Diapiric ridges and minibasins in the Central High Atlas: impact on geometries and facies distribution (Lower-Middle Jurassic, Morocco)
The Central High Atlas of Morocco is the result of the Alpine tectonic inversion of an intracontinental Mesozoic basin, the infill of which started with thick Upper Triassic clay and evaporite deposition. This slightly deformed mountain range is characterized by narrow ENE-WSW ridges that expose a Triassic core. These ridges bound unique synclines filled by thick Jurassic successions showing well-preserved halokinetic depositional sequences, interpreted as salt-related minibasins. This paper aims to describe and analyze the evolution of diapiric movements and their interactions with Lower and Middle Jurassic carbonate dominated sedimentation in the Imilchil area, which corresponds to the axial part of the Atlas basin. Four diapiric ridges have been identified in this region: the Tasraft, Tassent, Ikkou, and Amagmag, which expose Triassic shales and are intruded by Triassic and Jurassic magmatic rocks. These ridges delineate three minibasins: Ikassene, Lakes (Lake Plateau), and Tilmi (Ikkou), each 5 to 10 km wide, preserving over 6,000 m of Upper Liassic and Dogger deposits. The Atlas basin is filled with five third-order transgression-regression cycles organized as one regressive megasequence. This long regressive trend is expressed by the succession of three depositional systems: i) a distal to proximal carbonate ramp system from the Toarcian to Late Bajocian; ii) a shallow mixed carbonate-siliciclastic system from the Late Bajocian to Early Bathonian; and iii) a fluvial system from the Bathonian to Early Callovian. Throughout this period, the development of coeval diapiric ridges significantly influenced these sedimentary systems, though the intensity of the diapiric activity varied over time. During the Late Bajocian, ridge growth slowed considerably amid the peak progradation of the carbonate systems. It then increased significantly from the latest Bajocian onward, due to a drastic rise in siliciclastic flux and sedimentation rate in the Atlas basin. The effects of diapirism on sedimentation are observed regionally (several kilometers), as minibasins evolve as depocenters, each exhibiting distinct subsidence rates and sedimentary thicknesses. Despite these local variations, the regional scale paleogeography and the sequential organization of the deposits remained largely unaffected. On a smaller scale (hectometers to kilometers), diapiric structures are always characterized by halokinetic depositional patterns. Internal angular unconformities only occur in very shallow-marine to continental deposits during periods of maximum ridge growth and subaerial exposure (notably in the Bathonian). At this scale, diapiric movements lead to local facies variations within shallowmarine deposits, fostering the development of bioconstructed or grainy carbonate sediment bodies along the ridges. However, in outer ramp environments, the submarine topographies created by ridge growth were generally insufficient to induce similar facies variations.
(Bulletin de la Société Géologique de France, n° 0037-9409, 21/01/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, UAB, GEO3BCN–CSIC, CSIC
A critical role of heterotrophic bacteria in early diagenesis of carbonates through exopolymer degradation and calcium release.
The degradation of exopolymeric substances (EPS) by heterotrophic bacteria, concomitant release of calcium ions and precipitation of carbonates were studied in a temperate mountain lake, Lac d'Ilay, Jura France. Phytoplankton blooms in this lake produced large amounts of exopolymeric substances (EPS; 1.8–3.0 mg L −1 ), probably inhibiting CaCO 3 precipitation by binding Ca 2+ as shown by the saturation index of calcite and aragonite remaining well below 1. EPS settled to the sediments, where additional polymeric substances were produced by the benthic community. The total amount of EPS decreased downcore from ca 50 μg/g dry sediment near the surface to ca 1.5 μg/g dry sediment at the bottom (120 cm depth). A decrease in acidity, protein and sugar content, and calcium‐binding capacity of EPS with depth coincided with active calcite precipitation. Aerobic and anaerobic EPS‐degrading heterotrophic enrichments were obtained from the top, middle and bottom of the core. Doubling times of aerobic cultures from the top were six times shorter than those of cultures obtained from the bottom of the core, but anaerobic growth rates were similar across all enrichments. Aerobic turnover rates of organic compounds decreased by a factor of 4–5 from top to bottom; anaerobic rates were similar at all depths, except for the turnover of polymers, which was negligible at the surface compared to rates at the middle and bottom. All enrichments released calcium when grown on EPS. Growth on calcium‐saturated EPS in anaerobic cultures obtained from the bottom of the core was the slowest, but still released 26% of the Ca in 20 days. This release during EPS degradation explained an increase in free calcium ions with depth reported in a previous study and may account for a large fraction of the carbonate mud. This suggests that sediments should be considered as an important source of biogenic carbonates.
