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2. 230Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Author

Costa, Kassandra M, Hayes, Christopher T, Hillaire‐Marcel, Claude, Hoffmann, Sharon, Jaccard, Samuel L, Jacobel, Allison W, Kienast, Stephanie S, Kipp, Lauren, Lerner, Paul, Lippold, Jörg, Lund, David, Marcantonio, Franco, Anderson, Robert F, McGee, David, McManus, Jerry F, Mekik, Figen, Middleton, Jennifer L, Missiaen, Lise, Not, Christelle, Pichat, Sylvain, Robinson, Laura F, Rowland, George H, Roy‐Barman, Matthieu, Pavia, Frank J, Tagliabue, Alessandro, Torfstein, Adi, Winckler, Gisela, Zhou, Yuxin, Bausch, Alexandra, Deng, Feifei, Dutay, Jean‐Claude, Geibert, Walter, Heinze, Christoph, and Henderson, Gideon

Subjects
Geosciences (General)
Published
2020
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5. 230 Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Author

Costa, Kassandra M., Hayes, Christopher T., Anderson, Robert F., Pavia, Frank J., Bausch, Alexandra, Deng, Feifei, Dutay, Jean‐Claude, Geibert, Walter, Heinze, Christoph, Henderson, Gideon, Hillaire‐Marcel, Claude, Hoffmann, Sharon, Jaccard, Samuel L., Jacobel, Allison W., Kienast, Stephanie S., Kipp, Lauren, Lerner, Paul, Lippold, Jörg, Lund, David, Marcantonio, Franco, McGee, David, McManus, Jerry F., Mekik, Figen, Middleton, Jennifer L., Missiaen, Lise, Not, Christelle, Pichat, Sylvain, Robinson, Laura F., Rowland, George H., Roy‐Barman, Matthieu, Tagliabue, Alessandro, Torfstein, Adi, Winckler, Gisela, Zhou, Yuxin, Costa, Kassandra M., Hayes, Christopher T., Anderson, Robert F., Pavia, Frank J., Bausch, Alexandra, Deng, Feifei, Dutay, Jean‐Claude, Geibert, Walter, Heinze, Christoph, Henderson, Gideon, Hillaire‐Marcel, Claude, Hoffmann, Sharon, Jaccard, Samuel L., Jacobel, Allison W., Kienast, Stephanie S., Kipp, Lauren, Lerner, Paul, Lippold, Jörg, Lund, David, Marcantonio, Franco, McGee, David, McManus, Jerry F., Mekik, Figen, Middleton, Jennifer L., Missiaen, Lise, Not, Christelle, Pichat, Sylvain, Robinson, Laura F., Rowland, George H., Roy‐Barman, Matthieu, Tagliabue, Alessandro, Torfstein, Adi, Winckler, Gisela, and Zhou, Yuxin

Abstract

© 2020. The Authors. 230Th normalization is a valuable paleoceanographic tool for reconstructing high-resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0–5,000 years ago, or 0–5 ka) and the Last Glacial Maximum (18.5–23.5 ka), and investigated the spatial structure of 230Th-normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79–2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48–1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size-dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (>1,000 m water depth).

