Global significance of oxygen and carbon isotope compositions of pedogenic carbonates since the Cretaceous     

Marc Jolivet  Philippe Boulvais 《地学前缘(英文版)》2021,12(4):101132

Few global syntheses of oxygen and carbon isotope composition of pedogenic carbonates have been attempted,unlike marine carbonates.Pedogenic carbonates represent in-situ indicators of the climate conditions prevailing on land.The δ~(18)O and δ~(13)C values of pedogenic carbonates are controlled by local and global factors,many of them not affecting the marine carbonates largely used to probe global climate changes.We compile pedogenic oxygen and carbon isotopic data(N= 12,167) from Cretaceous to Quaternary-aged paleosols to identify potential trends through time and tie them to possible controlling factors.While discrete events such as the PaleoceneEocene Thermal Maximum are clearly evidenced,our analysis reveals an increasing complexity in the distribution of the δ~(18)O vs δ~(13)C values through the Cenozoic.As could be expected,the rise of C_4 plants induces a shift towards higher δ~(13)C values during the Neogene and Quaternary.We also show that the increase in global hypsometry during the Neogene plays a major role in controlling the δ~(18)O and δ~(13)C values of pedogenic carbonates by increasing aridity downwind of orographic barriers.Finally,during the Quaternary,an increase of 3‰ inδ~(18)O values is recorded both by the pedogenic carbonates and the marine foraminifera suggesting that both indicators may be used to track global climate signal.  相似文献   

Modeling of damage-related earthquake losses in a moderate seismic-prone country and cost–benefit evaluation of retrofit investments: application to France     

Ismaël Riedel  Philippe Guéguen 《Natural Hazards》2018,90(2):639-662

We performed large-scale earthquake economic loss estimations for France and cost–benefit analyses for several French cities by developing a semiempirical, intensity-based approach. The proposed methodology is inexpensive and easily applicable in case of a paucity of detailed information regarding the specific regional seismic hazard and the structural characteristics of the building stock, which is of particular importance in moderate-to-low seismic hazard regions. The exposure model is derived from census datasets, and the seismic vulnerability distribution of buildings is calculated using data mining techniques. Several hypothetical, large-scale retrofit scenarios are proposed, with increasing levels of investment. These cities, in their respective reinforced states, are then subjected to a series of hazard scenarios. Seismic hazard data for different return periods are calculated from regulatory accelerations from French seismic zoning. Loss estimations for the original (non-reinforced) configuration show high levels of expected building repair and replacement costs for all time spans. Finally, the benefits in terms of damage avoidance are compared with the costs of each retrofit measure. Relatively limited strengthening investments reduce the probability of building collapse, which is the main cause of human casualties. However, the results of this study suggest that retrofitting is, on average, only cost-effective in the parts of France with the highest seismicity and over the longest time horizons.  相似文献   

Developing a likely climate scenario from multiple regional climate model simulations with an optimal weighting factor   总被引：1，自引：0，他引：1  

Hyung-Il Eum  Philippe Gachon  René Laprise 《Climate Dynamics》2014,43(1-2):11-35

This study presents a performance-based comprehensive weighting factor that accounts for the skill of different regional climate models (RCMs), including the effect of the driving lateral boundary condition coming from either atmosphere–ocean global climate models (AOGCMs) or reanalyses. A differential evolution algorithm is employed to identify the optimal relative importance of five performance metrics, and corresponding weighting factors, that include the relative absolute mean error (RAME), annual cycle, spatial pattern, extremes and multi-decadal trend. Based on cumulative density functions built by weighting factors of various RCMs/AOGCMs ensemble simulations, current and future climate projections were then generated to identify the level of uncertainty in the climate scenarios. This study selected the areas of southern Ontario and Québec in Canada as a case study. The main conclusions are as follows: (1) Three performance metrics were found essential, having the greater relative importance: the RAME, annual variability and multi-decadal trend. (2) The choice of driving conditions from the AOGCM had impacts on the comprehensive weighting factor, particularly for the winter season. (3) Combining climate projections based on the weighting factors significantly increased the consistency and reduced the spread among models in the future climate changes. These results imply that the weighting factors play a more important role in reducing the effects of outliers on plausible future climate conditions in regions where there is a higher level of variability in RCM/AOGCM simulations. As a result of weighting, substantial increases in the projected warming were found in the southern part of the study area during summer, and the whole region during winter, compared to the simple equal weighting scheme from RCM runs. This study is an initial step toward developing a likelihood procedure for climate scenarios on a regional scale using equal or different probabilities for all models.  相似文献   

Sensitivity of seasonal precipitation extremes to model configuration of the Canadian Regional Climate Model over eastern Canada using historical simulations     

Philippe Roy  Philippe Gachon  René Laprise 《Climate Dynamics》2014,43(9-10):2431-2453

This study analyzes the uncertainty of seasonal (winter and summer) precipitation extremes as simulated by a recent version of the Canadian Regional Climate Model (CRCM) using 16 simulations (1961–1990), considering four sources of uncertainty from: (a) the domain size, (b) the driving Atmosphere–Ocean Global Climate Models (AOGCM), (c) the ensemble member for a given AOGCM and (d) the internal variability of the CRCM. These 16 simulations are driven by 2 AOGCMs (i.e. CGCM3, members 4 and 5, and ECHAM5, members 1 and 2), and one set of re-analysis products (i.e. ERA40), using two domain sizes (AMNO, covering all North America and QC, a smaller domain centred over the Province of Québec). In addition to the mean seasonal precipitation, three seasonal indices are used to characterize different types of variability and extremes of precipitation: the number of wet days, the maximum number of consecutive dry days, and the 95th percentile of daily precipitation. Results show that largest source of uncertainty in summer comes from the AOGCM selection and the choice of domain size, followed by the choice of the member for a given AOGCM. In winter, the choice of the member becomes more important than the choice of the domain size. Simulated variance sensitivity is greater in winter than in summer, highlighting the importance of the large-scale circulation from the boundary conditions. The study confirms a higher uncertainty in the simulated heavy rainfall than the one in the mean precipitation, with some regions along the Great Lakes—St-Lawrence Valley exhibiting a systematic higher uncertainty value.  相似文献   

Mangrove microbial diversity and the impact of trophic contamination     

Agnès Bouchez  Noémie Pascault  Cècile Chardon  Marc Bouvy  Philippe Cecchi  Luc Lambs  Mélanie Herteman  François Fromard  Patrice Got  Christophe Leboulanger 《Marine pollution bulletin》2013,66(1-2):39-46

Mangroves are threatened ecosystems that provide numerous ecosystem services, especially through their wide biodiversity, and their bioremediation capacity is a challenging question in tropical areas. In a mangrove in Mayotte, we studied the potential role of microbial biofilm communities in removing nutrient loads from pre-treated wastewater. Microbial community samples were collected from tree roots, sediments, water, and from a colonization device, and their structure and dynamics were compared in two areas: one exposed to sewage and the other not. The samples from the colonization devices accurately reflected the natural communities in terms of diversity. Communities in the zone exposed to sewage were characterized by more green algae and diatoms, higher bacteria densities, as well as different compositions. In the area exposed to sewage, the higher cell densities associated with specific diversity patterns highlighted adapted communities that may play a significant role in the fate of nutrients.  相似文献   

Calcul des pluies et débits classés sur le bassin du Bani (Mali): une approche de la vulnérabilité des ouvrages et de la population depuis la sécheresse     

Philippe Roudier  Gil Mahé 《水文科学杂志》2013,58(3):351-363

Résumé Dans un contexte de changement climatique, les dimensionnements d'ouvrages hydrauliques peuvent avoir un rôle crucial dans une évaluation de la vulnérabilité. Ainsi, on calcule avec les données les plus récentes possibles la pluie journalière maximale annuelle de période de retour donnée (10, 20 et 100 ans) sur 51 stations ainsi que les débits de projet pour six stations sur le bassin versant du Bani au Mali (129 000 km²). Pluies et débits sont calculés avec une méthode utilisant les L-moments et en découpant le bassin en régions climatiques homogènes. Une formule empirique d'évaluation du débit décennal est enfin réévaluée, considérant la baisse importante des débits maximaux depuis 1970. Les valeurs trouvées soulignent l'importance du choix de la période, puisque quelques années peuvent faire varier de façon importante les valeurs classées.  相似文献   

7000 years of paleostorm activity in the NW Mediterranean Sea in response to Holocene climate events     

Pierre Sabatier  Laurent Dezileau  Christophe Colin  Louis Briqueu  Frédéric Bouchette  Philippe Martinez  Giuseppe Siani  Olivier Raynal  Ulrich Von Grafenstein 《Quaternary Research》2012,77(1):1-11

A high-resolution record of paleostorm events along the French Mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the Gulf of Lions. Integrating grain size, faunal analysis, clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating, we recorded seven periods of increased storm activity at 6300–6100, 5650–5400, 4400–4050, 3650–3200, 2800–2600, 1950–1400 and 400–50 cal yr BP (in the Little Ice Age). In contrast, our results show that the Medieval Climate Anomaly (1150–650 cal yr BP) was characterised by low storm activity.The evidence for high storm activity in the NW Mediterranean Sea is in agreement with the changes in coastal hydrodynamics observed over the Eastern North Atlantic and seems to correspond to Holocene cooling in the North Atlantic. Periods of low SSTs there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies. We hypothesise that the increase in storm activity during Holocene cold events over the North Atlantic and Mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large Central Atlantic–European domain.  相似文献   

Thermodynamic properties of chlorite and berthierine derived from calorimetric measurements     

Philippe Blanc  Hélène Gailhanou  Jacques Rogez  Georges Mikaelian  Hitoshi Kawaji  Fabienne Warmont  Stéphane Gaboreau  Sylvain Grangeon  Jean-Marc Grenèche  Philippe Vieillard  Claire I. Fialips  Eric Giffaut  Eric C. Gaucher  F. Claret 《Physics and Chemistry of Minerals》2014,41(8):603-615

In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois [USA; (Al_0.975FeIII_0.182FeII_1.422Mg_0.157Li_0.035Mn_0.002)(Si_1.332Al_0.668)O₅(OH)₄] and chlorite CCa-2 from Flagstaff Hill, California [USA; (Si_2.633Al_1.367)(Al_1.116FeIII_0.215Mg_2.952FeII_1.712Mn_0.012Ca_0.011)O₁₀(OH)₈]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738–4749, 2009) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature.  相似文献   

Trial Embankment Analysis to Predict Smear Zone Characteristics Induced by Prefabricated Vertical Drain Installation     

Ali Parsa-Pajouh  Behzad Fatahi  Philippe Vincent  Hadi Khabbaz 《Geotechnical and Geological Engineering》2014,32(5):1187-1210

In this study, FLAC finite difference software has been adopted to simulate the performance of the ground improved using prefabricated vertical drains assisted preloading, considering smear zone characteristics. The numerical code has been applied to predict smear zone properties employing a back calculation procedure using the results of several case studies. The construction of a trial embankment is proposed as a reliable method to predict the smear zone characteristics. The proposed back calculation method is applied to estimate the minimum required degree of consolidation and consequently the minimum required preloading time, resulting in a reliable estimation of the smear zone permeability and extent. Three preloading case studies considering both conventional preloading and vacuum assisted preloading have been simulated to verify the numerical code and to conduct the parametric study using the back calculation procedure. According to the results, the properties of the smear zone can be back-calculated reliably, when at least 33 % degree of consolidation due to trial embankment construction is achieved.  相似文献   

Variscan orogeny in Corsica: new structural and geochronological insights,and its place in the Variscan geodynamic framework     

Michel Faure  Philippe Rossi  Julien Gaché  Jérémie Melleton  Dirk Frei  Xianhua Li  Wei Lin 《International Journal of Earth Sciences》2014,103(6):1533-1551

In Western Corsica, remnants of pre-batholitic lithological and metamorphic assemblages are preserved as km-scale septa enclosed within Lower Carboniferous to Early Permian plutons. Two groups of septa were recognized: (1) the Argentella and Agriates-Tenda fragments correspond to Neoproterozoic rocks deformed and metamorphosed during the Cadomian–Panafrican orogeny, and (2) the Zicavo, Porto-Vecchio, Solenzara–Fautea, Belgodère, Topiti, and Vignola fragments consist of Variscan metamorphic rocks. The lithological content and the main ductile deformation events for each septum are presented. In the Zicavo, Porto-Vecchio, and Topiti septa, a top-to-the-SW ductile shearing (D1 event) coeval with an amphibolite facies metamorphism is responsible for crustal thickening at ca 360 Ma. This main event was preceded by eclogite and granulite facies metamorphic events preserved as restites within migmatites dated at ca 345–330 Ma. A top-to-the-SE ductile shearing (D2 event) coeval with the crustal melting accommodated the exhumation of the D1 event. In contrast, the Belgodère segment is peculiar as it exhibits a top-to-the-E vergence, although retrogressed high-pressure rocks are also recognized. The pre-Permian fragments are arranged in four NW–SE-striking stripes that define a SW–NE zoning with (1) a Western domain in Topiti, Vignola, Zicavo, Porto-Vecchio, and Solenzara–Fautea; (2) a Neoproterozoic basement with its unconformable Early Paleozoic sedimentary cover in Argentella; (3) an Eastern metamorphic domain in Belgodère; (4) another Neoproterozoic basement with its Upper Paleozoic sedimentary cover in Agriates-Tenda. The Argentella basement is separated from the Western and Eastern domains by two sutures: S1 and S2. The Variscan Corsica represents the Eastern part of the Sardinia–Corsica–Maures segment. The comparison of this segment with other Variscan domains allows us to propose some possible correlations. We argue that the Western domain, Argentella, Belgodère, and Agriates-Tenda domains can be compared with the Southern Variscan belt exposed in French Massif Central–Southern Massif Armoricain, Armorica microblock, Léon block, respectively.  相似文献