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Evaluating Quercus pollen as a valuable archive of past UV-B levels in the Central Mediterranean: Insights from comparative infrared spectroscopy analyses
No full textInternational audienceThe relative abundance of ultraviolet-absorbing compounds (UACs) in pollen and spore exine increases with prolonged and higher exposure to ultraviolet B (UV-B) radiation. This relationship has been extensively studied via transmission Fourier-transform infrared microspectroscopy (transmission micro-FTIR), primarily in Lycopodium spores and airborne Pinus pollen. However, traditional transmission micro-FTIR methods are prone to infrared light scattering and interference, resulting in spectral deformations and reduced reproducibility. Additionally, bisaccate pollen, like Pinus, can travel long distances and may not accurately reflect local UV-B levels. This study compares transmission and attenuated total reflection (ATR) micro-FTIR methods to assess their reproducibility and investigates Quercus pollen as a potential local UV-B proxy in the Central Mediterranean. Samples containing fresh (in situ), trapped (in mosses), and fossilized (from Holocene sediments) pollen grains were subjected to various chemical treatments, after which the macromolecular composition of single and clustered grains was characterized. Results show that ATR micro-FTIR yields significantly more reproducible data than transmission micro-FTIR, demonstrating the suitability of this method for systematic chemo-palynological studies. Quercus ilex pollen consistently display UAC-related absorption bands across modern and fossil samples, and treatment with hydrochloric acid, hydrofluoric acid, and sodium hydroxide does not significantly alter these signatures. A comparison with fresh and trapped Q. cerris and Q. pubescens pollen further supports these findings. These results suggest that relative UAC concentrations in modern and fossil Quercus exine likely reflect accumulated UV-B dosage, pinpointing Quercus pollen as a valuable local UV-B proxy for reconstructing past UV-B levels in the Central Mediterranea
Evidence of Fukushima fallout in the area affected by wildfires in Kamaishi (Iwate Prefecture, Tohoku Region, Japan): Implications for future environmental research using radionuclide tracers
No full textInternational audienceSignificant deposition of radiocesium including 134Cs and 137Cs occurred in March 2011 following the Fukushima nuclear accident across vast regions of Northeastern Japan. However, as most studies focused on fallout that took place in the Fukushima Prefecture, much less information is available on the situation that prevails further to the North, in other parts of the Tohoku Region of Japan. In this context, the current research investigated the occurrence of fallout radionuclides (including natural 210 Pb-xs as well as artificial 134Cs and 137Cs) in burned and unburned soil profiles as well as in a range of surface soil and sediment samples collected in the region of Kamaishi (Iwate Prefecture, Tohoku Region, Japan) affected by wildfires in 2017. Results show that 210Pb-xs and 137Cs may be used as tracers of sediment sources across landscapes affected by wildfires in this region. Furthermore, the soil profile analysis demonstrated that all analysed fallout radionuclides were found enriched in the burned vs. unburned profiles, due to the incorporation of radionuclides trapped by vegetation into the ash after the fire. The detection of 134 Cs in the uppermost 0-5 cm depth layer in all investigated soil profiles also allowed to demonstrate the occurrence of significant Fukushima fallout of 134Cs and 137Cs in this region (roughly of the same order of magnitude as the fallout associated with the nuclear atmospheric tests in the 1960s). In the future, both sources of fallout should be considered to provide relevant interpretations when examining radionuclide data found in environmental samples collected in vast regions of Northeastern Japan. The analysis of 134Cs should also be encouraged to document the sources of fallout in these regions as long as this short-lived radionuclide remains detectable (i.e., theoretically by 2031)
Impact of Strain on Carbonaceous Matter Crystallinity: Insights from Raman Spectroscopy and microstructural analysis of strain gradients from exhumed accretionary complexes
No full textInternational audienceHighlights (to remove in a single file after correction)• RSCM parameter R1 reflects CM maturity evolution • CM maturity is increased in ductile and brittle high-strain zones• In shear zones, strain is the main cause of increased CM maturity• In breccia zone frictional heating cannot be ruled out.• RSCM signal stems from ~50-100nm particles distributed throughout the rock 0.</div
