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International audience; Detrital zircon grains from Cambrian–Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Anti-Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63–0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian–Tonian shift (ca. 1.25–0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central-Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions.

International audience; Bilebullephlebia legendrei n. gen., n. sp. is described, illustrated, and placed into the small epiproctophoran family Burmaphlebiidae. This family was previously known from the mid-Cretaceous Kachin amber by two monotypic genera, but the new fossil shows that its diversity is underestimated. At least one additional genus with an enigmatic wing venation remains to be described from the same deposit. Nothing is known about the genitalia configuration of the Burmaphlebiidae but new fossils are expected to clarify the position of the family which is currently only discussed in light of wing venation characters.

The transition from a greenhouse to an icehouse world at the Eocene-Oligocene Transition (EOT) coincided with a large decrease of pollen from the steppe-adapted genus Nitraria. This genus, now common along the Mediterranean coast, Asia and Australia, has a proposed coastal origin and a geographically widespread fossil record. Here we investigated the evolution, taxonomic diversity and morphological disparity of Nitraria throughout the Cenozoic by integrating extant taxa and fossil palynological morphotypes into a unified phylogenetic framework based on both DNA sequences and pollen morphological data. We present the oldest fossil pollen grain of Nitraria, at least 53 Myr old. This fossil was found in Central Asian deposits, providing new evidence for its origin in this area. We found that the EOT is an evolutionary bottleneck for Nitraria, coinciding with retreat of the proto-Paratethys Sea, a major global cooling event and a turnover in Central Asian steppe vegetation. We infer the crown age of modern Nitraria spp. to be significantly younger (Miocene) than previously estimated (Palaeocene). The diversity trajectory of Nitraria inferred from extant-only taxa differs markedly from one that also considers extinct taxa. Our study demonstrates it is therefore critical to apply an integrative approach to fully understand the plant evolutionary history of Nitrariaceae.

International audience; The structural organization of heterogeneous and multiphase natural aggregates depends on the biophysicochemical conditions prevailing in the environment, with major ions playing a crucial role. In this study, the impact of aluminum (Al) on iron-organic matter (Fe-OM) aggregates was investigated since Al can interact with OM and can be incorporated in Fe-oxyhydroxides or adsorbed on their surface. Mimetic environmental Fe-OM-Al aggregates were synthesized at various [Fe] and [Al] with a constant [OM]. At low [Al+Fe], Fe-OM-Al aggregates exhibit a colloidal behavior. Within the aggregates, Fe is present as Fe(III)-oligomers and ferrihydrite-like nanoparticles whereas Al forms monomers, oligomers and small polymers, all bound to OM. The Al and Fe phases interacted with each other. At high [Fe+Al], the Fe(III)-oligomers and Al monomers/oligomers polymerized which increases the size and quantity of the ferrihydrite-like nanoparticles and Al polymers and then branched out the OM, resulting in a large settling network. The effect of Al on the Fe-OM aggregates structure could also have an impact on the fate of pollutants. The occurrence of Al amorphous hydroxides and the increase in ferrihydrite-like nanoparticles lead to a higher availability of surface reactive sites and subsequently to an increase in the sorption capacity of the Fe-OM aggregates for pollutants that exhibit a greater affinity for minerals than for organics.

International audience; Plastic has been largely detected in estuarine environments and represents major concern towards aquatic living organisms. The present study evaluates the impact of microplastics (MPs) and nanoplastics (NPs) under realistic exposure conditions. Scrobicularia plana individuals were exposed to low concentrations (0.008, 10, and 100 µg L−1) of environmental MPs and NPs as well as to standard PS NPs, as a comparison condition. The aim of this study was to understand the ecotoxicological effects of environmental plastic particles on S. plana gills and digestive glands but also to compare the effects of plastic polymers size in order to highlight if the size could induce different toxicity profiles within this model organism, at different levels of biological organization. Results showed a differential induction of detoxification enzymes (CAT, GST), immunity (AcP), DNA damage processes as well as a differential effect on behavior and condition index of animals depending upon the type of plastic, the size, the concentration tested, and the type of organ. This study underlines the necessity of testing (i) plastics collected from the environment as compared to standard ones and (ii) the effect of size using plastics coming from the same batch of macrosized plastics. This study concludes on the future need directions that plastic-based studies must take in order to be able to generate a large quantity of relevant data that could be used for future regulatory needs on the use of plastic.

International audience; The objective of the paper is to better understand and quantify the flow structure in fractured rocks from flow logs, and to propose relevant indicators for validating, calibrating or even rejecting hydrogeological models. We first studied what the inflow distribution tells us about the permeability structure from a series of analyses: distribution of transmissivities as a function of depth, proportion of flowing sections as a function of section scale, and scaling of the arithmetically-averaged and geometrically-averaged permeability. We then define three indicators that describe few fundamental characteristics of the flow/permeability, whatever the scale: a percolation scale , the way permeability increases with scale above , and the variability of permeability. A 4th indicator on the representative elemental volume could in principle be defined but the data show that this volume/scale is beyond the 300 m investigated. We tested a series of numerical models built in three steps: the geo-DFN based on the observed fracture network, the open-DFN which is the part of the geo-DFN where fractures are open, and a transmissivity model applying on each fracture of the open-DFN (Discrete Fracture Network). The analysis of the models showed that the percolation scale is controlled by the open-DFN structure and that the percolation scale can be predicted from a scale analysis of the percolation parameter (basically, the third moment of the fracture size distribution that provides a measure of the network connectivity). The way permeability increases with scale above the percolation threshold is controlled by the transmissivity model and in particular by the dependence of the fracture transmissivity on either the orientation of the fractures via a stress-controlled transmissivity or their size or both. The comparison with data on the first two indicators shows that a model that matches the characteristics of the geo-DFN with an open fraction of 15% as measured adequately fits the data provided that the large fractures remain open and that the fracture transmissivity model is well selected. Most of the other models show unacceptable differences with data but other models or model combinations has still to be explored before rejecting them. The third indicator on model variability is still problematic since the natural data show a higher variability than the models but the open fraction is also much more variable in the data than in the models.

Acoustic pulses transmitted across air bubbles in water are usually analyzed in the ν frequency domain to determine attenuation and phase velocity for comparison with effective models. In the present work, acoustic experiments performed beyond the bubble resonance frequency highlight an attenuation approximated to a(ν/ν0)^(-y) with y>0 and ν0 the wavelet source peak frequency, a significant shape variability of the waveform with the propagation distance x

Hearth-pits are some of the most common archaeological features documented in open-air Mesolithic sites, especially in coversand areas of NW Europe. However, very few geoarchaeological studies have addressed their formation, function and relationship with occupation surfaces. This work introduces new interdisciplinary investigations on the sediments of the Mesolithic open-air site of El Arenal de la Virgen (SE Iberia). A selection of five hearth-pits from two different occupation phases (Phase 1: 9.3–9.1 cal ka BP and Phase 2: 8.6–8.3 cal ka BP) has been analysed using stratigraphy, texture, soil chemistry, micromorphology, petrography and OSL and TL analyses. Combustion traits of the carbonate rock assemblages preserved in the sediments of the hearth-pits have also been investigated and compared to reference and experimental data from local geogenic materials. Our results allowed us to discuss the anthropogenic origin and taphonomy of the hearth-pits studied and approach their function. The structures from Phase 1 are interpreted as a possible oven and a dumping feature linked to single/occasional use events. In contrast, for hearth-pits from Phase 2, we propose they were related to combustion and dwelling areas subject to recurrent occupation episodes and disturbance. Finally, our sedimentary and soil data revealed existing favourable paleoenvironmental conditions during the Mesolithic occupation of the site characterized by increased moisture, temperature and vegetation cover, in contrast to the Pleistocene and Middle Holocene periods pre- and post-dating the human settlement. This work highlights the potential of integrating geoarchaeological and contextual evidence to clarify the factors involved in the formation of hearth-pits and infer intra-site occupation patterns. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. AP-D is currently the holder of a Maria Zambrano fellowship at the University of the Basque Country (UPV/EHU) funded by the Ministry of Universities (Government of Spain) and the European Union-Next GenerationEU-. JRR is currently supported by a Margarita Salas fellowship funded by the European Union-Next Generation EU, the Spanish Ministry of Universities and the University of Alicante. The present study is part of the PALEODEM project, funded by the European Research Council (ERC-CoG-2015 granted to JF-LdP) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 683018)".

International audience; 12 The Early Cretaceous topographic evolution of Transbaikalia was largely governed by the 13 tectonic evolution of the Mongol-Okhotsk orogenic belt. The collapse of the Mongol-Okhotsk 14 orogen triggered the formation of metamorphic core complexes and associated extensional basins, 15 widespread throughout Transbaikalia, North Mongolia, and North China. Numerous lithofacies proximal sediment sources. Distal provinces also made a contribution to sedimentation indicating 29 the rise of a positive topography characterizing the exhumation of the metamorphic core 30 complexes. Overlying fine-grained formations indicate a significant smoothing of the topography, 31 suggesting that from middle Aptian, Western Transbaikalia developed in a relatively calm tectonic 32 regime. We also show that the basins of Transbaikalia were formed both in conjunction with the 33 exhumation of metamorphic cores complexes and reactivated structural sutures. Revised data on 34 dinosaur fauna and palynology, together with the dating of host deposits, provide insights on the 35 Early Cretaceous paleoenvironmental evolution.

