Expedition 397 Preliminary Report: Iberian Margin Paleoclimate
From 11 October to 11 December 2022, International Ocean Discovery Program Expedition 397 took place off the coast of Portugal southwest of Lisbon. The main objective was to recover the exceptional sedimentary archive preserved beneath the seafloor on the Iberian margin to study past climate change at high temporal resolution. During the expedition, which carried 26 international scientists, four sites were drilled, recovering 6.2 km of marine sediments that accumulated rapidly, thereby providing a high-fidelity record of past climate change on timescales of hundreds to thousands of years and extending back millions of years ago. Climate signals from these marine sediment cores will be correlated precisely to polar ice cores from both hemispheres and with European pollen records, providing a rare opportunity to link oceanic, atmospheric, and terrestrial climate and environmental changes. The four drill sites are located at different water depths (1339, 2590, 3479 and 4691 m below sea level), permitting scientists to study how deep-ocean circulation and chemistry changed in the past, including its role in deep-sea carbon storage and atmospheric CO2 changes. The sediment cores recovered during Expedition 397 will provide benchmark records of North Atlantic climate change at high temporal resolution from the late Miocene (about 8 million years ago) to present. This period includes the last 3 million years when changes in the Earth's orbit resulted in the growth and decay of large ice sheets in the Northern Hemisphere and a warmer world before this time when atmospheric CO2 was similar to today. All cores recovered show strong changes in physical properties (such as color) that represent a response to known cyclic changes in Earth’s orbit, which will aid in accurately dating the sediment. Many years of research will be needed to extract the detailed climatic signals from the kilometers of core recovered during Expedition 397, but the records to be produced will be vital for testing numerical climate models and understanding how the climate system works and how it might change in the future.
(International Ocean Discovery Program Preliminary Reports, n° 2372-9562, pp. 397, 20/06/2026)
IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contribution des méthodes d'imagerie drone à l'étude des bassins fracturés : application à la plate-forme mésozoïque nord-Aquitaine.
Dans les bassins sédimentaires, la connaissance du réseau de fractures et de la manière dont il s'est développé au cours du temps permettent de mieux contraindre les conditions actuelles de migration des fluides (eaux, saumures, hydrocarbures, CO2). Bien que souvent associés aux données de reconnaissances (sismique 3D, forages...), ces réseaux peuvent également être observés et caractérisés à partir d'affleurements sur le terrain. Les surfaces stratigraphiques, en particulier, font l'objet d'un nombre croissant d'études avec le développement de l'imagerie à haute résolution à partir de drone. L'objectif de cette étude est de caractériser le réseau de fracturation de la partie nord du bassin Aquitain afin de reconnaître les principaux épisodes de fracturations. Pour cela, des ortho-images drone ont été acquises sur le littoral Atlantique entre la Vendée et la Charente Maritime. L'âge des terrains varient depuis l'Hettangien au nord jusqu'au Tithonien au sud. Cet enregistrement sédimentaire permet potentiellement d'estimer l'âge des déformations sur l'intervalle 200-150 Ma à l'aide des critères de chronologie relative. Cette approche est complétée par datation U/Pb sur cristaux de calcite qui remplissent certaines populations de fractures. Les premiers résultats mettent en évidence une période de calme tectonique entre 200 et 150 Ma, suivie par deux phases d'ouverture de fractures orientées E-W à la fin du Jurassique et au milieu du Crétacé supérieur. Localement, une reprise en compression selon une direction NNW-SSE recoupe l'ensemble des fractures en ouverture et est attribuée à la propagation en champ lointain de contraintes Pyrénéennes.
