Office National des Mines

Tunis, Tunisia

Office National des Mines

Tunis, Tunisia
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Belkhiria W.,Office National des Mines | Belkhiria W.,Tunis el Manar University | Boussiga H.,Tunis el Manar University | Boussiga H.,University of Carthage | Inoubli M.H.,Tunis el Manar University
Tectonics | Year: 2017

The transition zone between western and central Mediterranean domains presents a key area to investigate kinematic interactions within the adjacent orogen systems such as the easternmost Atlas foreland-and-thrust belt. Gravity and seismic data revealed a highly structured basement, characterizing a series of structural highs and lows delimited by high-angle N-S, E-W, and NW-SE extensional faults. This basement architecture is inherited from successive extensional events related to the openings of the Triassic-Early Cretaceous Tethys oceans (i.e., Alpine Tethys, Ligurian Tethys, and Mesogea). Throughout this period, this mosaic of continental blocks significantly controlled the thickness and facies distributions. Early stages of diapirism took place along these basement faults and allowed maximum subsidence in minibasins revealed by the development of growth strata. In response to the Late Cretaceous-Eocene shortenings, these extensional faults have been reactivated as trasnpressional shear zones, giving rise to narrow pop-up structures. In addition, gravity modeling indicates crustal thinning and deep-rooted faults affecting the crust south of the Zaghouan Thrust and along E-W transfer zones. From the late Miocene, a drastic change in the stress regime is attributed to the effect of the adjacent Sicily channel on the study area. This promotes crustal thinning, basin subsidence, and channeling up of mantle-derived helium along lithospheric-scale weak zones. Our results give rise to new insights into the reactivation of inherited weakness zones of southern Tethys margin in response to the complex interaction between African and Eurasian plates accommodated by subduction, rollback, collision, and slab segmentation. ©2017. American Geophysical Union. All Rights Reserved.

PubMed | French National Center for Scientific Research, Office National des Mines, University of Carthage and University of Calgary
Type: Journal Article | Journal: Ecotoxicology (London, England) | Year: 2016

The present study investigates the quality of surface sediments from the Bizerte lagoon (North Tunisia) using an integrated approach including chemical contaminant analysis, bioassays and sediment quality guidelines (SQGs). Sediment samples were collected at 9 sites and analyzed for eight heavy metals (Hg, Cd, Cr, Cu, Pb, Zn, Ni, Fe and Mn). PAHs, PCBs, OCPs were measured previously in the same sediment samples. Our results indicated that the highest concentrations of metals were found near urban areas due to the municipial and industrial wastewater discharges. Sediment pollution assessment was carried out using geoaccumulation index and enrichment factor, which indicate a widespread pollution by Cd, Pb, Ni and Zn in the studied sediments. For bioassays, aqueous and organic extracts were used to assess toxicity and genotoxicity in sediments by using Microtox() and SOS Chromotest, respectively. Toxicity levels were compared to metallic and organic pollutants contents. Our results highlight differences in the pattern of responses between the different assays and show no correlation with all the studied contaminants, emphasizing the influence of other contaminants not analyzed in the present study. Based on SQGs, the results of toxicity assessment indicated that adverse effects caused by Ni and Zn would be expected frequently. Nickel was found to have the highest predicted acute toxicity, followed by Zn, Pb, Cd, Cu and Cr. There was no significant relationship between sediment toxicity calculated from heavy metal concentrations (SQG approach) and those measured with bioassays. These findings support the use of integrated approachs for evaluating the environmental risks of sediments.