Across ancient oceans: Eocene dispersal routes of Asian terrestrial mammals to Europe, Afro-Arabia and South America
No full textInternational audienceDuring the middle and late Eocene, Asian terrestrial mammals dispersed to Europe, while primates and rodents dispersed across the 500-to-2000 km wide Neotethys Ocean and the 1500-to-2000 km wide Atlantic Ocean to colonize Afro-Arabia and South America. This study explores how these mammals have achieved such remarkable and enigmatic dispersals. We present high-resolution paleogeographic models for the middle to late Eocene based on updated plate kinematic reconstructions, paleo-bathymetry and paleo-topography data. With this, we evaluate landmass configurations and connectivity that may have facilitated faunal exchanges from Asia toward Europe, Afro-Arabia, and South America and discuss dispersal mechanisms between these biogeographic provinces. Our reconstructions reveal that during the Bartonian (~40–38 Ma), an overland dispersal corridor between Asia and Balkanatolia became available to terrestrial mammals and acted as a pivotal pathway for Asian faunas dispersing toward western Europe and Afro-Arabia. We identified two Balkanatolian island-hopping routes across the Western Neotethys potentially enabling the dispersal of small-bodied Asian primates, rodents and artiodactyls to Afro-Arabia. Alternatively, these taxa may have rafted across the Central Neotethys. By ~34 Ma, Balkanatolia fully connected with Western Europe, opening a southern “Grande Coupure” route for Asian faunas. In the Atlantic, we identify long-distance rafting as the most plausible mechanism for the 40–34 Ma transoceanic dispersal of the Asian-originated primates and rodents from Afro-Arabia to South America despite the likely presence of sparse islands along the Walvis Ridge and the Rio Grande Rise
Mesozoic Pb-Zn hydrothermal veins in the Jebilet, Morocco: Constraints from mineralogy, fluid inclusions and stable isotope data
No full textInternational audienceThe Sarhlef, Bir N'Has, Bramram, and Bamega Pb-Zn vein deposits are hosted within the Carboniferous schistose series of the Jebilet Massif, Morocco. All four deposits share similar structural pattern and mineralization history. Early Variscan barren N-S quartz veins (Stage 1) crosscut the schist and are followed by E-W quartz-carbonate veins bearing Pb-Zn-(Cu) mineralization (Stage 2). Mineral paragenesis (stage 1) begins with pyrite, followed by minor arsenides (stage 1), associated with metamorphic carbonic to aqueous-carbonic fluids (7-18.4 wt% NaCl equivalent; 250° to >410°C), attributed to Variscan events in the Jebilet. The Pb-Zn ore stage (stage 2) comprises two polyphase episodes. The first episode begins with the deposition of carbonates (siderite-dolomite), followed by quartz (geodic comb then saccharoidal). The second episode is marked by ore deposition, with Fe-dolomite and minor calcite as gangue minerals. Barite crystallized locally (stage 2), followed by Fe-rich sphalerite, galena, and chalcopyrite. The ore stage is associated with aqueous brines (ore brines: ~9-27 wt% NaCl equivalent; 69°-212°C). Ore precipitation was likely driven by cooling and dilution of brines through mixing with recharge fluids.Stable carbon and oxygen isotope data from carbonates (stage 2) suggest that carbon was derived from fluids that interacted with organic-rich schist. The oxygen and hydrogen isotope compositions of the ore brines (δ¹⁸O: -1.8‰ to +2.4‰ ± 0.1‰ V-SMOW; δD: -60.4‰ V-SMOW) are typical of general basinal brines. Sulfur isotopes from galena and sphalerite (+3.1‰ to +12.9‰) suggest a sulfur source from Triassic evaporated seawater/Triassic evaporites for stage 2 (ore stage).The ore veins that crosscut post-Variscan microdiorite dikes are at least Mesozoic. We propose that the ore-forming brines originated from Triassic sedimentary and evaporitic sequences within Atlasic basins. Structural traps for Pb-Zn mineralization likely formed during Mesozoic extensional tectonics associated with the early rifting of the Atlantic Ocean.The Pb-Zn ore stage (stage 2) is genetically distinct from the earlier Variscan magmatic and metamorphic events (i.e. stage 1).</p
Une modernisation longtemps ajournée : la construction du dock-entrepôt bordelais au XIXe siècle
No full textInternational audienc
Extreme Mediterranean rainfall impact on sedimentary routing systems: what can we learn from Storm Alex using in situ detrital 10Be?
