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1.
Structural analysis of Jebel Chemsi and Belkhir located in southern Tunisian Atlas lead to propose the fault-propagation fold as a model for these anticlines. Geometric analogy is settled after dip surveys and observation of several anticline kinks. Several, independent geomorphologic observations support the hinge migration kinematics characterizing this numerical model. The geomorphological hallmarks used matches to (1) alluvial fan progradation, (2) knick points on longitudinal profiles of channel streams and (3) anomalies on the drainage net in the eastern limits of the fold. These anomalies proved a centrifugal hinge migration of, at least, last folding stages in the direction prospected by the model. Results of numerical modelling using Ramp EM software showed detachment layer at 5.5 km that matches to Triassic series. Shortening amplitude is about 2 km for Jebel Chemsi and 1.5 km for Jebel Belkhir. Locally, we highlighted the role of inherited faults in locating and controlling the compressive deformation. In active tectonic region, the use of geomorphological approach is suitable to highlight the folding kinematics and thus to prove the deformation model. In our case study, many special conditions, such as excellent outcropping resulting of arid climate, constant base level and good lithological contrast, allow objective interpretations  相似文献   
2.
Metallothionein was quantified in sea bass Dicentrarchus labrax intraperitoneally (i.p.) injected with different Cu, Cd and Hg doses (50-250 microg kg(-1) wet wt) after 48 h exposure. A distinct peak with 16.8 min retention time was obtained by reversed-phase high performance liquid chromatography coupled to fluorescence detection (RP-HPLC-FD) with the three metals. Total metallothionein levels assayed in unheated liver extracts by RP-HPLC-FD were significantly higher (1.3-1.95-fold) than those obtained by the well-established spectrophotometric method. In the RP-HPLC-FD method, metallothionein increased linearly with Cu and Hg doses, being saturated beyond 100 mug kg(-1) Cd. Maximum induction was obtained at 100 microg kg(-1) Cd (5.3-fold), and 250 microg kg(-1) Cu or Hg (8- and 5.1-fold, respectively). At low doses no metallothionein induction was shown by the less sensitive spectrophotometric assay.  相似文献   
3.
The structural and sedimentological study of fault-propagation folds in Southern Tunisia highlights a special geometry of the growth strata (strata deposited simultaneously with the formation or growth of a fold). This distinct geometry is visible in the uppermost growth-strata beds and consists of one flank with unconformity as opposed to the other flank with perfect conformity. This geometry can be explained by the mechanism of fault-propagation folding, with asymmetrical flank dips and hinge migration kinematics. This kinematics was originally predicted by the fault-propagation fold model, which facilitates the study of this special geometry in a narrow domain of sedimentation-to-shortening ratios. A plot projection provides a generalisation of the results of all types of fault-propagation folds by revealing the expected geometry of the growth strata. This study constitutes one of the most complete examples of kinematic model validation on a field scale.  相似文献   
4.
This study is meant to provide an insight into how discharge playas, which are strongly influenced by a regional salty groundwater flow regime, such as the discharge playa of Sidi El Hani, would respond to the climatic variability and to the materials coming from the subsurface of the Sahel area. In order to choose the appropriate method, a special care was given in this paper to different methods of investigation of the groundwater contribution in water and salt budgets of saline systems. The hydrogeological map of the surrounding aquifers proved their convergence toward Sidi El Hani discharge playa. As consequence of the dominance of a salty groundwater contribution, the climate variability may be considered minor. Accordingly, the model proposed by this study showed the dominance of the salty water coming from the hydrogeology at the expense of the fresh water coming from the climatic contribution. Moreover, according to the adopted model, the effect of the human-induced activity on the hydrogeological contribution such as the installation of dams in the Tunisian center and the overexploitation of the phreatic aquifer of Kairouan was judged increasing the convergence of Kairouan aquifer towards Sidi El Hani discharge playa. On the other hand, the consumption of salt reserves from the discharge playa tends to decrease its salinization.  相似文献   
5.
The modeling study on the Mrihla anticline was carried out using two techniques, i.e., excess area law and balanced cross section. The results show that this structure is likely affected by at least two compressive phases. The interpretation of surface (bedding dips, thickness, lithology, etc.) and subsurface (seismic lines) data along the cross section indicates that the Mrihla structure has a shortening of about 525 m that is evolved above a detachment layer formed by gypsum Triassic formation. The top of this layer is situated at a depth of about 3,890 m from the top of the Aptian dolomitic level, known in Central Tunisian Atlas as Serdj Formation. The kinematic of the investigated structure is a combination of two deformation models. The first is the halokenitic model, defined by the flowing of Triassic ductile material upward toward the surface through the deep Mrihla fault, which is parallel to Mrihla anticline. The second is the fault propagation fold model, characterized by thin-skin deformation mechanics in relation with the movement of the Mrihla fault.  相似文献   
6.
This paper presents the results of an experimental investigation carried out on disturbed clay samples to analyze their creep behavior. The experimental program included compression triaxial tests with varied degree of saturation of the samples and stress level. Triaxial tests were performed at imposed strain rate varied from 0.005 to 0.10%/min. Various stress paths have also been tested including isotropic consolidation and deviatoric stress. The obtained results showed that shear deformation increases with the initial degree of saturation and stress level of clay samples. At fixed stress level and for both isotropic and deviatoric stress paths, the initial degree of saturation and the second invariant of the strain tensor varied with a similar trend. The variation of axial creep strain is correlated with time in a semi-logarithmic function.  相似文献   
7.
In the current research, solidification/stabilization (S/S) treatment of the contaminated soil using hydraulic binders and additives was used to (1) reduce the mobility of organic and inorganic contaminants and (2) compare the ability of various binders in fixing contaminants. The samples were collected from Franco-Tunisian Petroleum Company, located in Sidi Litayem, Sfax (Southern Tunisia). Leaching tests were performed on contaminated soil, containing metallic elements, and hydrocarbons. Calcium aluminate cement (CAC), ordinary Portland cement (OPC), and ground-granulated blast-furnace slag (GGBFS), additives especially the bentonite and water, were used for S/S treatment. The obtained standard specimens were subjected for treating after treatment the leachability of pollutants, compressive strength (CS), and XRD analysis. The results of analysis conducted on contaminated soils showed that concentrations of metallic elements were in the range of 9.08–427 mg/kg and 15,520 mg/kg of organic compound. Next, 10% of the used binder improved the immobilization of pollutants and gave a satisfactory CS exceeding 1 MPa. Thus, the CAC is more effective in reducing the leachability of metal contaminants than OPC + GGBFS and produces much higher strength, which was of the order of 2.41 MPa. The mechanical characterization was confirmed by XRD analysis. The lowest values of organic compounds are presented in mixtures treated by 10% of used binder, indicating the effectiveness of those with the presence of 10% of bentonite. This work shows that 10% (OPC + GGBFS) +?10% bentonite improved the immobilization of metallic elements and hydrocarbons, thus proving its efficiency due to its low cost.  相似文献   
8.
The Jriba trough is an Upper Miocene graben located within the Tunisian offshore Gulf of Hammamet area, east of the Atlas front. This distensive structure suffered a compressive event during the Early Quaternary (Villafranchian). The Jriba structure was previously interpreted as ‘flower structure’, which possibly complicated by halokinetics movements. A new analysis of a set of seismic lines crossing the Jriba trough allows us to propose a new tectonic model where the Villafranchian deformation is characterized by (1) occurrence of a decollement level cutting Messinian to Pliocene layers; and (2) the growth of fault-related folds (fault-propagation fold). The NE–SW Miocene, inherited normal faults, locate the position of the ramps and folds whereas the NW–SE inherited normal faults are reactivated as tear faults. These NW–SE tear faults define various domains of different shortening values (one kilometre at maximum). To cite this article: M. Ben Romdhane et al., C. R. Geoscience 338 (2006).  相似文献   
9.
Abstract

A 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   
10.
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