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Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule A-sciences De La Terre Et Des Planetes | 2000

Corrélation stratigraphique entre les unités oligo-miocènes de Tunisie centrale et le Numidien

Chokri Yaich; Herman-Jean-François Hooyberghs; Christophe Durlet; Maurice Renard

Abstract Sedimentologic and biostratigraphic studies from the Oligocene to Middle Miocene deposits, exposed in central and north Tunisia, lead to a sequence stratigraphy subdivision of these deposits into several third order depositional sequences. The north–south correlations show that the detrital quartz pebbles appeared much later in central Tunisia (within a ‘fluvial-deltaic’ complex), than in the Numidian in northern Tunisia (characterised by deep submarine channels filled with high density turbidites). Thus, in central Tunisia, the Fortuna Formation (from Rupelian to Lower Burdigalian) could not have supplied Numidian sands from the Saharan region as has been proposed by several authors.


Arabian Journal of Geosciences | 2013

Effect of the groundwater contribution, the climatic change, and the human-induced activities on the hydrological behavior of discharge playas: a case study Sidi El Hani discharge playa, Tunisian Sahel

Elhoucine Essefi; Jamel Touir; Mohamed Ali Tagorti; Chokri Yaich

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.


Life | 2014

Models of Formation and Activity of Spring Mounds in the Mechertate-Chrita-Sidi El Hani System, Eastern Tunisia: Implications for the Habitability of Mars

Elhoucine Essefi; Goro Komatsu; Alberto G. Fairén; Marjorie A. Chan; Chokri Yaich

Spring mounds on Earth and on Mars could represent optimal niches of life development. If life ever occurred on Mars, ancient spring deposits would be excellent localities to search for morphological or chemical remnants of an ancient biosphere. In this work, we investigate models of formation and activity of well-exposed spring mounds in the Mechertate-Chrita-Sidi El Hani (MCSH) system, eastern Tunisia. We then use these models to explore possible spring mound formation on Mars. In the MCSH system, the genesis of the spring mounds is a direct consequence of groundwater upwelling, triggered by tectonics and/or hydraulics. As they are oriented preferentially along faults, they can be considered as fault spring mounds, implying a tectonic influence in their formation process. However, the hydraulic pressure generated by the convergence of aquifers towards the surface of the system also allows consideration of an origin as artesian spring mounds. In the case of the MCSH system, our geologic data presented here show that both models are valid, and we propose a combined hydro-tectonic model as the likely formation mechanism of artesian-fault spring mounds. During their evolution from the embryonic (early) to the islet (“island”) stages, spring mounds are also shaped by eolian accumulations and induration processes. Similarly, spring mounds have been suggested to be relatively common in certain provinces on the Martian surface, but their mode of formation is still a matter of debate. We propose that the tectonic, hydraulic, and combined hydro-tectonic models describing the spring mounds at MCSH could be relevant as Martian analogs because: (i) the Martian subsurface may be over pressured, potentially expelling mineral-enriched waters as spring mounds on the surface; (ii) the Martian subsurface may be fractured, causing alignment of the spring mounds in preferential orientations; and (iii) indurated eolian sedimentation and erosional remnants are common features on Mars. The spring mounds further bear diagnostic mineralogic and magnetic properties, in comparison with their immediate surroundings. Consequently, remote sensing techniques can be very useful to identify similar spring mounds on Mars. The mechanisms (tectonic and/or hydraulic) of formation and evolution of spring mounds at the MCSH system are suitable for the proliferation and protection of life respectively. Similarly, life or its resulting biomarkers on Mars may have been protected or preserved under the spring mounds.


International Scholarly Research Notices | 2013

Hydrocarbons Migration through Groundwater Convergence toward Saline Depressions: A Case Study, Sidi El Hani Discharge Playa, Tunisian Sahel

Elhoucine Essefi; Mohamed Ali Tagorti; Jamel Touir; Chokri Yaich

This paper aims to provide proofs of hydrocarbons migration from petroleum reservoirs towards the surface of discharge playas. This is a case study of the discharge playa of Sidi El Hani, eastern Tunisia. The geochemistry of water of some hydrological drills in the Sahel area and of water from the discharge playa proves relatedness between the deep aquifer and the water of the discharge playa. Thus, the hydrology is now more than likely converging from the subsurface. This convergence may be an agent of transport of hydrocarbons. Concerning the organic matter within the discharge playa, high percentages of different fractions seem abnormal in such a saline context. This maturated organic matter should be viewed in the widest context of a multidisciplinary study taking into account the presence of petroleum potentials in the subsurface, the converging hydrogeology, and the tectonised region. The high percentage of Aromatic Polycyclic Hydrocarbon (APH) may be the result of hydrocarbons migration rather than anthropogenic pollution. As for the reinterpretation of previous works about the organic matter in playas done in sebkha Moknine, the contaminated organic matter, which was interpreted as a human induced activity, may have another origin from a reservoir located in the subsurface of the Sahel area.


