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This article combining geophysics and archaeology aims to provide a more comprehensive characterization of the La Ruchelle valley located in the south of the Celtic site of La Peyrouse (Saint‐Félix‐de‐Villadeix, Dordogne, France) (occupied between the 3rd century BC and the 2nd century AD) through geological prospection (core sampling, geotechnical prospection and mechanical prospection) and near‐surface geophysics (electrical resistivity tomography). On this site, other studies have been carried out since the discovery of the site, such as magnetic prospecting and a hydrogeological study. Geophysical data coupled with geological prospection were used to understand the geology of the valley: (1) The bottom of the valley is filled with colluvium with a thickness of 6 m maximum; (2) part of the colluvium filling characterize by a very low resistivity is indeed archaeological remains; (3) three very distinct geological horizons have been detected—two of these horizons are characteristic of Campanian limestone (C6d and C6e), and the last consists of colluvium with a filling between 2 and 6 m in the centre of the valley, which is particularly thick. This last very thick formation is in fact filled with archaeological and prehistoric remains. [ABSTRACT FROM AUTHOR]

The Chauvet-Pont d'Arc Cave (Ardèche, France), famous for its remarkable rock art, also contains unique thermal-alterations such as rock spalling and color changes on the walls. These alterations resulted from intense fires that have not been observed in the other decorated caves thus far discovered. The functions of these unusual fires challenge archaeologists. To characterize these combustions, we used a numerical tool, previously validated with experimental data, to study the thermo-alterations in the Megaceros Gallery. This unprecedented approach in cave art research enabled us to assess the wood quantities and locations of the hearths responsible for the thermo-alterations. We report here that at least ten fires took place in the Megaceros Gallery while burning more than 170 kg of wood. Both simulation and in situ observations suggest that the branches were arranged in a tepee shape and purposefully positioned, some distance from the walls. This method therefore enables further analysis of the functions of these fires. [ABSTRACT FROM AUTHOR]

Abstract: In France, the monitoring of landfill cover after closure of the site is a local problem, since its tightness must be ensured over time. Leaks in the cover are a problem, as they allow water to infiltrate the stored waste. In order to locate such leaks, electrical resistivity tomography was used on an experimental site in which defects had been intentionally made in the cover. Repeated measurements taken on this site showed that the weather conditions preceding the measurements need to be taken into account, as they affect the water content in the cover material. They also showed that there are optimal weather conditions for detecting defects in the cover. A statistical analysis carried out on the electrical resistivity results for all surveys and cover material samples showed that the material was heterogeneous; this variability was mainly due to a difference in particle size (fines content) and in compaction. This study has shown the capacity of electrical resistivity tomography to detect defects and heterogeneity in the cover material, indicating that it is a good means of monitoring the quality of landfill cover both when it is put in place and subsequently. [Copyright &y& Elsevier]

Because of the great heterogeneity of the limestone fissures, conduits, and reservoirs in karst areas, the understanding of the infiltration in caves and karst terrains is complicated. For example, the time delays observed between rainfall and the various flows into caves, such as shaft flow and seepage flow, exhibit significant variability. To better understand the infiltration above a typical shallow cave, Villars Cave, South-west France, we used both a very long monitoring (>20 years) isotopic data set of rainfall and dripping rates at two different cave gallery levels (14 m and 36 m below the surface, respectively) and a conceptual model (KarstFor) that mix water flows and isotopes. In order to determine the most appropriate reservoir and flow settings, we used one time-lapse electrical resistivity tomography (ERT) image made above the cave, which were incorporated into the KarstFor model. The modeled variations in storage water and infiltration flows are in a good agreement with the observed dripping discharge rates, indicating seasonal variability and various time delays between water excess ((Rainfall-Evapotranspiration) > 0) and drip rates in the different cave levels. The fact that the model strikingly simulates the small, but constant, isotopic difference of drip water δ18O (δ18O d) values between the upper and the lower galleries of Villars Cave, not only reinforces reliability in the model itself but also reveals the impact of multiple infiltration routes and karst reservoir dynamics on the δ18O d. On an inter-annual scale, the observed δ18O d values follow the variations of the water excess and of the cave temperature, which, in the period analyzed, show a marked trend, possibly induced by the climate variability patterns above the cave. Overall, these results are not only important to better understand the infiltration in karstic zones, but also to better interpret speleothem isotopic records widely used in paleo-climate studies. [ABSTRACT FROM AUTHOR]

• The δ18O p (rainfall δ18O) d-excess, and moisture sources reveal decadal trends in SW-France. • Seasonal and interannual changes of δ18O p not only respond to atmospheric temperature but also significantly to moisture sources. • The impact of moisture sources and temperature on δ18O p were quantitatively evaluated. In the mid-high latitude region, variations of stable isotopic compositions of atmospheric precipitation (δ18O p and δD p) were commonly regarded as reflecting the "temperature effect". However, some studies have indicated that changes in moisture sources are important controlling factors for δ18O p. To clarify whether there are connections between δ18O p and variations of moisture sources in Southwest France (SW-France), whose implications for speleothem δ18O are of great importance, we have used among the longest isotopic time-series from SW-France (Le Mas and Villars stations) and a 5 days' reconstruction of air mass history during the 1997–2016 A.D period based on the HYSPLIT tracking model. We found the percentage of initial moisture sources (PIMS) as important factors controlling the oxygen isotope composition of precipitation in SW-France, whether monthly or inter-annual timescale was considered. Additionally, we observed that the δ18O p preserved the signal of local temperature, supporting the "temperature effect", while no evidence for its "amount effect" has been observed. These quantified links between PIMS/local-temperature and δ18O p appear useful references to understand the link between stable oxygen isotopes and climate parameters. Our long-term monitoring of δ18O p , d-excess, and moisture sources reveals decadal trends, highlighting a tight coupling in hydrologic systems and relatively fast changes on rainfall sources controlled by atmospheric circulations in SW-France. [ABSTRACT FROM AUTHOR]