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A Fluvio‐Lacustrine Environment Preserved in the Jezero Crater Inlet Channel, Neretva Vallis, Mars
No full textInternational audienceMartian fluvial valleys provide evidence for the surface flow of liquid water, making them a key target for rover-based investigations of ancient habitability. The Mars 2020 Perseverance rover spent ∼85 sols exploring the Bright Angel formation, exposed across the floor of Neretva Vallis: the western inlet channel of Jezero crater. This study documents the sedimentology and stratigraphy of the Bright Angel formation to reconstruct its depositional setting. The unit preserves a concave-up bedding structure consistent with a young channel-fill deposit, rather than an older unit exposed by incision of Neretva Vallis. The lower stratigraphy displays a fining-up sequence from coarse-grained sediments up to pebble-conglomerates (the Tuff Cliff member) into a ≥10-m-thick succession of laminated mudstone (the Walhalla Glades member), interpreted as a transgressive sequence recording the onset of lacustrine conditions in Neretva Vallis. Lenses of matrix-supported granule-conglomerate adjacent to the valley wall (the Fern Glen Rapids member) may preserve locally derived debris flows entering the lake. These are overlain by a polymict, matrix-supported, boulder-conglomerate (the Mount Spoonhead member), interpreted as a high-energy debrite derived from the watershed. The sequence is capped by cross-stratified sediments (the Serpentine Rapids member), preserving lake margin deposits. The Bright Angel lacustrine sequence occurs ∼10–50 m higher in elevation than the lake level anticipated for the Jezero western delta, requiring an additional period of lacustrine activity. The structure and spatial distribution of the unit leads us to propose that a late-stage blockage of Neretva Vallis may have facilitated the formation of a perched, valley-confined lake upstream
A window on the amalgamation of Western Gondwana: Geological history of the Ouaddaï massif (E. Chad)
No full textInternational audienceThe Saharan metacraton was assembled during pre-Neoproterozoic to Neoproterozoic times and was strongly remobilised during the Pan African orogeny. The Ouaddaï massif in eastern Chad represents the core of the Saharan metacraton, yet its geological history remains poorly documented. In this study, we combine of field observations, petrological analysis of metamorphic rocks, and geochemical and geochronological constraints to reconstruct the tectono-metamorphic evolution of the Ouaddaï massif. The study area is dominated by collision-related plutonic rocks and migmatitic gneisses, within which inliers of older basement occur. Geochemical data indicate a transition from active-margin to collisional magmatism, with a compositional evolution from diorite to granite. This suite is cross-cut by syenogranites and alkaline granites with shoshonitic affinities, interpreted as post-collisional granitoids derived from tonalitic rocks to sedimentary protoliths. Geochronological data (U-Pb on zircon and monazite) point to a ca. 1000 Ma age for orthogneisses inliers. Granitoids of the Ouaddaï massif record emplacement ages from 620 to 590 Ma, coeval with high-temperature metamorphism characterized by peak pressure–temperature conditions of 1.2 GPa and 850 °C (mafic granulite) and around 0.8 GPa and 700 °C (sillimanite-garnet bearing migmatites). Integrating our new results with regional data, we discuss the existence and geodynamic evolution of the Saharan Metacraton. Our findings emphasize the significance of the Saharan Metacraton as a key region for understanding the extensive reworking of cratonic lithosphere during both a Tonian magmatic phase prior and the assembly of Gondwan
Modélisation hydrologique et changements climatiques. Méthodologie et applications
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Prioritising research on endocrine disruption in the marine environment: a global perspective
No full textInternational audienceA healthy ocean is a crucial life support system that regulates the global climate, is a source of oxygen and supports major economic activities. A vast and understudied biodiversity from micro‐ to macro‐organisms is integral to ocean health. However, the impact of pollutants that reach the ocean daily is understudied for marine taxa, which are also absent or poorly represented in regulatory test guidelines for chemical hazard assessment. Inspired by the United Nations Decade of Ocean Science, which aims to reverse the decline in ocean health, this communication calls for global coordination in building resources for studying the effects of marine pollution. The bibliographic analysis, a collective product of scientists from diverse backgrounds, focused on endocrine‐disrupting chemicals (EDCs). In this review, we ( i ) critically analyse the literature on endocrine signalling pathways and high‐level physiological impacts of EDCs across 20 representative marine taxa; ( ii ) identify knowledge and regulatory gaps; ( iii ) apply bioinformatics approaches to marine species genomic resources, with relevance for predictions of susceptibility; and ( iv ) provide recommendations of priority actions for different stakeholders. We reveal that the scientific literature on EDCs is biased towards terrestrial and/or freshwater organisms, is limited to a handful of animal taxa, and marine organisms are dramatically underrepresented. Our bibliographic analysis also confirmed that only a small number of (neuro) endocrine pathways are covered for all animals, whilst basic knowledge on endocrine systems/endocrine disruption for most marine invertebrate phyla is minimal. Despite significant gaps in genomic resources for marine animals, endocrine‐related protein conservation was evident across more than 500 species from diverse marine taxa, highlighting that they are at risk from EDCs. Despite recent technological advances, translation of existing knowledge into international regulatory test guidelines for chemical hazard assessment and monitoring programs is limited. Furthermore, the current understanding is confounded in part by transposing vertebrate endocrinology onto non‐vertebrate taxa. In this context, specific recommendations are provided for all stakeholders, including academia (e.g. to expand knowledge across metazoan taxa and endocrine targets and translate it to New Approach Methodologies and Adverse Outcome Pathways; to increase and improve tools for comparative species‐sensitivity distributions and cross‐species extrapolations), regulators (e.g. increase awareness of specific risks for the marine environment, prioritise international standardisation of testing methods for marine species and request evidence for absence of endocrine disruption in marine phyla), policy makers (e.g. implement sustained, long‐term international marine monitoring programs and increase global co‐operation) and the public or non‐governmental organisations (e.g. foster public engagement and behaviours that prevent marine chemical pollution; promote citizen science activities; and drive political actions towards protective and restorative marine policies). We hope that this and past reviews can contribute towards meeting ambitious international plans for marine water quality assurance, mitigation of marine pollution impacts and protection of marine biodiversity. The importance of marine biodiversity for climate change mitigation, food security and sustainable ecosystem services calls for urgent, cooperative action
The Tianlai-WIYN North Celestial Cap Redshift Survey
No full textInternational audienceWe present the results of a small, low redshift spectroscopic survey of galaxies within 3 degrees of the North Celestial Pole (NCP) selected using V-band photometry obtained from the North Celestial Cap Survey (NCCS) (Gorbikov & Brosch 2014). The purpose of the current survey is to create a redshift space template for 21 cm emission from neutral hydrogen with which to correlate radio line intensity observations by the Tianlai dish and cylinder interferometers. A total of 898 redshifts were obtained from the 2102 extended objects in the NCCS with m_V < 19 in the survey area. After accounting for extinction, the survey geometry and selection effects, the number density and clustering pattern of galaxies in the redshift catalog are consistent with other low redshift surveys. We were also able to identify 11 galaxy cluster candidates from this redshift catalog
Platinum and Rare Earth Elements distribution in costal sediments from French western Mediterranean Sea
No full textInternational audienc
Spatial variability in nutrient and organic matter concentrations during hydrological fragmentation of an intermittent temperate catchment
No full textThis research was funded by the AQUA division of the Institut national de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), the Brittany region, and the Observatoire des sciences de l’environnement de Rennes (OSERen).International audienceIntermittent and ephemeral streams are watercourses that cease to flow and/or dry up during part of the year. Their seasonal drying is sometimes preceded by a stream fragmentation phase with formation of isolated pools where the biogeochemistry differs from that of perennial reaches. Our objective was to analyse how hydrological fragmentation alters the spatial variability in dissolved nutrient and organic matter concentrations in a temperate-oceanic and agriculture-impacted headwater stream, where nutrient loadings are high. We conducted repeated synoptic sampling campaigns at high spatial resolution (150–200 m) along the stream network of the Naizin catchment (7 km2) during the spring–summer-fall of 2023. We sampled 38 sites and analysed dissolved organic carbon (DOC) concentrations and fluorescence properties, dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) concentrations, during four sampling campaigns: stream recession, early and late fragmentation and reconnection. Our results showed an increase in the spatial variability of concentrations, with monotonic longitudinal gradients along the stream disappearing during hydrological fragmentation. Both DOC and SRP concentrations were higher in isolated pools than in flowing reaches, while DIN concentration was lower. The chemical composition of DIN and DOC also changed with stream fragmentation, with increasing proportions of nitrite and ammonium in DIN and humic-like organic matter in DOC. These results suggest that the main controlling processes in the isolated pools were streambed mobilisation of SRP and DOC, along with denitrification under anoxic conditions. We expect the observed spatio-temporal patterns in nutrient and DOC concentrations to become more widespread in the future as intermittent streams will become more frequent owing to climate change
Chemical contamination of black soldier fly larvae raised on EU-authorized or unauthorized substrate
No full textInternational audienceBlack soldier fly larvae (BSFL), Hermetia illucens, can efficiently convert biowaste into high-quality protein for the feed industry. However, biowaste can contain several chemical hazards and their fate in BSFL remain largely unexplored, even though they can pose a threat for both the insect sector and the higher levels of the trophic chain. The purpose of this study was to evaluate the chemical contamination of BSFL reared on authorized biowaste (wheat bran, carrots, apricots, salad) or unauthorized biowaste in the EU (school canteen and supermarket biowaste). PFAS were not quantifiable in the substrates in contrast with persistent organic pollutants, pesticides and trace metal elements. The chlormequat pesticide was the only pesticide quantified in BSFL (15 µg/kg), slightly above the maximum residue limit in the EU for feed (10 µg/kg). Concentrations of PCBs and PCDD/Fs in BSFL were below the maximum limit (ML) but bioaccumulation factors up to 5 were obtained. As and Cd were highly bioaccumulated with concentrations approaching the ML for Cd (0.5 mg/kg) or 8 times below for As (ML = 2 mg/kg). The unauthorized substrate samples tested led to higher chemical safety risks in BSFL, with 10 times higher concentrations of As than in BSFL reared on authorized substrates and the presence of PCDD/Fs and PCBs. The concentrations of chemical contaminants in animal products consumed by humans such as eggs were estimated using transfer models when animals were fed with BSFL reared on unauthorized substrates. The concentrations were below the maximum limits in all cases
Influence of precursor molecular weight on swelling and elastic modulus of cross-linked PDMS films
No full textInternational audienceThe influence of precursor molecular weight on cross-linked poly(dimethylsiloxane) (PDMS) thin films was studied at constant cross-linker ratio. Increasing molecular weight lowers cross-link density, enhances swelling, and reduces elastic modulus
Extreme flood deposits in the Roya Valley during the Holocene: characterisation and recurrence intervals
No full textInternational audienceFloods are among the costliest natural disasters, causing extensive damage and fatalities worldwide. Mountainous regions of the Mediterranean Alps are highly vulnerable to extreme hydrological events, whose frequency is increasing in the context of climate change favouring convective storms. In October 2020, the Roya valley was struck by an extreme hydrological event. The amount of rainfall (return period >1000yr) and discharge (>100yr), triggered major geomorphological changes, including subsantial channel widening, slope destabilisation and extensive bank erosion. This study provides unprecedented sedimentological data on torrential dynamics in the Roya Valley, based on 14C and OSL dating of newly exposed flooding deposits following Storm Alex. Five clusters of preserved fluvial and torrential deposits ranging from the Younger Dryas–Holocene transition to the Little Ice Age are identified. These preservation clusters correspond to periods of wetter condition and anthropogenic influence. By combining sedimentological analyses with documented pollen and sediments records from lakes in the Mercantour massif, as well as historical archives, this study presents one of the first flood-frequency reconstructions for a Mediterranean Alpine catchment over a multi-millennial timescale. Past flooding events (on centennial to millennial scales) leave distinctive sedimentary signatures, characterised by thick deposits and the mobilisation of coarse particles, before being reworked within the broader autogenic dynamics of the river system. Reconstructing the frequency and occurrence of past extreme flood events provides key insights into the conditions under which such events occurr, and offers valuable information for the development of flood-risk scenarios, particularly in mountainous areas that are among the most affected by contemporary climate change