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Le début du Crétacé a été marqué en Europe occidentale par le développement de paléoaltérations de type latéritique. Les argiles rouges à cuirasse ferrugineuse pisolitique du graben de Saint-Maixent-l’École (seuil du Poitou) peuvent constituer un exemple-témoin de ce type d’altération. Toutefois, leur âge reste inconnu et leur position stratigraphique, au-dessus des calcaires oligocènes du fond du graben, ne permet pas d’exclure un âge de formation beaucoup plus récent. Des pisolites de goethite provenant de ces sols latéritiques ont été échantillonnés dans la forêt de Fouilloux et ont fait l’objet d’analyses isotopiques Rb-Sr, U-Th et δ 18 O-δD, afin de tenter de lever l’indétermination sur l’âge de leur formation. Pour Rb-Sr, outre les analyses sur pisolites totaux, des expériences de lessivages ménagés ont été effectuées afin d’essayer d’isoler un composant radiogénique. Les résultats obtenus n’ont pas permis de donner un âge fiable par la méthode des isochrones, même si les données tendraient plutôt à faire remonter l’épisode d’altération au début du Crétacé. Les analyses δ 18 O-δD ont été effectuées sur des pisolites de goethite totaux, ainsi que sur des fragments sous-échantillonnés. Les résultats plaident en faveur de conditions de formation en zone climatique chaude et/ou aride. Aucun argument en faveur d’un âge fini ou post-oligocène ne peut être tiré de l’étude des isotopes de l’oxygène et de l’hydrogène. Enfin, les analyses U-Th ont été effectuées sur des goethites totales ainsi que sur des fragments sous-échantillonnés. Les rapports d’activités 234 U/ 238 U sont tous légèrement supérieurs à l’équilibre séculaire, indiquant que les goethites évoluent actuellement et/ou ont évolué récemment en système ouvert. Ainsi, les sols latéritiques apparaissent toujours comme géochimiquement actifs. Si cette étude n’a pas permis d’apporter une réponse claire sur l’âge des sols latéritiques, l’hypothèse la plus probable au vu des données isotopiques est que ces sols latéritiques se sont développés au-dessus des calcaires kimméridgiens sur les bordures du graben de Saint-Maixent-l’École, puis remaniés et finalement resédimentés au fond du graben. It has been previously established that Western Europe underwent an important episode of lateritic weathering during early cretaceous times. In this context, the red clays and ferrugineous pisoids deposits occurring in the graben of Saint-Maixent-l’École (Poitou saddle) may represent remnants of lateritic formations associated with this paleoweathering episode. However, their exact age is unknown, and since they occur on top of the Oligocene limestones filling the graben, it cannot be ruled out that these lateritic soils formed more recently. In order to better constrain the age of these lateritic formations, goethite pisoids were sampled in the Fouilloux forest and investigated for Rb-Sr, U-Th and δO-δD isotopic systems. Rb and Sr have been measured on bulk pisoids, and also on leachates and residues from leaching experiments carried out in the attempt to isolate a radiogenic component. No reliable Rb-Sr isochron age could be derived, although the isotopic data would favor an early Cretaceous age for these lateritic formations. δ 18 O-δD measurements have been done on bulk goethite pisoids, and also on sub-fragments. The results indicate that the pisoids likely formed under a warm and/or arid climate. No argument for a late of post – oligocene age can be found from the oxygen and hydrogen isotope data. Finally, U-Th analyses have been carried on bulk samples of goethites, and on sub-fragments as well. 234 U/ 238 U activity ratios are typically slightly higher than the equilibrium value, which indicates that goethites have recently evolved as open systems (if not still open). Hence, pedogenesis processes are still active from a geochemical point of view in these lateritic soils. This study has not allowed to derive a reliable age for these lateritic soils. However, when the results from the different isotopic systems investigated here are considered together, the best interpretation is that these lateritic soils developed most probably over the kimmeridgian limestones along the edge of the Saint-Maixent-l’École graben, and were reworked and redeposited at the bottom of the graben later on.

Hard rocks or crystalline rocks (i.e., plutonic and metamorphic rocks) constitute the basement of all continents, and are particularly exposed at the surface in the large shields of Africa, India, North and South America, Australia and Europe. They were, and are still in some cases, exposed to deep weathering processes. The storativity and hydraulic conductivity of hard rocks, and thus their groundwater resources, are controlled by these weathering processes, which created weathering profiles. Hard-rock aquifers then develop mainly within the first 100 m below ground surface, within these weathering profiles. Where partially or noneroded, these weathering profiles comprise: (1) a capacitive but generally low-permeability unconsolidated layer (the saprolite), located immediately above (2) the permeable stratiform fractured layer (SFL). The development of the SFL’s fracture network is the consequence of the stress induced by the swelling of some minerals, notably biotite. To a much lesser extent, further weathering, and thus hydraulic conductivity, also develops deeper below the SFL, at the periphery of or within preexisting geological discontinuities (joints, dykes, veins, lithological contacts, etc.). The demonstration and recognition of this conceptual model have enabled understanding of the functioning of such aquifers. Moreover, this conceptual model has facilitated a comprehensive corpus of applied methodologies in hydrogeology and geology, which are described in this review paper such as water-well siting, mapping hydrogeological potentialities from local to country scale, quantitative management, hydrodynamical modeling, protection of hard-rock groundwater resources (even in thermal and mineral aquifers), computing the drainage discharge of tunnels, quarrying, etc.

It has been previously established that Western Europe underwent an important episode of lateritic weathering during early cretaceous times. In this context, the red clays and ferrugineous pisoids deposits occurring in the graben of Saint-Maixent-l'Ecole (Poitou saddle) may represent remnants of lateritic formations associated with this paleoweathering episode. However, their exact age is unknown, and since they occur on top of the Oligocene limestones filling the graben, it cannot be ruled out that these lateritic soils formed more recently. In order to better constrain the age of these lateritic formations, goethite pisoids were sampled in the Fouilloux forest and investigated for Rb-Sr, U-Th and delta O-delta D isotopic systems. Rb and Sr have been measured on bulk pisoids, and also on leachates and residues from leaching experiments carried out in the attempt to isolate a radiogenic component. No reliable Rb-Sr isochron age could be derived, although the isotopic data would favor an early Cretaceous age for these lateritic formations. delta O-18-delta D measurements have been done on bulk goethite pisoids, and also on sub-fragments. The results indicate that the pisoids likely formed under a warm and/or arid climate. No argument for a late of post - oligocene age can be found from the oxygen and hydrogen isotope data. Finally, U-Th analyses have been carried on bulk samples of goethites, and on sub-fragments as well. U-234/U-238 activity ratios are typically slightly higher than the equilibrium value, which indicates that goethites have recently evolved as open systems (if not still open). Hence, pedogenesis processes are still active from a geochemical point of view in these lateritic soils. This study has not allowed to derive a reliable age for these lateritic soils. However, when the results from the different isotopic systems investigated here are considered together, the best interpretation is that these lateritic soils developed most probably over the kimmeridgian limestones along the edge of the Saint-Maixent-l'Ecole graben, and were reworked and redeposited at the bottom of the graben later on. -Le début du Crétacé a été marqué en Europe occidentale par le développement de paléoaltérations de type latéritique. Les argiles rouges à cuirasse ferrugineuse pisolitique du graben de Saint-Maixent-l'École (seuil du Poitou) peuvent constituer un exemple-témoin de ce type d'altération. Toutefois, leur âge reste inconnu et leur position stratigraphique, au-dessus des calcaires oligocènes du fond du graben, ne permet pas d'exclure un âge de formation beaucoup plus récent. Des pisolites de goethite provenant de ces sols latéritiques ont été échantillonnés dans la forêt de Fouilloux et ont fait l'objet d'analyses isotopiques Rb-Sr, U-Th et d 18 OdD , afin de tenter de lever l'indétermination sur l'âge de leur formation. Pour Rb-Sr, outre les analyses sur pisolites totaux, des expériences de lessivages ménagés ont été effectuées afin d'essayer d'isoler un composant radiogénique. Les résultats obtenus n'ont pas permis de donner un âge fiable par la méthode des isochrones, même si les données tendraient plutôt à faire remonter l'épisode d'altération au début du Crétacé. Les analyses d 18 OdD ont été effectuées sur des pisolites de goethite totaux, ainsi que sur des fragments sous-échantillonnés. Les résultats plaident en faveur de conditions de formation en zone climatique chaude et/ou aride. Aucun argument en faveur d'un âge fini ou post-oligocène ne peut être tiré de l'étude des isotopes de l'oxygène et de l'hydrogène. Enfin, les analyses U-Th ont été effectuées sur des goethites totales ainsi que sur des fragments sous-échantillonnés. Les rapports d'activités 234 U/ 238 U sont tous légèrement supérieurs à l'équilibre séculaire, indiquant que les goethites évoluent actuellement et/ou ont évolué récemment en système ouvert. Ainsi, les sols latéritiques apparaissent toujours comme géochimiquement actifs. Si cette étude n'a pas permis d'apporter une réponse claire sur l'âge des sols latéritiques, l'hypothèse la plus probable au vu des données isotopiques est que ces sols latéritiques se sont développés au-dessus des calcaires kimméridgiens sur les bordures du graben de Saint-Maixent-l'École, puis remaniés et finalement resédimentés au fond du graben.

It has been previously established that Western Europe underwent an important episode of lateritic weathering during early Cretaceous times. In this context, the red clays and ferrugineous pisoids deposits occurring in the graben of Saint-Maixent-l'Ecole (Poitou saddle) may represent remnants of lateritic formations associated with this paleoweathering episode. However, their exact age is unknown, and since they occur on top of the Oligocene limestones filling the graben, it cannot be ruled out that these lateritic soils formed more recently. In order to better constrain the age of these lateritic formations, goethite pisoids were sampled in the Fouilloux forest and investigated for Rb-Sr, U-Th and δO-δD isotopic systems. Rb and Sr have been measured on bulk pisoids, and also on leachates and residues from leaching experiments carried out in the attempt to isolate a radiogenic component. No reliable Rb-Sr isochron age could be derived, although the isotopic data would favor an early Cretaceous age for these lateritic formations. δ18O-δD measurements have been done on bulk goethite pisoids, and also on sub-fragments. The results indicate that the pisoids likely formed under a warm and/or arid climate. No argument for a late of post-Oligocene age can be found from the oxygen and hydrogen isotope data. Finally, U-Th analyses have been carried on bulk samples of goethites, and on sub-fragments as well. 234U/238U activity ratios are typically slightly higher than the equilibrium value, which indicates that goethites have recently evolved as open systems (if not still open). Hence, pedogenesis processes are still active from a geochemical point of view in these lateritic soils. This study has not allowed to derive a reliable age for these lateritic soils. However, when the results from the different isotopic systems investigated here are considered together, the best interpretation is that these lateritic soils developed most probably over the Kimmeridgian limestones along the edge of the Saint-Maixent-l'Ecole graben, and were reworked and redeposited at the bottom of the graben later on.

We developed a high-resolution MIKE SHE/MIKE 11 model of a 231.3 ha headwater catchment in the granitic uplands of the French Massif Central to estimate the contribution of groundwater upwelling to the water balance of the Dauges mire, an acidic valley mire of international importance for nature conservation. We estimated that groundwater upwelling from the underlying weathered granite formations – mostly an approximately 55 m deep fissured zone – provides 27.1 % of total long-term inflows to the mire. This contribution increases to 37.2 % in September when total inflows are small. Overland boundary inflow accounts for an average of 40.2 % of total inflows. However, most of this originates from groundwater seepage through mineral soils along the mire margins or in small non-channelised valleys upslope of the mire. A sensitivity analysis showed that model performance in terms of the simulation of mire groundwater levels was most sensitive to parameters describing the mineral soils and weathered granite formations rather than the overlying peat layer. Variation partitioning demonstrated that groundwater upwelling was the most important factor driving simulated monthly groundwater table depth within the mire. Sustained groundwater upwelling maintains the mire water table close to or at ground level for most of the year. As a result, precipitation and overland boundary inflows quickly leave the wetland as saturation-excess runoff. There was close agreement between the observed distribution of mire habitats and areas where the simulated long-term groundwater seepage rate was larger than zero in September. Our results demonstrate that, contrary to the assumed small contribution of groundwater to the hydrology of hard-rock regions, groundwater upwelling from underlying weathered formations can be a quantitatively important and functionally critical element of the water balance of valley mires in granitic headwater catchments. These results have important legal and management implications.

We present an integrated petrological, petrophysical, and hydrogeological study of the critical zone (CZ) developed in the Hercynian granitic basement of the Strengbach watershed (Vosges Massif, France) to characterize its deep architecture and water circulation levels. For this purpose, six boreholes (50–120 m depth), from which three are cored, and three piezometers (10–15 m depth) were drilled to define the vertical extension and lateral variability of the main CZ horizons. The Strengbach watershed is composed of a topsoil horizon of limited vertical extension (0.8–1.2 m), a mobile saprolite level, and an in-place fractured bedrock. The latter is subdivided into a few meters thick saprock horizon, defined by open sub-horizontal fractures and a deeper fractured bedrock horizon with steeply dipping fractures ( > 50°). In the north-facing slope, the vertical extension of the mobile saprolite horizon increases from ≈ 1–2 m at the top of the slope to ≈ 9 m downstream, close to the valley bottom. In contrast, the south-facing and more easterly slope shows a mobile saprolite horizon with limited vertical extension ( ≈ 2–3 m thick). Such a difference is associated with the existence of a knickpoint in the river bed, separating a downstream zone marked by currently active erosion from an upstream one, less prone to erosion, with preserved reliefs formed around 20 ka ago. The water circulation scheme within the Strengbach watershed involves two different systems: a subsurface circulation within the shallow aquifer, corresponding to the mobile saprolite horizon and the saprock, and a deeper circulation in the fractured bedrock. The water circulation in the fractured bedrock is controlled by fractures of regional orientations, linked to the Vosges massif and the Rhine Graben Tertiary tectonics, and partly to reactivated Hercynian fracture zones. The unaltered bedrock was not reached by any of the three cores. These results from the Strengbach CZ demonstrate the importance of integrating geological history of the watershed, either the long-term geological bedrock evolution or the Quaternary erosion patterns, to better understand and model the CZ hydrological functioning at the watershed scale.

From the study of the Strengbach and Ringelbach watersheds we propose to illustrate the interest of combining the geochemical tracing and geochemical modeling approaches on surface and deep borehole waters, to decipher the diversity of the water flow and the associated water–rock interactions in such elementary mountainous catchments. The results point to a clear geochemical typology of waters depending on the water circulations (deep vs. hypodermic) within the substratum.

Amyotrophic lateral sclerosis (ALS) is an incurable degenerative disorder of motoneurons. We recently reported that reduced expression of Vegfa causes ALS-like motoneuron degeneration in Vegfa δ/δ mice. In a meta-analysis of over 900 individuals from Sweden and over 1,000 individuals from Belgium and England, we now report that subjects homozygous with respect to the haplotypes −2,578A/−1,154A/−634G or −2,578A/−1,154G/−634G in the VEGF promoter/leader sequence had a 1.8 times greater risk of ALS ( P = 0.00004). These 'at-risk' haplotypes lowered circulating VEGF levels in vivo and reduced VEGF gene transcription, IRES-mediated VEGF expression and translation of a novel large-VEGF isoform (L-VEGF) in vivo . Moreover, SOD1 G93A mice crossbred with Vegfa δ/δ mice died earlier due to more severe motoneuron degeneration. Vegfa δ/δ mice were unusually susceptible to persistent paralysis after spinal cord ischemia, and treatment with Vegfa protected mice against ischemic motoneuron death. These findings indicate that VEGF is a modifier of motoneuron degeneration in human ALS and unveil a therapeutic potential of Vegfa for stressed motoneurons in mice.