Othmani M.A.,Laboratory of Materiaux Utiles | Othmani M.A.,Tunis el Manar University | Souissi F.,Laboratory of Materiaux Utiles | Benzaazoua M.,University of Québec | And 3 more authors.
Mine Water and the Environment | Year: 2013

Flotation tailings associated with the extraction of Pb and Zn in the Touiref mining district, Tunisia, contain galena, sphalerite, pyrite, and marcasite in a carbonate gangue. The geochemical behaviour of oxidized and unoxidised tailings were consistent with their mineralogical and chemical characteristics. The leaching proceeded under neutral to slightly alkaline condition (pH 7. 3-8. 5), and positive Eh (250-470 mV). The concentrations of sulfate and Ca released during the leaching tests were associated with the neutralization of acidity by carbonates and the dissolution of gypsum initially present in the tailings. The iron precipitated, but significant amounts of Zn (5-3,300 μg/L), Cd (3-18 μg/L), and Pb (28-83 μg/L) were released during leaching, with the latter two exceeding international environmental norms (5 μg/L for Cd and 10 μg/L for Pb). © 2012 Springer-Verlag Berlin Heidelberg.

Fanti F.,University of Bologna | Cau A.,Museo Geologico Giovanni Capellini | Hassine M.,Office National Des Mines
Journal of African Earth Sciences | Year: 2014

Isolated sauropod remains including vertebrae and a humerus from the Aïn El Guettar Formation (Albian, Early Cretaceous) of Tunisia are described. Vertebrae include a slightly procoelous anterior caudal vertebra, amphicoelous middle caudal vertebrae, and strongly procoelous distal caudal vertebrae. The humerus has an anteroposteriorly compressed shaft, robust deltopectoral crest restricted laterally and prominent condyles bounding a distinct distal fossa. The morphological characters present in the specimens suggests that isolated remains can be referred to at least two distinct sauropod taxa.The anterior caudal vertebra is referred to Rebbachisauridae, whereas remaining caudal vertebrae show titanosauriform and titanosaurian derived features (anteriorly placed neural arches and, in the posterior vertebrae, distincly procoelous centra); finally, the humerus may pertain to a somphospondylian titanosauriform, perhaps the same taxon represented by the middle and posterior caudal vertebrae. This study introduces some of the oldest titanosauriform remains from Northern Africa and provides additional data on the stratigraphic and geographic distribution of this clade during the Early Cretaceous. © 2013 Elsevier Ltd.

Fanti F.,University of Bologna | Cau A.,Museo Geologico Giovanni Capellini | Hassine M.,Office National des Mines | Contessi M.,University of Bologna
Nature Communications | Year: 2013

Recent interpretations of the postcranial anatomy of sauropod dinosaurs differ about pneumatic features supporting an avian-like ventilatory system; the most conservative workers reject most postcranial pneumatizations as being unambiguous evidence of abdominal air sacs. Here we describe the first articulated dinosaur skeleton from Tunisia and refer it to a new rebbachisaurid sauropod, Tataouinea hannibalis gen. et sp. nov. The Tunisian specimen shows a complex pattern of caudosacral and pelvic pneumatization-including the first report of an ischial pneumatic foramen among Dinosauria-strongly supporting the presence of abdominal air sacs. Character optimization among Rebbachisauridae indicates that in the caudal vertebrae, pneumatization of the neural arches preceded that of the centra; in the pelvis, pneumatization of the bones adjacent to the sacrum preceded that of more distal elements. Tataouinea was more closely related to European nigersaurines than to otherwise Gondwanan rebbachisaurids; this supports an Afro-European route for rebbachisaurid dispersal. © 2013 Macmillan Publishers Limited. All rights reserved.

Boussen S.,Tunis el Manar University | Sghaier D.,Tunis el Manar University | Chaabani F.,Tunis el Manar University | Jamoussi B.,Laboratoire Central dAnalyses et dEssais | And 2 more authors.
Applied Clay Science | Year: 2015

