Enregistrement Holocène dans le Sud-Est du Golfe de Gascogne. Signaux climatiques globaux et régionaux

• Main Author: Garcia, Jennifer
• Other Authors: Bio-Indicateurs Actuels et Fossiles (BIAF), Université d'Angers (UA), Université d'Angers, Hélène Howa
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2013
• Subjects: Paleoclimate; Bay of Biscay; Planktic Foraminifera; Benthic Foraminifera; Navidad current; Stable isotopes; Carbon; Oxygen; Paléoclimat; Holocène; Golfe de Gascogne; Foraminifères planctoniques; Foraminifères benthiques; courant Navidad; NAO; Isotopes stables du carbone; Isotopes stables de l'oxygène; [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology; Navidad; North Atlantic; North Atlantic oscillation
• Online Access: https://tel.archives-ouvertes.fr/tel-01067832; https://tel.archives-ouvertes.fr/tel-01067832/document; https://tel.archives-ouvertes.fr/tel-01067832/file/these_J_GARCIA.pdf

This work aims to improve the use of biological tracers (or proxies) to reconstruct past hydrological changes in the Bay of Biscay (B of B) over the Holocene. The study of sedimentary archives from the southeastern (SE) B of B demonstrated that this environment, which is marginal from the general ocean thermohaline circulation and under the direct influence of the North Atlantic Oscillation (NAO), records global as well as regional Holocene climatic variability. In this context, short sedimentary cores (1 to 3m long) were retrieved from four stations located along a NWSE bathymetric gradient in the SE B of B. Sedimentary characteristics, planktic (PF) and benthic (BF) foraminiferal assemblages, coccolith assemblages, oxygen and carbon isotopic ratios of the foraminiferal shells, as well as size measurements were investigated every 0.5 to 10 cm. From 13 000 cal yrs BP to modern ages, B of B has encountered a succession of environnemental perturbations in response to global forcing factors (insolation, atmospheric and oceanic circulations). Planktic fauna constitute good proxies of temperature and water column stratification characteristics, forced by short-, mid- and long- term insolation changes, allowing the distinction of high summer temperature periods or periods of intense primary production (PP; spring blooms). The occurrence of species typical of subtropical environments suggests long-term incursions of the warm and saline water Navidad Current from the Iberian margin, reaching the SE corner of the B of B. These incursions are nowadays observed during negative NAO conditions. Along with the holocene rising sea-level until ~8 000 cal yrs BP, strong continental influence affects benthic environments characterized by intense sediment transports. From 8 000 cal yrs BP, benthic fauna responds mainly to PP and occasionally to lateral transport of organic matter by fluvial plumes. This study allows also the correlation of the near continent climatic events to environmental perturbations observed locally in this ...