Reconstitution des paléoenvironnements côtiers bretons à l’Holocène : interactions entre dynamiques sédimentaires, climatiques et anthropiques
The objective of Ophélie David's thesis is to compare the climatic and anthropogenic histories of the region of Southern Brittany (Morbihan to the Baie de Vilaine) to that of Northern Brittany (Baie de Morlaix and Plouescat), then to integrate the studies carried out in recent years in Rade de Brest, Southern Brittany and on the Grande Vasière, in order to establish the most complete possible historical framework of Holocene paleoenvironmental dynamics on the scale of Brittany. In this context, this project implements different specialties (paleoclimatology, coastal and littoral paleoenvironments, dynamics of human occupation in collaboration with archaeologists and historians) applied to the coastline of Brittany from the Neolithic period to the present day by relying on the skills currently available within the LGO between UBO and UBS on marine (benthic foraminifera, dinoflagellate cysts) and continental (pollen grains and other non-pollen microrests) markers. Marine markers provide information on planktonic productivity related to nutrient export, water stratification, oxygenation conditions, while pollen grains allow the characterization of watersheds and vegetation dynamics and the discussion of paleo-landscape dynamics (pollination, transport and preservation). These different markers are profoundly linked to climatic variations whose forcings on our coasts are both oceanic and atmospheric (natural daily to multi-decadal oscillations such as the NAO), to which are added over the long term variations in insolation (associated with variations in the Earth's orbital parameters and modifying seasonality) and solar activity, as well as large-scale oceanic circulation on millennial scales (AMOC).