Jamel Touir

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

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.

Cypridea Bosquet, 1852 (Ostracoda) in the Early Albian of Tunisia

Fig. 1 Cypridea gr. laevigata (Dunker, 1946), sample K6, Early Albian, Jebel Kebar. 1, carapace, right lateral view, specimen J. Keb. 0001 (L = 1.0 mm). 2, carapace, right lateral view, specimen J. Keb. 0002 (L = 1.1 mm). The sub-cosmopolitan limnic ostracod genus Cypridea Bosquet, 1852 ( sensu Horne & Colin, 2005) is known from the Lower Tithonian (Martin-Closas et al ., 2008) to the Aptian, with a maximum development during the Berriasian to Barremian (Horne, 1995), in Europe, Africa, the Middle East, North and South America. In the Far East (China, Mongolia) and Alaska it ranges up to the Cretaceous–Tertiary boundary (Brouwers & De Deckker, 1993; …

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

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.

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

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.

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

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.

Diagenetic process as tool to diagnose paleo-environment conditions, bathymetry and oxygenation during Late Paleocene-Early Eocene in the Gafsa Basin

Abstract Late Paleocene–Early Eocene deposits cropping out in Tamerza area were settled on a carbonate homoclinal ramp. Deposits which are ranged in six main facies record a gradual transition from intertidal to upper circatidal environment. Lateral variations in terms of facies and thickness infers to the main role of synsedimentary tectonics. The characterization of paleoenvironments was established in respect to the lithology, fauna content, sedimentary structures and diagenetic features. Detailed analysis of deposits shows that the diagenetic processes are reliable tools to reconstruct each depositional environment. Moreover, they bring out precious information concerning the chemical and physical parameters and the sedimentary dynamics of the studied interval. The early stage cementation is favored under low rates of sedimentation and a calm sea floor. The arrangement and the morphology of crystals permit to appreciate the bathymetry and to better characterize the depositional environment. Phosphogenesis seems in a tight relation with silicification requiring both an acidic environment. The occurrence of upwelling currents engendered the blooming of fauna guarantying test preservation after death and allowed to establish a linkage between fauna content and diagenetic features. Silicification processes concern test replacement and the genesis of chert beds included within the enclosing deposits. Micritization processes, occurring in the inner ramp, advocate calm environments and are engendered by endolithic algae, bacteria and fungi. The X-Ray diffraction shows the frequency of smectites associated with clinoptilolites, sepiolite and palygorskite. The clay paragenesis helps to identify several diagenetic contexts occurring under xeric and confined conditions.