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| Solignac, S; Giraudeau, J; De Vernal, A. |
| Holocene records of sea surface conditions in the western Nordic seas were obtained from quantitative reconstructions based on dinoflagellate cyst assemblages. Two sediment cores from the east Greenland and the north Iceland shelves provide a detailed account of the long- and short-term dynamics of the opposing flows of Arctic versus Atlantic waters. Both marker species and quantitative reconstructions depict an overall trend toward warmer winter temperatures, saltier surface waters, and decreased sea ice extent. The latter is supported by a close relationship between relative abundances of an Atlantic dinocyst species, Nematosphaeropsis labyrinthus, and ice-rafted debris (IRD) records. We propose that the late Holocene increased IRD delivery in the... |
| Tipo: Text |
Palavras-chave: Holocene; North Atlantic; Sea-surface conditions. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00234/34573/33124.pdf |
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| Pujos, A; Giraudeau, J. |
| Calcareous nannofossil assemblages of the family Noelaerhabdaceae have been studied in sediments of seventeen Quaternary cores raised from various climatic areas of the Atlantic and Pacific oceans. These sections display a regular, hiatus-free sedimentation for the last 500000 years. They have been dated using oxygen-isotopic measurements, variations of calcium carbonate content, variations of total nannofossil abundance, thorium measurements and volcanic ash horizons. Coccoliths of the genus Gephyrocapsa have been placed in three distinct taxonomic groups, based on morphological criteria inferred from light-microscope observations. Their acmes, as well as the acme of Emiliania huxleyi, are considered as stratigraphic markers. These markers characterize... |
| Tipo: Text |
Palavras-chave: NOELAERHABDACEAE; CALCAREOUS NANNOFOSSILS; STRATIGRAPHICAL MARKERS; UPPER/MIDDLE QUATERNARY. |
| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00099/21061/18687.pdf |
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| Pichevin, L; Martinez, P; Bertrand, P; Schneider, R; Giraudeau, J; Emeis, K. |
| In the light of new surface sediment delta(15)N data collected over the Namibian shelf and slope, we examined glacial-interglacial variations of N inventory in the area of Luderitz (25 degrees 6S) by deciphering delta(15)N signals of three cores distributed from the upper to the lower continental slope. The lower slope cores display low delta(15)N during cold periods and high delta(15)N during climatic optima, akin to many other records from the world ocean, whereas the upper slope core displays a high-frequency low-amplitude delta(15)N signal without obvious glacial-interglacial variability. This dissimilarity results from the segregation of the upwelling structure in two cells, decoupling nutrient dynamics of the shelf from those beyond the shelf-edge.... |
| Tipo: Text |
Palavras-chave: Nitrogen cycling; Benguela; Climatic cycles. |
| Ano: 2005 |
URL: https://archimer.ifremer.fr/doc/00232/34366/32796.pdf |
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