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Tunis, Tunisia

Mahmoudi S.,Faculte des science de Gabes | Srasra E.,Center des Materiaux | Zargouni F.,Departement de Geologie
Journal of African Earth Sciences

The Valangenian-Hauterivian clays of Tunisia located at Djebel Oust were characterised by chemical analysis, X-ray diffraction and scanning electron microscopy in order to determine if these clays are appropriate for the manufacturing of ceramic products for construction. The mineralogical study shows that these clays are mainly of illitic type. However, other clay minerals, such as kaolinite, I/Sm mixed-layer, and chlorite, are also present. The chemical analysis indicates that the clays are notably siliceous, carbonated and aluminous. The content of iron is variable. Under firing tests on clay raw material until 1200. °C, quartz, cristobalite, hematite, mullite and sillimanite minerals were also identified. The amount of interstratified I/Sm and chlorite is higher in the samples located at the west zone of Djebel Oust than those located at the east. However, under firing behaviour of both types of raw samples seems to be similar. As conclusion of this study, these clays meet the firing specifications required for the manufacturing of ceramic products for construction. © 2010. Source

Achiba W.B.,Laboratoire Traitement et Recyclage des eaux usees | Lakhdar A.,Laboratoire Traitement et Recyclage des eaux usees | Gabteni N.,Departement de Geologie | Laing G.D.,Ghent University | And 5 more authors.
Journal of Hazardous Materials

A field plots experiment was carried out to assess the effects of repeated application of municipal solid waste compost in comparison to farmyard manure on the accumulation and distribution of trace metals, as well as organic carbon and nitrogen in Tunisian calcareous soil. Compared with untreated soil, the application of the two organic amendments significantly increased the organic carbon and nitrogen contents of the soil. Particle-size fractionations showed that carbon and nitrogen were mainly found to occur in the macro-organic matter fraction (80%). The two organic amendments significantly increased organic carbon in the macro-organic and mineral >150 μm fraction and the 150-50 μm fraction, as well as the organic nitrogen in 150-50 μm and macro-organic fraction. Compared with farmyard manure, municipal solid waste compost significantly increased total Cd, Cu, Pb and Zn contents in the topsoil. These trace metals were mainly present in the macro-organic matter fraction. Significant increases of Cu, Zn and Pb were detected in the 150-50 μm, <50 μm and macro-organic fractions after application of municipal solid waste compost. A significant increase of Cd content was only observed in the 150-50 μm fraction. The trace metals also showed different fractionation patterns when the BCR sequential extraction scheme was applied on untreated and compost-treated soil. The residual fraction was found to be the major fraction, especially for Cu, Cr, Ni and Zn. In contrast, Cd was mainly present in the acid-extractable and reducible fraction, whereas Pb was mainly associated with the reducible fraction. © 2009 Elsevier B.V. All rights reserved. Source

Rigaud S.,Departement de Geologie | Blau J.,Institute For Geowissenschaften | Martini R.,Departement de Geologie | Rettori R.,University of Perugia
Acta Palaeontologica Polonica

Early Jurassic aragonitic foraminifers are outstandingly well-preserved in the Marmorea crust, a multiphased ferromanganese layer limiting the Schnöll and Adnet formations (Adnet, Northern Calcareous Alps, Austria). This remarkable preservation, related to the pervasive impregnation of aragonitic tests prior to their recrystallization, allowed observing unknown diagnostic features of the genus Involutina, which typifies the Suborder Involutinina. Thanks to a detailed examination of the Adnet specimens, this paper clarifies the taxonomy, systematic position, and phylogeny of Involutina. A new diagnosis, structural model, and lineage are introduced for the group. Involutina is the direct descendant of Aulotortus and the two taxa probably showed a parallel evolution. As Aulotortus, Involutina presents a high intraspecific variability and its diversity must be revised downward. Current phylogenetic and taxonomic frames of the Suborder Involutinina are firmly questioned as, contrary to previous schemes, the type-genus possesses more than one lamellar deposit per whorl. In Involutina, the height and distribution of papillae on the test surface is not random and probably related to a biological function. We here propose that the papillose lamellae and tube infoldings that characterize representatives of the genus were rudimentary features for light catching and symbiont positioning, respectively. Copyright © 2015 S. Rigaud et al. Source

Roldan F.J.,Instituto Geologico Y Minero Of Espana | Galindo-Zaldivar J.,University of Granada | Ruano P.,University of Granada | Chalouan A.,Mohammed V University | And 8 more authors.
Journal of Geodynamics

The Volubilis Basin is located between two structural arcs formed by the Prerif Ridges that developed during and after sedimentation. The arcs correspond with W- to WSW-verging anticline culminations, limited, to the north by a NE-SW strike-slip lateral ramp. Sedimentary infill took place during two stages of ridge formation and propagation. The first stage occurred in the Middle Miocene-early Tortonian and was determined by the deposition of the Nappe Prérifaine in the northern part of the basin, and continental and marine sediments over the Prerif Ridges. The second one, Late Miocene in age (Tortonian-Messinian), corresponds to the sedimentation of calcarenites and bioclastic limestones at the basin edges, with a lateral transition to white and blue marls toward the center of the basin. There is clear evidence of synsedimentary deformation, suggesting the interaction of sedimentation and tectonics. Geophysical data allow us to characterize the stratigraphic architecture of the Volubilis Basin and the geometry of the top of the Paleozoic basement. An approximately N-S Tortonian-Messinian asymmetric depocenter is located close to the front of the eastern arc. This research illustrates the nucleation, progressive thrust bending and segmentation, and the propagation of folds interacting with sedimentation. Thrust nucleation agrees with Paleozoic basement highs under the detachment surface. The progressive development of these tectonic structures conditioned the formation, segmentation and final continentalization of the Volubilis Basin, which can be considered as a piggy-back basin. © 2013 Elsevier Ltd. Source

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