Published
2022

8. Book of Abstracts - vDEUQUA2021

Author

Abadi, Mehrdad, Abbasi, Hamidreza, Abd El-Raouf, Amr, Abdulkarim, Mubarak, Adolph, Marie-Luise, Aeschbach, Werner, Akçar, Naki, Amini, Hamideh, Andreev, Andrej, Anselmetti, Flavio S., Aumaître, Georges, Avendaño Villeda, Diana, Bartz, Melanie, Baumhauer, Roland, Bazarradnaa, Enkhtuya, Bebiolka, Anke, Behling, Hermann, Benkaddour, Abdelfattah, Binot, Franz, Birlo, Stella, Bittner, Lucas, Bliedtner, Marcel, Bolland, Alexander, Bork, Hans-Rudolf, Bouaziz, Moncef, Bourlès, Didier, Brauer, Achim, Breuer, Sonja, Bromm, Tobias, Buechi, Marius W., Burghardt, Diana, Busch, Robert, Caballero, Margarita, Carr, Andrew S., Chapkanski, Stoil, Christl, Marcus, Cosac, Marian, Dal Corso, Marta, Daniel, Thomas, Dar, Reyaz, Dave, Aditi Krishna, De Jonge, Cindy, Deplazes, Gaudenz, Dietze, Elisabeth, Dietze, Michael, Dietzel, Martin, Dreibrodt, Stefan, Drysdale, Russell, du Plessis, Nadia, Dubois, Nathalie, Duller, Geoff, Duttmann, Rainer, Duval, Mathieu, Döhlert-Albani, Norman, Egli, Markus, Einwögerer, Thomas, Elbracht, Jörg, Enters, Dirk, Enzel, Yehouda, Ertlen, Damien, Farkas, Beáta, Fattahi, Morteza, Faust, Dominik, Faybishenko, Boris, Feistmantl, Nina, Fernandez, Philippe, Ferrier, Catherine, Fiedler, Sabine, Fischer, Birgit, Fischer, Peter, Fitzsimmons, Kathryn, Fletcher, William, Frechen, Manfred, Fuchs, Margret C., Fuchs, Markus, Fuelling, Alexander, Fábián, Szabolcs, Fülling, Alexander, Garbe, Philipp, Gebhardt, Catalina, Gegg, Lukas, Geis, Anna-Lena, Geitner, Clemens, Ghanbarian, Behzad, Gianotti, Franco, Gil Romera, Graciela, Glaser, Bruno, Glückler, Ramesh, Gresina, Fruzsina, Grootes, Pieter Meiert, Guadelli, Aleta, Guadelli, Jean-Luc, Guérin, Guillaume, Haas, Jean Nicolas, Haberzettl, Torsten, Hambach, Ulrich, Hardt, Jacob, Hein, Michael, Heinrich, Hartmut, Heinrich, Susann, Herzschuh, Ulrike, Heydari, Maryam, Hildebrandt, Dominic, Hirschmann, Philip, Hofmann, Felix Martin, Hofmann, Robert, Hogrefe, Ines, Huang, Jyh-Jaan Steven, Hunt, Allen, Händel, Marc, Ivy-Ochs, Susan, Jary, Zdzisław, Jeanneret, Pilar, Jöris, Olaf, Kalicki, Tomasz, Kamleitner, Sarah, Karaschewski, Jasmin, Keddadouche, Karim, Kehl, Martin, Kern, Zoltán, Kertscher, Cathleen, Khatooni, Darvish, Khosravichenar, Azra, Kipfer, Rolf, Kirchner, André, Kirleis, Wiebke, Klaes, Björn, Knitter, Daniel, Kolb, Thomas, Konstantinovski Puntos, Cyryl, Kreienbrink, Frauke, Kreutzer, Sebastian, Kulongoski, Justin, Laag, Christian, Labahn, Jakob, Lachner, Johannes, Lak, Razyeh, Lamb, Henry F., Lampe, Reinhard, Lang, Jörg, Lange-Athinodorou, Eva, Lauer, Tobias, Leanni, Laetitia, Leblanc, Jean-Claude, Lee, An-Sheng, Lehmkuhl, Frank, Lempe, Bernhard, Lerch, Marcel, Liou, Sofia Ya Hsuan, Lisa, Lenka, Liu, Zuorui, Lomax, Johanna, Lorenz, Sebastian, Lozano García, Socorro, Madarász, Balázs, Madritsch, Herfried, Maier, Andreas, Mangelsdorf, Kai, Markovic, Slobodan, Martinez Abarca, Luis Rodrigo, Marx, Samuel, May, Jan-Hendrik, Mayr, Christoph, Meister, Julia, Merchel, Silke, Meszner, Sascha, Meyer, Juliane, Mikdad, Abdeslam, Milevski, Ivica, Mir, Jehangeer, Mischke, Steffen, Mohammadi, Ali, Monegato, Giovanni, Moreiras, Stella, Mueller, Daniela, Muratoreanu, George, Müller, Daniela, Müller, Johannes, Nadeau, Marie-Josée, Nett, Janina, Neugebauer, Ina, Ng, Jessica, Nill, Leon, Nir, Nadav, Ohlendorf, Christian, Opp, Christian, Orgeira, Maria, Ortega Guerrero, Beatriz, Pasda, Clemens, Pasda, Kerstin, Penkman, Kirsty, Peric, Zoran, Pichat, Sylvain, Piller, Werner, Polgar, Irene, Prendergast, Amy, Preusser, Frank, Prud'homme, Charlotte, Pötter, Stephan, Quick, Lynne J., Rambeau, Claire, Reichert, Markus, Reimann, Tony, Reiss, Lilian, Roettig, Christopher-Bastian, Rolf, Christian, Russell, James, Ruszkiczay-Rüdiger, Zsófia, Ryzner, Kamila, Sahakyan, Lilit, Salazar, Gary, Salomon, Ferréol, Sardar Abadi, Mehrdad, Sarı, Selma, Scardia, Giancarlo, Schiestl, Robert, Schimmelpfennig, Irene, Schirmer, Wolfgang, Schmidt, Christoph, Schmidt, Johannes, Schmitt, Laurent, Schneider, Birgit, Schulte, Philipp, Schulze, Tabea, Schunke, Torsten, Schwab, Markus J., Schwahn, Lea, Schwamborn, Georg, Schwark, Lorenz, Schäfer, Dieter, Schütt, Brigitta, Seltzer, Alan, Selzer, Johnnes, Severinghaus, Jeffrey, Shah, Rayees, Simon, Ulrich, Sirakov, Nikolay, Sirakova, Svoboda, Sontag-González, Mariana, Sprafke, Tobias, Stahlschmidt, Mareike, Stauber, Theresa, Steier, Peter, Steiner, Martin, Stojakowits, Philipp, Strobel, Paul, Stroessner, Kathrin, Struck, Julian, Stute, Martin, Stutzriemer, Marika, Stäuble, Harald, Szidat, Sönke, Taneva, Stanimira, Tanner, David, ASTER, Team, Temovski, Marjan, Tinapp, Christian, Tjallingii, Rik, Trappe, Julian, Tylmann, Wojciech, Ulfers, Arne, Ullmann, Tobias, Urban, Brigitte, van Meer, Mike, Varga, György, Veres, Daniel, Verstraeten, Gert, Videiko, Michail, Vinnepand, Mathias, Vockenhuber, Christof, Vogel, Hendrik, Voigt, Silke, von Suchodoletz, Hans, Vött, Andreas, Weiß, Marcel, Werther, Lukas, Wolf, Daniel, Wonik, Thomas, Wrozyna, Claudia, Wunderlich, Tina, Zech, Michael, Zech, Roland, Zeeden, Christian, Zielhofer, Christoph, Zolitschka, Bernd, Zöller, Ludwig, Żurek, Krzysztof, von Suchodoletz, Hans, Dietze, Elisabeth, Dietze, Michael, Meister, Julia, Wrozyna, Claudia, Zeeden, Christian, Kreutzer, Sebastian, and Hildebrandt, Dominic

