Structure of the Mesozoic sedimentary cover of the North Aquitaine continental shelf – New results from offshore and onshore observations in the Charente region (France).
Résumé
The North Aquitaine continental shelf is a key sector to understand the deformation of this shelf related to the rifting events of the Bay of Biscay and the orogenic Pyrenean phases that may help to understand the role of the inheritance on present day structures.
We propose a new analysis of the onshore-offshore tectonic structure of the Charente Region and the North Aquitaine shelf1 based on i) aerial photographies and field measurements along the coast of the Oleron and Ré Islands and the Charente River area, and ii) a newly acquired very high resolution offshore seismic survey2. Offshore we confirm the presence of a large Mesozoic synclinal with an NW-SE axis dipping to the SE and of NE-SW lineaments segmenting the shelf. The Mesozoic sedimentary cover exhibits faults and folds with major faults showing more than 10m large throws. These faults are mainly oriented EW near the coast and NW-SE further off- shore. The same directions of faults were also observed in the Cenozoic formations of the South Brittany shelf. Onshore, the analysis of field measurements and aerial photographies show the extensive occurrence of normal faults oriented in an EW direction and strike slip faults oriented in NW-SE and NE-SW directions associated with folds.
This preliminary structural study provides information on the distribution of structures, style and timing of deformations in the Charentes area induced both by the Biscay rifting, with creation of extensive structures, and/or the orogenic Pyrenean phase that is certainly associated with strike-slip displacement.