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Observations of the condition of the walls of the Salle des Taureaux (Great Hall of the Bulls) in the prehistoric cave of Lascaux showed important moisture variations over time. These are related to the presence and activity of four discontinuities, or joints, within the Upper Cretaceous limestone. There are two distinct hydrogeological regimes in the chamber: one corresponds to a superficial water table with a significant discharge; the other is caused by the activity of the joints, which cannot be measured. Observations of the activity of two of the joints (nos 3 and 4)for the period 2000-2004 showed that the activity of the joints is not always in phase with that of the water table and that it cannot be directly linked to the rise of the water table. These two joints are responsible for the appearance of damp areas on the walls that are subjected to the microclimate in the chamber. If water evaporates from the walls, this could lead to crystal growth and the appearance of a calcite film obliterating the rock suite in general and, most importantly, the painted figures. [ABSTRACT FROM AUTHOR]

Massive walls and a buttress were constructed during the seventeenth century in order to strengthen the foundations of the bell tower which stands over the monolithic subterranean church of St Emilion in south-west France. These works have resulted in an overload of the geostructures which underlie the monument. Indirect methods of analysis and internal sounding (auscultation) of the geological materials, complemented by various direct measurements, have permitted a precise assessment of the current condition of the vault and pillars and allowed a plan of conservation to be developed, followed by the construction of a reversible Support system. [ABSTRACT FROM AUTHOR]

Seasonal variations of sea level have an important impact on coastal groundwater level and salinity. Consequently, they cause spatiotemporal changes in the seawater/freshwater interface. The oceanic tide effect on groundwater dynamics and salinity was investigated in the coastal aquifers of Sahel Doukkala, Morocco. Continuous monitoring of water level and electrical conductivity (EC) was carried out in two coastal wells (drawing from two different aquifers) over a period of 9 months. The main objective of the study was to characterize the aquifers’ exposure to anthropic pumping operations and oceanic tide oscillations. The obtained results showed that oceanic tide has a significant effect on groundwater level as well as on water salinity. The fluctuation periods of groundwater level and tidal level were found to be equal, with a specific time lag. Hydraulic diffusivity was calculated using both confined- and semi-confined-aquifer methods and by analyzing both the time lag and amplitude damping factor. Results indicate hydraulic diffusivity differences between the two aquifers. In addition, there were apparent differences depending on whether time lag or amplitude was analyzed, possibly due to effects of heterogeneity within the aquifers. A detailed study of water EC variation revealed the significant influence of daily and synodic tide on groundwater salinity. Water EC variations were significant when hydraulic diffusivity is higher, indicating that sea-level oscillations induce freshwater/seawater interface movement and consequently influence the groundwater quality. [ABSTRACT FROM AUTHOR]

Leye Cave (Dordogne, France) is a laboratory cave in the Vézère area, a region that contains some of the most famous rock art caves in the world such as Lascaux, Font-de-Gaume and Combarelles, and is listed as Human World Heritage by UNESCO. Leye Cave was selected because it is representative of painted caves, with respect to parameters such as its geological stage, the presence of water and carbon dioxide, the geological state of its walls, and the size of the cave. These wall states are studied to better understand the conditions of conservation of rock art caves without damaging them. The choice of an equivalent medium, i.e., a non-painted cave, was made to be able to conduct experiments or take measurements that would not have been possible in a rock art cave. The climatic conditions (temperature, hygrometry, etc.) monitored since 2011 are central to our understanding of the genesis and evolution of wall states. Leye Cave is sub-horizontal then descendant, forming a cold air trap. The phenomenon of condensation is thought to be important in the genesis of these wall states. Our article presents a model which describes the competition that exists between the conduction of the rock heating the air and the convection cooling the rock, in the area named the "Throne Chamber", located in the deepest parts of the cave. [ABSTRACT FROM AUTHOR]

This study aims to assess the evolution of seawater intrusion between 1992 and 2011 periods in the coastal aquifers of Oualidia. To achieve this objective, the combination of geoelectrical and hydrochemical methods was adopted. Apparent resistivity maps, using 74 Vertical Electrical Sounding (VES) performed on 1992, allowed to distinguish two different zones. The conductive one, with apparent resistivity ranging between 4 and 86 Ω·m, is limited to 1 km with respect to the ocean. Meanwhile, the resistant one is much farther from the coastline. Besides, results of Electrical Resistivity Tomography (ERT) profiles performed during 2011 are in good agreement with those obtained by apparent resistivity maps. The ERT profiles show a conductive level characterized by low resistivity below 30 Ω·m assigned to seawater intrusion effect. Moreover, hydrochemical analysis, performed on 19 wells during three different periods, on June, December 2010 and May 2011, indicates that the most affected part with marine waters was at that time localized in the first kilometer from the ocean, with high amounts of Na + and Cl − ions. Beyond this fringe, mineralization becomes very weak. Overall, the comparison of old VES with recent ERT coupled with hydrochemical results suggest no important evolution of the salt wedge since 1992. [ABSTRACT FROM AUTHOR]

