Caractérisation et chronologie des systèmes de dunes barkhanoïdes de la flèche du Cap Ferret (Aquitaine) : modèle d’évolution et datations OSL
La flèche du Cap Ferret est un système côtier recouvert par un vaste champ dunaire barkhanoïdes, fixé au cours du XIXeS. L’analyse du MNT LiDAR et de l’architecture interne par géoradar révèlent un gradient morphologique ouest-est structuré en 4 morphotypes (Fig.1) : dunes embryonnaires à morphologie chaotique, proto-barkhanes à forme longitudinale, rides barkhanoïdes et barkhanes. Les profils géoradar illustrent les phases successives de migration vers l’est et ont permis de définir un modèle d’évolution du champ dunaire (initiation, grossissement par chevauchement, changement morphologique et individualisation des barkhanes). Ce travail vise à déterminer si ces morphotypes se sont mis en place simultanément ou non. Six datations par OSL ont été réalisées sur un transect ouest-est (Fig.1) à partir de sédiments prélevés en zones interdunaires et pieds de dune. Les âges obtenus sont compris entre 0.29ka et 0.49ka (incertitude moyenne : 0.05ka), confirmant une mise en place, ou du moins une mobilité, du champ dunaire au cours des cinq derniers siècles. On distingue 3 groupements d’âges : 1) les plus profonds correspondent aux plus anciens , sont datés en zone interdunaire (CAPF2-1/2-4/2-5 : 0.45–0.49ka), l’hypothèse est qu’ils dateraient des phases précédentes de migration dunaire; 2) de part et d’autre la ride barkhanoïde centrale, les âges sont proches (CAPF2-2/2-3 : ~0.38ka) et indiquerait une remobilisation et un dépôt du sable dunaire lors de sa dernière phase de migration ; 3) les âges au niveau des pieds de dune de la face d’avalanche, sont les plus récents et concordants entre eux (CAPF2.-3/2-6 : 0.29/0.38ka), ce qui indiquerait que les dunes ont été mobiles sur les mêmes périodes. De plus, le fait de ne pas avoir de dates plus jeunes coïncide avec une stabilisation puis un arrêt de la migration dunaire (fixation dunaire par l’homme). Ce schéma chronologique est cohérent avec le modèle d’évolution proposé. Ces résultats fournissent une 1ère contrainte temporelle sur la mise en place et la mobilité du champ dunaire barkhanoïde du Cap Ferret et sont cohérents avec le modèle d’évolution proposé ainsi qu’avec les études menées localement dans la région (Soulac et Biscarosse). Figure 1: (A) Carte de position des points de datation OSL (CAPF2) sur fond LiDAR ; (B) modèle d’évolution des barkhanoïdes (Billières-Kim et al., in review) ; (C) Coupe topographique du transect échantillonné pour datation
(Bulletin de l'Association des sédimentologistes Français, 11/10/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRAMAT, UTBM, UO, UBM, CNRS, IRAMAT-CRP2A, IRAMAT, UTBM, UO, UBM, CNRS
Organic carbon composition and preservation in macrotidal coastal wetland sediment: insights from biomarkers and isotopic signatures
Coastal wetlands store high amounts of organic carbon (OC) in their sediments, but long-term preservation of this carbon depends on habitat type, sediment depth, and the molecular characteristics of organic matter (OM). This study explores the dynamics of OC deposition and preservation across vertical profiles (0–30 cm) in two adjacent coastal habitats—mudflat, and salt-marsh—within the macrotidal system of the Aiguillon Bay (France). A multi-tracer approach was applied, combining stable isotopes δ13C, C/N ratios, lignin phenols, and fatty acids. Sediment OC content ranged from 13.4 to 23.2 mgC g−1, with the highest concentrations found in the salt-marsh. δ13C and C/N signatures revealed dominant marine source in the mudflat, with a secondary contribution from microphytobenthos, and mixed marine–C₃ plant inputs in the salt-marsh. Fatty acids and lignin compositions supported this partitioning, with surface mudflat layers enriched in labile microbial and algal-derived compounds, whereas deeper salt-marsh sediments retained more resistant, C3 plant-derived signatures resembling those of terrestrial OM source. OM degradation rates were closely linked to source composition and depth. Degradation was concentrated within the top 5 cm of salt-marsh and the top 10 cm of mudflat. Below these depths, biomarker profiles changed minimally, delineating a transition to longer-term preservation. First-order degradation constants were three times higher in mudflat (0.53 yr−1) than in salt-marsh (0.17 yr−1), despite similarly high sedimentation rates (1.8 and 2.2 cm yr−1, respectively). This reflects differences in OM lability, with even minor contributions from microphytobenthos enhancing reactivity in mudflats. Salt-marshes, with their intermediate OM reactivity and high sedimentation rates, emerged as hotspots of carbon accumulation (366 gC m−2 yr −1), while mudflats also contributed substantially to coastal carbon sequestration (239 gC m−2 yr −1). These results highlight the value of depth-resolved, biomarker-based approaches to identify habitat-specific degradation dynamics; ultimately better understanding carbon accumulation in coastal ecosystems.
