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Philippe Paillou Ahmed El Barkooky Aly Barakat Jean-Marie Malezieux Bruno Reynard Jean Dejax Essam Heggy 《Comptes Rendus Geoscience》2004,336(16):1491-1500
Using orbital imaging radar, we have detected a large number of circular structures in the southwestern Egyptian desert, covering more than 4500 km2 close to the Gilf Kebir plateau in sandstones of Upper Cretaceous. Fieldwork confirmed that it is a new impact crater field: 13 craters from 20 m to 1 km in diameter were studied. The impact origin is confirmed by the observation of shock-related structures, such as shatter cones and planar fractures in quartz grains of breccia. Considering the extension of the crater field, it was possibly created by several meteorites that broke up when entering the atmosphere. To cite this article: P. Paillou et al., C. R. Geoscience 336 (2004).
Résumé
À partir d'images satellites issues de systèmes radar, nous avons détecté un grand nombre de structures circulaires dans le Sud-Ouest du désert égyptien, s'étendant sur plus de 4500 km2 à l'est du plateau du Gilf Kebir, dans des grès du Crétacé supérieur. Une étude sur le terrain a permis de vérifier qu'il s'agit d'un champ d'impacts météoritiques jusque là inconnu : 13 structures, d'un diamètre compris entre 20 m et 1 km, ont été reconnues comme cratères d'impact. La présence d'un grand nombre de cônes de percussion et de brèches dans lesquelles des quartz choqués à structures planaires ont été observés confirment l'hypothèse de l'impact. Considérant l'extension du champ d'impact, il a probablement été créé par plusieurs météorites qui se sont fragmentées dans l'atmosphère terrestre. Pour citer cet article : P. Paillou et al., C. R. Geoscience 336 (2004). 相似文献13.
Jessica Barabasch Mathieu Ducros Nicolas Hawie Samer Bou Daher Fadi Henri Nader Ralf Littke 《Basin Research》2019,31(2):228-252
The Eastern Mediterranean Levant Basin is a proven hydrocarbon province with recent major gas discoveries. To date, no exploration wells targeted its northern part, in particular the Lebanese offshore. The present study assesses the tectono‐stratigraphic evolution and related petroleum systems of the northern Levant Basin via an integrated approach that combines stratigraphic forward modeling and petroleum systems/basin modeling based on the previous published work. Stratigraphic modeling results provide a best‐fit realisation of the basin‐scale sedimentary filling, from the post‐rift Upper Jurassic until the Pliocene. Simulation results suggest dominant eastern marginal and Arabian Plate sources for Cenozoic siliciclastic sediments and a significant contribution from the southern Nilotic source mostly from Lower Oligocene to Lower Miocene. Basin modeling results suggest the presence of a working thermogenic petroleum system with mature source rocks localised in the deeper offshore. The generated hydrocarbons migrated through the deep basin within Jurassic and Cretaceous permeable layers towards the Latakia Ridge in the north and the Levant margin and offshore topographic highs. Furthermore, the basin model indicates a possibly significant influence of salt deposition during Messinian salinity crisis on formation fluids. Ultimately, the proposed integrated workflow provides a powerful tool for the assessment of petroleum systems in underexplored areas. 相似文献
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Samer K. Abi Kaed Bey Douglas P. Connelly François-Eric Legiret Andy J. K. Harris Matthew C. Mowlem 《Ocean Dynamics》2011,61(10):1555-1565
In this work, we describe a high-resolution fluorometric shipboard analyser and an improved method to determine NH4+ in oligotrophic seawater. The limit of detection is <5 nM, calculated with 95% confidence level using the weighted regression
line applied to the standard addition method using real samples prepared with low nutrient seawater from the Atlantic. The
results are summarised and cross-compared with spiked artificial seawater (ASW) and spiked Milli-Q water samples. The analyser
has a precision of ±1–4% with a high performance over a wide range from 5 nM to 25 μM. The methodology of NH4+ analysis is based on the fluorescent product formed between o-pthaldialdehyde and NH4+ in the presence of sulfite. Due to the high resolution of the developed system, we were able to study in depth the sensitivity
of the method to salinity, amines, amino acids and potential interferences from particles/algae. The method was found to be
sensitive to salinity variations, reducing the signal by up to 85% at 5 nM; this effect decreased at higher concentrations
of ammonium. It was noted that the interference from amines at low concentrations was negligible; however, at either high
amino acid or high amine concentrations, the signal was depressed. To test for the effect of particles on the system, the
system was tested with samples containing phytoplankton (Dunaliella primolecta) cells at different concentrations prepared with ASW to simulate the effect of a phytoplankton bloom. This experiment assessed
the potential impact of both particles and other potential fluorescence interferences from cells and/or ammonium leaching
from cells. This experiment showed that a phytoplankton bloom could potentially have an impact of up to 12% on the signal
of interest. Thus, we propose that this method is suitable for oligotrophic environments rather than coastal and eutrophic
environments. The reagent was found to be stable for 17 days and standards of 1 μM were stable for 6 days under laboratory
conditions. The developed analyser was successfully demonstrated in the North Atlantic Ocean, in an area of oligotrophic,
low NH4+ oceanic waters. 相似文献
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Widad Ennaji Ahmed Barakat Mohamed El Baghdadi Hakima Oumenskou Mohamed Aadraoui Lalla Aicha Karroum Abdessamad Hilali 《Journal of Earth System Science》2018,127(6):79
Assessment of soil suitability for sustainable intensive agriculture is an appropriate tool to select the land suitable for agricultural production with the least economic and environmental costs. This study was conducted to evaluate the agricultural soil quality in the northeast area of Tadla plain (Morocco) using geographic information system (GIS) and analytical hierarchy process (AHP). Six soil quality indicators, i.e., pH, organic carbon, cation exchange capacity, texture, salinity and slope were considered and performed in 60 subsurface soil samples. AHP method was utilized to identify the weight of each indicator from the pairwise comparison matrix. The weighted sum overlay analysis was then used to generate the soil quality map in a GIS environment, by overlaying both indicator weights and sub-indicator weights. The studied area was classified into four soil quality categories, i.e., poor, medium, good, and excellent, the percentage of each category is 1.12, 20.98, 61.07 and 16.83%, respectively. The results indicated that 1.12% of the study area has poor suitability for sustainable intensive agriculture due to their unsuitable texture and low salinity, while about 77% of cultivated soils are adapted to agricultural production. The above results could be useful for the management of agricultural activity. 相似文献
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Heavy metal pollution and soil magnetic susceptibility in urban soil of Beni Mellal City (Morocco) 总被引：3，自引：2，他引：1
Mohamed El Baghdadi Ahmed Barakat Mohamed Sajieddine Samir Nadem 《Environmental Earth Sciences》2012,66(1):141-155
The assessment of anthropogenic impact in the urban environment can be evaluated according to heavy metal contents of soils such as Pb, Cu, Zn, Cd and Fe. These elements have more affinity to establish metallic bond with ferrous material leading to enhancement of soil magnetic susceptibility. The objective of this study was to undertake joint magnetic and geochemical investigations of road-side urban soil materials to address the environmental pollution of Beni Mellal city that has been subjected to environmental stress, due to population overpressure and related urbanization. Twenty three soils magnetic susceptibility profiles were made along 5 km peripheral national road (N8) in Beni Mellal. The magnetic survey reported here for the first time on this City’s topsoils tries to establish the link between magnetic properties and the content of heavy metals. High magnetic susceptibility values and high contents of heavy metals were found near the paved edge of the road and within the place reserved as large engine park. Magnetic extracts of highly polluted areas and unpolluted soil (olive plantation) were analyzed by SEM coupled with RDX in order to discriminate anthropogenic magnetic spherules and pedo-lithogenic magnetite-like minerals. Magnetic mineralogy determined by Mössbauer spectroscopy suggests the presence of hematite, magnetite and goethite in highly polluted areas. The iron oxides and especially goethite are efficient in incorporating and/or adsorbing foreign ions. 相似文献
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Samer?A.?BarakatEmail author Abdallah?I.?Husein?Malkawi Maher?Omar 《Geotechnical and Geological Engineering》2005,23(1):61-78
Parametric study was carried out in this paper using the Finite Element Method (FEM) to study the effects of variations of the two parameters, i.e., variations in batter slope and foundation properties under static and dynamic loading conditions on the distribution of the peak stresses within the dam and foundation soils. The response spectra for the operating basis earthquake (OBE) and the maximum credible earthquake (MCE) were used in the dynamic analysis. It is shown that the distribution of peak stresses across base of dam and the extent of tensile zone on the foundation soils at the foundation level vary with the variations in the batter slope. Generally, as the batter slope increases the extent of the tensile zone at the foundation level decreases but not necessarily the maximum tensile stresses. However, an optimum batter slope could be achieved based on the results of this parametric study. It should be noted that the greatest tension is developed in the rock adjacent to the toe of the batter. For the foundation mechanical properties, it has been shown that the assessment of accurate soil mechanical properties has a great effect on the computed design stresses from finite element analysis. However, the greatest effect of the foundation properties was on the stresses at the base of dam while it has a negligible effect within the dam body. 相似文献
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I.A. Barghouthi V. Pierrard A.R. Barakat J. Lemaire 《Astrophysics and Space Science》2001,277(3):427-436
A Monte Carlo simulation is used to study the effects of Kappa H+distributions in the polar wind. We consider the gravity, the polarization electric field, the divergence of geomagnetic field
lines and Coulomb collisions of H+ in a background of O+ ions. The aim is to study the consequences of a velocity distribution function with an enhanced high energy tail instead
of a Maxwellian distribution as assumed in earlier Monte Carlo simulations. The transformation of the velocity distribution
function of H+ ions as a function of the altitude is presented. Effects resulting from the acceleration of the particles by the polarization
electric field and from Coulomb collisions depend on the energy of the particles. Coulomb collisions mainly affect low energy
particles while high energy particles are more efficiently accelerated by the upward directed ambipolar electric field. The
combination of both effects results in double-hump velocity distribution functions developing in the transition region. We
study consequences of suprathermal tails distributions on the shape of the double-hump and on the moments of the velocity
distribution function.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献