The Bengal fan: external controls on the Holocene Active Channel turbidite activity
The eastern levee of the Active Channel in the Bengal fan has been investigated in order to better understand the history of turbidite activity in this channel during the Holocene in the context of Ganges-Brahmaputra source-to-sink' system. A robust C-14-based chronostratigraphy provides high temporal resolution for reconstructing sediment accumulation history on the eastern levee of the Active Channel. Integration of this study with previous work in the area suggests that the Bengal fan has remained continually connected with the Ganges-Brahmaputra fluvial system through the Holocene, feeding through the main canyon, the Swatch of No Ground (SoNG). An intense turbidite activity occurred during a transgressive wet period from 14.5 to 9.2 ka cal. BP, followed by an abrupt shift in sedimentation at 9.2 ka cal. BP, probably due to the high sea level leading to a partial disconnection between massive river discharges and the deep turbidite system. During the last 9.2 ka cal. BP, turbidite activity is still present but irregular, likely modulated by a combination of various forcings such as monsoon variability and river migration. In total, three phases are distinguishable during this period: 9.2-5.5, 5.5-4, and 4 ka cal. BP to modern, according to the turbidite record. Unexpectedly, the Indo-Asian monsoon does not appear to be the only predominant forcing on the establishment of the Bengal fan during the Holocene because of the combination of different forcings directly affecting transfers between the Ganges-Brahmaputra and the Bengal fan as well as river migrations, delta construction, and potentially anthropogenic impact.
(The Holocene. vol. 27, n° 0959-6836, pp. 900-913, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SCTA, UQAM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOPS, UP11, CNRS, EMBS, iSTeP, UPMC, CNRS
Gravity-Driven Deposits in an Active Margin (Ionian Sea) Over the Last 330 000 Years
(Geochemistry, Geophysics, Geosystems, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SHOM, LMV, IRD, INSU - CNRS, UJM, UCA [2017-2020], CNRS, LDO, INSU - CNRS, UBO EPE, CNRS
Signification environnementale de guano de salanganes et de chiroptères de Nouvelle-Calédonie. Premiers résultats
L'intérêt est grandissant pour le potentiel présenté par les acccumulations cavernicoles de guano de chauves-souris et d'oiseaux en tant qu'enregistrements stratigraphiques continentaux, complémentaires voire alternatifs aux archives étudiées générale-ment (sédiments lacustres, palustres, tourbeux, etc.). Ces dépôts permettent des reconstructions de la variabilité climatique à haute résolution pour des échelles de temps récentes à plus anciennes, grâce à la calibration de nouveaux proxies susceptibles d'enregistrer ces variations. Ainsi la comparaison du contenu pollinique et des traceurs isotopiques δ13 C et δD des n-alcanes du guano de différents animaux insectivores, les salanganes diurnes (Collocalia spodiopygia) et les chiroptères nocturnes (Micropterus robustior) cohabitant dans de nombreuses grottes de Nouvelle-Calédonie, met en évidence une grande variabilité. Celle-ci est à l'image des cibles de nourrissage des proies appétées et de leur interaction avec les composantes de l'écosystème, en particulier les plantes. La grande richesse du contenu pollinique observée dans les deux types de guano, bien que présentant 50 % de taxons communs, souligne des aires de nourrissage préférentielles. Elle montre aussi des fluctuations interannuelles, marqueurs probables de changements environnementaux, sinon climatiques. Cet article présente des premiers résultats obtenus sur le sondage HAK1 prélévé dans un amas de guano de salanganes de la grotte Hama sur l'île de Lifou, l'une des îles Loyautés. La comparaison entre les données de géochimie isotopique moléculaire (isotopes du carbone δ13C et de l'hydrogène δD du n-alcane C29) et les données pluviométriques met en évidence une bonne covariation interprétée comme marqueur du signal climatique ENSO contemporain des dépôts de guano analysés. Ce travail préliminaire confirme le fort potentiel des amas de guano cavernicoles pour étudier à haute résolution les changements paléo-environnementaux.
(Quaternaire. vol. 28, n° 1142-2904, pp. 401-412, 27/04/2026)
BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IAC
Sub-Antartic glacier extensions in the Kerguelen region (49° S, Indian Ocean) over the past 24 000 years constrained by 36Cl moraine dating
Similar to many other regions in the world, glaciers in the southern sub-polar regions are currently retreating. In the Kerguelen islands (49°S, 69°E), the mass balance of the Cook Ice Cap (CIC), the largest ice cap in this region, experienced dramatic shrinking between 1960 and 2013 with retreat rates among the highest in the world. This observation needs to be evaluated in a long-term context. However, data on the past glacier extents are sparse in the sub-Antartic regions. To investigate the deglaciation pattern since the Last Glacial Maximum (LGM) period, we present the first 13 cosmogenic 36Cl surface exposure ages from four sites in the Kerguelen Islands. The 36Cl ages from erratic and moraine boulders span form 24.4 ± 2.7 ka to 0.3 ± 0.1 ka. We combined these ages with existing glacio-marine radiocarbon ages and bathymetric data to document the temporal and spatial changes of the island's glacial history. Ice began to retreat on the main island before 24.4±2.7 ka until around the time of the Antartic Cold Reversal (ACR) period (-14.5-12.9ka), during which the Bontemps moraine was formed by the advance of a CIC outlet glacier. Deglaciation continued during the Holocene probably until 3ka with evidence of minor advances during the last millennium. The chronology is in pace with major changes in ᵟ18O in a recent West Antarctica ice core record, showing thet Kerguelen Islands glciers are particularly sensitive and relevant to document climate change in the southern polar regions.
(Quaternary Science Reviews. vol. 162, n° 0277-3791, pp. 128-144, 27/04/2026)
LGP, UP1, UPEC UP12, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, ISTO, BRGM, INSU - CNRS, UO, CNRS, GEODE, UT2J, Comue de Toulouse, CNRS, ISTO, BRGM, INSU - CNRS, UO, CNRS, IGE, IRD, Grenoble INP, INSU - CNRS, CNRS, UGA [2016-2019], Fédération OSUG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPEV, M.E.N.E.S.R.
Earthquake imprints on a lacustrine deltaic system: The Kürk Delta along the East Anatolian Fault (Turkey)
Deltas contain sedimentary records that are not only indicative of water-level changes, but also particularly sensitive to earthquake shaking typically resulting in soft-sediment-deformation structures. The Kürk lacustrine delta lies at the south-western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re-evaluates water-level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic-reflection profiles and side-scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water-level changes provides a temporal framework for the depositional record. In addition to the common soft-sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake-induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating ($^{137}$Cs and $^{210}$Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X-ray imagery, X-ray diffraction, loss-on-ignition, grain-size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post-seismic sediment reworking of earthquake-triggered landslides.
(Sedimentology. vol. 64, n° 0037-0746, pp. 1322-1353, 27/04/2026)
ULiège, UGent, KAUST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ITU
Post-depositional evolution over a time scale of 1 million years of eastern Mediterranean organic-rich and organic-poor sediments: new insights on the debromination and layer-silicate markers
Organic matter degradation is the engine behind the biogeochemical evolution of sediments during burial. Previous research has shown that eogenesis is the seat of a complex interplay between organic matter, microbes and the most reactive part of inorganic compounds, such as clay minerals. To explore the variability and stability of bromine and clay minerals as geochemical and mineral tracers, we selected an eastern Mediterranean core that has a high degree of stability in the quality and quantity of organic matter through time at a one-million-year scale and great variability in organic matter content at a 10 ky scale. According to the very low maximal burial depth reached by these sediments (the core length is only 36.5 m), physical parameters, such as temperature and pressure, did not significantly influence the evolution of the studied parameters during the burial history. The bulk clay mineralogy of organic-rich and organic-poor sediments is similar all along the investigated core material; smectite predominates over kaolinite. The only identified authigenic minerals are biogenetic framboidal pyrite and manganese oxides. The X-ray data and the chemical compositions of the smectite are characteristic of a montmorillonite which is representative of a detrital Nile source. At a one-million-year scale, the organic matter content has no significant influence on clay eogenesis, and detrital smectite and kaolinite remain unchanged. Bromine is present in marine organic matter as organobromine compounds. During eogenesis, bromine is released from organic matter as bromide ion, resulting in an increase in the bromide concentration in the pore water with depth. Dissolved bromide can be used as a conservative tracer of the debromination of sedimentary organic matter. For the first time, we established that solid-phase BrOrg is a reliable tracer of debromination rates in marine sediments. The rate of debromination depends on the organic matter content. The rate increases from less than 2.3 × 10−4 μmolBrOrg mol.C−1.y−1 to 6.3 × 10−4 μmolBrOrg mol.C−1.y−1 when TOC varies from 0.17 to 3%. This increase is related to the development of the bacterial population and provides the basis for further investigation of other oceanic basins. For TOC values >4%, the rate of debromination decreases. We propose that the bioavailability of organic matter is another factor of variability in the debromination rate.