Numerous fire marks occur on the walls of the Chauvet-Pont d’Arc cave. Dating indicated that some of the fires were contemporary to the Aurignacian. Violent thermal shocks were observed in surprisingly narrow areas of the cave. This raises numerous archaeological questions about the function of the fires; the answers depend on the location of the hearths, and the intensity of the fires. Numerical simulation was used here to provide information about the behaviour of fires in such confined spaces. An underground non-archaeological site, in a limestone quarry, was equipped to monitor fires in an environment similar to that of the Megaceros gallery of the Chauvet-Pont d’Arc cave. The fire and the movement of heat and smoke in the quarry were simulated by the open source code “Fire Dynamics Simulator (FDS)”. Results were validated on wall temperatures recorded behind and above the fire. The thermo-mechanical impact of the fire on the rock was simulated with CAST3M software, providing the most probable zones for limestone spalling due to thermal gradients. The validated approach will, in a forthcoming study, be applied to the Chauvet-Pont d’Arc cave, in which coupled simulations in the air and in the rock should indicate the location of the hearths and the intensity of the fires that generated the marks. [ABSTRACT FROM AUTHOR]

The Lascaux cave, located in southwest France, is one of the most important prehistoric cave in the world that shows Paleolithic paintings. This study aims to characterize the structure of the weathered epikarst setting located above the cave using Time-Lapse Electrical Resistivity Tomography (ERT) combined with local hydrogeological and climatic environmental data. Twenty ERT profiles were carried out for two years and helped us to record the seasonal and spatial variations of the electrical resistivity of the hydraulic upstream area of the Lascaux cave. The 20 interpreted resistivity models were merged into a single synthetic model using a multidimensional statistical method (Hierarchical Agglomerative Clustering). The individual blocks from the synthetic model associated with a similar resistivity variability were gathered into 7 clusters. We combined the resistivity temporal variations with climatic and hydrogeological data to propose a geo-electrical model that relates to a conceptual geological model. We provide a geological interpretation for each cluster regarding epikarst features. The superficial clusters (no 1 & 2) are linked to effective rainfall and trees, probably a fractured limestone. Another two clusters (no 6 & 7) are linked to detrital formations (sand and clay respectively). The cluster 3 may correspond to a marly limestone that forms a non-permeable horizon. Finally, the electrical behavior of the last two clusters (no 4 & 5) is correlated with the variation of flow rate; they may be a privileged feed zone of the flow in the cave. [ABSTRACT FROM AUTHOR]

Cussac cave was investigated to assess the cave air temperature variations and to understand its ventilation regime. This cave is located in an active karst system in the south west part of France. It has a single entrance and is considered as a cold air trap. In this study, air mass exchanges were probed. Measurements of temperature and Pco with a 30-min frequency were made in several locations close to the cave entrance. Speed of the air flow was also measured at the door of cave entrance. Results show that cave air Pco varies from 0.18 to 3.33 %. This cave appears to be a CO source with a net mass of 2319 tons blown in 2009. Carbon-stable isotope of CO (Cco) ranges from −20.6 ‰ in cold season to −23.8 ‰ in warm season. Cave air is interpreted as a result of a mix between external air and an isotopically depleted air, coming from the rock environment. The isotopic value of the light member varies through time, from −23.9 to −22.5 ‰. Furthermore, this study ascertains that the cave never stops in communicating with the external air. The ventilation regime is identified. (1) In cold season, the cave inhales at night and blows a little at the warmest hours. However, in warm season, (2) cave blows at night, but (3) during the day, a convection loop takes place in the entrance area and prevents the external air from entering the cave, confirming the cold air trap. [ABSTRACT FROM AUTHOR]

The Lascaux cave, located in southwest France, is one of the most important prehistoric caves in the world that show Paleolithic paintings. This study aims to simulate the 3D geological environment of the cave by geostatistical modeling based on 2D Electrical Resistivity Tomography (ERT) data. Seventeen ERT profiles were carried out resulting in 64,195 geolocated resistivity values, covering about 14,500 m 2 of the Lascaux site. From this dataset, 3D resistivity geo-model has been built by geostatistical method. We used geotechnical data from 36 boreholes and cone penetrometer tests to validate the geo-model. By modeling from 2D data, we can establish a good estimation of the 3D geological environment of the Lascaux site. Our results show that the site can be generally separated in two parts: the limestone promontory in the center and the detrital formations located in both east and west sides. There is a high contrast between resistivity of the two formations: 45 Ω·m (detrital formation) to 556 Ω·m (limestone) with a rough boundary. In the center, the limestone could also be separate into two parts: a superficial layer of weathered limestone (150 Ω·m) and a deeper layer with compact limestone (556 Ω·m). [ABSTRACT FROM AUTHOR]