Subjects
Quaternary, Conference abstracts, Geoscience
Abstract

Collection of conference abstracts presented at the vDEUQUA2021 (2021-09-30 to 2021-09-01), the virtual meeting of the German Quaternary Association (DEUQUA).

Published
2021
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12. Centennial to millennial-scale variability of Holocene climate and environmental dynamics in the western Mediterranean (Lake Sidi Ali, Middle Atlas, Morocco)

Author

Schmidt, Johannes, primary, Kertscher, Cathleen, additional, Reichert, Markus, additional, Ballasus, Helen, additional, Schneider, Birgit, additional, Dietze, Elisabeth, additional, Tjallingii, Rik, additional, Benkkadour, Abdelfattah, additional, Mikdad, Abdselam, additional, Werther, Lukas, additional, Bolland, Alexander, additional, Pichat, Sylvain, additional, von Suchodoletz, Hans, additional, Fletcher, William, additional, Mischke, Steffen, additional, and Zielhofer, Christoph, additional

Published
2021
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13. Sub-decadal scale coupling of the Moroccan Sidi Ali lake core record with historical and meteorological data for the last 120 years

Author

Kertscher, Cathleen, primary, Schmidt, Johannes, additional, Ballasus, Helen, additional, Schneider, Birgit, additional, Köhler, Anne, additional, Flörke-Staats, Maja, additional, Dietze, Elisabeth, additional, Benkkadour, Abdelfattah, additional, Mikdad, Abdeslam, additional, Werther, Lukas, additional, Bolland, Alexander, additional, Pichat, Sylvain, additional, von Suchodoletz, Hans, additional, Fletcher, William, additional, Mischke, Steffen, additional, and Zielhofer, Christoph, additional

Published
2021
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18. 230 Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Author

Costa, Kassandra M., primary, Hayes, Christopher T., additional, Anderson, Robert F., additional, Pavia, Frank J., additional, Bausch, Alexandra, additional, Deng, Feifei, additional, Dutay, Jean‐Claude, additional, Geibert, Walter, additional, Heinze, Christoph, additional, Henderson, Gideon, additional, Hillaire‐Marcel, Claude, additional, Hoffmann, Sharon, additional, Jaccard, Samuel L., additional, Jacobel, Allison W., additional, Kienast, Stephanie S., additional, Kipp, Lauren, additional, Lerner, Paul, additional, Lippold, Jörg, additional, Lund, David, additional, Marcantonio, Franco, additional, McGee, David, additional, McManus, Jerry F., additional, Mekik, Figen, additional, Middleton, Jennifer L., additional, Missiaen, Lise, additional, Not, Christelle, additional, Pichat, Sylvain, additional, Robinson, Laura F., additional, Rowland, George H., additional, Roy‐Barman, Matthieu, additional, Tagliabue, Alessandro, additional, Torfstein, Adi, additional, Winckler, Gisela, additional, and Zhou, Yuxin, additional

Published
2020
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19. 230 Th normalization: new insights on an essential tool for quantifying sedimentary fluxes in the modern and quaternary ocean

Author

Costa, Kassandra M., Hayes, Christopher T., Anderson, Robert F., Pavia, Frank, Bausch, Alexandra, Deng, Feifei, Dutay, Jean-Claude, Geibert, Walter, Heinze, Christoph, Henderson, Gideon M., Hillaire‐Marcel, Claude, Hoffmann, Sharon S., Jaccard, Samuel L., Jacobel, Allison W., Kienast, Stephanie S., Kipp, Lauren, Lerner, Paul, Lippold, Jörg, Lund, David C., Marcantonio, Franco, McGee, David, McManus, Jerry F., Mekik, Figen, Middleton, Jennifer L., Missiaen, Lise, Not, Christelle, Pichat, Sylvain, Robinson, Laura F., Rowland, George H., Roy-Barman, Matthieu, Tagliabue, Alessandro, Torfstein, Adi, Winckler, Gisela, Zhou, Yuxin, Costa, Kassandra M., Hayes, Christopher T., Anderson, Robert F., Pavia, Frank, Bausch, Alexandra, Deng, Feifei, Dutay, Jean-Claude, Geibert, Walter, Heinze, Christoph, Henderson, Gideon M., Hillaire‐Marcel, Claude, Hoffmann, Sharon S., Jaccard, Samuel L., Jacobel, Allison W., Kienast, Stephanie S., Kipp, Lauren, Lerner, Paul, Lippold, Jörg, Lund, David C., Marcantonio, Franco, McGee, David, McManus, Jerry F., Mekik, Figen, Middleton, Jennifer L., Missiaen, Lise, Not, Christelle, Pichat, Sylvain, Robinson, Laura F., Rowland, George H., Roy-Barman, Matthieu, Tagliabue, Alessandro, Torfstein, Adi, Winckler, Gisela, and Zhou, Yuxin

