Écoulements Turbiditiques Volcanoclastiques Récents du Bassin de Somalie : Sources et Origines
L'Archipel des Comores se situe au Sud du Bassin de Somalie et est constitué de 4 iles volcaniques. Au large de celui-ci, des dépôts volcanoclastiques ont été découverts à partir d'enregistrements sédimentaires carottes (campagnes océanographiques : MOZAPHARE, 1996 ; SISMAORE, 2020-21 ; SCRATCH, 2021). Ce sont des turbidites à matériel volcanoclastique retrouvées sur plusieurs dizaines à centaines de kilomètres. Cette étude s'insérant dans le cadre des ANRs COYOTE (ANR-19-CE31-0018) et ITCH (ANR-22-EDIR-0003), vise à caractériser les genèses et mécanismes de mise en place des évènements turbiditiques depuis 1200 ka du bassin de Somalie. Pour retracer les sources, des analyses géochimiques ont été faites sur des verres juvéniles basaltiques à basanitiques issus des niveaux volcanoclastiques. Ces derniers ont été étudiés à partir d'une approche morphogranulométrique ayant pour but de (i) classer les grains entre les éléments lithiques masqués et les verres frais et de (ii) décrire des morphologies caractéristiques de certains dynamismes éruptifs. Parmi les douze évènements principaux étudiés, la plupart présente une source potentielle du volcan principal de l'ile de Grande Comore, le Karthala. Les morphologies des particules volcaniques semblent mettre en jeu du volcanisme phréatomagmatique, sous-marin peu profond à surtseyen. Les valeurs de teneurs en eau des verres frais viendraient corroborer cette hypothèse. Une période éruptive principale entre 1200 et 800 ka est documentée dans toutes les carottes étudiées (espacées de 50 à 400 km d'une source comorienne). Pour expliquer une activité volcanique surtseyenne répétitive visible sur plusieurs niveaux espaces de dizaines de milliers d'années, une cyclicité des phases éruptives entrecoupées d'effondrements successifs de l'édifice volcanique, peinant à dépasser durablement la surface et nécessaire à son émersion, sont proposés. Les volumes déplacés avec les turbidites volcanoclastiques font de ces éruptions menant à l'émersion du Karthala des évènements régionaux majeurs.
(30/10/2023)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMV, IRD, INSU - CNRS, CNRS, UCA, LMV-ENSMSE, Mines Saint-Étienne MSE, IMT, CNRS, LMV, IRD, INSU - CNRS, CNRS, UCA, LGSR, UR, IPG Paris
Volcanisme et tectonique le long de l'archipel des Comores (Canal Nord Mozambique) : état d'avancement du projet ANR COYOTES
Suite à l’initiation en mai 2018 de la crise sismo-volcanique de Mayotte qui a donné lieu, entre autre, à une intense sismicité et à la mise en place d’un nouvel édifice volcanique sous-marin, Fani-Maoré, à 50km à l’Est de Mayotte, la communauté scientifique s’est fortement impliquée. Un effort conséquent a été réalisé pour améliorer les connaissances géologiques de ce territoire grâce à des projets de recherches, en parallèle de la surveillance de l’activité tellurique menée par le REVOSIMA (campagnes MAYOBS, DOI :10.18142/291).Le projet COYOTES (Comoros & maYotte: vOlcanism, TEctonics and Seismicity, 2020-2024), s’appuyant sur des données des campagnes océanographiques de recherche SISMAORE (10.17600/18001331) et SCRATCH (DOI :10.17600/18002274), vise à mieux comprendre le contexte géologique et géodynamique du Canal nord Mozambique. Cela intègre à la fois l'évolution et la répartition de l’activité volcanique, tectonique et sismologique ainsi que la cinématique et la caractérisation des dépôts sédimentaires et des structures crustales, à court et à long terme et aux échelles locale et régionale. Nous proposons de présenter l’état d’avancement des travaux menés dans le cadre de cet ANR-COYOTES, spécifiquement sur la distribution spatiale des déformations actives et récentes le long de l'archipel des Comores (Thinon et al., 2022 ; Boymond et al., 2022 ; Mercury et al., 2022), sur les nouveaux âges et la géochimie des édifices volcaniques et des iles (Rusquet et al., 2023), sur la caractérisation des dépôts volcano-détritiques et des déstabilisations identifiées dans la plaine abyssale (Paquet et al., 2019). L’architecture du substratum sous le volcan Fani-Maoré et la structuration crustale seront également exposées (Canva et al., RST 2023; Masquelet et al., 2022; Rolandone et al., 2022 ; Watremez et al., RST 2023). Ce résumé est une contribution des équipes du projet COYOTES (ANR-19-CE31-0018), financé par l’ANR et le BRGM (http://www.geocean.net/coyotes/doku.php?id=start).
