Greater India Basin Hypothesis and A Two-Stage Cenozoic Collision Between India and Asia     

Douwe VAN HINSBERGEN  Lippert Peter  Dupont-Nivet Guillaume  McQuarrie Nadine  Doubrovine Pavel  Spakman Wim  Torsvik Trond 《《地质学报》英文版》2013,87(Z1):15-15

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Effect of particle density and inflow concentration of suspended sediment on bedload transport in rill flow     

Guillaume Nord  Michel Esteves    Jean‐Marc Lapetite  Alexandre Hauet 《地球表面变化过程与地形》2009,34(2):253-263

Laboratory flume experiments were carried out to evaluate the effect of particle density on bedload transport of sand‐sized particles and the effect of a suspended load of clay particles (kaolinite) on bedload transport of sand‐sized particles in rill flow conditions. Three materials in the range 400–600 µm were selected to simulate bedload transport of primary particles and aggregates: sand (2650 kg/m³), crushed brick (2450 kg/m³) and anthracite (1300–1700 kg/m³). In the two first experiments, two different methods were applied to determine bedload transport capacity of coarse particles for various conditions of flow discharge (from 2 to 15 L/min) and slope (2.2, 3 and 4%). In the third experiment, clear water was replaced with kaolinite–water mixture and bedload transport capacity of crushed brick particles was determined for a 4% slope and different concentrations of kaolinite (0, 7, 41 and 84 g/L). The results showed that bedload transport increased significantly with the decrease in particle density but the effect of particle density on transport rates was much less important than flow discharge. Velocity measurements of clear flow, flow mixed with coarse particles and coarse particles confirmed the existence of a differentiation between suspended load and bedload. In these experimental conditions, suspended load of kaolinite did not affect bedload rates of crushed brick particles. Three transport capacity formulae were tested against observed bedload rates. A calibration of the Foster formula revealed that the shear stress exponent should be greater than 1.5. The Low and the Govers unit stream power (USP) equations were then evaluated. The Low equation was preferred for the prediction of bedload rates of primary particles but it was not recommended in the case of aggregates of low density because of the limited experimental conditions applied to derive this equation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Deterministic sensitivity analysis for a model for flow in porous media     

Estelle Marchand  François Clément  Jean E. Roberts  Guillaume Pépin 《Advances in water resources》2008

A deterministic method for sensitivity analysis is developed and applied to a mathematical model for the simulation of flow in porous media. The method is based on the singular value decomposition (SVD) of the Jacobian matrix of the model. It is a local approach to sensitivity analysis providing a hierarchical classification of the directions in both the input space and of those in the output space reflecting the degree of sensitiveness of the latter to the former. Its low computational cost, in comparison with that of statistical approaches, allows the study of the variability of the results of the sensitivity analysis due to the variations of the input parameters of the model, and thus it can provide a quality criterion for the validity of more classical probabilistic global approaches. For the example treated here, however, this variability is weak, and deterministic and statistical methods yield similar sensitivity results.  相似文献   

The snowball Earth aftermath: Exploring the limits of continental weathering processes     

Guillaume Le Hir  Yannick Donnadieu  Yves Goddéris  Raymond T. Pierrehumbert  Galen P. Halverson  Mélina Macouin  Anne Nédélec  Gilles Ramstein 《Earth and Planetary Science Letters》2009,277(3-4):453-463

Carbonates capping Neoproterozoic glacial deposits contain peculiar sedimentological features and geochemical anomalies ascribed to extraordinary environmental conditions in the snowball Earth aftermath. It is commonly assumed that post-snowball climate dominated by CO₂ partial pressures several hundred times greater than modern levels, would be characterized by extreme temperatures, a vigorous hydrological cycle, and associated high continental weathering rates. However, the climate in the aftermath of a global glaciation has never been rigorously modelled. Here, we use a hierarchy of numerical models, from an atmospheric general circulation model to a mechanistic model describing continental weathering processes, to explore characteristics of the Earth system during the supergreenhouse climate following a snowball glaciation. These models suggest that the hydrological cycle intensifies only moderately in response to the elevated greenhouse. Indeed, constraints imposed by the surface energy budget sharply limit global mean evaporation once the temperature has warmed sufficiently that the evaporation approaches the total absorbed solar radiation. Even at 400 times the present day pressure of atmospheric CO₂, continental runoff is only 1.2 times the modern runoff. Under these conditions and accounting for the grinding of the continental surface by the ice sheet during the snowball event, the simulated maximum discharge of dissolved elements from continental weathering into the ocean is approximately 10 times greater than the modern flux. Consequently, it takes millions of years for the silicate weathering cycle to reduce post-snowball CO₂ levels to background Neoproterozoic levels. Regarding the origin of the cap dolostones, we show that continental weathering alone does not supply enough cations during the snowball melting phase to account for their observed volume.  相似文献   

Polarization effects of seismic waves on the basis of radiative transport theory     

Guillaume Bal  & Miguel Moscoso 《Geophysical Journal International》2000,142(2):571-585

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Numerical modelling of stream–aquifer interaction: Quantifying the impact of transient streambed permeability and aquifer heterogeneity          下载免费PDF全文

Dan Zhou  Ye Zhang  Guillaume Gianni  Peter Lichtner  Irina Engelhardt 《水文研究》2018,32(14):2279-2292

Stream–aquifer interaction plays a vital role in the water cycle, and a proper study of this interaction is needed for understanding groundwater recharge, contaminants migration, and for managing surface water and groundwater resources. A model‐based investigation of a field experiment in a riparian zone of the Schwarzbach river, a tributary of the Rhine River in Germany, was conducted to understand stream–aquifer interaction under alternative gaining and losing streamflow conditions. An equivalent streambed permeability, estimated by inverting aquifer responses to flood waves, shows that streambed permeability increased during infiltration of stream water to aquifer and decreased during exfiltration. Aquifer permeability realizations generated by multiple‐point geostatistics exhibit a high degree of heterogeneity and anisotropy. A coupled surface water groundwater flow model was developed incorporating the time‐varying streambed permeability and heterogeneous aquifer permeability realizations. The model was able to reproduce varying pressure heads at two observation wells near the stream over a period of 55 days. A Monte Carlo analysis was also carried out to simulate groundwater flow, its age distribution, and the release of a hypothetical wastewater plume into the aquifer from the stream. Results of this uncertainty analysis suggest (a) stream–aquifer exchange flux during the infiltration periods was constrained by aquifer permeability; (b) during exfiltration, this flux was constrained by the reduced streambed permeability; (c) the effect of temporally variable streambed permeability and aquifer heterogeneity were found important to improve the accurate capture of the uncertainty; and (d) probabilistic infiltration paths in the aquifer reveal that such pathways and the associated prediction of the extent of the contaminant plume are highly dependent on aquifer heterogeneity.  相似文献   

Palaeomagnetism of the Permian Volcanic Rocks of Moissey (French Jura): Implications For the Palaeofield and Tectonic Evolution     

J. F. C. Thompson  A. Guillaume  L. Daly 《Geophysical Journal International》1986,86(1):103-117

Rocks from the Massif de la Serre in the French Jura (latitude: 47.3°N longitude: 5.6°E) belonging to an ignimbritic assemblage dominated by vitrophyric rhyolites, and whose age of formation is probably Permian (Autunian to Saxonian) have been studied by applying thermal and alternating field demagnetization. the characteristic magnetization has a mean direction derived from 89 samples of D= 170°, I = - 16°, k = 26.2°, α₉₅= 3° and a corresponding north palaeopole at 41°N, 172°E, A ₉₅= 5°. the pole, which is very close to the Permian European poles, can thus be considered as a new contribution. Some samples are found to carry a unique normal polarity magnetization, others carry both normal and reverse polarities. It therefore seems that, similar to Permian series in the USSR, these west European rocks have registered a normal event in the Kiaman interval. From a structural point of view, we may conclude that during the Alpine tectonic phases the Massif de la Serre has not been subjected to substantial rotation.  相似文献   

Co-use of existing scenario sets to extend and quantify the shared socioeconomic pathways     

Guillaume Rohat  Johannes Flacke  Hy Dao  Martin van Maarseveen 《Climatic change》2018,151(3-4):619-636

More often than not, assessments of future climate risks are based on future climatic conditions superimposed on current socioeconomic conditions only. The new IPCC-guided alternative global development trends, the shared socioeconomic pathways (SSPs), have the potential to enhance the integration of future socioeconomic conditions—in the form of socioeconomic scenarios—within assessments of future climate risks. Being global development pathways, the SSPs lack regional and sectoral details. To increase their suitability in sectoral and/or regional studies and their relevance for local stakeholders, the SSPs have to be extended. We propose here a new method to extend the SSPs that makes use of existing scenario studies, the (re)use of which has been underestimated so far. Our approach lies in a systematic matching of multiple scenario sets that facilitates enrichment of the global SSPs with regional and sectoral information, in terms of both storylines and quantitative projections. We apply this method to develop extended SSPs of human vulnerability in Europe and to quantify them for a number of key indicators at the sub-national level up to 2050, based on the co-use of the matched scenarios’ quantitative outputs. Results show that such a method leads to internally consistent extended SSPs with detailed and highly quantified narratives that are tightly linked to global contexts. This method also provides multiple entry points where the relevance of scenarios to local stakeholders can be tested and strengthened. The extended SSPs can be readily employed to explore future populations’ vulnerability to climate hazards under varying levels of socioeconomic development.  相似文献   

Anharmonicity and high-temperature heat capacity of crystals: the examples of Ca2GeO4, Mg2GeO4 and CaMgGeO4 olivines     

Guillaume Fiquet  Philippe Gillet  Pascal Richet 《Physics and Chemistry of Minerals》1992,18(7):469-479

Drop-calorimetry determinations of the isobaric heat capacity (C_P) of Mg₂GeO₄, Ca₂GeO₄ and CaMgGeO₄ have been made up to 1700 K. The thermal expansion coefficient (α) of these olivine germanates has been determined from high-temperature X-ray measurements up to 1500 K. From these measurements and available compressibility data, one calculates that the isochoric heat capacity (C_V) exceeds the harmonic limit of Dulong and Petit above 1000–1200 K. Such an intrinsic anharmonic behaviour can be accounted for by introducing anharmonic parameters a_i=(? ln v _i/?T)_V in vibrational modelling of C_V. These parameters are calculated from pressure and temperature shifts of the vibrational frequencies as measured by Raman spectroscopy up to 10 GPa at room temperature and up to 1300 K at 1 bar. A comparison of the Raman spectra of the three germanates with those of natural olivines justifies once again the use of germanates as silicate analogues. Extensive Ca,Mg disordering likely takes place in CaMgGeO₄, beginning at about 1100 K and leading to unusually high increases of the heat capacity and thermal expansion coefficient.  相似文献   

Information infrastructure for Australia’s Integrated Marine Observing System     

Marton G. Hidas  Roger Proctor  Natalia Atkins  Julian Atkinson  Laurent Besnard  Peter Blain  Philip Bohm  Jon Burgess  Kim Finney  Dan Fruehauf  Guillaume Galibert  Xavier Hoenner  Jacqui Hope  Craig Jones  Sebastien Mancini  Benedicte Pasquer  David Nahodil  Kate Reid  Katherine Tattersall 《Earth Science Informatics》2016,9(4):525-534

Australia’s Integrated Marine Observing System (IMOS, imos.org.au) is research infrastructure to establish an enduring observing program for Australian oceanic waters and shelf seas. The observations cover physical, biological, and chemical variables to address themes of multi-decadal ocean change, climate variability and weather extremes, boundary currents and inter-basin flows, continental shelf processes and ecosystem responses.IMOS observations are collected by national facilities based on various platform types and operated by partner institutions around the country. In this paper we describe the infrastructure and workflows developed to manage and distribute the data to the public. We highlight the existing standards and open-source software we have adopted, and the contributions we have made. To demonstrate the value of this infrastructure we provide some illustrations of use and uptake.All IMOS data are freely and openly available to the public via the Ocean Portal (https://imos.aodn.org.au). All IMOS-developed software is open-source and accessible at https://github.com/aodn.  相似文献