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International audience; The Western Gneiss Region in Norway is constituted by a crustal nappe stack that comprises someof the best-preserved exhumed ultra-high pressure (UHP) terranes on Earth. The UHP rocks resultfrom the subduction of the western edge of the Baltica craton beneath Laurentia during theCaledonian orogeny. Mafic eclogites form lenses within granitoid orthogneisses and show the bestrecord of the pressure and temperature evolution. Their exhumation from the UHP conditions hasbeen largely studied, but the prograde evolution has been rarely quantified in the eclogitesalthough it constitutes an important constraint on the tectonic history of this area. This studyfocused on an unaltered eclogite sample from Vågsøy in the Nordfjord region. This sample wasinvestigated using a large panel of methods including phase-equilibria modelling, trace-elementanalyses of garnet, trace- and major-element thermo-barometry and quartz-in-garnet barometryby Raman spectrometry. The eclogite comprises omphacite, garnet, white mica, epidote andamphibole and accessory rutile, quartz, zircon, carbonates and kyanite. Garnet shows a grossularrichcore with inclusions of quartz, epidote, white mica and amphibole, while grossular-poor rimsare enriched in pyrope and middle rare-earth elements and include omphacite and rutile.Inclusions in garnet core point to crystallisation conditions in the amphibolite facies at 550–600 °Cand 11–15 kbar, while chemical zoning in garnet suggests growth during isothermal compressionup to the peak pressure of 28 kbar at 600 °C, followed by near-isobaric heating to 640–680 °C.Isothermal decompression to 8–13 kbar is recorded in fine-grained clinopyroxene-amphiboleplagioclasesymplectites. The absence of a temperature increase during compression seemsincompatible with the classic view of crystallization along a geothermal gradient in a subductionzone and may question the tectonic significance of eclogite-facies metamorphism. Two maintectonic scenarios are discussed to explain such an isothermal compression: (1) either the maficrocks were originally at deep level within the lower crust and were then buried along theisothermal part of the subducting slab, or (2) the mafic rocks recorded significant tectonicoverpressure at constant depth and temperature conditions during the collisional stage of theorogeny. A multi-chronometer geochronological study is currently performed and expected tobring additional, discriminant constraints on this P–T evolution.

International audience; Eclogitization reactions in mafic rocks involve large volume changes, porosity evolution and fluidtransfer. They impact many important geological processes such as the localization of deformationand fluid channeling at intermediate depth in subduction zone. The study of exhumed eclogiticbodies in orogens shows that eclogitization of the oceanic crust is heterogeneous from both astructural and metamorphic point of view. For example, in the European Alps, the Allalinmetagabbro shows high strain areas, consisting of hydrous metagabbros, fully equilibrated undereclogite-facies conditions during the Alpine orogeny. Conversely, large volumes of low strain, fluidundersaturatedgabbros remained largely unaffected by the high-pressure (HP) metamorphism,locally preserving igneous textures and even, occasionally, relics of their magmatic mineralogy.The intensity of deformation as well as the degree of eclogitization in the metagabbro have beenshown to be directly related to the extent of pre-Alpine hydration during high-temperaturehydrothermal alteration [1]. However, the influence of this degree of hydration on (1) reactionkinetics and/or (2) enhancing rheological contrasts leading to heterogeneous deformationpatterns and metamorphic conditions is still debated.In order to address this issue, we propose a multidisciplinary study involving petrographic andmicrotextural observations combined with 2D thermo-mechanical numerical models allowing todiscuss the role of pre-Alpine hydrothermal alteration on the development of HP metamorphicassemblages.We present petrographic and textural data from three different types of rocks from the Allalinmetagabbros: i) undeformed and mostly untransformed metagabbros, with relics of igneousaugite and plagioclase, ii) coronites, with olivine pseudomorphs showing different levels ofhydration, rimmed by a garnet corona, and iii) eclogitized metagabbros, with olivine andplagioclase sites fully replaced by high-pressure assemblages.The role of protolith hydration on the observed range in metamorphic facies is then tested byusing 2D thermo-mechanical models that allow to simulate the deformation of a strong and dryrock with several randomly oriented weak and hydrous zones. Our results show that the shearingof heterogeneous rock can lead to the formation of localized ductile shear zone within a matrixthat remains relatively undeformed but where plastic deformation can occur. The associated P field is also highly heterogeneous, with P ranging from 1 to 3 GPa. The deformation patterns and Pmodelled may suggest that locally hydrated portions of the gabbro acted as rheologicalperturbations sufficiently efficient in producing the structural and metamorphic record nowobserved in the field.[1] Barnicoat, A. C. & Cartwright, I. (1997) Journal of Metamorphic Geology 15, 93–104

International audience; High-elevation, low-relief surfaces are widespread in many mountain belts. However, the origin of these surfaces has long been debated. In particular, the Southeast (SE) Tibetan Plateau has extensive low-relief surfaces perched above deep valleys and in the headwaters of three of the world’s largest rivers (Salween, Mekong and Yangtze). Synthesized low-temperature thermochronologic data indicate that uplift of the Tibetan Plateau may have propagated progressively from NW to SE, with thermochronologic ages at ~50 Ma observed in the headwaters and interfluves of the rivers but young ages

Ferruginous duricrust formation takes place by dissolution and accumulation of iron during the wet season and precipitation during the dry season. However, the formation of iron duricrusts has always been the centre of much debate. They commonly form as hard iron layers in tropical and subtropical environments with strong climatic seasonality. They were first described in Africa, Australia and India in the 1950’s. They often cap landscapes, which can be explained by their extremely high iron content making them more resistant to mechanical weathering. However, in recent years, iron duricrusts were also described at depth in the regolith, like in South America.This has led to 2 distinct formation hypotheses: the first one relies on the vertical beating of the water table most likely in a stable environment combined to lateral hydraulic transport of iron. In this scenario, iron hydroxides accumulate in one specific region after being transported from surrounding source areas through the water table, and precipitate as Fe3+ during the dry season. Through time, this leads to duricrusts forming within the water table beating range. This model is compatible with duricrusts forming at depth within the regolith. The second hypothesis relies on the vertical, in situ leaching of elements and resulting compaction and surface lowering. During weathering, iron nodules accumulate with the progressive leaching of soluble elements from the parent rock, leaving only the iron oxides, ultimately forming a duricrust. It implies a genetic link between the duricrust, the lateritic profile and the underlying parent rock. This model explains why duricrusts are mostly observed near the surface. Nevertheless, there is no consensus on the conditions under which either of these hypotheses prevail. To address this issue, we developed two separate first-order numerical models representing the two hypotheses for duricrust formation. We used the models to demonstrate that the hypotheses lead to different scenarios of duricrust formation by running a large number of simulations. Especially, we show that the stability of a landform is a discerning element between the 2 models. In the first case, quiescent periods of time in between uplifting periods are crucial, while in the second case, constant dynamic uplift is needed to enable the accumulation of enough elements by compaction.

Landscape evolution is intimately related to processes of erosion and rock fragmentation that transform the bedrock into granular material that can be transported by rivers. Among the involved processes, rock fracture seems to play a key role on the mechanisms and rates of erosion, and on the size of the produced sediments. Efforts have been focused on erosion along hillslopes, yet, as far as we know, there is no systematic study of the impact of fracture density and orientation on bedrock erosion within rivers and on the geometry of the produced grains. This is partly due to the characteristic timescales of the processes at stake (abrasion and plucking) that strongly limit direct field observations. To address this question, we develop an experimental setup designed to simulate the erosion of a fractured bedrock within a river. The setup is made up of an annular plexiglas cylinder, at the bottom of which is placed a fractured concrete disk. The fracture network is designed numerically and then printed in 3D in PolyVinyl Alcohol (PVA), a thermo-plastic that softens when in contact with water. Water and granite sediments are added on the top of the disk, and a motor-driven propeller circulates the water and the sediments so that erosion can proceed. A set of cameras is used to reconstruct the topography by Structure From Motion so that the erosion dynamics is recorded quantitatively and at high-frequency. The first set of experiments explore the role of fracture spacing and azimut. The preliminary results suggest that for a given lithology, the relationship between fracture density and sediment size controls the dominant mode of erosion (abrasion vs plucking). We also observe a clear relationship between the fracture spacing and the size of the concrete clasts produced by plucking. We are currently running additional experiments with different fracture orientation and we also explore the role of the granite sediment size. Based on these experimental results, our objective is to build and validate a conceptual model of erosion and landscape evolution that integrates the role of bedrock fracture within rivers.

Resumen del trabajo presentado en la EGU General Assembly 2022 , celebrada en Viena (Austria), del 22 al 27 de mayo de 2022., Cushion gas injection at the Underground Gas Storage (UGS) project of Castor, Spain, induced hundreds of events, including thirteen with magnitude higher than 3.5 that were felt by the local population and led to project cancellation. The sequence of felt events comprises the three largest earthquakes (M4.08, M4.01 and M3.97) ever induced by any of the more than 640 UGS facilities around the world. The largest earthquakes occurred 20 days after shut-in, when pore pressure buildup had already dissipated. The induced earthquakes nucleated at depths ranging from 4 to 10 km, significantly deeper than the storage formation, which is located at 1.7 km depth. These features of the induced seismicity disregard pore pressure buildup as the triggering mechanism. Our analyses show that seismicity was induced by gas injection, which reactivated the critically stressed Amposta fault. The Amposta fault, which bounds the storage formation, is a mature fault with very low permeability as a result of clay accumulation into its core resulting from its 1,000-m offset. Pore pressure buildup, but specially buoyancy of the gas, which continued to act after shutin, destabilized the Amposta fault aseismically. The accumulation of aseismic slip caused stress transfer, destabilizing a deep critically stressed fault. Subsequently, shear slip stress transfer combined with slip-driven pore pressure changes, induced the sequence of felt earthquakes. We conclude that the induced earthquakes at Castor could have been avoided because fault stability analysis reveals the high risk of inducing seismicity.

