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1. Contrasted release of insoluble elements (Fe, Al, rare earth elements, Th, Pa) after dust deposition in seawater: a tank experiment approach

Author

M. Roy-Barman, L. Foliot, E. Douville, N. Leblond, F. Gazeau, M. Bressac, T. Wagener, C. Ridame, K. Desboeufs, and C. Guieu

Subjects
Ecology, QH540-549.5, Life, QH501-531, Geology, QE1-996.5
Abstract

Lithogenic elements such as aluminum (Al), iron (Fe), rare earth elements (REEs), thorium (232Th and 230Th, given as Th) and protactinium (Pa) are often assumed to be insoluble. In this study, their dissolution from Saharan dust reaching Mediterranean seawater was studied through tank experiments over 3 to 4 d under controlled conditions including controls without dust addition as well as dust seeding under present and future climate conditions (+3 ∘C and −0.3 pH). Unfiltered surface seawater from three oligotrophic regions (Tyrrhenian Sea, Ionian Sea and Algerian Basin) were used. The maximum dissolution was low for all seeding experiments: less than 0.3 % for Fe, 1 % for 232Th and Al, about 2 %–5 % for REEs and less than 6 % for Pa. Different behaviors were observed: dissolved Al increased until the end of the experiments, Fe did not dissolve significantly, and Th and light REEs were scavenged back on particles after a fast initial release. The constant 230Th/232Th ratio during the scavenging phase suggests that there is little or no further dissolution after the initial Th release. Quite unexpectedly, comparison of present and future conditions indicates that changes in temperature and/or pH influence the release of Th and REEs in seawater, leading to lower Th release and a higher light REE release under increased greenhouse conditions.

Published
2021
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2. Introduction to the French GEOTRACES North Atlantic Transect (GA01): GEOVIDE cruise

Author

G. Sarthou, P. Lherminier, E. P. Achterberg, F. Alonso-Pérez, E. Bucciarelli, J. Boutorh, V. Bouvier, E. A. Boyle, P. Branellec, L. I. Carracedo, N. Casacuberta, M. Castrillejo, M. Cheize, L. Contreira Pereira, D. Cossa, N. Daniault, E. De Saint-Léger, F. Dehairs, F. Deng, F. Desprez de Gésincourt, J. Devesa, L. Foliot, D. Fonseca-Batista, M. Gallinari, M. I. García-Ibáñez, A. Gourain, E. Grossteffan, M. Hamon, L. E. Heimbürger, G. M. Henderson, C. Jeandel, C. Kermabon, F. Lacan, P. Le Bot, M. Le Goff, E. Le Roy, A. Lefèbvre, S. Leizour, N. Lemaitre, P. Masqué, O. Ménage, J.-L. Menzel Barraqueta, H. Mercier, F. Perault, F. F. Pérez, H. F. Planquette, F. Planchon, A. Roukaerts, V. Sanial, R. Sauzède, C. Schmechtig, R. U. Shelley, G. Stewart, J. N. Sutton, Y. Tang, N. Tisnérat-Laborde, M. Tonnard, P. Tréguer, P. van Beek, C. M. Zurbrick, and P. Zunino

Subjects
Ecology, QH540-549.5, Life, QH501-531, Geology, QE1-996.5
Abstract

The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this special issue (https://www.biogeosciences.net/special_issue900.html), results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among 18 articles. Here, the scientific context, project objectives, and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue.

Published
2018
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3. Downcore Variations of Sedimentary Detrital (238U/232Th) Ratio: Implications on the Use of 230Thxs and 231Paxs to Reconstruct Sediment Flux and Ocean Circulation

Author

L. Missiaen, S. Pichat, C. Waelbroeck, E. Douville, L. Bordier, A. Dapoigny, F. Thil, L. Foliot, and L. Wacker

Subjects
detrital correction, U‐series nuclides, excess fraction, Geophysics. Cosmic physics, QC801-809, Geology, QE1-996.5
Abstract

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.

Published
2018
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4. ESR/U-series chronology of early Neanderthal occupations at Cova Negra (Valencia, Spain)

Author

Murielle Richard, C. Falguères, Pere Miquel Guillem, L. Foliot, Edwige Pons-Branchu, Aleix Eixea, Rafael Martínez-Valle, Valentín Villaverde, Histoire naturelle de l'Homme préhistorique (HNHP), Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), IRAMAT-Centre de recherche en physique appliquée à l’archéologie (IRAMAT-CRP2A), Institut de Recherches sur les Archéomatériaux (IRAMAT), Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Montaigne-Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Montaigne-Université de Technologie de Belfort-Montbeliard (UTBM), 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), Géochrononologie Traceurs Archéométrie (GEOTRAC), 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), Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne-Centre National de la Recherche Scientifique (CNRS)-Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne-Centre National de la Recherche Scientifique (CNRS), Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne (UBM)-Centre National de la Recherche Scientifique (CNRS)-Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne (UBM)-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), 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), 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)-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), and Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)

Subjects
010506 paleontology, Neanderthal, Pleistocene, [SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, Stratigraphy, Population, 010502 geochemistry & geophysics, 01 natural sciences, [SHS]Humanities and Social Sciences, Prehistory, Cave, biology.animal, Earth and Planetary Sciences (miscellaneous), Repartition, education, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, education.field_of_study, geography.geographical_feature_category, biology, Geology, Archaeology, Human evolution, Chronology
Abstract

The spatiotemporal repartition of Neanderthal populations throughout the late Middle and early Upper Pleistocene is of great interest for our understanding of human evolution. Establishing a reliable chronology for human-bearing layers from prehistoric sites is thus essential for the study of Neanderthal population dynamics prior to modern human arrival in Europe. Cova Negra (Valencia, Spain) is one of the richest sites documenting Neanderthal fossil bones in the Iberian Peninsula (Arsuaga et al., 1989, 2007; Villaverde et al., 2014). The stratigraphic sequence includes 15 Middle Palaeolithic layers. Among them, four were dated by the ESR/U-series dating method on enamel from six herbivore fossil teeth. Equivalent doses were obtained using the additive dose method on multi-aliquots. U-content, 234U/238U and 230Th/234U isotopic ratios were measured using ICP-QMS. Results indicate that dental tissues from two out of six analysed teeth underwent U leaching during burial. Thus, it does not allow the calculation of US-ESR (U-series-ESR, Grun et al., 1988) ages for these samples. However, ages calculated using AU model (Accelerating Uptake, Shao et al., 2012) are discussed together with biochronological data and previous absolute ages obtained for the archaeological sequence. Age results indicate that Neanderthals occupied Cova Negra during MIS 8 to 6, between 273 ± 26 ka and 146 ± 34 ka. These results suggest that human occupation took place at the end of the Middle Pleistocene, and hence it is older than proposed by previous TL ages obtained on sediments (Arsuaga et al., 2007). By contrast, our ESR/U-Th ages suggest that Neanderthals were present in the cave 100 ka earlier than initially proposed, in agreement with TL ages obtained on burnt flint (Villaverde et al., 2014). This implies that the Cova Negra human specimens could represent one the earliest occurrences of Neanderthal presence in the Iberian Peninsula.

Published
2019
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