High-resolution stratigraphic forward modeling of a Quaternary carbonate margin: Controls and dynamic of the progradation
The relationships between the margin sedimentary regime and the platform progradation are studied using forward stratigraphic numerical simulations on the Leeward (Western) prograding margin of the Great Bahama Bank (GBB) during the Quaternary (1.7–0 Ma). The corresponding sedimentary regime in the slope and the platform is well known from the ODP leg 166 and Bahamas Drilling Project wells located along the “Western line” seismic transect. However the sedimentary regime on the margin is not well established: the coral reefal margin observed before between 1.7 and 0.8 Ma in the well Clino is not active anymore at present-day, and the Holocene sedimentary regime is geometrically unable to account alone for the progradation. This study is based on three 2D high-resolution forward stratigraphic numerical modeling experiments with the software DionisosFlow that include the platform, margin and slope domains on the “Western Line Section” in the same sedimentary models. The results are compared to the six sedimentary cores and to the present day bathymetry in order to identify the more realistic scenario. The three experiments test different models of carbonate sediment production and transport. Experiment 1 shows that the highstand shedding of the fine-grained uncemented platform production is unable to reproduce the progradation and the present-day profile. Experiments 2 and 3 incorporate cemented facies in the margin, with the best results obtained with the cemented marginal wedges produced in Experiment 2 during platform emersion. From these results a high-resolution interpretation of the margin seismic section is proposed. This study shows that the platform progradation can be decoupled from the highstand shedding of the fine-grained platform production. It is dependent on the accumulation in front of the steep margin of coarse or cemented material. Before 0.8 Ma this corresponds to the coral reef identified in Clino. The transition after 0.45 Ma to 100-kyr large eustatic cycles with total platform flooding created two distinct marginal regimes: (1) during platform flooding aggrading accumulation of non-skeletal sands, and (2) during platform emersion prograding cemented marginal wedges produced in-situ.
(Sedimentary Geology. vol. 379, n° 0037-0738, pp. 77-96, 01/01/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFPEN, [Total Energies. Anciennement : Total, TotalFina, TotalFinaElf], CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, UHH
Kleptoplastidic benthic foraminifera from aphotic habitats: insights into assimilation of inorganic C, N and S studied with sub-cellular resolution
(Environmental Microbiology, n° 1462-2912, 01/01/2019)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, WHOI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPFL
Into the deep: A coarse-grained carbonate turbidite valley and canyon in ultra-deep carbonate setting
New high-resolution multibeam mapping images detail the southern part of Exuma Sound (Southeastern Bahamas), and its unchartered transition area to the deep abyssal plain of the Western North Atlantic, bounded by the Bahama Escarpment extending between San Salvador Island and Samana Cay. The transition area is locally referred to as Exuma Plateau. The newly established map reveals the detailed and complex morphology of a giant valley draining a long-lived carbonate platform from its upper slope down to the abyssal plain. This giant valley extends parallel to the slope of Long Island, Conception Island, and Rum Cay. It starts with a perched system flowing on top of a lower Cretaceous drowned main carbonate platform. The valley shows low sinuosity and is characterized by several bends and flow constrictions related to the presence of the small relict isolated platforms that kept alive longer than the main platform before drowning and merging tributaries. Turbidite levees on either side of the valley witness the pathway of multiple gravity flows, generated by upper slope over steepening around Exuma Sound through carbonate offbank transport, some of them locally >15°, and resulting slumping. In addition, additional periplatform sediments are transported to the main valley through numerous secondary slope gullies and several kilometre-long tributaries, draining the upper slopes of cays and islands surrounding Exuma Plateau. Some of them form knickpoints indicating surincision of the main Exuma Valley which is consistent with an important lateral supply of the main Exuma Valley. Prior to reaching the abyssal plain, the main valley abruptly evolves into a deep canyon, 5 km in width at its origin and as much as 10 km wide when it meets the abyssal plain, through two major knickpoints named “chutes” with outsized height exceeding several hundred of meters in height. Both chutes are associated with plunge pools, as deep as 200-m. In the deepest pools, the flows generate a hydraulic jump and resulting sediment accumulation. When the canyon opens to the San Salvador abyssal plain, the narrow, deep, and strong flows release significant volume of coarse-grained calcareous sediments in numerous turbidite layers interbedded with fine mixed siliciclastic and carbonate sediments transported by the Western Boundary Undercurrent (WBUC) along the Bahama Escarpment. Carbonate gravity flows exiting the canyon decelerate at the abyssal plain level and construct a several-kilometre-wide coarse-grained deep-sea turbidite system with well-developed lobe-shape levees, partially modified by the flow of strong contour-currents along the Bahama Escarpment.