International audience; Polymorphic transformations are key tracers of metamorphic processes, also used to estimate thepressure and temperature conditions reached by a rock. In particular, the quartz-coesite transitionis commonly used to define the lower boundary of the ultrahigh-pressure (UHP) metamorphicfield. The partial preservation of coesite included in garnets from UHP rocks bring considerableinsights into the burial and exhumation mechanisms of the continental crust involved inconvergent zone. Coesite was first described in the Western Alps by Chopin[1], in the Dora-Mariawhiteschist, one of the most emblematic UHP rock worldwide. Although the partial preservation ofcoesite inclusions in garnet has long been attributed to the pressure vessel effect, theinterrelationship and relative timing between fracturing and retrogression is still contentious.Here we study the reaction-deformation relationships of coesite inclusions initially enclosed ingarnet and transforming into quartz during the decompression process. We combine 2Dnumerical thermo-mechanical models constrained by pressure-temperature-time (P-T-t) estimatesfrom the Dora-Maira whiteschist. The model accounts for a compressible visco-elasto-plasticrheology including a pressure-density relationship of silica based on thermodynamic data. Thisallows us to study the effect of reaction-induced volume increase during decompression. Ourresults capture the typical fracture patterns of the host garnet radiating from retrogressed coesiteinclusions and can be used to study the relative role of volume change associated with a change ofP-T conditions on the style of deformation during decompression.The mechanisms of the coesite-quartz transformation and geodynamic implications are presentedand validated against geological data. The effect of fluids on the phase transition and theconditions of access of fluids during the transformation are discussed in the light of the results ofthe thermo-mechanical models.This study demonstrates the high potential of thermo-mechanical modelling in enhancing ourunderstanding of the processes involved in the formation and evolution of metamorphic minerals.[1]Chopin (1984) Contributions to Mineralogy and Petrology 86, 2, 107-118

Poster réalisé par l'Institut de recherche pour le développement et le laboratoire Hydrosciences Montpellier; International audience; At the African scale, there is a lack of coordination for hydrological data collection and dissemination : hydrological data is often scattered, heterogeneous or incomplete Numerous public, semi-public and private organizations produce and manage data, but often they do not have the resources to exchange, standardize, summarize and apitalize on the data they generate There is not enough partnership between the national hydrological services, in many countries licensing issues prevent the distribution of the data collected. There is also a more general problem of a widespread reluctance to share information There is need to develop links between data producers and users to reinforce capacities for accessing, processing and take benefit from existing data.As a consequence, the African continent is largely under-represented in global scale studies.

Arctic extensively urbanized centers are subject to the impact of many negative environmental phenomena progressing in terms of global climate change and regional development in Yakutia in the context of poor and missing databases. For this reason, the modeling of the risk exposures is based on combining the remote sensing, and local knowledge of inhabitants. According to the occurrences of the natural hazards, the territorial management and the decision-making system require the identification and assessment of natural risks to which the rural populations localized in the towns and villages are exposed, for example, in the urban center of Khamagatta located at 70km to the North from Yakutsk near the Lena River. The main environmental vulnerability exposures are seasonal: springtime floods between May and June, the forest fires from June to August, the cyclic permafrost degradation, and river erosion impacts.The current vulnerability impacts, damages to the lands and the settlements, and the populations risk exposures are analyzed from the maps of vulnerabilities created from remote sensing satellite Sentinel 2A/B series, with the local knowledge of the inhabitants of Khamagatta who lived and perceived all events. All the data generated, maps, models of vulnerability exposures, and local knowledge are integrated, combined, and merged into the geographic information system (GIS). The GIS modeling combines the risk of natural hazards and the damages, and the risk knowledge and perceptions of the inhabitants. Land uses, Landscape classification, and the land cover is made by Object-Based Image Analysis (OBIA) using an optical time series of Sentinel 2 images (2015-2020) including the population knowledge for the recognition of the environmental vulnerabilities. The methodological approach included the participation of local people in workshops through discussion and participatory mapping, questionnaires, and interviews in two stages. The first stage included the development of the knowledge database for a comprehensive understanding of the life of the local population, including the forms of adaptation to the negative natural phenomena. The collected information is delocalized and integrated into the GIS. The second stage consisted of validation and discussion, including stakeholders (municipality and rescue services) to increase the reliability and legitimacy of the research results.Perceptions of the inhabitants of Khamagatta are correlated with the maps of risk exposures generated by remote sensing to increase the accuracy of the environmental process modeling and landscape classification. The combination of the environmental change dynamics, the impacts on the towns and villages with the human perception and experience constitutes the main base supporting the prevention mapping of the natural hazards. This data could be very useful in planning the development of Arctic towns and villages and proposing evolution scenarios and urban planning models and strategies for increasing their resilience and adaptation to climate change consequences.

We investigate how geomorphological structures shape Transit Time Distributions (TTDs) in shallow aquifers. We show that the TTD is determined by integrated features of the groundwater structure and of the repartition of seepage in convergent/divergent hillslopes of constant slope. More specifically, the coefficient of variation of the TTD (standard deviation divided by the mean) scales linearly with the mean distance of the groundwater volume to the river. The extent and structure of seepage modify the groundwater contribution to the transit time distribution and increase its variability.Extensive 3D simulations were performed to determine the TTDs synthetic convergent, straight and divergent hillslope models of constant slope. The recharge was applied uniformly on top of the aquifer and transferred to the receiving stream through steady-state groundwater flows, return flows and saturation excess overland flows. Without seepage, TTDs evolve from uniform- to power law-like- distributions depending on the average distance of the groundwater volume to the river. Remarkably, the coefficient of variation of the TTDs scales linearly with the groundwater volume to the river at any hillslope convergent/divergent rate in agreement with a theoretical prediction based on three analytical approximations. With seepage, the TTD progressively displays three separate modes corresponding (1) to the rapid saturation excess overland flows, (2) to the intermediary circulations ending up in seepage area and (3) to the slower circulations going from a recharge upstream the seepage zone to a discharge in the river. The coefficient of variation additionally depends on the extent of the seepage area.Applied to a natural hillslope in the crystalline basement of Normandy (France), the same synthetic analysis demonstrates that the coefficient of variation is not only determined by the extent of the seepage zone but also by its structure in relation to the geomorphological local and global organizations. These results suggest the possibility to assess the variability of transit times by combining geomorphological analysis, surface soil saturation observations and environmental tracers.

Solute mixing mediated by flow in porous media plays a significant role in controlling reaction rates in subsurface environments. In many practical cases, incomplete mixing—inhomogeneous solute concentrations—occurs at the pore-scale, limiting local and thus upscaled reaction rates, and renders their prediction based on effective dispersion coefficients derived from dispersion models (or by assuming Taylor-Aris dispersion) inaccurate. We perform solute transport experiments in transparent, quasi-two-dimensional, soil analog models to investigate the relationships between pore-scale solute dispersion and mixing under different flow conditions. We use Fluorescein as a conservative tracer and record its fluorescence intensity in monochrome images at fixed time intervals. We convert the fluorescence intensity to solute concentration fields based on a calibration curve obtained with various homogeneous solute concentrations and subsequently compute concentration gradients. Our images provide evidence for incomplete mixing at the pore-scale and show strong gradients transverse to the overall flow direction. We fit the mean longitudinal concentration profile to an analytical solution of the advection-dispersion equation and compute the effective longitudinal dispersion coefficient. Based on the lamellar mixing theory, we also infer an effective diffusion coefficient relevant to the mean concentration gradient’s dynamics. By comparing these two diffusion/dispersion coefficients in saturated flow conditions, we show that while their values are similar at low Péclet, their scaling behaviors as a function of Péclet are different. Hence, as pointed out by several previous studies, modeling reactive transport processes requires accounting for a mixing behavior driven by a diffusive process that cannot entirely be described by the solute dispersion coefficient. We extend this work by varying the saturation degree in the experiments and our samples' structural heterogeneity to investigate how flow desaturation and porous medium structure impact solute mixing.

Landforms and channel networks have long been analysed through co-variation between topographic slope and drainage area, which is derived from easy-to-implement flow routing algorithms (D8 or Dinf) relying on topographic slopes. The slope-area relationship has been successful to identify morphologic regions in landscapes likely reflecting the erosion and transport processes that shape them. But the implicit assumption for using the slope-area relationship is that channels are narrower than the DEM resolution and that, at this scale, the flow is correctly routed. These assumptions are no more valid for very high-resolution DEM (HRDEM, In this study, we propose a new topographic analysis relying on realistic hydraulic simulations of surface flow. For this, we use a particle-based hydraulic model, Floodos, which solves the 2D shallow water equations, and we present an analysis of the 1m LiDAR DEM of the Elder creek watershed in California, for which channels are up to ten meters wide. By simulating channel flows with water depth, hydraulic slope, specific discharge and bed shear stress, the hydraulic model reveals landscape patterns that are not described by the slope-area relationship. Additionally, the flow model handles very well the small irregularities of the topography.We introduce new geomorphic descriptors: the hydraulic slope and the specific drainage area (or specific discharge). The catchment organization is then analysed through a new framework called the hydraulic slope-area diagram. This diagram has several benefits over the classical slope-area diagram. It correctly classifies pixels located in the river for a given discharge in the fluvial domain leading to a sharper transition between the colluvial and fluvial domain. The hillslope-to-valley transition is also insensitive to the DEM resolution. Channel width can also be automatically calculated based on a joint analysis of Dinf and 2D shallow water simulation. Finally, the capability to perform the hydraulic slope-area for various discharges brings a richer description of landscape organization by highlighting discharge-dependent regions such as floodplain areas and fluvial terraces.

International audience; The evolution of sedimentary landscapes is primary driven by the interplay between the rate ofaccommodation creation A, controlled by sea-level and subsidence, and the rate of sedimentsupply S, controlled by erosion and sediment transport. In simple terms, the balance between Aand S can be used to predict periods of progradation (when sediment supply exceedsaccommodation) and periods of retrogradation (when accommodation exceeds sediment supply).However, a growing list of observations show that internal feedbacks within the sedimenttransport system can generate large-scale, autogenic stratigraphic patterns that are notanticipated by the A/S theory. These observations call for a reanalysis of several sequencestratigraphic precepts that assume a deterministic relationship between external forcings andstratigraphic products. Here, we focus on the filling of incised valleys during constant sea-levelrise, and by a constant sediment flux. We develop a simple conceptual model of valley filling andwe show that the classic sequence stratigraphic phenomenon of bayhead deltaic systems can begenerated by purely autogenic progradation during the late stage of valley flooding. This transient“auto-advance” event results from a strong decrease of in-valley accommodation as base-levelrises towards the valley apex. To test this model, we build a laboratory experiment thatsuccessfully reproduces the dynamics predicted by the model. Finally, we apply our model to twosimilar field examples, the Trinity and Brazos rivers incised valleys (Texas, USA). There systems arebroadly similar in dimension and sea-level history but were filled at different sediment rates. Wepropose that this led to auto-advance event in the Trinity River valley while no advance is observedin the Brazos system. We thus show by conceptual, experimental and natural examples that auto-advance can produce out-of-sequence regressive bayhead diastems during highstands similar to atransient change in allogenic forcing. Combined with other recent studies, our findings support theidea that meso-scale autogenic patterns are ubiquitous in the fluvio-deltaic record, and need to bemore extensively incorporated into reconstructions of Earth surface evolution and reservoirmodels

