|
|
|
| Registros recuperados: 29 | |
|
|
| 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... |
| Tipo: Text |
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 |
| |
|
|
| Sadekov, Aleksey; Eggins, Stephen M.; De Deckker, Patrick; Ninnemann, Ulysses; Kuhnt, Wolfgang; Bassinot, Franck. |
| Laser-ablation inductively coupled plasma-mass spectrometry microanalyses of Mg/Ca across individual final chambers of three planktonic foraminifera species, Globigerinoides ruber, G. sacculifer, and Pulleniatina obliquiloculata, reveal significant interspecies differences in test Mg concentrations. Whereas these three species have similar Mg/Ca values at low sea surface temperatures (similar to 22 degrees C), they diverge markedly at high sea surface temperatures (similar to 29 degrees C). Explanations for these differences in species Mg/Ca values based on detailed comparison of species intratest Mg/Ca distributions suggest that compositional variability within tests cannot account for the observed deviation of species Mg/Ca values in warm-water... |
| Tipo: Text |
|
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00218/32934/31448.pdf |
| |
|
|
| 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 |
| |
|
|
| Ma, Ruifang; Sépulcre, Sophie; Licari, Laetitia; Haurine, Frédéric; Bassinot, Franck; Yu, Zhaojie; Colin, Christophe. |
| We have measured Cd / Ca ratios of several benthic foraminiferal species and studied benthic foraminiferal assemblages on two cores from the northern Indian Ocean (Arabian Sea and northern Bay of Bengal, BoB), in order to reconstruct variations in intermediate water circulation and paleo-nutrient content since the last deglaciation. Intermediate water Cdw records estimated from the benthic Cd / Ca reflect past changes in surface productivity and/or intermediate-bottom water ventilation. The benthic foraminiferal assemblages are consistent with the geochemical data. These results suggest that during the last deglaciation, the Heinrich Stadial 1 and Younger Dryas (HS1 and YD, respectively) millennial-scale events were marked by a decrease in Cdw values,... |
| Tipo: Text |
|
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00659/77152/78525.pdf |
| |
|
|
| Ujiie, Yurika; Asahi, Hirofumi; Sagawa, Takuya; Bassinot, Franck. |
| The North Pacific Subtropical Gyre (NPSG) has two important functions, i.e., one in ocean heat transfer and another as a driving force for circulation of the surface and intermediate waters on the basin scale. In the present study, we describe records of the vertical thermal structures and distributions of water masses in the upper ocean of the subtropical northwest (NW) Pacific for the past 190 kyr, using two sediment cores collected from the Kuroshio Current area in the East China Sea and the NPSG area. During the two glacial periods, the Kuroshio Current was weakened owing to changes in ocean-atmosphere circulation and eustasy. The differences in the Mg/Ca-derived temperatures between surface and thermocline waters show the changes of depth and... |
| Tipo: Text |
Palavras-chave: North Pacific Subtropical Gyre; LGM; MIS 6; Paleotemperature; Water-column structure. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00358/46911/46812.pdf |
| |
|
|
| 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 |
| |
|
|
| Boussetta, Soumaya; Kallel, Nejib; Bassinot, Franck; Labeyrie, Laurent; Duplessy, Jean-claude; Caillon, Nicolas; Dewilde, Fabien; Rebaubier, Helene. |
| We generated a high-resolution SSTMg/Ca record for the surface-dwelling planktonic foraminifera Globigerina bulloides from the core MD99-2346 collected in the Gulf of Lion, and compared it to that obtained using modern analogue techniques applied to fossil foraminiferal assemblages (SSTMAT). The two temperature records display similar patterns during the last 28,000 years but the SSTMg/Ca estimates are several degrees warmer (similar to+4 degrees C) than SSTMAT. The temperature shift between SSTMg/Ca and SSTMAT remained relatively constant over time. This seems to exclude a bias on the Mg/Ca record associated with salinity or secondary Mg-rich calcite encrustation on the foraminiferal tests during early diagenesis. Therefore, anomalously high Mg/Ca... |
| Tipo: Text |
Palavras-chave: Mediterranean; Mg/Ca; Planktonic foraminifera; Sea surface Temperature; Salinity; Diagenesis; Vital effect. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00139/25047/23181.pdf |
| |
|
|
| Moreno, Eva; Bassinot, Franck; Baudin, Francois; Venec-peyre, Marie-therese. |
| [1] A multiproxy study of core MD98-2166 makes it possible to investigate the influence of orbital forcing and sea level changes on Timor Sea sedimentation during the last 260 ka. Spectral analysis reveals a strong imprint of obliquity in all proxies. This is particularly puzzling for the CaCO(3) and total organic carbon (TOC) records since recent data obtained on nearby core MD01-2378, collected at a shallower water depth, showed a concentration of spectral power in the eccentricity and precession bands. Our results suggest that while sedimentary record in shallower core MD01-2378 shows a clear low-latitude response, that of core MD98-2166 reflects a stronger influence of high-latitude forcing through deepwater changes. In addition, Rock-Eval analyses... |
| Tipo: Text |
|
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00238/34885/33152.pdf |
| |
|
|
| Nouet, Julius; Bassinot, Franck. |
| Several authors suggested that the thinning, with increasing depth of deposition, of calcite X-ray diffractometry (XRD) peaks obtained on planktonic foraminifera tests resulted from the preferential removal of their poorly crystallized parts as dissolution increases. By deconvolving XRD peak (104) from Globorotalia tumida (surface sediments, Sierra Leone Rise depth transect), we show that the full width at midheight does not depend only upon crystallinity, but reflects also the chemical and structural heterogeneity of foraminifera tests, which results in closely spaced, individual (104) diffraction peaks corresponding to phases with slightly different Mg contents. G. tumida contains two calcite phases: a well crystallized, Mg-poor calcite and a poorly... |
| Tipo: Text |
Palavras-chave: Dissolution; Foraminifera; X-ray diffraction; Crystallinity; Deconvolution. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00235/34626/32973.pdf |
| |
| Registros recuperados: 29 | |
|
|
|
