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Technical improvements at the end of the Bronze Age led to the rise of a 1rst generation of major sea powers around the Mediterranean Sea, such as Etruria in modern Italy. The Etruscan coast was the fringed by a series of large lagoons. Only one survives today: the lagoon of Orbetello. The lagoon is preserved by two subparallel sand spits that connect former Argentario island to mainland Italy, as situation that today protects it from rapid infilling. A third sand spit, in the middle of the lagoon, hosts the Etruscan city of Orbetello. Today, three canals connect the lagoon to the sea. A massive phase of eutrophication driven by the ingress of fertilizers has plagued the lagoon in late 20th Century. Eutrophication at times has spurred fish and bird kills, and the release of mercury in the water column. Major contingency plans have been implemented to fight off eutrophication, with various success. However little is known of the lagoon management and the evolution of Orbetello before the 17th century CE. Nonetheless, the wealth of the city and the health of its lagoon have been tightly related during the past three millennia. To track this coevolution, a large team of researcher has been assembled to conduct an analysis of the lagoon sediments using XRF scanning of cored sediments, SMIR, Rock Eval, hyperspectral imaging of chromatic pigments, analysis of mercury and phosphorus content, ostracods and pollen assemblages, to document the links between sediment facies, eutrophication and salinity crises, as a result of successive phases of rise and demise of lagoon management over the past three millennia. Here, we focus on the sub-bottom imaging conducted in the very shallow (< 1.5m) waters of this extensive (30 km2) lagoon. The Exail Echoes 10 000 sub-bottom profiler reveals individual layers that can be traced across the lagoon, allowing stratigraphic correlations between cores, and highlighting the environmental significance of the sedimentary facies. Acoustic imaging using a 3.5 kHz Chirp systems from Exail (Haliotis R/V) was conducted offshore to document the architecture of the sand spits protecting the lagoon. The architecture of the deposits, 14C, OSL, and U-Th dating reveal that the lagoon results from the drowning of strandplains that started forming on both side of the older, central sand spit, at the end of the postglacial transgression. Drowning accompanied the final rise in sea level over the past 6.5 ka, forming two lagoons on both sides of the central spit. These initial lagoons eventually coalesced after drowning the central sand spit. Continuation of the lagoon level rise since Antiquity led to the flooding of Bronze Age, Etruscan and Roman settlements. Sub-bottom imaging in the lagoon reveals buried structures possibly used for navigation and salinity control. Sedimentation is marked by an alternation of black, shelly organic silty clays and decimeter-thick layers of broken shells. Radiocarbon dating indicates that the cores capture up to five millennia of sedimentation, with a sharp decrease in sedimentation rates four millennia ago.

A lightweight geophysical survey method was used to estimate quarry filling layer thickness based on EMI and DCP data.