Jurassic carbonate strata in the eastern Paris Basin exhibit several generations of faults, tension gashes and stylolites. Although their relative chronology can sometimes be determined according to cross-cutting relationships, the duration of major deformation phases and their influence on fluid flow and carbonate cementation are still uncertain. This contribution aims to clarify the timing of brittle deformation and associated calcite cementation. Tension gashes filled by calcite in Jurassic carbonates were sampled in outcrops and boreholes and dated through U–Pb geochronology. Almost all the sampled fractures were cemented during the Cenozoic period. Continuous deformation spread from c. 50 to 30 Ma. Tension gashes oriented N10° to N20° dated at 48–43 Ma show the main Pyrenean contractional stage. A second set of calcites were dated at c. 35–33 Ma and document a Late Eocene – Oligocene extension. A transition from the compressional to the extensional regime is expressed by tension gashes dated between 43 and 35 Ma. Finally, tension gashes oriented N150° to N175°, dated between 32 and 18 Ma, may result from the propagation of the horizontal stress generated by the Alpine orogen or by late Pyrenean deformation. Clumped isotope thermometry on five samples revealed both low crystallization temperatures (from 27 to 53 °C) and the meteoric origin of calcite-precipitating fluids. Our research therefore documents a continuous fracturing from Ypresian to Rupelian times, and less expressed brittle deformation during the Miocene period.

International audience; An ammonite biostratigraphy for Oxfordian in the Tlemcenian domain (northwestern Algeria) belonging to the south Tethyan margin is presented. It is based on the study of many sections located near Takhemaret and Frenda cities (Province of Tiaret). From bottom to top, the following biozones and subzones are distinguished: (i) Liosphinctes plicatilis Zone subdivided into the Cardioceras vertebrale (including the Otosphinctes arkelli Horizon) and Dichotomosphinctes antecedens subzone (including the Dichotomosphinctes antecedens Horizon); (ii) Gregoryceras transversarium Zone subdivided into four subzones: Perisphinctes parandieri, Dichotomosphinctes luciaeformis (its presence is doubtful), Larcheria schilli and Dichotomoceras rotoides subzones; (iii) Dichotomoceras bifurcatus Zone subdivided into two subzones: Dichotomoceras stenocycloides Subzone including the Dichotomoceras bifurcatoides Horizon, and the Dichotomoceras grossouvrei Subzone. The obtained results are compared and completed with those of Bou Rheddou and Bechtout (northern Tiaret city). The recorded biozones are very similar to the standard biozonation of the Upper Jurassic recognized throughout the Mediterranean region.

Pools are common features of peatlands and can represent from 5 % to 50 % of the peatland ecosystem's surface area. Pools play an important role in the peatland carbon cycle by releasing carbon dioxide and methane to the atmosphere. However, the origin of this carbon is not well constrained. A hypothesis is that the majority of the carbon emitted from pools predominantly originates from mineralized allochthonous (i.e., plant-derived) dissolved organic matter (DOM) from peat rather than in situ primary production. To test this hypothesis, this study examined the origin, composition, and degradability of DOM in peat porewater and pools of an ombrotrophic boreal peatland in northeastern Quebec (Canada) for 2 years over the growing season. The temporal evolution of dissolved organic carbon (DOC) concentration, the optical properties, molecular composition (THM-GC-MS), stable isotopic signature (δ13C-DOC), and degradability of DOM were determined. This study demonstrates that DOM, in both peat porewater and pools, presents a diverse composition and constitutes highly dynamic components of peatland ecosystems. The molecular and isotopic analyses showed that DOM in pools was derived from plants. However, DOM compositions in the two environments were markedly different. Peat porewater DOM was more aromatic, with a higher molecular weight and DOC : DON (dissolved organic nitrogen) ratio compared to pools. The temporal dynamics of DOC concentration and DOM composition also differed. In peat porewater, the DOC concentration followed a strong seasonal increase, starting from 9 mg L−1 and reaching a plateau above 20 mg L−1 in summer and autumn. This was explained by seasonal peatland vegetation productivity, which is greater than microbial DOM degradation. In pools, DOC concentration also increased but remained 2 times lower than in the peat porewaters at the end of the growing season (∼ 10 mg L−1). Those differences might be explained by a combination of physical, chemical, and biological factors. The limited hydraulic conductivity in deeper peat horizons and associated DOM residence time might have favored both DOM microbial transformation within the peat and the interaction of DOM aromatic compounds with the peat matrix, explaining part of the shift of DOM compositions between peat porewater and pools. This study did not report any photolability of DOM and only limited microbial degradability. Thus, it is likely that the DOM might have been microbially transformed at the interface between peat and pools. The combination of DOM quantitative and qualitative analyses presented in this study demonstrates that most of the carbon present within and released from the pools originates from peat vegetation. These results demonstrate that pools represent a key component of the peatland ecosystem ecological and biogeochemical functioning.

International audience; The foundations of modern quantitative geomorphology have thus been built around this paradigm of steady-state landscapes responding to progressive changes in climatic or tectonic condition. In ice-free landscapes, the evolution of continental landforms over large time scales is generally described by a competition between tectonic uplift and erosion of rivers and hillslopes. The initiation of co-seismic landslides is generally attributed to the passage of seismic waves, and in particular to the peak ground acceleration associated with volume waves. The volume of landslides is then generally obtained using empirical scaling laws with their area. Co-seismic landslides have a geomorphological impact that goes beyond the co-seismic phase. The principle of a landscape at a steady state, with a balance between the rates of erosion and uplift, needs to be reconsidered due to the amplitude and variability of tectonic and geomorphological processes during the seismic cycle

International audience; Reorganization of the Asian climate from one dominated by global planetary wind systems to a regional monsoon climate is closely related to the surface uplift of the Tibetan Plateau (TP). However, evaluating this climatic reorganization is limited by difficulty in constraining the complex, multistaged uplift of the TP and contradictory evidence regarding Asian Monsoon onset. In this Review, we summarize proxy and model evidence for Asian Monsoon initiation at different latitudes to identify the main controls on monsoon evolution. Stratigraphy and palaeoclimate proxy records indicate that the Asian climate was reorganized in a two-stage northward expansion process. At ~41 million years ago (Ma), the monsoon advanced northwards from the tropic to the southern subtropical regions (~26° N, approximately present-day Yunnan), probably driven by central TP uplift, global cooling and rapid regression of the proto-Paratethys Sea. At ~26 Ma, the monsoon expanded northwards into temperate regions (~30–36° N, equivalent to the present-day Asian Monsoon boundary), likely driven by TP growth and global warming. Additional proxy records are needed to fill regional gaps, establishing more solid boundary conditions and improving parameter constraints for climate models.

International audience; A new genus and species of Odonatoptera is described and figured from the Amisan Formation as Koreaphlebia iussradiae gen. et sp. nov. This new genus and species is placed in the Zygophlebiidae and differs from all other zygophlebid, inter alia, owing to the forewing with a distinct bridge IR2-RP2-IR1 perfectly straight, crossvein between MP and Cu+AA below apex of MAb vertical and rather long, base of CuP separating from that of CuA opposite point of junction between MAa and MP, at the crossing point of ‘pillar’ and Cu+AA, and RP3/4 with at most short distal branches covering a small area. This new specimen is the first Zygophlebiidae from the Amisan Formation. The temporal range of the Triadophlebiomorpha is used to discuss the dating of the Amisan Formation.

International audience; Trans-dimensional Markov chain Monte Carlo (MCMC) treats the number of model parameters as an unknown, and provides a natural approach to assess models of variable complexity. We demonstrate the application of these methods to geochronology and thermochronology. The first is mixture modelling, physically a finite dimension problem, which aims to extract the number and characteristics of component age distributions from an overall distribution of radiometric age data. We demonstrate the MCMC method with Gaussian and skew-t component distributions, the latter containing the former as a special case, applied to a suit of U-Pb zircon data from a sediment in northern France. When considering the posterior distributions obtained from the MCMC samplers, the asymmetrical skew distribution models imply fewer components than the symmetrical Gaussian distribution models. We present some heuristic criteria based on different ways to look the results and aid in model choice in the mixture modelling problem. The second application is a thermal history model, physically a continuous time-temperature function but here parametrised in terms of a finite number of time temperature nodes. We consider a suite of synthetic data from a vertical profile to demonstrate the variable resolution in models constrained from single and multiple samples. Provided the implicit assumptions made when grouping multiple samples are valid, the multi-sample approach is preferable as we exploit the variable information on the model (thermal history) contained in different samples.

International audience; Amber and plant remains were discovered in the lower Cenomanian lignitic clay from La Gripperie-Saint-Symphorien (Charente-Maritime, western France). The amber mainly consists of scarce and infracentimetric pieces showing a wide range of sizes and colours. The shape of the amber grains greatly varies, including more or less cylindrical fragments of flows and spherical drops. Plants consist of foliar remains corresponding to isolated pinnae and pinnules of ferns (Matonia sp., Weichselia reticulata (Stokes & Webb, 1824) Fontaine emend. Alvin, 1971), leafy axes of conifers (Geinitzia reichenbachii (Geinitz, 1842) Hollick & Jeffrey, 1909, Pagiophyllum sp.) and leaves of angiosperms (including cf. Eucalyptolaurus depreii Coiffard, B.Gomez, Thiébaut & J.Kvaček and three morphotypes of undeterminable leaves). They are preserved as isolated cuticles, charcoalified compressions without cuticle, and external casts. Angiosperms are clearly the most abundant and diverse remains of the plant assemblage. This latter contrasts with most of Albian-Cenomanian coastal floras from the Aquitaine Basin, which are dominated by gymnosperms characterised by xeromorphic adaptations and tolerating halophytic conditions. Similar to the coeval sites of Puy-Puy (Charente-Maritime) and Jaunay-Clan (Vienne), the plant-rich clay from La Gripperie-Saint-Symphorien was probably deposited in innermost coastal environments heavily influenced by inland/continental freshwater.; De l’ambre et des plantes ont été découverts dans les argiles ligniteuses du Cénomanien inférieur de La Gripperie-Saint-Symphorien (Charente-Maritime, Ouest de la France). L’ambre correspond principalement à de rares pièces infracentimétriques qui montrent une large gamme de tailles et de couleurs. La forme des grains varie beaucoup, incluant des fragments de coulées plus ou moins cylindriques, ainsi que des gouttes sphériques. Les plantes correspondent à des pennes et pinnules isolées de fougères (Matonia sp., Weichselia reticulata (Stokes & Webb, 1824) Fontaine emend. Alvin, 1971), des axes feuillés de conifères (Geinitzia reichenbachii (Geinitz, 1842) Hollick & Jeffrey, 1909, Pagiophyllum sp.), ainsi que des feuilles d’angiospermes (incluant cf. Eucalyptolaurus depreii Coiffard, B.Gomez, Thiébaut & J.Kvaček et trois morphotypes de feuilles indéterminées). Ces restes sont préservés sous forme de cuticules isolées, compressions charbonneuses sans cuticule et moulages externes. Les angiospermes constituent les restes les plus abondants et les plus diversifiés de l’assemblage paléobotanique. Ceci contraste avec la plupart des flores littorales de l’Albien-Cénomanien du Bassin Aquitain, dominées par des gymnospermes montrant des adaptations xéromorphiques ainsi qu’une tolérance aux conditions halophytiques. Similairement aux sites contemporains de Puy-Puy (Charente-Maritime) et Jaunay-Clan (Vienne), les argiles à plantes de La Gripperie-Saint-Symphorien ont probablement été déposées dans des environnements côtiers plutôt internes et fortement influencés par de l’eau douce.

The amber fossil record is distributed worldwide but mainly supported by Northern Hemisphere deposits.The Southern Hemisphere amber fossil record is relatively scarce, due to difficulties of access andprospection. The African continent recently revealed two new amber outcrops. Previously, fossiliferous andnon fossiliferous copals were known from Africa, as well as older fossilised resins lacking fossil inclusions1.The Cretaceous resin from Congo, and the Cenozoic resin from Ethiopia, are the first African ambers knownto display arthropod and botanical inclusions.When first mentioned in 20102, the Ethiopian amber was suggested Cretaceous. This dating was rapidlyquestioned by the modern lineage taxa, described from the fossilized resin3,4. Those rather display a Cenozoicassemblage. Palynological data and field observations corroborate this revision and further indicate aMiocene age of the amber. The resin originates from an angiosperm, probably Hymenaea (Fabaceae), assuggested by its chemical signal, and the associated botanical inclusions. Cryptogam and arthropod inclusions(mainly Hymenoptera and Diptera) already display a large diversity of modern taxa. All together, fossilisedspecimens illustrate a subtropical, hot and humid, swamp forest ecosystem. Similarities with the botanicaland entomofaunal composition of the contemporaneous Dominican and Mexican ambers, suggest anaffinities between African and American Miocene ecosystems.References1. Bouju V., Perrichot P. 2020: BSGF Earth Sci. Bull., 191 (17); doi:10.1051/bsgf/20200182. Schmidt A.R. et al. 2010: Proc. Natl Acad. Sci. U.S.A., 107 (16), 7329 7334; doi:10.1073/pnas.10009481073. Coty D. et al. 2016: Ann. Soc. entomol. Fr., 52 (3), 161 166; doi:10.1080/00379271.2016.12304774. Perrichot V. et al. 2016: The age and paleobiota of Ethiopian amber revisited, in 5th InternationalPaleontological Congress.

Here we report on Neanderthal engravings on a cave wall at La Roche-Cotard (LRC) in central France, made more than 57±3 thousand years ago. Following human occupation, the cave was completely sealed by cold-period sediments, which prevented access until its discovery in the 19 th century and first excavation in the early 20 th century. The timing of the closure of the cave is based on 50 optically stimulated luminescence ages derived from sediment collected inside and from around the cave. The anthropogenic origin of the spatially-structured, non-figurative marks found within the cave is confirmed using taphonomic, traceological and experimental evidence. Cave closure occurred significantly before the regional arrival of H . sapiens , and all artefacts from within the cave are typical Mousterian lithics; in Western Europe these are uniquely attributed to H . neanderthalensis . We conclude that the LRC engravings are unambiguous examples of Neanderthal abstract design.

International audience; 'BayLum' is an R-package that facilitates the application of Bayesian models to the field of OSL dating. Here we present two recent feature updates to 'BayLum', significantly reducing computation time and improving general use. The first feature allows users to parallelize the computations involved in the MCMC sampling of values, while the second introduces the ability to extend a 'BayLum' model, which has run to completion without converging. All updates are automatically available with 'BayLum' v0.3.1.

International audience; Chemical and biological reactions at fluid-solid interfaces are central to a broad range of porous material applications and research. Pore-scale solute transport limitations can reduce reaction rates, with marked consequences for a wide spectrum of natural and engineered processes. Recent advances show that chaotic mixing occurs spontaneously in porous media, but its impact on surface reactions is unknown. We show that pore-scale chaotic mixing significantly increases reaction efficiency compared to nonchaotic flows. We find that reaction rates are well described in terms of diffusive first-passage times of reactants to the solid interface subjected to a stochastic restart process resulting from Lagrangian chaos. Under chaotic mixing, the shear layer at no-slip interfaces sets the restart rate and leads to a characteristic scaling of reaction efficiency with Péclet number, in excellent agreement with numerical simulations. Reaction rates are insensitive to the flow topology as long as flow is chaotic, suggesting the relevance of this process to a broad range of porous materials.

In the context of global change and enhanced toxic cyanobacterial blooms, cyanobacterial transfer to estuaries is likely to increase in frequency and intensity and impact animal and human health. Therefore, it is important to evaluate the potential of their survival in estuaries. In particular, we tested if the colonial form generally observed in natural blooms enhanced the resistance to salinity shock compared to the unicellular form generally observed in isolated strains. We tested the impact of salinity on two colonial strains of Microcystis aeruginosa, producing different amounts of mucilage by combining classical batch methods with a novel microplate approach. We demonstrate that the collective organization of these pluricellular colonies improves their ability to cope with osmotic shock when compared to unicellular strains. The effect of a sudden high salinity increase (S ≥ 20) over 5 to 6 days had several impacts on the morphology of M. aeruginosa colonies. For both strains, we observed a gradual increase in colony size and a gradual decrease in intercellular spacing. For one strain, we also observed a decrease in cell diameter with an increase in mucilage extent. The pluricellular colonies formed by both strains could withstand higher salinities than unicellular strains studied previously. In particular, the strain producing more mucilage displayed a sustained autofluorescence even at S = 20, a limit that is higher than the most robust unicellular strain. These results imply survival and possible M. aeruginosa proliferation in mesohaline estuaries.

