Variations in eastern Mediterranean hydrology during the last climatic cycle as inferred from neodymium isotopes in foraminifera

QUATERNARY SCIENCE REVIEWS

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Article

Duhamel, Maxence¹  Colin, Christophe¹  Revel, Marie²  Siani, Giuseppe¹  Dapoigny, Arnaud³  Douville, Eric³  Wu, Jiawang⁴  Zhao, Yulong⁴  Liu, Zhifei⁴  Montagna, Paolo⁵ 

[1] Univ Paris Saclay, GEOPS, CNRS, F-91405 Orsay, France

[2] Univ Cote dAzur, Geoazur, OCA, CNRS,IRD, 250 Rue Albert Einstein, F-06500 Valbonne, France

[3] Univ Paris Saclay, Lab Sci Climat & Environm, LSCE, CEA,CNRS,UVSQ,IPSL, F-91191 Gif Sur Yvette, France

[4] Tongji Univ, State Key Lab Marine Geol, Shanghai 200092, Peoples R China

[5] CNR, ISP, Via Gobetti 101, I-40129 Bologna, Italy

关键词: Neodymium isotopes;    Foraminifera;    Paleo-hydrology;    Sapropels;    Eastern Mediterranean sea;    African monsoon;   

DOI  :  10.1016/j.quascirev.2020.106306

来源: Elsevier

【 摘 要 】

The Nd isotopic compositions (epsilon Nd) of mixed planktonic foraminifera have been analyzed in two sediment cores collected in the Nile deep-sea fan in order to reconstruct past epsilon Nd of the Eastern Mediterranean Deep Water (EMDW) and to assess the relative contributions of Nile discharge and Modified Atlantic Water (MAW) inflow to the Eastern Mediterranean Sea hydrology, as well as their potential control on anoxic events over the last climatic cycle. The two foraminiferal epsilon Nd records are similar and display an increase in epsilon Nd values during the African Humid Periods. Superimposed on this precession-forced variability (insolation received by the Earth at low latitudes), the record of variations in foraminiferal epsilon Nd indicates a 2-unit decrease in epsilon Nd during the interglacial Marine Isotope Stages (MIS) 5 and 1 compared to glacial MIS6, 4, 3 and 2. The epsilon Nd results suggest that the long-term glacial to interglacial changes in Nd isotopic composition of EMDW were not entirely induced by variations in Nile River discharge and Saharan dust inputs. Decreases in epsilon Nd during MIS5 and MIS1 interglacials indicate an increase in the contribution of unradiogenic MAW to the eastern Mediterranean Sea related to high sealevel stands and greater seawater exchange between the North Atlantic and Mediterranean basins. In addition, radiogenic seawater epsilon Nd values observed during African Humid Periods (and sapropel events) are associated with an intensification of Nile discharge and an increase in residence time of deep-water masses in the eastern Mediterranean Sea, which induces an increase in the interaction between deepwater masses and radiogenic sediments along the margin of the eastern Mediterranean Sea. Results confirm that an intensification of the hydrological exchanges between the western and eastern Mediterranean basins during high sea-level stand and the subsequent higher proportion of Atlantic Water in the Levantine Basin may have preconditioned the eastern Mediterranean Sea to sapropel depositions during the last climatic cycle. (C) 2020 Elsevier Ltd. All rights reserved.

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