(Science of the Total Environment. vol. 1020, n° 0048-9697, pp. 181542, 11/10/2026)
LIENSs, INSU - CNRS, ULR, CNRS, iEES Paris, IRD, SU, UPEC UP12, CNRS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPG-ANGERS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST
The impact of suspended sediments on exchange flow in a macrotidal, hyperturbid estuary
This study investigates the sensitivity of the total exchange flow (TEF) with regard to suspended sediment concentrations (SSC) in water density calculations. We consider two scenarios of an idealized model based on a macrotidal, highly turbid estuary: one where density depends on both salinity and SSC and another where density depends only on salinity. These models are used to understand how TEF volume inflow ( Q in ) varies along the estuary over fortnightly and monthly time scales. The bulk values of TEF inflow between the two model scenarios show small differences (less than 4 %) over 5 months. However, differences in TEF bulk volume inflow reach 7 % downstream of the estuarine turbidity maximum (ETM), 22 % at the ETM, and nearly 70 % upstream of the ETM when quantified only over spring tides. The gradient Richardson number indicates that sediment-induced stratification suppresses shear production ∼ 30 km further upstream when suspended sediments are an active tracer. The most profound impact on TEF occurs during spring tides at, and upstream of, the ETM where sediment contributions to density exceed those from salinity. The sediment contribution leads to increased stratification in the upper reaches of the estuary, effectively reducing the longitudinal density gradient and therefore the exchange flow as much as 2000 m 3 s −1 , indicating a dominant role of suspended sediments in attenuating exchange in hyperturbid estuaries. The results from this work highlight the importance of SSC on density calculations in estuarine studies of the exchange flow.
(Ocean Science. vol. 22, n° 1812-0784, pp. 1311-1327, 11/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, RHITME, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS
Late Holocene glacier fluctuations in the Northern Greater Caucasus (Russia) inferred from 10 Be cosmic ray exposure moraine dating
Our understanding of mountain glacier changes located in the Greater Caucasus during the Holocene is only loosely constrained. So far moraines were tentatively dated from sporadic cosmic ray exposure (CRE) ages, tree rings and radiocarbon ages. Here, we present 78 10 Be CRE ages that were obtained from samples collected on moraine boulders and roches moutonnees from one debris-free Terskol glacier and two debris-covered Bashkara and Donguz-Orun glaciers, all located in the Elbrus area. 10 Be CRE ages span from the beginning of the Late Holocene to the Little Ice Age. We did not found evidence of moraine formed neither during the Early Holocene nor during the Mid-Holocene suggesting that during both periods glaciers had a smaller size than during the Late Holocene, when several moraines were deposited at the base of the three glaciers. The oldest moraine that documents the largest Holocene glacier advance occurred around 3.4 ka at the base of the debris-covered Bashkara and Donguz-Orun glaciers, respectively. The debris-free Terskol glacier experienced its largest Holocene extent a bit later in the Late Holocene with moraines dated to ~2.7 ka. Subsequently several glacier advances of smaller extent were recorded almost synchronously between the three glaciers around ~2.2 ka, 1.5 ka, and during the Little Ice Age. Regional climate conditions estimated from TraCE simulations and rare proxy records suggest that the Early and Mid-Holocene were dry and warm with progressive wetter and cooler conditions during the Late Holocene concomitant with glacier evolution observed in the three valleys.