International audience; The Asian monsoons are triggered by complex interactions between the atmosphere, Asian and African orography, and the surrounding oceans, resulting in highly seasonal climate and specific regional features. It was thought that the Asian monsoon was established during the Neogene, but recent evidence for monsoon-like precipitation seasonality occurring as early as the Paleogene greenhouse period challenges this paradigm. The possible occurrence of monsoons in a climatic and paleogeographic context very different from the present-day questions our understanding of the drivers underpinning this atmospheric phenomenon, in particular with regard to its dependence on geography. In this study, we first take advantage of the wealth of new studies to tentatively draw an up-to-date picture of Asian tectonic and paleoenvironmental evolution throughout the Cenozoic. We then analyze a set of 20 paleoclimate simulations spanning the late Eocene to latest Miocene ( 40–8 Ma) in order to better understand the evolution of the distinct Asian monsoon subsystems. At odds with the traditional view of a monsoonal evolution driven mainly by Himalayan-Tibetan uplift, our work emphasizes the importance of peripheral mountain ranges in driving the evolution of Asian climate. In particular, the uplift of East African and Anatolian-Iranian mountain ranges, as well as the emergence of the Arabian Peninsula, contribute to shaping the modern South Asian summer monsoon. We also suggest that East Asian monsoon establishment and the aridification of inland Asia are driven by a combination of factors including increasing continentality, the orographic evolution of the Tibetan Plateau, Mongolia, Tian Shan and Pamir, and decrease during the Cenozoic.

During the last glacial period, the climate shift to cold conditions associated with changes in atmospheric circulation and vegetation cover resulted in the development of large aeolian systems in Europe. On a regional scale, many factors may have influenced dust dynamics, such as the latitudinal difference between the various aeolian systems and the variability of the sources of wind-transported particles. Therefore, the assumption that the timing of aeolian deposition is strictly synchronous in Europe does not seem to be the most plausible hypothesis and needs to be evaluated. To test this assumption, the chronology of loess deposition in different European regions was investigated by studying 93 luminescence-dated loess-palaeosol sequences with their data recalculated and compiled in a single CSV file: the ChronoLoess database. Our study shows that the two major aeolian systems, the Northern European Loess Belt (NELB) on the one hand and the systems associated with the rivers draining the Alpine Ice Sheet on the other hand, developed asynchronously. The significant deposition started at about 32 ka for the NELB vs 40 ka for the perialpine loess and peaked about two millennia later for the former (21.8 ka vs 23.9 ka, respectively). This shift resulted mainly from the time lag between the maxima of the Alpine and Fennoscandian ice sheets, which acted as the primary sources of fine-grained particles through glacial abrasion. The major geomorphic changes that resulted from the development and decay of the Fennoscandian and British-Irish ice sheets also played an important role. Particularly, ice sheet coalescence during the LGM diverted meltwater fluxes through the Manche River and provided vast amounts of glacial particles available for deflation in the western NELB. The period during which the maximum Mass Accumulation Rate was reached for each loess-palaeosol sequence is relatively homogeneous in the NELB and ranges from 30 ka to 19 ka, whereas it is more scattered in the perialpine systems (>60 ka to 14 ka). This probably resulted from a combination of factors, including the asynchrony of maximum valley glacier advances and local geomorphic factors.

The interval from the Valanginian to the Barremian stages (137–121 Ma; Early Cretaceous) is punctuated by several episodes of environmental changes, accompanied by shifts in weathering intensity on the continents and changes in the Tethyan neritic carbonate production. We synthetize 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), anchored to 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 from belemnites and proxies of detrital supply in the Tethyan area (Vocontian Basin and Subbetic Domain). From this compilation, we show that the episodes of environmental changes are paced by a 2.4-Myr cycle and, with a lower amplitude, a 1.2-Myr cycle. In addition, the new time scale shows the synchronicity between the Weissert Event and the Parana-Etendeka Large Igneous Province. In the series of carbon-isotope ratios measured on belemnite rostra, the amplitude of the 2.4-Myr cycle is twice higher during the Valanginian than in the Late Barremian and three times higher than in the Hauterivian and Early Barremian, suggesting that the activity of the Parana-Etendeka Large Igneous Province amplified the initial orbital forcing to trigger the environmental 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 Andean and 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. Integrated astrochronology 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; The 12 m thick sequence of calcareous slope deposits and palaeosols exposed in a quarry at Verteuil (southwest France) has been studied and dated by optically stimulated luminescence. Emphasis was given to the identification and characterisation of palaeosols through geochemistry and micromorphology. The main clastic units, separated by major unconformities, were dated to MIS 6, MIS 5-4 and MIS 3-2. Stratified deposits ('grèzes litées'), consisting of alternating diamictic and matrix-free clastic beds and attributed to stacked stone-banked solifluction lobes, developed mainly after ca. 40 ka, i.e. during late MIS 3 and MIS 2. MIS 3 is recorded as a palaeosol complex including two humic A horizons overlying a chromic cambisol associated with burrows of ground squirrels, while MIS 5 corresponds to a reworked rubified chromic cambisol. Overall, this sequence shows similarities with the clastic deposits found in regional cave porches and rock shelters, strongly suggesting that anthropogenic activities did not significantly modify the climate-driven sedimentary and soil-forming processes at the Palaeolithic sites.

International audience; The monitoring of temporal variabilities of groundwater flows is a critical point in many hydrogeological contexts, especially for the characterization of coastal aquifers, sub-surface heterogeneities or else groundwater/stream interactions. Considering the lack of available methods, we investigate the possibility of monitoring and quantifying groundwater fluxes variations over time through active-Distributed Temperature Sensing (DTS) measurements. Active-DTS, consisting in heating a fiber optic cable, performs very well for investigating the spatial distribution of groundwater fluxes but the method has never been tested to continuously monitor groundwater fluxes changes. In this context, both numerical simulations and sandbox experiments were performed in order to assess the sensitivity of temperature elevation to variable flow conditions. Results first demonstrate that when a flow change is followed by a long-enough steady-state flow stage the temperature elevation stabilizes independently of previous fluxes conditions. Thus, the stabilization temperature can easily be interpreted to estimate groundwater fluxes using the analytical model commonly used under steady flow conditions to interpret active-DTS measurements. Under certain flow conditions, depending on the nature of flow variations, the approach also allows the continuous monitoring of fluxes variations over time. If instantaneous flow changes occur, the superposition principle can even be used to reproduce the temperature signal over time. In summary, we demonstrated through these preliminary results the possibility of for monitoring and/or quantifying the temporal dynamic of groundwater fluxes at different temporal scales including diurnal and periodic fluxes variations, which open very interesting perspectives for the quantification of subsurface processes.

The anaerobic digestion industry is currently in development and enables the energetic valorization of organic waste products (OWP) to generate biogas. A co-product of this process, digestate, is more and more produced and can be recycled on agricultural lands as a low-cost alternative to mineral fertilizers. Thus, the organic carbon (C) it contains could improve the soil quality and store C in subsoil through dissolved organic C (DOC) transfers. Biogas digestate is a recent OWP characterized by a chemical composition rich in recalcitrant molecules and little is known about its impacts on dissolved fluxes in the scientific literature.In order to evaluate the impacts of biogas digestate and winter crop on DOC and nitrates fluxes in soil, the experimental site EFELE from the SOERE PRO network (https://www6.inra.fr/valor-pro) was followed. The long-term evolution of the repeated application of OWP since 2012 was assessed for three different treatments: pig slurry, biogas digestate from the anaerobic digestion of pig slurry and a mineral fertilizer as a control. Lysimeters were monitored from 2014 to 2022 (8 drainage seasons) with two replicates per modality and depth (40 and 90 cm) under winter cover of wheat or mustard. The drainage seasons lasted from November to April. The DOC and nitrates dynamics observed for the four years under wheat and the four years under mustard were repeatable. Nitrates leaching losses were low under mustard (2.7 ± 2.3 kg N.ha-1 at 40cm and 0.9 ± 0.8 at 90cm), which had fulfilled its role as a catch crop, and higher under wheat (30.5 ± 12.9 kg N.ha-1 at 40cm and 14.3 ± 10.1 at 90cm), regardless of treatment. Regarding the DOC fluxes at 40cm depth, there was a significant difference between mustard (34.0 ± 11.4 kg C.ha-1) and wheat (20.6 ± 11.1 kg C.ha-1). DOC fluxes under biogas digestate were significantly higher (36.3 ± 16.2 kg C.ha-1) than under mineral fertilizer and pig slurry (21.4 ± 7.4 kg C.ha-1 on average). At the beginning of the drainage season, the DOC concentrations dynamics were already significantly different between digestate and the two other treatments under mustard, which was sown in September and already well developed. Under wheat, which was sown in November, there was no difference between treatments at the beginning of the season. It was only in the middle of winter, when the crop had more time to develop, that a difference could be observed. It seemed that the crop effect controlled the treatment effect. DOC fluxes to groundwater (90 cm) were not significantly different between treatments or crop (7.4 ± 6.0 kg C.ha-1 on average). Part of the C could be stored between 40cm and 90cm depth or mineralized.

Determination of the depositional age of sediments provides the basis for much of the current understanding of tectonic processes, paleoclimate, and other aspects that relate to time. Integrated the high-resolution magnetostratigraphy with independent means of age control (e.g., biostratigraphy, tephrostratigraphy), the age model of the sedimentary sequences can generally be constrained. However, as the paleomagnetic correlation to the Geomagnetic Polarity Time Scale (GPTS) is usually non-unique, magnetostratigraphy alone usually leads to dramatically different age models for the siliclastic sequences in the absence of fossils or volcanic ash layers, likely resulting in diverse tectonic and paleoclimate reconstructions. This challenge presented by different age models is well-exemplified in the debated Cenozoic terrestrial strata in Central Asia, resulting in competing models that account for the growth of the Tibetan plateau and its association with aridification history of Central Asia. Here we develop a new approach to evaluate the age model of the tephras- and fossils-free strata by checking the potential link between syntectonic sedimentation in the basin and the rapid exhumation of basement rocks. By comparing the initiation of growth strata with the onset timing of the rapid exhumation revealed by the low-temperature thermochronology, we validate this method in the regions (e.g., Zagros fold-and-thrust belt and Ruby Mountains metamorphic core complex) where the age models for the strata have been well-constrained. Applying this approach to the debated age models of the strata in the Tarim and Qaidam basins, we constrain the depositional age of Paleogene syntectonic strata, indicating a Paleocene-Eocene initial and an Oligocene-Miocene intensified mountain building process along the northern margin of the Tibetan plateau. Integrating the timing of Paleogene tectonism along the northern Tibetan plateau with Proto-Paratethys Sea fluctuations history, we highlight the significant role of tectonism in the retreat of proto-Paratethys Sea as well as its influence on the aridification in Central Asia.

International audience; In continental subsurface environments, biogeochemical reactions drive nutrient delivery, deep microbial life and mineral weathering, with crucial importance in the critical zone. Current models often simplify groundwater transport, using the residence time approach or hillslope models. However, increasing observations suggest that the nature, location and efficiency of reactions are strongly affected by groundwater 3D flow patterns, chemical gradients and subsurface heterogeneity. Here, we investigate how hydrological and geological structures control where and when biogeochemical reactions occur in the deep critical zone. For this purpose, our approach integrates long-term and widespread local observations in a catchment-scale framework and is based on data from two critical zone observatories of the French OZCAR national network. The first study took place in Guadeloupe (Obsera), where we integrated geophysical, hydrological and geochemical data in a reactive-hydrogeological model to simulate the 3D structure of groundwater flow paths and weathering. We found that the downstream evolution of the river chemistry is controlled by the pattern of hydrogeological circulations and by the depth of the weathering front. Furthermore, the calibrated 3D model allowed the delimitation of areas where weathering occurs and we showed that active weathering is restricted to catchment-areas where downward groundwater flows are deep. The second study focused on the dynamics of dissolved oxygen (DO) in a fractured aquifer at the Ploemeur catchment (Bretagne, France). Deep and intermittent inputs of DO in groundwater were observed, enabling the reaction of DO with dissolved Fe2+, in turn sustaining the development of deep microbial communities. In this study, we designed a simple model to simulate jointly the depth-distribution of DO and Fe2+ and to investigate the hydrological and geological factors controlling the DO depth-distribution. We found that the reducing capacity of the bedrock and the mean fluid transit time are the main parameters to explain and predict the depth of the oxic-anoxic transition in crystalline environments. In this presentation, we will provide new perspectives to observe and understand the origin of subsurface biogeochemical reactions and we will illustrate key processes that breakdown classical assumptions of reactive groundwater models.

Duricrusts are hard elemental layers forming in tropical and subtropical regions. Different types of duricrusts exist, including calcretes, silcretes and ferricretes (or iron duricrusts), that differ by their composition and, most likely, their formation mechanism. In places such as Africa, Australia or Brazil, we can observe them capping hills and protecting landscapes, thus being an important part of regional geomorphology. Their formation is highly dependent on climate and requires strong seasonal precipitation cycles, enabling transport and accumulation of elements during wet seasons and precipitation and hardening during dry seasons. However, it is also known that duricrusts form in tectonically quiet environments, and multiple tens of thousands of years are needed to form centimetres to metres thick elemental layers. Two hypotheses for duricrust formation exist, namely the water table (or horizontal) hypothesis and the laterite (or vertical) hypothesis. Yet, until recently, no quantitative (numerical) model exists that represents either of them. We presented last year (Fenske et al, 2022) a model based on the water table hypothesis. Here we present a second model based on the laterite hypothesis and compare the predictions of the two models. Although the models we propose are potentially applicable to a wide range of duricrusts, we will concentrate here on the formation of ferricretes.Laterites are a type of regolith covering around 33\% of land surfaces. The thickest lateritic profiles are found in the centre of continental cratons, where they evolved for millions of years. The main process responsible for laterisation is weathering, the process transforming bedrock into regolith. During weathering rocks progressively lose their structure, elements are dissolved, re-precipitated, leached, or transported, leading to progressive porification and compaction. Subsequently, from the weathering front to the surface, a typical lateritic profile is made of coarse grained and then fine grained saprolite, a mottled zone and at the top, an indurated cover, the ferricrete. We recently developed a numerical model for duricrust formation according to the laterisation hypothesis (LT model). In this model, iron duricrusts are genetically linked to the bed rock. Material from the bedrock are transformed and leached within a given vertical column of rocks but are also moved vertically due to tectonic uplift. We assume that as the regolith ages, it undergoes a process of transformation that is proportional to mean fluid flow and that leads to hardening and compaction. As material is constantly removed from the regolith layer, the model is dependant on a constant material input (through uplift and, potentially, surface erosion) to reach sufficient laterisation for ferricrete formation. Comparing predictions of the laterisation (LT) model to those of the water table (WT) model, we observe that they require slightly different tectonic regime, with the WT model most efficient during period of complete quiescence and the LT model needing a slow constant rate of base level fall to produce duricrusts. The two models also differ by the geometry of the duricrusts they predict and, in particular, the depth at which duricrust forms in the regolith (at or above the water table level).

Integrating hydrology in Landscapes Evolution Models (LEMs) is challenging. The drainage-area-based solutions, where drainage area weighted by precipitation rates approximate the amount of water flowing through every location, accumulates drainage-area downstream following the topographic gradient and has been empirically linked to observed discharge. While straightforward and computationally efficient, it implicitly includes hydrology without calculating discharge or water height. A more sophisticated solution consist in the direct calculation of the shallow water equation, which explicitly approximates water height and discharge using physics-based equations. While the latter bears more information about the channels and floodplains dynamics, it is inherently limited to short time scales and is computationally more expensive, with numerical time step typically of the order of the second – making its use for long-term LEMs particularly challenging. Here, we present GraphFlood, a fast iterative method computing river depth and water discharge in 2D on a digital elevation model (DEM). This new method leverages the Directed Acyclic Graph (DAG) nature of water flowing on surface topography to iteratively solve for the 2D shallow water equation without the inertia terms. The main idea of the algorithm is to find the correct water surface height by iteratively balancing discharge input and output. At each iteration, we first use fast DAGs-related algorithms to calculate flow accumulation on the hydraulic surface. We use this as an approximation of the discharge input. Then, the discharge output is calculated using the Manning flow resistance equation, in a manner similar to the Floodos model (Davy et al., 2017). The divergence of the discharges increments the water height. The iterative process is repeated until reaching a stationary state, i.e. a static field of water height and discharge representing an equilibrium state. Note that this method can be slightly modified to solve flood wave propagation by approximating the input discharge function of the immediate upstream neighbours. Water depths obtained with the stationary solution were validated against an analytical solution in the case of a rectangular channel and with the Floodos model for natural DEMs. Compared to previous hydrodynamic models, the main benefits of GraphFlood are its simplicity of implementation, which mainly requires a classical flow routing algorithm, and its efficiency. While case-dependent, our tests suggested a ~10 times speed-up compared to Floodos model (Davy et al., 2017) which was already significantly faster than other hydrodynamic models. Moreover, the computational time scales a little more than linearly with the number of cells, which makes GraphFlood a suitable solution even for DEMs larger than 106 – 107 cells. We demonstrate the suitability of the method for integrating realistic hydrology in a wide range of topographic and morphometric analyses (e.g. channel width assessment, floodplain delineation, Flint-Morisawa metrics) and in LEMs – even for longer timescales.

From the end of the Carboniferous onwards, the over-thickened and hot Variscan crust collapsed (late-orogenic collapse), accompanied by the rise of high-grade metamorphic domes along low-angle detachment faults and the development of mainly half-graben or pull-apart type asymmetric intramountain coal basins.These Carboniferous-Permian late orogenic basins widely developed around 300 Ma and were filled with siliciclastic continental material, accompanied by a widespread intrusive and extrusive magmatic activity. These basins crop out in the internal parts of the belt south of the Variscan Front in several limited locations in and around the Variscan basement of Western Europe (Massif Central, Vosges-Black Forest, Alps, Harz). They occur as small isolated and disconnected “basins” with incomplete sedimentary series. Their present-day area does not reflect their initial extent and thickness, which can be explored by studying their subsurface prolongation beneath their Meso-Cenozoic sedimentary covers.We propose a geological overview of the late Variscan Carboniferous-Permian Brécy basin (SW Paris basin, France), based on the reprocessing and interpretation of vintage seismic lines and related deep boreholes. We aim (i) to discuss its sedimentary filling, which is hidden beneath the Meso-Cenozoic cover of the Paris basin, (ii) to present thickness maps of its 3.9 km-thick sedimentary filling, and (iii) to describe its structural extensional features related to a syn- to post-rift tectonic scenario. We finally compared our new results to other Carboniferous-Permian deposits in France (to discuss its lateral correlation with neighboring basins) and northwest Europe, suggesting that the Brécy Basin may represent - due to its thickness and location - a missing link between late Variscan basins in southern and northern Europe.

International audience; Terra Antiqua is a plugin for QGIS to make paleogeographic reconstructions with a user-friendly graphical interface. The goal of Terra Antiqua is to make paleogeographic reconstructions accessible and attractive to a much wider range of users, typically Earth and Life scientists and students, without extensive expertise in programming and GIS analyses. Yet Terra Antiqua can also be attractive for GIS developers as our reconstruction algorithms are accessible through application programming interfaces (APIs), open source Github repository and written in python with open standards (e.g. OpenLayers, OGC, GDAL). Starting from physiographic features and datasets rotated back to the desired reconstructed age (typically using Gplates), the previous release of Terra Antiqua offered a set of primary tools to run the main steps of a global reconstruction (1. Combine topo-/bathymetry, 2. Set Paleoshorelines, 3. Modify topo/bathymetry and 4. Create topo/bathymetry) and secondary tools to improve and enhance the result. From this first simple release we are incrementally adding tools and features inspired by various methods developed by experienced paleogeographers. The new release, Terra Antiqua 2.0, has integrated a new set of options on the existing tools, including the ability to create physically realistic geomorphic features. These new options will be presented within the controversial example of the reconstruction of the India-Collision and the development of the Tibetan-Himalayan orogen. Several reconstructions stemming from competing topographic and geodynamic models are thus compared and assessed based on compiled datasets including updated paleoaltimetry.

Radial microcracks surrounding retrogressed SiO2 inclusions in UHP garnets are key microstructural observations allowing to constrain the mechanisms of exhumation of ultra-high-pressure (UHP) rocks. The major challenge lies in identifying whether the microstructures formed during their ascent from mantle depths, or as a consequence of transient variations in the tectonic regime. By combining petrographic observations, petrochronological data and numerical thermo-mechanical modelling, we show that radial cracks around SiO2 inclusions in ultrahigh-pressure garnets from Dora Maira are caused by ultrafast decompression during the early stage of exhumation (< 0.5 Ma). Decompression rates higher than 10-14 s-1 are, for the first time, inferred from natural microstructures independently of current petrochronological estimates1. We demonstrate that the SiO2 phase transition generates shear stresses sufficiently large to trigger plastic yielding, resulting in the generation and propagation of radial and bent shear bands, mimicking the fractures observed in UHP garnet. Our results question the traditional interpretation of the exhumation from great depth of ultrahigh-pressure tectonic. Instead, we propose that such ultrafast decompression rates are related to transient changes in the stress state of the buried continental lithosphere, favoring an exhumation mechanism involving nappe stacking. 1 Rubatto, D. & Hermann, J. Exhumation as fast as subduction? Geology 29, 3–6 (2001).

Active faults accommodate tectonic plate motion through different slip modes, some stable and aseismic, others characterized by the occurrence of large earthquakes after long periods of inactivity. Although the slip mode estimation is of primary importance to improve seismic hazard assessment, this parameter inferred today from geodetic observations needs to be better constrained over many seismic cycles. From an analytical formulation developed for analyzing fault scarp formation and degradation in loosely consolidated material, we show that the final topographic shape generated by one earthquake rupture or by creep (i.e., continuous slip) deviates by as much as 10–20%, despite a similar cumulated slip and a constant diffusion coefficient. This result opens up the theoretical possibility of inverting, not only the cumulated slip or averaged slip rate, but also the number of earthquakes and their sizes from scarp morphologies. This approach is all the more relevant as the number of rupture events is limited. Estimating the fault slip history beyond a dozen earthquakes becomes very difficult as the effect of erosion on scarp morphology prevails. Our modeling also highlights the importance of trade-offs between fault slip history and diffusive processes. An identical topographic profile can be obtained either with a stable fault creep associated with rapid erosion, or a single earthquake rupture followed by slow erosion. These inferences, derived from the simplest possible diffusion model, are likely to be even more pronounced in nature.

Since the end of the 19th century, geomorphologists have been on a relentless quest to unravel the mysteries of landscape evolution and explain the diversity of the resulting forms. However, a quantitative model of landscape morphodynamics that is relatively universal and applicable at various time scales still eludes us. This raises an important question: are we, geomorphologists, dumber than the average scientist, or is landscape evolution particularly complex to decipher? ChatGPT tells us that, indeed, landscape evolution is complex. As for many natural phenomena, the complexity of landscape evolution results from 3 elementary components: processes, stochasticity, and heterogeneity. Process geomorphology tackles the complex morphodynamics emerging from the diversity and interactions of physical, chemical, and biological processes that shape the Earth. Stochastic geomorphology addresses the role of fluctuations in the drivers of landscape evolution, such as the frequency-magnitude distribution of precipitation events, landslides, earthquakes, or fires. Heterogeneous geomorphology embraces the variable nature of the properties of landscape elements on which geomorphic processes operate or that they create. This includes, for instance, the distribution of grain sizes, the diversity of rock type, the fractal nature of rock fractures, or the spatial variations in vegetation size and type.Accounting for all these sources of complexity, inasmuch as they can be quantified, is an untractable problem resulting in models of little explainability. Therefore, hypotheses had been and must be formulated to simplify the problem of landscape evolution comprehension and modeling. There is, arguably, a long tradition of emphasizing process complexity to explain landscape dynamics, neglecting or simplifying both stochastic fluctuations and heterogeneity. In this lecture, I shall discuss this view, emphasizing the now well-established importance of stochastic fluctuations, and how little we know of the role of heterogeneity.On this latter topic, I shall illustrate with a variety of examples how time series of high-resolution and high-precision topographic data (4D data) offers unprecedented insights into landscape morphodynamics. Beyond quantifying and detecting a variety of processes and their temporal fluctuations, 4D data allow a systematic quantification of the heterogeneity (e.g., vegetation, grain size, ...) of landscape elements, and spatial variability of geomorphic rates, thus bringing us closer to formulating the role of heterogeneity in landscape dynamics. Yet, this goal can only be achieved if tools to harness the complexity and richness of high-resolution topographic data are developed and made available.Keywords: fluvial incision, landslides, floods, salt marshes, topo-(bathymetric) LiDAR, numerical modeling, machine learning.

Being the world’s largest freshwater resource, groundwater is at a continuous risk of overabstraction for human water use. Beside substantial drops in groundwater levels that are the consequence of unsustainable groundwater abstraction, which modify the recharge/discharge relationships between large-scale hydrogeological units, this anthropogenic hydraulic forcing is also responsible for changes in thermal regimes within the critical zone. While the impact of global groundwater pumping on the hydrogeological cycle has long been demonstrated, we still have insufficient knowledge on the influence of human activities on groundwater temperatures and, as a consequence, on stream thermal regimes and groundwater quality.In this contribution we discuss temperature anomalies that develop in the shallow subsurface as a result of localized groundwater extraction. We study different hydrogeological settings, i.e., porous and fractured aquifers, that we explore via numerical modelling and comparison with field observations. In the field, we use repeated temperature-depth borehole profiles separated by decades, the advantage of which is that differencing the temperature logs for individual boreholes yields real temperature change and eliminates steady-state sources of curvature. Thus, it enables us to detect changes in subsurface thermal regimes, resulting from transient conditions, i.e., climate change and changes in groundwater hydrodynamics.

The Cenozoic history of the Tibetan Plateau topography is critical for understanding the evolution of the Indian-Eurasian collision, climate, and biodiversity. However, the long-term growth and landscape evolution of the Tibetan Plateau remains ambiguous, it remains unclear if plateau uplift occurred soon after the India-Asia collision in the Paleogene or later in the Neogene. As the landscape evolution is controlled mainly by mountain uplift and surface processes, the present-day river profiles and the drainage basin geometries preserve important information that can be extracted to infer the long-term history of mountain uplift with numerical models. Here we focus on the southeastern (SE) Tibetan Plateau where three of the world’s largest rivers draining the Tibetan Plateau (the Yangtze, Mekong, and Salween Rivers, i.e., Three Rivers) have incised deep valleys with distinctive geomorphic signatures. We reproduce the uplift history of the SE Tibetan Plateau using a 2D landscape evolution model, which simultaneously solves fluvial erosion and sediment transport processes in the drainage basins of the Three Rivers region. Our model was optimized through a formal inverse analysis with a large number of forward simulations, which aims to reconcile the transient states of the present-day river profiles. The modeling results were ultimately compared to existing thermochronologic and paleoelevation datasets to help decipher between competing tectonic models that predict contrasting topographic evolutions. Our results suggest initially low elevations during the Paleogene, followed by a gradual southeastward propagation of topographic uplift of the plateau margin until present day. The modeling thus does not support Paleogene formation of the SE Tibetan Plateau with a major subsequent degradation via upstream fluvial erosion. The scenario with pre-existing high-elevation plateau or plateau degradation will result in much wider river channels with knickpoints that propagated upstream much further away from the plateau margin compared to observed river profiles. The quantitative constraints on landscape evolution achieved based on drainage patterns in SE Tibet indicate a powerful tool potentially applicable to other regions to infer important implications for the evolution of Indian-Eurasian collision, Asian monsoons, and biodiversity, as well as the geodynamic forces involved in collisional orogens.

Eclogitization constitutes one of the most emblematic transformations in continental subduction zones, where conversion of initially dry lower crustal rocks into eclogite facies rocks correlates with the occurrence of seismogenic events. This reaction is generally considered to occur at high pressure conditions during hydration of dry granulite. Several models using « ad hoc » diffusion equation exist to model this hydration process and the consequences of reaction-induced changes in terms of rheology and density. However, to our knowledge, there is no quantitative model allowing to physically explain how fluids propagate inside a dry rock (i.e. with no porosity at all) and how reaction-induced alteration front widens over time. In this study, we therefore propose a new fully coupled hydro-chemical model wherein a two-phase flow model is coupled with the eclogitization reaction. We use a mass conservative approach, solving total mass and solid mass equations, in a closed isothermal system. Fluid and solid densities are calculated with lookup tables from equilibrium thermodynamics. Our model shows that a fluid pressure pulse generates a pressure gradient that can be associated with the densification reaction when the pressure required for the eclogitization is reached. This reaction generates a large increase in porosity (0 to ~16%) and subsequent porous fluid flow inside the initially dry granulite. This process is then sustained as long as the fluid pulse is maintained, and ends shortly after the fluid pressure pulse stops. However, high pressure within the reacted area can persist for a long period of time. A parametric study allowing to constrain both the duration and the widening of the reaction area is proposed as well as an application to the emblematic case study of the eclogitized granulites of Holsnoy (Bergen Arcs, Norway).

International audience; The knowledge acquired on the exhumation of the Pyrenean chain and the evolution of the adjacent foreland basins makes this Alpine-type domain a good laboratory to better constrain a full sediment routing system in a compressive context and to apprehend the driving processes controlling the sediment routing in space and time. This integrated approach aims at enhancing our basin mastering approach as well as improving our predictions of reservoir properties. This Source-to-Sink study seeks to understand the evolution of sedimentary routing from the Source (orogenic relief, craton, basin recycling) through the transfer zone (peripheral or internal to the basin) to the final sink (flexural basin, deep turbiditic margin). Within this new cartography, we propose to compile the data over the entire peri-Pyrenean domain. We produced large scale quantitative and qualitative maps to better observe and interpret the tectonic, climatic and surface processes impacts of the SRS behavior. These maps include kinematic reconstructions of the Iberian-European-Mediterranean system, restored sequential cross-sections, history/magnitude of exhumation by thermochronology, source tracking, characterization of weathering and erosion surfaces, synthesis of the major structures activity, paleogeographic reconstructions, analysis of sedimentary geometries and transport directions as well as the quantification of volumes preserved in the basins. Their interpretation is combined with a time representation along the routing system, linking classical basin wheeler diagram representation to source erosion and lithologies to obtain a continuous view on the sediment journey. The time steps chosen for these 5 maps account for the different stages of tectono-sedimentary evolution of the peri-Pyrenean system at the early-, syn- and post-orogenic stages. The compilations carried out compare exhumed domains and sedimentation zones in terms of fluxes and volumes and make it possible to map the routing systems and point out the main drivers for the surface evolution during the construction/destruction cycle of an orogen. Research work financed and carried out as part of the BRGM-TOTAL Source-to-Sink program

The study of heat transport in porous media has recently attracted a lot of attention due to the wide range of industrial and geological applications, yet the impact of the structural heterogeneity of naturally occurring aquifers on their hydraulic and thermal properties is often disregarded. In that regard, a novel application of phosphor thermometry to porous media is proposed with the aim of examining under which conditions the validity of existing thermal transfer models in complex natural saturated porous media can be questioned. This experimental technique relies on monitoring the temperature-dependent luminescence properties of solid phosphor particles seeded into the fluid as tracers, using light sources and cameras. It offers the possibility of characterizing quantitatively the interaction between flow and heat transport processes at the pore scale in transparent analog porous media, with minimal interference and from spatially-resolved measurements, hereby overcoming the technical limitations of current experimental techniques, which are constrained to point temperature measurements.Here, as proof of concept, we present a demonstration experiment performed on a slow-moving flow in a synthetic porous medium with a heterogenous size distribution, and using YAG:Cr3+, a thermographic phosphor with a temperature sensitivity exceeding 0.3%/K [1]. The measurements are performed using a modulated light source and are recorded at a sampling rate of 1 kHz during continuous injection of an aqueous solution which is initially at a constant temperature, different from that of the resident solution. The results show the dynamics of the spatial temperature distribution in the porous medium with a precision of ±0.3°C.[1] J. L. Bonilla and B. Fond, "Phosphor thermometry using the phase-shift method: optimization and comparison with decay time method," 2022.

Repeated alpine glaciations during the Quaternary partly reached far into the foreland and caused profound landscape changes beyond glacial margins in northern Switzerland. Climate-driven glacier growth and decay and commensurate variations in water and sediment delivery caused river systems to aggrade and to incise, leading to the widespread occurrence of glacio-fluvial deposits (Deckenschotter) and associated terraces. Mapping and numerical dating of these depositional complexes increasingly offer insights into the spatial patterns and timing of Quaternary glaciations, and associated changes in (glacio-)fluvial dynamics. An improved understanding of how fluvial systems respond to glacial-interglacial cycles will help to assess the erosion potential around repository sites of nuclear waste over the next one million years. In this study, we contribute to close this research gap using numerical landscape evolution modelling (LEM).We use EROS, a numerical landscape evolution model, which implements a particle-based approach to simulate water and sediment fluxes that interact with topography through erosive and depositional actions. Unlike LEMs based on the stream-power incision law, the method solves the 2D shallow water equations with both basal and lateral erosion and deposition, which allows for variations in width and lateral mobility of rivers; these variations induce changes in the transport capacity of the sediments that cause specific patterns of deposition and erosion to emerge. We adjusted the model so that it is capable to run over 1 Myrs, and imposed boundary conditions that - informed by estimates on longterm erosion rates – reflect rock uplift and plausible variations in water and sediment fluxes following a 100-kyrs glacial cycle. Our model relies on digital elevation models and sediment thickness data with 60 m spatial resolution and is applied to the Hochrhein river between Stein am Rhein and Basel and the Aare river downstream of the area, where Limmat and Reuss enter.Our simulations show that the model reproduces widespread aggradation, reworking of the sediments by highly laterally mobile, braided river systems and incision during periods of increased runoff and low sediment availability.Our model setup and parametrization features several uncertainties. For example, the capacity of rivers to laterally erode strongly determines the thickness and extent of depositional complexes lining the Hochrhein and Aare system. Also, our model is sensitive to temporally varying boundary conditions of water and sediment input about which precise estimates are lacking. Regardless, the more detailed and realistic representation of hydraulic and sediment transport processes by EROS compared to conventionally used landscape evolution models at this spatial and temporal scale provide the opportunity to test different hypotheses using numerical experiments and link the results to field evidence. Further sensitivity analyses and uncertainty quantification will enable us to use our model as simulation tool to hindcast and investigate the behaviour of fluvial system in response to different tectonic and climatic scenarios, thus helping to better understand potential spatial patterns of and sediment assemblages within widespread glacio-fluvial deposits.

Stream water chemistry at catchment outlets is commonly used to infer the flowpaths of water through the catchment and to quantify the relative contributions of various flowpaths and/or end-members during, e.g., storm events. For this purpose, the number and nature of these flowpaths or end-members are commonly defined a priori as part of the experimental design and previous knowledge, and their contributions are calculated based on the dynamics of the stream chemistry, with the inherent assumptions and uncertainties of this approach. Here, we present a methodology, which inverts this classical approach. We use the variability of the stream chemistry data to determine the minimum number of end-members needed and, more specifically, whether two end-members would be sufficient. In this methodology, we analysed the concentration-concentration relationships of several major ion combinations on the storm-event scale for multiple events, using a multi-year, high-frequency (< 60 minutes) timeseries of the major cations and anions from the outlet of two small (0.8 – 5 km²) french catchments with contrasting land-use (forest and mixed farming-cropping productions). The results indicate that a large number of storm-events (up to 92%) could be interpreted as the result of only two end-members, depending on the catchment and the ion combination used. These findings might help to revise some of the perceptual understandings of flowpath or end-member contributions in catchments during storm-events. In addition, they might stimulate the discussion about the definition of end-members or flowpaths in catchments, especially with regard to variable hydrological contributions.