International audience; The interval from the Valanginian to the Barremian stages (137–121 Ma; Early Cretaceous) ispunctuated by several episodes of environmental changes, accompanied by shifts in weatheringintensity on the continents and changes in the Tethyan neritic carbonate production. Wesynthetize here the astrochronology of two recent studies performed in the Neuquén basin,Vocontian Basin and Subbetic Domain (Aguirre-Urreta et al., 2019; Martinez et al., 2020), anchoredto CA-ID-TIMS U-Pb ages, which conclusions have been included in the Geologic Time Scale 2020(Gale et al, in press). We applied this time scale to a compilation of carbon-isotope ratio frombelemnites and proxies of detrital supply in the Tethyan area (Vocontian Basin and SubbeticDomain). From this compilation, we show that the episodes of environmental changes are pacedby a 2.4-Myr cycle and, with a lower amplitude, a 1.2-Myr cycle. In addition, the new time scaleshows the synchronicity between the Weissert Event and the Parana-Etendeka Large IgneousProvince. In the series of carbon-isotope ratios measured on belemnite rostra, the amplitude ofthe 2.4-Myr cycle is twice higher during the Valanginian than in the Late Barremian and threetimes higher than in the Hauterivian and Early Barremian, suggesting that the activity of theParana-Etendeka Large Igneous Province amplified the initial orbital forcing to trigger theenvironmental changes observed during the Mid-Valanginian.Reference:Aguirre-Urreta, B., Martinez, M., Schmitz, M., Lescano, M., Omarini, J., Tunik, M., Kuhnert, H.,Concheyro, A., Rawson, P.F., Ramos, V.A., Reboulet, S., Noclin, N., Frederichs, T., Nickl, A.-L., Pälike,H., 2019. Interhemispheric radio-astrochronological calibration of the time scales from the Andeanand the Tethyan areas in the Valanginian–Hauterivian (Early Cretaceous). Gondwana Research 70,104-132. https://doi.org/10.1016/j.gr.2019.01.006.Gale, A.S., Mutterlose, J., Batenburg, S., in press. Chapter 27: The Cretaceous Period, in: Gradstein,F.M., Ogg, J.G., Schmitz, M.D., Ogg, G.M. (Eds.) Geologic Time Scale 2020. Elsevier BV, Amsterdam,The Netherlands, pp. 1023–1086.Martinez, M., Aguado, R., Company, M., Sandoval, J., O’Dogherty, L., 2020. Integratedastrochronology of the Barremian Stage (Early Cretaceous) and its biostratigraphic subdivisions.Global and Planetary Change 195, 103368. https://doi.org/10.1016/j.gloplacha.2020.103368.

International audience; Sedimentary breccias formed during extensional tectonics are spatially associated with large-throw normal faults. They result from the creation of a steep topography that becomes unstable, producing major rockfalls. The studied breccias, in Crete and in the Pyrenees, are up to 300 meters thick and are characterized by poorly sorted polygenic deposits of pebbles to boulders composed of highly angular plurimillimetric to plurimetric carbonate clasts. A lateral evolution is observed, with pebble-size clasts found near the normal fault and boulder-size clasts away from the fault. This evolution is related to the rockfall process as the total kinetic energy acquired by the small clasts during the fall is lower than that acquired by the bigger ones; as a result, the latter are able to travel farther. Interestingly, the fact that the smallest clasts are proximal while the bigger ones are more distal is contrary to the distribution found in alluvial fan systems, making it possible to differentiate from one another. The studied breccias commonly show disorganized layers and/or no noticeable layering across large distances. We interpret this feature as related to the movement on the normal fault, which progressively tilts the breccia layers and favours their gliding along the slope. Gliding is an important internal process to take into account in rockfall systems because it may disorganize the layering, create specific geometries like onlap around olistoliths, and produce deformation inside the breccia layers; the latter feature could be mistakenly interpreted as resulting from post-deposition regional deformation.According to our observations, active normal faults with large throws provide the conditions for the formation and preservation of great volumes of sedimentary breccias through the following processes: i) footwall uplift, creating a pronounced topography with steep slopes, giving rise to major rockfalls, ii) hangingwall rapid subsidence, which allows the accumulation and preservation of the breccias without clast reworking by drainage systems. The latter is reinforced by the fact that, during the early stages of extension, the main watersheds point in a direction opposite to the fault slope whereas only small, discontinuously distributed watersheds flow in the direction of the fault slope. Upon ongoing extension, the size of these small watersheds increase. At one point, the sedimentary flow coming from these watersheds becomes more important than rockfall processes. Part of the breccia body is then eroded, reworked, and replaced by conglomerates of an alluvial fan deposited unconformably above the breccias.Summing up, sedimentary breccias are readily formed as thick syn-tectonic deposits during early stages of extensional basin development. Thus, they may be considered as a typical lithology, and a marker, of continental extension.

The Moroccan Anti-Atlas consists of a several kilometers thick sediment pile accumulated on the northern Gondwana platform since the latest Precambrian (Ediacaran). This study focuses on the Ktaoua Group, early Late Ordovician (Mid-Sandbian to Katian) in age, which records a major and multiphase transgressive/regressive cycle above the shallow marine sandstones of the underlying First Bani Group. In the western Central Anti-Atlas, the Ktaoua Group is formed by offshore shales to coastal sandstones organized in regressive parasequences. Here, high-resolution field-based stratigraphy is used to constrain the shelf architecture and clinoforms geometries within the Ktaoua Group.Whereas the lower part of the Ktaoua Group records parasequences from silty-shale to fine to coarse sandstones with hummocky-cross-stratification (HCS), its upper part oscillates between HCS beds and very coarse sandstones. Ferruginous, condensed horizons usually drape the parasequences. In this study, we investigate the platform geometry through the correlation of the stacking patterns of seventeen stratigraphic logs along an 85 km long, well-exposed cliff. Drone images support the logging and the correlations of the sections by imaging clinoforms geometries. Several decameters of fine to coarse sandstones can be observed to grade laterally into condensed level(s) within a few kilometers, hence evidencing clinoforms pinching out. The visible orientation of the clinoforms along the cliff exposures show a proximal to distal trend from the south-west to the north-east, in agreement with the overall basin geometry. Three clinoforms with distinct geometries and lateral evolution of facies associations are highlighted. The distal part of a clinoform, 15 m in thickness, pinches out onto the top of the underlying First Bani Group within 7 km. The overlying regressive parasequence, approximatively 50 m thick, remains consistent more than 50 km, and is understood as a prograding clinoform. A third clinoform, capped by a prominent sandstone body constantly thicker than 20 m over ca. 20 km, disappears within its last 3.5 km onto the underlying clinoform. This study offers new details on the progradation and regression geometries along a giant platform within a detailed stratigraphic framework.We would like to thank the Pacha and the Gendarmerie Royale of Foum-Zguid, the governor of Tata and the different persons who gave their approval and facilitated the use of the drone in the region of Souss-Massa for their precious help.

International audience; Widespread carbonate rocks from the Tibetan plateau have been extensively used to constrainterrane paleolatitudes involved in the India-Asia collision. However, their reliability in preserving aprimary magnetization has been recently put into question.A transformation of pyrite tomagnetite has been recently proposed as a cause for late re-magnetizations in Paleocene TethyanHimalaya carbonates (1) and late Triassic carbonates from the Qiantang (2), thus discarding suchCharacteristic Remanent Magnetizations (ChRM) for tectonic purposes. We have re-examined thepaleomagnetic data obtained on late Triassic carbonate rocks from the Qiantang. Our SEMobservations indicate pristine pyrite in non-weathered carbonate rocks. Optical microscopeobservations in reflected light demonstrate that pyrite, when it is weathered, is transformed toiron hydroxides minerals but not to magnetite. This is at odds with previously proposed pyrite tomagnetite transformation hypothesis mainly based on interpretations of Scanning ElectronMicroscope data (SEM/EDS). We thus interpret the ChRM more likely related to an early diageneticmagnetization of Late Triassic age. Knowing that the arguments put forward for a remagnetizationof Triassic carbonates are the same as those proposed for the remagnetization of Paleocenecarbonates, the ChRM in some Paleocene carbonates could also be of early diagenetic origin.However, there is also a growing number of studies where remagnetization is obvious in theTethyan Himalaya and undetected remagnetizations (3) are likely the cause of the largedifferences in the estimation of the size of Greater India. These examples show the urgent need topublish the complete demagnetization dataset in an open database like MAGIC or the FAIR datainitiative from (4) in order to reassess previous interpretations if we want to solve problems likethe size of Greater India and hypothesis like the Greater India basin

Ultrahigh-pressure (UHP) continental crustal rocks were first discovered in the Western Alps in 1984 and have since then been observed at many convergent plate boundaries worldwide. Unveiling the processes leading to the formation and exhumation of (U)HP metamorphic crustal rocks is key to understand the geodynamic evolution of orogens such as the Alps. Previous numerical studies investigating (U)HP rock exhumation in the Alps predicted deep (>80 km) subduction of crustal rocks and rapid buoyancy-driven exhumation of mainly incoherent (U)HP units, involving significant tectonic mixing forming so-called mélanges. Furthermore, these predictions often rely on excessive erosion or periods of divergent plate motion as important exhumation mechanism. Inconsistent with field observations and natural data, application of these models to the Western Alps was recently criticised. Here, we present models with continuous plate convergence, which exhibit local tectonic-driven upper plate extension enabling compressive- and buoyancy-driven exhumation of coherent (U)HP units along the subduction interface, involving feasible erosion. The two-dimensional petrological-thermo-mechanical numerical models presented here predict both subduction initiation and serpentinite channel formation without any a priori prescription of these two features. The (U)HP units are exhumed coherently, without significant internal deformation. Modelled pressure and temperature trajectories and exhumation velocities of selected crustal units agree with estimates for the Western Alps. The presented models support previous hypotheses of synconvergent exhumation, but do not rely on excessive erosion or divergent plate motion. Thus, our predictions provide new insights into processes leading to the exhumation of coherent (U)HP crustal units consistent with observations and natural data from the Western Alps.

International audience; In the former Cordex program, regional climate models were run over Africa and only covered the western part of the South Indian Ocean at a coarse 50-km resolution while a 12-km resolution was used for Europe. A 50-km resolution is insufficient for island territories as small and steep as those in the Indian Ocean. Yet this area is especially vulnerable to natural catastrophes related to the effects of climate change: it is the third region in the world most affected by extreme climatic events. The need for climate services over that populated area has now become a critical issue. Both dynamical and statistical downscaling from a few ongoing CMIP6 simulations were therefore used to obtain regional climate information on a large area of the southwest Indian Ocean that includes most of the inhabited countries from the coasts of Mozambique (33°E) to 74°E as well as the main area of tropical cyclone genesis [2-28°S]. The limited area model ALADIN was implemented in its climate version at 12-km resolution and the first runs were coupled by outputs from one of the CMIP6 Earth Simulation Coupled Models named CNRM-ESM2-1. We will present the numerical and statistical tools used for this regional climate study as well as the first projections obtained for ssp126 (RCP2.6), ssp245 (RCP4,5) and ssp585 (RCP8.5) scenarios over the 2015-2100 period. Results will be illustrated for the southwest Indian ocean basin as well as for the main islands of the IOC member countries: Madagascar, Reunion, Mauritius, Seychelles, and Comoros where observations over the 1981-2010 period were used for model bias correction using the quantile-quantile matching method. For climate uncertainty representativeness, the 2015-2100 evolution of both ALADIN and CNRM-ESM2-1 temperature and precipitation averages over our region will be compared to that of the other available CMIP6 simulations. This work is part of the BRIO (Building Resilience in the Indian Ocean) project which aims at supporting the Indian Ocean Commission (IOC) member countries in the implementation of their adaptation policies with respect to climate change (regarding water resources, health and other issues). This project will provide a set of high quality climate-related data on a free-access online regional portal as well as climate services. It is funded by the Agence Française de Développement (AFD), through the Adapt’Action Facility, in cooperation with the IOC.

International audience; Hydraulic tomography is a state of the art method for inferring hydraulic conductivity fields using head data. Here, a numerical model is used to simulate a steady-state hydraulic tomography experiment by assuming a Gaussian hydraulic conductivity field (also constant storativity) and generating the head and flux data in different observation points. We employed geostatistical inversion using head and flux data individually and jointly to better understand the relative merits of each data type. For the typical case of a small number of observation points, we find that flux data provide a better resolved hydraulic conductivity field compared to head data when considering data with similar signal-to-noise ratios. In the case of a high number of observation points, we find the estimated fields to be of similar quality regardless of the data type. A resolution analysis for a small number of observations reveals that head data averages over a broader region than flux data, and flux data can better resolve the hydraulic conductivity field than head data. The inversions' performance depends on borehole boundary conditions, with the best performing setting for flux data and head data are constant head and constant rate, respectively. However, the joint inversion results of both data types are insensitive to the borehole boundary type. Considering the same number of observations, the joint inversion of head and flux data does not offer advantages over individual inversions. By increasing the hydraulic conductivity field variance, we find that the resulting increased non-linearity makes it more challenging to recover high-quality estimates of the reference hydraulic conductivity field. Our findings would be useful for future planning and design of hydraulic tomography tests comprising the flux and head data.

Western Europe experienced a major rift system initiated during Bartonian times (41 Ma). This evolution is coeval with long wavelength deformations (several hundreds of kilometers) that control the topography and the sediment production beyond the rift. The climate during this time interval was first increasingly arid and then wetter.This study is based on both landform and sediment analysis of southern England, France, Belgium and western Germany. The landforms are mainly large pediments, dated by the intersection with sediments deposited in low to high subsiding areas and volcanism. A set of paleogeographic maps with paleotopographic reconstructions, is used to constrain the uplifting and subsiding areas, their wavelength and the critical periods of intraplate deformations.The main periods of deformations and sedimentary systems changes area as follow.41Myrs (base Bartonian) was the beginning of a major tilting of Western Europe with subsidence of France and uplift of the Brabant/Ardennes/Rhenish Massif. Even a dense network of basement faults was reactivated, biochemical sedimentation prevailed.35-31Myrs (Late Priabonian-Early Rupelian) initiated a period of general subsidence even along the Ardennes/Rhenish Massif and the French Massif Central. Two major marine floodings are recorded, with a differential preservation according to the balance between deformation and eustasy.27-25Myrs (Chattian) was a period of uplift of Western Europe except the Aquitaine Basin, followed by a relaxation favoring eustatic floodings in (very) low subsiding domains. Chattian siliciclastic deposits are preserved as lowstand wedges in the surrounded basins (North Sea, Atlantic Margin).14-11Myrs (Serravallian-Early Tortonian) initiated the overall uplift of Western Europe, still operating today. This is the beginning of a period of major denudation in southern England, Western Germany (SW Germany flat - “Stufenland”) and along the southern limb of the Franch Massif Central.The causes and the consequences in term of sediment production are discussed.

Deep groundwater circulation increases multiplicity and complexity of groundwater pathways providing a high diversity of intrinsic water properties. Water-rock interactions at depth associated with transit time disparities generate singular mineralisation with high temperature, notable dissolved ions and significant gaseous content. As shown in literature, deep processes involved in gas release can be deduced from fluid gas composition collected at the surface. Widely used as tracers in volcanic areas, seismically- and tectonically-active regions, the gaseous emission monitoring is underused to understand the regional and local groundwater flow patterns that are not linked to an active zone. In order to refine knowledge on complex flow organisation at the origin of diversified mineral springs, this study aims to experiment the use of dissolved gaseous components as a tracer of water up flows interactions.The oriental plain of Corsica (France) has been chosen for its wide variety of mineral waters (22 springs) emerging at the interface of magmatic (Hercynian orogenesis), metamorphic (Alpine orogenesis) and sedimentary rocks (from the Alpine orogenesis and from Neogene deposits). Dissolved reactive (N2, CO2, CH4, H2S, H2, O2) and noble gases (Ne, Ar, He) on 9 springs have been quarterly sampled (April, July, September & December 2018), and analysed by gas chromatography (µGC).The first results highlight 3 very contrasted gas abundances:(1) N2-rich thermal waters (54°C), poorly mineralised, with noble gas occurrence as cortege gases. This highlights the influence of deep flow with a long groundwater residence time. (2) CO2-rich cold waters (2 as cortege gase. This highlights the occurence of deep flow interacting during his upflow with carbonates of metamophosed rocks. (3) CH4-rich cold waters (2S and CO2 as cortege gases. This highlights biotic anaerobic activity involvement in gases composition of the mineral waters. Then, based on the observed abundance of noble gases, theoretical recharge conditions were computed to defined recharge temperature, air- and He-excess. Computation results have stressed out the common origin of these three gas, depending on flow paths, reservoir conditions, biotic and abiotic interaction involvement. The circulation within magmatic reservoir is responsible for the deep N2-rich flow, which shows during his up flow abiotic interactions with metamorphised carbonates rocks, increasing the CO2 content in water. Then under anoxic geological confinement in deep sedimentary layers, the CO2 is reduced into CH4 and N2 into NH4. In the shallowest sedimentary layers, CH4 formed is degraded, due to the occurrence of rich-organic matter lithology, by biotic activity into H2S.This monitoring substantially contributes to improving the complex hydrogeological model of Corsican mineral springs, highlighting the link between deep regional and local groundwater flow; whose even of the non-conventional tools doesn’t succeed in clearly testified about the deep escape mechanisms of natural fluids in this non-volcanic regions. In absence of current volcanism, seismic- or tectonic-activity, monitoring the dissolved gases releasing at the surface by thermo-mineral springs provides fundamental information about deep and complex flow paths.

Volatile Organic Compounds (VOCs) have direct influences on air quality and climate. They also play a key role in atmospheric chemistry, as they are precursors of secondary pollutants, such as ozone (O3) and secondary organic aerosols (SOA).Long-term datasets of in-situ atmospheric measurements are crucial to characterize the variability of atmospheric chemical composition. Online and continuous measurements of O3, NOx and aerosols have been achieved at the SIRTA-ACTRIS facility (Paris region, France), since 2012. Regarding VOCs, they have been measured there for several years thanks to bi-weekly samplings followed by offline Gas Chromatography analysis. However, this method doesn’t provide a good representation of the temporal variability of VOC concentrations. To tackle this issue, online VOC measurements using a Proton-Transfer-Reaction Quadrupole Mass-Spectrometer (PTR-Q-MS) have been started in January 2020.The dataset acquired during the first year of online VOC measurements is analyzed, which gives insights on VOC seasonal variability. The additional long-term datasets obtained from co-located measurements (O3, NOx, aerosol physical and chemical properties, meteorological parameters) are also used for the sake of this study.Due to Covid-19 pandemic, the year 2020 notably comprised a total lockdown in France in Spring, and a lighter one in Autumn. Therefore, a focus can be made on the impact of these lockdowns on the VOC variability and sources. To this end, the diurnal cycles of VOCs considered markers for anthropogenic sources are carefully investigated. Results notably indicate that markers for traffic and wood burning sources behave quite differently during the Spring lockdown in comparison to the other periods. A source apportionment analysis using positive matrix factorization allows to further document the seasonal variability of VOC sources and the impacts on air quality associated with the lockdown measures.

Intracrystalline diffusion is an efficient mechanism in high-grade rocks. Therefore, growth zoning in garnet is erased and the evidence for prograde path is lost. However, information recorded by the textures may store significant clues for deciphering part of the P-T path. An example is provided here from the migmatitic paragneisses from the Mont Mary nappe (Western Alps).The latter is made of a pre-Alpine basement consisting of an upper and a lower unit. The upper unit is made of paragneisses, marbles and amphibolites similar to those of the Valpelline Unit and of the Ivrea Zone. The lower unit displays granitic orthogneisses, paraschists (with muscovite, biotite, garnet with local occurrences of staurolite, kyanite and andalusite) (Dal Piaz et al. 2015). In this unit, we discovered a hectometre-sized volume with no Alpine overprint, preserving migmatitic paragneisses, the topic of this study.The paragneisses display quartzo-feldspathic leucocratic layers interpreted as crystallized melts. The leucosomes are separated by biotite- and sillimanite-rich layers, with conspicuous garnet porphyroblasts. In addition, fresh cordierite crystals are found in these layers. Sillimanite included in garnet rims has the same orientation than the one in the matrix. There, the foliation is defined by the shape fabric of biotite and sillimanite, wrapping both garnet and cordierite crystals.Such textures may be used to propose a P-T path. A sequence of prograde reactions, including dehydration-melting of muscovite, then biotite, result in the production of a large amount of sillimanite. Garnet growth was continuing during incongruent melting. However, intracrystalline diffusion has erased the prograde chemical zoning, as well as the distribution and shape of mineral inclusions. The late replacement of garnet and cordierite by biotite and sillimanite indicates near-isobaric cooling, also recorded by chemical zoning along garnet rims.Chemical data on coexisting minerals will be used to provide quantitative constraints on the P-T path. In addition, preliminary geochronological data suggest that detrital zircons grains were significantly reset during the HT metamorphism, which could have taken place c. 270 Ma ago. To conclude, the studied paragneisses offer another example of Permian near-isobaric cooling in the middle crust of the Adriatic plate.Dal Piaz G.V., Bistacchi A., Gianotti F., Monopoli B., Passeri L., Schiavo A. & collaboratori (2015) – Note illustrative della carta Geologica d’Italia alla scala 1:50.000. Foglio 070, Monte Cervino. ISPRA, Servizio Geologico d’Italia, 070, 1-431.

Understanding and simulating the soil organic matter had become a key challenge to better predict the landscape dynamic and its evolution. Although numerical modelling developments already integrate soil organic matter to improve agricultural practices at field or plot scales, additional work needs to be carried out to describe the landscape evolution over hundreds to thousands of years.We aim to identify and quantify the processes associated to organic matter cycle that take part in landscape long-term evolution. We complete a reference sediment transport model designed for large scale evolution by adding some physical considerations relative to organic matter behaviour. The main developments concern: Organic matter productivity and its export to soils Organic matter evolution and degradation along soil profile and during transport Rock and regolith compartments with different lithologies and compositions Weathering and erosion In this presentation, we explore the strengths and limits of this model designed to address a wide variety of questions in various settings. We also discuss the results and assess the validity of this approach considering availability of long-term sedimentary records.

The spatial distribution of a solute undergoing advection and diffusion is impacted by the velocity variability sampled by tracer particles. In spatially structured velocity fields, such as porous medium flows, Lagrangian velocities along streamlines are often characterized by a well-defined correlation length and can thus be described by spatial-Markov processes. Diffusion, on the other hand, is generally modeled as a temporal process, making it challenging to capture advective and diffusive dynamics in a single framework. In order to address this limitation, we have developed a description of transport based on a spatial-Markov velocity process along Lagrangian particle trajectories, incorporating the effect of diffusion as a local averaging process in velocity space. The impact of flow structure on this diffusive averaging is quantified through an effective shear rate. The latter is fully determined by the point statistics of velocity magnitudes together with characteristic longitudinal and transverse lengthscales associated with the flow field. For infinite longitudinal correlation length, our framework recovers Taylor dispersion, and in the absence of diffusion it reduces to a standard spatial-Markov velocity model. This novel framework allows us to derive dynamical equations governing the evolution of particle position and velocity, from which we obtain scaling laws for the dependence of longitudinal dispersion on Péclet number. Our results provide new insights into the role of shear and diffusion on dispersion processes in heterogeneous media.In this presentation, I propose to discuss: (i) Spatial-Markov models and the modeling of diffusion as a spatial rather than temporal process; (ii) The concept of the effective shear rate and its role in the diffusive dynamics of tracer particle velocities; (iii) The role of transverse diffusion and its interplay with velocity heterogeneity on longitudinal solute dispersion.

Tectonics, climate and surface processes dictate the evolution of Earth’s surface topography. Topographic change in turn influences lithospheric deformation, but the temporal and spatial scales at which this feedback can be effective remains an open issue. Here, we make a synthesis of recent developments investigating how erosion impacts the stress-loading of faults and potentially induces some earthquakes. We first show, using an elastic model for the lithosphere, that erosion rates of ca 0.1–20 mm.yr−1, as documented in active compressional orogens, can raise the Coulomb stress by ca 0.1–10 bar on the nearby thrust faults over an earthquake cycle, by changing both the normal and tangential stress. This model also suggests that short-lived but intense erosional events can represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Indeed, we demonstrate that typhoon Morakot in 2009, which triggered numerous landslides, was followed by a step increase in the shallow (

At the interface between aquifers and rivers, hyporheic zones are shallow sediment layers where surface and subsurface waters mix and react. In these zones, the dynamic of solute transport and mixing is a crucial and limiting component for many biogeochemical reactive processes (arsenic and nitrates degradation for instance). In particular, the understanding of the consequence of flow path heterogeneity on solute mixing and reactivity is key to develop physically-based upscaled models of the hyporheic function. By simulating the evolution of reacting fronts under simple 2D and 3D heterogeneous hyporheic flows created by bed superficial pressure gradients, we show that incomplete mixing of reacting solutes systematically precludes the use of macro-dispersion models as upscaled models of the hyporheic function, both in steady and unsteady flow conditions.Based on these simulations, we propose an alternative theoretical framework, based on the concept of solute lamellae stretched by flow velocity gradients, to correctly upscale local reaction rates at the reach and basin scale. Finally, we compare our numerical and theoretical results to reacting fronts in a laboratory scale hyporheic mixing experiment.

International audience; As secondary organic aerosols (SOA) largely contribute to the mass of particles and may strongly affect health, it is essential to represent them as accurately as possible in air quality models (AQM). Their formation and aging involve multi-generation oxidations of numerous volatile organic compounds (VOC) combined with gas-particle partitioning processes.Tracking the non-linear relationship between VOC emissions and aerosol formation demands comprehensive chemical mechanisms, which take into account the whole complexity of the SOA precursor oxidation to simulate aerosols under various conditions.However, the use of explicit gas-phase chemical mechanism (e.g., MCM, GECKO-A) or molecular structure-limited parameterization (e.g., VBS, SOM, FGOM) could be problematical in large-scale SOA modeling, as the former is overwhelmingly computational expensive while the latter loses tracks of VOC oxidation products after few generations and specific properties relying on aerosol formation.Consequently, we have developed semi-explicit SOA chemical mechanisms designed to model the SOA formation and evolution in 3D AQM. These mechanisms are reduced based on simulations of the near-explicit master chemical mechanism (MCM) performed under various conditions representative of ambient conditions and different lumping strategies. The new mechanisms integrate the crucial SOA species/reactions with different mechanism complexities. The mechanisms, therefore, preserve the complexity of the oxidation chemistry (dependence on NOx of the SOA formation, the influence of radical concentrations, humidity, photolysis, etc..) as well as the molecular composition of the organic aerosol. The mechanisms are implemented in a novel 0D aerosol model SSH-aerosol, which can use the molecular structure of lumped compounds to estimate the influence of non-ideality on SOA formation.The current application has been conducted on the MCM degradation scheme of beta-caryophyllene (C15H24), the most representative sesquiterpene. A reduction of the average 90% CPU time and up to 92% number of S/IVOCs species has been achieved compared to the original MCM mechanism.

International audience; Anthropogenic gas tracers such as CFC, SF6, 85Kr, 36Cl or 3H have been widely used to study shallow groundwaters with residence time of less than 70 yr. For longer groundwater residence time (100- x1000 yr), 39Ar, 14C, 36Cl and 4He have been used. 4He can cover a dating range of 10 to thousands of years (Solomon et al., 1996). The main difficulty is to estimate the production rate through U and Th decay and the others fluxes: atmosphere, lithosphere and asthenosphere. In many cases U-Th production is not sufficient to explain the 4He concentrations observed in the aquifer. Other 4He fluxes can then be estimated through the use of other tracers: 14C, 36Cl or modeling. Fracturing may also enhance 4He concentrations in groundwater.We present here the evaluation of 4He in a crystalline fractured aquifer in the Northwest of France (H+ national hydrogeological network), in order to investigate the range of groundwater residence time in this complex shallow aquifer. Previous studies on this aquifer reveal mixing between young (1000 yrs) (Ayraud et al., 2008). The Helium radiogenic production rate is then evaluated through in situ production (U, Th, porosity), calibration with CFC and 14C, and modelling of the diffusion processes affecting 14C and 4He through physical characteristics of the aquifer (porosity, fracture spacing and aperture). Young groundwater residence times estimated by 4He agree with those estimated by CFC and 3H/3He. In this fractured media, old groundwater residence times (> 100 yr) are better estimated through the integration of the mass transfer between the fractures and the porous rock matrix through diffusion processes. 4He proves to be a valuable tool to characterize groundwater mixing processes and groundwater residence times from a decade to thousands of years.Solomon, D. K., Hunt, A., & Poreda, R. J. (1996). Source of radiogenic helium 4 in shallow aquifers: Implications for dating young groundwater. Water Resources Research, 32(6), 1805-1813.Ayraud, V., Aquilina, L., Labasque, T., Pauwels, H., Molenat, J., Pierson-Wickmann, A. C., ... & Fourre, E. (2008). Compartmentalization of physical and chemical properties in hard-rock aquifers deduced from chemical and groundwater age analyses. Applied geochemistry, 23(9), 2686-2707.

Meteorological considerations of grapevine damage due to temperature variations: the 2019 late spring frost and summer heat wave events in Burgundy During 2019, the occurrence of two contrasting weather events, a cold snap and a heat wave, caused extensive damage to the vineyards of Northern Burgundy. The late spring cold snap, that occurred from May 5th to 7th, generated frost like conditions across the northern and north-western areas of the Côte-d'Or department. The weather stations of the Northern Auxois area, where the three observation and study sites are located, recorded minimum temperatures ranging between -1 and -2°C. On the 24th and the 25th of July vineyards were exposed, yet again, to an extreme temperature variation. A brief but unusually intense heat wave increased daily maximum temperatures up to 42°C in the department’s far north. Landforms such as plateaus were less exposed to the increase in temperatures due the limiting effect of higher elevations. This led to temperatures not exceeding 40°C above 300 m, elevation at which the vineyard sites of this study are located.Weather conditions that caused the early May frost event were related to a northern circulation present over Western Europe that persisted from the 28th of April to the 6th of May. The strong anticyclonic ridge stretching from Greenland to the Iberian Peninsula directed an air mass of arctic origin towards France. On July 24th and 25th, the presence of a surface high pressure system above Scandinavia, associated with a low-pressure center located near the Atlantic Ocean, generated an influx of a very hot air mass from the northern part of the African continent through France and neighbouring countries.The local impact of these two weather events was modulated by the topographical features specific to the study area: a limestone plateau strongly dissected by parallel valleys of S.E. / N.W. orientations. The three observation sites have similar soil characteristics and are located on south facing slopes. However, damage to vegetation was uneven across sites as well as within each site. These observations rise up the question of the influence of very fine-scale environmental conditions and the impact they might have on the different vegetative growth stages. Lastly, the variation in physiological response among grapevines and its effect on their sensitivity to the occurrence of different weather hazards is also to be considered.

In a near future, the Sahara and Sahelian regions could experience more rainfall than today as a result of climate change. Wetter conditions in the hottest and driest place of the planet today raise the question of whether the near future might hold in store environmental transformations, particularly in view of the growing human-induced climate, land-use and land-cover changes. Reflecting an enhancement of the global hydrological cycle under warmer conditions, some experiments provide support for the notion of a strengthening of the monsoon in the future and more rainfall in central Sahel and Sahara. However, some remote forcing could counterbalance the decadal trend. Modeling experiments suggest that the freshwater discharge coming from Greenland melting could significantly impact the sea surface temperature of North Atlantic and induce a decrease in Sahel rainfall for the next decades, remaining left open the question how Sahara will be in a warmer climate?By chance, Lake Chad, located at the southern edge of the Sahara, is recognized for being the best site in Africa for deciphering hydrological and climate change. After being ranked at the world’s sixth largest inland water body with an open water area of 25,000 km2 in the 1960s, it shrunk dramatically at the beginning of the 1970s and reached less than 2000 km2 during the 1980s, decreasing by more 90% in area. Because it provides food and water to 50 millions of people, it becomes crucial to observe precisely its hydrological cycle during the last 20 years.Here by using a new multi-satellite approach combined with ground-based observations, we show that Lake Chad extent has remained stable during the last two decades, slightly increasing at 14,000 km2. We extend further this reconstruction by adding new data from the hydrological year 2019-2020, which is considered at an extreme in precipitation recorded over the Sahel. Moreover, since the 2000s, groundwater which contributes to 70% of Lake Chad’s annual water storage, is increasing due to water supply provide by its two main tributaries draining a catchment area 610,000 km2 wide. Because the current climate change seems to be characterize by a higher interannual variability affecting from year to year the amount of precipitation during the rainy season and increasing the vulnerability of the economy of the region mainly based of agropastoral activities, we investigate the yearly cycle and see how it is impacted the hydrological cycle of Lake Chad and changed over time.

Sediment archives in the terrestrial and marine realm are regularly analyzed to infer changes in climate, tectonic, or anthropogenic boundary conditions of the past. However, contradictory observations have been made regarding whether short period events are faithfully preserved in stratigraphic archives; for instance, in marine sediments offshore large river systems. On the one hand, short period events are hypothesized to be non-detectable in the signature of terrestrially derived sediments due to buffering during sediment transport along large river systems. On the other hand, several studies have detected signals of short period events in marine records offshore large river systems. We propose that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and signal propagation times. In this review, we (1) expand the definition of the term ���signal��� and group signals in sub-categories related to hydraulic grain size characteristics, (2) clarify the different types of ���times��� and suggest a precise and consistent terminology for future use, and (3) compile and discuss factors influencing the times of signal transfer along sediment routing systems and how those times vary with hydraulic grain size characteristics. Unraveling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy ��� a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records., Zweitver��ffentlichungen der Universit��t Potsdam : Mathematisch-Naturwissenschaftliche Reihe; 1230

The first Infrared Atmospheric Sounding Instrument (IASI) on the Metop satellites suite has achievedmore than 13 years of continuous operation. The instrument stability and the consistency between thedifferent instruments on the successive Metop (A, B and C) is remarkable and offer the potential toinvestigate trends in the concentration of various species better than with any other previous or currenthyperspectral IR sounder. The low noise of IASI radiances is also such that even weakly absorbingspecies can be identified, on single or at least on averaged spectra. In this work, we apply the so-calledwhitening transformation on IASI spectra, and show that it allows removing most of the climatologicalbackground from spectra, leaving a residual that contains those spectral signatures that depart fromnormality. These can subsequently be attributed to changes in the abundance of trace species. Byexploiting the first decadal record of IASI measurements, this method allows to (1) detect and monitorhalogenated compounds regulated by the Montreal protocol (CFCs) or used as substitutes (HCFCs,HFCs), as well as fluorinated compounds (CF?, SF?) and potentially short-lived chlorine species, forwhich substantial emissions are suspected (2) give a first assessment of the trend evolution of thesespecies over the 2008-2017 period covered by IASI on Metop-A. This is done by targeting variousgeographical areas on the globe and examining the remote oceanic and continental source regionsseparately. The trend evolution in the different chemical species, either negative or positive, is validatedagainst what is observed from ground-based measurement networks. We will conclude by assessing theusefulness of IASI and follow-on mission to contribute to global measurements of ozone depletingsubstances.

The main trigger for the Cretaceous/Paleogene boundary (KPB) mass extinction is still subject of intense debate. The co-occurrence of the Chicxulub impact (Yucatan, Mexico) and massive Deccan Traps volcanism (India) during Chron C29r hinders disentangling their climatic and environmental effects. Unravelling the influence of Deccan volcanism on the KPB extinction and other Maastrichtian and Danian perturbations requires more accurate age calibrations and duration estimates of biotic and climatic events. Here we integrate existing astrochronologies of the Zumaia section, allowing us to produce a refined cyclostratigraphic calibration of the main planktic foraminiferal and paleoclimatic events recorded across the KPB in the well-know Zumaia section (NW, Spain).At Zumaia, the KPB is marked by a ~8 cm-thick dark clay bed, with low values of %CaCO3 and δ13C. The Chicxulub ejecta-rich airfall layer has been identified at the base of the dark clay bed, but it is partially masked within a 1–2 cm-thick diagenetic calcitic layer. At Zumaia, the KPB has been astronomically calibrated at 66 Ma (compatible with radioisotopic ages), and the duration of dark clay bed is estimated at ~10 kyr. The first appearances (FA) of the Danian planktic foraminiferal index-species Parvularugoglobigerina longiapertura, Parvularugoglobigerina eugubina, Eoglobigerina simplicissima, Parasubbotina pseudobulloides, Subbotina triloculinoides and Globanomalina compressa have been orbitally tuned at Zumaia, to have occurred at 8, 30, 45, 70, 210, and 475 kyr after the KPB. Specimens of Plummerita hantkeninoides have been identified for the first time in the Maastrichtian of Zumaia, and its first occurrence is dated at ~100 kyr before the KPB. Based on d13C data, we have identified the late Maastrichtian Warming Event (LMWE), the early Danian Dan-C2 and the Lower-C29N events. Additionally, a bloom of the eutrophic/opportunist genus Chiloguembelitria, interpreted as a period of environmental stress, has also been recognized above and separate from the KPB clay bed. Besides the KPB, the main paleoclimatic/paleoenvironmental events have been astronomically calibrated at Zumaia as follows: the LMWE between 270 and 120 kyr before the KPB, the Dan-C2 event between 205 and 305 kyr after the KPB, the Lower-C29N event between 520 and 595 kyr after the KPB, and the Chiloguembelitria bloom between 100 and 305 kyr after the KPB. According to this chronology, we conclude that the LMWE and early Danian Chiloguembelitria bloom seems to coincide in time with major volcanic pulses of the Deccan Traps, unlike the Dan-C2 and Lower-C29N events, which appear to have been driven by orbital forcing. Regardless of the cause of climatic and environmental events, all these perturbations appear unrelated to the KPB mass extinction event. It supports the hypothesis that the influence of Deccan volcanism on planktic foraminiferal assemblages during the Maastrichtian and Danian was limited.

This study focus on the catchment of Ambouli wadi which is one of the country’s largest watersheds covering 794 km² (3.5 % of the total area of the Republic of Djibouti). Because of its groundwater resources, this exoreic watershed is of major importance. Indeed, the aquifer is the main source of drinking water supply for the city of Djibouti-city. In addition, this wadi is also responsible for floods causing human suffering and severe economic damages. Despite the importance of the catchment for the development of Djibouti-city, Ambouli wadi has been the subject of few scientific studies. This partly explains the scarcity of rainfall stations and therefore data in this area. Analysis of the spatio-temporal variability of rainfall is required to assess the risk of flooding. In an arid country like the Republic of Djibouti flash floods are an important concern for the management of water resources systems and risk prevention and protection. The desertic climate of the country is characterized by high levels of temperature and evaporation, and also by very weak and irregular annual rainfall, distributed in two major seasons : a cooler season (from October to March) with high relative humidity and low temperatures comprised between 22°C and 30°C, and a hot and dry season (from June to September). Rain data were collected from a network of 9 raingauge stations at different time scales, from monthly to hourly. These data are provided by the national meteorological agency (4 stations) and the early warning system of CERD National Research Center (5 stations). The spatio-temporal variability of rainfall, is characterized using the Standardized Precipitation Index (SPI) and the analysis of rainfall normals over 30 years (1951-1980 and 1961-1990). Long time series data were available from 4 of the 9 stations: (Djibouti-serpent, Djibouti-aeorodrome, Oueah and Arta). At annual scale, the variability is clearly described by a succession of dry and humid years. Also, the monthly rainfall clearly demonstrates the well-known bimodal precipitation regime of east Africa. It shows, two peaks corresponding to the « long rain » and the « short rain » rainy seasons, which correspond to the period of March-April-May and of October-November-December, respectively. On the other hand, we also observe a dry period which is characterized by a rainfall deficit (negative rainfall index for almost all the stations) corresponding to the boreal summer (June to September). Daily data is currently collecting from the Djibouti-aerodrome station (1981-2017) for a better understanding of the precipitation regime. Rainy days are computed from daily data (rainfall > 1 mm) and we find an annual average of 11 wet days with a minimum in 1988 (1 rainy day) and a maximum in 1993 (23 rainy days).

International audience; EGU21-10962https://doi.org/10.5194/egusphere-egu21-10962EGU General Assembly 2021© Author(s) 2021. This work is distributed underthe Creative Commons Attribution 4.0 License.Using hillslope-scale groundwater model to bridge the gap betweenbasin inputs and river concentrations. The case of nitrates inBrittany (France).Luca Guillaumot1, Luc Aquilina2, Jean-Raynald de Dreuzy3, Jean Marçais, and Patrick Durand1International Institute for Applied System Analysis (IIASA), Laxenburg, Austria (luca.guillaumot@live.fr)2Université de Rennes 1, CNRS - Géosciences Rennes, Rennes, France (luc.aquilina@univ-rennes1.fr)3Université de Rennes 1, CNRS - Géosciences Rennes, Rennes, France (jean-raynald.de-dreuzy@univ-rennes1.fr)Over the past decades, intensive agriculture has altered surface water and groundwater resourcesquality. Nutrient surplus increased nitrate concentrations in groundwater and rivers resulting ineutrophication or drinking water risk having ecosystem, sanitary and economic repercussions.Legislations led to a reduction of agricultural inputs of nitrogen since 1990’s followed by adecrease of nitrate concentrations in rivers, but still difficult to predict and evaluate. Indeed, theincomplete knowledge of the spatial variability of climate and nitrogen inputs, cumulated to theunknown groundwater heterogeneity, leads to hydrological and biogeochemical processesdifficult to model. This study deals with the long-term variations (~decades) of nitrateconcentrations in three rivers (~30 km² catchment) located in Brittany. Thus, we focus ongroundwater modelling because they constitute the bigger hydrological reservoir. We developed aparsimonious equivalent hillslope-scale groundwater model. The model parameterization, whichcontrols hydrological functioning such as mean groundwater residence times, young watercontribution to the river or denitrification, relies on long-term monitored streamflow and nitrateriver concentrations. In addition, dissolved CFC were sampled in the catchments. Finally, we foundthat uncertainty on simulated nitrate river concentrations is low. The physically-based model alsobrings information on temporal and spatial variability of groundwater residence times highlightingthe relative importance of young (1-5 yr) and old waters (~decades) for nitrate riverconcentrations. Moreover, calibrated models show similar trends looking at two fictive inputscenarios from 2015 to 2050.