Inland aquifers are connected to the ocean through permeable coastal sediments. The mixing zone between sea water and fresh-groundwater forms a so-called subterranean estuary. The dynamics and the shape of this interface influence fluxes of fresh water to the coastal zone. On tidal sandy beaches, tide and waves actions lead to the formation of an intertidal saline circulation cell that complements the structure of the subterranean estuary between sea water and fresh water. The upper beach corresponds to the recharge zone, where large volumes sea water penetrate the sediment at high tide, whereas the lower beach corresponds to the discharge zone of older pore water that remains in the sand for several tidal cycles. The objective of our study was to characterize the shape and the evolution of this saline cell in a high-energy macro-tidal beach, the Truc Vert beach (SW France). In order to assess the distribution of saline, brackish and fresh water in this high-energy beach aquifer, we conducted electrical resistivity tomography (ERT) measurements from the lower beach face to the sand dune in winter 2012–2013. We also measured water table elevation and salinity in three piezometers situated at the base of the dune and in pore waters at low tide on tidal cross-shore transects. Results show that the intertidal saline plume can be identified and localized with the ERT method. The fresh-saline water interface is almost vertical in the upper beach. The saline circulation cell occupies the upper part of the tidal beach over a thickness of 5 m deep. Below this saline cell, a brackish water flows to the ocean: about 30% of fresh water was found in pore water in the lower part of the beach. Shifting of the vertical front between saline and fresh waters of about 2–5 m occurred during the spring–neap tidal cycle. This migration is small relative to the beach size, suggesting that the transition zone is relatively stable. The variations in salinity of the circulation cell suggest that the position of the saline plume is controlled by the spring tide level. Our results differ slightly from studies based on modelling and piezometric measurement made in less exposed micro-tidal sandy beaches. Our data would allow to better constrain numerical models that would enable to quantify water residence time and solute fluxes in subterranean estuaries of high-energy beaches. [ABSTRACT FROM AUTHOR]

The Lascaux Cave, located in the south-eastern part of the department of the Dordogne (24, France), is considered to be one of the most important prehistoric caves in the world. The scope of this study is the protection and conservation of the Lascaux paintings from a hydrogeological and climatic environmental standpoint. Geophysical methods enable us to monitor the environment of the decorated cave in a non-invasive way. Electrical resistivity tomography (ERT) using a pole--dipole array, together with analysis of the local effective rainfall (groundwater recharge) and the flow in the cave, helps us to identify an area where upstream underground water is probably stored e.g. a recharge zone. There is a relationship between resistivity change in this zone and the underground flow measured in the cave, but with a time lag. Thus systematic electrical surveys following rainy periods could be used to predict the beginning of the underground flow and in so doing provide valuable advice for the preservation of the Lascaux Cave. [ABSTRACT FROM AUTHOR]

Experiments have been carried out at two sites in periglacial (MAAT ≈ 0 °C) and alpine (MAAT ≈ 4 °C) contexts in the Pyrenees, including open-air and cave loci, to document in detail the role of site formation processes and taphonomic agents in the degradation of archaeological assemblages. In both sites, the experimental cells have undergone significant changes over the five years of measurements. These are marked by slow downslope creep of lithic artefacts due to solifluction, rain creep, and the impact of debris fallen from the wall in the cave. The behaviour of bone material was significantly different from that of lithics, due to the activity of scavengers. This was responsible for scattering a high proportion of bone remains, and displacements were typically significant. Such activity was also responsible for a high number of bone elements being lost (1/3 to 2/3 of the bones). Weathering, mostly cracking and exfoliation, also affected dry bone material in the open-air cells. The measurements have highlighted the specific nature of the cave context, which plays a protective role for bone remains against meteoric agents. The talus at the entrance of the cavity was also characterized by a strong spatial heterogeneity in sedimentary processes, which may generate a differential preservation of the assemblages. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this proposal is to present an original approach to the study and preservation of rock art caves. A multidisciplinary study of cave wall alteration will be performed to understand the impact of environmental context on the evolution of wall surfaces. The approach involves the choice of a cave with characteristics similar to painted caves in the studied area (Vézère Valley in Dordogne, France): e.g., cave wall alteration, lithology, morphology, etc. This selected cave is intended to become a laboratory cave, monitored for the acquisition of chemical, physical and biological environmental data on bedrock, air and fluids along with their characteristics. A cave without art or archaeological interest has been chosen specifically to conduct experiments, to make in situ analysis and to obtain samples. The results are to be completed by specific observations in several other caves and compiled in a database. [Copyright &y& Elsevier]

Abstract: An Eulerian/Lagrangian method for the numerical simulation of incompressible convection flows interacting with complex obstacles is developed in this article. This method is successfully validated on natural convection cases, a porous medium and the Sierpinski carpet. The ability of the model to take accurately into account complex topologies allows its application to natural convection in the Lascaux cave, in order to give information on velocities, temperature and moisture content values and to provide helpful details to the conservators of the cave. [Copyright &y& Elsevier]