The information system of the French Peatland Observation Service: Service National d'Observation Tourbières – A valuable tool to assess the impact of global changes on the hydrology and biogeochemistry of temperate peatlands through long term monitoring     

Sébastien Gogo  Jean-Baptiste Paroissien  Fatima Laggoun-Défarge  Jean-Marc Antoine  Léonard Bernard-Jannin  Guillaume Bertrand  Philippe Binet  Stéphane Binet  Guillaume Bouger  Yohann Brossard  Thierry Camboulive  Jean-Pierre Caudal  Stéphane Chevrier  Geneviève Chiapiuso  Benoît D'Angelo  Pilar Durantez  Chris Flechard  André-Jean Francez  Didier Galop  Laure Gandois  Daniel Gilbert  Christophe Guimbaud  Louis Hinault  Adrien Jacotot  Franck Le Moing  Emilie Lerigoleur  Gaël Le Roux  Fabien Leroy  Alexandre Lhosmot  Qian Li  Elodie Machado Da Silva  Jean-Sébastien Moquet  Juanita Mora-Gomez  Laurent Perdereau  Thomas Rosset  Marie-Laure Toussaint 《水文研究》2021,35(6):e14244

Mitigating and adapting to global changes requires a better understanding of the response of the Biosphere to these environmental variations. Human disturbances and their effects act in the long term (decades to centuries) and consequently, a similar time frame is needed to fully understand the hydrological and biogeochemical functioning of a natural system. To this end, the ‘Centre National de la Recherche Scientifique’ (CNRS) promotes and certifies long-term monitoring tools called national observation services or ‘Service National d'Observation’ (SNO) in a large range of hydrological and biogeochemical systems (e.g., cryosphere, catchments, aquifers). The SNO investigating peatlands, the SNO ‘Tourbières’, was certified in 2011 ( https://www.sno-tourbieres.cnrs.fr/ ). Peatlands are mostly found in the high latitudes of the northern hemisphere and French peatlands are located in the southern part of this area. Thus, they are located in environmental conditions that will occur in northern peatlands in coming decades or centuries and can be considered as sentinels. The SNO Tourbières is composed of four peatlands: La Guette (lowland central France), Landemarais (lowland oceanic western France), Frasne (upland continental eastern France) and Bernadouze (upland southern France). Thirty target variables are monitored to study the hydrological and biogeochemical functioning of the sites. They are grouped into four datasets: hydrology, fluvial export of organic matter, greenhouse gas fluxes and meteorology/soil physics. The data from all sites follow a common processing chain from the sensors to the public repository. The raw data are stored on an FTP server. After operator or automatic processing, data are stored in a database, from which a web application extracts the data to make them available ( https://data-snot.cnrs.fr/data-access/ ). Each year at least, an archive of each dataset is stored in Zenodo, with a digital object identifier (DOI) attribution ( https://zenodo.org/communities/sno_tourbieres_data/ ).  相似文献   

Modelling the poroelastoplastic behaviour of soils subjected to internal erosion by suffusion     

Quentin Rousseau  Giulio Sciarra  Rachel Gelet  Didier Marot 《国际地质力学数值与分析法杂志》2020,44(1):117-136

Granular soils subjected to seepage flow may suffer suffusion, ie, a selective internal erosion. Extending the classical approach of poromechanics, we deduce a new form of the Clausius-Duhem inequality accounting for dissipation due to suffusion, and we deduce restrictions on the constitutive laws of the soil. We suggest (a) a possible coupling between the seepage forces and the suffusion kinetics and (b) an extension of an existing elastoplastic model for the skeleton mechanical behaviour. Numerical integrations of the elastoplastic model are carried out under drained axisymmetric triaxial and oedometric conditions. As a result, we prove that the extended model is able to qualitatively reproduce the suffusion induced strains and the strength reduction experimentally observed. Predictions on the oedometric behaviour of suffusive soils are also provided.  相似文献   

Can sediment supply variations create sequences? Insights from stratigraphic forward modelling     

Jinyu Zhang  Peter M. Burgess  Didier Granjeon  Ronald Steel 《Basin Research》2019,31(2):274-289

Classic sequence stratigraphy suggests depositional sequences can form due to changes in accommodation and due to changes in sediment supply. Accommodation‐dominated sequences are problematic to define rigorously, but are commonly interpreted from outcrop and subsurface data. In contrast, supply‐dominated sequences are much less commonly identified. We employ numerical stratigraphic forward modelling to compare stratal geometries forced by cyclic changes in relative sea level with stratal geometries forced by sediment discharge and water discharge changes. Our quantitative results suggest that both relative sea‐level oscillations and variations in sediment/water discharge ratio are able to form sequence‐bounding unconformities independently, confirming previous qualitative sequences definitions. In some of the experiments, the two types of sequence share several characteristics, such as an absence of coastal‐plain topset deposits and stratal offlap, something typically interpreted as the result of falling relative sea level. However, the stratal geometries differ when variations in amplitude and frequency of relative sea‐level change, sediment/water discharge ratio, transport diffusion coefficient and initial bathymetry are applied. We propose that the supply‐dominated sequences could be recognised in outcrop or in the subsurface if the observations of stratal offlap and the absence of coastal‐plain topset can be made without any strong evidence of relative sea‐level fall (e.g. descending shoreline trajectory). These quantitative results suggest that both supply‐dominated and accommodation‐dominated sequences are likely to occur in the ancient record, as a consequence of multiple, possibly complex, controls.  相似文献   

Deglaciation history at the Alpine-Mediterranean transition (Argentera-Mercantour,SW Alps) from 10Be dating of moraines and glacially polished bedrock     

Yann Rolland  Romain Darnault  Régis Braucher  Didier Bourlès  Carole Petit  Stéphane Bouissou  ASTER Team 《地球表面变化过程与地形》2020,45(2):393-410

Estimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source-to-sink studies and paleoclimate reconstructions. The Argentera-Mercantour massif is located at the transition between the Alps and the Mediterranean Sea, therefore, its deglaciation chronology can be compared to the sediment budget of the Var River basin. Based on 13 new cosmic-ray exposure (CRE) beryllium-10 (¹⁰Be) datings performed on moraines and polished crystalline bedrocks and 22 reassessed ¹⁰Be CRE ages from similar altitude nearby steep basement surfaces, and from a lake sediment core, we can constrain the deglaciation chronology of the Argentera-Mercantour massif. These data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at c. 15 ka, at the onset of Bølling transition between the Oldest and Older Dryas. Main deglaciation of the upper slopes [2700–2800 m above sea level (a.s.l.)] occurred after the Last Glacial Maximum (LGM) at 20.8–18.6 ka, followed by the main deglaciation of the lower slopes (2300 m a.s.l.) at 15.3–14.2 ka. Finally, the flat polished surfaces above 2600 m a.s.l. and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the Younger Dryas re-advance stage between 12 and 8–9 ka. At lower elevations, the Vens Lake located at 2300 m a.s.l., allows evidence of the onset of lake sedimentation at c. 14 ka and a transition towards a vegetated environment that mainly occurred before 8 ka. Moraine final stabilization at 5 ka might reflect denudation acceleration during the Holocene humid phase. This contribution reveals a glacier–climate relationship more sensitive to warming phases in the southern Alps highlighted by a major decrease of glaciers after c. 15 ka. This major deglaciation is correlated with a 2.5-fold decrease of sediment discharge of rivers into the Mediterranean Sea. © 2019 John Wiley & Sons, Ltd.  相似文献   

Geological and geophysical studies of the Agoudal impact structure (Central High Atlas,Morocco): New evidence for crater size and age     

Houda El Kerni  Hasnaa Chennaoui Aoudjehane  David Baratoux  Mohammed Aoudjehane  Andr Charrire  Hassan Ibouh  Pierre Rochette  Yoann Quesnel  Minoru Uehara  Thomas Kenkmann  Gerwin Wulf  Michael Poelchau  Van Binh Nguyen  Maria Aboulahris  Samira Makhoukhi  Georges Aumaître  Didier Bourls  Karim Keddadouche 《Meteoritics & planetary science》2019,54(10):2483-2509

Since the discovery of shatter cones (SCs) near the village of Agoudal (Morocco, Central High Atlas Mountains) in 2013, the absence of one or several associated circular structures led to speculation about the age of the impact event, the number, and the size of the impact crater or craters. Additional constraints on the crater size, age, and erosion rates are obtained here from geological, structural, and geophysical mapping and from cosmogenic nuclide data. Our geological maps of the Agoudal impact site at the scales of 1:30,000 (6 km²) and 1:15,000 (2.25 km²) include all known occurrences of SCs in target rocks, breccias, and vertical to overturned strata. Considering that strata surrounding the impact site are subhorizontal, we argue that disturbed strata are related to the impact event. Three types of breccias have been observed. Two of them (br1‐2 and br2) could be produced by erosion–sedimentation–consolidation processes, with no evidence for impact breccias, while breccia (br1) might be impact related. The most probable center of the structure is estimated at 31°59′13.73?N, 5°30′55.14?W using the concentric deviation method applied to the orientation of strata over the disturbed area. Despite the absence of a morphological expression, the ground magnetic and electromagnetic surveys reveal anomalies spatially associated with disturbed strata and SC occurrences. The geophysical data, the structural observations, and the area of occurrence of SCs in target rocks are all consistent with an original size of 1.4–4.2 km in diameter. Cosmogenic nuclide data (³⁶Cl) constrain the local erosion rates between 220 ± 22 m Ma^?1 and 430 ± 43 m Ma^?1. These erosion rates may remove the topographic expression of such a crater and its ejecta in a time period of about 0.3–1.9 Ma. This age is older than the Agoudal iron meteorite age (105 ± 40 kyr). This new age constraint excludes the possibility of a genetic relationship between the Agoudal iron meteorite fall and the formation of the Agoudal impact site. A chronolgy chart including the Atlas orogeny, the alternation of sedimentation and erosion periods, and the meteoritic impacts is presented based on all obtained and combined data.  相似文献   

Multimodel analysis on the response of the AMOC under an increase of radiative forcing and its symmetrical reversal     

Sgubin  Giovanni  Swingedouw  Didier  Drijfhout  Sybren  Hagemann  Stefan  Robertson  Eddy 《Climate Dynamics》2015,45(5-6):1429-1450

Climate Dynamics - The response of the Atlantic meridional overturning circulation (AMOC) to an increase of radiative forcing (ramp-up) and a subsequent reversal of radiative forcing (ramp-down) is...  相似文献   

HP–UHP metamorphism as an indicator of slab dip variations in the Alpine arc     

Nicolas Carry  Fredéric Gueydan  Didier Marquer  Jean Pierre Brun 《International Journal of Earth Sciences》2011,100(5):1087-1094

HP/UHP and LT metamorphic units that commonly occur in the inner parts of mountain belts result from the subduction of continental and oceanic material, most often exhumed prior to continental collision. The prograde pressure–temperature history of HP–UHP rocks strongly depends on the convergence rate and on the subduction zone geometry. The maximum pressure recorded provides a proxy for the depth of shearing off and stacking of HP metamorphic nappes. A 2-D thermal model of continental subduction at lithospheric scale is used to compute the length and pressure peak of detached HP metamorphic units as a function of the slab dip angle and the convergence rate. Model results are applied to the metamorphic nappe pile of the inner Alps. A mean convergence rate of 1 cm/year during the subduction of the Briançonnais terrane is indicated by the paleogeographic reconstructions between 46 and 38 Ma. On this basis, the available petrological data and lengths of metamorphic units are used to compute the variations of the slab dip angle. The slab dip angle is shown to increase, from the northeast to the southwest, along the Alpine arc with estimated values of 20° for Suretta, 30–45° for Monte Rosa and Gran Paradiso, and 60° for Dora Maira. From Eocene to Oligocene times, the increase in slab dip angle is controlled by changes of buoyancy, due to the spatial configuration of the Valaisan trough and the incoming of crustal material within the subduction zone.  相似文献   

Internal erosion in granular media: direct numerical simulations and energy interpretation          下载免费PDF全文

Luc Sibille  Franck Lominé  Philippe Poullain  Yacine Sail  Didier Marot 《水文研究》2015,29(9):2149-2163

  相似文献   

Low melting temperature for calcite at 1000 bars on the join CaCO3‐H2O – some geological implications          下载免费PDF全文

Cyril Durand  Lukas P. Baumgartner  Didier Marquer 《地学学报》2015,27(5):364-369

Melting experiments of calcite were performed on the join CaCO₃‐H₂O at a pressure of 1000 bars. The system evolves to the ternary CaO‐H₂O‐CO₂ system during melting experiments. Our experiments show that partial melting of calcite begins at a low temperature, below 650 °C. Such a low partial melting temperature for carbonates revives the debate about the presence of carbonate melts in the upper crust. More specifically, the conditions for carbonate partial melting are present in carbonate host rocks undergoing contact metamorphism at high temperatures in the presence of water‐rich fluid. The presence of carbonate melts influences physical parameters such as viscosity and permeability in contact aureoles, and, furthermore, decarbonation reactions release massive amounts of CO₂.  相似文献   

8000 years of vegetation history in the northern Iberian Peninsula inferred from the palaeoenvironmental study of the Zalama ombrotrophic bog (Basque‐Cantabrian Mountains,Spain)          下载免费PDF全文

Sebastián Pérez‐Díaz  José Antonio López‐Sáez  Xabier Pontevedra‐Pombal  Martín Souto‐Souto  Didier Galop 《Boreas: An International Journal of Quaternary Research》2016,45(4):658-672

This paper focuses on pollen, spores, non‐pollen palynomorphs (NPPs) and certain geochemical elements from the ombrotrophic blanket bog of Zalama (Basque‐Cantabrian Mountains, northern Iberian Peninsula), with the support of a robust chronology based on 17 AMS ¹⁴C dates. The main results related to the last 8000 years show that, during the early middle Holocene, pines and deciduous forests were the most extensive tree formations. At the beginning of the succession, pines reach 44%, showing regional presence, whereas after 7600 cal. a BP, deciduous forests were particularly abundant. From c. 6500 cal. a BP the pollen diagram constructed from our samples shows the first anthropogenic evidence, linked with the new economic practices related to the Neolithic of the Basque‐Cantabrian Mountains. From 3300 cal. a BP the expansion of Fagus sylvatica is particularly clear, and has since then become one of the dominant forest species in this region. We also discuss the Holocene evolution of other noteworthy plant communities in southwestern Europe, such as Taxus baccata, Juglans and shrublands.  相似文献