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1.
This research is conducted as part of a Spanish International Cooperation Agency project with the aim to investigate the sustainable protection of Tunisian coastal zones, as in the case of Beni Khiar and Dar Chaabane coasts (Hammamet Gulf) separated by Oued El Kebir river. The sedimentary dynamic of these beaches is studied in order to identify the main causes responsible for their erosion by the use of different approaches of in situ measurements and numerical methods. Geophysical surveys and sedimentary analyses have demonstrated that sediments are finer and less carbonated from Beni Khiar to Dar Chaabane. Then, the shoreline mapping of several missions of aerial photos has illustrated a mean shoreline retreat between 3 and 4 m/year. In terms of sand volume, a sediment loss more than 30,000 m3/year at Dar Chaabane has been observed since the hill lake structures were built within Oued El Kebir river in 1996. Finally, modelled hydrodynamic and sedimentary patterns have illustrated the refraction of waves in deep water close to shoals and a high-energy concentration along Dar Chaabane coast. The sediment transport direction is mainly of NE-SW induced by ESE-SE wave-driven alongshore current. Results provided by these approaches have shown the importance of Oued El Kebir sediment yield in supplying the neighbouring beaches. Changes in sedimentary dynamics are affected by the modification of hydrodynamic patters caused by the presence of hydrological dams and the implementations of hotels close to the shoreline. This finding underlines the key role of Oued El Kebir fluvial activity in controlling the equilibrium of beaches and their sensitivity to coastal managements induced by man activities, as in the case of the most Mediterranean beaches. 相似文献
2.
The Hammam Lif coast (North-East of Tunisia) suffered from erosion mainly after the storm that damaged the zone in 1981. To protect it, eight shore-parallel breakwaters were built. The present study is interested in presenting the effect of the protection works on the coastline behavior by using aerial photographs geo-referenced by the digital photogrammetric method and empirical relationships. The successive breakwaters made a general accretion with formation of seven tombolos and salient. The response of the coast to these structures was related to the characteristics of these latter (length, distance to coast, and spacing). The effectiveness of such protection works is shown by the evaluation of the accretion areas formed behind them. The breakwaters which are the longest, less distant from the shoreline, and less spaced formed well-developed tombolos. Whereas, the structures which are short, very far from the coastline, and far from each other caused very small tombolos and even a salient. 相似文献
3.
Nejib Jemmali Fouad Souissi Emmanuel John M. Carranza Torsten W. Vennemann 《Resource Geology》2013,63(1):27-41
The Pb–Zn deposit at Jebel Ghozlane, in the Nappe zone (northern Tunisia), is hosted by Triassic dolostones and Eocene limestones and is located along faults and a thrust‐sheet boundary. The sulfide mineralization of the deposit consists mainly of galena and sphalerite and occurs as vein, stockwork, breccia, dissemination and replacement ores. Three hydrothermal stages are involved in the formation of the ores: stage I is dominated by celestite‐barite, hydrothermal dolomite DII, colloform sphalerite, and galena I; stage II consist of galena II; and stage III contains calcite. Galena in the deposit yielded average 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of 18.705, 15.667 and 38.734, respectively, suggesting a single upper crustal source reservoir for metals. Trace element data indicate the presence of Zn‐ and As‐free galena and As‐rich galena (with 0.2–0.5% As). Sphalerite contains 0.4% As, 0.7–0.9% Cd and 0.1–1.5% Fe. Microthermometric analysis of fluid inclusions in celestite shows that the deposit formed from fluids composed of heterogeneous mixtures of saline (19.5 ± 1 wt% NaCl eq.) aqueous solutions sourced from basinal brines, and gaseous CO2‐rich phases bearing low amounts of CH4, N2 and/or H2S, at temperatures of 172 ± 5°C. 相似文献
4.
Several F, Pb, Zn and Ba deposits are located in the province of Zaghouan in north-eastern Tunisia. They are hosted in Lower
Liassic or Upper Jurassic reef limestones, and the overlying condensed Carixian phosphatic limestones and Campanian marls,
respectively. The mineralization occurs in three types of orebodies: stratiform replacement heaps and lenses (Jebel Stah and
Hammam Zriba), breccia fillings and dissolution void fillings (Sidi Taya) and lodes (Jebel Oust). More than one generation
of fluorite is observed in the stratiform deposits. Microthermometric analyses of the inclusion fluids observed in fluorite
and quartz show that the economic concentrations of fluorite have deposited from moderate to highly saline (12–22.5 wt% NaCl
equivalents) hydrothermal (110–160 °C) mineralizing fluids at the center (Jebel Stah, Sidi Taya) and to the east of the province
(Hammam Zriba). Late remobilizations, observed in the stratiform deposits, are related to the circulation of a warmer (up
to 185 °C) but less saline (10 wt% NaCl equivalents) fluid (Jebel Stah) and more saline (12–22 wt% NaCl equivalents) fluid
(Hammam Zriba). The highest temperature (up to 250 °C) and salinity (32–34 wt% NaCl equivalents) are observed to the west
of the province of Zaghouan (Jebel Oust). Less saline (3–6 wt% NaCl equivalents) and moderately hot to hot fluids (up to 220 ± 20 °C)
and rich in gaseous CO2 invade most of the ore deposits in later stages and give rise to the massive quartz within fractures at Jebel Stah. Chemical
analyses of the fluids extracted from the inclusions occuring in fluorite show compositions dominated by the presence of Na+, Ca2+ and Cl− ionic species and allow the mean temperature of the fluids in the source reservoir to be estimated as 275 ± 25 °C. The circulation
of the ore-forming fluids is triggered by a regional tectonic extensional phase which occurs within the post-Jurassic to ante-Miocene
time interval. The deposition of the economic concentrations of fluorite resulted from the decrease in pressure and temperature
of the hydrothermal brines (Jebel Oust), along with the increase in the dissolved calcium activity (Jebel Stah and Sidi Taya),
or a decrease in salinity due to the mixing with a hot, less saline and Na-poor, Ca-rich fluid (Hammam Zriba). The mineralogical
associations (CaF2, PbS, ZnS, BaSO4) hosted within carbonate rocks, the temperatures and the salinities of the fluids that gave rise to the more important ore
deposits (110–160 °C and 12–22.5 wt% NaCl equivalents), their composition (Na, Ca, Cl) and the molar ratios between the major
ionic species, as well as the presence of liquid hydrocarbons in the mineralizing fluids, show that the ore deposits of the
province of Zaghouan belong to the carbonate-hosted F, Pb, Zn, Ba Mississippi Valley-type deposits.
Received: 23 June 1995 / Accepted: 18 November 1996 相似文献
5.
David Devreker Sami Souissi Juan Carlos Molinero Delphine Beyrend-Dur Fernando Gomez Joelle Forget-Leray 《Estuarine, Coastal and Shelf Science》2010
Annual variability in abundance and population structure of the copepod Eurytemora affinis was studied in the maximum turbidity zone of the Seine Estuary in 2005. An Eulerian sampling strategy was applied monthly from March to July and from September to December. Chlorophyll a and suspended particulate matter (SPM) concentration, copepod abundance and stage distribution, and phytoplankton abundance were measured in sub-surface and near-bottom water during the ebb phase. Total E. affinis abundance was at a maximum in March and April (>200 × 103 ind. m−3), and decreased from May to September (<25 × 103 ind. m−3). This decrease corresponds to annual increases in temperature, salinity, chlorophyll a concentration and phytoplankton abundance, which was dominated by large diatoms, and decreases in SPM and river discharge. The phenology observed in 2005 was almost two months earlier compared to previous studies in the 1990s, when E. affinis reached maximum abundance in May and June. The low proportion of nauplii (<50%) in the population and high abundance of ovigerous females suggests that low recruitment is probably related to anomalously low temperatures in late winter (<5 °C). Whatever the horizontal position of the population in the estuary, adult and late copepodid stages are distributed in higher salinity than naupliar stages. Overall E. affinis population abundance was driven by parameters that characterize water masses at the tidal scale and by river discharge and chlorophyll a at the annual scale. By integrating the tidal effect, the high-frequency sampling protocol used appears to be optimal for investigating annual variability of planktonic communities in megatidal estuaries. 相似文献
6.
7.
This work presents a recent grain size study characterizing superficial sediments of the whole sectors of the Gulf of Tunis which extends from Sidi Ali El Mekki to Sidi Daoued. In this study, a total of 112 samples were collected from different depths following 26 profiles perpendicular to the shore and from rivers. The determination of the proportions of coarse and fine fractions and the interpretation of the grain size results lead to dividing the Gulf of Tunis into two principal coasts: (1) the western coast situated between Sidi Ali El Mekki and Borj Cédria, which is characterized by three sedimentary facies: (a) a sandy facies along the coastline, (b) a mixed facies between Ghar El Melh and Raoued, near the Medjerda River, and between La Goulette and Ezzahra, near the Miliane River, and (c) a muddy facies between Ghar El Melh and Kalâat El Andalous and covered by fine to very fine sands, and (2) the eastern coast, which is characterized by a sandy facies and covered by medium to coarse sands. The dominant N–E and N–W waves generate longshore currents that provide sediment transport following the directions N–S, from Sidi Ali El Mekki to Kalâat El Andalous; SE–NW, from Gammarth to Raoued; NE–SW, from Sidi Bou Saïd to La Goulette and from Sidi Daoued to Bir El Jadi; SE–NW, from Hammam-Plage to Ezzahra; and SW–NE, from Port aux Princes to Rtiba. 相似文献
8.
Nejib Jemmali Larbi Rddad Fouad Souissi Emmanuel John M. Carranza 《Comptes Rendus Geoscience》2019,351(4):312-320
Jebel Mecella and Sidi Taya F–(BaPbZn) deposits are located within the Fluorite Zaghouan Province (NE Tunisia). The mineralization occurs along the unconformity surface between the Jurassic limestones and Upper Cretaceous rocks. The mineralization consists mainly of fluorite, barite, sphalerite, and galena. The δ34S values of barite at Jebel Mecella (14.8–15.4‰) and at Sidi Taya (21.6–22.2‰) closely match those of the Triassic evaporites and Messinian seawater, respectively. The range of δ34S values of galena and sphalerite in both deposits (?6.9 to +2.4‰) suggests the involvement of thermochemical sulfate reduction and possibly organically-bound sulfur in the generation of sulfur. Lead isotope data with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.893–18.903, 15.684–15.699, and 38.850–38.880, respectively suggests a single homogeneous source reservoir of Paleozoic age and/or the homogenization of the Paleozoic–Cretaceous multireservoir-derived fluids along their long migration paths to the loci of deposition during the Alpine orogeny. 相似文献
9.
The tidal flat of Nakta is located in the northern part of the gulf of Gabes and in the southern coast of Sfax. It corresponds to a flat reef protected from less topography, with a slope ranging between 2° and 4°, which borders the Gargour Wadi. The study sector is renowned to have moderate hydrodynamics which lasts almost for two millenary (14C isotopic dating).The sedimentological study of the Nakta tidal flat revealed different facies: fine-grained sand in the intertidal zone and carbonated muddy sand in the infratidal zone.Equilibrium state of the Nakta ecosystem depends entirely on tide currents, which mainly inhibit drift currents. The Nakta tidal flat is characterized by a variety of faunal species (Cerastoderma glaucum, Arca noe, Cardita antiquatus, Chlamys varied, Ruditapes deccussatus, Tapes rhomboids, Pinctada radiate, etc.) and floristic diversities (Halocnemum strobilacum, Halimione portulacoides, Enteromorpha linza, Ulva rigida, Cymodocea nodosa, Posidonia oceanica). The species are abundant in the infratidal zone, while in its intertidal zone, faunal species remain little diversified and are dominated by limivorous diggering.The paleogeographic study of the Nakta tidal flat showed the alternation of regression and transgression periods. 相似文献
10.
Mohamed Jalal El Hamidi Abdelkader Larabi Mohamed Faouzi Mohamed Souissi 《Arabian Journal of Geosciences》2018,11(5):104
In many countries of the world, groundwater is the main source of water in arid and semiarid regions. The scarcity of water is one of the main issues in Morocco. The coastal aquifer system of Rmel-Oulad Ogbane is recognized as one of the most important aquifers in Morocco and is very well known for their role in industrial, economic, and social development. However, this role is confronted to climate change impacts and heavy abstraction rates leading to a major decline in the groundwater levels and may eventually cause a deficit water balance of the aquifer as well as a degradation of the freshwater quality by seawater intrusion. The objective of this research is to identify and evaluate the distribution and spatial changes of regionalized variables on reservoirs and groundwater resources using geostatistical analysis in Geographic Information System (GIS) software. The prediction of these variables was performed using an interpolation method: ordinary kriging in a GIS. The normality test and trend analysis were applied to each variable to select the appropriate semivariogram model (SVM) and check the results using cross-validation (CV). Hence, several kriged maps of reservoirs and water resources have been produced to be exploited by the decision maker. The studied variables related to reservoirs and hydrodynamic data have a strong spatial dependence, which show correlations in specific direction, while the hydrochemical data are mainly related to groundwater mechanisms, such as advective-diffusive transport, without any autocorrelation between data. 相似文献