No full textInternational audienceUnderstanding how extreme meteorological events influence sediment transport is critical for predicting landscape evolution under a changing climate. Detrital cosmogenic 10Be can provide insights into sediment dynamics following extreme rainfall, but high-resolution datasets tracking 10Be variations before and after a storm, alongside long-term records, remain rare.The Var catchment (French Southern Alps) presents a unique case study, as its 10Be signal was well-documented before the October 2020 Storm Alex (>500 mm of rainfall/24 h), which triggered flash floods, mobilized large sediment volumes, and formed a 10 km-long sediment plume in the Mediterranean Sea. We compare 10Be concentrations in river sediments collected pre-storm (2016–2018), and at +7 days, +21 days, +4 months, and +7 months post-storm. We also use a historical offshore sample and contextualize these results with a 75 ka-long 10Be record from deep-sea sediment cores.At the Var outlet, 10Be concentrations initially increased by ∼25 % at +7 and +21 days, attributed to the mobilization of 10Be-rich sediments from the upstream Var and Tinée sub-catchments. Concentrations returned to pre-storm levels within four months, primarily due to dilution with 10Be-poor sediments from the Vésubie sub-catchment fluvioglacial terraces. While short-term 10Be fluctuations at the Var outlet reflect complex sediment sourcing, our comparison with the 0–75 ka record confirms that major glaciation events and potential anthropic influences remain distinguishable, demonstrating that 10Be is a robust proxy of denudation changes, even when extreme events are involved
Ionomic exploration of the geographical and geological origins of mountain pasture cow milks in the French Massif central
No full textInternational audienceIonomic profiling was used to characterize the multielemental composition of raw cow milk during mountain pasture in the French Massif central, and to assess its potential as an indicator of geographical and geological origin. Eighteen milk samples were analyzed by ICP-MS from farms in three mountain sectors (Sancy, Cantal, Other), located on volcanic and non-volcanic sites. Of the 61 analyzed elements, 32 were consistently quantified, several of them (Pd, Zr and Nb) being reported for the first time in milk. Multivariate statistical analyses permitted to differentiate geographical provenances and geological conditions based on specific sets of elements. Pearson correlations analyses revealed geology-driven soil-to-milk transfer processes, exemplified by the element pairs -(Rb,Te) and (Sr,Pd), underscoring the influence of terroir on milk composition. Further research should focus on the soil-plant-milk continuum to better understand these geochemical pathways and to support the concept of milk terroir for the PDO cheese sector
Lithospheric models supported by the Caribbean and Levant examples help rethink transpression at plate boundaries
No full textInternational audienceStrike-slip restraining bends, such as the Levant Fault, belonging to push-up systems and the Jamaican fault network, belonging to duplex systems, display a diversity of fault geometries and deformation patterns that reflect distinct modes of lithospheric-scale strain localization. To investigate the origin of this variability, we develop 3D numerical models of transpressional strike-slip systems using heterogeneous simple shear boundary conditions and thermally-dependent, non-linear rheology. Unlike classical analog or numerical models that impose velocity discontinuities, our approach allows spontaneous fault localization that naturally generates transpression. We systematically explore how the position and geometry of inherited weak zones influence fault development. We show that three distinct strike-slip systems emerge: (1) push-up systems with a single strike-slip fault and outward-propagating thrusts; (2) duplex systems with interacting parallel faults connected by P-shears; and (3) systems of non-interacting parallel faults. These results highlight spontaneous strike-slip localization and how initial heterogeneities control formation and evolution of long-term lithospheric deformation