(20/06/2026)
LPG - Le Mans, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS
Temperature variations in caves induced by atmospheric pressure variations-Part 2: Unveiling hidden thermal signals
In underground cavities, temperature variations of the order of 10-3 °C are permanently induced by the variations of atmospheric pressure, even at great depths, with couplings of the order of 0.2 to 20 × 10-3 °C/hPa depending on frequency. In the first part of this study, we established the atmospheric pressure to temperature transfer function (TF) as a function of frequency from 8 × 10-7 to 8 × 10-4 Hz. Here, we use this TF to calculate the expected PIT variations, which, after being subtracted from the observed time-series, provide residual temperature time-series. We calculated such temperature residuals in four natural caves in France: Esparros, Aven d'Orgnac, Pech Merle and Chauvet-Pont d'Arc Caves, the last two containing unique prehistoric wall paintings. Temperature signals, as small as a few 10-3 °C, due to human presence, are then conspicuous, with evidence of relaxation longer than several days and long-term cumulative effects. In addition, we observe temperature signals suggesting non-stationary states characterized by several processes which are not necessarily easy to separate, such as transient air currents, due to barometric winds or locally semi-confined convection cells, transient infiltration, or energy dissipation by evaporation-condensation at the rock surface. This background thermal agitation displays a scale-free amplitude spectrum, from 2 × 10-5 to 4 × 10-4 Hz, of the form f-α, with α varying from 0.1 to 0.6 depending on the site. Furthermore, at the Chauvet Cave, a weak but unambiguous peak emerges during some months at a period of about 82.2 ± 0.8 minutes, suggesting a Helmholtz-type resonance. Small but significant temperature signals are therefore detected in underground cavities once the effect of atmospheric pressure variations is corrected for. These signals reveal subtle coupled processes whose knowledge is essential to evaluate preservation strategies and to establish conditions for resilience of underground systems under artificial or natural influence including climate change.
(Geosystems and Geoenvironment. vol. 2, 20/06/2026)
IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS
The effects of artificial light at night on behavioral rhythm and related gene expression are wavelength dependent in the oyster Crassostrea gigas
Artificial light at night (ALAN) constitutes a growing threat to coastal ecosystems by altering natural light cycles, which could impair organisms’ biological rhythms, with resulting physiological and ecological consequences. Coastal ecosystems are strongly exposed to ALAN, but its effects on coastal organisms are poorly studied. Besides ALAN’s intensity, ALAN’s quality exposure may change the impacts on organisms. This study aims to characterize the effects of different ALAN’s spectral compositions (monochromatic wavelength lights in red (peak at 626 nm), green (peak at 515 nm), blue (peak at 467 nm), and white (410–680 nm) light) at low and realistic intensity (1 lx) on the oyster Crassostrea gigas daily rhythm. Results reveal that all ALAN’s treatments affect the oysters’ daily valve activity rhythm in different manners and the overall expression of the 13 studied genes. Eight of these genes are involved in the oyster’s circadian clock, 2 are clock-associated genes, and 3 are light perception genes. The blue light has the most important effects on oysters’ valve behavior and clock and clock-associated gene expression. Interestingly, red and green lights also show significant impacts on the daily rhythm, while the lowest impacts are shown with the green light. Finally, ALAN white light shows the same impact as the blue one in terms of loss of rhythmic oysters’ percentage, but the chronobiological parameters of the remaining rhythmic oysters are less disrupted than when exposed to each of the monochromatic light’s treatments alone. We conclude that ALAN’s spectral composition does influence its effect on oysters’ daily rhythm, which could give clues to limit physiological and ecological impacts on coastal environments.
(Environmental Science and Pollution Research. vol. 30, n° 0944-1344, pp. 120375-120386, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Image analysis and benthic ecology: Proceedings to analyze in situ long‐term image series
Long time series of underwater images have become a tool widely used within the benthic ecology research community. The development of new acquisition systems with bigger storing capacities lead researchers and scientists to deploy them for longer periods resulting in large amounts of data. This paper focuses on the first steps of analyzing large numbers of underwater images, which involves assessing the amount of valid data while assuming no technical problems. The question here addressed is how many of the in situ images can reliably be really used for benthic ecology purposes. To answer this question, we propose a method to eliminate nonvalid images and use it with four different sets of time-lapsed images acquired for long periods ranging from 73 to 371 ds in a row. The results show that elimination of between 8% and 22% of the images is possible depending on the data set. The main advantage of the method is easing and accelerating automation of subsequent analysis.
