Hydrogeophysics of permafrost mounds and thermokarst ponds in northern Quebec and Nouvelle-Aquitaine : a contribution to the understanding of the paleorecharge of large aquifers using a field analogue

• Main Author: Bussière, Lea
• Other Authors: Géoressources et environnement, Institut Polytechnique de Bordeaux (Bordeaux INP)-Université Bordeaux Montaigne (UBM), Université Michel de Montaigne - Bordeaux III, Université Laval (Québec, Canada), Alain Dupuy, Richard Fortier, Myriam Schmutz
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2022
• Subjects: Ponds; Thermokarst; Permafrost; Tomography; DC electrical resistivity; Spectral induced polarization; Ground penetrating radar; Electromagnetic induction; Modeling; Aquitaine; Nunavik; Cryptokarst; Mares; Pergélisol; Tomographie; Résistivité électrique en courant continu; Polarisation provoquée spectrale; Géoradar; Induction électromagnétique; Modélisation; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Canada; permafrost; pergélisol
• Online Access: https://theses.hal.science/tel-04016842; https://theses.hal.science/tel-04016842/document; https://theses.hal.science/tel-04016842/file/These_Lea_BUSSIERE.pdf

This Ph.D thesis aims at enhencing our understanding of the connection between surface water and groundwater in south-west France, by questionning the possible aggradation of permafrost in the Triangle landais area during the Last Glacial Maximum (LGM),and its consequences on groundwater recharge. Such a permafrost event has been proposedfor two reasons. On the one hand, it could offer an explanation to the low recharge of theCretaceous aquifer at the time of the LGM, and to its subsequent high recharge at the endof this period. On the other hand, it could explain the inset of the numerous ponds dottingthis territory. This assumption is examined by means of a comparative study conductedon a watershed in the discontinuous permafrost zone in Nunavik (Québec, Canada). Theresearch is structured in two steps: firstly by verifying whether the numerous ponds havetypical thermokarst characteristics, and secondly, by quantifying the consequences of thepresumed paleo-permafrost on groundwater recharge.From the available hydrogeological and geomorphological data, most of the pondsappear to originate from karstic or aeolian processes. However, the permafrost hypothesiscannot be rejected and seems to be the best explanation for a minority of ponds. Moreprecisely, these ponds may correspond to thermokarst ponds resulting from the thawsettlement of the ground in a sporadic or discontinuous permafrost environment, butcertainly not in a continuous one.Geophysical data (ground penetrating radar, DC electrical resistivity, and spectralinduced polarization) have been used to build two conceptual stratigraphic models: oneof a pond from the area of Villagrains-Landiras (SW France) and one of a thermokarstpond from Nunavik. For further comparison, stratigraphic sections and bathymetric mapswere also produced on other ponds. As a result, the ponds from the Triangle landais andthe thermokarst ponds seem closely related in terms of morphology, geological context andfrost susceptibility of the ground. Solifluction and creeping features ...