Abstract

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Costa, K. M., Hayes, C. T., Anderson, R. F., Pavia, F. J., Bausch, A., Deng, F., Dutay, J., Geibert, W., Heinze, C., Henderson, G., Hillaire-Marcel, C., Hoffmann, S., Jaccard, S. L., Jacobel, A. W., Kienast, S. S., Kipp, L., Lerner, P., Lippold, J., Lund, D., Marcantonio, F., McGee, D., McManus, J. F., Mekik, F., Middleton, J. L., Missiaen, L., Not, C., Pichat, S., Robinson, L. F., Rowland, G. H., Roy-Barman, M., Alessandro, Torfstein, A., Winckler, G., & Zhou, Y. 230 Th normalization: new insights on an essential tool for quantifying sedimentary fluxes in the modern and quaternary ocean. Paleoceanography and Paleoclimatology, 35(2), (2020): e2019PA003820, doi:10.1029/2019PA003820., 230Th normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0–5,000 years ago, or 0–5 ka) and the Last Glacial Maximum (18.5–23.5 ka), and investigated the spatial structure of 230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79–2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48–1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size‐dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (>1,000 m water depth)., We thank Zanna Chase and one anonymous reviewer for valuable feedback. K. M. C. was supported by a Postdoctoral Scholarship at WHOI. L. M. acknowledges funding from the Australian Research Council grant DP180100048. The contribution of C. T. H., J. F. M., and R. F. A. were supported in part by the U.S. National Science Foundation (US‐NSF). G. H. R. was supported by the Natural Environment Research Council (grant NE/L002434/1). S. L. J. acknowledges support from the Swiss National Science Foundation (grants PP002P2_144811 and PP00P2_172915). This study was supported by the Past Global Changes (PAGES) project, which in turn received support from the Swiss Academy of Sciences and the US‐NSF. This work grew out of a 2018 workshop in Aix‐Marseille, France, funded by PAGES, GEOTRACES, SCOR, US‐NSF, Aix‐Marseille Université, and John Cantle Scientific. All data are publicly available as supporting information to this document and on the National Center for Environmental Information (NCEI) at https://www.ncdc.noaa.gov/paleo/study/28791.

Published
2020

21. Rbiative timing of precipitation and ocean circui In changes in the western equatorial Atlantic over the last 45 kyr

Author

Waelbroeck, Claire, Pichat, Sylvain, Bohm, Evelyn, Lougheed, Bryan C., Faranda, Davide, Vrac, Mathieu, Missiaen, Lise, Vazquez Riveiros, Natalia, Burckel, Pierre, Lippold, Joerg, Arz, Helge W., Dokken, Trond, Thil, Francois, and Dapoigny, Arnaud

Abstract

Thanks to its optimal location on the northern Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e., Greenland stadials). These rainfall events are recorded in MD09-3257 as peaks in ln(Ti / Ca). New sedimentary Pa / Th data indicate that mid-depth western equatorial water mass transport decreased during all of the Greenland stadials of the last 40 kyr. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sedimentary Pa / Th and ln(Ti/Ca) signals. We show that decreased water mass transport between a depth of similar to 1300 and 2300 m in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 120 to 400 yr at Dansgaard-Oeschger (D-O) frequencies, and by 280 to 980 yr at Heinrich-like frequencies. We suggest that the large lead of ocean circulation changes with respect to changes in tropical South American precipitation at Heinrich-like frequencies is related to the effect of a positive feedback involving iceberg discharges in the North Atlantic. In contrast, the absence of widespread ice rafted detrital layers in North Atlantic cores during D-O stadials supports the hypothesis that a feedback such as this was not triggered in the case of D-O stadials, with circulation slowdowns and subsequent changes remaining more limited during D-O stadials than Heinrich stadials.

