Search

Your search keyword '"Turon, J.-L."' showing total 136 results
Start Over Author "Turon, J.-L."
136 results on '"Turon, J.-L."'

1. Long- and Short Term Holocene Variations in the Strength of the North Atlantic Deep Water at the Charlie-Gibbs fracture zone

Author

Kissel, C., Turon, J. L., Cortijo, E., Laj, C., Laboratoire des Sciences du Climat et de l'Environnement (LSCE), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
[SDU]Sciences of the Universe [physics]
Abstract

International audience; The precise documentation of the natural variability of the THC during the interglacials in North Atlantic is of critical interest for the understanding of its future evolution under the effect of global warming. It is one of the goals of the AMOCINT project (06-EuroMARC-FP-008). We report on detailed magnetic analyses of a Holocene marine sequence taken at the Charlie-Gibbs fracture zone (52°S), on the path of the contourite drift at the place where it turns around the Reykjanes ridge, from the Gardar drift northward. This location has been sampled twice. The first core (gravity) has been taken in 1977 with the R.V. J. Charcot from IFREMER. The second one (Casq core) has been taken during the IMAGES MD168-AMOCINT cruise on board the R. V. Marion Dufresne in 2008 (IPEV). In the first core, the apparent sedimentation rate varies between 50 and 79 cm/kyr and it obviously results from compaction as the second one known to be free of any distortion has sedimentation rates of the order of 50 to 140 cm/kyr between present and 10 kyr B.P. The two cores can be perfectly correlated using any physical property allowing to precisely transfer the 19 radiocarbon dates from the old series to the new one. Detailed magnetic analyses have been performed on both cores and will be compared. The magnetic fraction is uniformly composed during the Holocene period of magnetites with a grain size distribution in the pseudo-single domain range (a few micrometers). The magnetic concentration varies in time on both long and short terms. The long-term trends may be fitted by a 4th order polynomial with an increase of the bottom circulation strength in the mid-Holocene. We shall discuss these long term trends together with the short term features in terms of changes in the strength of the bottom current through Holocene and compare them to other proxies an other records also obtained from North Atlantic.

Published
2023

4. Late Quaternary co-seismic sedimentation in the Sea of Marmara's deep basins

Author

Beck, Christian, Mercier de Lépinay, Bernard, Schneider, Jean-Luc, Cremer, Michel, Çağatay, Namik, Wendenbaum, Evrard, Boutareaud, Sébastien, Ménot, Guillemette, Schmidt, Sabine, Weber, Olivier, Eris, Kadir, Armijo, Rolando, Meyer, Bertrand, Pondard, Nicolas, Gutscher, Marc-André, Turon, J.-L., Labeyrie, L., Cortijo, E., Gallet, Y., Bouquerel, Hélène, Gorur, N., Gervais, A., Castera, M.-H., Londeix, L., de Rességuier, A., and Jaouen, A.

Published
2007
Full Text
View/download PDF

11. Atlas of modern dinoflagellate cyst distribution based on 2405 datapoints

Author

Zonneveld, K.A.F., Marret, F., Versteegh, G.J.M., Bogus, K., Bonnet, S., Bouimetarhan, I., Crouch, E., de Vernal, A., Elshanawany, R., Edwards, L., Esper, O., Forke, S., Grøsfjeld, K., Henry, M., Holzwarth, U., Kielt, J.-F., Kim, S.-Y., Ladouceur, S., Ledu, D., Chen, L., Limoges, A., Londeix, L., Lu, S.-H., Mahmoud, M.S., Marino, G., Matsouka, K., Matthiessen, J., Mildenhal, D.C., Mudie, P., Neil, H.L., Pospelova, V., Qi, Y., Radi, T., Richerol, T., Rochon, A., Sangiorgi, F., Solignac, S., Turon, J.-L., Verleye, T., Wang, Y., Wang, Z., and Young, M.

Subjects
Holocene, World, Dinoflagellata
Abstract

Dinoflagellate cysts are useful for reconstructing upper water conditions. For adequate reconstructions detailed information is required about the relationship between modern day environmental conditions and the geographic distribution of cysts in sediments. This Atlas summarises the modern global distribution of 71 organic-walled dinoflagellate cyst species. The synthesis is based on the integration of literature sources together with data of 2405 globally distributed surface sediment samples that have been prepared with a comparable methodology and taxonomy. The distribution patterns of individual cyst species are being compared with environmental factors that are known to influence dinoflagellate growth, gamete production, encystment, excystment and preservation of their organic-walled cysts: surface water temperature, salinity, nitrate, phosphate, chlorophyll-a concentrations and bottom water oxygen concentrations. Graphs are provided for every species depicting the relationship between seasonal and annual variations of these parameters and the relative abundance of the species. Results have been compared with previously published records; an overview of the ecological significance as well as information about the seasonal production of each individual species is presented.The relationship between the cyst distribution and variation in the aforementioned environmental parameters was analysed by performing a canonical correspondence analysis. All tested variables showed a positive relationship on the 99% confidence level. Sea-surface temperature represents the parameter corresponding to the largest amount of variance within the dataset (40%) followed by nitrate, salinity, phosphate and bottom-water oxygen concentration, which correspond to 34%, 33%, 25% and 24% of the variance, respectively. Characterisations of selected environments as well as a discussion about how these factors could have influenced the final cyst yield in sediments are included.

