Stratigraphie, dynamique fluvio‑éolienne et héritages du pléniglaciaire supérieur weichselien dans les basses plaines du bassin français de l’Escaut (nord de la France)

• Published in: Quaternaire
• Main Author: Deschodt, Laurent
• Format: Article in Journal/Newspaper
• Language: French
• Published: Association française pour l’étude du quaternaire 2020
• Subjects: Escaut; Lys; Deûle; Marque; Scarpe; Pléniglaciaire supérieur weichselien; Tardiglaciaire weichselien; dépôt éolien; dépôt fluvio-éolien; loess; modelés fluviaux; dune; dépressions thermokarstiques; Scheldt River; Leie River; Deûle River; Marque River; Scarpe River; Weichselian Upper Pleniglacial; Weichselian Lateglacial; aeolian deposit; fluvio-aeolian deposit; fluvial landforms; thermokarst depressions; geo; Thermokarst
• Online Access: http://journals.openedition.org/quaternaire/12444

The French upstream catchment of the Scheldt River is divided into a high country and a low country. The low country is part of the northwest European Loess Belt and is characterised by large plains and minor streams. This configuration allowed for the deposition of original sedimentary records during the Weichselian Upper Pleniglacial. A strong and extensive fluvial activity occured during the Pleniglacial in valley floors. Around 22 ka, the river system retracted and the valleys were filled with loess. The sandy alluvial deposits (S) present on all the valley floors then passed to predominantly silty formations (L): loess or loess reworked by runoff (fluvio-aeolian facies). While flows disappeared on the slopes and in the upstream terminations of basins, they continued in channels further downstream. Small dunes (sand or alternation of sand and loess) developed locally near hydrographic axes and on larger surfaces in the Scarp River plain. The (S) and (L) formations are correlated to the Older Cover Sand 1 of the northern sandy area. The occurrence of thermokarst depressions is suspected in the Scarpe Plain at the end of the Upper Pleniglacial. At the end of the Pleniglacial, linear or meandering channels were present in the upstream basins. Downstream, an active band, possibly braided, was incised in the loessic plains. During the return to temperate conditions, some inherited channels were simply flooded. Le bassin français amont de l’Escaut se divise en un haut pays et un bas pays. Le bas pays est composé de plaines larges avec de petits cours d’eau. Il est situé dans la zone loessique du nord-ouest européen. Cette configuration a permis des enregistrements sédimentaires originaux durant le Pléniglaciaire supérieur weichselien. Une forte activité fluviatile extensive intervient dans les fonds de vallée. Vers 22 ka, le réseau hydrographique se rétracte et les fonds de vallées sont envahis par le loess. Les dépôts alluviaux sableux (S) présents sur la totalité des fonds de vallées passent alors à des ...