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31.
Evidence for Triassic salt domes in the Tunisian Atlas from gravity and geological data 总被引：3，自引：1，他引：3
Chokri Jallouli Mongi Chikhaoui Ahmed Braham Mohamed Moncef Turki Kevin Mickus Ramdhane Benassi 《Tectonophysics》2005,396(3-4):209-225
Detailed gravity data were analyzed to constrain two controversial geological models of evaporitic structures within the Triassic diapiric zone (Triassic massifs of Jebel Debadib and Ben Gasseur) of the northern Tunisian Atlas. Based on surface observations, two geological models have been used to explain the origin of the Triassic evaporitic bodies: (1) salt dome/diapiric structure or (2) a “salt glacier”. The gravity analysis included the construction of a complete Bouguer gravity anomaly map, horizontal gravity gradient (HGG) map and two and a half-dimensional (2.5D) forward models. The complete Bouguer gravity anomaly map shows a prominent negative anomaly over the Triassic evaporite outcrops. The HGG map showed the location of the lateral density changes along northeast structural trends caused by Triassic/Cretaceous lithological differences. The modeling of the complete Bouguer gravity anomaly data favored the diapiric structure as the origin of the evaporitic bodies. The final gravity model constructed over Jebel Debadib indicates that the Triassic evaporitic bodies are thick and deeply rooted involving a dome/diapiric structure and that the Triassic material has pulled upward the younger sediment cover by halokinesis. Taking in account kinematic models and the regional tectonic events affecting the northern margin of Africa, the above diapirs formed during the reactive to active to passive stages of continental margin evolution with development of sinks. Otherwise, this study shows that modeling of detailed gravity data adds useful constraints on the evolution of salt structures that may have an important impact on petroleum exploration models. 相似文献
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Neotectonic and seismotectonic investigation of seismically active regions in Tunisia: a multidisciplinary approach 总被引：1，自引：0，他引：1
N. Bahrouni S. Bouaziz A. Soumaya N. Ben Ayed K. Attafi Y. Houla A. El Ghali N. Rebai 《Journal of Seismology》2014,18(2):235-256
Due to its key position within the Africa–Europe convergence zone, Tunisia is marked by thrusting, folding, and faulting and has a major rupture zones associated with active faults. Consequently, most of Tunisian land is seismically active with significant active deformations, showing recent seismic events and their relative surface effects. This paper reports on several aspects of the seismotectonics, historical, and present-day seismicity and places them in the general tectonic and geodynamic framework of Tunisia. Field investigations, based on an integrated multidisciplinary approach, included (1) the identification of active faults, their motion and displacement, geomorphic aspects, and scarps and their relation with the general structural map of Tunisia and (2) an extensive analysis of brittle tectonic deformation affecting Quaternary deposits in several sites throughout Tunisia. The integration of field data within the existing data related to the seismic events that took place during the last decades allowed the establishment of an earthquake distribution map, as well as major seismic zones for better understanding of the seismicity database of Tunisia. To establish microzonation maps in seismic regions such as Gafsa and its surroundings, we have analyzed surface effects and secondary structures associated with active faults and correlated them with deformation rates, reconstructed for significant seismic events. Most faults exhibited typical left-stepping en-echelon with strike-slip component pattern suggesting that Tunisia is presently subjected to NNW–SSE compression. The focal mechanism of most Tunisia earthquakes combined with the existing tectonic and structural information and reconstruction of the Quaternary stress tensor allowed (a) better understanding of seismic zoning, (b) provided better assessment of the seismic hazard, and (c) facilitated the interpretation of the relationship between seismic zones and the geodynamic African–Eurasian plate boundary. 相似文献
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Remote gully erosion mapping using aster data and geomorphologic analysis in the Main Ethiopian Rift 总被引：1，自引：0，他引：1
The Main Ethiopian Rift(MER)is an area of extreme topography underlain by post-Miocene volcanic rocks,Jurassic limestone and a Precambrian basement.A prime concern is the rapid expansion of wide gullies that are impinging on agricultural land.We investigate the potential contribution of Advanced Space-borne Thermal Emission and Reflection Radiometer(ASTER)data and geomorphologic parameters to discern patterns and features of gully erosion in the MER.Maximum Likelihood Classifica-tion(MLC),Support Vector Machine(SVM),and Minimum Distance(MD)classifiers are used to extract different gully shapes and patterns.Several spatial textures based on Grey Level Co-occurrence Matrices(GLCMs)are then generated.Afterwards,the same classifiers are applied to the ASTER data combined with the spatial texture information.We used geomorphologic parameters ex-tracted from SRTM and ASTER DEMs to describe the geomorphologic setting and the gullies’ shapes.The classifications show accuracies varying between 67% and 89%.Maps derived from this quantitative analysis allow the monitoring and mapping of land degradation as a direct result of gully-widening.This study reveals the utility of combining ASTER data and spatial textural infor-mation in discerning areas affected by gully erosion. 相似文献
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Arid and semi-arid regions are susceptible to high levels of erosion.A rapid and cost effective methodological erosion assessment for these regions is required to describe and monitor the processes that control erosion.This study uses remote sensing to describe the contribution of several factors that control erosion.Topography,land use,vegetation density,soil properties and climatic proxies are used to determine erosion risk and to provide basic maps of water and soil conservation practices. A hierarchi... 相似文献
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The monthly geochemical study of Bizerte lagoon principal affluent water consists in characterizing the water geochemical facies and their inorganic pollution degree by nutrients. The major elements analysis shows calcium sulfate to chloride calcium balanced facies. The geochemical analysis of water nutritive salts shows generally a good to excellent quality. Wadi Guenniche is considered more polluted as we recorded the highest nutrients contents. The principal component analysis of the connections between the physicochemical and geochemical parameters of Bizerte lagoon affluent water show that the low salinities, the turbidity, and the low contents of major sodium, chloride ions, and nutritive elements are the major factors of the environment controlling the good quality of this fresh water. 相似文献
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The valorization solutions for dredged sediment have been the subject of a great number of investigations over the previous decades.In the current present study,treatment of polluted dredged sediment fom the commercial port of Sfax,Tunisia,is proposed.An industrial byproduct(blast furnace slag)was used to bind raw sediment for a reuse in road engineering.Following standards of this field,the raw sediment first was identified and classified according to the French technical guidance.Then an environmental assessment was applied due to the presence of heavy metals.The concentrations were measured on the raw sediment particles so as to control the binding effect on heavy metals.Sediment mixtures consisted of a mix of sand and a blast furnace slag activated with quicklime.Different mixtures were tested and some were proposed for sub-layer applications.The Sfax commercial port raw sediment is considered as a sandy loam with a very low fraction of clay.The measured concentrations of heavy metals exceed the recommended thresholds for cadmium,copper,lead,and zinc.These can induce hazardous effects in the case of their dumping into the sea.On the other hand,the concentrations of the detected elements after leaching tests run on raw sediment samples are very low compared to the thresholds;such results highlight a possible recycling of the raw sediment in subgrade layers without any negative impact.Suitable formulations were deduced for road engineering tests relying on the ratio the California Bearing Ratio index and the immediate bearing index.If the obtained ratio exceeds one,the treated sediment can be recycled and used in road layers. 相似文献
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Eric Barrier Samir Bouaziz Jacques Angelier Gilles Creuzot Jamel Ouali Pierre Tricart 《Geodinamica Acta》2013,26(1):39-57
AbstractA detailed analysis of brittle deformations in the Saharian platform of southern Tunisia is based on studies of fault-slip data sets and joint sets. It allows reconstruction of the Mesozoic paleostress evolution. During the Permo-Triassic, N-S extensions occurred with high late Permian subsidence rates. During the Norian, strike-slip movements reactivated former normal faults. During the Jurassic and the Cretaceous a succession of extensional events was characterized by : (1) a N-S extension which dominated from late Triassic to early Aptian. We relate this extension to the Africa-Eurasia divergence; (2) a ENE-WSW extension during the Cenomanian. We relate this extension to the opening of «he African basins ; (3) a NE-SW Senonian extension that continued during the Cenozoic in the Jeffara and in the Gabes Gulf, during the further evolution of the northern African margin. The various compressional trends recorded in the platform are attributed to Cenozoic events. 相似文献
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Noamen Rebai Hammadi Achour Rochdi Chaabouni Rania Bou Kheir Samir Bouaziz 《Earth Science Informatics》2013,6(4):187-198
Morphotectonic analysis using geomorphic indexes has been developed as a basic tool to identify recent tectonic deformation in specific areas.This study was undertaken to develop an integrated quantitative geomorphic analysis of tectonic activity in the North–south axis, central of Tunisia. Different geomorphic indexes, including elongation ratio (E), drainage basin asymmetry (Af), hypsometric integral (Hi), Valley floor width-to-height ratio (Vf), mountain front sinuosity (Smf), and stream length gradient index (SL) were calculated. The relationships between the calculated indexes, their correlations and their significance (based on p-values) were also investigated.. Using the hierarchical cluster analysis based on Ward’s method, these indexes were classified into three classes describing the relative, different effect of tectonics in each fault segment. The higher deformation is concentrated in the NE-SW Boudinar fault, followed, in order of decreasing activity, by Goubrar, Gouleb, and Majoura normal faults. This pattern of variation in the relative degree of tectonic activity is consistent with field evidence. 相似文献