Published
2013

12. Tracking atmospheric and riverine terrigenous supplies variability during the last glacial and the Holocene in central Mediterranean

Author

Bout‑Roumazeilles, Viviane, Combourieu-Nebout, N, Desprat, S, Siani, G, Turon, J-L, Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), ANR-07-BLAN-0009,LAMA,Holocene changes in environment and climate, and history of human societies in Central Mediterranean as reflected by LAke and MArine records(2007), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE)

Subjects
010504 meteorology & atmospheric sciences, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, 010502 geochemistry & geophysics, 01 natural sciences, 0105 earth and related environmental sciences
Abstract

The objectives were to retrace the eolian and fluvial terrigenous supplies in a sediment core from the Sicilian-Tunisian Strait by coupling mineralogical, grain-size and geochemical approaches, in order to get informations on the atmospheric versus riverine contributions to sedimentation on the southern side of central Mediterranean since the last glacial. The eolian supply is dominant over the whole interval, excepted during the sapropel S1 when riverine contribution apparently became significant, and particles provenance has been modified since Last Glacial. Saharan contribution increased during the Bølling-Allerød, evidencing the persistence of aridity over North Africa although the northern Mediterranean already experienced moister and warmer conditions. The Younger Dryas is marked by proximal dust inputs highlighting intense regional eolian activity. A southward migration of dust provenance toward Sahel occurred at the onset of the Holocene, likely resulting from a southward position of the Inter Tropical Convergence Zone, probably associated with a large-scale atmospheric reorganization. Finally, a peculiar high terrigenous flux associated with drastic modifications of the mineralogical and geochemical sediment signature occurred during the sapropel S1, suggesting the propagation of fine-particles derived from major floodings of the Nile River – resulting from enhanced rainfall on northeastern Africa – and their transportation across the Sicilian-Tunisian Strait by intermediate water-masses.

Published
2012
Full Text
View/download PDF

13. Variations of the Antarctic Circumpolar Current intensity during the past 500 ka

Author

Mazaud, A., Michel, Elisabeth, Dewilde, F., Turon, J. L., Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Climat et Magnétisme (CLIMAG), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Paléocéanographie (PALEOCEAN), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE)

Subjects
7 figures Keywords: Antarctic, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, cycles, 1635 Global Change: Oceans (1616, Components: 4200 words, cycles Index Terms: 1512 Geomagnetism and Paleomagnetism: Environmental magnetism, current, Antarctic, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, past, 4513)
Abstract

International audience; [1] We examine the past variations of the Antarctic Circumpolar Current (ACC) by using variations in size and abundance of the magnetic grains deposited by this current at a site east the Kerguelen-Crozet plateau. Core MD00-2375G was taken at a midlatitude site during the ANTAUS cruise conducted in 2000 by the French R/V Marion Dufresne. Marine isotope stages (MIS) down to MIS 13 are identified, and an age model is derived from a correlation to the ice core isotopic record obtained from EPICA in Antarctica. Continuous records of abundance and size of the magnetic grains were obtained using environmental magnetism methods. Results show a strong modulation of the ACC flow intensity in response to glacial and interglacial cycles. The low abundance and the small size of magnetic grains indicate that the ACC was weak during warm stages and strong during glacial epochs. A large modulation is also observed at the sub-stage scale during the interglacials. A minimum in concentration and grain size occurs at the onset of MIS 11. At the MIS 6-5, 10-9, and possibly 12-11 transitions, observed variations suggest a mechanism involving both rapid and progressive variations of the ACC flow at deglaciations.

Published
2010
Full Text
View/download PDF

14. Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum

Author

Waelbroeck, C., Paul, A., Kucera, Michal, Rosell-Melé, Antoni, Weinelt, Mara, Schneider, Ralph, Mix, Alan C., Abelmann, Andrea, Armand, Leanne, Bard, Edouard, Barker, Stephen, Barrows, Timothy T., Benway, H., Cacho, Isabel, Chen, Min-Te, Cortijo, Elsa, Crosta, X., de Vernal, Anne, Dokken, Trond, Duprat, Josette, Elderfield, Harry, Eynaud, Frédérique, Gersonde, Rainer, Hayes, Angela, Henry, M., Hillaire-Marcel, Claude, Huang, C.-C., Jansen, Eystein, Juggins, Stephen, Kallel, N., Kiefer, Thorsten, Kienast, M., Labeyrie, Laurent, Leclaire, H., Londeix, L., Mangin, S., Matthiessen, Jens, Marret, F., Meland, M., Morey, Ann E., Mulitza, Stefan, Pflaumann, Uwe, Pisias, N. G., Radi, T., Rochon, A., Rohling, Eelco J., Sbaffi, Laura, Schaefer-Neth, C., Solignac, Sandrine, Spero, Howard J., Kazuyo, Tachikawa, Turon, J.-L., Members, Margo Project, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Paléocéanographie (PALEOCEAN), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Department of Geosciences, Institute of Geosciences, Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, Institute of Environmental Science and Technology [Barcelona] (ICTA), Universitat Autònoma de Barcelona (UAB), Institució Catalana de Recerca i Estudis Avançats (ICREA), Service de Chimie Inorganique et Biologique (SCIB - UMR E3), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Centre National de la Recherche Scientifique (CNRS), Collège de France - Chaire Evolution du climat et de l'océan, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Department of Stratigraphy Paleontology and Marine Geosciences, University of Barcelona, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences [Bergen] (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Department of Bentho-pelagic processes, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), Centre de recherche sur la dynamique du système Terre (GEOTOP), École Polytechnique de Montréal (EPM)-McGill University = Université McGill [Montréal, Canada]-Université de Montréal (UdeM)-Université du Québec en Abitibi-Témiscamingue (UQAT)-Université du Québec à Rimouski (UQAR)-Concordia University [Montreal]-Université du Québec à Montréal = University of Québec in Montréal (UQAM), Unité GEOGLOB, Faculté des Sciences de Sfax, Université de Sfax - University of Sfax-Université de Sfax - University of Sfax, Past Global Changes International Project Office (PAGES), Past Global Changes International Project Office, Centre d'Études Biologiques de Chizé (CEBC), Centre National de la Recherche Scientifique (CNRS), School of Environmental Sciences, University of Liverpool, Center for Marine Environmental Sciences [Bremen] (MARUM), Universität Bremen, National Oceanography Centre [Southampton] (NOC), University of Southampton, Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Chaire Evolution du climat et de l'océan, Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Université de Montréal (UdeM)-McGill University = Université McGill [Montréal, Canada]-École Polytechnique de Montréal (EPM)-Concordia University [Montreal]-Université du Québec à Rimouski (UQAR)-Université du Québec à Montréal = University of Québec in Montréal (UQAM)-Université du Québec en Abitibi-Témiscamingue (UQAT), Centre d'études biologiques de Chizé (CEBC), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Institut Pierre-Simon-Laplace (IPSL), École normale supérieure - Paris (ENS Paris)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National d'Études Spatiales [Toulouse] (CNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Eberhard Karls Universität Tübingen, Universitat Autònoma de Barcelona [Barcelona] (UAB), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), University of Bergen (UIB), École Polytechnique de Montréal (EPM)-Université McGill -Université de Montréal (UdeM)-Université du Québec en Abitibi-Témiscamingue (UQAT)-Université du Québec à Rimouski (UQAR)-Concordia University [Montreal]-Université du Québec à Montréal (UQAM), PAGES International Project Office, Zähringerstrasse 25, 3122 Bern, Switzerland, Univsersity of Liverpool, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] ( LSCE ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay-Centre National de la Recherche Scientifique ( CNRS ), Institut Pierre-Simon-Laplace ( IPSL ), École normale supérieure - Paris ( ENS Paris ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Centre National d'Etudes Spatiales ( CNES ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Inst. of Environmental Science and Technology (ICTA), Institució Catalana de Recerca i Estudis Avançats, Institució Catalana de Recerca i Estudis Avançats ( ICREA ), Service de Chimie Inorganique et Biologique ( SCIB - UMR E3 ), Institut Nanosciences et Cryogénie ( INAC ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Grenoble Alpes ( UGA ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Grenoble Alpes ( UGA ) -Centre National de la Recherche Scientifique ( CNRS ), Centre européen de recherche et d'enseignement de géosciences de l'environnement ( CEREGE ), Centre National de la Recherche Scientifique ( CNRS ) -Institut de Recherche pour le Développement ( IRD ) -Aix Marseille Université ( AMU ) -Collège de France ( CdF ) -Institut National de la Recherche Agronomique ( INRA ) -Institut national des sciences de l'Univers ( INSU - CNRS ), Environnements et Paléoenvironnements OCéaniques ( EPOC ), Observatoire aquitain des sciences de l'univers ( OASU ), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -École pratique des hautes études ( EPHE ) -Centre National de la Recherche Scientifique ( CNRS ), Bjerknes Centre for Climate Research ( BCCR ), University of Bergen ( UIB ), Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse ( CSNSM ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ), Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research ( AWI ), California Institute of Technology ( CALTECH ), GEOTOP-UQAM-McGill, Faculté des sciences de Sfax, Centre d'études biologiques de Chizé ( CEBC ), Centre National de la Recherche Scientifique ( CNRS ), MARUM &ndash, Center For Marine Environmental Sciences, National Oceanography Centre [Southampton] ( NOC ), and University of Southampton [Southampton]

