9Be ratio are analyzed and compared with the geomagnetic dipole low series reported from global RPI stacks. The largest 10Be... |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00358/46910/46811.pdf |
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| Simon, Quentin; Thouveny, Nicolas; Bourles, Didier L.; Bassinot, Franck; Savranskaia, Tatiana; Valet, Jean-pierre. |
| New high-resolution authigenic 10Be/9Be ratio (Be-ratio) records covering the last geomagnetic reversal, i.e. the Matuyama–Brunhes transition (MBT), have been obtained and set on a time scale using benthic δ18 O (Cibicides wuellerstorfi) records. The geographic distribution of the four studied sites allows global comparison between the North Atlantic, Indian and Pacific Oceans. All Be-ratio records contain a two-fold increase triggered by the geomagnetic dipole moment (GDM) collapse associated with the MBT. The stratigraphic position of the Be-ratio spike, relative to marine isotope stages, allows establishment of a robust astrochronological framework for the MBT, anchoring its age between 778 and 766 ka (average mid-peaks at 772 ka), which is consistent... |
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Palavras-chave: Authigenic Be-10/Be-9 ratio; Geomagnetic dipole moment minimum; Matuyama-Brunhes transition (MBT); Geomagnetic polarity reversal; Marine isotope stage 19; Atmospheric Be-10 production rates. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00430/54150/55510.pdf |
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| 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... |
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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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| Simon, Quentin; Bourles, Didier L.; Bassinot, Franck; Nomade, Sebastien; Marino, Maria; Ciaranfi, Neri; Girone, Angela; Maiorano, Patrizia; Thouveny, Nicolas; Choy, Sandrine; Dewilde, Fabien; Scao, Vincent; Isguder, Gulay; Blamart, Dominique; Aster Team,. |
| Geomagnetic dipole moment (GDM) lows associated with polarity reversals or geomagnetic excursions induce significant modulation of the cosmogenic nuclide Beryllium-10 (Be-10) production. Hence, the reconstruction of atmospheric Be-10 production rates from natural archives such as marine sedimentary sequences or ice cores constitutes a complementary approach, independent from paleomagnetic measurements, to decipher past GDM fluctuations. This is particularly important in the Montalbano Jonico succession (South Italy) since it is candidate to host the Global Stratotype Section and Point of the Middle Pleistocene Stage but where the magnetostratigraphic positioning of the Matuyama-Brunhes boundary (MBB) has not been available up to now. This study presents... |
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Palavras-chave: Be-10 cosmogenic nuclide; Authigenic Be-10/Be-9 ratio; Matuyama Brunhes Boundary (MBB); High-resolution oxygen isotope stratigraphy; MIS 19; GSSP stratotype. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00420/53183/55042.pdf |
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| Simon, Quentin; Bourles, Didier L.; Thouveny, Nicolas; Horng, Chorng-shern; Valet, Jean-pierre; Bassinot, Franck; Choy, Sandrine. |
| Long-term variations of the geomagnetic dipole moment (GDM) during periods of stable polarity and in transitional states (reversals and excursions) provide key information for understanding the geodynamo regime. Following several studies dealing with the Brunhes chron and the Matuyama–Brunhes transition, this study presents a new authigenic 10Be/9Be ratio (Be-ratio) record obtained from the MD97-2143 core (western Pacific Ocean). This new Be-ratio series yields a record of GDM variations covering the early Brunhes and mid to late Matuyama time period (i.e. 700–2140ka), independently from the relative paleointensity (RPI) record obtained from the same core, that can be compared with available RPI records and stacks. Stratigraphic offsets measured between... |
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Palavras-chave: Authigenic Be-10/Be-9 ratios; Matuyama-Brunhes transition; Jaramillo and Olduvai subchrons; Cobb Mountain and Reunion events; Matuyama geomagnetic excursions; Lock-in depth. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00414/52553/53381.pdf |
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