Clay deposits of the Aleg formation (Jebel Romana of the northern Chotts range, southern-east Tunisia) were sampled and investigated for their, mineralogical, chemical, rheological, and physical characteristics to develop their potential use as drilling mud. X-ray diffraction revealed a predominance of smectite (≥90%) with minor amounts of kaolinite and illite. Calcite, quartz and gypsum were also detected. Results show that the main oxides in the samples were SiO2, Al2O3, and Fe2O3, whereas the other oxides were present only in small quantities. However, the relatively high Na2O and MgO content is also one of the favorable points considered in terms of swelling and viscosity features. Standard tests show that the rheological behavior of the clay suspensions is unsuitable for preparing drilling muds. Therefore, the activation of these clays was performed using the most popular Na2CO3 in a wet condition. The drilling muds qualities of the Upper Cretaceous smectite-rich clay from Jebel Romana, significantly improved with additive sodium carbonate. The Ca-montmorillonite was completely converted into Na-montmorillonite after addition of 3% Na2CO3. The activation of the Aleg clay with soda influenced the viscosities, swelling indices and specific surface area. The optimum conditions for the preparation of high quality materials for drilling mud were investigated by studying the effects of clay minerals percentage, Na2CO3 concentration, activation time and temperature. Commercial bentonite samples imported from Algeria (A.G) were also included as reference materials. The optimum parameters for activation can be achieved under the operating conditions of 3% Na2CO3 concentration, 60min activation time, 75°C heating temperature and clay concentration of 75g/l. Under these conditions, the rheological and physical properties including apparent viscosity, surface area and swelling index showed a maximum values. Therefore, by alkali activation, it is possible to upgrade smectite from Jebel Romana to meet the minimum API viscosity (15cp); mud yield value (90barrels/sh.ton) and swelling index (22ml) standards. In addition, the apparent viscosity and mud yield efficiency was obtained around pH10, as 18cp, 101.93 (barrels/sh.ton), respectively. So, to achieve higher quality, optimization needs to be carried out in the formulation of batches or in the processing conditions. The utilization of these clays, after their upgrading and activation, can represent a value-added to the Tunisian economy by preventing the importation of bentonite. © 2015 Elsevier B.V.

The detailed study of the Sidi Kralif Formation in Jebel Meloussi allowed to identify the principal zones and subzones of calpionellids and ammonites in the Lower to Middle Berriasien. Thus, the B2, B3, C1 and C2 subzones of calpionellids, the Grandis Subzone and Occitanica Zone of ammonites have been well characterized. Calpionellids associations of biozones of the studied section were compared with the associations reported in other regions of the globe, particularly the South-East of France and the external Rif (Morocco).

Kadri A.,University of Carthage | Essid E.M.,Office National des Mines | Merzeraud G.,Montpellier University
Journal of African Earth Sciences | Year: 2015

The emergent domain known as "Kasserine Island" in central Tunisia, to the West of the North-South Axis, was emerging during the Turonian. This area has undergone several changes during the Cretaceous-Eocene period. In the present study, the compilation of surface and sub-surface data provided new information about the boundaries variations of the emerged domain. The analysis of paleogeographic maps allowed the identification of three distinct stages of evolution. The first stage extents from the Middle Turonian to the Lower Maastrichtian where the emergent domain covers the area extending from Jebels Selloum-Sidi Aich in the West to Jebel Bouhedma in the East. The boundaries of this area coincide with the E-W Kasserine fault to the North, the N-S Lessouda-Boudinar fault in the East and the N 120 el Mech-Souinia flexure at the South. This emersion contemporaneous with a high eustatic level is most likely related to tectonic activity. The extensional tectonic regime that is characterized by a NE-SW minimal horizontal stress, has reactivated border faults with a normal component. The interference of the tilting of these border faults was at the origin of the emergence of this domain. The ascent of the Triassic salt may also have contributed in this uplift.In the second stage, the emerged domain has reached its maximum expansion to the North, the West and the South during the Middle Maastrichtian-Paleocene period. Its northern limit is irregular, while the southern limit coincides with the N120 Gafsa fault and the E-W fault of Jebels Orbata-Bouhedma. The N-S Lessouda-Boudinar fault forms the eastern limit. This expansion is mostly related to the global eustatic fall that is well characterized during this period, and partly to the compressive tectonic activity.The Lower Eocene is characterized by a marine transgression that has interested the northern edge of the Island, where the Ypresian deposits are discordant on older series. This edge was irregular and marked by the Gulf of Sbiba. The eastern, the southern, and the western boundaries kept the same shape as that of the previous stage. The compressive tectonic regime, characterized by a NW-SE maximum horizontal stress, is accentuated. This constraint state has generated NE-SW folds and NW-SE grabens. Some of these structures allowed the accumulation of a thick phosphate deposits at their edges, and continental deposits in the emerged area.During the Middle to Upper Eocene, the emergent area narrowed further at the North. The deposits are transgressive and discordant on older series. The Other limits always coincide with the Gafsa fault, the Jebels Orbata-Bouhedma and Jebels Lessouda-Boudinar faults. This period is characterized by the filling of the Gafsa basin by evaporate deposits before its emergence in the Oligocene. As a result, the southern-central Tunisia emerged as one area. © 2015 Elsevier Ltd.

