Geomorphological and Tectonic Evolution of the central English Channel: Insights from High-Resolution Marine Geophysical Data

The Cotentin Peninsula (CP), located in north-western France, represents the northern extension of the North Armorican Domain (NAD), which forms a structural rim in the central Channel. The NAD, including the Cotentin and the Channel Islands, has been shaped by major geodynamic processes such as the Icartian (~2 Ga), Cadomian (~580 Ma), and Hercynian (~300 Ma) orogenies. Subsequently, the development of Meso-Cenozoic sedimentary basins, although modest in extent and thickness, further influenced the area. The NAD, in particular, experienced differential evolution due to extensive Meso-Cenozoic sedimentation, and successive Cenozoic tectonic inversions associated with the Alpine orogeny. The area is also characterized by the evolution of the Channel River and its associated troughs.

 

The English Channel reflects complex interactions between tectonics and surface processes. Moderate and diffuse seismic activity, including historical earthquakes near Jersey, highlights the region’s ongoing deformation (e.g. Beucler et al., 2021). The strongest tidal currents in Europe takes place in the Alderney Race, between Alderney and the CP. They greatly participate in shaping the morphology of the submarine floor (Furgerot et al., 2019).

 

While onshore fault-controlled Meso-Cenozoic sedimentary basins are well-studied, their offshore counterparts remain less understood, despite geological mapping efforts in the 1970’s. Recent high-resolution multibeam bathymetric data and seismic reflection surveys (EMECHAT1 in 2022 and EMECHAT2 in 2024) have provided new insights into the submarine structural framework, especially around the Cap de la Hague and in the central English Channel. These studies have identified major faults, including the La Hague Offshore Fault (LHOF) and the La Hague Deep Faults (LHDF1 and LHDF2), and refined the location of sedimentary basins (Kaci et al, 2024).

 

The seismic profiles offer crucial information about the geometry of geological layers, seismic facies, and apparent thickness, as well as fault characteristics such as alignment, dip, and displacement. These data also reveal the interactions between tectonics and sedimentation in the central Channel, highlighting the evolution of the Channel River system. Additionally, the 51 rock cores collected during EMECHAT2 will establish a stratigraphic framework for dating seabed units and understanding associated geological events.

 

The project aims to explain the differential post-Hercynian evolution of the northern and southern compartments by producing a marine geological map off the north-western Cotentin, extending onshore data, and analyzing the interactions between faults, sedimentary basins, and troughs (especially the Hurd Deep and the La Hague Trough). A final goal is to pinpoint ongoing deformation to confirm or refute the presence of active faults in this area and to correlate them with historical and instrumental seismic activity.

 

This work, part of a thesis on Channel troughs funded by UBO and ASNR (ex IRSN), contributes to understanding the geomorphological and tectonic dynamics at the land-sea interface in this key region.