(30/10/2023)
BRGM, iSTeP, INSU - CNRS, SU, CNRS, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, LGSR, UR, IPG Paris, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGENS, INSU - CNRS, CNRS, ENS-PSL, PSL, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], EOST, UNISTRA, INSU - CNRS, CNRS, OVSG, IPG Paris, LMV, IRD, INSU - CNRS, CNRS, UCA, IPGS, UNISTRA, INSU - CNRS, CNRS, UNISTRA, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Tectono-sedimentary evolution of the late-Carboniferous intramountain basins of the Maures-Tanneron Massif: a key to precise the late-orogenic structural setting of the southeastern European Variscan Belt?
Understanding the geodynamic history of the Southeastern European Variscan Belt, including the Corsica, Sardinia and Maures-Tanneron massifs, is challenging, because it developed in a context of orogen-parallel extension associated with ductile strike-slip shearing. While this question is often addressed by studying the tectono-metamorphic evolution of deep crustal level, new answers could be provided by studying the infill and geometry of the contemporary sedimentary basins. Here, we investigate the Maures-Tanneron Massif (Provence, southeastern France), structured during the Devonian and Carboniferous with high-grade metamorphism related to the crustal thickening of the Variscan orogeny. It displays two intramountain late-Carboniferous basins: the Reyran and Plan-de-la-Tour basins, relatively well-preserved at present-days, and supposedly developed during the latest stages of the Variscan Orogeny. We document (i) the nature of the basin infills, the depositional environments and sedimentary fluxes through time, (ii) the relationship between basin deposits and the basement, and (iii) the volcanic contribution. We aim to discuss the timing of the basin development and deformation in relation to the tectonic and magmatic setting. In the light of recent sedimentological concepts, the observations in the Reyran and Plan-de-la-Tour basins contrast with the previous attribution to fluvial-dominated environments. Instead, we show that most of the sediments were deposited in subaqueous environments, i.e. in a relatively shallow lake, with sedimentary fluxes supplied by river-delta systems dominated by flood processes and subordinate hyperpycnal flows. Little subaerial lake-plain or delta-plain deposits are preserved. Regarding (i) the spatial distribution of the facies through time, (ii) the nature of the contacts with both the basement and the overlying Permian strata, (iii) the syn- to post-sedimentary deformation of the Carboniferous strata, (iv) the deformation of the crystalline basement, and (v) new U–Pb ages obtained on interbedded or neighboring plutonic and volcanic rocks, we also question the current tectonic model for the development of the Carboniferous basins in this area, and bring new insights on the tectonic and tectono-magmatic histories.
(30/10/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOAZUR 7329, INSU - CNRS, UniCA, CNRS, IRD [Occitanie], IRD, UniCA, BRGM, GR, UR, INSU - CNRS, CNRS
Architectures et modélisation géologique 3D des réservoirs argilo-sableux apto-albiens d'Île-de-France (Bassin de Paris) pour des applications en géothermie
En Île-de-France, la stratégie énergie-climat régionale prévoit d’augmenter assez significativement la production de chaleur par géothermie à l’horizon 2030. Il devient nécessaire de proposer des solutions qui envisagent l’exploitation de nouvelles zones, et les réservoirs argilo-sableux du Crétacé inférieur apparaissent comme une cible qu’il convient de mieux caractériser pour optimiser son développement. Or les hétérogénéités de ces réservoirs en termes de continuité ou d’épaisseur des niveaux sableux et/ou de niveaux argileux, de minéralogie ou de granulométrie sont très peu documentées. Dans le cadre du projet ANR UPGEO, une base de données rassemblant les logs et données pétrophysiques de puits profonds d’exploration, pétroliers, géothermiques ou encore de stockage de gaz en ˆIle-de-France a été constituée à partir de la Banque du Sous-Sol (BSS) mise à disposition sur InfoTerre par le BRGM, ou par notre partenaire GEOFLUID, ou encore par STORENGY. Parmi cette base, 133 puits traversant les sables de l’Albien ont été sélectionnés, comprenant au moins une diagraphie (GR) et/ou des descriptions de carottes (forage d’Orsay). Le périmètre s’étend du nord de la Seine-Saint-Denis jusqu’au sud de l’Essonne et de la Seine et Marne (110 x 85km). A partir des travaux de Sévenier et Lasseur (2016), ainsi que de la description de carottes de deux forages des sites de stockage de gaz de STORENGY à Crouy-sur-Ourcq et Beynes, un réexamen des faciès et séquences stratigraphiques a été réalisé. L’étude détaillée des faciès sur carottes a permis de reconnaître des faciès attribués à un environnement de dépôt côtier, plutôt estuarien, et avec une dynamique sédimentaire dominée par les courants tidaux. 19 transects de corrélations ont été réalisés suivant des principes de stratigraphie séquentielle, et 7 séquences stratigraphiques ont ainsi été identifiées et hiérarchisées en trois cycles majeurs. Ces transects permettent d’illustrer la géométrie des corps réservoirs et de retracer les évolutions paléoenvironnementales au cours de l’Albien inférieur. A partir de ces interprétations, des cartes paléogéographiques ont été établies et un modèle géologique 3D habillé en faciès construit. Celui-ci pourra servir de base à la création d’un modèle réservoir afin de réaliser `a terme des simulations d’écoulements hydrothermodynamiques dans le cadre du projet.