Published
2018

22. Downcore Variations of Sedimentary Detrital ( 238U/ 232Th) Ratio: Implications on the Use of 230Thxs and 231Paxs to Reconstruct Sediment Flux and Ocean Circulation

Author

Missiaen, Lise, Pichat, Sylvain, Waelbroeck, Claire, Douville, Eric, Bordier, Louise, Dapoigny, Arnaud, Thil, François, Foliot, L., Wacker, Lukas, Paléocéanographie (PALEOCEAN), 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)-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), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Climate Geochemistry Department [Mainz], Max Planck Institute for Chemistry (MPIC), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, Géochrononologie Traceurs Archéométrie (GEOTRAC), Géochimie Des Impacts (GEDI), Laboratory of Ion Beam Physics, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), 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), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, U‐series nuclides, detrital correction, excess fraction, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Panoply
Abstract

Excess 231Pa and 230Th (231Paxs and 230Thxs) can be used to reconstruct past oceanic sedimentation (230Th‐normalized flux) and circulation changes ((231Pa/230Th)xs,0, hereafter Pa/Th). These quantities are determined by computing the detrital and authigenic contributions from bulk sediment measurement. The method relies on the use of a chosen constant value of the detrital (238U/232Th) activity ratio (hereafter (U/Th)det). In this study, we have extracted the detrital fraction of the sediments from North Atlantic deep‐sea core SU90‐08 (43°03′1N, 30°02′5W, 3,080m) and determined its (U/Th)det value over the last 40 ky. We find that (U/Th)det varied significantly through time with a minimum value of 0.4 during the Holocene and a maximum value of 0.7 during the Last Glacial Maximum (LGM). The sensitivity of sedimentary 230Th‐normalized flux and Pa/Th is tested for our study site and for other North Atlantic sites. We show that the sensitivity is highly dependent on the core location and its terrigenous material supply. The 230Th‐normalized flux and Pa/Th signals are very robust in cores with low detrital contributions, whereas they are very sensitive to (U/Th)det changes in cores with higher detrital contribution. In the latter case, changes in 230Th‐normalized flux and Pa/Th due to the choice of a constant (U/Th)det can largely exceed the uncertainty on the 230Th‐normalized flux and Pa/Th, inducing potential biases in the amplitude and temporal variability of reconstructed sedimentation and ocean circulation changes., Geochemistry, Geophysics, Geosystems, 19 (8), ISSN:1525-2027

Published
2018
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25. Relative timing of precipitation and ocean circulation changes in the western equatorial Atlantic over the last 45 kyr

Author

Waelbroeck, Claire, Pichat, Sylvain, Böhm, Evelyn, Lougheed, Bryan C., Faranda, Davide, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)

Subjects
[SDU]Sciences of the Universe [physics]
Published
2018
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26. Relative timing of precipitation and ocean circulation changes in the western equatorial Atlantic over the last 45 kyr

Author

Waelbroeck, Claire, primary, Pichat, Sylvain, additional, Böhm, Evelyn, additional, Lougheed, Bryan C., additional, Faranda, Davide, additional, Vrac, Mathieu, additional, Missiaen, Lise, additional, Vazquez Riveiros, Natalia, additional, Burckel, Pierre, additional, Lippold, Jörg, additional, Arz, Helge W., additional, Dokken, Trond, additional, Thil, François, additional, and Dapoigny, Arnaud, additional

Published
2018
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27. Supplementary material to "Relative timing of precipitation and ocean circulation changes in the western equatorial Atlantic over the last 45 ky"

Author

Waelbroeck, Claire, primary, Pichat, Sylvain, additional, Böhm, Evelyn, additional, Lougheed, Bryan C., additional, Faranda, Davide, additional, Vrac, Mathieu, additional, Missiaen, Lise, additional, Vazquez Riveiros, Natalia, additional, Burckel, Pierre, additional, Lippold, Jörg, additional, Arz, Helge W., additional, Dokken, Trond, additional, Thil, François, additional, and Dapoigny, Arnaud, additional

Published
2018
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29. Carbon isotopes and Pa / Th response to forced circulation changes: a model perspective.

Author

Missiaen, Lise, Bouttes, Nathaelle, Roche, Didier M., Dutay, Jean-Claude, Quiquet, Aurélien, Waelbroeck, Claire, Pichat, Sylvain, and Peterschmitt, Jean-Yves

Abstract

Understanding the ocean circulation changes associated with last glacial abrupt climate events is key to better assess climate variability and understand its different natural modes. Sedimentary Pa / Th, benthic δ13C and Δ14C are common proxies used to reconstruct past circulation flow rate and ventilation. To overcome the limitations of each proxy taken separately, a better approach is to produce multi-proxy measurements on a single sediment core. Yet, different proxies can provide conflicting information about past ocean circulation. Thus, modelling them in a consistent physical framework has become necessary to assess the geographical pattern, the timing and sequence of the multi-proxy response to abrupt circulation changes. We have implemented a representation of the 231Pa and 230Th tracers into the model of intermediate complexity iLOVECLIM, which already included δ13C and Δ14C. We have further evaluated the response of these three ocean circulation proxies to a classical abrupt circulation reduction obtained by freshwater addition in the Nordic seas under preindustrial boundary conditions. Without a priori guess, the proxy response is shown to cluster in modes that resemble the modern Atlantic water masses. The clearest and most coherent response is obtained in the deep (> 2,000 m) Northwest Atlantic, where δ13C and Δ14C significantly decrease while Pa / Th increases. This is consistent with observational data across millennial scale events of the last glacial. Interestingly, while in marine records, except in rare instances, the phase relationship between these proxies remains unclear due to large dating uncertainties, in the model the bottom water carbon isotopes (δ13C and Δ14C) response lags the sedimentary Pa / Th response by a few hundred years. [ABSTRACT FROM AUTHOR]

