The structural evolution of the English Channel area

Abstract

International audienceThe structural evolution of the English Channel area is controlled by structure and particularly by the pre-existing Cadomian and Variscan crustal discontinuities, which have been reactivated repeatedly in post-Variscan times. They controlled the crustal subsidence that produced basin development in the Mesozoic, prior to the sea-floor spreading in the North Atlantic region. They were then reactivated during the Cenozoic compression and basin inversion. The English Channel development is ascribed to mid-Tertiary differential uplift (Oligocene to Miocene). During late Tertiary to Quaternary times the Channel displays characteristics of a tectonically controlled fluvial basin periodically invaded by the sea. At the lithospheric scale, the Channel can be considered as an active intraplate area influenced by the NW–SE ‘Alpine push', the NW–SE ‘Atlantic ridge push' and glacial rebound stresses

DEM and GIS analysis of the stream gradient index to evaluate effects of tectonics: The Normandy intraplate area (NW France)

“…However one can note that (i) the present-day seismicity is not randomly distributed but located over NW-and ENE-trending seismic lineaments (Amorèse et al, 1999;Lagarde et al, 2003), ( Fig. 2A) and (ii) there is a close correspondence among seismic lineaments, pre-existing fault zones and major landform discontinuities marked by linear scarps ranging from steep slopes to cliffs (Fig.…”

“…It has been tectonically active throughout the Plio-Quaternary, as suggested by various tectonic, seismotectonic and geomorphological indicators (Lenô-tre et al, 1999;Lague et al, 2000;Bonnet et al, 2000;Lagarde et al, 2000;Cloetingh et al, 2006). This deformation seems to be the continuation of late Paleogene to Neogene episodes of uplift (Wyns, 1991;Japsen, 1997) and is mainly controlled by structural discontinuities that are parallel to the Cadomian and Variscan faults (Lagarde et al, 2003;Fig. 1).…”

Mapping the human record in the British early Palaeolithic: evidence from the Solent River system

“…By contrast, a drop of at least 30 m would be required in the Dover Strait and a drop of at least 60 m in the English Channel to significantly reduce the sea barriers in these areas. These depths are based on current topography, but due to uplift in the Channel region (estimated at between 30 and 40 m since MIS 11; Lagarde et al, 2003) they actually underestimate past depths and the challenges to colonisation across this area. The contrasting geographies therefore might have led to colonisations during different climatic and environmental phases in the two regions.…”

The Pleistocene rivers of the English Channel region

“…The longitudinal profiles of the bedrock surface beneath each of the alluvial sequences are identified on the basis of their height above the basal contact of the alluvial sequence in the modern valley. The study of the main Pleistocene river systems is completed by a short presentation Auffret et al (1982) and Lericolais (1997); 2, unfilled palaeovalleys (Northern Palaeovalley, according to Auffret et al, 1982); 3, main terrace concentrations (according to Hallegouet and Gibbard, 2003); 4, main faults (according to B. Hallegouet); 5, main faults (according to Lagarde et al, 2003); 6, longitudinal profiles of Figs 4 and 5 coastline: 15 km from the Saint-Brieuc bay (Fig. 1).…”