(30/10/2023)
GEOPS, INSU - CNRS, CNRS, IFPEN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Degradation of azoxystrobin, methoxyfenozide, and propyzamide by ultrasound treatment
Ultrasound as a green and efficient process gains special attention in wastewater treatment. The ultrasound-assisted degradation of azoxystrobin, methoxyfenozide, and propyzamide as widely used pesticides for vine treatment was investigated. A wide range of ultrasonic power (40 to 140 W) and a single frequency (20 kHz) were applied. Degradation experiments were carried out according to the parameters set by a central composite design (CCD) under response surface methodology (RSM) via JMP software. The treatment efficiency was quantified using degradation rates and hydrogen peroxide (H2O2) measurements. Results indicated that the pesticide’s degradation was negligible at 40 W but by increasing the power setting from 80 to 140 W, the degradation rate constants of azoxystrobin, methoxyfenozide, and propyzamide increased from 3.6 × 10−2 min−1 to 0.2 min−1, from 6.1 × 10−2 min−1 to 0.3 min−1, and from 3.1 × 10−2 min−1 to 0.1 min−1, respectively. The hydrogen peroxide (H2O2) measurements confirmed this trend. Besides, electric energy per order of pollutant removal (EE/O) was also evaluated for the same treatment duration and results revealed that treatment conditions of 20 kHz and 140 W were the less energy-guzzling. Finally, profiles obtained with RSM illustrated linear degradation kinetics for azoxystrobin and propyzamide. Indeed, treatment efficiency increased when increasing both studied parameters. However, both linear and quadratic degradation kinetics occurred for methoxyfenozide degradation indicating a parameter threshold beyond which the trend is reversed. Overall, this study confirms the effectiveness of ultrasound for the degradation of pesticides in aqueous medium.
(Environmental Science and Pollution Research. vol. 30, n° 0944-1344, pp. 114239-114248, 19/10/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Environmental controls on the brGDGT and brGMGT distributions across the Seine River basin (NW France): Implications for bacterial tetraethers as a proxy for riverine runoff
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial lipids that have been largely used as environmental proxies in continental paleorecords. Another group of related lipids, branched glycerol monoalkyl glycerol tetraethers (brGMGTs), has recently been proposed as a potential paleotemperature proxy. Nevertheless, the sources and environmental dependencies of both brGDGTs and brGMGTs along the river-sea continuum are still poorly understood, complicating their application as paleoenvironmental proxies in aquatic settings. In this study, the sources of brGDGTs and brGMGTs and the potential factors controlling their distributions are explored across the Seine River basin (NW France), which encompasses the freshwater to seawater continuum. To this aim, brGDGTs and brGMGTs were analyzed in soils, Suspended Particulate Matter (SPM) and sediments (n=237) collected all along this basin, from land to sea. Both types of compounds are shown to be produced in situ, in freshwater as well as saltwater. Redundancy analysis further shows that both salinity and nitrogen loadings dominantly control the brGDGT distributions. Furthermore, the relative abundance of 6-methyl vs. 5-methyl brGDGTs (IR6Me ratio), Total Nitrogen (TN), δ15N and chlorophyll a concentration co-vary in a specific zone with low salinity, suggesting that 6-methyl brGDGTs are preferentially produced under low-salinity and high-productivity conditions. In contrast with brGDGTs, brGMGT distribution appears to be primarily regulated by salinity, with a distinct influence on the individual homologues. Salinity is positively correlated with homologues H1020a and H1020b, and negatively correlated with compounds H1020c and H1034b. This suggests that bacteria thriving in freshwater preferentially produce compounds H1020c and H1034b, whereas bacteria primarily growing in saltwater appear to be predominantly responsible for the production of homologues H1020a and H1020b. Based on the abundance ratio of the freshwater-derived compounds (H1020c and H1034b) vs. saltwater-derived homologues (H1020a and H1020b), a novel proxy, Riverine IndeX (RIX) is proposed to trace riverine organic matter inputs, with high values (>0.5) indicating higher riverine contribution. RIX was then applied to the Godavari River basin (India) and a paleorecord across the upper Paleocene and lower Eocene, showing its potential applicability in both modern samples and in paleorecords.
