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351.
Mahmoud Dlala 《Comptes Rendus Geoscience》2002,334(2):135-140
The synsedimentary tectonic activity evidenced in central and northern Tunisia points out the fact that the Campanian–Maastrichtian deposits are associated with several NW–SE and east–west normal faults. These results suggest that the east–west transform fault of North African Margin is still active during this stage. These data allow us to discuss a new geodynamic model for the North African Margin. To cite this article: M. Dlala, C. R. Geoscience 334 (2002) 135–140. 相似文献
352.
Vania Rosolen Mathieu Lamotte René Boulet Jean Trichet Olivier Rouer Adolpho José Melfi 《Comptes Rendus Geoscience》2002,334(3):187-195
A mottled horizon in a laterite cover (without any duricrust) was studied by microscopy and quantitative chemical microanalysis. Apart from the voids, light red spots consisting of Fe-rich particles (≈2 μm) are set in clayey plasma. Dark red spots consisted of concentrations of Fe-rich particles. These patterns are inherited. On the border of structural or biological voids, where Fe-depletion features are systematic, gray or yellow spots result from dissolution of the Fe-rich particles and impregnation of the plasma by iron, respectively. The present Fe-depletion is the dominant process that explains the mottled differentiation and the absence of lateritic duricrust. To cite this article: V. Rosolen et al., C. R. Geoscience 334 (2002) 187–195. 相似文献
353.
Jean-François Royer Daniel Cariolle Fabrice Chauvin Michel Déqué Hervé Douville Rong-Ming Hu Serge Planton Annie Rascol Jean-Louis Ricard David Salas Y Melia Florence Sevault Pascal Simon Samuel Somot Sophie Tyteca Laurent Terray Sophie Valcke 《Comptes Rendus Geoscience》2002,334(3):147-154
Two climate simulations of 150 years, performed with a coupled ocean/sea-ice/atmosphere model including stratospheric ozone, respectively with and without heterogeneous chemistry, simulate the tropospheric warming associated with an increase of the greenhouse effect of carbon dioxide and other trace gases since 1950 and their impact on sea–ice extent, as well as the stratospheric cooling and its impact on ozone concentration. The scenario with heterogeneous chemistry reproduces the formation of the ozone hole over the South Pole from the 1970s and its deepening until the present time, and shows that the ozone hole should progressively fill during the coming decades. To cite this article: J.-F. Royer et al., C. R. Geoscience 334 (2002) 147–154. 相似文献
354.
Anne Le Friant Georges Boudon Jean-Christophe Komorowski Christine Deplus 《Comptes Rendus Geoscience》2002,334(4):235-243
Results from recent fieldwork and the Aguadomar marine survey in the Lesser Antilles clearly indicate that the volcanic field of southern Dominica has experienced three major edifice collapse events. This led to formation of the most voluminous debris avalanches known in the Caribbean Arc. Submarine hummocky morphology with plurikilometric megablocks is characteristic of debris avalanche deposits. We propose that steep slopes on the western Caribbean side of the island and intense hydrothermal alteration lead to recurrent large-scale edifice collapses. Therefore islands in the Lesser Antilles face a non-negligible risk from generation of tsunamis associated with potential future edifice collapse. To cite this article: A. Le Friant et al., C. R. Geoscience 334 (2002) 235–243. 相似文献
355.
Samir Bouaziz Younes Jedoui Éric Barrier Jacques Angelier 《Comptes Rendus Geoscience》2003,335(2):247-254
Pleistocene marine deposits of so-called Tyrrhenian age in southeastern Tunisia include two lithostratigraphic units of Last Interglacial (marine isotopic substage 5e). The lower unit culminates at about +3 m above the sea level; the upper unit with Strombus bubonius culminates at +5 m. Brittle deformations affected the upper unit. The analysis of fault-slip data sets reveals a post-Tyrrhenian N020°E trending compression, consistent with joint patterns. This event induced limited vertical movements, showing that at the northeastern edge of the Saharan Platform, the coastal area of the southern Tunisia remained relatively stable since at least the Last Interglacial. 相似文献
356.
Heritiana Rakoto Pierre Andrieux Jean-Bruno Ratsimbazafy Vittorio Iliceto Eddy Rasolomanana Louis Pastor Gian Maria Zuppi 《Comptes Rendus Geoscience》2003,335(4):355-363
A gravimetric survey has been carried out in a sedimentary basin, south of Madagascar, in order to define the bedrock morphology. The bedrock is made up of crystalline and volcanic rocks. The objective of the survey was to demonstrate whether a relationship could be established between bedrock morphology and groundwater mineralisation. Indeed, bedrock morphology has been successfully mapped and it is confirmed that most of the low mineralisation wells are located in areas where the slope of the bedrock is trending to the south-west, which ensures a higher hydraulic conductivity, i.e. a faster water flow, than in the other parts of the survey area. To cite this article: H. Rakoto et al., C. R. Geoscience 335 (2003). 相似文献
357.
Pablo Pulido-Leboeuf Antonio Pulido-Bosch Maria Luisa Calvache Ángela Vallejos José Miguel Andreu 《Comptes Rendus Geoscience》2003,335(14):1039-1048
The strontium content and the SO42?/Cl? and Mg2+/Ca2+ ratios were used as natural tracers of the residence time of seawater intrusion into the Castell de Ferro aquifer. Analysis of these parameters indicated the existence of two principal flowpaths in the aquifer. The first flows through the eastern part of the aquifer, through the karstified Castell de Ferro massif; it accommodates a larger and more rapid flow, so that the residence time is shorter, leading to lower SO42+/Cl? ratios, lower Sr2+ content and higher Mg2+/Ca2+ ratios. The second flowpath is in the western sector, and flows exclusively through alluvial deposits; the flow here is slower, particularly that flowing towards the sea. Thus the residence time of the water here will be longer and there is scant flushing of the intruded seawater; this is manifested in the high Sr2+ content, high SO42+/Cl? and low Mg2+/Ca2+ ratios. To cite this article: P. Pulido-Leboeuf et al., C. R. Geoscience 335 (2003). 相似文献
358.
Laurent Bret Jean-Lambert Join Xavier Legal Jean Coudray Bertrand Fritz 《Comptes Rendus Geoscience》2003,335(14):1031-1038
The drilling of a gallery through the Roche-Écrite massif (Reunion Island) allowed to sample the old formations of the ‘Piton des Neiges’ volcano. The mineralogical study of the alteration products of the formations showed significant variations of the zeolites/clay minerals ratio depending on the location of the rocks in the volcano. The abundance of zeolites in the formation near the surface hydrographic network or the underground water drainage system seems to be due to the physicochemical processes favouring zeolites in more open systems in their competition with secondary clays. To cite this article: L. Bret et al., C. R. Geoscience 335 (2003). 相似文献
359.
360.
A new proficiency testing sample, OPY‐1 (ultramafic rock), the basis of the twentieth international proficiency test of analytical geochemistry laboratories (GeoPT 20), was recently prepared by the International Association of Geoanalysts (IAG). This paper reports analytical data for Os, Ir, Ru, Rh, Pt and Pd with different digestion techniques, including an improved Carius tube, Carius tube combined with HF dissolution and alkaline fusion. About 4–15% of the PGEs are in the silicate phase, which cannot be leached by aqua regia even when digested at 300 °C with the Carius tube technique. Both the Carius tube technique combined with HF dissolution and alkaline fusion can obtain reliable data. The results demonstrated that OPY‐1 is sufficiently homogeneous at a 2 g test portion level to be suitable as a reference material for method validation. The procedure for sealing the Carius tube was simplified and the recommended digestion procedures are provided. 相似文献