International Scholarly Research Notices | 2013

Record of the Climatic Variability and the Sedimentary Dynamics during the Last Two Millennia at Sebkha Dkhila, Eastern Tunisia

Elhoucine Essefi; Jamel Touir; Mohamed Ali Tagorti; Chokri Yaich

This paper aimed to study the record of the climatic variability during the last two millennia within the sebkha of Dkhila. Six climatic stages were recognized along the 104 cm core: the Warming Present (WP), the Late Little Ice Age (Late LIA), the Early Little Ice Age (ELIA), the Medieval Climatic Anomaly (MCA), the Dark Age (DA), and the Roman Warm Period (RWP). The WP stretches along the uppermost 1 cm with a high grey scale as sign of a dry climate. The Late LIA is located between 1 cm and 6 cm. The ELIA is located between 6 cm and 40 cm. The MCA spanning from 40 cm to 72 cm is marked by a sharp increase of the GS revealing a wet period. The DA appears along the part between 72 cm and 84 cm; a shift from light to dark sediments is recorded. The RWP appears between 84 cm and 104 cm. Based on the grain size distribution, two low frequency cycles were identified indicating radical global changes of climatic conditions, the differential tectonics, and the groundwater fluctuations. On the other hand, high frequency cycles indicate local modifications of the climatic conditions.


International Scholarly Research Notices | 2014

Geodynamic Framework of Saline Systems in Eastern Tunisia: Saline Depressions Inherited from the Triassic Intrusions and/or the Messinian Salinity Crisis

Elhoucine Essefi; Jamel Touir; Mohamed Ali Tagorti; Chokri Yaich

Based on the geodynamic context, two hypotheses of origin of salt in the subsurface of the Sahel area are worth being defended. The first suggests that the halokinesis activities, namely, of the Triassic evaporitic sedimentation, may still be until now influencing the functioning of the saline systems in the Sahel. The second integrates the Sahel area geodynamic evolution in the framework of the convergence between African and Eurasian plates. It suggests a link between the blockage of the subduction between African and Eurasian plates in North Tunisia, the Messinian Salinity Crisis, and eventually the concrete opening and evolution of the playa during the Quaternary. Such a suggestion is materialized by a geodynamic model relating successively these events. This scenario suggests that the Messinian Salinity Crisis constituted huge quantities of salt and/or salty water. This saline subsurface reserve is until now influencing the Sahel behavior as a whole. Through groundwater convergence, huge quantities of salt are accumulated within depressions of the Sahel area. Currently, the convergence of the plate between African and Eurasian plates results in a tectonic activity within these saline systems materialized by the formation of fault spring mounds along preferential orientation ensuring the surface-subsurface connectivity.


International Journal of Geophysics | 2014

Magnetic Study of the Heated and Unheated Sedimentary Fillings of Sebkha Mhabeul, Southeast Tunisia: A Geophysical Method for Paleoclimatic Investigation and Tephrochronological Dating

Elhoucine Essefi; Samir Mefteh; Mounir Medhioub; Chokri Yaich

This paper is meant to investigate the climatic and volcanic signals within the sedimentary filling of sebkha Mhabeul through a thermomagnetic study of a 37 cm length core. Values of the magnetic susceptibility at ambient temperature show that the core encompasses four climatic stages: the Warming Present (WP), the Little Ice Age (Late LIA), Early Little Ice Age (ELIA), and the Medieval Climate Anomalies (MCA). Added to the subcycles, the spectral analysis shows the individualization of an 888 yr cycle probably related to solar activity. The heating at 250°C is good-for-nothing since it was useful neither for climatic investigation nor for tephras layers detection. Heating at 700°C generated the complete loss of the climatic signal. On the other hand, it allowed the detection of the previously identified tephras layers. Further, it highlighted the presence of other tephras layers. The extraction by the bromoform confirms the presence of these tephras. The use of the same methodology may allow the detection of tephras layers within other sebkhas.


Planetary and Space Science | 2014

Groundwater influence on the aeolian sequence stratigraphy of the Mechertate–Chrita–Sidi El Hani system, Tunisian Sahel: Analogies to the wet–dry aeolian sequence stratigraphy at Meridiani Planum, Terby crater, and Gale crater, Mars

Elhoucine Essefi; Goro Komatsu; Alberto G. Fairén; Marjorie A. Chan; Chokri Yaich


Journal of African Earth Sciences | 2013

Geochemical controls of groundwaters upwelling in saline environments: Case study the discharge playa of Sidi El Hani (Sahel, Tunisia)

Mohamed Ali Tagorti; Elhoucine Essefi; Jamel Touir; Rihab Guellala; Chokri Yaich


Carnets de Géologie | 2016

Évolution des séries silicoclastiques miocènes en Tunisie centrale : Cas de la coupe de Khechem El Artsouma

Hanene Belghithi; Frédéric Boulvain; Chokri Yaich; Anne-Christine Da Silva

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