The fit of the continents around the North Atlantic Ocean     

Xavier Le Pichon  Jean-Claude Sibuet  Jean Francheteau 《Tectonophysics》1977,38(3-4)

A new reassembly of the continents around the North Atlantic Ocean is presented. The first criterion used for this reassembly is the identification of the structural framework related to the opening which consists of marginal fracture zones generated by offsets of the Rift. The Africa—North America, Eurasia—Greenland, Greenland—North America and Eurasia—North America adjustments are successively discussed. It is argued that the adjustments are best made at the 3000-meters isobath between Africa and North America and at the 2000-meters isobath for the younger rifts. The difference is attributed to subsidence and modification of continental margins with time. The importance of the Late Paleozoic tectonic phase in determining the subsequent pattern of Mesozoic rifting is emphasized.  相似文献   

ACMEG‐TS: A constitutive model for unsaturated soils under non‐isothermal conditions     

Bertrand François  Lyesse Laloui 《国际地质力学数值与分析法杂志》2008,32(16):1955-1988

This paper introduces an unconventional constitutive model for soils, which deals with a unified thermo‐mechanical modelling for unsaturated soils. The relevant temperature and suction effects are studied in light of elasto‐plasticity. A generalized effective stress framework is adopted, which includes a number of intrinsic thermo‐hydro‐mechanical connections, to represent the stress state in the soil. Two coupled constitutive aspects are used to fully describe the non‐isothermal behaviour. The mechanical constitutive part is built on the concepts of bounding surface theory and multi‐mechanism plasticity, whereas water retention characteristics are described using elasto‐plasticity to reproduce the hysteretic response and the effect of temperature and dry density on retention properties. The theoretical formulation is supported by comparisons with experimental results on two compacted clays. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Multiscale approach to geo‐composite cellular structures subjected to rock impacts     

François Nicot  Philippe Gotteland  David Bertrand  Stéphane Lambert 《国际地质力学数值与分析法杂志》2007,31(13):1477-1515

Geo‐composite cellular structures are an efficient technological solution for various applications in civil engineering. This type of structure is particularly well adapted to resisting rockfalls and can act as a defensive structure. However, the design of such structures is for the most part empirically based; this lack of research‐based design stagnates optimization and advanced development. In this paper, the mechanical behaviour of a geo‐composite cellular structure is investigated using a multi‐scale approach, from the individual cell made up of an assembly of rocky particles contained in a wire netting cage to the entire structure composed of a regular array of cells. Based on discrete modelling of both the cell and structure scales, a computational tool has been developed for design purposes. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Deep seismic reflection and refraction profiling along the Aquitaine shelf (Bay of Biscay)   总被引：2，自引：0，他引：2  

Bertrand Pinet  Lucien Montadert  ECORS Scientific Party 《Geophysical Journal International》1987,89(1):305-312

Summary. The 300 km ECORS - Bay of Biscay profile was carried out along the Aquitaine shelf and comprised a complete set of experiments including zero-offset and 7.5 km constant offset vertical seismic reflection and six expanding spread profiles. Large offset recordings were fundamental for the definition of the layered lower crust and the Moho, while ESPs provided decisive complementary information for the geological interpretation. These data show a strong variation in crustal thickness from about 20 km beneath the rifted Parentis basin, a failed arm of the oceanic Bay of Biscay, up to 35 km to the north below the Armorican shelf, in the Hercynian domain, and to the south below the Cantabria shelf, in the vicinity of the Pyrenean deformation front. The results have important implications for the behaviour of the crust during the formation of rifted sedimentary basins and during continental collision.  相似文献   

Chondrules in CK carbonaceous chondrites and thermal history of the CV–CK parent body          下载免费PDF全文

Noël Chaumard  Bertrand Devouard 《Meteoritics & planetary science》2016,51(3):547-573

CK chondrites are the only group of carbonaceous chondrites with petrologic types ranging from 3 to 6. It is commonly reported than ~15 vol% of CK4–6 samples are composed of chondrules. The modal abundance of chondrules estimated here for 18 CK3–6 (including five CK3s) ranges from zero (totally recrystallized) to 50.5%. Although almost all chemically re‐equilibrated with the host matrix, we recognized in CK3s and Tanezrouft (Tnz) 057 (CK4) up to 85% of chondrules as former type I chondrules. Mean diameters of chondrules range from 0.22 to 1.05 mm for Karoonda (CK4) and Tnz 057 (CK4), respectively. Up to ~60% of chondrules in CK3–4 are surrounded by igneous rims (from ~20 μm to 2 mm width). Zoned olivines were found in unequilibrated chondrules from DaG 431 (CK3‐an), NWA 4724 (CK3.8), NWA 4423 (CK3.9), and Tnz 057 (CK4). We modeled Fe/Mg interdiffusion profiles measured in zoned olivines to evaluate the peak metamorphic temperatures and time scales of the CK parent body metamorphism, and proposed a two‐stage diffusion process in order to account for the position of inflection points situated within chondrules. Time scales inferred from Fe/Mg interdiffusion in olivine from unequilibrated chondrules are on the order of tens to a hundred thousand years (from 50 to 70,000 years for peak metamorphic temperatures of 1140 and 920 K, respectively). These durations are longer than what is commonly accepted for shock metamorphism and shorter than what is required for nuclide decay. Using the concept of a continuous CV–CK metamorphic series, which is reinforced by this study, we estimated peak metamorphic temperatures <850 K for CV, 850–920 K for CK3, and 920–1140 K for CK4–6 chondrites considering a duration of 70,000 years.  相似文献   

Paradox of estuarine quality: benthic indicators and indices, consensus or debate for the future     

Dauvin JC 《Marine pollution bulletin》2007,55(1-6):271-281

The European Water Framework Directive will have instituted the concept of Ecological Quality Status (EQS) as a way to assess the biological quality of water masses. The EQS will be based mainly upon the composition of the different biological compartments in the ecosystem specially the benthos as compared to certain reference sites. Such management tools are already well established for freshwater (i.e. biotic indices), but not for coastal and estuarine (i.e. transitional) waters. In the framework of the Seine-Aval programme a workshop on benthic indicators was organized at Wimereux (France) in June 2005. The aim of this workshop and this paper is (1) to present the experiences of the Seine Aval researchers, and the French scientific approaches to benthic indicators, with those international experiences and approaches that have been published or are under development; and (2) to examine the existing benthic tools and their possible use in the characterization of the state of estuarine ecosystems. The debate during the workshop and the numerous recently published on the WFD are discussed in term of the implementation of the WFD in transitional water bodies using benthic indicators and indices. Some proposals for the future underline the needs to re-examine and adapt the different index thresholds, to take into account physical disturbances, to inventory the existing conditions vs reference conditions and to be as pragmatic as possible in using the WFD in transitional waters.  相似文献   

The ecological quality status of the Bay of Seine and the Seine estuary: use of biotic indices     

Dauvin JC  Ruellet T  Desroy N  Janson AL 《Marine pollution bulletin》2007,55(1-6):241-257

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Establishing constraints on groundwater ages with Cl,C, H,and noble gases: A case study in the eastern Paris basin,France     

Véronique Lavastre  Corinne Le Gal La Salle  Jean-Luc Michelot  Sophie Giannesini  Lucilla Benedetti  Joël Lancelot  Bernard Lavielle  Marc Massault  Bertrand Thomas  Eric Gilabert  Didier Bourlès  Norbert Clauer  Pierre Agrinier 《Applied Geochemistry》2010

Groundwaters from the Tithonian/Kimmeridgian, Oxfordian and Upper Dogger aquifers, within the eastern part of the Paris basin (France), were characterised using ³H, ¹⁴C and ³⁶Cl, and noble gases tracers, to evaluate their residence times and determine their recharge period. This information is an important prerequisite to evaluating the confinement properties of the Callovo-Oxfordian clay formation sandwiched between the Oxfordian aquifer and the Dogger aquifer, currently being investigated by the French nuclear waste management agency (Andra) for radioactive waste disposal. Data presented in this paper are used to test 4 hypotheses.  相似文献   

Erratum to “Establishing constraints on groundwater ages with Cl,C, H,and noble gases: A case study in the eastern Paris basin,France” [Applied Geochemistry 25 (1) (2010) 123–142]     

Véronique Lavastre  Corinne Le Gal La Salle  Jean-Luc Michelot  Sophie Giannesini  Lucilla Benedetti  Joël Lancelot  Bernard Lavielle  Marc Massault  Bertrand Thomas  Eric Gilabert  Didier Bourlès  Norbert Clauer  Pierre Agrinier 《Applied Geochemistry》2010

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Comparing seven candidate mission configurations for temporal gravity field retrieval through full-scale numerical simulation   总被引：3，自引：2，他引：1  

Basem Elsaka  Jean-Claude Raimondo  Phillip Brieden  Tilo Reubelt  Jürgen Kusche  Frank Flechtner  Siavash Iran Pour  Nico Sneeuw  Jürgen Müller 《Journal of Geodesy》2014,88(1):31-43

The goal of this contribution is to focus on improving the quality of gravity field models in the form of spherical harmonic representation via alternative configuration scenarios applied in future gravimetric satellite missions. We performed full-scale simulations of various mission scenarios within the frame work of the German joint research project “Concepts for future gravity field satellite missions” as part of the Geotechnologies Program, funded by the German Federal Ministry of Education and Research and the German Research Foundation. In contrast to most previous simulation studies including our own previous work, we extended the simulated time span from one to three consecutive months to improve the robustness of the assessed performance. New is that we performed simulations for seven dedicated satellite configurations in addition to the GRACE scenario, serving as a reference baseline. These scenarios include a “GRACE Follow-on” mission (with some modifications to the currently implemented GRACE-FO mission), and an in-line “Bender” mission, in addition to five mission scenarios that include additional cross-track and radial information. Our results clearly confirm the benefit of radial and cross-track measurement information compared to the GRACE along-track observable: the gravity fields recovered from the related alternative mission scenarios are superior in terms of error level and error isotropy. In fact, one of our main findings is that although the noise levels achievable with the particular configurations do vary between the simulated months, their order of performance remains the same. Our findings show also that the advanced pendulums provide the best performance of the investigated single formations, however an accuracy reduced by about 2–4 times in the important long-wavelength part of the spectrum (for spherical harmonic degrees ${<}50$ ), compared to the Bender mission, can be observed. Concerning state-of-the-art mission constraints, in particular the severe restriction of heterodyne lasers on maximum range-rates, only the moderate Pendulum and the Bender-mission are beneficial options, of course in addition to GRACE and GRACE-FO. Furthermore, a Bender-type constellation would result in the most accurate gravity field solution by a factor of about 12 at long wavelengths (up to degree/order 40) and by a factor of about 200 at short wavelengths (up to degree/order 120) compared to the present GRACE solution. Finally, we suggest the Pendulum and the Bender missions as candidate mission configurations depending on the available budget and technological progress.  相似文献