(Bulletin de la Société Géologique de France. vol. 188, n° 0037-9409, pp. 21, 27/04/2026)
LUSAC, UNICAEN, NU, IC2MP [Poitiers], UP, INC-CNRS, CNRS, EMBS, iSTeP, UPMC, CNRS, ETH Zürich, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CINaM, AMU, CNRS
How annual course of photoperiod shapes seasonal behavior of diploid and triploid oysters, Crassostrea gigas
In this work, we study if ploidy (i.e. number of copies of chromosomes) in the oyster Crassostrea gigas may introduce differences in behavior and in its synchronization by the annual photoperiod. To answer to the question about the effect of the seasonal course of the photoperiod on the behavior of C. gigas according to its ploidy, we quantified valve activity by HFNI valvometry in situ for 1 year in both diploid and triploid oysters. Chronobiological analyses of daily, tidal and lunar rhythms were performed according the annual change of the photoperiod. In parallel, growth and gametogenesis status were measured and spawning events were detected by valvometry. The results showed that triploids had reduced gametogenesis, without spawning events, and approximately three times more growth than diploids. These differences in physiological efforts could explain the result that photoperiod (daylength and/or direction of daylength) differentially drives and modulates seasonal behavior of diploid and triploid oysters. Most differences were observed during long days (spring and summer), where triploids showed longer valve opening duration but lower opening amplitude, stronger daily rhythm and weaker tidal rhythm. During this period, diploids did major gametogenesis and spawning whereas triploids did maximal growth. Differences were also observed in terms of moonlight rhythmicity and neap-spring tidal cycle rhythmicity. We suggest that the seasonal change of photoperiod differentially synchronizes oyster behavior and biological rhythms according to physiological needs based on ploidy.
(PLoS ONE. vol. 12, n° 1932-6203, pp. e0185918, 27/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Mission Baelo Claudia. Rapport d'activités
(27/04/2026)
LIENSs, INSU - CNRS, ULR, CNRS, HALMA, CNRS, MC, IRAA, UL2, AMU, CNRS, HeRMA [Poitiers], UP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Benthic production, respiration and methane oxidation in Lobelia dortmanna lawns
Isoetid macrophytes such as Lobelia dortmanna and Littorella uniflora are engineering species with an extensive root system and high radial oxygen loss (ROL). Despite several studies on these macrophytes, the effect of their oxygenation on methane dynamics has never been investigated. In this study, we hypothesize that isoetids promote dissolved inorganic carbon (DIC) fixation and methane (CH4) oxidation in sandy sediments. Our whole-ecosystem approach study lasted two years (2013-2014) on two oligo-mesotrophic shallow lakes. Benthic chamber incubations confirmed that, as a result of primary production and methanotrophy, isoetid lawns had consistently lower benthic carbon fluxes than bare sediments. On a daily basis, vegetated areas acted as a carbon sink (-0.7 ± 0.4 g C m-2d-1, as DIC + CH4) whereas bare sediments acted as a net source (0.6 ± 0.5 g C m-2d-1, as DIC + CH4). Photosynthetic quotients of < 1 indicated that photosynthetically-produced oxygen was not released into the water column, but accumulated in leaf lacunae or was transferred to the rhizosphere, that contributing to the alteration of net benthic fluxes at the sediment-water interface. This preliminary study highlights the necessity of further investigating the role that isoetids play in mitigating greenhouse gas emissions from temperate shallow lakes.
(Hydrobiologia, n° 0018-8158, pp. 21-34, 27/04/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Migratory behavior, metabolism, oxidative stress and mercury concentrations in marine and estuarine European glass eels (Anguilla anguilla)
The relationships between the migratory behavior, methylmercury (MeHg) concentrations, oxidative stress response and detoxification processes were investigated in glass eels collected in marine (Molliets) and estuarine (Urt) waters (Adour estuary, South West France) at the end of the fishing season (April). Glass eel migratory behavior was investigated in an experimental flume according to their response to dusk. Fish responding to the decrease in light intensity by ascending in the water column and moving with or against the flow were considered as having a high propensity to migrate (migrant). Glass eels still sheltering at the end of the 24 h catching period were considered as having a low propensity to migrate and were called non-migrant. Our results provide some evidence that estuarine glass eels were bigger, presented a higher propensity to migrate and a lower oxidative stress response than marine glass eels. This might reflect a selection process, some marine glass eels progressively settling or dying before reaching Urt and/or a change in feeding behavior. In April, glass eels restart feeding in the Adour estuary which might decrease the oxidative stress possibly related to starvation, and enhance migration. MeHg concentrations was significantly higher in non-migrant than in migrant glass eels and it is suggested that non-migrant glass eels might present a higher vulnerability to stress (at least contamination and/or starvation), although the underlying mechanisms remain to be elucidated. © 2016 Elsevier Inc.
(Physiology & behavior. vol. 169, n° 0031-9384, pp. 33--40, 27/04/2026)
ECOBIOP, INRA, UPPA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS