EPOC
UMR CNRS 5805 EPOC
Environnements et Paléoenvironnements
Océaniques et Continentaux
Université de Bordeaux  CNRS  Bordeaux-INP  EPHE  OASU

Version Française
HomeNewsJobsAccessLinksSite Map
 
> News > Informations
Consignes de Sécurité et Numéros d'Urgence
(à l'usage des personnels du laboratoire)
Séminaire


A highly productive Subarctic Atlantic during the Last Interglacial and the role of diatoms

Date
March 19, 2010  10:45 am

Intervenant(s)
Oscar E. ROMERO, Inst. Of Earth Sciences of Andalucia (IACT-CSIC), Facultad de Ciencias, Universidad de Granada, Spain

Résumé
This presentation offers results on the paleoceanographic reconstruction for the last interglacial (LIG) period based on sediments from Site U1304 cored in the Subarctic Atlantic during IODP Expedition 303. Site U1304 (~53°N, 33'W) represents a high-resolution, high-sedimentation record of Pleistocene environmental change at a sensitive location close to the Subarctic Convergence between the surface Labrador Current and the North Atlantic Current. A key characteristic of Site U1304 sediments is the recurring occurrence of laminated, diatom-rich sequences, dominated by the needle-shaped Thalassiothrix longissima. Although most marine laminated sediments are located close to continental margins, a few, like those at Site 1304, are exceptionally formed at oceanic frontal systems in pelagic waters.
The LIG, corresponding to Marine Isotope Stage (MIS) 5e, is commonly used for comparison to the Holocene providing a reference of interglacial climate variability in the absence of anthropogenic forcing. Using an expanded section of the LIG recovered at Site U1304, we demonstrate that early MIS 5e offered sufficient hydrographic and nutrient conditions for high diatom production and accumulation. The appearance of laminated diatom oozes in the sediment sequence ~3 ka after the beginning of MIS 5e at ~125 ka BP coincides with a shift to higher diatom silicon (δ30Sidiat) values, indicative of increased nutrient availability and silicic acid utilization in surface waters transported northwards by Southern Ocean-originated waters. We argue that the hydrography of surface waters alone does not guarantee significant siliceous productivity and the formation of diatom-rich sediments, but that the additional presence of an increased silicic acid/nutrient pool played a decisive role in strengthening diatom production, the biological pump and so CO2 drawdown in the Subarctic Atlantic during the LIG.
UMR CNRS 5805 EPOC - OASU - Université de Bordeaux
Allée Geoffroy Saint-Hilaire - CS 50023 - 33615 PESSAC CEDEX - FRANCE

| Last update : 18 December 2023 | Contact | Legal Disclaimer | © 2006-2024 EPOC |