The proposed "SYRRE" campaign will allow to acquire Very High Resolution (VHR) seismic profiles across the Vendée inner shelf (Southern part of Armorican shelf, North Biscay Margin). This project is a continuation of studies carried out since 2005 by BRGM and CNRS Géosciences Rennes, as well as work carried out on the South Brittany shelf (1:250,000 scale geological map of France (Lorient sheet) edited by BRGM and CARTOMAR/CNRS Rennes) in collaboration with numerous laboratories (Univ. /CNRS Rennes, UBS, IUEM,IFREMER, Univ. Caen et Orléans, MNHN, SHOM, BRGM). The proposed "SYRRE" campaign is part of BRGM's RGF "continental shelf" research and mapping project.

While the south Brittany inner continental shelf is relatively well known thanks to the work already carried out, the Vendée shelf is less well documented. Since 2005, one of the projects has been the production of a 1:250,000-scale geological map (Vendée sheet). For this purpose, HR seismic profiles were acquired during two campaigns carried out in 2005 (GEOVEND) and 2006 (GEOVEND06) on the INSU N/O by CNRS Rennes and BRGM. The interpretations were used to draw up a preliminary distribution map of seismic facies and geological formations (Huerta et al., 2008). One of the results of this study was to highlight the inconsistency of some geological contours with those drawn on the 1:1,000,000 French geological map.

The aim of the "SYRRE" campaign is to expand the network of available seismic profiles by acquiring VHR reflection seismic profiles to improve our knowledge of tectonic structures, the Hercynian basement, pre-Quaternary sedimentary cover, recent loose sediments and Quaternary incisions. The densification of the seismic network will enable us to propose a structural pattern around Yeu Island and Rochebonne High as far as Ré and Oléron Islands, and to determine the distribution of structures, the style and timing of deformation. Is the structural pattern of the Vendean shelf in continuity with that the tectonic pattern of South-Brittany shelf (Lorient sheet)? how does it correlate with major faults observed on land? An updated of structural pattern  is also of interest for questions concerning the structural inheritance/reactivation of Variscan structures and the origin of basement highs (Yeu, Rochebonne) and Tertiary carbonate plateaus (south of Noirmoutier).

The seismic reflection data (Sparker Very High Resolution monotrace) from the "SYRRE" campaign will enable us to specify :

• the limits of extension of the Tertiary and Mesozoic formatrions, in order to remove cartographic inconsistencies between the 1:1,000,000 scale geological map (Chantraine et al., 2003) and that proposed by Huerta et al. (2010). A recent review ("GEOPAL-littoral" project 2011-2013) highlighted areas of data lack or with nconsistencies for both Mesozoic and Tertiary series;
• the distribution of preserved thicknesses;
• the geometries of major surfaces and Meso-Cenozoic deposits to determine progradation directions, and deduce areas of subsidence;
• the evolution of paleogeography in relation to the rifting of the Bay of Biscay and the Pyrenean-Alpine orogens

The SYRRE THR profiles will also enable us to look at recent deposits and improve the mapping of coastal basins, their sedimentary filling and the network of Quaternary palaeo-valleys (extension of the Loire network towards the Ile d'Yeu? Extension of the Charentes incision network to the shelf?).

From a regional point of view, this knowledge will provide a global view of the structuration of the North Biscay continental shelf , as well as a vision of its paleogeographic evolution.