Late Permian–Middle Jurassic lithospheric thinning in Peru and Bolivia, and its bearing on Andean-age tectonics     

Thierry Sempere  Gabriel Carlier  Pierre Soler  Michel Fornari  Víctor Carlotto  Javier Jacay  Oscar Arispe  Didier Nraudeau  Jos Crdenas  Silvia Rosas  Nstor Jimnez 《Tectonophysics》2002,345(1-4)

Integrated studies and revisions of sedimentary basins and associated magmatism in Peru and Bolivia (8–22°S) show that this part of western Gondwana underwent rifting during the Late Permian–Middle Jurassic interval. Rifting started in central Peru in the Late Permian and propagated southwards into Bolivia until the Liassic/Dogger, along an axis that coincides with the present Eastern Cordillera. Southwest of this region, lithospheric thinning developed in the Early Jurassic and culminated in the Middle Jurassic, producing considerable subsidence in the Arequipa basin of southern Peru. This 110-Ma-long interval of lithospheric thinning ended 160 Ma with the onset of Malm–earliest Cretaceous partial rift inversion in the Eastern Cordillera area.The lithospheric heterogeneities inherited from these processes are likely to have largely influenced the distribution and features of younger compressional and/or transpressional deformations. In particular, the Altiplano plateau corresponds to a paleotectonic domain of “normal” lithospheric thickness that was bounded by two elongated areas underlain by thinned lithosphere. The high Eastern Cordillera of Peru and Bolivia results from Late Oligocene–Neogene intense inversion of the easternmost thinned area.  相似文献   

Multistage shortening in the Dauphiné zone (French Alps): the record of Alpine collision and implications for pre-Alpine restoration     

Thierry Dumont  Jean-Daniel Champagnac  Christian Crouzet  Philippe Rochat 《Swiss Journal of Geoscience》2008,101(1):89-110

Three-dimensional modelling tools are used with structural and palaeomagnetic analysis to constrain the tectonic history of part of the Dauphiné zone (external Western Alps). Four compressive events are identified, three of them being older than the latest Oligocene. Deformation D1 consists of W–SW directed folds in the Mesozoic cover of the study area. This event, better recorded in the central and southern Pelvoux massif, could be of Eocene age or older. Deformation D2 induced N-NW-oriented basement thrusting and affected the whole southern Dauphiné basement massifs south of the study area. The main compressional event in the study area (D3) was WNW oriented and occurred before 24 Ma under a thick tectonic load probably of Penninic nappes. The D2-D3 shift corresponds to a rapid transition from northward propagation of the Alpine collision directly driven by Africa-Europe convergence, to the onset of westward escape into the Western Alpine arc. This Oligocene change in the collisional regime is recorded in the whole Alpine realm, and led to the activation of the Insubric line. The last event (D4) is late Miocene in age and coeval with the final uplift of the Grandes Rousses and Belledonne external massifs. It produced strike-slip faulting and local rotations that significantly deformed earlier Alpine folds and thrusts, Tethyan fault blocks and Hercynian structures. 3D modelling of an initially horizontal surface, the interface between basement and Mesozoic cover, highlights large-scale basement involved asymmetric folding that is also detected using structural analysis. Both, Jurassic block faulting and basement fold-and-thrust shortening were strongly dependent on the orientation of Tethyan extension and Alpine shortening relative to the late Hercynian fabric. The latter’s reactivation in response to oblique Jurassic extension produced an en-échelon syn-rift fault pattern, best developed in the western, strongly foliated basement units. Its Alpine reactivation occurred with maximum efficiency during the early stages of lateral escape, with tectonic transport in the overlying units being sub-perpendicular to it.  相似文献   

A discrete spherical harmonics method for radiative transfer analysis in inhomogeneous polarized planar atmosphere     

Romuald Tapimo  Hervé Thierry Tagne Kamdem  David Yemele 《Astrophysics and Space Science》2018,363(3):52

A discrete spherical harmonics method is developed for the radiative transfer problem in inhomogeneous polarized planar atmosphere illuminated at the top by a collimated sunlight while the bottom reflects the radiation. The method expands both the Stokes vector and the phase matrix in a finite series of generalized spherical functions and the resulting vector radiative transfer equation is expressed in a set of polar directions. Hence, the polarized characteristics of the radiance within the atmosphere at any polar direction and azimuthal angle can be determined without linearization and/or interpolations. The spatial dependent of the problem is solved using the spectral Chebyshev method. The emergent and transmitted radiative intensity and the degree of polarization are predicted for both Rayleigh and Mie scattering. The discrete spherical harmonics method predictions for optical thin atmosphere using 36 streams are found in good agreement with benchmark literature results. The maximum deviation between the proposed method and literature results and for polar directions \(\vert \mu \vert \geq0.1 \) is less than 0.5% and 0.9% for the Rayleigh and Mie scattering, respectively. These deviations for directions close to zero are about 3% and 10% for Rayleigh and Mie scattering, respectively.  相似文献   

Benthic indicators and index approaches in the three main estuaries along the French Atlantic coast (Seine, Loire and Gironde)     

Jean-Claude Dauvin  Guy Bachelet  Anne-Laure Barillé  Hugues Blanchet  Xavier de Montaudouin  Nicolas Lavesque  & Thierry Ruellet 《Marine Ecology》2009,30(2):228-240

The three main estuaries in the French Atlantic coast – the Seine, Loire and Gironde, all with high tidal regimes – are interfaces between the continental and the coastal ecosystems. The Seine and Gironde are highly contaminated, whereas the Loire remains in a more natural state. Both the Seine and Gironde have suffered from harbour construction, and as a result, their biological units are extremely compartmentalized. Benthic species and communities have adapted to tolerate temporal physical and chemical changes ( e.g. salinity, substrata, depth, and levels of fine particles and oxygen) and human activities ( e.g. dredging, shipping traffic, and habitat reduction). Although numerous bio-indicators and indices are used to define the ecological quality status (EcoQS) of coastal waters, very few of them were developed specifically for environments with a mosaic of conditions and salinity levels, including freshwater. The main problem appears to be that all the indices for determining anthropogenic stress examine the abundances of stress-tolerant species, which may also be able to tolerate natural stressors such as those occurring in estuaries. This paper takes a look at the development status of the benthic indicators and index approaches used in the three main estuaries along the French Atlantic coast. In addition, it examines the adaptation of the different benthic indicators to the taxonomic sufficiency principle, and the adaptation of the Benthic Opportunistic Polychaetes Amphipods index (BOPA) and the Benthic Opportunistic Annelida Amphipod index (BO2A) for use in the freshwater zones of transitional waters ( i.e. up to the upper limit of the tidal range). Several perspectives are discussed in light of the diverse disturbances and the heterogeneity of such stressed zones, such as the use of multimetric and scoring approaches.  相似文献   

The effects of resolving the Canadian Arctic Archipelago in a finite element sea ice model   总被引：1，自引：0，他引：1  

Olivier Lietaer  Thierry Fichefet  Vincent Legat 《Ocean Modelling》2008,24(3-4):140-152

Though narrow straits may have a strong influence on the large-scale sea ice mass balance, they are often crudely represented in coarse resolution sea ice models. Unstructured meshes, with their natural ability to fit boundaries and locally increase the mesh resolution, propose an alternative framework to capture the complex oceanic areas formed by coasts and islands. In this paper, we develop a finite element sea ice model to investigate the sensitivity of the Arctic sea ice cover features to the resolution of the narrow straits constituting the Canadian Arctic Archipelago. The model is a two-level dynamic-thermodynamic sea ice model, including a viscous-plastic rheology. It is run over 1979–2005, forced by daily NCEP/NCAR reanalysis data. Confronting qualitatively numerical experiments with observations shows a good agreement with satellite and buoys measurements. Due to its simple representation of the oceanic interactions, the model overestimates the sea ice extent during winter in the southernmost parts of the Arctic, while the Baffin Bay and Kara Sea remain ice-covered during summer. In order to isolate the benefits from resolving the Canadian Arctic Archipelago, a numerical experiment is performed where we artificially close the archipelago. Focusing on the large-scale sea ice thickness pattern, no significant change is found in our model, except in the close surroundings of the archipelago. However, the local and short-term influences of the ice exchanges are nonnegligible. In particular, we show that the ice volume associated to the Canadian Arctic Archipelago represents 10% of the Northern Hemisphere sea ice volume and that the annual mean ice export towards Baffin Bay amounts to 125 km³ yr⁻¹, which may play an important role on the convective overturning in the Labrador Sea.  相似文献   

Tectonic shortening and gravitational spreading in the Gulf of Cadiz accretionary wedge: Observations from multi-beam bathymetry and seismic profiling     

Marc-André Gutscher  Stephane Dominguez  Graham K. Westbrook  Pascal Gente  Nathalie Babonneau  Thierry Mulder  Eliane Gonthier  Rafael Bartolome  Joaquim Luis  Filipe Rosas  Pedro Terrinha 《Marine and Petroleum Geology》2009,26(5):647-659

The Gulf of Cadiz lies astride the complex plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. We report on the results of recent bathymetric swathmapping and multi-channel seismic surveys carried out here. The seafloor is marked by contrasting morphological provinces, spanning the SW Iberian and NW Moroccan continental margins, abyssal plains and an elongate, arcuate, accretionary wedge. A wide variety of tectonic and gravitational processes appear to have shaped these structures. Active compressional deformation of the wedge is suggested by folding and thrusting of the frontal sedimentary layers as well as basal duplexing in deeper internal units. There is evidence for simultaneous gravitational spreading occurring upslope. The very shallow mean surface and basal slopes of the accretionary wedge (1° each) indicate a very weak decollement layer, geometrically similar to the Mediterranean Ridge accretionary complex. Locally steep slopes (up to 10°) indicate strongly focused, active deformation and potential gravitational instabilities. The unusual surface morphology of the upper accretionary wedge includes “raft-tectonics” type fissures and abundant sub-circular depressions. Dissolution and/or diapiric processes are proposed to be involved in the formation of these depressions.  相似文献   

Seasonal Sensitivity on COBEL-ISBA Local Forecast System for Fog and Low Clouds     

Stevie Roquelaure  Thierry Bergot 《Pure and Applied Geophysics》2007,164(6-7):1283-1301

Skillful low visibility forecasts are essential for air-traffic managers to effectively regulate traffic and to optimize air-traffic control at international airports. For this purpose, the COBEL-ISBA local numerical forecast system has been implemented at Paris CDG international airport. This local approach is robust owing to the assimilation of detailed local observations. However, even with dedicated observations and initialization, uncertainties remain in both initial conditions and mesoscale forcings. The goal of the research presented here is to address the sensitivity of COBEL-ISBA forecast to initial conditions and mesoscale forcings during the winter season 2002–2003. The main sources of uncertainty of COBEL-ISBA input parameters have been estimated and the evaluation of parameter uncertainty on the forecasts has been studied. A budget strategy is applied during the winter season to quantify COBEL-ISBA sensitivity. This study is the first step toward building a local ensemble prediction system based on COBEL-ISBA. The conclusions of this work point out the potential for COBEL-ISBA ensemble forecasting and quantify sources of uncertainty that lead to dispersion.  相似文献   

Pollution au plomb dans la Savoie antique (II–IIIe s. apr. J.-C.) en relation avec une installation métallurgique de la cité de Vienne     

Fabien Arnaud  Joël Serralongue  Thierry Winiarski  Marc Desmet  Martine Paterne 《Comptes Rendus Geoscience》2006,338(4):244-252

In Lake Anterne (NW French Alps), the Roman period is characterised by a lead contamination more important than that of the 1970s, due to the use of leaded gasoline. The maximum of this contamination period has been varve-dated 220 AD, i.e., during the optimum of Roman civilization in the Alps. Crossing palaeoenvironmental and archaeological evidences points out the economic importance of the town of Passy for the City of Vienne and yields a new example of lead contamination due to local metallurgical activity rather than distant impact of the exploitation of the Spanish Rio Tinto mine. To cite this article: F. Arnaud et al., C. R. Geoscience 338 (2005).  相似文献   

应用多种数据融合方法对多时相SPOT图像处理提取三峡工程大坝区地面动态变化信息     

杨武年  Thierry Ranchin 《物探化探计算技术》2005,27(3):267-273

三峡库区三斗坪大坝区及其周围地区在1994到1998年期间，由于大坝的施工地面发生了巨大变化。这些变化在1990、1997和1998年获取的SPOT遥感图像上都有明显的记录，其中一些地面变化细节在分辨率10m的全波段（P）图像更为清楚。这里利用三种方法（高通滤波算法（HPF algorithm，Chavezet al．1991）、RWM—ARSIS方法（Ranchin and Wald，1999）和P＋XS算法（Anonymous 1986））对三峡工程三斗坪大坝区的多时相高空间分辨率的SPOT图像（获取时闻为1990，1997和1998年，包括全波段P图像和多波段XS图像）进行融合处理，在提取测区地面动态变化信息的同时，从理论和实际应用的角度探讨了不同数据融合方法的效果。  相似文献   

Integrating diverse geologic and geodetic observations to determine failure mechanisms and deformation rates across a large bedrock landslide complex: the Osmundneset landslide,Sogn og Fjordane,Norway     

Adam M. Booth  John Dehls  Trond Eiken  Luzia Fischer  Reginald L. Hermanns  Thierry Oppikofer 《Landslides》2015,12(4):745-756

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