Late Pleistocene climatic change in the French Jura (Gigny) recorded in the δO of phosphate from ungulate tooth enamel     

Magali Fabre  Christophe Lcuyer  Jean-Philip Brugal  Romain Amiot  Franois Fourel  Franois Martineau 《Quaternary Research》2011,75(3):605-613

Oxygen isotope compositions of phosphate in tooth enamel from large mammals (i.e. horse and red deer) were measured to quantify past mean annual air temperatures and seasonal variations between 145 ka and 33 ka in eastern France. The method is based on interdependent relationships between the δ¹⁸O of apatite phosphate, environmental waters and air temperatures. Horse (Equus caballus germanicus) and red deer (Cervus elaphus) remains have δ¹⁸O values that range from 14.2‰ to 17.2‰, indicating mean air temperatures between 7°C and 13°C. Oxygen isotope time series obtained from two of the six horse teeth show a sinusoidal-like signal that could have been forced by temperature variations of seasonal origin. Intra-tooth oxygen isotope variations reveal that at 145 ka, winters were colder (? 7 ± 2°C) than at present (3 ± 1°C) while summer temperatures were similar. Winter temperatures mark a well-developed West–East thermal gradient in France of about ? 9°C, much stronger than the ?4°C difference recorded presently. Negative winter temperatures were likely responsible for the extent and duration of the snow cover, thus limiting the food resources available for large ungulates with repercussions for Neanderthal predators.  相似文献   

Biogeochemical processes in a clay formation in situ experiment: Part F - Reactive transport modelling     

Christophe Tournassat  Peter Alt-EppingEric C. Gaucher  Thomas Gimmi  Olivier X. LeupinPaul Wersin 《Applied Geochemistry》2011,26(6):1009-1022

  相似文献   

气候环境变化研究中影响粘土矿物形成及其丰度因素的讨论          下载免费PDF全文

孙庆峰  Christophe Colin  陈发虎  张家武 《岩石矿物学杂志》2011,30(2):291-300

粘土矿物在形成过程中受构造运动、气候、盆地规模、地表母岩、土壤、植被、地貌、介质环境、风以及成岩作用等多种因素的影响,这些因素对地层中粘土矿物的类型和含量的影响程度不一。构造运动和气候是影响粘土矿物形成的两个主要因素,对沉积物中的粘土矿物形成和含量以及影响粘土矿物形成的其他次要影响因素有着控制作用。在构造活动稳定的状态下,气候则成为影响粘土矿物形成和含量的决定性因素,其他因素尽管也有不同程度的影响,但可以看成是相对稳定不变的,粘土矿物携带的主要是气候环境变化的信息。地表水系的复杂程度引起的沉积物的混合程度影响粘土矿物信号的清晰度,沉积埋藏成岩作用对粘土矿物的影响也不容忽视。  相似文献   

About the effect of relative humidity on the indentation response of Meuse/Haute�CMarne argillite     

Vincent Magnenet  Albert Giraud  Christophe Auvray 《Acta Geotechnica》2011,6(3):155-166

The unsaturated poromechanical behavior of Callovo-Oxfordian argillite (also referred to as Meuse/Haute–Marne argillite) is analyzed by means of indentation tests at different hygrometries. Numerical simulations carried out with a finite element code are then used to simulate flat punch indentation tests at different controlled hygrometries. The numerical response F(h) is compared to experimental data in order to estimate the drained Young’s modulus E and the internal friction angle \Upphi\Upphi (at high confinement) by means of a back analysis. A linear decrease in the drained Young’s modulus and quasi-constant values of the internal friction angle are observed when the relative humidity ranges. Some predictions of the model are also presented to quantify the activation of hydraulic phenomena. Indeed, the maximal variation of the saturation and porosity relative to the initial state of the specimen are lower than 10% and 8%, respectively.  相似文献   

Weathering of sandstone lotus petals at the Angkor site: a 1,000-year stone durability trial   总被引：1，自引：1，他引：0  

Marie-Françoise André  Bruno Phalip  Olivier Voldoire  Franck Vautier  Yves Géraud  Mhammed Benbakkar  Christophe Constantin  Fabienne Huber  Gilles Morvan 《Environmental Earth Sciences》2011,63(7-8):1723-1739

This article is based on field investigations carried out at Ta Keo and Banteay Srei temples (Angkor, Cambodia), which have similar environmental histories and display the same recurrent decorative pattern (lotus petal) in three different sandstone lithotypes. Based on two original scales of mechanical and chemical weathering, the degree of deterioration of c.2000 sandstone petals was visually assessed, resulting in the proposal of a durability scale. An explanatory scheme was provided, based on laboratory analyses of stone materials (ICP-AES, XRD, SEM-EDS, polarizing microscopy and mercury injection). The key drivers of sandstone durability are both mineralogical and petrophysical. The remarkable preservation of the pink sandstone is due to the quartzose nature of its clasts, the non-swelling clay content of its abundant matrix (kaolinite) and its porosity structure (large connected pores and probable non-connected porosity). The overall good preservation of the green sandstone is due to its extremely low porosity and specific surface area, associated with its strong cementation. The severe deterioration of the grey sandstone is due to its laminated structure (oriented biotites), the susceptibility to hygric swelling and solution of its binding agents (chlorite/smectite and calcite) and its porosity structure, which evolves during a two-stage weathering sequence. The first stage is characterized by a bimodal porosity due to the partial clogging of macropores by swelling clays, and the second stage by a substantial increase in porosity and the penetration of salts (barite and anhydrite). Conversely, oxidation phenomena associated with weathering can lead to a drastic reduction of porosity.  相似文献   

Morphology, distribution and origin of recent submarine landslides of the Ligurian Margin (North-western Mediterranean): some insights into geohazard assessment     

S��bastien Migeon  Antonio Cattaneo  Virginie Hassoun  Christophe Larroque  Nicola Corradi  Francesco Fanucci  Alexandre Dano  Bernard Mercier de Lepinay  Fran?oise Sage  Christian Gorini 《Marine Geophysical Researches》2011,32(1-2):225-243

Based on new multibeam bathymetric data, seismic-reflection profiles and side-scan sonar images, a great number of submarine failures of various types and sizes was identified along the northern margin of the Ligurian Basin and characterized with 3 distinct end-members concerning their location on the margin, sedimentary processes and possible triggering mechanisms. They include superficial landslides mainly located in the vicinity of the main mountain-supplied rivers and on the inner walls of canyons (typically smaller that 10⁸ m³ in volume: Type 1), deep scars 100?C500 m high along the base of the continental slope (Type 2), and large-scale scars and Mass Transport Deposits (MTDs) affecting the upper part of the slope (Type 3 failures). The MTDs are located in different environmental contexts of the margin, including the deep Var Sedimentary Ridge (VSR) and the upper part of the continental slope in the Gulf of Genova (Finale Slide and Portofino Slide), with volumes of missing sediment reaching up to 1.5 × 10⁹ m³. High sedimentation rates related to hyperpycnal flows, faults and earthquake activity, together with sea-level fluctuations are the main factors invoked to explain the distribution and sizes of these different failure types.  相似文献   

Recent contributions of geotechnical centrifuge modelling to the understanding of jack-up spudcan behaviour     

Christophe Gaudin  Britta Bienen 《Ocean Engineering》2011,38(7):900-48

The paper presents an overview of the recent contributions of centrifuge modelling to the understanding of soil-structure interaction and the development of design and predictive methods in the field of mobile jack-up drilling rig foundations. Both advantages and limitations of the centrifuge methods are detailed and key examples are presented. The benefits provided by centrifuge modelling to the development of analysis methods that are now being used within the jack-up industry are highlighted. To conclude, industry trends and research opportunities are discussed, as is the possible role of the geotechnical centrifuge in finding solutions to these new needs.  相似文献   

Transport of Snow by the Wind: A Comparison Between Observations in Ad��lie Land, Antarctica, and Simulations Made with the Regional Climate Model MAR     

Hubert Gall��e  Alexandre Trouvilliez  C��cile Agosta  Christophe Genthon  Vincent Favier  Florence Naaim-Bouvet 《Boundary-Layer Meteorology》2013,146(1):133-147

For the first time a simulation of blowing snow events was validated in detail using one-month long observations (January 2010) made in Adélie Land, Antarctica. A regional climate model featuring a coupled atmosphere/blowing snow/snowpack model is forced laterally by meteorological re-analyses. The vertical grid spacing was 2 m from 2 to 20 m above the surface and the horizontal grid spacing was 5?km. The simulation was validated by comparing the occurrence of blowing snow events and other meteorological parameters at two automatic weather stations. The Nash test allowed us to compute efficiencies of the simulation. The regional climate model simulated the observed wind speed with a positive efficiency (0.69). Wind speeds higher than 12 m s ^?1 were underestimated. Positive efficiency of the simulated wind speed was a prerequisite for validating the blowing snow model. Temperatures were simulated with a slightly negative efficiency (?0.16) due to overestimation of the amplitude of the diurnal cycle during one week, probably because the cloud cover was underestimated at that location during the period concerned. Snowfall events were correctly simulated by our model, as confirmed by field reports. Because observations suggested that our instrument (an acoustic sounder) tends to overestimate the blowing snow flux, data were not sufficiently accurate to allow the complete validation of snow drift values. However, the simulation of blowing snow occurrence was in good agreement with the observations made during the first 20 days of January 2010, despite the fact that the blowing snow flux may be underestimated by the regional climate model during pure blowing snow events. We found that blowing snow occurs in Adélie Land only when the 30-min wind speed value at 2 m a.g.l. is >10 m s ^?1. The validation for the last 10 days of January 2010 was less satisfactory because of complications introduced by surface melting and refreezing.  相似文献   

Projected changes in the tropical Pacific Ocean of importance to tuna fisheries     

Alexandre Ganachaud  Alexander Sen Gupta  Jaclyn N. Brown  Karen Evans  Christophe Maes  Les C. Muir  Felicity S. Graham 《Climatic change》2013,119(1):163-179

Future physical and chemical changes to the ocean are likely to significantly affect the distribution and productivity of many marine species. Tuna are of particular importance in the tropical Pacific, as they contribute significantly to the livelihoods, food and economic security of island states. Changes in water properties and circulation will impact on tuna larval dispersal, preferred habitat distributions and the trophic systems that support tuna populations throughout the region. Using recent observations and ocean projections from the CMIP3 and preliminary results from CMIP5 climate models, we document the projected changes to ocean temperature, salinity, stratification and circulation most relevant to distributions of tuna. Under a business-as-usual emission scenario, projections indicate a surface intensified warming in the upper 400 m and a large expansion of the western Pacific Warm Pool, with most surface waters of the central and western equatorial Pacific reaching temperatures warmer than 29 °C by 2100. These changes are likely to alter the preferred habitat of tuna, based on present-day thermal tolerances, and in turn the distribution of spawning and foraging grounds. Large-scale shoaling of the mixed layer and increases in stratification are expected to impact nutrient provision to the biologically active layer, with flow-on trophic effects on the micronekton. Several oceanic currents are projected to change, including a strengthened upper equatorial undercurrent, which could modify the supply of bioavailable iron to the eastern Pacific.  相似文献   

The Séchilienne (France) Landslide:a Non-typical Progressive Failure Implying Major Risks     

Jean-Louis DURVILLE  Christophe BONNARD  Pierre POTHERAT 《山地科学学报》2011,8(2):117-123

The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion might result in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard assessment based on geological and hydrological surveys, including small scale hydraulic tests, as well as the risk evaluation that has been performed. The risk management relies first upon a high level monitoring and an emergency plan; various mitigation strategies have been considered.  相似文献