Spatial Variability of Modern Incised Valleys on the French Atlantic Coast: Comparison between the Charente and the Lay–Sèvre Incised Valleys

Climate control on late Holocene high-energy sedimentation along coasts of the northeastern Atlantic Ocean

“…The Pertuis Charentais area was chosen because it has received much attention over recent decades, with abundant stratigraphical, sedimentological and geochronological data (Allard et al, 2008(Allard et al, , 2010Bertin et al, 2008;Bertin and Chaumillon, 2006;Billeaud et al, 2005;Chaumillon et al, 2008Chaumillon et al, , 2004Chaumillon and Weber, 2006;Poirier et al, 2011;Weber et al, 2004a,b). Previous studies have demonstrated the vulnerability of the Pertuis Charentais to storm events (Baumann et al, 2017a,b;Breilh et al, 2014), and its ability to record climate changes of the past centuries to decades (Allard et al, 2008;Poirier et al, 2011Poirier et al, , 2017.…”

“…Differential erosion of Mesozoic to Cenozoic loose marls and sandstones in synclines during the Pleistocene contributed to the formation of NW-SE incised valleys, which provided a large accommodation space for deposition of Holocene marine and continental sediments ( Fig. 1B; Chaumillon et al, 2008;Chaumillon and Weber, 2006;Weber et al, 2004a,b).…”

“…• The Pertuis Breton (260 km 2 ) and Poitevin marsh (980 km 2 ), which correspond to the paleo-valleys of the Sèvre Niortaise, Vendée and Lay rivers (Chaumillon and Weber, 2006;Weber et al, 2004a), • The Pertuis d'Antioche (450 km 2 ) and Rochefort marsh (240 km 2 ), which correspond to the paleo-valley of the Charente River (Chaumillon and Weber, 2006;Weber et al, 2004b), • The Pertuis de Maumusson and Arvert marsh (170 km 2 ), which correspond to the paleo-valley of the Seudre river . The Pertuis de Maumusson, unlike the two former bounded by rocky shores, is a 1.5 km wide sedimentary tidal inlet .…”

“…Internal architecture, sedimentology and timing of deposition of the Holocene sediment infilling of the outer marine Pertuis Charentais have been extensively investigated with very highresolution seismic surveys ground-truthed by sedimentary cores and 14 C dating Chaumillon and Weber, 2006;Weber et al, 2004a,b), with particular emphasis on the MarennesOléron Bay (Allard et al, 2010;Billeaud et al, 2005;Poirier et al, 2011). Inland, Holocene sediment infilling of the coastal marshes has been described from sedimentary cores, with a focus on the record of relative sea-level changes in the Poitevin Marsh Gruet and Sauriau, 1994;Sauriau and Gruet, 1988;Visset, 1987;Visset et al, 1990).…”

“…At the millennial scale, sediment infilling of the incised valleys was dominantly coarse-grained (Chaumillon and Weber, 2006). Stratigraphy was primarily controlled by rapid sea-level rise during the early Holocene (ca.…”