Recent works have shown that laminar flows through porous media generate Lagrangian chaos at pore scale, with strong implications for a range of transport, reactive, and biological processes in the subsurface. The characterization and understanding of mixing dynamics in these opaque environments remains an outstanding challenge. We present a novel experimental technique based upon high-resolution imaging of the scalar signature produced by push-pull flows through various porous materials (beads, gravels, sandstones) at high Péclet number. We show that this method provides a direct image (see below) of the invariant unstable manifold of the chaotic flow, while allowing a precise quantification of the incompleteness of mixing at pore scale. In the limit of large Péclet numbers, we demonstrate that the decay rate of the scalar variance is directly related to the Lyapunov exponent of the chaotic flow. Thus, this new push-pull method has the potential to provide a complete characterization of chaotic mixing dynamics in a large class of opaque porous materials.

The spectral analysis of a planetary surface is fundamental for a deeper understanding of the mineralogy and composition. In particular, the determination of spectral units is a reliable method to infer the physical and compositional properties of a surface by processing several spectral parameters simultaneously, instead of the more traditional approach of interpreting each single parameter separately. To define the spectal units, we first compute the most relevant spectral parameters, based on a preliminary detailed analysis of the spectral properties of a surface. This method could be used for different bodies and is described in [1].For this work, we selected the Apollo Basin area within South Polar Aitken [2,3], the largest and deepest impact basin on the Moon. We analyzed the M3/Chandrayaan-1 data [4] after performing the most up-to-date calibration, thermal removal and photometric correction [5,6]. Lunar spectra are characterized by two strong pyroxenes absorption bands at 1 and 2 µm. In this regard, we decided to define the Apollo Basin spectral units by using the two pyroxenes band depths, the reflectance at 540 nm (standard visible wavelength), and the spectral slope of the 1 µm (see [7]). In Apollo Basin, we found 12 different spectral units. Among these units, the most peculiar is the one linked to the basaltic smooth plains within the floor of the crater. This unit is characterized by low reflectance, deep band depths and a strongly positive spectral slopes (more red surfaces). Subsequently, an analysis of absorption band center at 1 and 2 µm and a comparison with RELAB synthetic pyroxenes [8] revealed a composition compatible with material dominated by strong pyroxene absorptions, e.g. clinopiroxenes, such as pigeonite or augite, with Low Ca and Mg, and relatively high Fe (Fs: 34-75; En: 6-23; Wo: 10-27). The rest of the units show a similar mineralogy to the orthopyroxenes, with intermediate amount of Fe and Mg.This work allows for a detailed understanding of the mineralogy of Apollo Basin, but also lays the groundwork to search for a link between spectral, and morpho-stratigraphic units [9] to reach out highly informative geological maps of the Moon. This innovative approach is one of the main goals of the H2020 no. 776276-PLANMAP project [10].Acknowledgments: This work is funded by the European Union’s Horizon 2020 research grant agreement No 776276- PLANMAP.References: [1] Zambon et al., 2020 LPSC. [2] Ohtake, M. et al., 2014, GRL. [3] Moriarty, D.P. et al., 2018, JGR. [4] Pieters et al., 2009, Current Science. [5] PLANMAP D4.3- Spectral Indices and RGB maps. [6] Besse, S. et al., 2012, Icarus. [7] PLANMAP D4.3- Spectral Indices and RGB maps. [8] http://planetary.brown.edu/relabdocs/synth_pyx/pyroxenes.html. [9] Ivanov, M.A., 2018, JGR. [10] https://www.planmap.eu/.

The spatial and temporal variability of extreme wave climate in the North Atlantic Ocean and the Mediterranean Sea is assessed using a 31-year wave model hindcast. Seasonality accounts for 50% of the extreme wave height variability in the North Atlantic Ocean and up to 70% in some areas of the Mediterranean Sea. Once seasonality is filtered out, the North Atlantic Oscillation and the Scandinavian index are the dominant large-scale atmospheric patterns that control the interannual variability of extreme waves during winters in the North Atlantic Ocean; to a lesser extent, the East Atlantic Oscillation also modulates extreme waves in the central part of the basin. In the Mediterranean Sea, the dominant modes are the East Atlantic and East Atlantic-Western Russia modes, which act strongly during their negative phases. A new methodology for analyzing the atmospheric signature associated with extreme waves is proposed. The method obtains the composites of significant wave height (SWH), mean sea level pressure (MSLP), and 10m height wind velocity (U 10) using the instant when specific climatic indices have a stronger correlation with extreme waves., This research has been supported by the Ministerio de Ciencia e Innovación (grant nos. FPI2016, CTM2015-66225-C2-2-P, RTI2018-095441-B-C21, and PRX18/00218) and the European Geosciences Union (EGU OSPP 2019 grant).

International audience; Examples of fossil and present-day passive margins resulting from mantle exhumation at the ocean–continent transition appear to have developed under conditions of high mantle heat flow. The pattern of geothermal gradients along these hyperextended margins at the time of rifting is of interest for exploration of geothermal and petroleum resources, but is difficult to access. The fossil rift in the North Pyrenean Zone, which underwent high temperature–low pressure metamorphism and alkaline magmatism during Early Cretaceous hyperextension, was studied to explore the geothermal regime at the time of rifting. Data from a set of 155 samples from densely spaced outcrops and boreholes, analyzed using Raman spectroscopy of carbonaceous material, shed light on the distribution of geothermal gradients across the inverted hyperextended Mauléon rift basin during Albian and Cenomanian time, its period of active extension. The estimated paleogeothermal gradient is strongly related to the structural position along the Albian-Cenomanian rift, increasing along a proximal-distal margin transect from ~34°C/km in the European proximal margin to ~37–47°C/km in the two necking zones and 57–60°C/km in the hyperextended domain. This pattern of the paleogeothermal gradient induced a complex competition between brittle and ductile deformation during crustal extension. A numerical modeling approach reproducing the thermal evolution of the North Pyrenees since 120 Ma suggests that mantle heat flow values may have peaked up to 100 mW.m-2 during the rifting event. We demonstrate that the style of reactivation during subsequent convergence influences the thermal structure of the inverted rift system.

International audience; Trading of photovoltaic (PV) energy generation involves several decision making processes at different times with different objectives. For example, a PV power plant coupled with a Battery Energy Storage System (BESS) has to provide bids in the day-ahead electricity market, but can also provide ancillary services. On the delivery day, it can also participate in intra-day trading sessions, and must decide which quantity to charge or discharge from the BESS in real-time. These successive decision-making processes all require forecasts of the energy production level for different forecast horizons. Besides, such decisions are generally not taken for a single plant at a single location but for a collection of several geographically distributed plants.However, the models and the inputs used for the different forecast horizons are often different. In situ measurements are more accurate for very-short term forecasts (real-time to one hour ahead forecasts), satellite data is used for short-term forecasts (up to 6 hours ahead), and Numerical Weather Predictions (NWP) are used for long-term forecasts (day-ahead and longer). Models also vary, with auto-regressive approaches being commonly used for very-short term forecasts, while longer forecast horizons use a wide range of machine learning models. PV producers have thus to develop and maintain numerous forecasting models for the different decision-making processes they are involved in, usually fitted for each power plant. This increases further the complexity of the decision-making processes.In this work we propose a forecasting model that can use all the inputs mentioned before, and weights them according to the forecasting horizon. It can thus operate from very short-term to day-ahead forecast horizons with state-of-the-art performance. It can also directly provide probabilistic forecasts for an aggregation of power plants, thus allowing having a single forecasting model for managing a virtual power plant. The model follows the lazy learning paradigm, where generalization from the training set is only computed when a forecast is requested. Thus, the model is resilient to changes in the neighborhood of the plant (surrounding environment, partial outage, soiling, etc.). The model is based on the Analog Ensemble (AnEn) method. However it is structurally expanded to allow the method to use an arbitrary large number of inputs. Each input is then weighted depending on the forecast horizon, which allows dynamically selecting the most relevant inputs depending on the horizon.The model is evaluated for short-term and day-ahead forecasts, and compared with a Quantile Regression Forest (QRF) and Bayesian Automatic Relevance Determination (ARD) for day-ahead forecasts, and a linear Auto-Regressive Integrated Moving Average (ARIMA) model for short term forecasts. Results show that the AnEn model is competitive with the QRF and ARD models in day-ahead forecasting, while requiring less computational resources and without a need for regular retraining. It is also better than the ARIMA model for short-term forecasting. An evaluation conditional to the the weather variability allow to assess the model performance in the best and worst condition.

International audience; Supergene copper mineralization (SCM) are nowadays the economic viability of many porphyry copper deposits worldwide. These mineralization are derived from supergene processes, defined by Ransome (1912) as sulfide oxidation and leaching of ore deposits in the weathering environment, and any attendant secondary sulfide enrichment. For supergene copper mineralization to form, favorable tectonics, climate and geomorphologic conditions are required. Tectonics control the uplift needed to induce groundwater lowering and leaching of sulphides from a porphyry copper deposit. Climate controls copper leaching in the supergene environment and groundwater circulation towards the locus where supergene copper-bearing minerals precipitate. Two types of SCM have been recognized: 1) in-situ SCM, which are products of descending aqueous solutions and 2) exotic SCM, which are the products of lateral migration of supergene copper solutions from a parental porphyry copper deposit (Sillitoe, 2005).In the Atacama Desert, such deposits seem to take place during specific Tertiary climatic periods and relief formation. But many uncertainties remain regarding the genesis and the exact timing for their formation. In this study, a coupled approach combining a petro-geochemical study and LA-ICP-MS U-Pb dating were applied to four mining copper deposits (e.g. Mina Sur, Damiana, El Cobre, Zaldivar) from hyperarid Atacama Desert of Northern Chile. Textural features are the same in all the deposits with chrysocolla as the abundant mineral, followed by black chrysocolla, pseudomalachite and minor atacamite and copper wad. Their geochemical compositions (i.e. major, traces and rare Earth elements) also show homogeneous results suggesting similar process in their genesis. U-Pb dating were performed on black chrysocolla, chrysocolla and pseudomalachite from all the deposits. Apart from Mina Sur deposit, all the mines mentioned above showed high common lead content. To try to extract in these deposit an U-Pb age, complementary analyses to quantify accurately common lead concentration are ongoing, using MC-ICPMS. At Mina Sur, U-Pb dating performed on pseudomalachite bands yields a crystallisation age of 18.4 ± 1.0 Ma. For the black chrysocolla clasts, the 206Pb/238U apparent ages are ranging from 19.7 ± 5.0 Ma down to 6.1 ± 0.3 Ma, a spreading that we interpret as the result of uranium and lead mobility linked to fluid circulation following crystallization. Isotopic analyses, i.e. Cu and O isotopes, are in progress to better constrain the source and nature of these fluids. This study demonstrates, for the first time, that supergene copper mineralization presents a chronological potential and can be dated, at least in some case, by the U-Th-Pb method. Furthermore, the age obtained on pseudomalachite indicates that Mina Sur deposition took place as early as 19 Ma, a result that is in agreement with geological constraints in the mining district and the supergene ages already known in the Atacama Desert. These promising results represent a new tool to understand the physico-chemical, climatic and geological conditions that prevailed during the formation of supergene copper deposits and a proxy for their prospection around the world and maybe date climatic variation.

Antimony (Sb) is a critical metal for Europe. Indeed, Sb is widely used in a variety of industrial operations, especially in the European aircraft industry, such as production of flame retardants, plastics, paint pigments, glassware and ceramics, alloys in ammunition and battery manufacturing plants.Despite its strategic importance, the knowledge on Sb and its ore deposits remains poorly constrained. Moreover, Europe remains under the threat of an essentially Chinese supply despite a proven potential for European deposits that contain also strategic and precious co-products (W, Au). In parallel, Sb and associated metalloids (As, Hg, etc) are more and more recognised as a global threat for human health and it has been demonstrated that most of elevated concentrations of Sb on earth surface originate from natural, geogenic sources. Then, a first large-scale identification of these areas where primaries resources occur and metalloids can contaminate humans should be a priority.To achieve its objectives, the overall approach of the ERA-MIN2 AUREOLE project (2019-2022 - https://aureole.brgm.fr) is based on disruptive concepts: i) development of a 3D large-scale metallogenic model integrating deep-seated processes to determine the spatial distribution of ore deposits; ii) the use of mineral prospectivity data weighted by surface data to determine the probability of environmental risk over large areas.The work package (WP) 1 is dedicated to produce the new 3D deep-seated metallogenic model for antimony mineralisations and contribute to the global 3D understanding of the Sb mineralising processes. The WP2 is designed to the understanding of processes - such as geomorphology, weathering, climate - that control the mobilisation and transport of metalloids at the earth surface. The WP3 will use results from WPs 1 & 2 to produce large-scale mineral prospectivity and a large-scale environmental risk assessment by weighting mineral prospectivity with earth surface properties, such as DTM, rainfall, weathering cartographic maps, etc.The AUREOLE project will bring new scientific knowledge on Sb and Sb deposits, for a better mineral exploration targeting.The expected outcomes will be several high-impact deliverables devoted to the targeting of new Sb deposits and a new large-scale environmental assessment maps for decision-making dealing with humans health. Long term expected impacts would be an increase of EU Sb resources and EU Sb sustainable supply. Because of its implications for European critical metals, the AUREOLE project will provide new findings and results to the SCRREEN project (Solutions for Critical Raw Materials – a European Expert Network) and to the IMP@CT project (Integrated Mobile Modularised Plant and Containerised Tools for sustainable, selective, low-impact mining of small, high-grade or complex deposits). It will also interact with the Geo-ERA FRAME project (Forecasting and assessing Europe’s strategic raw materials needs).

Understanding the source-to-sink system in sedimentary basins supposes the characterization of two key parameters: the source and the mode of sediment production (physical vs. chemical erosion), as well as the distance of the transfer zone. The shape of the quartz grains may record (1) the chemical vs. physical production of the grain, (2) the processes (eolian vs. fluvial) of sediment transfers, and (3) possible post-deposition emersion and weathering.The criteria to distinguish chemical erosion are microstructures linked to dissolution (oriented etch pits, solution pits, solution crevasses and scaling) or precipitation (crystalline overgrowths and silica globules, flowers and pellicle). The difference between eolian and fluvial processes is mainly based on the roundness and the type of impact (conchoidal breakage, percussion marks and grooves).This approach was successfully applied to the Cenozoic of the Paris Basin, a low accommodation sedimentary system (maximum 200 m in 35 Ma) encompassing numerous hiatuses. The source was mainly subjected to chemical erosion, since etching microstructures are often observed overcut by eolian or fluvial transport criteria. This chemical weathering is thought to has been particularly pronounced during Paleocene and Early Eocene times. Eolian transport occurred preferentially during Danian, Lutetian and Bartonian times whereas fluvial transport appears dominant in Danian, Thanetian and Ypresian times. Major emersion marked by in situ laterites growing occurred during Late Paleogene times, Ypresian and Bartonian, with minor ones during Thanetian. This is testified by the superimposition of chemical weathering features on grains smoothed by fluvial and/or eolian transport.

Recent and dramatic events occurred on the Italian transport networks have pointed out the urgent need for assessing the actual state of health along the national transport assets. Analogous considerations can be addressed towards the high exposition and vulnerability of the transport system to major natural events, such as floods or earthquake.Recently, the administrations and managing companies have increasingly made use of non-destructive techniques for achieving a denser knowledge about the health of the asset.However, one of the major limitations concerning these methods is that each technology, according to its specific features, is usually suitable for a single specific application and has very limited effectiveness for other tasks. Accordingly, the integration of datasets collected with different NDTs stands as a viable approach to fill technology-specific gaps, thereby ensuring a more comprehensive assessment of the infrastructure [1-3]. Data fusion logic can also potentially allow for further data interpretation from merging different information [4].The EXTRATN project aims at overcoming the state-of-the-art research in the field of non-destructive monitoring of linear infrastructures and, through a “data fusion” logic, at achieving a comprehensive rate of knowledge about the actual condition of the asset. The addressed concept is a “fully sensed infrastructure”, being sensed by different technologies and with different scopes. Specifically, interferometric synthetic aperture radar (DInSAR), Laser Imaging Detection and Ranging (LiDAR), Ground-penetrating Radar (GPR) and Falling Weight Deflectometer (FWD) are considered to the purpose.A system of transport infrastructure being located in the Province of Salerno (IT), within an area subjected to hydrogeological risk, has been selected as a study case for the integrated approach. This system includes a motorway, a rural highway and a railway.As a major advantage with respect to the state-of-the-art, such a methodology allows for analysing the evolution trend of the on-going distresses, meaning a significant upgrade of the monitoring activities that may provide valuable information for a priority-based scheduling of the maintenance.Moreover, such an approach enables to simultaneously monitor exogenous and endogenous events that may lead to a decrease of the safety, functionality or strength conditions.The research is supported by the Italian Ministry of Education, University and Research under the National Project “Extended resilience analysis of transport networks (EXTRA TN): Towards a simultaneously space, aerial and ground sensed infrastructure for risks prevention”, PRIN 2017, Prot. 20179BP4SM. Liu W, Chen S, Hauser E (2011) LiDAR-based bridge structure defect detection. Exp Tech 35(6):27–34. Grasmueck M, Viggiano DA (2007) Integration of ground-penetrating radar and laser position sensors for real-time 3-D data fusion. IEEE Trans Geosci Remote Sens 45(1):130–137. Solla M et al (2011) Non-destructive methodologies in the assessment of the masonry arch bridge of Traba, Spain. Eng Fail Anal 18(3):828–835 Luo RC, Yih C-C, Su KL (2002) Multisensor fusion and integration: approaches, applications, and future research directions. IEEE Sens J 2(2):107–119.

International audience; Nanofluids are recent nanomaterials with improved thermophysical properties that could enhance the efficiency and reliability of heat transfer systems. Relevant properties for heat transfer calculation, thin film flows, droplet impingements or microfluidic are surface tension and wettability. However, to date, the understanding of those properties in nanofluids field is at the beginning compared to transport properties. At this stage, this review focus on the effect of nanoparticles and base fluid nature, temperature, use of surfactant, nanoparticle concentration, size and shape as well on the surface tension and wettability of nanofluids. After the presentation of heat transfer processes involving the influence of surface tension and wettability, this paper is organized according to the nature of the nanoparticles dealing with oxide, carbon-based and metallic nanofluids as well as unusual or less considered nature of nanoparticles. The factors affecting the surface tension of nanofluids are relatively well identified, but concentration and surfactant effects present some inconsistent outcomes. In any case, the dispersion of nanoparticles have an effect on the surface tension of base fluid significantly lower than that on transport properties. Based on results available in the literature and existing empirical correlations, a comprehensive assessment, challenges and future works are suggested. © 2018 Elsevier Ltd

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International audience; Some organic pollutants found in soils, like the herbicide 2,4-D, are very mobile and can easily infiltrate, reach the underground water and spread more broadly in the environment. The degradation of these pollutants during their lixiviation through soil is a critical point to understand. This degradation starts with the encounter between the pollutant and the degrading agent, that are mainly bacterial endoenzymes in the case of 2,4-D. Encounter, and thus spatial distributions of bacteria and pollutants, appear to be particularly relevant in soils, where these distributions can be highly heterogeneous and sparse. This leads us to wonder how the macroscopic spatiotemporal distributions of bacteria and their substrate impact their encounter and thus pollutant degradation. It is often assumed that the dispersion of bacteria and their substrate in soil eventually promotes their encounter. But the validation and the fine understanding of this assumption, especially of how this encounter is shaped by the interaction between transport processes and bacterial metabolism, is still unclear. We use this assumption as our working hypothesis. We develop several reactive transport models at mm-to-cm scale (Babey et al., 2017), in a considered homogeneous medium, aimed at investigating the impacts of initial localizations (mainly co-localization) and concentrations of 2,4-D and its bacterial degraders on 2,4-D biodegradation, under several transport processes (diffusion and advection) and biochemical processes (sorption and microbial metabolism). These models are built and calibrated on cm-scale experiments performed on the degradation of 2,4-D spots in natural repacked soil cores without dispersion of bacteria (Pinheiro et al., 2015), and compared to homologous experiment with dispersion of bacteria (Pinheiro et al., 2018). Contrary to our hypothesis, we show through modeling that dispersion of bacteria and substrate decreases their encounter in many cases. This is caused by the immediate, continuous, and strongly adverse effect of substrate dilution. We show that dispersion promotes encounter in some very specific cases, when an inversion of substrate gradient occurs, that is when the effect of dilution is at least counterbalanced by a decrease of spatial competition of bacteria for substrate. Whether bacteria dispersion promotes or not encounter strongly depends on the interplay between transport processes and metabolism. We also show that the positive effect of dispersion on encounter is theoretically limited, and that in some experiments it is not high enough to explain the observed increase of pollutant biodegradation caused by bacteria dispersion. This points out that dispersion can act also through processes other than encounter between bacteria and their substrate. One of these processes could be spatial inhibition between bacteria. References Babey T, Vieublé-Gonod L, Rapaport A, Pinheiro M, Garnier P, de Dreuzy J-R. Spatiotemporal simulations of 2,4-D pesticide degradation by microorganisms in 3D soil-core experiments. Ecol Model. 2017 Jan;344:48–61. Pinheiro M, Garnier P, Beguet J, Martin Laurent F, Vieublé Gonod L. The millimetre-scale distribution of 2,4-D and its degraders drives the fate of 2,4-D at the soil core scale. Soil Biol Biochem. 2015 Sep;88:90–100

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