Les manifestations tectoniques synsédimentaires associées à la compression éocène en Tunisie : implications paléogéographiques et structurales sur la marge Nord-Africaine     

Abdessalem El Ghali  Noureddine Ben Ayed  Claude Bobier  Fouad Zargouni  Anis Krima 《Comptes Rendus Geoscience》2003,335(9):763-771

In central Tunisia, a synsedimentary tectonic episode has been pointed out through the tectonic movements affecting the Late Palaeocene–Early Eocene successions. This tectonic episode has controlled, to a large extent, the palaeogeographic setting of the area during that period and confirmed the important effect induced by the Pyrenean shortening phase on the edge of the African plate, which obviously has witnessed a common history with the southern part of the European plate. To cite this article: A. El Ghali et al., C. R. Geoscience 335 (2003).  相似文献   

A lead isotope method for the accurate dating of disturbed geologic systems: numerical demonstrations, some applications and implications     

Fouad Tera 《Geochimica et cosmochimica acta》2003,67(19):3687-3716

Lead isotopes are compared in two equivalent diagrams. With a range in U/Pb, a closed system that evolved its radiogenic Pb in a single stage yields data that define a line of exactly the same age in the two presentations. This strict reproducibility (within ± a few 10⁶ yr, at most) is the crux of the concept of Pb-isotope synchronism. In contrast, an open system produces data that disperse variably in the two diagrams, yielding ages which are often different by ?10⁷ yr. However, because an age-calculation reconciles uncertainty in the age with the degree of dispersion in the data, a highly disturbed system yields false ages (from both diagrams), which nevertheless overlap within the calculated errors.This dichotomy (tightly reproduced linearity of a closed system vs. loosely correlated dispersion of an open one) is exploited in a new procedure, termed differential Pb correlation. This procedure allows filtering the data, so that an imperfect isochron may be improved or an invisible one may be identified within a dispersion field.Applying the synchronism method to the whole rock Pb isotopic data on the Amîtsoq gneisses results in their resolution into three synchronous lines, yielding the single-stage ages of 4.42, 3.74 and 3.45 Ga. In an attempt to reconcile this observation with geology, the mechanisms which may have produced these lines (multi-stage lineation) are explored. In addition, the possibility that the 4.42-Ga line is an actual isochron, and that vestiges of an ancient terrestrial crust of that age exist, are contemplated in some detail.The utility of the method is further demonstrated by application to meteorites as well as terrestrial rocks. Isochrons of crustal rocks intersect with each other as subgroups in multiple places (that is, at multiple Pb isotope values). This indicates the apparent existence of terrestrial reservoirs distinct in isotopic composition from each other. One of these reservoirs, characterized by a low (U/²⁰⁴Pb) = 4 may represent a depleted complement to the U-enriched source(s) of the ocean-island basalt (OIB). If so, then the so-called “Pb paradox” may no longer exist.  相似文献   

Evaluating accuracy for two empirical methods in predicting settlement of drilled shafts     

Azm S. Al-Homoud  T. Fouad  Ahmed Mokhtar 《Geotechnical and Geological Engineering》2004,22(2):245-267

Several theoretical, empirical and semi-empirical methods are available in the literature to predict settlement of drilled shafts in sandy soils. In the Arabian Gulf countries, specifically in the United Arab Emirates, equations and procedure from the rest of the world are being used in analysis and design of drilled shafts without proper validation. It is the aim of this study to assess the applicability and evaluate the accuracy of two well known, and commonly used methods for pile prediction in the United Arab Emirates (UAE), namely Vesic (1977) and Poulos (1979), via comparison with data from field pile load tests conducted on shafts drilled in the region. Some of these tests were conducted for the purpose of this study, while others were made available through the courtesy of International Piling Contractors who are active in the region (e.g. Bauer International and Swiss Borings). Pile load test data were analyzed to back-calculate the model parameters related to settlement under different loading stages. Geological data and soil properties were obtained from studies conducted at the relevant sites. An effort is made to correlate soil properties with the prediction models. Statistical analysis is conducted to assess the accuracy of the results obtained from the two methods at different stages of loading via those obtained from pile load tests. Moreover, a detailed parametric study is conducted to assess the effect of the related parameters on the predicted pile settlement and the estimated settlement at different stages of loading. The study concluded with a recommendation of the most appropriate models and procedures to be followed for predicting the settlement of drilled shafts in the UAE, together with useful charts and correlation relations. Results showed that settlement values predicted by Vesic (1977) and Poulos (1979) overestimates the true values. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Green synthesis of magnetic mesoporous silica nanocomposite and its adsorptive performance against organochlorine pesticides     

W. A. El-Said  D. M. Fouad  M. H. Ali  M. A. El-Gahami 《International Journal of Environmental Science and Technology》2018,15(8):1731-1744

Green synthesis of nanomaterials has received increasing attention as an eco-friendly technology in materials science. Here, we have used two types of extractions from green tea leaf (i.e., total extraction and tannin extraction) as reducing agents for a rapid, simple and one-step synthesis method of mesoporous silica nanoparticles/iron oxide nanocomposite based on deposition of iron oxide onto mesoporous silica nanoparticles. Mesoporous silica nanoparticles/iron oxide nanocomposite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray, vibrating sample magnetometer, N₂ adsorption and high-resolution transmission electron microscopy. Mesoporous silica nanoparticles/iron oxide nanocomposite was used as a solid adsorbent for removal of lindane pesticide from aqueous solutions. The developed system possesses the advantages of silica as core that include large surface area and advantages of iron oxide (shell) that include the capability to interact with chlorinated compounds and ability to release by using external magnetic field. UV-Vis technique was used as a simple and easy method for monitoring the removal of lindane. Effects of pH and temperature on the removal efficiency of the developed mesoporous silica nanoparticles/iron oxide nanocomposite toward lindane pesticide were also investigated. Fourier transform infrared spectroscopy, high-performance liquid chromatography and gas chromatography techniques were used to confirm the high ability of mesoporous silica nanoparticles/iron oxide nanocomposite for sensing and the capture of lindane molecules with high sorption capacity (about 99%) that could develop a new eco-friendly strategy for detection and removal of pesticide and as a promising material for water treatment.  相似文献   

Style and timing of tectonic deformation across the Bou Arada-El Fahs troughs system,Northeast Tunisia: integration in the structural evolution of Atlas fold and thrust belt     

Mohamed Sabri Arfaoui  Radhouane Khouni  Soufiene Dridi  Fouad Zargouni 《Arabian Journal of Geosciences》2018,11(5):95

The Bou Arada-El Fahs troughs system is a particularly E-W trending collapsed structure with the manifestation of normal-to-strike-slip faults. A combined multi-source and multi-scalar structural and geophysical investigation provides important insights on the geometry and the kinematics evolution of trough systems in the Atlas of Tunisia. New data, as well as a reappraisal of available data show that the studied troughs system is established during three main successive events: the Oligocene-Miocene, the Tortonian, and the Plio-Quaternary events. The goal of this paper is to present the structural evolution of the study area, on a pre-structured substratum. The structural evolution progressed from an extensional event, manifested by the formation of grabens, passing by an episode of reactivation of faults related troughs in strike-slip motion during the Atlas compression accompanied by an en-échelon folding in foot wall and hanging wall. These results acquired and presented in the following order: We will initially present the geological context by integrating and correlating the lithostratigraphic data. We continue by examining the geometry and kinematics of structure-related troughs via the detailed geological mapping, the interpretation of available 2D seismic data, and the interpretation of processed fault slip data. This integrated geological and geophysical study allows a better understanding of the BETS, and makes it possible to propose a new geometrical and kinetic model of the establishment of trough structure in the Tunisian Atlas.  相似文献   

Causes of the famine among the rural population of the Sahelian zone of the Sudan     

Fouad N. Ibrahim Dr. 《GeoJournal》1988,17(1):133-141

Taking the example of W Sudan, an analysis of the climatic incidents leading to the two recent famine disasters is made. On this natural background, the human side is investigated. Focus is directed towards the fragile economic structure of the famine-prone population groups. An early-warning system for famine in the Sahelian Zone is proposed taking grain production and storage, livestock development and the relationship between the prices of livestock and grain as major indicators.  相似文献   

The role of rural-rural migration as a survival strategy in the Sahelian zone of the Sudan —     

Prof. Dr. Fouad N. Ibrahim  Prof. Dr. Helmut Ruppert 《GeoJournal》1991,25(1):31-38

Taking the example of Burush, N Darfur, Sudan, the authors analyse the role of migration as a survival strategy in the desertification-stricken Sahelian zone. It is being argued that the rual-rual migration plays a greater role than the rual-urban migration among the Berti ethnic group of northern Darfur. Their high mobility within their own area is part of their traditional economic pattern for coping with aridity and high rainfall variability  相似文献   

Hunger-vulnerable groups within the metropolitan food system of Khartoum     

Fouad N. Ibrahim 《GeoJournal》1994,34(3):257-261

Due to the current civil war and the economic and political deterioration in the Sudan, the majority of the Sudanese are suffering from food shortage. The dislocated southern Sudanese in Khartoum, however, belong to the group most affected. This paper tries to analyse the structure of hunger in the capital city of the Sudan. The formal and informal food supply systems are described. The reasons why the southern Sudanese are specially vulnerable to hunger and the indicators of this vulnerability are discussed.  相似文献   

Combating famine by grain storage in Western Sudan     

Prof.  Dr. Fouad N. Ibrahim 《GeoJournal》1987,14(1):29-35

Traditional grain storage used to be an effective mechanism to combat famine in the rural areas of W Sudan. Of late, this mechanism has failed to function and a severe famine took place in 1984–1985. This paper endeavours to highlight this crisis, show the traditional methods of grain storage and point out to ways of retrieving grain storage systems to start again on a less vulnerable basis. An assessment of grain storage requirements under the new conditions where both market and subsistence economy are effective in rural areas is made for the different ecological zones of W Sudan.  相似文献   

Social and economic geographical analysis of the Egyptian Copts     

Fouad N. Ibrahim 《GeoJournal》1982,6(1):63-67

This paper gives a brief account of the social and economic situation of the Copts in Egypt. As an ethnic group the Copts are the pure successors of the ancient Egyptians. This does not imply that the Moslems are pure Arabs. At least 90% of the Egyptian Moslems are of Coptic origin, so that no particular differentiation should be made between the Copts and the Moslems of Egypt from the ethnical point of view. The Copts are fully integrated into the Egyptian population. Only in times of religious persecution, they huddled together in villages of Upper Egypt in the provinces of El Minia and Assiut. The recent wave of reislamisation in the Near East has inflicted some suffering on the Copts of Egypt. This was combined with economic losses. Nasser's nationalisation of private concerns and confiscation of large tenures of land was a blow directed against the Copts. Suggestions are made to improve their situation with the aim of giving them equal rigths with the Moslems in the political, social, economic, and religious fields.  相似文献