(Marine Geology. vol. 407, n° 0025-3227, pp. 316-333, 01/01/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, KFUPM, IPGP, INSU - CNRS, UPD7, UR, IPG Paris, CNRS, RSMAS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, UNIGE, IFPEN
Analyses préliminaires d'une chondrite ordinaire NWA XXX de type L
(18/10/2026)
UB, LAB, UB, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEESA, UB, CNRS, PACEA, UB, CNRS, ENSAM
Influence of parasitism on bioturbation: from host to ecosystem functioning
Bioturbating species represent a typical example of ecosystem engineer species in marine benthic environments. These abundant endo- or epibenthic organisms modify the physical structure and geochemical properties of sediments and, at broader ecosystem scales, impact nutrient flows and benthic community structure. The ecological importance of bioturbators depends on (1) their abundance and (2) the magnitude of their bioturbation activity. We suggest that parasitism has a substantial impact on bioturbators, with cascading effects on their role in ecosystem functioning. Reviewing 5940 papers concerning bioturbation and using a set of selective criteria, we identified 176 bioturbating species, with 31% of these potentially parasitized (micro- and macroparasites). However, there are significant discrepancies in the research effort on parasites among bioturbating groups, the highest effort being devoted to molluscs, whereas studies on annelids and arthropods are rare. Furthermore, studies addressing the impacts of parasites on their bioturbating hosts are still scarce, but evidence we do have indicates that parasites impair their hosts’ physiological state, fecundity, behaviour and survival. Because of impacts of parasites on phenotypic traits related to the bioturbation engineering activity of their hosts, parasitism could play a key role on ecosystem functioning through cascade effects. Yet, studies assessing the intricate link between parasites and their hosts’ bioturbation activity, including potential effects on ecosystem functioning, are very scarce.
(Marine Ecology Progress Series. vol. 619, n° 0171-8630, pp. 201-214, 18/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
River estuaries of the Amazon-influenced Guianas coast: diversity and preliminary classification
The morphology and dynamics of the 1500 km-long Guianas coast, South America, are strongly influenced by mud supplied by the Amazon River. A fraction of this mud (20% of nearly 1 billion tons annually) is organized into large banks that migrate along the coast under the influence of waves and currents, separated by 'inter-bank' zones. 'Bank' zones significantly dissipate the wave energy transmitted shoreward, whereas inter-bank zones are commonly characterized by a relatively mud-free shoreface, and wave energy is thus more efficiently transmitted to the shore. The alongshore alternation of shifting bank and inter-bank zones is strongly modulated by water discharge from the local rivers, which depends essentially on catchment size. The hydrology and sediment fluxes of many of these rivers, which drain the crystalline rocks of the Guiana Shield between the Amazon and the Orinoco River deltas, are still largely unknown. Even the catchment size of several of these rivers is not known with certainty. The relationship between discharge from these Guiana Shield rivers and the Amazon mud-bank belts results in a variety of estuarine morphological and dynamic configurations. Further estuarine diversity is engendered by lithology. A preliminary classification of 15 estuaries, based on plan morphology and ongoing analyses of estuarine hydrodynamics, suggests four basic types: (1) estuaries fixed by headlands of Precambrian basement rocks (Mahury, Cayenne, and Kourou Rivers); these are associated with small catchments and found only in French Guiana, where the basement crops out along the coast; (2) estuaries with mouths diverted westward (the direction of regional alongshore sediment transport) by prograded mud capes and spits, reflecting a significant influence of multi-decadal to multi-millennial coastal accretion of Amazon-derived mud (Cassipore, Uaça, Rivers in Amapa, Brazil; Oyapock between Brazil and French Guyana; Approuague, Sinnamary and Mana Rivers in French Guyana; Suriname and Coppename Rivers in Suriname; Berbice River in Guyana); (3) estuaries oriented normal to the coast and associated with relatively large-discharge rivers (Maroni River between French Guiana and Suriname; Corentyne River between Suriname and Guyana; (4) a prograded estuary mouth with a transitional morphology towards a delta (Essequibo River in Guyana, the largest river on the Guianas coast after the Amazon and the Orinoco). Ongoing monitoring of the sediment fluxes and hydrodynamics of a type 1 (Mahury) and a type 3 estuary (Maroni), both of which are fixed (lithologically for type 1, and hydrodynamically for type 3), and akin, morphologically, to normal trumpet-or funnel-shaped estuaries, shows a tropical seasonal regime but which is strongly influenced by Amazon mud during the low-discharge dry season. This mud influence from the distant Amazon constitutes a unique aspect of the river mouths on the Guianas coast.
(. vol. 21, 18/10/2026)
LEEISA, IFREMER, UG, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, LHSV, ENPC, EDF [E.D.F.], M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, IEPA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Beach recovery from extreme storm activity during the 2013/14 winter along the Atlantic coast of Europe
The storm sequence of the 2013/14 winter left many beaches along the Atlantic coast of Europe in their most eroded state for decades. Understanding how beaches recover from such extreme events is essential for coastal managers, especially in light of potential regional increases in storminess due to climate change. Here we analyze a unique dataset of decadal beach morphological changes along the west coast of Europe to investigate the post‐2013/14‐winter recovery. We show that the recovery signatureis site‐specific and multi‐annual, with one studied beach fully recovered after two years, and the others only partially recovered after four years. During the recovery phase, winter waves primarily control the timescales of beach recovery, as energetic winter conditions stall the recovery process while moderate winter conditions accelerate it. This inter‐annual variability is well correlated with climate indices. On exposed beaches, an equilibrium model showed significant skill in reproducing the post‐storm recovery and thus can be used to investigate the recovery process in more details.
(Earth Surface Processes and Landforms. vol. 44, n° 0197-9337, pp. 393-401, 18/10/2026)
LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SBMS, LGO, UBS, IFREMER, UBO EPE, CNRS
Analysis of Suspended Sediment Variability in a Large Highly Turbid Estuary Using a 5-Year-Long Remotely Sensed Data Archive at High Resolution
Spatial variability of surface suspended particulate matter (SPM) concentration in the Gironde estuary and their relationships with environmental forcing are investigated through high spatial resolution multispectral data collected from July 2013 to August 2018 by the Operational Land Imager (Landsat-8/OLI) and MultiSpectral Instrument (Sentinel-2/MSI). A principal component analysis using the T-mode orientation is applied to the discontinuous multiannual time series composed of 41 remotely sensed images. The three first principal components (PC1, PC2, and PC3) explain 65.7% of the total variance. The SPM distribution associated with PC1 and PC2 exhibits a privileged along-estuary direction of the oscillation modes, while the spatial patterns of PC3 are clearly dominated by lateral oscillations opposing channels and shoals. The main environmental factors affecting the SPM distribution are identified by the analysis of their temporal patterns. The tidal range and the daily river discharge control the spatial patterns of PC1 and PC2, while the tidal cycles and the wind speed are significantly correlated with PC3. Furthermore, the analysis in the along-estuary and lateral directions shows marked longitudinal and transverse SPM gradients and a strong control of bathymetry on the SPM spatial distribution. For the first time, we highlight that the maxima of surface residual turbidity are located on the shoals regardless of the environmental (tidal and hydrological) conditions. Compared to previous studies, usually based on single-point in-water column measurements, these results provide a novel and complementary description of the spatial variability of SPM. They are useful to validate sediment transport numerical models, but also may improve our understanding of suspended sediment dynamics in estuarine systems governed by an estuarine turbidity maximum.