(Depositional Record. vol. 12, n° 2055-4877, pp. e70057, 16/01/2026)
UCONN, BGS, EPHE, PSL, CNRS, UBE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Unibas, UNSW, UNC, UNC
Salinity Transition in the Ostia Lagoon During the Roman Period: Assessing the Feasibility of Salt Exploitation
This study examines long‐term salinity changes in the Ostia Lagoon between the 4th century cal BC and the 6th century cal AD , with emphasis on their implications for ancient salt production. Although Ostia's foundation is closely linked to the control of salt resources in the Tiber Delta, direct archaeological evidence of Roman‐period saltworks is scarce. To address this gap, this study combines micropalaeontological analysis of ostracod assemblages with a morphometric study of sieve pore features in Cyprideis torosa (Jones, 1850). This approach enables reconstruction of short‐term palaeosalinity dynamics. Core LOA–1 documents a transition from peatland to euryhaline lagoon between the 8th–6th and the 4th–3rd centuries cal BC , followed by repeated high‐salinity episodes. A notable peak coincides with the establishment of the Roman Castrum, suggesting favourable conditions for salt concentration. After the mid‐4th century cal BC , salinity peaks decreased, possibly reducing the lagoon's potential for saltworks and fostering greater reliance on the Maccarese saltworks. In the northern lagoon sector, hyperhaline conditions during the Roman period remain uncertain because of chronological gaps and the lack of sieve pore analysis. Overall, the results demonstrate both the potential and limitations of ostracod analysis as a palaeosalinity proxy and refine understanding of salt exploitation in the Tiber Delta. This study provides valuable insights into the long‐term socio‐environmental dynamics of the Mediterranean coastal wetlands, contributing to the advancement of geoarchaeological research on ancient salt production through salterns and its influence on human settlement patterns and economic practices.
(Geoarchaeology: An International Journal. vol. 41, n° 0883-6353, 10/01/2026)
Archéorient, UL2, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IGAG, CNR, CNRS, LIVE, UNISTRA, CNRS, ISCR
Tackling global change: integrated approaches for people and environment
(09/01/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE, ECLA, USMB [Université de Savoie] [Université de Chambéry], INRAE, OFB, UB, CNRS, INRAE
Oceanic and climatic dynamics during the MIS 12–11 transition in the Gulf of Cádiz: Insights from coccolithophores
This study reconstructs environmental variability and surface-ocean dynamics across Termination V (MIS 12-11) in the Gulf of Cádiz using coccolithophore assemblages from International Ocean Discovery Program (IODP) Site U1386. Our data, combined with independent palaeoenvironmental proxies, including sea surface temperatures (SST), ice-rafted debris (IRD), benthic δ 18 O, and Mediterranean forest pollen assemblages, reveal a marked increase in coccolithophore productivity during MIS 11 compared to MIS 12. The end of the glacial period is characterised by higher abundances of Gephyrocapsa oceanica and reworked calcareous nannofossils, suggesting intensified Mediterranean Outflow Water (MOW). High abundances of the cold-water species Coccolithus pelagicus subsp. pelagicus, together with low SSTs and reduced Mediterranean forest pollen, reflect cold and dry conditions that were unfavourable for coccolithophore proliferation. These patterns suggest a weak westerly influence over southwestern Iberia, resulting in reduced precipitation and limited upwelling during the end of the MIS 12. In contrast, MIS 11 suggests stronger westerly influence, promoting wetter conditions and higher productivity. A sharp decline in productivity around 430 ka corresponds to a cooling event associated with increased IRD deposition, likely related to Heinrich-type event 4. These findings provide new insights into the coupling between atmospheric circulation, ocean dynamics, and primary productivity during the Mid-Brunhes Event.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 681, n° 0031-0182, 01/01/2026)
CIDIS, UPCH, UC Santa Cruz, UC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The role of biomolecules produced by invasive macrophytes in lake ecosystem processes
Egeria densa and Lagarosiphon major are the main invasive hydrophytes in French Atlantic Lakes. These exotic species can modify trophic levels by producing large quantities of biomass in lakes; previous investigations revealed the occurrence of endogenous metabolites in these plants known to be able to affect epiphytic communities, phytoplankton, or other plants, through allelopathic activity. Nevertheless, the actual excretion and environmental occurrence of these metabolites remain poorly documented. In order to gain knowledge of the concrete occurrence and potential ecological impact of E. densa and L. major exometabolome, untargeted metabolomics using high-resolution mass spectrometer and chemometrics approaches is relevant through its ability to depict, as a first step, the exometabolome chemical landscape.
(01/01/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
In situ monitoring of LNAPL-contaminated aquifer remediation using ultraviolet light-induced fluorescence imaging
Groundwater contamination by light non-aqueous phase liquids (LNAPLs) represents a major environmental challenge, requiring efficient and adaptive remediation methods. This study proposes and validates an innovative implementation of an in situ monitoring technique for LNAPL remediation treatments, based on ultraviolet lightinduced fluorescence imaging (UVIF), combined with automated image post-treatment, to enable in situ and realtime monitoring of decontamination processes. Specifically, a mini-camera integrated into a set of transparent wells embedded in the subsurface of LNAPL-contaminated zones was used to monitor both a surfactant injection remediation process and a skimming operation involving groundwater drawdown. The technique was first calibrated and validated through laboratory and pilot-scale experiments, then tested on a real site, which was contaminated with diesel. The pilot test revealed differences of less than 5 % between recovery factors obtained via gas chromatography (GC) of soil samples and those measured with the proposed imaging technique. Sitespecific calibration correlated fluorescence intensity from endoscopic images in transparent tubes with GCanalyzed LNAPL content, showing a strong correlation (R² = 0.993) and relative errors below 10 %. This enabled accurate in situ estimation of LNAPL variations: content remained mostly unchanged without treatment (<5 % variation), decreased moderately during pumping and skimming (≈35 %), and dropped substantially during surfactant injection (≈60 %).This capability supports immediate treatment adjustments, thereby optimizing pollutant recovery rates. Beyond simple monitoring, the results demonstrate that UVIF can effectively guide remediation operations by providing rapid feedback (near real-time) on contaminant removal dynamics.
(Journal of Hazardous Materials. vol. 501, n° 0304-3894, 01/01/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, I2M-BX, UB, CNRS, INRAE
Northernmost record in the Bay of Biscay (northeastern Atlantic) of two leptothecate hydroids (Cnidaria: Hydrozoa) of southern affinity
Two leptothecate hydroids of southern affinity, Sertularella ornata Broch, 1933 and Sertularelloides cylindritheca (Allman, 1888) were collected in the southern sector of the Bay of Biscay off Saint Jean de Luz (France). The latter was also seen during several ROV surveys on rocky communities along the Cantabrian Sea and northwestern Spain. Each of the two species is herein described and illustrated and their worldwide distribution, bathymetric ranges and reproductive periods, revised; additionally, we allocate them in their biocoenological context, providing in situ images. The northern boundary limits are extended for both hydroids, which are new records for the Atlantic coast of France; the latter belongs to a genus previously unrecorded in the French mainland fauna. We also discuss the importance of having inventories of the sessile fauna of the exceptional sites at study, for the sake of their protection and detection of future modifications due to climate change.
(Journal of Marine Systems. vol. 253, n° 0924-7963, pp. 104158 (11p.), 01/01/2026)
INSUB, LERAR, COAST, IFREMER, IEO | CSIC, CSIC, LERPAC, COAST, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
First and disturbing records of the bivalve molluscs Potamocorbula amurensis (Schrenck, 1861) and Mulinia lateralis (Say, 1822) in the Bay of Biscay (France)
The bivalve mollusc Potamocorbula amurensis, a Corbulidae from the Asian coasts, was recorded for the first time in France in September 2023 in the Gironde estuary, and subsequently in September 2024 in Aiguillon Cove and Aytré Bay. In Aytré Bay, it was accompanied by another non-native bivalve not previously reported from French coasts, Mulinia lateralis, a Mactridae from the western Atlantic coasts. These two species were first recorded in Europe in 2018 in the Westerschelde (Netherlands, Belgium) and are known to be potentially highly invasive. Particular attention should be paid to monitor the spread and the establishment of these two euryoecious species along European coasts.
(An Aod - Les cahiers naturalistes de l’Observatoire marin, n° 2263-5718, 03/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, OBIONE, LIENSs, INSU - CNRS, ULR, CNRS, LPO, PatriNat, MNHN, IRD, CNRS, OFB - DSUED, OFB, PatriNat, MNHN, CNRS, OFB, PatriNat, MNHN, CNRS, AFB
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, 03/09/2026)
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