At the end of the Bronze Age, technical improvements have made possible the rise of the first generation of major sea powers around the Mediterranean realm, such as Etruria in Italy. The Etruscan coast was fringed by large lagoons, of which only one survives today: the lagoon of Orbetello. This peculiar lagoon is held between two sand spits that connect the former island of Argentario to the mainland. A third sand spit lies in the middle of the lagoon, and supports the Etruscan city of Orbetello. Archeological investigations suggest that the lagoon was connected to the sea through a natural outlet until the 9th century BCE, when an integrated management plan of the lagoon was implemented to optimize fishing. Subsequent closure of the natural outlet implies that lagoon management heavily subsequently relied on man-made openings to maintain the lagoon connected to the sea and nearby rivers. Today, three canals connect the lagoon to the sea. Management plans were implemented in the late 20th Century to fight a massive phase of eutrophication driven by excess release of fertilizers. Eutrophication as responsible for extensive fish kills, and to the release of mercury in the water column. Little is known about lagoon management and the evolution of the city before the 17th century CE, but it is clear that the wealth of the city of Orbetello and the health of its lagoon have been strongly correlated over the past three millennia. To track this coevolution, we conducted a coring campaign coupled to sub-bottom imaging in the very shallow (2) lagoon. iXblue Echoes 10 000 sub-bottom profiler reveals individual layers that can be traced across the lagoon, allowing stratigraphic correlations between cores, and highlighting the environmental significance of the sedimentary facies. Architecture of the deposits reveals a pronounced transgression of the lagoon over its shallowly inward-dipping margins since Antiquity. This led to the flooding of an array of regularly-spaced Roman farms along its southern shorelines, and to a more important flooding of Etruscan structures. Lagoon level rise was driven by a combination of regional sea level rise and fluctuations in the hydraulic balance of the lagoon, controlled by the opening and closure of canals. Sub-bottom imaging reveals buried structures tentatively interpreted as docks and canals used for navigation and salinity control. Sediment analyses under XRF scanning, Rock Eval, and hyperspectral imaging reveals that sedimentation is marked by an alternation of black, shelly organic silty clays and decimeter-thick layers of broken shells. Radiocarbon dating indicates that the cores capture up to five millennia of sedimentation. Ongoing analysis of mercury and phosphorus content, ostracods and pollen assemblages, and chromatic pigments in the organic fractions are expected to document the links between sediment facies, eutrophication and salinity crises, and the rise and demise of land and lagoon management through the past three millennia. A sub-bottom profiling campaign in June 2022 is aimed at mapping the observed structure. Further coring is planned near putative man-made structures next Fall.

– Electrical resistivity and dielectric permittivity mapping using an electrostatic survey device. – GPR delineation of probable ancient anchor point of the ancient bridge. – Combination of GPR and electrostatic surveys for urban archaeology.

– Use of high resolution GPR mapping for the study of masonry walls. – Delineation of underlying the main characteristics of the wall. – Evaluate the different steps of renovation and/or partial reconstruction of the wall.

La commanderie de Jalès, à Berrias-et-Casteljau dans le sud de l’Ardèche, est l’une des maisons du Temple les mieux préservées de cette région. Étudiée dans le cadre d’un Projet Collectif de Recherche depuis 2017, elle fait l’objet de recherches pluridisciplinaires associant historiens, géographes, archéologues et géophysiciens. Ce projet vise à mettre en lumière les différentes périodes de genèse, de développement et de transformation de la maison de la commanderie, ensemble d’édifices destinés à la vie de la communauté religieuse, mais aussi du territoire et du vaste domaine agricole au cœur duquel elle s’est développée.L’année 2019 a permis de progresser sur plusieurs points. Sur un plan général, l’étude archéogéographique de l’environnement de la commanderie et de ses dépendances a été confiée à Maël Crépy (géographe, chercheur associé Archéorient), qui a pu travailler à la fois à la mise en contexte de l’ensemble du territoire de la commanderie et à une prospection de terrain sur les dépendances. Cette dernière prospection a été réalisée avec Emmanuelle Régagnon et Olivier Barge (Archéorient). L’étude historique, menée par Laurent D’Agostino (Atelier d’Archéologie Alpine), a progressé par le dépouillement et la transcription d’un certain nombre de textes, sans qu’il soit encore possible d’en présenter la synthèse.Sur le terrain, un nouveau chantier archéologique a été consacré aux bâtiments en avril, accueillant une dizaine d’étudiants de l’Université Lyon 2 pendant deux semaines. Le chantier a comporté un volet d’étude de bâti sur les bâtiments conventuels, dirigé par Evelyne Chauvin-Desfleurs et Laurent D’Agostino (Atelier d’Archéologie Alpine), et des sondages au sol dans la cour nord conduits par Audrey Saison (Pôle Archéologique de l’Ardèche) en recherche de l’enceinte de la basse cour. Bien que les données restent à traiter, Christophe Benech (Archéorient) a pu mener deux campagnes de prospection géophysique dans l’aile nord des bâtiments conventuels, à la fois dans les sols et de manière plus expérimentale dans les élévations. Les analyses xylologiques et dendrochronologiques réalisées durant l’hiver 2018-2019 par Stéphanie Wicha et Antoine Nicault (Archéobois) documentent par ailleurs différentes phases de construction entre le milieu du XIVe siècle et le XXe siècle.Enfin, nous avions livré en 2018 les premières images de la restitution 3D de la chapelle réalisée en collaboration entre Evelyne Chauvin-Desfleurs et Edouard Maréchal et Benoît Campo (architectes, Paris Picture Club). L’achèvement de l’étude de la chapelle a permis de revoir nos hypothèses de restitution des matériaux et d’aboutir à des rendus plausibles de l’architecture, mais aussi des matériaux de construction employés et de leur mise en œuvre.

An electromagnetic (EM) tool working in the medium-frequency range allows the determination of the electric conductivity and dielectric permittivity of soils with a single measurement. It brings information about different state parameters of soils, especially their water and clay contents for a significant volume of investigation. To investigate these properties, a medium-frequency-range EM prototype, the CE120, was built using a perpendicular coil Slingram configuration with a working frequency of 1.56 MHz and a fixed coil spacing of 1.2 m. This configuration was chosen using modeling with the purpose of measuring electric resistivities up to a few thousands of ohm-meters and relative dielectric permittivities as low as two. These thresholds match the expected parameters values in the medium frequency range. Moreover, the CE120 characteristics allowed for an investigation depth between 2 and 2.5 m, depending on the nature of the soil. The prototype was tested on two different soils with water variations: sandy alluvia and clay-loam soil. The electric resistivities of the sandy alluvia can reach [Formula: see text], which is higher than the detection threshold of the CE120. Only the measured dielectric permittivity can be interpreted in terms of water contrasts. Four different zones corresponding to four different water contents were detected. For the clay-loam soil, the electric conductivity and dielectric permittivity measure the water content variations created by the wheat roots. At 1.56 MHz, the high-frequency equations linking the dielectric permittivity to the volumetric water content have a limited validity. Laboratory measurements for each different soil type are necessary to deduce empirical relations. In both cases, the results are coherent with the measured mass water content variations.

International audience; Laboratory physical modelling and non-contacting ultrasonic techniques are frequently proposed to tackle theoretical and method- ological issues related to geophysical prospecting. We used an innovative experimental set-up to perform laser-Doppler acoustic probing of granular materials with varying water levels to target near-surface hydrogeological applications. The preliminary results presented here show a clear influence of the water level on both first arrival times and dispersion of guided waves, and significant differences in terms of amplitudes. They validate the use of such approach to benchmark recently developed methods for water saturation detection in hydrogeophysics.

International audience; The characterisation and monitoring of aquifer systems mainly rely on piezometric and log data. Delineating spatial variations of lithology between piezometers is a delicate task, which inevitably generates errors possibly propagating into hydrogeological models. Seismic methods have been proposed to: (i) improve the low spatial resolution of borehole data, (ii) provide a characterisation of the subsurface geometry, and (iii) estimate the physical parameters of the medium influenced by the presence of water and the associated flow and transport processes. The joint study of pressure (P-) and shear (S-) wave seismic velocities (VP and VS, respectively), whose evolution is strongly decoupled in the presence of fluid, has been proposed through the estimation of the VP/VS ratio and Poisson's ratio. A specific methodology has been developed for the combined exploitation of P- and surface waves present on single seismic records. The use of this methodology in several geological and hydrogeological contexts allowed for estimating VP/VS ratio lateral and temporal variations in good agreement with a priori geological information and existing geophysical and piezometric data. Laser-based ultrasonic techniques were also proposed to put these processing techniques in practice on perfectly controlled physical models and study elastic wave propagation in partially saturated porous media.

