Electrical, pedological and geotechnical characterisation of micro-reliefs (“mottureaux”) of the Poiré-sur-Velluire marsh (France)

A survey of electrical, pedological and geotechnical measurements was carried out on the Marais du Poiré-sur-Velluire site (Marais Poitevin, France) in 2021 and 2022 to characterise micro-reliefs (often named “mottureaux” or “gilgais”), which are home to a rich biodiversity. The electrical measurements consisted in Electrical Resistivity Tomography at various investigation depths. The summary of the results presented in this paper highlights the following two elements, which may play a definite role in the genesis of these very special micro-reliefs: (a) desiccation cracks and (b) the thickness of a very soft, plastic-to-liquid clay layer in the saturated part of the soil.