Published
2019
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32. Changes in the geometry and strength of the Atlantic meridional overturning circulation during the last glacial (20-50 ka)

Author

Burckel, Pierre, Waelbroeck, Claire, Luo, Yiming, Roche, Didier M., Pichat, Sylvain, Jaccard, Samuel L., Gherardi, Jeanne, Govin, Aline, Lippold, Jörg, Thil, Francois, Burckel, Pierre, Waelbroeck, Claire, Luo, Yiming, Roche, Didier M., Pichat, Sylvain, Jaccard, Samuel L., Gherardi, Jeanne, Govin, Aline, Lippold, Jörg, and Thil, Francois

Abstract

We reconstruct the geometry and strength of the Atlantic meridional overturning circulation during the Heinrich stadial 2 and three Greenland interstadials of the 2050 ka period based on the comparison of new and published sedimentary Pa-231/Th-230 data with simulated sedimentary Pa-231/Th-230. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present-day North Atlantic deep water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic bottom water (AABW). Our results further show that during Heinrich stadial 2, the deep Atlantic was probably directly affected by a southern-sourced water mass below 2500 m depth, while a slow, southward-flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500 m down to the equator.

Published
2016
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35. Hypoxia induces copper stable isotope fractionation in hepatocellular carcinoma, in a HIF-independent manner

Author

Bondanese, Victor P., primary, Lamboux, Aline, additional, Simon, Melanie, additional, Lafont, Jérôme E., additional, Albalat, Emmanuelle, additional, Pichat, Sylvain, additional, Vanacker, Jean-Marc, additional, Telouk, Philippe, additional, Balter, Vincent, additional, Oger, Philippe, additional, and Albarède, Francis, additional

Published
2016
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36. A Sr, Nd, Hf, and Pb isotope perspective on the genesis and long-term evolution of alkaline magmas from Erebus volcano, Antarctica

Author

Sims, K.W.W, Blichert-Toft, Janne, Kyle, Ph.R., Pichat, Sylvain, Bluzstajn, J., Kelly, P., Ball, L.A, Secrétariat, Sylvie, Laboratoire de Sciences de la Terre (LST), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2008

37. Lower export production during glacial periods in the equatorial Pacific derived from (231Pa/ 230Th)xs,0 measurements in deep-sea sediments

Author

Pichat, Sylvain, Sims, Kenneth, François, Roger, McManus, Jerry, Brown Leger, Susan, Albarède, Francis, Laboratoire de Sciences de la Terre (LST), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
Abstract

International audience

Published
2004
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39. Export fluxes of calcite in the eastern equatorial Pacific from the Last Glacial Maximum to present

Author

Loubere, Paul, Mekik, Figen, Francois, Roger, Pichat, Sylvain, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, eastern equatorial Pacific, glacial-interglacial, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, calcite fluxes
Abstract

International audience; The eastern equatorial Pacific (EEP) is an important center of biological productivity, generating significant organic carbon and calcite fluxes to the deep ocean. We reconstructed paleocalcite flux for the past 30,000 years in four cores collected beneath the equatorial upwelling and the South Equatorial Current (SEC) by measuring ex 230 Th-normalized calcite accumulation rates corrected for dissolution with a newly developed proxy for ''fraction of calcite preserved.'' This method produced very similar results at the four sites and revealed that the export flux of calcite was 30-50% lower during the LGM compared to the Holocene. The internal consistency of these results supports our interpretation, which is also in agreement with emerging data indicating lower glacial productivity in the EEP, possibly as a result of lower nutrient supply from the southern ocean via the Equatorial Undercurrent. However, these findings contradict previous interpretations based on mass accumulation rates (MAR) of biogenic material in the sediment of the EEP, which have been taken as reflecting higher glacial productivity due to stronger wind-driven upwelling.

Published
2004
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41. Export fluxes of calcite in the eastern equatorial Pacific from the Last Glacial Maximum to present

Author

Loubere, Paul, Mekik, Figen, Francois, Roger, Pichat, Sylvain, Loubere, Paul, Mekik, Figen, Francois, Roger, and Pichat, Sylvain

Abstract

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA2018, doi:10.1029/2003PA000986., The eastern equatorial Pacific (EEP) is an important center of biological productivity, generating significant organic carbon and calcite fluxes to the deep ocean. We reconstructed paleocalcite flux for the past 30,000 years in four cores collected beneath the equatorial upwelling and the South Equatorial Current (SEC) by measuring ex230Th-normalized calcite accumulation rates corrected for dissolution with a newly developed proxy for “fraction of calcite preserved.” This method produced very similar results at the four sites and revealed that the export flux of calcite was 30–50% lower during the LGM compared to the Holocene. The internal consistency of these results supports our interpretation, which is also in agreement with emerging data indicating lower glacial productivity in the EEP, possibly as a result of lower nutrient supply from the southern ocean via the Equatorial Undercurrent. However, these findings contradict previous interpretations based on mass accumulation rates (MAR) of biogenic material in the sediment of the EEP, which have been taken as reflecting higher glacial productivity due to stronger wind-driven upwelling., This research was partly supported by NSF grant OCE-0095617 and funds from the Northern Illinois University Graduate School (Loubere); the NASA Michigan Space Grant Consortium Seed Grant for summer, 2001 for 230Th analyses at WHOI (Mekik); the French Ministere de l’Education Nationale, de la Recherche et de la Technologie, and a EURODOC grant from the Region Rhone-Alpes (Pichat).

