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Glacial/interglacial transitions in mountainous areas are marked by significant glacier retreat from forelands to inner massifs, resulting in large-scale and ephemeral lake formation that are subsequently filled (or not) by sediment transfer during lateglacial to postglacial times. When valley paleo-infills are preserved, they form precious archives to investigate (1) Alpine erosion dynamics and paleo-environmental conditions during key transition periods from full glacial stages to interglacials, and (2) glacial erosion patterns during susbequent glaciation.In this contribution, we investigate such sedimentary deposits (locally called as "banquettes") in the French western Alps, and more precisely along the Isère valley and Val du Bourget. Previous research have attributed these deposits to the Riss – Würm transition due to their position under a basal compact till and to the MIS 6/5 transition up to early MIS 4 from palynological constraints, although no absolute ages has been available so far. Based on existing mapping of their spatial distribution and stratigraphic reconstructions, we sampled coarse-sand and sandy-gravel layers within these deposits for constraining both sediment deposition time (OSL dating) and provenance (glacial/postglacial origin, using terrestrial cosmogenic nuclide TCN 10Be in quartz). In addition, their spatial distribution provides estimates of maximum glacial erosion during the last glacial cycle, which can be subsequently used as spatial constraints for ice model predictions.Our results confirm deposition times of these sedimentary units at the MIS 6/5 transition, with dating constraints from the late MIS 6 (ca. 145 ka) to the early MIS 5 (Eemien, 115-130 ka) for sandy layers. Upper sandy-gravel layers have younger deposition ages of ca. 80 ka, illustrating sediment fluxes at the transition from late MIS 5 to early MIS 4. We compare this temporal sequence to more recent sediment infills of the Isère valley (14C and OSL dating) during the Lateglacial to Holocene (MIS 2/1) transition. TCN data from sand samples also illustrate the sharp transition from full glacial to interglacial conditions, with a significant increase in 10Be concentrations from Lateglacial to post-glacial sediments. We propose that the observed signal can reflect changes in erosion rates, but also in glacier expansion or in paleo-environmental conditions, with export of stored subglacial sediments as well as the re-establishment of sediment/soil production and transfer along the catchment routing system following glacier retreat.

International audience; This study tests the application of combined detrital apatite fission track (AFT) and U-Pb dating to infer both glacial erosion spatial patterns and long-term rock cooling histories in Alpine mountainous settings. We have dated 716 detrital apatite grains from glacial sediments collected in the Maurienne and Arve valleys (Western European Alps, France) from moraine deposits corresponding to different stages of glacial retreat since the Last Glacial Maximum (LGM, ca. 24-21 ka).The Maurienne valley crosses the internal and external Alps, which exhibit contrasting in-situ AFT and U-Pb ages. Here, we present the measured distribution of both detrital AFT and U-Pb ages at 6 locations along the valley, with catchment elevations ranging from 390 to 1740 m. We show that during glacial retreat, erosion is mainly concentrated in the downstream part of the glacier, near the sampled moraine deposits. This inference suggests that during glacial retreat, glacial erosion is more effective below the ELA (Equilibrium Line Altitude) and specifically close to the glacier front, in areas where ice flow velocity is high and subglacial water is abundant, as predicted by ice-dynamics reconstructions in the European Alps over the last 20 ka.In the Arve valley, previous studies showed that in situ AFT ages are systematically younger than 7 Ma for the Mont-Blanc massif. We compare the thermal history obtained from these literature bedrock-derived data to that derived from the new detrital AFT data collected in the Little Ice Age (LIA) moraine, just at the front of the Bossons glacier (~1300 m elevation). We also compare our results with 5 other samples down the valley at catchment elevations between 460 and 1050 m to evaluate potential changes in the detrital AFT signal as well as the consistency in the retrieved long-term cooling history.Based on these first results, we plan to extend our study to other areas (e.g., Patagonia) to investigate both (1) spatial patterns of glacial erosion for older glacial periods (pre-LGM), and (2) long-term rock cooling histories from moraine deposits where modern bedrock is inaccessible (e.g. under modern glaciers or ice fields).

The microvasculature facilitates gas exchange, provides nutrients to cells, and regulates blood flow in response to stimuli. Vascular abnormalities are an indicator of pathology for various conditions, such as compromised vessel integrity in small vessel disease and angiogenesis in tumors. Traditional immunohistochemistry enables visualization of tissue cross-sections containing exogenously labeled vasculature. Although this approach can be utilized to quantify vascular changes within small fields-of-view, it is not a practical way to study the vasculature on the scale of whole organs. Three-dimensional (3D) imaging presents a more appropriate method to visualize the vascular architecture in tissue. Here we describe the complete protocol that we use to characterize the vasculature of different organs in mice encompassing the methods to fluorescently label vessels, optically clear tissue, collect 3D vascular images, and quantify these vascular images with a semi-automated approach. To validate the automated segmentation of vascular images, one user manually segmented fifty random regions of interest across different vascular images. The automated segmentation results had an average sensitivity of 80±8% and an average specificity of 90±5% when compared to manual segmentation. Applying this procedure of image analysis presents a method to reliably quantify and characterize vascular networks in a timely fashion. This procedure is also applicable to other methods of tissue clearing and vascular labels that generate 3D images of microvasculature.

Introduction: Cerebral microhemorrhages (CMH) are the pathologic substrate of MRI-demonstrable cerebral microbleeds, and are thought to occur when integrity of cerebral microvessels is compromised, leading to deposits of hemosiderin/iron accumulating within brain tissue. The presence of CMH is associated with cognitive decline and ischemic and hemorrhagic stroke. Hypertension (HTN) is a major risk factor for cerebral microbleeds and has been linked to a more significant microbleed burden in patients. Despite the clinical significance of HTN and cerebral microbleeds, our understanding of HTN-induced microbleed formation remains limited, and the vascular origin of CMH remains obscure. Methods: We used a perfusion-based vascular label with tissue clearing to enable three-dimensional visualization of CMH with the surrounding microvascular network. Adult (18-month-old) C57BL/6J mice were administered angiotensin II to induce HTN (n=10) or PBS (n=10). Lectin-DyLight-649 was injected retro-orbitally to bind to the endothelial walls of all blood vessels in a mouse. Brains were cut into 1-mm thick sections, stained with Prussian blue to label CMH, cleared using iDISCO, and imaged via confocal microscopy. MATLAB and neuTube were used to quantify vessel diameters. Results: Using this methodology, we were able to collect three-dimensional transmission images of CMH that were colocalized with three-dimensional fluorescence images of the surrounding microvasculature. The average vessel diameter of the 5 nearest vessels to 17 different CMH was found to be 4.22±0.81 μm, which corresponds to capillary-size vessels. Conclusions: These data support a capillary origin for cerebral microhemorrhages in this mouse model. The capillary origin implies a role for the blood-brain barrier in the development of CMH and cerebral microbleeds in this model of HTN and aging. Three-dimensional imaging has substantial utility for improved understanding of CMH origin.

International audience; Submerged fault ruptures generate earthquake-triggered mass flow deposits, which are extensively used as a tool in subaqueous paleoseismology. In tectonically active deep sedimentary basins, such as the Sea of Marmara (SoM), these mass flow deposits are defined as turbidite-homogenite units (THUs), consisting essentially of a coarse basal part and an overlying homogeneous mud (homogenite). Detailed characterization of THUs is crucial in order to establish meaningful criteria to link these units with earthquakes events and to identify their transport routes and depositional mechanisms. Here, we combine μ-X-ray Fluorescence (μ-XRF), Anisotropy of Magnetic Susceptibility (AMS) and additional rock magnetism analyses of a 21-m long piston core from the Kumburgaz Basin of SoM to define the upper stratigraphic boundary of THUs with hemipelagic sediments and investigate the controls of hydrological changes on turbidite frequency and thickness over the last 15 kyrs BP. The sedimentary succession of this period includes a lower lacustrine and an upper marine unit with two Holocene sapropel intervals. The sequence is interrupted by a total of 70 THUs, characterized by a significant magnetic foliation related to the depositional setting rather than the magnetic signature. Magnetic mineralogy of the coarse basal parts of THUs have more ferromagnetic particles than the overlying homogenites and background sediments. While the homogenite parts have a more constant mineralogy than the basal parts, they do not differ the background sediments.Based on an event-free chronostratigraphic model derived from radiocarbon ages and the published age of lacustrine-marine (L-M) transition, the average THU occurrence intervals in the lacustrine (14.8–12.6 kyrs BP), lower sapropel (11.2–5.7 kyrs BP), upper sapropel (5.4–2.7 kyrs BP) and non-sapropelic part of the marine unit (2.7 kyrs BP-present) are 235 yrs., 287 yrs., 114 yrs. and 160 yrs. respectively. The average thickness of the THUs in the same units are 20.8 cm, 15.7 cm, 6.1 cm and 6.1 cm. The variability of average THU occurrence intervals and THU thicknesses are controlled by the sea level rise and salinity increase following the full marine connection of the SoM at 12.6 kyrs BP, which caused changes in slope stability, sediment composition and sediment deposition in different parts of the basin. Geomechanical properties of the lower sapropel appears to have been important in resulting long THU recurrence intervals and relatively high THU thicknesses.

In the western French Alps, morphologies and deposits from glacial and proglacial environments are inherited from Quaternary glaciations. Geomorphological and geological analyses of these morphologies and deposits highlighted different glacier advances on the foreland and in the internal valleys. These glacier advances have been defined using a morphostratigraphic approach, but the absolute chronological framework represented mainly by 14C dating is very incomplete. More precisely, the absolute age of the foreland morainic complex left by the lyonnais glacial lobe, during its extensions of the last glacial cycle, is not clearly established. Similarly, the ages of the retreat stages upstream of the foreland in the Alpine valleys are incomplete. The aim of this thesis is therefore to characterize geomorphologically and sedimentologically glacial and proglacial deposits, and to date them in order to establish the chronology of glacier fluctuations in the western French Alps. The absolute datings carried out come from the dating methods by cosmogenic radionuclides and by luminescence (OSL). This thesis focuses on the foreland of the western French Alps and more specifically on the internal morainic complex (IMC) resulting from the glaciations of the last glacial cycle and on the associated fluvioglacial systems. Secondly, this thesis aims to highlight and date the fluctuations (glacier advances and glacier retreats) of the glaciers of the French Western Alps from the mountain front to the Maurienne valley. The Maurienne valley where the Arc glacier flowed, is one of the accumulation zones of the lyonnais lobe. In the foreland, a geomorphological and sedimentological analysis of the fluvioglacial systems at the front of the CMI indicate that the fluvioglacial terraces are topographically correlated with different sets of moraines. These fluvioglacial systems were then dated by luminescence. The results indicate a fluvioglacial activity at 75-60 ka during MIS 4 at the origin of the deposition of the terraces correlated to the moraines of the maximum extension of the lyonnais lobe. A second fluvioglacial activity at 30-40 ka at MIS 3 is at the origin of the fluvioglacial terraces correlated to the moraines left by an extension of the lyonnais lobe geometrically similar to that of MIS 4.To complete this OSL chronology, a study on the piedmont aim to date the extensions of the lyonnais lobe using 10Be dating on 9 glacial boulders located on the morainic complex and on with 12 erratic boulderslocated on the rest of the foreland. The results show a return of the lyonnais lobe on the foreland at the LGM at 24-21 ka. This LGM extension is similar with the extensions of MIS 4 and MIS 3. Behind these moraines, a re-advance/stabilization was highlighted at 19 ka. Finally, the exposure ages indicate that the piedmont is deglaciated at 16.5 ka. Upstream of the foreland, unpublished 10Be exposure ages on erratic boulders and published exposure ages on erratic and glacial boulders located in an area spanning the Chambéry cluse and the Maurienne valley, allow to reconstruct the deglaciation dynamic in the French Western Alps during the Lateglacial. These results made it possible to find glacial positions from the entrance of the foreland to the Maurienne between ~16.5 and ~12.5 ka. Between the foreland and the downstream part of the Maurienne, similar exposure ages suggest a rapid glacier retreat at around 16.5 ka over ~120 km, probably promoted by calving in large proglacial lakes. These dates allow to locate glacial positions without identifying fluctuations. In Maurienne, sedimentological analyses of two outcrops have revealed two glacier advances that did not leave moraines. The first glacier advance is suggested in the first outcrop by deformations found in a deltaic deposit. In the second outcrop, increasingly proximal facies towards the top of the sedimentary succession and deformations of ice contact delta attest to the second glacier advance. Sedimentological analyses, dating by exposure and by luminescence, allow to reconstruct 6 fluctuations of the Arc glacier. Three stages of glacier retreat have been highlighted at 16.7-14.6 ka; 15.3 and 14.5 ka respectively. Then, the two stages of re-advance of the Arc glacier highlighted by sedimentological analyses were estimated between 14.5 and 13.6 ka. Finally, the last stage is marked by frontal moraines resulting from a re-advance at 12.5 ka during the Younger Dryas.For the 6 fluctuations identified in the Maurienne, a glacial reconstructions was carried out and made it possible to estimate the variations of the equilibrium line altitude (ELA) between 16.7 and 12.5 ka. These models are also enable to quantify the variations in ice volume and the average mass balance between 16.7 and 14.5 ka, during the period of global warming during the early Bølling-Allerød, in the Lateglacial. Variations in the ELA suggest increasingly dry climatic conditions in the Maurienne. The average mass balance was compared to the mass balances of current glaciers subjected to anthropogenic global warming. These comparisons show that the average mass balances of current glaciers are 10 to 100 times higher than the values calculated for the Arc glacier during the Bølling-Allerød.; Dans les Alpes occidentales françaises, de nombreuses morphologies et dépôts issus d’environnements glaciaires et proglaciaires sont hérités des glaciations du Quaternaire. Depuis plus d’un siècle, deux complexes morainiques ont été reconnus dans la zone de piémont et attribués aux dernières glaciations du Quaternaire. A partir d’analyses géomorphologiques et géologiques sur le piémont et dans les vallées internes, différentes avancées glaciaires ont été identifiées. Ces avancées glaciaires ont été définies par une approche morphostratigraphique, mais le cadre chronologique absolu basé principalement sur des datations 14C reste très fragmentaire. Ainsi, l’âge absolu du complexe des moraines internes (CMI) se trouvant sur le piémont et mis en place par le lobe glaciaire lyonnais reste encore débattu. De même, la dynamique et la chronologie du retrait glaciaire, depuis le dernier maximum glaciaire jusque dans les vallées alpines restent très parcellaires. Le but de cette thèse est donc de définir un meilleur cadre chronologique du dernier maximum glaciaire et des différents stades de retrait dans les Alpes occidentales françaises. Ce travail de thèse se focalise sur le piémont des Alpes occidentales françaises et plus précisément sur le CMI et sur les dépôts fluvioglaciaires associés. Ce travail se concentre également sur la dynamique de retrait depuis le piémont jusqu’en amont de la vallée de la Maurienne. Pour la première fois sur ce secteur, les méthodes de datation absolue par radionucléides cosmogéniques 10Be et par luminescence (OSL) ont été utilisées. Cette étude est basée sur une nouvelle caractérisation géomorphologique et sédimentologique des dépôts glaciaires et proglaciaires, afin de mettre en évidence et de dater les fluctuations (avancées et retraits) des glaciers des Alpes occidentales françaises depuis le front montagneux jusqu’en amont de la vallée de la Maurienne. Dans le piémont, les analyses géomorphologiques et sédimentologiques des systèmes fluvioglaciaires localisés au front du CMI ont mis en évidence une corrélation topographique entre les terrasses fluvioglaciaires et les différents ensembles de moraines. Ces systèmes fluvioglaciaires ont été ensuite datés par luminescence. Les résultats indiquent une activité fluvioglaciaire à 75-60 ka au cours du MIS 4 à l’origine du dépôt des terrasses corrélées aux moraines du maximum d’extension du lobe lyonnais. Une seconde activité fluvioglaciaire à 30-40 ka au MIS 3 est à l’origine des terrasses fluvioglaciaires corrélées aux moraines laissées par une extension du lobe lyonnais géométriquement proche de celle du MIS 4. Pour compléter cette chronologie OSL, nous avons réalisé des datations par âges d’exposition 10Be sur 9 blocs glaciaires localisés sur le complexe morainique et sur 12 blocs erratiques situés sur le reste du piémont. Les résultats montrent un retour du lobe glaciaire sur le piémont au LGM à 24-21 ka. Cette extension LGM est légèrement moins étendue que les extensions du MIS 4 et du MIS 3. En arrière de ces moraines, une réavancée / stabilisation a été mise en évidence à 19 ka. Enfin, les âges d’exposition indiquent que le piémont est déglacé à 16,5 ka. En amont du piémont, des âges d’exposition 10Be ont permis de reconstituer la dynamique de déglaciation dans les Alpes occidentales françaises au Tardiglaciaire. Ces âges d’exposition sont issus de datations inédites sur blocs erratiques ainsi que de datations sur blocs erratiques et glaciaires publiées. Ces résultats ont permis de retrouver des positions glaciaires de l’entrée du piémont (Culoz) jusqu’en amont de la Maurienne (Bessans) entre ~16,5 et ~12,5 ka. Entre l’entrée du piémont et la partie aval de la Maurienne (Pas du Roc), des âges d’exposition proches les uns des autres suggèrent un retrait rapide à environ 16,5 ka sur ~120 km, probablement favorisé par un vêlage dans de grands lacs proglaciaires. En Maurienne, des analyses sédimentologiques de deux affleurements (Verney et Lanslebourg) ont permis de mettre en évidence deux avancées glaciaires n’ayant pas laissé de moraines. La première avancée glaciaire est marquée par des déformations retrouvées dans un dépôt deltaïque au Verney. ALanslebourg, des faciès de plus en plus proximaux vers le haut de la succession sédimentaire et des déformations de cônes proglaciaires sous-aquatiques attestent de la seconde avancée glaciaire. Les analyses sédimentologiques, les datations par exposition et les âges par luminescence, permettent de reconstituer six fluctuations du glacier de l’Arc. Trois étapes de retrait glaciaire ont été mises en évidence à 16,7-14,6 ka ; 15,3 et 14,5 ka respectivement. Puis, deux stades de réavancée du glacier de l’Arc mis en évidence par les analyses sédimentologiques dont l’âge est estimé entre 14,5 et 13,6 ka. Enfin le dernier stade est marqué par des moraines frontales issues d’une réavancée à 12,5 ka au Dryas récent. Pour les six fluctuations glaciaires identifiées en Maurienne, une modélisation géométrique glaciaire a été réalisée et a permis d’estimer les variations de la ligne d’équilibre glaciaire (ELA) entre 16,7 et 12,5 ka. Ces modèles ont également permis de quantifier les variations de volume de glace et le bilan de masse moyen entre 16,7 et 14,5 ka, pendant la période de réchauffement climatique au début du Bølling-Allerød. Les variations de l’altitude de la ELA suggèrent des conditions de plus en plus sèches en Maurienne. Le bilan de masse moyen a été comparé aux bilans de masse des glaciers actuels soumis au réchauffement climatique anthropique. Ces comparaisons montrent que les bilans de masse moyens des glaciers actuels sont 10 à 100 fois supérieurs aux valeurs calculées pour le glacier de l’Arc pendant le Bølling-Allerød.