Divergent Mediterranean seawater circulation during Holocene sapropel formation – Reconstructed using Nd isotopes in fish debris and foraminifera

Autor: Philipp Böning, Gert J. de Lange, Katharina Pahnke, Li Wu, Jiawang Wu, Annie Michard
Přispěvatelé: Tongji University, Utrecht University [Utrecht], Carl Von Ossietzky Universität Oldenburg, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), 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), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Geochemistry, General geochemistry, Carl Von Ossietzky Universität Oldenburg = Carl von Ossietzky University of Oldenburg (OFFIS), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-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)
Jazyk: angličtina
Rok vydání: 2019
Předmět:
Zdroj: Earth and Planetary Science Letters
Earth and Planetary Science Letters, Elsevier, 2019, 511, pp.141-153. ⟨10.1016/j.epsl.2019.01.036⟩
Earth and Planetary Science Letters, 511, 141. Elsevier
Earth and Planetary Science Letters, 2019, 511, pp.141-153. ⟨10.1016/j.epsl.2019.01.036⟩
ISSN: 0012-821X
DOI: 10.1016/j.epsl.2019.01.036⟩
Popis: The recurrent deposition of organic-rich sapropel layers in the eastern Mediterranean Sea (EMS) has been attributed to deep-water stagnation and enhanced biological production. However, the underlying climatic interactions, paleoceanographic processes, and associated ventilation dynamics are still debated. Here, we present a basin-wide reconstruction of circulation systematics during sapropel S1 formation (∼10.8–6.1 kyr BP), using the Nd isotope composition ( e Nd ) as paleo-seawater tracer. Our e Nd data from fish debris and foraminifera tests are remarkably radiogenic compared to today, and spatially and temporally constant. These results predominantly reflect enhanced Nile versus Atlantic contributions, and indicate that EMS deep-water stagnation prevailed below ∼800 m water-depth during S1 formation. Additional e Nd records obtained from bulk sediment leachates show that such stagnation was preconditioned thousand(s) of years prior to S1 initiation by intensified Nile flooding, whereas it terminated with a basin-wide, deep-water renewal. In addition, decoupling of deep waters between the EMS and western Mediterranean Sea (WMS) is evident for the S1-period. Using a box-model for Nd in the EMS, the observed e Nd distribution can be most adequately explained by a 2-fold increase in Nile discharge, and a 50% decrease in the EMS–WMS exchange that was mostly limited to the surface waters alone. The corresponding circulation during S1 was more sluggish and shallow for the EMS, but largely unaffected for the WMS. This implies that deep-water stagnation is a prerequisite for sapropel formation.
Databáze: OpenAIRE
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