Benoit J.,Montpellier University | Adnet S.,Montpellier University | El Mabrouk E.,Office National des Mines | Khayati H.,Office National des Mines | And 6 more authors.
PLoS ONE | Year: 2013

Sea cows (manatees, dugongs) are the only living marine mammals to feed solely on aquatic plants. Unlike whales or dolphins (Cetacea), the earliest evolutionary history of sirenians is poorly documented, and limited to a few fossils including skulls and skeletons of two genera composing the stem family of Prorastomidae (Prorastomus and Pezosiren). Surprisingly, these fossils come from the Eocene of Jamaica, while stem Hyracoidea and Proboscidea - the putative sister-groups to Sirenia - are recorded in Africa as early as the Late Paleocene. So far, the historical biogeography of early Sirenia has remained obscure given this paradox between phylogeny and fossil record. Here we use X-ray microtomography to investigate a newly discovered sirenian petrosal from the Eocene of Tunisia. This fossil represents the oldest occurrence of sirenians in Africa. The morphology of this petrosal is more primitive than the Jamaican prorastomids' one, which emphasizes the basal position of this new African taxon within the Sirenia clade. This discovery testifies to the great antiquity of Sirenia in Africa, and therefore supports their African origin. While isotopic analyses previously suggested sirenians had adapted directly to the marine environment, new paleoenvironmental evidence suggests that basal-most sea cows were likely restricted to fresh waters. © 2013 Benoit et al.

Benoit J.,Montpellier University | Essid E.M.,Office National des Mines | Marzougui W.,Office National des Mines | Khayati Ammar H.,Office National des Mines | And 3 more authors.
Journal of Human Evolution | Year: 2013

We report the discovery of three isolated primate petrosal fragments from the fossiliferous locality of Chambi (Tunisia), a primate-bearing locality dating from the late early to the early middle Eocene. These fossils display a suite of anatomical characteristics otherwise found only in strepsirhines, and as such might be attributed either to Djebelemur or/and cf. Algeripithecus, the two diminutive stem strepsirhine primates recorded from this locality. Although damaged, the petrosals provide substantial information regarding the ear anatomy of these advanced stem strepsirhines (or pre-tooth-combed primates), notably the patterns of the pathway of the arterial blood supply. Using μCT-scanning techniques and digital segmentation of the structures, we show that the transpromontorial and stapedial branches of the internal carotid artery (ICA) were present (presence of bony tubes), but seemingly too small to supply enough blood to the cranium alone. This suggests that the ICA was not the main cranial blood supply in stem strepsirhines, but that the pharyngeal or vertebral artery primitively ensured a great part of this role instead, an arterial pattern that is reminiscent of modern cheirogaleid, lepilemurid lemuriforms and lorisiforms. This could explain parallel loss of the ICA functionality among these families. Specific measurements made on the cochlea indicate that the small strepsirhine primate(s) from Chambi was (were) highly sensitive to high frequencies and poorly sensitive to low frequencies. Finally, variance from orthogonality of the plane of the semicircular canals (SCs) calculated on one petrosal (CBI-1-569) suggests that Djebelemur or cf. Algeripithecus likely moved (at least its head) in a way similar to that of modern mouse lemurs. © 2013 Elsevier Ltd.

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