Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

M E T H O D The geology of the Cotentin Peninsula is well known through mapping and drilling data. There is a strong structural heritage ranging from the Icartian (Early Proterozoic) orogen to the Cadomian (Late Proterozoic) and Variscan (Late Paleozoic) terranes, on which Mesozoic to Cenozoic brittle tectonics is superimposed. In the onshore domain, several basins are limited by faults, and develop after the Eocene during the Neogene, in the central zone of the Peninsula (SM) (Baize, 1998; Dugué et al., 2007), while poorly characterized deformations appear to control the landscape development (Lagarde et al., 2000; Pedoja et al., 2018). However, and despite the important stakes, the geology of the offshore part bounding the nuclear sites’ coast was not known on a better scale than the 1/1,000,000 until the last years. Recently, we have begun to fill this knowledge gap by compiling and acquiring bathymetric data, and by performing geophysical profiles in the Channel and especially around the La Hague Cape and the Channel Islands. The first allow to differentiate and map geological units, because the bedrock is devoid of Holocene sediment. The seconds provide in-depth imagery of the mapped geological units, their geometric relationships, and particularly their tectonic deformation. The next crucial step will be to take in- situ samples from the geological formations identified in seismics, to complete the catalogue available today. Fig. 1: Location of major features cited in this contribution. HD: Hurd Deep; LH: La Hague Deep; CP: Cotentin Peninsula; SM: Sainteny- Marchésieux basin ; E : Ecréhous basin.