(The Holocene, n° 0959-6836, 26/12/2025)
CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, RAS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS, LGP, UP1, UPEC UP12, CNRS
Investigating the potential of time‐varying free parameters in equilibrium shoreline change models through data assimilation
Equilibrium shoreline change models with calibrated, time‐invariant free parameters have demonstrated good skill in hindcasting shoreline evolution at sites dominated by cross‐shore sediment transport. However, their performance can be biased by the specific conditions present during the calibration period. In this study, a dual parameter‐state ensemble Kalman filter (EnKF) was applied to track non‐stationarity in model free parameters at three sites along the west coast of Europe. Introducing time‐varying parameters did not substantially improve performance relative to an already well‐calibrated stationary model. Model skill improvement occurred mainly during the EnKF correction step, highlighting the potential of real‐time data assimilation for maintaining model stability. Although variations in model parameters may compensate for unresolved processes and should be interpreted cautiously, incorporating climate‐driven, time‐varying parameters could improve extreme‐event predictions at seasonally dominated sites and enhance overall model performance in regions influenced by complex, multimodal wave climates.
(Earth Surface Processes and Landforms. vol. 50, n° 0197-9337, 21/12/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, UNSW, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS
Times of changes, the latest Pleistocene micromammal association of the Salto de Piedra site (Buenos Aires Province, Argentina)
The results of the taxonomic, taphonomic, and paleoecological analyses of Late Pleistocene micromammals from the Salto de Piedra paleontological locality are presented in this paper. Our results support the conclusion that the microfaunal remains were mainly accumulated by diurnal raptors in areas close to where the remains were deposited, as there is no evidence of transport. Taxonomically, the recovered micromammals include rodents currently inhabiting the Humid Pampa (Calomys cf. C. musculinus-laucha, Ctenomys sp., and Reithrodon auritus) and species that became extinct during the Late Pleistocene (Microcavia cf. M. robusta) and Holocene (Galea tixiensis). Additionally, remains of the Patagonian marsupial Lestodelphys halli and the amphibious sigmodontine Holochilus brasiliensis were identified. These analyses, along with the paleoecological and malacological studies at Salto de Piedra, confirm a trend toward increased humidity, consistent with the paleoenvironmental evidence documented for the region at the end of the Pleistocene. This study of the central Humid Pampa based on this small mammal record is of particular interest for interpreting the paleoenvironmental and paleoecological scenario, coinciding with the arrival of the first humans in the area and the extinction of the megafauna.
(Quaternary Research. vol. 131, n° 0033-5894, pp. 116 - 133, 18/12/2025)
UV, UC3M, MNCN, CSIC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Synthetic cannabinoids in Mayotte over a year in time and space: an example of high-frequency evolution of market
As illicit drug trafficking becomes more widespread, it is increasingly important to assess the extent of drug abuse for health and safety reasons. However, on the one hand, administering questionnaires to consumers is time-consuming and inconclusive, and on the other hand, seizures and clinical data evaluate service performance in response to the flow of illicit drugs rather than the flow itself. Wastewater-based epidemiology has ushered in a new era, but it tends to provide snapshots and encourages the bias of assuming that recalculated consumption is stable between samples. In Mayotte, synthetic cannabinoid receptor agonists (SCRAs), the main constituents of “chimique,” have achieved an unusual status as an iconic hard drug in a disorganized political context. Assuming a “worst-case scenario,” i.e., insularity and the specificity of SCRAs drug abuse in Mayotte, this approach aimed to explore the evolution of the nature and concentration of SCRAs, as well as their location. Over the course of a year, eight “chimique” sampling campaigns were conducted in Mayotte, collecting samples from street users and in places of open consumption for 1 week each. Consumers were offered (i) an interview (standard of living, sources of supply, consumption, co-addictions, side effects on health, and social life) and (ii) the opportunity to provide a sample of their “chimique” dose for analysis and to be informed of its composition. The collected “chimique” samples were analyzed using a liquid chromatography method with high-resolution mass spectrometry detection method and (i) “in-house” and (ii) online (HighResNPS) spectral libraries. Illegal drugs were identified during each campaign, for a total of 195 samples (187 cigarettes and 8 powders). Thirteen different SCRAs were observed in association with a plant matrix (tobacco was predominant, mixed or unmixed with cannabis). Co-formulants included cannabinoids, pharmaceuticals/precursors, and/or other new psychoactive substances. The results showed that month after month, the market became more homogeneous due to the products offered by SCRA pharmaceutical manufacturers and the growing hegemony of a gang of traffickers. However, the profile of the samples collected changed rapidly, sometimes becoming unrecognizable from one campaign to the next.