Hydrological predictions for ungauged basins at catchment and regional scales are still challenged by the lack of available data. Under the assumption that the perennial stream network is mostly fed by groundwaters, its spatial extent is controlled by the magnitude of the subsurface hydraulic conductivity (K) with respect to the actual recharge rate (R). In addition, the residence time of groundwater is directly controlled by the storage capacity of the aquifer system, i.e. the porosity (Ө). Here we propose a new inversion approach that jointly considers the spatial organization of observed hydrographic network and the residence times of groundwater measured at springs to infer the geometry of the aquifer system and its hydraulic properties.We used a dataset gathered in an alpine catchment observatory (Natural conservation area of the Massif of Saint-Barthélemy, Pyrenees, France). The extent of the stream network has been mapped using field observation. Residence times have been obtained from concentrations of dissolved CFCs and SF6 gases measured at 6 spring locations distributed over the catchment. The average transit time is about 30 years for perennial springs with a significant variability across the watershed. The relatively high residence time is also confirmed by high Helium concentrations.In our inversion scheme, we evaluate the accuracy of an ensemble of 3D hydrogeological models with different aquifer geometries and hydraulic properties. We found that topography and aquifer compartmentalization, through the decreasing trend in hydraulic conductivity, are key parameters in setting the spatial pattern of seepage areas and the distribution of transit times across the catchment. In addition, by running transient simulations of the model ensemble we further explore the accuracy of the models by comparing results with measurements of stream discharge and the intermittency of the hydrographic network. We found that intermittence seems to be connected to high transmissive shallow flow structures with low storage capacities (mostly organized within shallow soils and rockslides). However, perennial springs are sustained by deep groundwater flow paths within the bedrock. In perspective, we discuss the potential evolution of the extent, discharge magnitude and the transit time of seeping groundwater under changing recharge scenarios.

Manuscript abstract: Paleoecological estimation is fundamental to the reconstruction of evolutionary and environmental histories. The ant fossil record preserves a range of species in three-dimensional fidelity and chronicles faunal turnover across the Cretaceous and Cenozoic; taxonomically rich and ecologically-diverse, ants are an exemplar system to test new methods of paleoecological estimation in evaluating hypotheses. We apply a broad extant ecomorphological dataset to evaluate Random Forest machine learning classification in predicting the total ecological breadth of extinct and enigmatic “hell ants”. In contrast to previous hypotheses of extinction-prone arboreality, we find hell ants were primarily leaf litter or ground-nesting and foraging predators, and by comparing ecospace occupations of hell ants and their extant analogues, we recover a signature of ecomorphological turnover across temporally and phylogenetically distinct lineages on opposing sides of the KPg boundary. This paleoecological predictive framework is applicable across lineages and may provide new avenues for testing hypotheses over deep time. This supplementary folder is designed to provide all raw data used in this study, and provide a workflow and code to enable duplication of our work. Descriptions of all files included are listed here, with a summary of the data file, definitions of all variables included, and relevance of the file to the work. Replication of the main statistical analyses, the Random Forests analyses predicting the ecology of extinct taxa, may be conducted using the Supplementary Data_Code file under the heading ###Random Forest analyses###, using the training datasets provided (listed as Supplementary Data_Extant Ant Morphometrics, 3 files based on type of morphometric data). The ecology of extinct species may then be predicted using the morphometric data in theSupplementary Data_Fossil Morphometrics files. Please consult the README file for further details on each included file.&nbsp

International audience; The Mesoproterozoic era is a crucial period in Earth history characterized by muted oxygen levels in the atmosphere–ocean system. This period is well represented in the non-metamorphosed sedimentary rocks from the Taoudeni Basin, Mauritania. Few studies have been carried out to trace the sources of these sedimentary archives. Here, we examined the sedimentary rocks from the Atar (S4 drill core) and El Mreiti groups (S2 and S3 drill cores). This study focuses on whole-rock elemental geochemistry and Sm/Nd isotope compositions to provide insights into the provenance of the fine-grained siliciclastic sediments from the basal part of the Mesoproterozoic Atar and El Mreiti groups. Paleoweathering indices reveal a moderate degree of chemical weathering in the source areas, consistent with the low compositional maturity of the studied samples. The concentrations of the relatively immobile trace elements suggest mixing sources of sediment provenance, which is dominated by felsic source rocks for the Atar sediments. However, distinctively positive ƐNd(t) values coupled with high 143Nd/144Nd and Sm/Nd ratios and high ƒSm/Nd values of the sediments from the El Mreiti Group indicate derivation from juvenile and less evolved sources rocks. Further, the depleted mantle model ages (TDM) of the provenance protolith (1.95–2.31 Ga) support the argument that the El Mreiti sediments are dominantly sourced from the Paleoproterozoic terrane exposed in the eastern Reguibat Shield while the Atar Group were predominantly from the Archean basement rocks in the western Reguibat Shield. Moreover, Sm/Nd isotope and mixing model results support the major contributions of the felsic Archean rocks of the Reguibat Shield for the Atar Group samples. Although these strata, separated by ∼1000 km, have been described as stratigraphic equivalent, our study demonstrates distinct sediment sources between the Atar Group strata and those of El Mreiti, therefore, reinforcing the importance of sediment provenance in understanding the evolution and reconstruction of modern and ancient sedimentary systems.

Ancient fluvial deposits typically display repetitive changes in their depositional architecture such as alternating intervals of coarse-grained highly amalgamated (HA), laterally-stacked, channel bodies, and finer-grained less amalgamated (LA), vertically-stacked, channels encased in floodplain deposits. Such patterns are usually ascribed to slower, respectively higher, rates of base level rise (accommodation). However, “upstream” factors such as water discharge and sediment flux also play a potential role in determining stratigraphic architecture, yet this possibility has never been tested despite the recent advances in the field of palaeohydraulic reconstructions from fluvial accumulations. Here, we chronicle riverbed gradient evolution within three Middle Eocene (~ 40 Ma) fluvial HA-LA sequences in the Escanilla Formation in the south-Pyrenean foreland basin. This work documents, for the first time in a fossil fluvial system, how the ancient riverbed systematically evolved from lower slopes in coarser-grained HA intervals, and higher slopes in finer-grained LA intervals, suggesting that bed slope changes were determined primarily by climate-controlled water discharge variations rather than base level changes as often hypothesized. This highlights the important connection between climate and landscape evolution and has fundamental implications for our ability to reconstruct ancient hydroclimates from the interpretation of fluvial sedimentary sequences.

International audience; Plates and the convective mantle interact with each other over geological time scales, leading to mantle flow, plate motion, and deformation along plate boundaries. At convergent boundaries undergoing subduction, the role played by mantle drag remains poorly understood despite its potential impact on subduction dynamics, and in turn on the deformation regime of the overriding plate. Previous studies were generally conducted in two dimensions, limiting their ability to faithfully reproduce processes taking place on Earth. Instead, in this study, we present 11 three-dimensional analog models of subduction at the scale of the upper mantle, including an overriding plate, and in which we control mantle drag at the base of the lower or upper plate by imposing a controlled unidirectional background mantle flow perpendicular to the trench. We systematically vary the velocity and the direction of the imposed horizontal mantle flow and quantify its impact on horizontal and vertical upper plate deformations, plate and subduction velocities, and the geometry of the slab. The geometry of the slab is only marginally affected by the velocity and direction of the mantle flow. In the absence of mantle flow, slab rolls back and deformation is accommodated by trench-orthogonal stretching in the upper plate. Instead, the addition of a background flow dragging the lower or upper plate toward the trench systematically results either in the absence of upper plate deformation, or in trench-orthogonal shortening with strain rates that increase linearly with increasing mantle flow. We show that the upper plate strain rate is primarily controlled by the velocity of the free plate in the model, which itself results from the drag exerted by the mantle at the base of the plate. Coupling between mantle and plate is larger for models with flow directed toward the upper plate, resulting in strain rates that are about three times larger than for equivalent models with flow directed toward the lower plate. This systematic study provides a better understanding of the effect of mantle drag on plate displacements and deformation along subduction zones, leading to a better understanding of the ingredients required to form Andean-type mountain ranges.

International audience; In the midst of climate change, academic travels - one salient aspect of the carbon footprint of research activities - are at the center of a growing concern. Mitigation options often focus on two dimensions : (i) decreasing the frequency of attendance to conferences and (ii) modal shift in transport. Here, we analyze professional travel in academia from a unique database compiling about 100 000 travels from about 150 research labs across a large array of disciplines and localities in France to detail the structure, patterns and heterogeneity of national and international research travels for research purposes. We estimate the mitigation potential of a series of options encompassing but not limited to institutional options. We show that, if short distance traveling (typically below 1000 km) are largely dominant in number, their relative mitigation potential via modal shift is small (i.e., below 15%). On the other hand, long distance traveling, which is often associated with international collaborations or field work hold a much larger mitigation potential but question the very nature of research activities. We propose ambitious sobriety options to robustly decrease travel-induced GHG emissions in academia and discuss their acceptability in the context of the French public research system.