Datation UPb sur zircons des dolérites tholéiitiques pyrénéennes (ophites) à la limite Trias–Jurassique et relations avec les tufs volcaniques dits « infra-liasiques » nord-pyrénéens     

Philippe Rossi  Alain Cocherie  C.Mark Fanning  Yves Ternet 《Comptes Rendus Geoscience》2003,335(15):1071-1080

The tholeiitic doleritic magmatism (ophites) in the Aspe valley of the Pyrenees has been dated on the Triassic–Jurassic boundary (199±2 Ma) by the UPb method on zircon (SHRIMP). Emplacement of the ophites was probably synchronous with that of the earliest ‘Infraliassic’ Ségalas tuffs. The ophites are thus related to the Central Atlantic Magmatic Province (CAMP) whose emplacement linked with the fracturing of Pangea, preceded the opening of the Atlantic Ocean. To cite this article: P. Rossi et al., C. R. Geoscience 335 (2003).  相似文献   

Study Of `Soft' Night-Time Surface-Layer Decoupling Over Forest Canopies In A Land-Surface Model     

Yves Delage  Paul A. Bartlett  J. Harry McCaughey 《Boundary-Layer Meteorology》2002,103(2):253-276

The cause of a night-time land-surface model cold bias over forest canopies at threedifferent sites is studied in connection with various formulations of turbulent transferand the phenomenon of decoupling between the surface and the boundary layer. Themodel is the Canadian Land Surface Scheme (CLASS), a leading internationally knownmodel that has been tested over a variety of instrumented sites. The bias was first attributed to a deficient turbulent transfer and a few formulations were compared. One formulation is the classical log-linear profile with a sharp cut-off of the fluxes at a critical Richardsonnumber around 0.2, while in the other ones the flux decreases less rapidly with increasingstatic stability. While the surface-layer formulations have an impact on the modelled canopy temperature, other causes were found for the negative bias. The CLASS model neglected the heat capacity of the air trapped inside the canopy and its inclusion multiplied theeffective heat capacity of the canopy, by a factor ranging from 2.3 to 3.4 for the canopies studied, and reduced the error. A correction was also made to the air specific humidity at canopy level and the topsoil thermal conductivity was changed from that of organic matter to that of mineral soil. With these modifications, and using the incoming longwave radiative flux instead of the net longwave flux, the bias almost completely disappeared. Using ascheme with more heat transfer at large static stability, obtained by assuming that thefluxes decrease in magnitude with height in the surface layer, reduced the original biaswhile using the log-linear formulation amplified the cold bias. The impact of the turbulent transfer formulations is much reduced when they are applied to model runs in which the other above modifications have been made.The phenomenon of decoupling is presented and its understanding is complementedwith the new notions of `hard' versus `soft' decoupling and complete versus incompletedecoupling, depending on the impact decoupling has on the model and on the effectiveness of the model in achieving the decoupling. The geostrophic wind speed is a determiningfactor in separating cases of hard decoupling (rare) from the soft cases (frequent) while the completeness of the decoupling primarily depends on the form of the turbulent transfer curve as a function of static stability.  相似文献   

Milieux coralliens du Dogger près de Betioky (Madagascar) : la fin d'une exceptionCorallian meadows in the Dogger near Betioky (Madagascar): the end of an exception     

Bernard Lathuilire  Yves Almeras  Vincent Huault  Frdric Bouticourt  La-Jacqueline Raharijaona-Raharison 《Comptes Rendus Geoscience》2002,334(16)

Corallian outcrops of the Dogger in the Betioky area (Madagascar) have been previously interpreted as barrier reefs or atolls involved in a large carbonate platform. This statement appeared exceptional for these times. A field study demonstrates that, in fact, they are only sparse solitary or colonial corals, whose growth occurred with some difficulty. They developed in meadows strongly marked by terrigenous inputs, in a subsiding context, and during brief episodes favourable to the genesis of ooids. To cite this article: B. Lathuilière et al., C. R. Geoscience 334 (2002) 1169–1176.  相似文献   

Comment: Tephrochronological dating of varved interglacial lake deposits from Piànico‐Sèllere (Southern Alps,Italy) to around 400 ka. Achim Brauer,Sabine Wulf,Clara Mangili and Andrea Moscariello Journal of Quaternary Science 22: 85–96     

Daniele L. Pinti  Virgile Rouchon  Xavier Quidelleur  Pierre‐Yves Gillot  Sergio Chiesa  Cesare Ravazzi 《第四纪科学杂志》2007,22(4):411-414

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Interpretation of dilatometer tests in a heavy oil reservoir     

Christophe Dano  Pierre‐Yves Hicher  Damien Rangeard  Philippe Marchina 《国际地质力学数值与分析法杂志》2007,31(10):1197-1215

This paper presents a prospective study for identifying selected parameters of the modified Cam‐Clay model representing the behaviour of heavy oil reservoirs. The first part shows that the plastic compressibility, which controls the main recovery mechanism of such reservoirs, can be accurately determined, simultaneously with other parameters, by an inverse analysis of pressure–strain curves. The conditions of the identification procedure mainly involve two tests conducted under different drainage conditions or at different strain rates. The numerical study also establishes the sequence of an original in situ experimental program, in which three dilatometer tests at a relatively great depth (several hundreds of metres) were carried out. The comparison of the experimental data with the numerical computations reveals a significant over‐consolidation ratio which does not allow the plastic compressibility to be determined but supports the findings regarding the geological erosion of the site. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

PaleoNet: new software for building,evaluating and applying neural network based transfer functions in paleoecology     

Julien M. J. Racca  Robert Racca  Reinhard Pienitz  Yves T. Prairie 《Journal of Paleolimnology》2007,38(3):467-472

Transfer functions that implement organism–environment relationships are now commonly used for inferring past environmental conditions in paleoecology. Specific software for developing and evaluating commonly used modelling techniques such as Weighted averaging (WA), Weighted averaging partial least square (WA-PLS), Maximum likelihood (ML), and Modern analog technique (MAT) are available. A new software programme, PaleoNet, is now available for modelling organism–environment relationships which is specifically designed for the development and the evaluation of artificial neural network (ANN) based transfer functions in paleoecology. Here we present the main characteristics of this new software PaleoNet (User guide version 1.01) and discuss in more detail one of its specific features: the pruning.  相似文献   

Consequences of progressive eclogitization on crustal exhumation, a mechanical study     

Hugues Raimbourg  Laurent Jolivet  Yves Leroy 《Geophysical Journal International》2007,168(1):379-401

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Accuracy evaluation of weather data generation and disaggregation methods at finer timescales     

Bekele Debele  R. Srinivasan  J. Yves Parlange 《Advances in water resources》2007

Availability of weather data at finer timescales such as hourly is vital in the application of dynamic physical and biological models. In this study, we have examined the suitability of various approaches (deterministic periodic versus stochastic) of disaggregating daily weather data into hourly data in the Cedar Creek watershed, TX, USA. We found the cosine function suitable to disaggregate daily maximum and minimum temperatures and wind speed data into respective hourly data. We also used a common logarithmic equation to compute vapor pressures from temperature data, and hence relative humidity (the ratio between actual and saturated vapor pressures multiplied by 100). Disaggregation following uniform distribution of daily rainfall over 24 h did not reproduce most statistical parameters computed from observed hourly rainfall data onsite. Conversely, both stochastic models formulated based on univariate (Hyetos) and multivariate (MuDRain) processes mimicked the measured hourly rainfall distributions very well. Overall, we found the MuDRain model superior, compared to other models to disaggregate daily rainfall data into hourly data.  相似文献   

Impact of surface heterogeneity on a buoyancy-driven convective boundary layer in light winds     

Dominique Courault  Philippe Drobinski  Yves Brunet  Pierre Lacarrere  Charles Talbot 《Boundary-Layer Meteorology》2007,124(3):383-403

Land-use practices such as deforestation or agricultural management may affect regional climate, ecosystems and water resources. The present study investigates the impact of surface heterogeneity on the behaviour of the atmospheric boundary layer (ABL), at a typical spatial scale of 1 km. Large-eddy simulations, using an interactive soil–vegetation–atmosphere surface scheme, are performed to document the structure of the three-dimensional flow, as driven by buoyancy forces, over patchy terrain with different surface characteristics (roughness, soil moisture, temperature) on each individual patch. The patchy terrain consists of striped and chessboard patterns. The results show that the ABL strongly responds to the spatial configuration of surface heterogeneities. The stripe configuration made of two patches with different soil moisture contents generates the development of a quasi- two-dimensional inland breeze, whereas a three-dimensional divergent flow is induced by chessboard patterns. The feedback of such small-scale atmospheric circulations on the surface fluxes appears to be highly non-linear. The surface sensible and latent heat fluxes averaged over the 25-km² domain may vary by 5% with respect to the patch arrangement.  相似文献   

Rock conductivity and fractal nature of porosity     

Clotilde Ruffet  Yves Gueguen  Michel Darot 《地学学报》1991,3(3):265-275

While the d.c. electrical properties of a rock, through the volume conductivity, provide information on pore space structure (Formation factor) and pore fluid, the frequency dependence of the electrical parameters allows the characterization of the pore-matrix interfaces. To illustrate these properties, we present here some results of measurements performed on sedimentary rocks (Vosges and Fontainebleau sandstones). These samples have a classical electrical response, i.e. a ‘Cole and Cole’ frequency behaviour near a certain relaxation frequency and a low-frequency dispersion. We discuss some of the models that have been proposed in the past to explain this behaviour. It appears that most of them are valid near and above the relaxation frequency, but only Dissado and Hill's model seems to be satisfactory over the whole frequency range. The fractal nature of the interfaces, assumed in two of these models but appropriate only for one of them, could also be a convenient explanation for the frequency dependence.  相似文献