(Environmental Science and Pollution Research. vol. 32, n° 0944-1344, pp. 30517-30539, 12/12/2025)
CUFR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CHRU Lille, IMPECS, CHRU Lille, ESE, CNRS
ADB-BUTINACA, a synthetic cannabinoid receptor agonist: overview of its presence in the “Chimique” in Mayotte
The emergence of new psychoactive substances (NPS) has made illicit drugs a major health issue. The largest family of NPS is that of synthetic cannabinoid receptor agonists (SCRAs). Due to their widespread use, security authorities are working to strengthen their protocols for detecting, managing, and preventing abuse. Wastewater-based epidemiology, which focuses on drug metabolites, complements seizures and questionnaires in this regard. In this context, we present data on ADB-BUTINACA, a SCRA detected during the "Chasse-marée" study conducted in Mayotte, a French overseas territory located in the Mozambique Channel. The aim of this article is to identify and select ADB-BUTINACA metabolites relevant as target residues of this SCRA to estimate population exposure from wastewater. Using LC-HRMS, this SCRA (along with other SCRAs) was detected in "Chimique" samples (the term used for illicit substances in circulation in Mayotte) on 24 occasions during seven of the eight sampling campaigns conducted as part of the study (2022-2023). We then conducted a study on its metabolism using in vitro human liver microsome incubation experiments and LC-HRMS analysis and discussed its most relevant biomarker. Among the 26 metabolites identified, two resulting from the mono-hydroxylation of the n-butyl tail of ADB-BUTINACA (C18H26N4O3, HRMS target [M+H]+ m/z 347.2078) are considered the most promising biomarkers. This assessment is based on the relatively high intensity of the chromatographic peak observed in vitro (41.7% and 34.2%, respectively) and on the assumption that this type of product is persistent in wastewater. Their practical analytical relevance in subsequent studies still needs to be validated by assessing their toxicological significance and stability in wastewater. These two metabolites constitute an initial proposal for targets for monitoring ADB-BUTINACA in wastewater, subject to verification of their persistence, in order to improve knowledge of these compounds.
(Environmental Science and Pollution Research. vol. 32, n° 0944-1344, pp. 29905-29916, 11/12/2025)
CHRU Lille, IMPECS, CHRU Lille, CRPV Bordeaux, CHU Bordeaux, POPAM 976, Association Oppelia, IRD, UPVD, AU, UR, UNC, UG, UA, UM, UMay, Migrinter [Poitiers], UP, CNRS, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modeling past and future evolution of sandy coasts
Sandy coasts are dynamic environments that continuously respond to the combined influence of waves, tides, and sea-level rise. With the acceleration of this rise and the persistence of sediment deficits, these systems are becoming increasingly vulnerable, particularly where human occupation constrains their natural adjustment. Despite recent advances in coastal morphodynamic modeling, long-term shoreline prediction remains challenging. Most models represent only a simplified coupling between longshore sediment transport and the cross-shore profile response, still considering these components as weakly interactive, without explicit feedback between the planform shoreline evolution and the volumetric translations of the profile under sea-level rise. This thesis addresses this limitation through the development and application of LX-ST, a reduced-complexity coupling framework that integrates the planform dynamics of the LX-Shore model with the profile translation simulated by the ShoreTrans model. LX-ST includes several levels of coupling and, through ShoreTrans, can represent different modes of profile translation, notably distinguishing between adaptive dune responses and constrained responses to sea-level rise. Its capabilities were tested on both synthetic and real cases (Lacanau, Aquitaine coast, France), showing that LX-ST reproduces key coastal behaviors, including longitudinal variability, induced feedbacks, and nonlinear responses to sea-level rise. Projections to the year 2100, based on various Shared Socioeconomic Pathway scenarios, combine two major sources of uncertainty: sea-level rise and long-term sediment deficit. Probabilistic shoreline projections were obtained using LX-Shore, while LX-ST refined the representation of dune evolution and morphological changes near the seawall. Sensitivity analysis showed that sediment deficit dominates uncertainty during the first decades, whereas sea-level rise becomes the main source of uncertainty in the second half of the century, depending on the scenario considered. An important result is the identification of trajectory changes, i.e., transitions in the spatial pattern of shoreline evolution, resulting from feedbacks between longshore transport and nearshore evolution. The results also highlight the sensitivity of projections to the mode of profile response (adaptive or erosive), with major implications for the persistence or disappearance of dune systems. This work contributes to improving the understanding and prediction of the long-term evolution of wave-dominated sandy coasts under future sea-level rise.