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Climate change, Last Glacial Maximum, 010502 geochemistry & geophysics, 01 natural sciences, Sea surface temperature, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, 13. Climate action, Climatology, Paleoclimate Modelling Intercomparison Project, Deglaciation, General Earth and Planetary Sciences, Climate sensitivity, 14. Life underwater, Glacial period, Oceanic basin, [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Geology, 0105 earth and related environmental sciences
Abstract

International audience; Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations 1. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2,3). Since that time, several shortcomings of that earlier effort have become apparent 4. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project 5. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present 6,7. Studies following the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project mainly reanalysed old primary data, applied single new proxies or concentrated on specific ocean basins 8-11. The Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project's objective has been to compile and analyse available estimates of Last Glacial Maximum (LGM) sea surface temperatures (SSTs) based on all prevalent microfossil-based (transfer functions based on planktonic foraminifera, diatom, dinoflagellate cyst and radiolarian abundances) and geochemical (alkenones and planktonic foraminifera Mg/Ca) palaeothermometers. The MARGO project approach is to argue that no current proxy method is objectively better than another to provide an accurate picture of past SST, and that consequently the multiproxy approach yields the least biased representation of past reality. By using a rigorous definition of the LGM time interval (19-23 cal kyr bp; ref. 4), many records used previously had to be discarded. Other key features are the use of a common data set of ambient temperatures for the calibration of all proxies and the assessment of the reliability of individual SST estimates 5. The MARGO compilation combines 696 individual SST reconstructions (Fig.

Published
2009
Full Text
View/download PDF

15. Determining the absolute abundance of dinoflagellate cysts in recent marine sediments: the Lycopodium marker-grain method put to the test

Author

Mertens, K.N., Verhoeven, K., Verleye, T.J., Louwye, S., Amorim, A., Ribeiro, S., Deaf, A.S., Harding, I.C., De Schepper, S., Kodrans-Nsiah, M., de Vernal, A., Radi, T., Dybkjaer, K., Poulsen, N.E., Feist-burkhardt, S., Chitolie, J., González Arango, C., Heilmann-Clausen, C., Londeix, L., Turon, J.-L., Marret, F., Matthiessen, J., McCarthy, F.M.G., Prasad, V., Pospelova, V., Kyffin Hughes, J.E., Riding, J.B., Rochon, A., Sangiorgi, F., Welters, N., Sinclair, N., Thun, C., Soliman, A.K., Van Nieuwenhove, N., Vink, A., and Young, M.

Subjects
Lycopodium clavatum, Dinoflagellata
Abstract

Absolute abundances (concentrations) of dinoflagellate cysts are often determined through the addition of Lycopodium clavatum marker-grains as a spike to a sample before palynological processing. An inter-laboratory calibration exercise was set up in order to test the comparability of results obtained in different laboratories, each using its own preparation method. Each of the 23 laboratories received the same amount of homogenized splits of four Quaternary sediment samples. The samples originate from different localities and consisted of a variety of lithologies. Dinoflagellate cysts were extracted and counted, and relative and absolute abundances were calculated. The relative abundances proved to be fairly reproducible, notwithstanding a need for taxonomic calibration. By contrast, excessive loss of Lycopodium spores during sample preparation resulted in non-reproducibility of absolute abundances. Use of oxidation, KOH, warm acids, acetolysis, mesh sizes larger than 15 µm and long ultrasonication (> 1 min) must be avoided to determine reproducible absolute abundances. The results of this work therefore indicate that the dinoflagellate cyst worker should make a choice between using the proposed standard method which circumvents critical steps, adding Lycopodium tablets at the end of the preparation and using an alternative method.

Published
2009

16. Determining the absolute abundance of dinoflagellate cysts in recent marine sediments:The Lycopodium marker-grain method put to the test

Author

Mertens, K.N., Verhoeven, K., Verleye, T., Louwye, S., Amorim, A., Ribeiro, S., Deaf, A.S., Harding, I.C., De Schepper, S., Gonzales, C., Kodrans-Nsiah, M., De Vernal, A., Henry, M., Radi, T., Dybkjær, K., Poulsen, N.E., Feist-Burkhardt, S., Chitolie, J., Heilmann-Clausen, Claus, Londeix, L., Turon, J.-L., Marett, F., Matthiessen, J., McCarthy, F.M.G., Prasad, V., Pospelova, V., Kyffin Hughes, J.E., Riding, J.B., Rochon, A., Sangiorgi, F., Welters, N., Sinclair, N., Thun, C., Soliman, A., Van Nieuwenhove, Nicolas, Vink, A., and Young, M.

Published
2009

17. The absolute abundance calibration project: the Lycopodium marker-grain method put to the test

Author

Mertens, K., Amorim, A., Ribeiro, S., Deaf, A.S., Harding, I., De Schepper, S., de Vernal, A., Radi, T., Dybkjaer, K., Poulsen, N., Feist-Burkhardt, S., Chitolie, J., González, C., Heilmann-Clausen, C., Kodrans-Nsiah, M., Londeix, L., Turon, J.-L., Marret, F., Matthiessen, J., McCarthy, F., Prasad, V., Pospelova, V., Hughes, J.K., Riding, A.B., Rochon, A., Sangiorgi, F., Marino, G., Welters, N., Sinclair, N., Thun, C., Soliman, A., Van Nieuwenhove, N., Vink, A., Verhoeven, K., Verleye, T., Louwye, S., and Young, M.

Abstract

Traditionally, dinoflagellate cyst concentrations are calculated by adding an exotic marker or “spike” (such as Lycopodium clavatum) to each sample following the method of Stockmarr (1971). According to Maher (1981), the total error is controlled mainly by the error on the count of Lycopodium clavatum spores. In general, the more L. clavatum spores counted, the lower the error. A dinocyst / L. clavatum spore ratio of ~2 will give optimal results in terms of precision and time spent on a sample. It has also been proven that the use of the aliquot method yields comparable results to the marker-grain method (de Vernal et al., 1987). Critical evaluation of the effect of different laboratory procedures on the marker grain concentration in each sample has never been executed. Although, it has been reported that different processing methods (e.g. ultrasonication, oxidizing, etc.) are to a certain extent damaging to microfossils (e.g. Hodgkinson, 1991), it is not clear how this is translated into concentration calculations. It is wellknown from the literature that concentration calculations of dinoflagellate cysts from different laboratories are hard to resolve into a consistent picture. The aim of this study is to remove these inconsistencies and to make recommendations for the use of a standardized methodology. Sediment surface samples from four different localities (North Sea, Celtic Sea, NW Africa and Benguela) were macerated in different laboratories each using its own palynological maceration technique. A fixed amount of Lycopodium clavatum tablets was added to each sample. The uses of different preparation methodologies (sieving, ultrasonicating, oxidizing …) are compared using both concentrations – calculated from Lycopodium tablets - and relative abundances (more destructive methods will increase the amount of resistant taxa). Additionally, this study focuses on some important taxonomic issues, since obvious interlaboratorial differences in nomenclature are recorded.

Published
2008

19. Tracking atmospheric and riverine terrigenous supplies variability during the last glacial and the Holocene in central Mediterranean

Author

Bout-roumazeilles, Viviane, Combourieu-nebout, N., Desprat, S., Siani, G., Turon, J. -l., Essallami, L., Bout-roumazeilles, Viviane, Combourieu-nebout, N., Desprat, S., Siani, G., Turon, J. -l., and Essallami, L.

Abstract

A multiproxy study coupling mineralogical, grain size and geochemical approaches was used to tentatively retrace eolian and fluvial contributions to sedimentation in the Sicilian Tunisian Strait since the last glacial. The eolian supply is dominant over the whole interval, excepted during the sapropel Si when riverine contribution apparently became significant. Saharan contribution increased during the B011ing Allerod, evidencing the persistence of aridity over North Africa although the northern Mediterranean already experienced moister and warmer conditions. The Younger Dryas is marked by proximal dust inputs, highlighting intense regional eolian activity. A southward migration of dust provenance toward Sahel occurred at the onset of the Holocene, likely resulting from a southward position of the Inter Tropical Convergence Zone that was probably associated with a large-scale atmospheric reorganization. Finally, a peculiar high terrigenous flux associated with drastic modifications of the mineralogical and geochemical sediment signature occurred during the sapropel 51, suggesting the propagation of fine particles derived from major floodings of the Nile River resulting from enhanced rainfall on northeastern Africa and their transportation across the Sicilian Tunisian Strait by intermediate water masses.

Published
2013
Full Text
View/download PDF

20. Deglacial and Holocene vegetation and climatic changes in the southern Central Mediterranean from a direct land-sea correlation

Author

Desprat, S., Combourieu-nebout, N., Essallami, L., Sicre, Marie-alexandrine, Dormoy, I., Peyron, O., Siani, G., Roumazeilles, V. Bout, Turon, J. L., Desprat, S., Combourieu-nebout, N., Essallami, L., Sicre, Marie-alexandrine, Dormoy, I., Peyron, O., Siani, G., Roumazeilles, V. Bout, and Turon, J. L.

Abstract

Despite a large number of studies, the long-term and millennial to centennial-scale climatic variability in the Mediterranean region during the last deglaciation and the Holocene is still debated, including in the southern Central Mediterranean. In this paper, we present a new marine pollen sequence (core MD04-2797CQ) from the Siculo-Tunisian Strait documenting the regional vegetation and climatic changes in the southern Central Mediterranean during the last deglaciation and the Holocene. The MD04-2797CQ marine pollen sequence shows that semi-desert plants dominated the vegetal cover in the southern Central Mediterranean between 18.2 and 12.3 ka cal BP, indicating prevailing dry conditions during the deglaciation, even during the Greenland Interstadial (GI)-1. Across the transition Greenland Stadial (GS)-1 -Holocene, Asteraceae-Poaceae steppe became dominant till 10.1 ka cal BP. This record underlines with no chronological ambiguity that even though temperatures increased, deficiency in moisture availability persisted into the early Holocene. Temperate trees and shrubs with heath underbrush or maquis expanded between 10.1 and 6.6 ka, corresponding to Sapropel 1 (S1) interval, while Mediterranean plants only developed from 6.6 ka onwards. These changes in vegetal cover show that the regional climate in southern Central Mediterranean was wetter during S1 and became drier during the mid-to late Holocene. Wetter conditions during S1 were likely due to increased winter precipitation while summers remained dry. We suggest, in agreement with published modeling experiments, that the early Holocene increased melting of the Laurentide Ice Sheet in conjunction with weak winter insolation played a major role in the development of winter precipitation maxima in the Mediterranean region in controlling the strength and position of the North Atlantic storm track. Finally, our data provide evidence for centennial-scale vegetation and climatic changes in the southern Central Mediterr

Published
2013
Full Text
View/download PDF

21. Atlas of modern dinoflagellate cyst distribution based on 2405 data points

Author

Zonneveld, K.A.F., Marret, F., Versteegh, G.J.M., Bogus, K., Bonnet, S., Bouimetarhan, I., Crouch, E., de Vernal, A., Elshanawany, R., Edwards, L., Esper, O., Forke, S., Grøsfjeld, K., Henry, M., Holzwarth, U., Kielt, J.-F., Kim, S.-Y., Ladouceur, S., Ledu, D., Chen, L., Limoges, A., Londeix, L., Lu, S.-H., Mahmoud, M.S., Marino, G., Matsouka, K., Matthiessen, J., Mildenhal, D.C., Mudie, P., Neil, H.L., Pospelova, V., Qi, Y., Radi, T., Richerol, T., Rochon, A., Sangiorgi, F., Solignac, S., Turon, J.-L., Verleye, T., Wang, Y., Young, M., Zonneveld, K.A.F., Marret, F., Versteegh, G.J.M., Bogus, K., Bonnet, S., Bouimetarhan, I., Crouch, E., de Vernal, A., Elshanawany, R., Edwards, L., Esper, O., Forke, S., Grøsfjeld, K., Henry, M., Holzwarth, U., Kielt, J.-F., Kim, S.-Y., Ladouceur, S., Ledu, D., Chen, L., Limoges, A., Londeix, L., Lu, S.-H., Mahmoud, M.S., Marino, G., Matsouka, K., Matthiessen, J., Mildenhal, D.C., Mudie, P., Neil, H.L., Pospelova, V., Qi, Y., Radi, T., Richerol, T., Rochon, A., Sangiorgi, F., Solignac, S., Turon, J.-L., Verleye, T., Wang, Y., and Young, M.

Published
2013

23. Assessment of sea surface temperature changes in the Gulf of Cadiz during the last 30 ka: implications for glacial changes in the regional hydrography

Author

Penaud, Aurelie, Eynaud, F., Voelker, A., Kageyama, M., Marret, F., Turon, J. L., Blamart, D., Mulder, T., Rossignol, L., Penaud, Aurelie, Eynaud, F., Voelker, A., Kageyama, M., Marret, F., Turon, J. L., Blamart, D., Mulder, T., and Rossignol, L.

Abstract

New dinocyst analyses were conducted on core MD99-2339 retrieved from the central Gulf of Cadiz. Dinocyst and foraminiferal assemblages from this core are combined with existing data off SW Portugal and NW Morocco to investigate past hydrological and primary productivity regimes in the subtropical NE Atlantic Ocean over the last 30 ka. Our results have revealed highest upwelling intensity during Heinrich Stadial 1 (HS 1) and the Younger Dryas and weaker upwelling cells during the Last Glacial Maximum (LGM) and HS 2, off the SW Iberian and NW Moroccan margins. Similar assemblages between the Gulf of Cadiz and the NW Moroccan margin, and distinct species off Portugal, were observed during the cold climatic extremes that punctuated the last 30 ka. This pattern has been linked to the occurrence of a hydrological structure between SW Iberia and Cadiz during the last glacial period, perhaps similar to the modern Azores Front. This front was probably responsible locally for heterotrophic dinocysts found in the Gulf of Cadiz during the last glacial period, even if this sector is not conductive to upwelling phenomena by Ekman transport. Regional reconstructions of paleo-sea-surface temperatures (SSTs) using dinocyst and foraminiferal transfer functions, as well as alkenones, are also discussed and depict coherent scenarios over the last 30 ka. Seasonal reconstructions of LGM SSTs obtained with this multi-proxy panel are discussed jointly with model outputs in order to contribute to ongoing efforts in model-data comparison.

Published
2011
Full Text
View/download PDF

24. Timing of massive ‘Fleuve Manche’ discharges over the last 350 kyr: insights into the European ice-sheet oscillations and the European drainage network from MIS 10 to 2

Author

Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Cremer, M., Eynaud, Frederique, Van Vliet-lanoe, B., Penaud, A., Fontanier, C., Turon, J. L., Cortijo, E., Gibbard, P. L., Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Cremer, M., Eynaud, Frederique, Van Vliet-lanoe, B., Penaud, A., Fontanier, C., Turon, J. L., Cortijo, E., and Gibbard, P. L.

Abstract

Continuous high-resolution mass accumulation rates (MAR) and X-ray fluorescence (XRF) measurements from marine sediment records in the Bay of Biscay (NE Atlantic) have allowed the determination of the timing and the amplitude of the ‘Fleuve Manche’ (Channel River) discharges during glacial stages MIS 10, MIS 8, MIS 6 and MIS 4–2. These results have yielded detailed insight into the Middle and Late Pleistocene glaciations in Europe and the drainage network of the western and central European rivers over the last 350 kyr. This study provides clear evidence that the ‘Fleuve Manche’ connected the southern North Sea basin with the Bay of Biscay during each glacial period and reveals that ‘Fleuve Manche’ activity during the glaciations MIS 10 and MIS 8 was significantly less than during MIS 6 and MIS 2. We correlate the significant ‘Fleuve Manche’ activity, detected during MIS 6 and MIS 2, with the extensive Saalian (Drenthe Substage) and the Weichselian glaciations, respectively, confirming that the major Elsterian glaciation precedes the glacial MIS 10. In detail, massive ‘Fleuve Manche’ discharges occurred at ca 155 ka (mid-MIS 6) and during Termination I, while no significant discharges are found during Termination II. It is assumed that a substantial retreat of the European ice sheet at ca 155 kyr, followed by the formation of ice-free conditions between the British Isles and Scandinavia until Termination II, allowed meltwater to flow northwards through the North Sea basin during the second part of the MIS 6. We assume that this glacial pattern corresponds to the Warthe Substage glacial maximum, therefore indicating that the data presented here equates to the Drenthe and the Warthe glacial advances at ca 175–160 ka and ca 150–140 ka, respectively. Finally, the correlation of our records with ODP site 980 reveals that massive ‘Fleuve Manche’ discharges, related to partial or complete melting of the European ice masses, were synchronous with strong decreases in both th

Published
2009
Full Text
View/download PDF

25. What forced the collapse of European ice sheets during the last two glacial periods (150 ka BP and 18 ka cal BP)? Palynological evidence

Author

Penaud, A., Eynaud, F., Turon, J. L., Zaragosi, S., Malaize, B., Toucanne, Samuel, Bourillet, Jean-francois, Penaud, A., Eynaud, F., Turon, J. L., Zaragosi, S., Malaize, B., Toucanne, Samuel, and Bourillet, Jean-francois

Abstract

We present a new marine palynological record from the temperate North-eastern Atlantic (core MD03-2692, Celtic-Armorican margin) in the area of influence of the 'Fleuve Manche' paleoriver during glacial times. The runoff of this paleoriver was connected to the glacial history of European ice sheets (including the British Irish Ice Sheet-BIIS). Our study conducted on dinoflagellate cysts assemblages over the last 200 ka, associated with quantification of palynological remains reflecting continental influence (pre-Quaternary dinocysts and micro-algae Pediastrum spp. coenobia), yields detailed insights into the sea-surface paleoenvironments of this sector. More specifically, mechanisms responsible for the origin of unusual deposits of laminated sequences found at the end of Marine Isotope Stage (MIS) 2 and within mid-MIS 6 are here constrained. We provide evidence of genetic similarities between fluvial discharges occurring before and during times of deposition of the laminated deposits. Our study clarifies the causes of the collapse of European glaciated systems. At the end of MIS 2, prior to the deposition of the laminated deposits, plenioceanic influence characterized by high concentrations of Quaternary dinocysts prevailed, and a dinocyst species tracing the penetration of the warm North Atlantic Drift into the Bay of Biscay is recorded. However, this scenario did not recur prior to the deposition of laminated sediments of mid-MIS 6. In addition, contrary to the laminated deposits found at the end of MIS 2 and directly associated with Termination I, MIS 6 laminae appeared 20 ka earlier than Termination II. Our work shows that, during the penultimate glacial stage, the collapse of mid-latitudes ice sheets around 170 ka B.P. may have immediately followed the MIS 6.5 warming phase. Then, the most important melting event around 150 ka B.P. may be linked to a peak in insolation at 65 degrees N, though less important than those during MIS 6.5 and Termination II.

Published
2009
Full Text
View/download PDF

26. A 1.2 Ma record of glaciation and fluvial discharge from the West European Atlantic margin

Author

Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Gibbard, P. L., Eynaud, F., Giraudeau, J., Turon, J. L., Cremer, M., Cortijo, E., Martinez, P., Rossignol, L., Toucanne, Samuel, Zaragosi, S., Bourillet, Jean-francois, Gibbard, P. L., Eynaud, F., Giraudeau, J., Turon, J. L., Cremer, M., Cortijo, E., Martinez, P., and Rossignol, L.

Abstract

The correlation of continental sedimentary records with the marine isotope stratigraphy is a challenge of central importance in Quaternary stratigraphy, particularly in Western Europe where long records of glaciation on land areas are particularly rare. Here we demonstrate for the first time the interrelationship of events during the last 1.2 Ma in an ocean-sediment core from the Bay of Biscay (NE Atlantic), SW of the Channel. The identification of discharge variations from tributary river systems to the 'Fleuve Manche' palaeoriver during glacio-eustatic sea-level lowstands demonstrates the correlation of the marine sediment stratigraphy to the expansion and recession of the European ice-sheets. The amplitude and chronology of European ice-sheet oscillations since the late Early Pleistocene is discussed and our results demonstrate that the first coalescence of the Fennoscandian and British ice-sheets in the North Sea basin ca 450 ka ago caused a profound change in lowstand European drainage alignment. This change caused a rerouting of Fennoscandian and eastern British ice-sheets-derived meltwaters from northwards into the Nordic Seas to southwards into the eastern North Atlantic thereafter. Besides allowing a thorough synchronisation of the European ice-sheet palaeogeography with the well-dated records of palaeoceanographical changes, our results improve the stratigraphy of the English Channel palaeovalleys and will provide important constraints on paleoclimatic scenarios considering the impact that such rerouting and meltwater surges might have on the stability of the oceanic conveyor belt.

Published
2009
Full Text
View/download PDF

27. Determining the absolute abundance of dinoflagellate cysts in recent marine sediments: the Lycopodium marker-grain method put to the test

Author

Mertens, Kenneth Neil, Verhoeven, K., Verleye, T., Louwye, S., Amorim, A., Ribeiro, S., Deaf, A. S., Hardubg, I. C., De Schepper, S., González, C., Kodrans-Nsiah, M., de Vernal, A., Henry, M., Radi, T., Dybkjaer, K., Poulsen, N. E., Feist-Burkhardt, S., Chitolie, J., Heilmann-Clausen, C., Londeix, L., Turon, J.-L., Marret, F., Matthiessen, Jens, McCarthy, F. M. G., Prasad, V., Pospelova, V., Kyffin Hughes, J. E., Riding, J. B., Rochon, A., Sangiorgi, F., Welters, N., Sinclair, N., Thun, C., Soliman, A., Van Nieuwenhove, Nicolas, Vink, A., Young, M., Mertens, Kenneth Neil, Verhoeven, K., Verleye, T., Louwye, S., Amorim, A., Ribeiro, S., Deaf, A. S., Hardubg, I. C., De Schepper, S., González, C., Kodrans-Nsiah, M., de Vernal, A., Henry, M., Radi, T., Dybkjaer, K., Poulsen, N. E., Feist-Burkhardt, S., Chitolie, J., Heilmann-Clausen, C., Londeix, L., Turon, J.-L., Marret, F., Matthiessen, Jens, McCarthy, F. M. G., Prasad, V., Pospelova, V., Kyffin Hughes, J. E., Riding, J. B., Rochon, A., Sangiorgi, F., Welters, N., Sinclair, N., Thun, C., Soliman, A., Van Nieuwenhove, Nicolas, Vink, A., and Young, M.

Abstract

Absolute abundances (concentrations) of dinoflagellate cysts are often determined through the addition of Lycopodium clavatum marker-grains as a spike to a sample before palynological processing. An interlaboratory calibration exercise was set up in order to test the comparability of results obtained in different laboratories, each using its own preparation method. Each of the 23 laboratories received the same amount of homogenized splits of four Quaternary sediment samples. The samples originate from different localities and consisted of a variety of lithologies. Dinoflagellate cysts were extracted and counted, and relative and absolute abundances were calculated. The relative abundances proved to be fairly reproducible, notwithstanding a need for taxonomic calibration. By contrast, excessive loss of Lycopodium spores during sample preparation resulted in non-reproducibility of absolute abundances. Use of oxidation, KOH, warm acids, acetolysis, mesh sizes larger than 15 μm and long ultrasonication (N1 min) must be avoided to determine reproducible absolute abundances. The results of this work therefore indicate that the dinoflagellate cyst worker should make a choice between using the proposed standard method which circumvents critical steps, adding Lycopodium tablets at the end of the preparation and using an alternative method.

Published
2009

28. The absolute abundance calibration project: the Lycopodium marker-grain method put to the test

Author

Mertens, K. N., Verhoeven, K., Verleye, T., Louwye, S., Amorim, A., Ribeiro, S., Deaf, A. S., Harding, I., de Schepper, S., Kodrans-Nsiah, Monika, De Vernal, A., Henry, M., Radi, T., Dybkjaer, K., Poulsen, N. E., Feist-Brukhardt, S., Chitolie, J., González Arango, C., Heilmann-Clausen, C., Londeix, L., Turon, J. L., Marret, F., Matthießen, Jens, McCarthy, F., Prasad, V., Pospelova, V., Kyffin Hughes, J., Riding, J. B., Rochon, A., Sangiorgi, F., Welters, N., Sinclair, N., Thun, C., Soliman, A., Van Nieuwenhove, N., Vink, A., Young, M., Mertens, K. N., Verhoeven, K., Verleye, T., Louwye, S., Amorim, A., Ribeiro, S., Deaf, A. S., Harding, I., de Schepper, S., Kodrans-Nsiah, Monika, De Vernal, A., Henry, M., Radi, T., Dybkjaer, K., Poulsen, N. E., Feist-Brukhardt, S., Chitolie, J., González Arango, C., Heilmann-Clausen, C., Londeix, L., Turon, J. L., Marret, F., Matthießen, Jens, McCarthy, F., Prasad, V., Pospelova, V., Kyffin Hughes, J., Riding, J. B., Rochon, A., Sangiorgi, F., Welters, N., Sinclair, N., Thun, C., Soliman, A., Van Nieuwenhove, N., Vink, A., and Young, M.

Published
2009

29. North–south palaeohydrological contrasts in the central Mediterranean during the Holocene: tentative synthesis and working hypotheses

Author

Magny, M., primary, Combourieu-Nebout, N., additional, de Beaulieu, J. L., additional, Bout-Roumazeilles, V., additional, Colombaroli, D., additional, Desprat, S., additional, Francke, A., additional, Joannin, S., additional, Ortu, E., additional, Peyron, O., additional, Revel, M., additional, Sadori, L., additional, Siani, G., additional, Sicre, M. A., additional, Samartin, S., additional, Simonneau, A., additional, Tinner, W., additional, Vannière, B., additional, Wagner, B., additional, Zanchetta, G., additional, Anselmetti, F., additional, Brugiapaglia, E., additional, Chapron, E., additional, Debret, M., additional, Desmet, M., additional, Didier, J., additional, Essallami, L., additional, Galop, D., additional, Gilli, A., additional, Haas, J. N., additional, Kallel, N., additional, Millet, L., additional, Stock, A., additional, Turon, J. L., additional, and Wirth, S., additional

Published
2013
Full Text
View/download PDF

31. Variations of the ACC-CDW during MIS3 traced by magnetic grain deposition in midlatitude South Indian Ocean cores: Connections with the northern hemisphere and with central Antarctica

Author

Mazaud, A., Kissel, C., Laj, C., Sicre, M. A., Michel, E., Turon, J. L., Mazaud, A., Kissel, C., Laj, C., Sicre, M. A., Michel, E., and Turon, J. L.

Abstract

We examine the magnetic mineral deposition in three cores located at midlatitude sites in the South Indian Ocean, in an area where sediment eroded from the Kerguelen-Crozet plateau and transported by the marine currents, principally the Antarctic Circum Current, accumulates at a high sedimentation rate. We focus on Marine Isotopic Stage 3, characterized by large climatic fluctuations at northern latitudes, and compare the obtained records to the climatic records at Byrd ( Antarctica) and Summit (GISP2, Greenland) and to the North Atlantic Deep Water variations in the North Atlantic. Magnetic mineral deposition at the studied sites exhibits a profile with maxima at the time of Heinrich events H4 and H5, which suggests a strong Antarctic Circum Current when the North Atlantic Deep Water was reduced at northern latitude during these events. We show that an interhemispheric seesaw, characterized by temporary surface warmings in the southern hemisphere, is also marked by a strong Antarctic Circum Current at the time of the northern Heinrich events. The rapid Dansgaard-Oeschger oscillations evidenced in the northern records after interstadials IS12 and IS8 are not visible, suggesting a limited counterpart of these events in the midlatitude southern Indian Ocean.

