Headwater valley response to climate and land use changes during theLittle Ice Age in the Massif Central (Yzeron basin, France)

• Published in: Geomorphology
• Main Authors: Delile, Hugo, Schmitt, Laurent, Jacob-Rousseau, Nicolas, Grosprêtre, Loïc, Privolt, Grégoire, Preusser, Frank
• Other Authors: University of Southampton, ARCHEORIENT - Environnements et sociétés de l'Orient ancien (Archéorient), Université Lumière - Lyon 2 (UL2)-Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Environnement Ville Société (EVS), École normale supérieure - Lyon (ENS Lyon)-École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom Paris (IMT)-Institut Mines-Télécom Paris (IMT)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet Saint-Étienne (UJM)-École Nationale des Travaux Publics de l'État (ENTPE)-École nationale supérieure d'architecture de Lyon (ENSAL)-Centre National de la Recherche Scientifique (CNRS), University of Freiburg Freiburg
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: Little Ice Age; Headwater valley bottom deposits; Aggradation-incision cycle; OSL and radiocarbon dating; Landscape history; Massif Central; envir; geo; North Atlantic; North Atlantic oscillation
• Online Access: https://doi.org/10.1016/j.geomorph.2016.01.010; https://halshs.archives-ouvertes.fr/halshs-01302648/file/Delile%20et%20al._Geomorphology_2016.pdf; https://halshs.archives-ouvertes.fr/halshs-01302648

International audience The geomorphological response of valley bottoms in eastern France to climatic fluctuations of the Little Ice Age (LIA) was investigated using sedimentological analysis together with optically stimulated luminescence (OSL) and radiocarbon dating. Diachronic mapping of land use since the beginning of the nineteenth century was also carried out. Since A.D. 1500, the valley bottoms experienced three cycles of aggradation and subsequent incision , each characterized by paired periods of high and low detritic activity. While the impact of human activity on the aggradation of the alluvial plain is observed, the vertical dynamics of the valley bottom deposits seemingly were also linked to the hydroclimatic fluctuations during the LIA. The sensitivity to these fluctuations was increased by human activity at the scale of the basin. Variations of the winter North Atlantic Oscillation (NAO) and solar activity from the last five centuries correlate with wet and cold phases during which valley bottoms accumulated , and dry and warm phases during which the streams incised into the valley floors. This fluvial sensitivity to the meteorological conditions induced temporal variations in sedimentary supply originating from either direct input from remnants of periglacial alluvial sheets or local rocky outcrops and/or from indirect input from the erosion of alluvial and colluvial deposits. These two components, combined with the sheet runoff over the ploughlands, express the complex coupling between hillslopes and valley bottoms in the headwater catchments. This caused a cascade-shaped transit of the sediments characterized by alternating phases of storage and removal. Keywords: Little Ice Age Headwater valley bottom deposits Aggradation-incision cycle OSL and radiocarbon dating Landscape history Massif Central