(18/10/2023)
METIS, EPHE, PSL, INSU - CNRS, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ECOBIO, UR, INEE-CNRS, CNRS, CNRS, LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse
Potential of Marine Strains of Pseudoalteromonas to Improve Resistance of Juvenile Sea Bass to Pathogens and Limit Biofilm Development
The European sea bass (Dicentrarchus labrax), one of the most produced marine fish species in Europe, is acutely vulnerable to multiple infectious hazards. In this study, we investigated the potential probiotic effect of some marine Pseudoalteromonas bacterial strains against two major pathogens of this species, Vibrio harveyi and the nervous necrosis virus (NNV), and examined their antibiofilm effect. Impregnation phase was done by repeated immersion of juvenile’s sea bass during 8 to 12 weeks in seawater containing the probiotic candidates at a concentration of 106 CFU/mL. Four candidates were tested: (1) a combination of two strains producing antimicrobial compounds, hCg-42 and hOe-125; (2) strain 3J6, with known antibiofilm properties; (3) strain RA15, from the same genus, but with no identified probiotic effect; and (4) a control group without probiotics. At the end of the impregnation phase, fish underwent an infection challenge with V. harveyi or with a pathogenic strain of NNV and mortality was monitored. For the V. harveyi challenge, improved survival rates of 10 and 25% were obtained for the RA15 and the mix hCg-42 + hOe-125-impregnated groups, respectively. For the NNV challenge, no significant benefic effect of the probiotics on infection kinetics or cumulative mortality was observed. At the end of the impregnation phase, the maximal thickness of biofilm was significantly lower in the 3J6, double strain, and RA15 groups, compared with the non-impregnated control group. This study highlights the interesting probiotic potential of marine bacteria to limit mortalities induced by bacterial pathogens as well as biofilm development.
(Probiotics and Antimicrobial Proteins, n° 1867-1306, 18/10/2023)
LBCM, UBS, UBO EPE, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, CNRS, ANSES, VIMEP, ANSES, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
NOTES ON PROOF BY DICHOTOMY
In this document we define a method of proof that we call proof by dichotomy. Its field of application is any proposition on the set of natural numbers N. It consists in the repetition of a step. A step proves the proposition for half of the members of an infinite subset U of N members for which we neither know if the proposition is verified nor not. We particularly study the case where the elements of U are separated by the parity of the quotient of euclidean division by 2 k. In such a case, we prove that if a natural n does not verify the proposition, then it is unique.
(04/10/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Somatic evolution of marine transmissible leukemias in the common cockle, Cerastoderma edule
Transmissible cancers are malignant cell lineages that spread clonally between individuals. Several such cancers, termed bivalve transmissible neoplasia (BTN), induce leukemia-like disease in marine bivalves. This is the case of BTN lineages affecting the common cockle, Cerastoderma edule, which inhabits the Atlantic coasts of Europe and northwest Africa. To investigate the evolution of cockle BTN, we collected 6,854 cockles, diagnosed 390 BTN tumors, generated a reference genome and assessed genomic variation across 61 tumors. Our analyses confirmed the existence of two BTN lineages with hemocytic origins. Mitochondrial variation revealed mitochondrial capture and host co-infection events. Mutational analyses identified lineage-specific signatures, one of which likely reflects DNA alkylation. Cytogenetic and copy number analyses uncovered pervasive genomic instability, with whole-genome duplication, oncogene amplification and alkylation-repair suppression as likely drivers. Satellite DNA distributions suggested ancient clonal origins. Our study illuminates long-term cancer evolution under the sea and reveals tolerance of extreme instability in neoplastic genomes.
(Nature Cancer, 02/10/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Prokaryotic, Microeukaryotic, and Fungal Composition in a Long-Term Polychlorinated Biphenyl-Contaminated Brownfield
Polychlorinated biphenyls (PCBs) are recognized as persistent organic pollutants and accumulate in organisms, soils, waters, and sediments, causing major health and ecological perturbations. Literature reported PCB bio-transformation by fungi and bacteria in vitro, but data about the in situ impact of those compounds on microbial communities remained scarce while being useful to guide biotransformation assays. The present work investigated for the first time microbial diversity from the three-domains-of-life in a long-term contaminated brownfield (a former factory land). Soil samples were ranked according to their PCB concentrations, and a significant increase in abundance was shown according to increased concentrations. Microbial communities structure showed a segregation from the least to the most PCB-polluted samples. Among the identified microorganisms, Bacteria belonging to Gammaproteobacteria class, as well as Fungi affiliated to Saccharomycetes class or Pleurotaceae family, including some species known to transform some PCBs were abundantly retrieved in the highly polluted soil samples.
(Microbial ecology. vol. 86, n° 0095-3628, pp. 1696 - 1708, 01/10/2023)
LEM, UCBL, ENVL, VAS, CNRS, INRAE, LIEC, INSU - CNRS, UL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IUF, M.E.N.E.S.R.