(Limnology and Oceanography: Methods. vol. 21, n° 1541-5856, pp. 169-177, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IO-PAN, PAN
Deformation bands and alteration in porous glass-rich volcaniclastics: Insights from Milos, Greece
Deformation bands in porous volcaniclastics are little studied structural heterogeneities despite their relevance for constraining the modalities of deformation development and related fluid-rock interactions in volcanic areas. We document a dense network of normal-sense Deformation Bands (Normal-sense Compactional Shear Bands (NCSBs) affecting upper Pliocene felsic glassy tuffites in Milos, Greece. NCSBs probably formed between 300 and 500 m of burial depth, in response to NE-SW directed extension which is related to volcanic rift development in the area. They accommodate mm-to m-shear-offsets, trend either N105 ± 10° or N070 ± 10°, and show mutual cross-cutting relations. The NCSB fault rock is made of ultracataclasite in which the cataclastic mechanisms have affected both the mineral fraction and the volcanic glass. Minerals are fractured along their cleavages whereas pumices are interestingly fractured along their vesicles. The development of chemical alteration (dissolution and cementation) essentially into the ultracataclasite is expressed through glass-hosted corrosion gulfs and smectites filling the intergranular porosity. These observations support that NCSBs preferentially retained water, have been the seat of greater fluid flow, and are the locus of ongoing phyllosilicate self-sealing in the vadose zone. A significant decrease (up to one order of magnitude) in porosity is measured within the studied NCSBs
(Journal of Structural Geology. vol. 177, n° 0191-8141, pp. 104982, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, I2M-BX, UB, CNRS, INRAE, INSU - CNRS, CNRS, UA, UM, UiB, UiB
Morphodynamics of wave-dominated beaches
Abstract Wave-dominated sandy beaches are highly valued by societies and are amongst the world’s most energetic and dynamic environments. On wave-dominated beaches with unlimited sand supply and limited influence of tide and geology, beach change has long been conceptualised in the morphodynamic framework of Wright and Short (1984). Such framework describes the occurrence of beach types based on wave conditions and sediment characteristics across the complete reflective–dissipative spectrum. Building on theoretical work, field/laboratory measurements and monitoring programmes, the physical mechanisms underpinning this morphodynamic framework have been progressively unravelled. Cross-shore morphological changes are primarily controlled by equilibrium and beach memory principles with below (above) average wave conditions driving down-state (up-state) transitions associated with onshore (offshore) sediment transport. Such cross-shore behaviour mostly reflects the imbalance between the onshore-directed sediment transport driven by wave nonlinearities and the offshore-directed sediment transport driven by the undertow. Self-organised morphological instabilities resulting from different positive feedback mechanisms are primarily responsible for alongshore morphological variability and the generation of rhythmic morphological features, such as crescentic bars, rip channels and beach cusps. Critically, wave climate and changes in wave regimes are key in driving the coupled cross-shore and longshore behaviour that ultimately explains modal beach state and frequency-response characteristics of beach morphological time series.
(Cambridge Prisms: Coastal Futures. vol. 1, pp. e1, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Holocene hydroclimate variability along the Southern Patagonian margin (Chile) reconstructed from Cueva Chica speleothems
Patagonia is ideally situated to reconstruct past migrations of the southern westerly winds (SWWs) due to itssoutherly maritime location. The SWWs are an important driver of Southern Ocean upwelling and their strengthand latitudinal position changed during the Holocene, leading thus to different responses of the vegetation topast climate changes along the Chilean continental margin. A new speleothem record from Cueva Chica (51◦S) isinvestigated to reconstruct past climatic changes throughout the Holocene in conjunction with other marine andpaleoenvironmental records of the region and better constrain the regional paleoclimatic evolutions of SWWs.Samples comprising both a flowstone core and a stalagmite were radiometrically dated (U–Th & 14C) toconstruct age-depth models for the highly-resolved proxy profiles (δ13C, δ18O, chemical composition). TheCueva Chica record provides a highly-resolved isotopic and elemental curves for the last 12 ka, albeit with ahiatus from 5.8 to 4 ka BP. The multi-proxy analysis suggests three climatic regimes throughout the Holocene inSouthern Patagonia: i) an early Holocene wet period (with the exception of two dry excursions at 10.5 ka and 8.5ka BP), ii) a mid-Holocene dry period and iii), a return to generally wet conditions over the late Holocene. Theglobal drivers for these tri-phased climatic regimes are likely related to oceanic and South polar feedbacks. Theearly Holocene was the warmest period and might be attributable to changes in global ocean circulation whichinvolved a rise in air T◦ and a strength in SWW from 50◦S, and therefore higher precipitations over landmass.After 9 ka BP, an intensified deglaciation dynamic along the Antarctic Peninsula is concordant with increasingsummer insolation in the Southern hemisphere, leading to a poleward shift of the SWWs in response to globalwarming and thus to a reduction in moisture supply from the Pacific onto the Patagonian shore. After 5 ka BP, agradual SST decline is consistent with an equatorward shift of the SWWs in response to a cooling Southernhemisphere. The SWW storm tracks extended to lower latitudes, inducing a return to wetter conditions withhighly variable moisture patterns along the Patagonian landmass. Clumped isotope (Δ 47) analyses at lowerresolution reflect the degree of kinetic isotope fractionation at the time of carbonate deposition, especially duringthe dry interval around 8.5–5.5 ka BP. Reduced kinetic isotope fractionation is observed since at least 2.6 ka BP,a period marked by (slightly) wetter conditions.
(Global and Planetary Change. vol. 222, n° 0921-8181, pp. 104050, 20/06/2026)
IDEES, UNICAEN, NU, ULH, NU, UNIROUEN, NU, CNRS, IRIHS, UNIROUEN, NU, VUB, EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, VUB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MPIC, GFZ, UBA, UMAG
Settling dynamics of cohesive sediments in a highly turbid tidal river
An optical settling column was used in the Garonne Tidal River to estimate the settling velocity of suspended matter in surface waters over a period characterized by contrasting hydrological conditions. A time and space variability of settling velocity was observed during this study. The settling velocities of surface suspended matter ranged from 0.018 to 0.268 mm.s −1 , and the median diameter of dispersed particles varied from 4.74 to 14.38 µm. The data revealed the physical processes influencing the sediment settling dynamics throughout different time scales in a highly turbid tidal river. On tidal and fortnightly time scales, resuspension, deposition and advection mechanisms were the major drivers of the settling velocity variability, while it is likely that the estuarine turbidity maxima (ETM) was responsible for seasonal variations. The findings of this work suggest that in tidal rivers, salinity is too low to promote flocculation, whereas ETM can play a key role in enhancing this process. The stronger variability in settling velocity occurs on a tidal timescale, with median values up to four times higher at the end of the ebb tide than at high water. These variations cannot be correlated to salinity or sediment concentration. On a seasonal timescale, flocculation appears to be strongly correlated with the presence of the ETM and associated fluid mud layer. A simple correlation based on tidal variations seems to be a better predictor than the relationships based on the sediment concentration.
(Marine Geology. vol. 457, n° 0025-3227, pp. 106995, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IGE, IRD, INSU - CNRS, CNRS, INRAE, Fédération OSUG, UGA, Grenoble INP, UGA
Storm response and multi-annual recovery of eight coastal dunes spread along the Atlantic coast of Europe
Coastal dunes are natural barriers against coastal flooding, and represent large sources of sediment to mitigate coastal erosion, besides being a natural habitat for many living beings. Yet, these complex environments are threatened by sea level rise and possibly enhanced storminess in the future. Most of the studies on coastal dune erosion and recovery from storms are either site specific or focus on a short-time scale, from months to a couple of years. Here, airborne LiDAR data collected from 2011 to 2020 at eight diverse coastal dunes, spread from NW England to SW France, were analysed to study their response, and recovery from the most energetic extreme storms wave conditions since at least 1948. Results show that the 2013/14 winter was the first or second largest erosive event (from −14 to −290 m3/m dune volume loss) from 2011 to 2020 at all sites. The magnitude of storm-driven sand volume loss was mainly controlled by dune face slope (r = 0.84). Dunes with steeper pre-storm slopes lost the largest volumes of sand. At a dune scale, the scarping height was also well correlated to the dune face slope at sites where storm response was characterized by limited alongshore variability. Dune recovery was site specific (no recovery, partial, complete, excess), with dunes that either progressively returned to their pre-storm morphology or were reshaped while recovering. Percentage of dune sand volume recovery was well correlated to the local and long-term satellite-derived shoreline change rate computed from 1984 to 2021 (r = 0.81), suggesting that dune recovery is mainly controlled by the local coastal sediment budget. The rate of dune crest elevation increase (from 4.2 to 12 cm/year) at four of the study sites from 2011 to 2020, largely exceeded sea level rise rate over the past decade (3.3 ± 0.7 mm/year). These results provide key insight into the contrasting resilience of some of the most exposed coastal dunes along the Atlantic coast that recover at different rates following the same sequence of extreme storms
(Geomorphology. vol. 435, n° 0169-555X, pp. 108735, 20/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS