Structures and tectonic evolution of the external zone of Alpine Corsica     

Emmanuel Egal   《Journal of Structural Geology》1992,14(10)

This paper presents a structural analysis of the external zone of Alpine Corsica, including the autochthonous domain and overlying external nappes (Santa Lucia and Balagne nappes). Two stages of nappe emplacement are identified occurring prior to and after the deposition of the Eocene sediments which were laid down upon first generation thrust contacts but are imbricated with their composite (continental and ophiolitic) basement by second generation thrusts. Five generations of structures with regional extent have been distinguished. However, the first generation has not been recognized within the visible part of the autochthon domain.Eoalpine first generation structures, restricted to allochthonous units, and Late Eocene to Early Oligocene second generation structures were nearly contemporaneous with the two stages of thrusting. The precise significance of E-W third generation structures is poorly understood. Broadly N-S fourth generation structures resulted from Oligocene compressive tectonics (folding and local backthrusting). Finally, fifth generation structures were generated during a Miocene extensional stage.These results are partly consistent with structural features previously reported in the southern and the northern outcrops of the Schistes lustrés, i.e. the main part of the allochthonous domain. A summary of a regional tectonic evolution is thus proposed for Alpine Corsica from Eoalpine obduction to Miocene extension.  相似文献   

Responding to unmet food needs of displaced persons or refugees:     

Nebasina Emmanuel Ngwa Dr. 《GeoJournal》1992,27(4):323-330

This paper identifies two types of displaced persons in two different ecological zones in Cameroon as a result of two major causes; a poisonous lake gas explosion in the North West and the effects of a civil war in Chad on Kousseri town in North Cameroon. The displaced persons, through no fault of theirs had to look up to both international and local donor organizations for assistance. This paper addresses the usual unmet food needs, analyses some of the performances that often go wrong but which can be corrected. The paper points out that donor agencies and the host government played major roles in raising food, cash, etc. but regrets to note that unsurmountable logistical problems, improper choice and use of personnel with wider expertise to handle specialized problems, inexistent buffer stocks and non-involvement of the displaced persons in managing some of the problems hindered hard-generated resources from reaching most of the beneficiaries. Better performances lie in reducing dependency on continuous external supplies and also in the local hosts allowing room for small scale agro-pastoral productions which should satisfy and even improve on the unmet nutritional difficiencies and rations of the displaced persons.  相似文献   

Design charts for a deep circular tunnel under non-uniform loading     

Emmanuel Detournay  Christopher M. St. John 《Rock Mechanics and Rock Engineering》1988,21(2):119-137

Summary This paper describes design charts which can be used to quickly predict the size and shape of the failed rock regions caused by the excavation of a deep tunnel, and the induced closure for cases of non-uniformin-situ stress fields. Through a simple graphical construction, the design charts can also be used to evaluate the performance of a support system.Previously of J. F. T. Agapito and Associates, U.S.A.  相似文献   

Software for producing trichromatic images in astronomy     

Sébastien Morel  Emmanuel Davoust 《Experimental Astronomy》1995,6(3):223-234

We present a software package for combining three monochromatic images of an astronomical object into a trichromatic color image. We first discuss the meaning of true colors in astronomical images. We then describe the different steps of our method, choosing the relevant dynamic intensity range in each filter, inventorying the different colors, optimizing the color map, modifying the balance of colors, and enhancing contrasts at low intensity levels. While the first steps are automatic, the last two are interactive.  相似文献   

A Geostatistical Methodology to Evaluate the Performance of Groundwater Quality Monitoring Networks Using a Vulnerability Index     

Hugo Júnez-Ferreira  Julián González  Emmanuel Reyes  Graciela S. Herrera 《Mathematical Geosciences》2016,48(1):25-44

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Is better to be a kayayei than to be unemployed: reflecting on the role of head portering in ghana’s informal economy     

Yaa Ankomaa Agyei  Emmanuel Kumi  Thomas Yeboah 《GeoJournal》2016,81(2):293-318

The implementation of neoliberal economic reforms with its resultant effects on rural agricultural economies has facilitated the migration of young girls from northern to southern Ghana to seek for alternative livelihoods in the urban informal economy as head porters (Kayayei). Using semi-structured questionnaires and interviews with 45 Kayayei in Makola and Agbogbloshie Markets, Accra, this study examines how migration as a livelihood strategy contributes to an improvement in the living conditions of young girls and their families. The paper also looks more closely into the pathways through which the livelihoods of these young female migrants may contribute to local economic development. The study highlights that Kayayei contribute to local economic development through market exchange and revenue generation, also there is significant perceived positive impact of head portering on standard of living of these young girls through improved access to income, health care and asset accumulation while their families benefit from remittances. The study concludes by advocating for the need to provide access to credit and skills training in enhancing the livelihood of Kayayei.  相似文献   

Environmental health hazards on industrial disasters: a study on how to achieve community-level social support     

Cheryl-Ann Sarita Boodram  Emmanuel Janagan Johnson 《Natural Hazards》2016,84(1):109-120

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Episodic mineralization of hydrothermal illite in the Soultz-sous-Forêts granite (Upper Rhine Graben, France)     

Anja M. Schleicher  Laurence N. Warr  Bernd Kober  Emmanuel Laverret  Norbert Clauer 《Contributions to Mineralogy and Petrology》2006,152(3):349-364

Episodic and localized illite mineralization is documented in the hydrothermally altered Soultz-sous-Forêts granite (Upper Rhine Graben, France). Separated grain-size fractions of altered granite and argillite vein samples contain mixtures of 2M₁ and 1M trans-vacant illite varieties. The platy pseudohexagonal 2M₁ illite phases dominate the vein fillings, whereas the 1M illite occurs largely as a fibrous pore-filling variety, which is particularly abundant in the granite matrix. Multiple phases of fluid injections into the granite body have resulted in different illite assemblages, each sample containing a mixture of polytype generations formed during different crystal growth events. On the basis of mineralogical and K–Ar isotopic constraints, the ages of these vein-mineralizing events are determined by plotting the K–Ar values of the various grain-size fractions against polytype abundance and the fitted volume-weighted crystallite thickness distributions. The results suggest a Permian age for the formation of the studied argillite veins, characterized by successive injections of hydrothermal fluids. Secondary episodes of illite crystallization occurred during Jurassic and Cretaceous (or even younger times) in both the veins and the granite matrix. There are indications that the polytype structure and composition of illite were strongly influenced by variations in fluid chemistry and the degree of fluid–rock interaction as the granite was progressively sealed during post-Variscan, episodic hydrothermal activity.  相似文献   

The effect of bidirectional flow on tidal channel planforms   总被引：1，自引：0，他引：1  

Sergio Fagherazzi  Emmanuel J. Gabet  David Jon Furbish 《地球表面变化过程与地形》2004,29(3):295-309

Salt marsh tidal channels are highly sinuous. For this project, ?eld surveys and aerial photographs were used to characterize the planform of tidal channels at China Camp Marsh in the San Francisco Bay, California. To model the planform evolution, we assume that the topographic curvature of the channel centreline is a key element driving meander migration. Extraction of curvature data from a planimetric survey, however, presents certain problems because simple calculations based on equally distanced points on the channel axis produce numerical noise that pollutes the ?nal curvature data. We found that a spline interpolation and a polynomial ?t to the survey data provided us with a robust means of calculating channel curvature. The curvature calculations, combined with data from numerous cross‐sections along the tidal channel, were used to parameterize a computer model. With this model, based on recent theoretical work, the relationship between planform shape and meander migration as well as the consequences of bidirectional ?ow on planform evolution have been investigated. Bank failure in vegetated salt marsh channels is characterized by slump blocks that persist in the channel for several years. It is therefore possible to identify reaches of active bank erosion and test model predictions. Our results suggest that the geometry and evolution of meanders at China Camp Marsh, California, re?ect the ebb‐dominated regime. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Phase de Laves dans la première opale CT bidisperse     

Jean-Pierre Gauthier  Emmanuel Fritsch  Bertha Aguilar-Reyes  Alain Barreau  Bernard Lasnier 《Comptes Rendus Geoscience》2004,336(3):187-196

A Mexican opal from the state of Jalisco has a bidisperse, perfectly ordered structure with framboid silica lepispheres of two different diameters. Its structure has been determined by the observation of a vicinal section, close to a dense plane. Fresh breaks along a vicinal plane emphasized regular steps, which were studied by means of SEM. We have been able to propose unit cell models, theoretical positions of the two sets of spheres, and probable space group, P6₃/mmc. This structure arranges similarly to that of a diatomic compound having an AB₂ stoichiometry and corresponds to a cubic (MgCu₂-type) or hexagonal (MgZn₂-type) Laves phase. This last variety seems to be the most probable structure. To cite this article: J.-P. Gauthier et al., C. R. Geoscience 336 (2004).  相似文献