Published
2010

42. Lower export production during glacial periods in the equatorial Pacific derived from (231Pa/230Th)xs,0 measurements in deep-sea sediments

Author

Pichat, Sylvain, Sims, Kenneth W. W., Francois, Roger, McManus, Jerry F., Leger, Susan Brown, Albarede, Francis, Pichat, Sylvain, Sims, Kenneth W. W., Francois, Roger, McManus, Jerry F., Leger, Susan Brown, and Albarede, Francis

Abstract

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA4023, doi:10.1029/2003PA000994., The (231Pa/230Th)xs,0 records obtained from two cores from the western (MD97-2138; 1°25′S, 146°24′E, 1900 m) and eastern (Ocean Drilling Program Leg 138 Site 849, 0°11.59′N, 110°31.18′W, 3851 m) equatorial Pacific display similar variability over the last 85,000 years, i.e., from isotopic stages 1 to 5a, with systematically higher values during the Holocene, isotopic stage 3, and isotopic stage 5a, and lower values, approaching the production rate ratio of the two isotopes (0.093), during the colder periods corresponding to isotopic stages 2 and 4. We have also measured the 230Th-normalized biogenic preserved and terrigenous fluxes, as well as major and trace elements concentrations, in both cores. The (231Pa/230Th)xs,0 results combined with the changes in preserved carbonate and opal fluxes at the eastern site indicate lower productivity in the eastern equatorial Pacific during glacial periods. The (231Pa/230Th)xs,0 variations in the western equatorial Pacific also seem to be controlled by productivity (carbonate and/or opal). The generally high (231Pa/230Th)xs,0 ratios (>0.093) of the profile could be due to opal and/or MnO2 in the sinking particles. The profiles of (231Pa/230Th)xs,0 and 230Th-normalized fluxes indicate a decrease in exported carbonate, and possibly opal, during isotopic stages 2 and 4 in MD97-2138. Using 230Th-normalized flux, we also show that sediments from the two cores were strongly affected by sediment redistribution by bottom currents suggesting a control of mass accumulation rates by sediment focusing variability., SP funding for this research was provided by grants from the French Minister of Research and a EURODOC grant of the Re´gion Rhoˆne-Alpes (SAFIR-980065327). SP also gratefully acknowledges the financial support of the WHOI Geology and Geophysics Dept. This work was also supported by a CNRS-NSF grant (SP and KWWS). The contribution of JFM to this study was supported in part by the US NSF and by WHOI OCCI and Mellon awards.

Published
2010

44. Lower export production during glacial periods in the equatorial Pacific derived from (231Pa/230Th)xs,0 measurements in deep-sea sediments

Author

Pichat, Sylvain, Sims, Kenneth W. W., Francois, Roger, McManus, Jerry F., Leger, Susan Brown, Albarede, Francis, Pichat, Sylvain, Sims, Kenneth W. W., Francois, Roger, McManus, Jerry F., Leger, Susan Brown, and Albarede, Francis

Abstract

The (231Pa/230Th)xs,0 records obtained from two cores from the western (MD97-2138; 1°25′S, 146°24′E, 1900 m) and eastern (Ocean Drilling Program Leg 138 Site 849, 0°11.59′N, 110°31.18′W, 3851 m) equatorial Pacific display similar variability over the last 85,000 years, i.e., from isotopic stages 1 to 5a, with systematically higher values during the Holocene, isotopic stage 3, and isotopic stage 5a, and lower values, approaching the production rate ratio of the two isotopes (0.093), during the colder periods corresponding to isotopic stages 2 and 4. We have also measured the 230Th-normalized biogenic preserved and terrigenous fluxes, as well as major and trace elements concentrations, in both cores. The (231Pa/230Th)xs,0 results combined with the changes in preserved carbonate and opal fluxes at the eastern site indicate lower productivity in the eastern equatorial Pacific during glacial periods. The (231Pa/230Th)xs,0 variations in the western equatorial Pacific also seem to be controlled by productivity (carbonate and/or opal). The generally high (231Pa/230Th)xs,0 ratios (>0.093) of the profile could be due to opal and/or MnO2 in the sinking particles. The profiles of (231Pa/230Th)xs,0 and 230Th-normalized fluxes indicate a decrease in exported carbonate, and possibly opal, during isotopic stages 2 and 4 in MD97-2138. Using 230Th-normalized flux, we also show that sediments from the two cores were strongly affected by sediment redistribution by bottom currents suggesting a control of mass accumulation rates by sediment focusing variability.

