Periglacial landforms in the central French Pyrenees: spatial/chronological analyses and promotion

• Main Author: Feuillet, Thierry
• Other Authors: Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), Université de Nantes, Pascal Bertran
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2010
• Subjects: geomorphology; periglacial; permafrost; Pyrénées; géomorphologie; périglaciaire; pergélisol; environnement; géomorphosites; [SHS.GEO]Humanities and Social Sciences/Geography; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; Ice
• Online Access: https://theses.hal.science/tel-00564112; https://theses.hal.science/tel-00564112/document; https://theses.hal.science/tel-00564112/file/THESE.pdf

This thesis of climatic geomorphology aims to characterize the past and present periglacial stage in the Western part of the central French Pyrenees. It is based on the relationships between the regional climatic characteristics (freezing/thawing cycles in the ambient air and in the ground, quantity and rhythm of snow precipitations) and geomorphic consequences of this climate (patterned grounds, solifluction landforms, permafrost landforms). Thus, the first part focuses on the climate and on the altitudinal definition of the landforms under consideration. It reveals that regional periglacial landforms are staging in a large belt between 1 900 and 3 200 m a.s.l., in which mean annual air temperatures vary between 5°C and -3°C. freezing/thawing cycles fluctuate between 60 and 130 per year and our numerical modelling indicates that the ground freezing can exceed one meter in depth whatever elevation during snow-free time. The second part deals with spatial and paleoenvironmental variability of the periglacial level. In a first step, it is shown on the basis of multivariate analyses that the landforms staging vary on each slope according to local parameters (exposure, lithology, moisture, vegetal cover). Recently deglaciated areas are the most favourable to the development of forms because of the fine-rich deposits occurrence and high moisture. In a second step, the analysis focuses on the evolution of the periglacial landscapes since the Lateglacial. The observations of inherited landforms and radiocarbon dating show some favourable phases to periglacial dynamics (Younger Dryas, mid-Holocene, Little Ice Age). Finally, the third part describes activities dedicated to the promotion and diffusion of these results in the Pyrenees national park. For that, we evaluated 30 geomorphosites of the periglacial belt. Didactic panels and a web site were created to propose to the public at large easy to read presentations of the most remarkable geomorphosites. Cette thèse de géomorphologie climatique a pour objectif de ...