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Registros recuperados: 9
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Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition ArchiMer
Tachikawa, K.; Vidal, L.; Cornuault, M.; Garcia, M.; Pothin, A.; Sonzogni, C.; Bard, E.; Menot, G.; Revel, M..
Holocene eastern Mediterranean Sea sediments contain an organic-rich sapropel S1 layer that was formed in oxygen-depleted waters. The spatial distribution of this layer revealed that during S1 deposition, deep waters were anoxic below a depth of 1800 m. However, whether this boundary permanently existed from the early to the mid-Holocene has not been examined yet. To answer this question, a multi-proxy approach was applied to a core retrieved close to the 1800 m boundary (at 1780 m). We measured the bulk sediment elemental composition, the stable isotopic composition of the planktonic foraminifer Globigerinoides ruber and the abundance of benthic foraminifera since the last deglaciation. The result indicates that authigenic U and Mo accumulation began...
Tipo: Text
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00291/40252/38634.pdf
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Formation and preservation of greigite (Fe3S4) in sediments from the Santa Barbara Basin: Implications for paleoenvironmental changes during the past 35 ka ArchiMer
Blanchet, C. L.; Thouveny, N.; Vidal, L..
Diagenetic processes are known to modify sedimentary records, but they can also reveal important paleoenvironmental changes. Here we investigate variations in sedimentary iron diagenesis and depositional environments for the last 35 ka by analyzing the rock magnetic and geochemical properties of two sediment cores collected in the Santa Barbara Basin (California). In organic-rich sediments, early diagenesis often leads to partial dissolution of detrital iron oxides and stepwise formation of authigenic pyrite (FeS2). The pyritization process takes place following several geochemical pathways, sometimes involving intermediate iron sulfide species such as greigite (Fe3S4). Sedimentary conditions in the basin appear to have recurrently favored preservation of...
Tipo: Text
Ano: 2009 URL: https://archimer.ifremer.fr/doc/00218/32936/31447.pdf
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Hydrological variability in the Northern Levant: a 250 ka multiproxy record from the Yammouneh (Lebanon) sedimentary sequence ArchiMer
Gasse, F.; Vidal, L.; Develle, A-l; Van Campo, E..
The Levant is a key region in terms of both long-term hydroclimate dynamics and human cultural evolution. Our understanding of the regional response to glacial-interglacial boundary conditions is limited by uncertainties in proxy-data interpretation and the lack of long-term records from different geographical settings. The present paper provides a 250 ka paleoenvironmental reconstruction based on a multi-proxy approach from northern Levant, derived from a 36 m lacustrine-palustrine sequence cored in the small intra-mountainous karstic Yammouneh basin from northern Lebanon. We combined time series of sediment properties, paleovegetation, and carbonate oxygen isotopes (delta(c)), to yield a comprehensive view of paleohydrologic-paleoclimatic fluctuations in...
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Ano: 2011 URL: https://archimer.ifremer.fr/doc/00228/33902/32216.pdf
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Hydrology in the Sea of Marmara during the last 23 ka: Implications for timing of Black Sea connections and sapropel deposition ArchiMer
Vidal, L.; Menot, G.; Joly, C.; Bruneton, H.; Rostek, F.; Cagatay, M. N.; Major, C.; Bard, E..
Sediments deposited under lacustrine and marine conditions in the Sea of Marmara hold a Late Quaternary record for water exchange between the Black Sea and the Mediterranean Sea. Here we report a multiproxy data set based on oxygen and strontium isotope results obtained from carbonate shells, major and trace elements, and specific organic biomarker measurements, as well as a micropaleontological study from a (14)C-dated sediment core retrieved from the Sea of Marmara. Pronounced changes occurred in delta(18)O and (87)Sr/(86)Sr values at the fresh and marine water transition, providing additional information in relation to micropaleontological data. Organic biomarker concentrations documented the marine origin of the sapropelic layer while changes in...
Tipo: Text
Ano: 2010 URL: https://archimer.ifremer.fr/doc/00231/34243/32642.pdf
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Influence of diagenesis on the stable isotopic composition of biogenic carbonates from the Gulf of Tehuantepec oxygen minimum zone ArchiMer
Blanchet, C. L.; Kasten, S.; Vidal, L.; Poulton, S. W.; Ganeshram, R.; Thouveny, N..
In order to evaluate the influence of diagenetic and post-sampling processes on the stable oxygen and carbon isotope compositions of biogenic carbonates, we conducted a multiproxy study of organic-rich sediments from the eastern Pacific oxygen minimum zone. Core MD02-2520, which was retrieved from the Gulf of Tehuantepec (Mexico), has seasonal laminations and covers the last 40 kyr. Together with the presence of gypsum crystals and inorganic calcite aggregates, the occurrence of large excursions in the stable oxygen and carbon isotope records of both planktonic and benthic foraminifera (as large as +3 parts per thousand in delta O-18 and -5 parts per thousand in delta C-13) point to significant secondary transformations. Storage-related gypsum...
Tipo: Text Palavras-chave: Diagenesis; Gypsum; Inorganic calcite; Laminations; Oxygen minimum zone; Sulfur reoxidation.
Ano: 2012 URL: https://archimer.ifremer.fr/doc/00139/25049/23173.pdf
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Le carbone 14 : progrès récents et limitations de la méthode de datation IRD
Duplessy, J.C.; Arnold, M.; Bard, E.; Cortijo, E.; Labeyrie, L.; Laj, C.; Lehman, B.; Mazaud, A.; Paterne, M.; Tisnerat, N.; Vidal, L..
La méthode de datation par le carbone 14 a permis l'établissement d'une échelle chronologique du Quaternaire Supérieur et a contribué à la découverte de phénomènes insoupçonnés comme l'existence de variations climatiques abruptes et de grande amplitude pendant la dernière période glaciaire et la déglaciation qui l'a terminée. L'effort continu pour comparer les âges carbone 14 avec les âges calendaires a été maintenant étendu au delà de 30 000 ans, même si le nombre de mesures est encore trop petit pour permettre l'établissement d'une courbe de calibration précise au delà des dix mille dernières années. La comparaison des variations du rapport 14C/12C de l'atmosphère avec celles du champ magnétique terrestre (déduites de l'analyse des carottes de sédiments...
Tipo: Text Palavras-chave: QUATERNAIRE; DATATION ABSOLUE; C 14; GEOCHRONOLOGIE; PALEOCLIMAT; CHAMP MAGNETIQUE.
Ano: 1998 URL: http://www.documentation.ird.fr/hor/fdi:010013863
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Les axes de l'utopie : organisation des transports à Brasilia IRD
Aubertin, Catherine; Vidal, L..
Tipo: Text Palavras-chave: TRANSPORT URBAIN; URBANISME; VILLE SATELLITE.
Ano: 1991 URL: http://www.documentation.ird.fr/hor/fdi:35124
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Lithostratigraphic Summary For Leg 175: Angola-Benguela Upwelling System OceanDocs
Anderson, L.; Maslin, M.A.; Jansen, F.; Lin, H.; Pufahl, P.K.; Pérez, M.; Brüchert, V.; Vidal, L..
During Ocean Drilling Program Leg 175, 40 holes were drilled at 13 sites, and 8003 m were recovered with the aim of reconstructing the late Neogene history of the Angola-Benguela upwelling system on the southwest African margin. This system is one of the great upwelling regions of the world and is characterized by organic-rich sediments that provide an excellent record of productivity back to the middle Miocene. Understanding the sedimentology and stratigraphy of these sediments will provide important new information on the paleoceanography of this region, including the complex role the ocean plays in global carbon cycling and climate change. This contribution summarizes the sedimentologic and stratigraphic data compiled on board the JOIDES Resolution...
Tipo: Proceedings Paper Palavras-chave: Drilling; Upwelling.
Ano: 1998 URL: http://hdl.handle.net/1834/567
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Sea-surface salinity variations in the northern Caribbean Sea across the Mid-Pleistocene Transition ArchiMer
Sepulcre, S.; Vidal, L.; Tachikawa, K.; Rostek, F.; Bard, E..
By reconstructing past hydrologic variations in the Northern Caribbean Sea and their influence on the stability of the Atlantic Meridional Overturning Circulation (AMOC) during the last 940 ka, we seek to document climate changes in this tropical area in response to the Mid-Pleistocene Transition (MPT). Using core MD03-2628, we estimated past changes in sea surface salinity (SSS) using Delta delta O-18, the difference between the modern, and the past delta O-18 of seawater (obtained by combining alkenone thermometer data with the delta O-18 of the planktonic foraminifera Globigerinoides ruber (white) and corrected for ice-sheet volume effects). Today, the lowest SSS values in the area studied are associated with the northernmost location of the...
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Ano: 2011 URL: https://archimer.ifremer.fr/doc/00228/33887/32232.pdf
Registros recuperados: 9
Primeira ... 1 ... Última
 

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