International audienceThe prediction of landslide movement acceleration is a complex problem, among others identified for deep-seated landslides, and represents a crucial step for risk assessment. Within the scope of this problem, the objective of this paper is to explore a modelling method that enables the study of landslide function and facilitates displacement predictions based on a limited data set. An inverse modelling approach is proposed for predicting the temporal evolution of landslide movement based on rainfall and displacement velocities. Initially, the hydrogeology of the studied landslides was conceptualised based on correlative analyses. Subsequently, we applied an inverse model with a Gaussian-exponential transfer function to reproduce the displacements. This method was tested on the Grand Ilet (GI) and Mare-à-Poule-d'Eau (HB) landslides on Reunion Island in the Indian Ocean. We show that the behaviour of landslides can be modelled by inverse models with a bimodal transfer function using a Gaussian-exponential impulse response. The cumulative displacements over 7 years of modelling (2 years of calibration period for GI, and 4 years for HB) were reproduced with an RMSE above 0.9. The characteristics of the bimodal transfer function are directly related to the hydrogeological functioning demonstrated by the correlative analyses: the rapid reaction of a landslide can be associated with the effect of a preferential flow path on groundwater level variations. Thus, this study shows that the inverse model using a Gaussian-exponential transfer function is a powerful tool for predicting deep-seated landslide movements and for studying how they function. Beyond modelling displacements, our approach effectively demonstrates its ability to contribute relevant data for conceptualising the sliding mechanisms and hydrogeology of landslides

International audienceWe present a high-resolution conceptual hydrogeological model for complex basaltic volcanic islands based on Mayotte Island in the Comoros. Its geological structure and hydrogeological functioning are deduced from a large dataset: geological mapping, geophysics, some forty new boreholes, piezometric data, hydraulic conductivity, hydrochemical data, etc. We describe previously unknown deep cut-and-fill palaeovalleys. The resulting conceptual geological and hydrogeological model of the island is very different from the Hawaiian model, in that it lacks a low-elevation basal aquifer and dyke-impounded high-level aquifers. It is closer to the Canary Islands model, which has, however, not yet been described at a high-resolution scale. It does not have a continuous aquifer, but rather a discontinuous succession of perched aquifers separated by aquicludes and aquitards. This results more from the complex geological structure of the island, which has experienced several phases of volcanism, erosion and weathering, than from its age, but is also a result of the high-resolution scale of the model. High-resolution conceptual modelling is now necessary to solve problems of applied geology and hydrogeology

No abstract

No abstract

Le gisement karstique de Blanquatère 1 a livré une microfaune d'âge Miocène moyen, abondante (plus de 6300 dents) et très diversifi ée en rongeurs avec 33 espèces reconnues, parmi lesquelles plusieurs espèces nouvelles de Cricetidae et de Gliridae. Le présent travail complète l'étude initiale par la description de Cricetidae non décrits jusqu'ici, Eumyarion, Democricetodon, Pseudo fahlbuschia, des Eomyidae Ligerimys et Keramidomys et des Sciuridae Spermophilinus et Heteroxerus. Cette faune, très riche, fait de cette localité une référence pour le début du Miocène moyen (MN 4/MN 5) en Europe sud-occidentale. La faune inclut des taxons nouveaux et allochtones avec, en particulier, la présence d'un représentant des Myocricetodontinae (Dakkamys sp.), qui résulte d'une probable