(11/12/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Satellite-derived shoreline data assimilation for sandy coast evolution
Understanding and predicting the evolution of sandy shorelines remains a central challenge in coastal science and a critical requirement for sustainable management. Reliable predictions require consistent observations and models capable of representing complex, non-stationary morphodynamic behaviour. This thesis advances shoreline change modelling by integrating publicly available datasets—primarily satellite-derived shoreline (SDS) observations—within calibration and data assimilation frameworks, assessing their added value. By relying exclusively on freely accessible data, the work establishes a transparent, transferable modelling foundation applicable even in data-limited coastal environments. The initial focus is on 1D equilibrium shoreline models, addressing calibration using uncorrected, noisy SDS data without tidal adjustments or a priori site knowledge. Using a simulated annealing algorithm, robust model calibrations were achieved at Truc Vert beach, a fully exposed, wave-dominated site with high-energy waves, large tides, complex intertidal bathymetry, and mild nearshore slopes that introduce substantial observational uncertainty. The strong model performance under these challenging and conservative conditions demonstrates that valuable information can be extracted from low-quality SDS, supporting broader applicability where simple equilibrium models are suitable. Applying uncorrected SDS in sequential data assimilation proved more challenging due to observation noise limiting the algorithm’s ability to track system non-stationarity. To explore the potential of time-varying model free parameters, in situ observations were used to assess links to wave climate and influence on predictive skill. Across multiple sites along the European Atlantic coast, the connection between parameter variability and climate was weak or absent, suggesting non-stationarity primarily reflects local morphodynamic adjustments. Non-stationary models showed slightly improved performance at some sites and reduced skill at others, with data quality influencing outcomes—sites with higher-quality observations benefited more. Notably, nonstationary models captured extremes of erosion, demonstrating their potential for representing rare but significant events, though stronger gains would require regions with multimodal wave climates. Building on these insights, calibration and data assimilation were combined in an international benchmark experiment at a site in Australia documented with SDS data and historical aerial photographs. Two distinct equilibrium-based models were explicitly coupled within a hybrid framework, illustrating how calibration and assimilation can complement each other. This approach highlights the potential of ad hoc hybrid modelling strategies that merge separate empirical formulations to capture multi-scale shoreline dynamics within reduced-complexity frameworks. Finally, the framework was extended to a quasi-2D configuration using grid-based data assimilation with spatial nudging. Applied to the highly dynamic Sacalin spit in the southern Danube delta, where dominant processes are not explicitly represented in the model, the approach successfully constrained shoreline evolution across the grid and improved agreement with long-term satellite observations. Although neighbouring grid dependencies were not yet considered, this implementation represents a critical step toward fully 2D assimilation capable of resolving spatial feedbacks in shoreline evolution. Overall, this work demonstrates that combining long-term satellite observations with hybrid modelling and data assimilation provides a powerful pathway for advancing understanding, prediction, and eventually operational forecasting of shoreline change in complex coastal systems.
(08/12/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS