Ordovician magmatism in the Lévézou massif (French Massif Central): tectonic and geodynamic implications     

Lotout  Caroline  Pitra  Pavel  Poujol  Marc  Van Den Driessche  Jean 《International Journal of Earth Sciences》2017,106(2):501-515

International Journal of Earth Sciences - New U–Pb dating on zircon yielded ca. 470 Ma ages for the granitoids from the Lévézou massif in the southern French Massif...  相似文献   

Two-stage partial melting during the Variscan extensional tectonics (Montagne Noire,France)     

Poujol  Marc  Pitra  Pavel  Van Den Driessche  Jean  Tartèse  Romain  Ruffet  Gilles  Paquette  Jean-Louis  Poilvet  Jean-Charles 《International Journal of Earth Sciences》2017,106(2):477-500

International Journal of Earth Sciences - One of the striking features that characterise the late stages of the Variscan orogeny is the development of gneiss and migmatite domes, as well as...  相似文献   

The socio-economic impact of sea-level rise on the Netherlands: A study of possible scenarios     

M. G. J. Den Elzen  J. Rotmans 《Climatic change》1992,20(3):169-195

This paper describes a simulation study of some of the socio-economic consequences of a rise in sea level on Dutch society. A computer simulation model for the greenhouse problem has been developed, which tries to capture the climate change cause-effect relationship for a combination of greenhouse-gas emissions. The impact of emissions of greenhouse gases on global temperature and sea-level rise can be calculated using the model. Additionally, separate, independent modules have been implemented in order to quantify the socio-economic consequences for the Netherlands. Four consistent sets of scenarios have been developed, based on differences in economic growth, energy use, international environmental measures, etc. On the basis of these scenarios estimates are made of the costs of coastal defence and water management in the Netherlands as a result of adaptation to the impacts of sea-level rise.  相似文献   

宝钢引水库大坝水平位移监测评价和变形分析     

张正禄  邓克寰 《武汉大学学报(信息科学版)》1992,(4)

本文对宝钢引水库大坝的水平位移监测网的布设方案,采用灵敏度和可靠性准则进行了网的优化设计计算,从监测网的质量准则出发,对布网方案作了若干探讨。从二十五期观测资料中选出十三期进行了水平位移计算和变形的几何分析。指出,在变形分析中正确选取基准的重要意义和据多期位移值进行变形预报的一些方法,并定性地讨论了该大坝变形的物理解释。本文所作的工作对类似大坝的水平位移监测和成果处理具有实际意义。  相似文献   

On The Temperature-Humidity Correlation And Similarity   总被引：5，自引：3，他引：2  

H. A. R. De Bruin  B. J. J. M. Van Den Hurk  L. J. M. Kroon 《Boundary-Layer Meteorology》1999,93(3):453-468

The correlation coefficient between temperature and specific humidity (r_Tq) is considered. A brief literature review as well as experimental data reveals that there is evidence that the eddy diffusivities for heat and water vapour are not equal if |r_Tq| 1. Several conditions under which this can occur are discussed. It is concluded that if non-local effects are of the same order as local effects T and q will behave in a non-similar fashion. Moreover, it is shown that if |r_Tq| = 1, temperature and specific humidity both will obey Monin–Obukhov similarity. In addition, based on that derivation, a new method is presented to determine the Bowen ratio from the T - q correlation. A first test of this new Bowen ratio regression method is presented. It is recommended to use r_Tq as a diagnostic tool to judge whether T-q similarity holds.  相似文献   

The importance of breaching as a mechanism of subaqueous slope failure in fine sand   总被引：1，自引：1，他引：1  

Jan H. Van Den Berg  ré Van Gelder  & Dick R. Mastbergen† 《Sedimentology》2002,49(1):81-95

Large bank failures, comprising up to 10⁶ m³ of sediment, are common features along steep channel banks in estuaries and large rivers that consist of clean, fine sands, and are mostly assumed to be generated by sudden liquefaction of large masses of very loosely packed sand. Another less commonly recognized type of failure is manifested by the gradual retrogression of a very steep wall, steeper than the angle-of-repose. Instead of the voluminous surging plastic sediment-water flow, or hyperconcentrated density flow (sensu Mulder & Alexander, 2001 ) generated by liquefaction, this type of failure, known as breaching by dredging companies and hydraulic engineers, produces a sustained quasi-steady, turbidity current. To date, sedimentologists have not recognized the process of breaching as such. In this paper, it is suggested that breaching may be the origin of many thick, massive sand layers known from ancient deposits from various environments, notably in some turbidite successions. Possible differences in the sedimentary structure of the deposits produced by breach failures vs. liquefaction slope failures (=liquefaction flow slides) can be deduced from a knowledge of the sediment transport processes initiated by the failure. A field study is presented on some poorly structured beds in the Eocene Vlierzele Sands in Belgium, which are supposed to have originated from liquefaction failures, but are reinterpreted to be the products of breaching. It is postulated that the local steep slope disturbance required to initiate an active breach can be produced by a small liquefaction slope failure (=liquefaction flow slide failure) or local erosion by river or tidal channel flow at the initial stage of the failure event.  相似文献   

L'érosion des chaînes de montagnes : influence de la sédimentation de piedmont     

Julien Babault  Jean Van Den Driessche   《Comptes Rendus Geoscience》2005,337(16):1431

The applanation of mountain belts that results in peneplain is generally considered to be caused by the long-term activity of erosion. Peneplanation has been previously defined as the lowering of an elevated topography and the concomitant subduing of its relief. We propose a model following which piedmont sedimentation induces the base level rise, allowing applanation to develop at high elevation and resulting in an elevated ‘peneplain’. This model is illustrated by the morphological evolution of the southern flank of the Pyrenees during the Cainozoic. To cite this article: J. Babault, J. Van Den Driessche, C. R. Geoscience 337 (2005).  相似文献   

鲁西中生代富钾火山岩及煌斑岩微量元素和Nd—Sr同位素地球化学   总被引：33，自引：1，他引：33  

邱检生 McI.  BIA 《高校地质学报》1997,3(4):384-385

鲁西中生代富钾火山岩产于断陷型陆相火山岩盆地中，煌斑岩多位于火山岩盘地的外圈。二者形成时代相近，产出的构造背景相同，在主量元素、微量元素和Nd－Sr同位索等特征上极为相似，均表现出富碱富钾、富轻稀土及大离于亲石元素和贫高场强元素及亲铁元素的特点，并具有显著偏低的εNd值和明显偏高的Isr值。研究结果表明，富钾火山岩和煌斑岩均起源于富集型地幔的部分熔融。  相似文献   

米仓山区盖层褶皱构造变形分析   总被引：10，自引：0，他引：10  

邓明森 《矿物岩石》1997,(Z1)

通过１∶５万区域地质调查和构造研究，首次提出米仓山区构造模式是在印支期到喜马拉雅期秦岭造山、四川成盆的山－盆耦合作用动力学和区内岩石力学性质差异分层结构的地质背景下，经历主波长－接触应变褶皱之后，通过断展褶皱作用以先成褶皱包络面和盖层底部角度不整合面为褶皱变形面形成的一个巨型不协调背斜构造。充实并运用主波长理论公式估算了褶皱作用期间的有关参数。建立了区域构造两类四型五阶段演化模式。  相似文献   

Prediction of landslide susceptibility using rare events logistic regression: A case-study in the Flemish Ardennes (Belgium)   总被引：9，自引：8，他引：9  

M. Van Den Eeckhaut  T. Vanwalleghem  J. Poesen  G. Govers  G. Verstraeten  L. Vandekerckhove 《Geomorphology》2006,76(3-4):392-410

In this article a statistical multivariate method, i.e., rare events logistic regression, is evaluated for the creation of a landslide susceptibility map in a 200 km² study area of the Flemish Ardennes (Belgium). The methodology is based on the hypothesis that future landslides will have the same causal factors as the landslides initiated in the past. The information on the past landslides comes from a landslide inventory map obtained by detailed field surveys and by the analysis of LIDAR (Light Detection and Ranging)-derived hillshade maps. Information on the causal factors (e.g., slope gradient, aspect, lithology, and soil drainage) was extracted from digital elevation models derived from LIDAR and from topographical, lithological and soil maps. In landslide-affected areas, however, we did not use the present-day hillslope gradient. In order to reflect the hillslope condition prior to landsliding, the pre-landslide hillslope was reconstructed and its gradient was used in the analysis. Because of their limited spatial occurrence, the landslides in the study area can be regarded as “rare events”. Rare events logistic regression differs from ordinary logistic regression because it takes into account the low proportion of 1s (landslides) to 0s (no landslides) in the study area by incorporating three correction measures: the endogenous stratified sampling of the dataset, the prior correction of the intercept and the correction of the probabilities to include the estimation uncertainty. For the study area, significant model results were obtained, with pre-landslide hillslope gradient and three different clayey lithologies being important predictor variables. Receiver Operating Characteristic (ROC) curves and the Kappa index were used to validate the model. Both show a good agreement between the observed and predicted values of the validation dataset. Based on a qualified judgement, the created landslide susceptibility map was classified into four classes, i.e., very high, high, moderate and low susceptibility. If interpreted correctly, this classified susceptibility map is an important tool for the delineation of zones where prevention measures are needed and human interference should be limited in order to avoid property damage due to landslides.  相似文献