International audience; When applied to hydrogeology, seismic methods are generally confined to the characterisation of aquifers geometry. The joint study of pressure-(P) and shear-(S) wave velocities (V P and V S) can provide supplementary information and improve the understanding of aquifer systems. This approach is proposed here with the estimation of V P /V S ratios in a stratified aquifer system characterised by tabular layers, well-delineated thanks to electrical resistivity tomography, log and piezometer data. We carried out seismic surveys under two hydrological conditions (high and low flow regimes) to retrieve V S from both surface-wave dispersion inversion and SH-wave refraction interpretation, while V P were obtained from P-wave refraction interpretation. P-wave first arrivals provided 1D V P structures in very good agreement with the stratification and the water table level. Both V S models are similar and remain consistent with the stratification. The theoretical dispersion curves computed from both V S models present a good fit with the maxima of dispersion images, even in areas where dispersion curves could not be picked. Furthermore, V P /V S and Poisson's ratios computed with V S models obtained from both methods show a strong contrast for both flow regimes at depths consistent with the water table level, with distinct values corresponding to partially and fully saturated sediments.

International audience; Chalk groundwater is an important aquifer resource in France because it accounts for a production of 12 million m3 y-1 with a large proportion reserved for drinking water. Processes occurring in the unsaturated zone (UZ) and the overlying superficial formations have a high impact on Chalk groundwater geochemistry and require better understanding. The study site is a former underground Chalk quarry located near Beauvais (France) that extends over 1200 m in length, at a depth ranging from 20 to 30 m. The water table intersects the cavity creating 15 underground "lake" that give access to the Chalk groundwater. Lakes geochemistry has been studied: water samples were collected in July 2013 and major ion concentrations were analyzed. UZ and clay-with-flints thickness above each lake were estimated qualitatively using an electromagnetic sensor (EM31) and Underground GPS. The results unexpectedly showed that groundwater quality varied widely in spatial terms for both allochthonous and autochthonous ions (e.g., HCO3- ranged from 2.03 to 4.43 meq L-1, NO3- ranged from 0.21 to 1.33 meq L-1). Principal component analysis indicated the impact of agricultural land use on water quality, with the intake of NO3- as well as SO42-, Cl- and Ca2+. Chalk groundwater geochemistry is compared with the nature and structure of the UZ. We highlight correlations (1) between thick clay-with-flints layers and the ions Mg2+ and K+, and (2) between UZ thickness and Na+. In conclusion, this paper identifies various ion sources (agriculture, clay-with-flints and Chalk) and demonstrates different processes in the UZ: dissolution, ionic exchange and solute storage.

International audience; A study of spatial heterogeneity of groundwater geochemistry is conducted within an abandoned underground quarry of chalk. An associated geophysical study (electromagnetic mapping at low induction number, and electrical resistivity tomography) is carried out on the surface. It allows to determine the structural geometry of superficial formations, in order to understand the link between the geochemical spatial variability of the lakes and the properties of the environmental medium.

The renewal of existent railways requires the characterisation of the mechanical properties of railway platforms (RP), thus raising the need to select appropriate maintenance actions. Conventional techniques (geotechnical soundings, coring) remain local, destructive, expensive and with low yields. Using non-destructive investigation techniques for local diagnosis and monitoring thus appears of great interest for enhancing RP control. Seismic surface-wave methods have been proposed to estimate in situ mechanical parameters of the superficial layers below railways. In this context, a joint geotechnical and seismic survey was carried out along the Northern Europe high-speed line (LGV) in order to precisely determine the origins of a phenomenon affecting the geometry of the track. Strong a priori knowledge of the RP structure allowed for inverting dispersion measurements for 1D VS models along the track. The results showed a contrast of VS in the loess lying below the RP, between areas where the phenomenon was observed and those it was not. This contrast was confirmed by Bender Elements measurements of VS performed on core drilling samples, and corresponded to the lateral variations observed along the track. These results encourage considering dispersion measurements as an appropriate tool of RP monitoring.