Tectono-sedimentary events and geodynamic evolution of the Mesozoic and Cenozoic basins of the Alpine Margin,Gulf of Tunis,north-eastern Tunisia offshore     

Fetheddine Melki  Taher Zouaghi  Mohamed Ben Chelbi  Mourad Bédir  Fouad Zargouni 《Comptes Rendus Geoscience》2010,342(9):741-753

The structural pattern, tectono-sedimentary framework and geodynamic evolution for Mesozoic and Cenozoic deep structures of the Gulf of Tunis (north-eastern Tunisia) are proposed using petroleum well data and a 2-D seismic interpretation. The structural system of the study area is marked by two sets of faults that control the Mesozoic subsidence and inversions during the Paleogene and Neogene times: (i) a NE-SW striking set associated with folds and faults, which have a reverse component; and (ii) a NW–SE striking set active during the Tertiary extension episodes and delineating grabens and subsiding synclines. In order to better characterize the tectono-sedimentary evolution of the Gulf of Tunis structures, seismic data interpretations are compared to stratigraphic and structural data from wells and neighbouring outcrops. The Atlas and external Tell belonged to the southernmost Tethyan margin record a geodynamic evolution including: (i) rifting periods of subsidence and Tethyan oceanic accretions from Triassic until Early Cretaceous: we recognized high subsiding zones (Raja and Carthage domains), less subsiding zones (Gamart domain) and a completely emerged area (Raouad domain); (ii) compressive events during the Cenozoic with relaxation periods of the Oligocene-Aquitanian and Messinian-Early Pliocene. The NW–SE Late Eocene and Tortonian compressive events caused local inversions with sealed and eroded folded structures. During Middle to Late Miocene and Early Pliocene, we have identified depocentre structures corresponding to half-grabens and synclines in the Carthage and Karkouane domains. The north–south contractional events at the end of Early Pliocene and Late Pliocene periods are associated with significant inversion of subsidence and synsedimentary folded structures. Structuring and major tectonic events, recognized in the Gulf of Tunis, are linked to the common geodynamic evolution of the north African and western Mediterranean basins.  相似文献   

A thirty-year artificial recharge experiment in a coastal aquifer in an arid zone: The Teboulba aquifer system (Tunisian Sahel)   总被引：1，自引：0，他引：1  

Salem Bouri  Hamed Ben Dhia 《Comptes Rendus Geoscience》2010,342(1):60-74

With the increased demand for groundwater resulting from fast demographic growth, accelerated urbanization, economic and agricultural activity diversification, and the increase of per capita consumption, ground water resources, in particular in coastal regions, remain relatively low, compared to demand. The groundwater quality and piezometric variations result mainly from intensive exploitation, agricultural activities and the intrusion of seawater. This phenomenon is observed mostly in semi-arid areas, such as the oriental Sahel of Tunisia, where an apparent reduction in rainfall in recent years can be seen. Groundwater becomes overexploited especially as its natural recharge by rainwater does not succeed in maintaining the hydrologic balance. The imbalance between water demand and resources induces the degradation of the water quality. In such a case, the artificial recharge of water-table aquifers by water from dams is a credible alternative to improve the hydrodynamic and physicochemical conditions of the groundwater. Like most coastal aquifers, the Teboulba water-table aquifer is threatened by overexploitation for at least three decades. This threat appears by a considerable piezometric level drop and by water salinisation, due to seawater intrusion. Given this alarming situation, since 1971, artificial recharge through wells with surface water from a dam was tested in order to restore the water levels and to improve water quality. The piezometric and chemical surveys of the Teboulba aquifer permitted one to describe the temporal and spatial piezometric and geochemical conditions of the aquifer and to show the effect of the artificial recharge. Indeed, the artificial recharge undertaken since 1971 made the geochemical and piezometric conditions of the Teboulba aquifer improve. This example is a rare, well-documented case-study of the benefits of artificial recharge in a coastal aquifer, over the long term.  相似文献   

Spatial variability of monthly and annual rainfall data over Southern Tunisia   总被引：1，自引：0，他引：1  

Manel Ellouze  Chafai Azri  Habib Abida   《Atmospheric Research》2009,93(4):832-839

  相似文献   

Geochemical behaviour of the Tunisian background aerosols in Sirocco wind circulations     

Chafai AZRI  Habib ABIDA  Khaled MEDHIOUB 《大气科学进展》2009,26(3):390-402

This study examines spatial and time evolutions of the principal constituents of the Tunisian background aerosols under Sirocco wind circulations. Aerosols coming from the Sahara Desert were found to be loaded with particulate matter, especially silicon. The aerosols were shown to have varying geochemical behaviour along the ``South-North" displacement of the Saharan plumes, depending on the wind flow characteristics, geomorphologic features and the nature of soils swept by the wind. In the south and the center part of the country, the transfer of aerosol constituents to the soil (by gravity and/or impaction) was probably predominated by localized enrichment phenomena. The latter are reinforced by the effect of turbulent winds over bare soils, wind wakes and probably selective disintegration, especially in the vicinity of the geomorphologic features of central Tunisia. These relatively high features, extending over important distances, appear to be of paramount importance for the phenomena of redistribution of aerosol constituents even during periods without Sirocco wind circulations. In the northern section of the country, aerosol constituent concentrations dropped to almost 50%, in spite of the abundance of localized turbulent winds. This may be explained by the effect of forests and the relatively dense vegetation cover, which clearly reinforces the transfer phenomena to the soil and the attenuate of dust entrainment.  相似文献   

Tectonique quaternaire et plis de rampe dans le golfe d'Hammamet (offshore tunisien)     

Malika Ben Romdhane  Noureddine Brahim  Jamel Ouali  Éric Mercier 《Comptes Rendus Geoscience》2006,338(5):341-348

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   

Geophysical Constraints on the Location and Nature of the North Saharan Flexure in Southern Tunisia     

Hakim Gabtni  Chokri Jallouli  Kevin Mickus  Hédi Zouari  Mohamed Moncef Turki 《Pure and Applied Geophysics》2005,162(11):2051-2069

Gravity data, integrated with seismic refraction/reflection data, well data and geological investigations, were used to determine the location of the paleogeographic boundary between the Precambrian Saharan domain and the younger Tunisian Atlas domain. This boundary (North Saharan Flexure or NSF) has not been as clearly defined as it has been to the west in Algeria and Morocco. The gravity data analysis, which included the construction of complete Bouguer and residual gravity anomaly maps, revealed that the Atlasic domain is characterized by relative negative gravity anomalies and numerous linear gravity trends implying a thick and deformed sediment cover. The Saharan domain is characterized by relatively positive gravity anomalies with few gravity trends implying a thin and relatively undeformed sediment cover. An edge-enhancement analysis of the residual gravity anomalies revealed that the NSF is characterized by a series of discontinuous east- and northwest-trending linear anomalies south of 34°N that are not related to the well-known faults within the Gafsa and Accident de Medenine regions. Based on the continuity of the amplitudes of seismic reflection data and the trends of the residual gravity anomalies, the NSF is not an abrupt discontinuity but a series of step faults dipping toward the Atlasic domain. To obtain a more quantitative representation of the southern edge of Tunisian Atlas, a regional gravity model constrained by two wells and seismic reflection/refraction data was constructed along a north-south trending profile which confirms the presence of thicker sediments north of the NSF. Our analysis shows that the NSF has controlled the depositional environment of the sedimentary rocks within the region since at least Triassic time and has acted as a barrier to Atlasic deformation south of the NSF. The NSF is considered an important tectonic feature that has controlled the paleogeographic evolution of the southern margin of the Tethys Ocean, and it continues to be active today based on seismicity hazard studies.  相似文献   

Evaluation of the on-site impact of water harvesting in southern Tunisia   总被引：1，自引：0，他引：1  

L. Fleskens  L. Stroosnijder  M. Ouessar  J. De Graaff 《Journal of Arid Environments》2005,62(4):613-630

Water harvesting techniques (WHT) play an important role in water resources conservation in (semi-) arid environments. However, the impacts of WHT are not clearly understood. This paper presents a method to measure increased water availability to olive (Olea europeae) trees grown on the terraced area of a traditional WHT site in southern Tunisia (jessr) and to translate these measurements into effects on yield. Although the WHT were shown to greatly enhance possibilities for olive growing, yields remain dependent on water supply (rainfall+run-on) in spring. Critical factors in the method described are the maximum available soil water capacity (ASW_max), crop and yield response factors (kc, ky_veg and ky_fruit) and the yield consistency index (YCI). Detailed accounts are presented for the costs and benefits of jessr construction and olive production, and the WHT are evaluated using cost-benefit analysis. Difficulties and assumptions are discussed and it is concluded that on-site effects alone might not justify investing in the construction of WHT.  相似文献   

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   

Ammonite-based correlations in the Cenomanian-lower Turonian of north-west Europe, central Tunisia and the Western Interior (North America)     

Claude Monnet  Hugo Bucher 《Cretaceous Research》2007,28(6):1017-1032

The biochronology of Cenomanian-early Turonian ammonite faunas from three key stratotype areas (north-west Europe, central Tunisia and the Western Interior of North America) has been analysed and revised by utilizing the unitary association method. This review is prompted by the huge amount of biostratigraphic data published during recent decades and by a taxonomic homogenisation of the ammonite faunas from these key areas. The Cenomanian and lower Turonian of Tunisia comprise twenty-four Unitary Association zones and the middle Cenomanian-lower Turonian of the Western Interior Basin twenty-three such zones. The unitary association method means a two-fold increase in resolution of these ammonite zonations compared to the standard, empirical schemes. Central Tunisia and the Western Interior are correlated with north-west Europe by constructing a zonation including all taxa common to these areas. These correlations highlight the variable completeness and resolution of the faunal record through space and time, and reveal a significant number of diachronous taxa between the three areas. These correlations enable the designation of a new global marker for the middle/upper Cenomanian boundary, which is characterised by the disappearance of the genera Turrilites, Acanthoceras and Cunningtoniceras and by the appearance of Eucalycoceras, Pseudocalycoceras and Euomphaloceras. The only synchronous datum known is the last occurrence of Turrilites acutus, which may thus be used as a marker for the middle/upper Cenomanian boundary, provided that it does not turn out to be diachronous in the light of any new data.  相似文献   

Iron mineralisation in Mio-Pliocene sediments of the Tamra iron mine (Nefza mining district, Tunisia): Mixed influence of pedogenesis and hydrothermal alteration     

Sophie Decre  Thierry De Putter  Johan Yans  Bchir Moussi  Philippe Recourt  Fakher Jamoussi  Delphine Bruyre  Christian Dupuis 《Ore Geology Reviews》2008,33(3-4):397-410

The Tamra iron mine (Nefza mining district, N. Tunisia) has been exploited for about one century. There are, however, very few publications modelling the mineralisation within this 50 m-thick Messinian–Zanclean sedimentary series. We present the result of a detailed sedimentological, mineralogical and geochemical study on the siliciclastic sediments heavily mineralised in iron. In their present state of preservation, these are rather unusual sediments, wherein most of sedimentological information is obliterated by iron impregnation. The whole series consists of a succession of fining-upward sequences (a few meters in thickness) that are capped by clay-bearing variegated and mottled horizons, each sequence being interpreted as a shallowing-upward sequence topped by an emersive horizon corresponding to a paleosoil. We propose that alteration and/or pedogenesis by the downward percolation of meteoric fluids accounts for most of the initial iron concentration, while a hydrothermal overprint, linked to the neighbouring Miocene magmatic rocks and associated mineral deposits (Sidi Driss Fe–Pb–Zn mine), accounts for the existing extreme iron enrichment. The proposed model is likely to apply to several other iron mines linked to the Miocene magmatic activity in the whole Maghreb area, and especially along the Apenninic thrust front (locally known as Tell-Rif front).  相似文献