(Journal of Geophysical Research. Oceans. vol. 124, n° 2169-9275, pp. 7661-7682, 18/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
Secondary Organic Aerosol Formation from Aromatic Alkene Ozonolysis: Influence of the Precursor Structure on Yield, Chemical Composition, and Mechanism
The influence of the precursor chemical structure on secondary organic aerosol (SOA) formation was investigated through the study of the ozonolysis of two anthropogenic aromatic alkenes: 2-methylstyrene and indene. Experiments were carried out in three different simulation chambers: ICARE 7300L FEP Teflon chamber (ICARE, Orléans, France), EUPHORE FEP Teflon chamber (CEAM, Valencia, Spain), and CESAM evacuable stainless steel chamber (LISA, Créteil, France). For both precursors, SOA yield and growth were studied on a large range of initial concentrations (from ∼60 ppbv to 1.9 ppmv) and the chemical composition of both gaseous and particulate phases was investigated at a molecular level. Gas phase was described using FTIR spectroscopy and online gas chromatography coupled to mass spectrometry, and particulate chemical composition was analyzed (i) online by thermo-desorption coupled to chemical ionization mass spectrometry and (ii) offline by supercritical fluid extraction coupled to gas chromatography and mass spectrometry. The results obtained from a large set of experiments performed in three different chambers and using several complementary analytical techniques were in very good agreement. SOA yield was up to 10 times higher for indene ozonolysis than for 2-methylstyrene ozonolysis at the same reaction advancement. For 2-methylstyrene ozonolysis, formaldehyde and o-tolualdehyde were the two main gaseous phase products while o-toluic acid was the most abundant among six products detected within the particulate phase. For indene ozonolysis, traces of formic and phthalic acids as well as 11 species were detected in the gaseous phase and 11 other products were quantified in the particulate phase, where phthaldialdehyde was the main product. On the basis of the identified products, reaction mechanisms were proposed that highlight specific pathways due to the precursor chemical structure. These mechanisms were finally compared and discussed regarding SOA formation. In the case of 2-methylstyrene ozonolysis, ozone adds mainly on the external and monosubstituted double bond, yielding only one C8- and monofunctionalized Criegee intermediate and hence more volatile products as well as lower SOA mass than indene ozonolysis in similar experimental conditions. In the case of indene, ozone adds mainly on the five-carbon-ring and disubstituted C═C double bond, leading to the formation of two C9- and bifunctionalized Criegee intermediates, which then evolve via different pathways including the hydroperoxide channel and form highly condensable first-generation products.
(Journal of Physical Chemistry A. vol. 123, n° 1089-5639, pp. 1469-1484, 18/10/2026)
LISA (UMR_7583), INSU - CNRS, UPD7, UPEC UP12, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LCE, AMU, INC-CNRS, CNRS, LASIRE, INC-CNRS, CNRS, ICARE, UO, CNRS, INSIS - CNRS
Comparing the efficiency of hypoxia mitigation strategies in an urban, turbid tidal river, using a coupled hydro sedimentary–biogeochemical model
In view of future coastal hypoxia widespreading, it is essential to define management solutions to preserve a good quality of coastal ecosystems. The lower Tidal Garonne River (TGR, SW France), characterized by the seasonal presence of a turbidity maximum zone and urban water discharges, is subject to episodic hypoxia events during summer low river flow periods. The future climatic conditions (higher temperature; summer droughts) but also an increasing urbanization could enhance hypoxia risks near the city of Bordeaux in the next decades. A 3D model of dissolved oxygen (DO), which couples hydrodynamics, sediment transport and biogeochemical processes, is used to assess the efficiency of different management solutions on TGR oxygenation during summer low-discharge periods. We have runned different scenarios of reduction of urban sewage overflows, displacement of urban discharges downstream from Bordeaux, and/or temporary river flow support during summer period. The model shows that each option limits hypoxia, but with variable efficiency over time and space. Sewage overflow reduction improves DO levels only locally near the city of Bordeaux. Downstream relocation of wastewater discharges allows to reach better oxygenation level in the lower TGR. The support of low river flow limits the upstream TMZ propagation and dilutes TGR waters with well-oxygenated river waters. Scenarios combining wastewater network management and low water replenishment indicate an improvement in water quality over the entire TGR. These modelling outcomes constitute important tools for local water authorities to develop the most appropriate strategies to limit hypoxia in TGR
(Natural Hazards and Earth System Sciences Discussions, n° 2195-9269, pp. 1-32, 18/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LyRE, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA