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A Middle Pleistocene Northeast Atlantic coccolithophore record: Paleoclimatology and paleoproductivity aspects 5
Amore, F. O.; Flores, J. A.; Voelker, A. H. L.; Lebreiro, S. M.; Palumbo, E.; Sierro, F. J..
Changes in paleoclimate and paleoproductivity patterns have been identified by analysing, in conjunction with other available proxy data, the coccolithophore assemblages from core MD03-2699, located in the Portuguese margin in the time interval from the Marine Isotope Stage (MIS) 13/14 boundary to MIS 9 (535 to 300 ka). During the Mid-Brunhes event, the assemblages associated with the eccentricity minima are characterised by higher nannoplankton accumulation rate (NAR) values and by the blooming of the opportunistic genus Gephyrocapsa. Changes in coccolithophore abundance are also related to glacial-interglacial cycles. Higher NAR and numbers of coccoliths/g mainly occurred during the interglacial periods, while these values decreased during the glacial...
Tipo: Text Palavras-chave: North Atlantic Ocean; Mid-Pleistocene; Coccolithophores; Paleoclimate; Paleoproductivity.
Ano: 2012 URL: https://archimer.ifremer.fr/doc/00092/20286/17946.pdf
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A 500 kyr record of global sea-level oscillations in the Gulf of Lion, Mediterranean Sea: new insights into MIS 3 sea-level variability 5
Frigola, J.; Canals, M.; Cacho, I.; Moreno, A.; Sierro, F. J.; Flores, J. A.; Berne, Serge; Jouet, Gwenael; Dennielou, Bernard; Herrera, G.; Pasqual, C.; Grimalt, J. O.; Galavazi, M.; Schneider, R..
Borehole PRGL1-4 drilled in the upper slope of the Gulf of Lion provides an exceptional record to investigate the impact of late Pleistocene orbitally-driven glacio-eustatic sea-level oscillations on the sedimentary outbuilding of a river fed continental margin. High-resolution grain-size and geochemical records supported by oxygen isotope chronostratigraphy allow reinterpreting the last 500 ka upper slope seismostratigraphy of the Gulf of Lion. Five main sequences, stacked during the sea-level lowering phases of the last five glacial-interglacial 100-kyr cycles, form the upper stratigraphic outbuilding of the continental margin. The high sensitivity of the grain-size record down the borehole to sea-level oscillations can be explained by the great width of...
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00088/19944/17599.pdf
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Holocene climate variability in the western Mediterranean region from a deepwater sediment record 5
Frigola, J.; Moreno, A.; Cacho, I.; Canals, M.; Sierro, F. J.; Flores, J. A.; Grimalt, J. O.; Hodell, D. A.; Curtis, J. H..
The detailed analysis of the International Marine Past Global Changes Study core MD99-2343 recovered from a sediment drift at 2391 m water depth north of the island of Minorca illustrates the effects of climate variability on thermohaline circulation in the western Mediterranean during the last 12 kyr. Geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the Western Mediterranean Basin during the Holocene. Superimposed on the general trend, eight centennial- to millennial-scale abrupt events appear consistently in both grain size and geochemical records, which supports the occurrence of episodes of deepwater overturning reinforcement in the...
Tipo: Text Palavras-chave: Holocene climate variability; Thermohaline circulation; Western Mediterranean Sea.
Ano: 2007 URL: https://archimer.ifremer.fr/doc/00233/34448/32900.pdf
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Late Pleistocene paleoproductivity patterns during the last climatic cycle in the Guyana Basin as revealed by calcareous nannoplankton 5
López-otálvaro, G.-e.; Flores, J. A.; Sierro, F. J.; Cacho, I.; Grimalt, J.-o.; Michel, Elisabeth; Cortijo, E.; Labeyrie, L..
Variations in the assemblages and abundances of calcareous nannoplankton have allowed us to interpret changes in oceanic and atmospheric dynamics in the Guyana Basin, mainly linked to the southeast trades over the last climatic cycle. Records of the paleoproductivity index of coccolithophores (N ratio) allowed us to monitor the nutri-thermocline fluctuations. Additionally, nannofossil accumulation rates vary closely with the N ratio, indicating a strong correlation between these two paleoproductivity proxies. The dominance of upper (small Noelaerhabdaceae, Emiliania huxleyi and Gephyrocapsa oceanica), over lower photic zone dwellers (Florisphaera profunda) during Termination II and interglacial substages 5.1 and 5.3 is related to eutrophic conditions due...
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Ano: 2008 URL: https://archimer.ifremer.fr/doc/00240/35111/33608.pdf
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Parallelisms between sea surface temperature changes in the western tropical Atlantic (Guiana Basin) and high latitude climate signals over the last 140 000 years 5
Rama-corredor, O.; Martrat, B.; Grimalt, J. O.; Lopez-otalvaro, G. E.; Flores, J. A.; Sierro, F..
Sea surface temperatures (SST) in the Guiana Basin over the last 140 ka were obtained by measuring the C37 alkenone unsaturation index Uk'37 in the sediment core MD03-2616 (7° N, 53° W). The resulting data set is unique in the western tropical Atlantic region for this period. The SSTs range from 25.1 to 28.9 °C, i.e. glacial–interglacial amplitude of 3.8 °C, which is in the range of change of other tropical areas. During the last two interglacial stages (marine isotope stages; MIS1 and MIS5e) and warm long interstadials (MIS5d-a), a rapid transmission of climate variability from Arctic–tropical latitudes is recorded. During these periods, the MD03-2616 SSTs show a conspicuous parallelism with temperature changes observed in Greenland and SST records of...
Tipo: Text
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00296/40765/39760.pdf
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Evidence of early bottom water current flow after the Messinian Salinity Crisis in the Gulf of Cadiz 5
Van Der Schee, Marlies; Sierro, F. J.; Jimenez-espejo, F. J.; Hernandez-molina, F. J.; Flecker, R.; Flores, J. A.; Acton, G.; Gutjahr, M.; Grunert, P.; Garcia-gallardo, A.; Andersen, N..
Integrated Ocean Drilling Program (IODP) Expedition 339 cored multiple sites in the Gulf of Cadiz in order to study contourite deposition resulting from Mediterranean Outflow water (MOW). One Hole, U1387C, was cored to a depth of 865.85 m below seafloor (mbsf) with the goal of recovering the latest Miocene to Pliocene transition in order to evaluate the history of MOW immediately after the end of the Messinian Salinity Crisis. To understand this history, an accurate age model for the succession is needed, but is challenging to construct, because the Miocene-Pliocene boundary is not marked by a clear biostratigraphic event in the Atlantic and coring gaps occur within the recovered stratigraphic record. These limitations are overcome by combining a variety...
Tipo: Text Palavras-chave: Miocene-Pliocene boundary; Gulf of Cadiz; IODP Expedition 339; Mediterranean outflow water; Messinian salinity crisis; Contourites.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00421/53217/54843.pdf
Registros recuperados: 6
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