Published
2004

46. Late slowdown of the Atlantic Meridional Overturning Circulation during the Last Glacial Inception: New constraints from sedimentary (231Pa/230Th)

Author

Guihou, Abel, Pichat, Sylvain, Nave, Sìlvia, Govin, Aline, Labeyrie, Laurent, Michel, Elisabeth, and Waelbroeck, Claire

Subjects
*ATLANTIC meridional overturning circulation, *GLACIAL Epoch, *CONSTRAINT satisfaction, *SEDIMENTARY rocks, *PRECIPITATION variability, *DETRITUS, *ICE sheets, *EARTH'S core, *EARTH (Planet)
Abstract

Abstract: Our study gives new constraints on the response of Atlantic Meridional Overturning Circulation (AMOC) export to various forcings during the Last Glacial Inception. The decay corrected excess sedimentary (231Pa/230Th) activity ratio (hereafter referred to as (Pa/Th)) has been measured over that period in two deep cores from the Western (SU90-11, 44°04′N, 40°01′W, 3645m) and Eastern (MD01-2446, 39°03′N, 12°37′W, 3547m) basins of the North Atlantic. Both records display significant changes despite the relatively short half-life of 231Pa (∼32kyr) compared to the period we investigate. The (Pa/Th) variability does not correlate to changes in local opal flux normalized to 230Th. Moreover, the (Pa/Th) profiles display a high degree of coherency with indirect proxies of AMOC activity such as the benthic foraminifera δ13C and the mid-latitude summer Sea Surface Temperature in nearby reference cores. These additional pieces of evidence support our interpretation of the (Pa/Th) as reflecting AMOC export. The (Pa/Th) repeatedly underwent rapid changes during the Last Glacial Inception associated with the extension of ice rafted detritus in the North Atlantic, highlighting the control of ice-sheet dynamics through freshwater forcing on AMOC export. AMOC export remains large during periods of ice-sheet growth and its decreases lag the Northern Hemisphere summer insolation forcing. AMOC modulation appears driven by ice-sheet dynamics, itself driven by the seasonal insolation gradient between low and high Northern Hemisphere latitudes and the associated intensity of the meridional oceanic and atmospheric circulation. [Copyright &y& Elsevier]

Published
2010
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48. 230 Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Author

Costa, Kassandra M., Hayes, Christopher T., Anderson, Robert F., Pavia, Frank J., Bausch, Alexandra, Deng, Feifei, Dutay, Jean‐Claude, Geibert, Walter, Heinze, Christoph, Henderson, Gideon, Hillaire‐Marcel, Claude, Hoffmann, Sharon, Jaccard, Samuel L., Jacobel, Allison W., Kienast, Stephanie S., Kipp, Lauren, Lerner, Paul, Lippold, Jörg, Lund, David, Marcantonio, Franco, McGee, David, McManus, Jerry F., Mekik, Figen, Middleton, Jennifer L., Missiaen, Lise, Not, Christelle, Pichat, Sylvain, Robinson, Laura F., Rowland, George H., Roy‐Barman, Matthieu, Tagliabue, Alessandro, Torfstein, Adi, Winckler, Gisela, and Zhou, Yuxin

Subjects
13. Climate action, 550 Earth sciences & geology, 14. Life underwater
Abstract

230Th normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0–5,000 years ago, or 0–5 ka) and the Last Glacial Maximum (18.5–23.5 ka), and investigated the spatial structure of 230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79–2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48–1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size‐dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (>1,000 m water depth).

49. Lower export production during glacial periods in the equatorial Pacific derived from (231Pa/230Th)xs,0 measurements in deep-sea sediments

Author

Pichat, Sylvain, Sims, Kenneth W. W., François, Roger, McManus, Jerry F., Leger, Susan Brown, and Albarède, Francis

Subjects
13. Climate action, Chemical oceanography, Submarine geology, 14. Life underwater, Hydrology, Paleoclimatology, Marine sediments--Analysis
Abstract

The (231Pa/230Th)xs,0 records obtained from two cores from the western (MD97-2138; 1°25′S, 146°24′E, 1900 m) and eastern (Ocean Drilling Program Leg 138 Site 849, 0°11.59′N, 110°31.18′W, 3851 m) equatorial Pacific display similar variability over the last 85,000 years, i.e., from isotopic stages 1 to 5a, with systematically higher values during the Holocene, isotopic stage 3, and isotopic stage 5a, and lower values, approaching the production rate ratio of the two isotopes (0.093), during the colder periods corresponding to isotopic stages 2 and 4. We have also measured the 230Th-normalized biogenic preserved and terrigenous fluxes, as well as major and trace elements concentrations, in both cores. The (231Pa/230Th)xs,0 results combined with the changes in preserved carbonate and opal fluxes at the eastern site indicate lower productivity in the eastern equatorial Pacific during glacial periods. The (231Pa/230Th)xs,0 variations in the western equatorial Pacific also seem to be controlled by productivity (carbonate and/or opal). The generally high (231Pa/230Th)xs,0 ratios (> 0.093) of the profile could be due to opal and/or MnO2 in the sinking particles. The profiles of (231Pa/230Th)xs,0 and 230Th-normalized fluxes indicate a decrease in exported carbonate, and possibly opal, during isotopic stages 2 and 4 in MD97-2138. Using 230Th-normalized flux, we also show that sediments from the two cores were strongly affected by sediment redistribution by bottom currents suggesting a control of mass accumulation rates by sediment focusing variability.

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