Published
2007
Full Text
View/download PDF

39. Deep-penetration heat flow probes raise questions about interpretations from shorter probes

Author

Géli, Louis, Turon, J.-l., Aslanian, Daniel, Balut, Y., Beuzart, Paul, Cochran, J., Francheteau, J., Harmegnies, Francois, Landuré, Jean-yves, Le Suavé, Raymond, Mazaud, A., Michel, E., Normand, Alain, Pichon, Jack, Vlastelic, Ivan, Géli, Louis, Turon, J.-l., Aslanian, Daniel, Balut, Y., Beuzart, Paul, Cochran, J., Francheteau, J., Harmegnies, Francois, Landuré, Jean-yves, Le Suavé, Raymond, Mazaud, A., Michel, E., Normand, Alain, Pichon, Jack, and Vlastelic, Ivan

Published
2001
Full Text
View/download PDF

40. Dinoflagellate cyst assemblages as tracers of sea-surface conditions in the northern North Atlantic, Arctic and sub-Arctic seas: the new n = 677 data base and its application for quantitative palaeoceanographic reconstruction

Author

Vernal, A. de, Henry, M., Matthießen, Jens, Mudie, P. J., Rochon, A., Boessenkool, K., Eynaud, F., Grøsfjeld, K., Guiot, J., Hamel, D., Harland, R., Head, M. J., Kunz-Pirrung, Martina, Levac, A., Loucheur, V., Peyron, O., Pospelova, V., Radi, T., Turon, J.-L., Voronina, E., Vernal, A. de, Henry, M., Matthießen, Jens, Mudie, P. J., Rochon, A., Boessenkool, K., Eynaud, F., Grøsfjeld, K., Guiot, J., Hamel, D., Harland, R., Head, M. J., Kunz-Pirrung, Martina, Levac, A., Loucheur, V., Peyron, O., Pospelova, V., Radi, T., Turon, J.-L., and Voronina, E.

Published
2001

41. Late Quaternary variations of sea ice and sea-surface conditions in the Arctic and circum-Arctic based on dinocyst assemblages: preliminary results and methological issues

Author

de Vernal, A., Blake, W. jr., Darby, D., Hamel, D. D., Hillaire-Marcel, C., Grøsfjeld, K., Kunz-Pirrung, Martina, Levac, E., Matthießen, Jens, Mudie, P. J., Peyron, O., Polyak, L., Radi, T., Rochon, A., Turon, J. L., Voronina, E., de Vernal, A., Blake, W. jr., Darby, D., Hamel, D. D., Hillaire-Marcel, C., Grøsfjeld, K., Kunz-Pirrung, Martina, Levac, E., Matthießen, Jens, Mudie, P. J., Peyron, O., Polyak, L., Radi, T., Rochon, A., Turon, J. L., and Voronina, E.

Published
2000

42. Reconstruction of sea-surface temperature, salinity, and sea-ice cover in the northern Atlantic Ocean during the last glacial maximum based on dinocyst assemblages

Author

Vernal, A. de, Hillaire-Marcel, C., Turon, J.-L., Matthießen, Jens, Vernal, A. de, Hillaire-Marcel, C., Turon, J.-L., and Matthießen, Jens

Abstract

Past sea-surface conditions over the northern North Atlantic during the last glacial maximum were examined from the study of 61 deep-sea cores. The last glacial maximum time slice studied here corresponds to an interval between Heinrich layers H2 and H1, and spanningabout 20-16 ka on a 14C time scale. Transfer functions based on dinocyst assemblages were used to reconstruct sea-surface temperature, salinity, and sea-ice cover. The results illustrate extensive sea-ice cover along the eastern Canadian margins and sea-ice spreading, only during winter, over most of the northern North Atlantic. On the whole, much colder winter prevailed, despite relatively mild conditions in August (10-15°C at most offshore sites), thus suggesting a larger seasonal contrast of temperatures than today. Lower salinity than at present is reconstructed, especially along the eastern Canadian and Scandinavian margins, likely because of meltwater supply from the surrounding ice sheets. These reconstructions contrast with those established by CLIMAP on the basis of planktonic foraminifera. These differences are discussed with reference to the stratigraphical frame of the last glacial maximum, which was not the coldest phase of the last glacial stage. The respective significance of dinocyst and foraminifer records is also examined in terms of the thermohaline characteristics of surface waters and the vertical structure of upper water masses, which was apparently much more stratified than at present in the northern North Atlantic, thus preventing deep-water formation.

Published
2000

47. Distribution of recent dinoflagellate cysts in surface sediments from the North Atlantic Ocean and adjacent seas in relation to sea-surface parameters

Author

Rochon, A., Vernal, A. de, Turon, J.-L., Matthießen, Jens, Head, M. J., Rochon, A., Vernal, A. de, Turon, J.-L., Matthießen, Jens, and Head, M. J.

Abstract

Surface sediments at 439 sites throughout the North Atlantic Ocean and adjacent seas have been analyzed for dinoflagellate cysts in order to establish a reference database from which paleoenvironmental transfer functions can be developed. Laboratory procedures and systematics were standardized in order to avoid bias introduced by the selective loss of taxa and to facilitate site to site comparison. 371 sites were retained to develop the database that includes 41 taxa, some of which were grouped using morphological and/or ecological criteria. 27 taxa were retained for statistical purposes. Distribution maps of these latter taxa have been plotted on the basis of their relative abundance. Principal component analyses were performed in order to describe the distribution of assemblages. The relation between the assemblages, as well as the relative abundance of individual taxa, and selected sea-surface parameters are illustrated. The parameters which were considered include temperature and salinity for winter (February) and summer (August) together with the duration of sea-ice cover. Transfer functions using the best analogue method have been tested with a view to reconstruct past sea-surface parameters. Validation procedures on this transfer function demonstrate that more than 95% of the reconstructions are included within the interannual variability of modern sea-surface conditions. Therefore, these transfer functions give accurate results and can be applied to reconstructing paleotemperatures and salinities from analogous assemblages in Quaternary sedimentary sequences.Protoperidinium stellatum (Wall in Wall & Dale, 1968) Head, comb. nov. (basionym = Peridinium stellatum) is proposed as new, and Algidasphaeridium? minutum var. cezare de Vernal et al., 1989 ex de Vernal et al. is newly validated.

Published
1999

Catalog

Books, media, physical & digital resources
See catalog results