Study of a Neogene basin dynamics: The “Bizerte basin”, northeastern Tunisia: relevance to the global Messinian Salinity Crisis     

Salah Harrab  Beya Mannai-Tayech  Mohsen Rabhi  Fouad Zargouni 《Comptes Rendus Geoscience》2013,345(5-6):251-261

The Messinian sediments of northeastern Tunisia were deposited under an active tectonic setting. They are organized in sequences indicating a transitional deposit from margin – littoral to lacustrine – continental facies. These series unconformably overlie the Serravallian–Tortonian silty clays packages, and are overlain by the transgressive Early Pliocene marl (Zanclean). The presence of evaporitic strata points out to the Messinian Salinity Crisis described in the peripheral basins of the western Mediterranean. The Messinian sedimentation was found to have been closely controlled by transtensive tectonics and differential subsidence at a large spatio-temporal scale. It is organized in sequences typical of a depositional environment controlled by eustatism, tectonic and maybe by climate changes. Despite the existence of some local specific sedimentological characteristics, our results corroborate previous findings that pointed out to the Messinian times as a singular period all around the Mediterranean Basin. Field and subsurface seismic profile data helped reconstructing either the sedimentary or tectonic unconformities existing between the studied Messinian series and older Neogene successions.  相似文献   

Filtering of the gravimetric anomalies to the study of the geological structures of Oued Zarga (Septentrional Tunisia): structural implications     

Amira Ayed-Khaled  Mohamed Ghanmi  Fouad Zargouni 《Arabian Journal of Geosciences》2012,5(1):169-180

Gravity data were analysed in the Northern Tunisian Atlas (case study of Oued Zarga area) to better understand the organization of its underlying structures. The gravity data analysis included the construction of a gravity anomaly maps and two and a half dimensional gravity model. The qualitative analysis of gravimetric maps served for the foundation of a new structural map of the study region that constitutes a new contribution of the gravimetry in this present work. In addition, the complete Bouguer and residual gravity anomaly maps indicate a negative gravity anomaly over the Triassic evaporitic outcrops of Jebel Guerouaou and prominent NE?CSW-trending features associated with the boundary of the Triassic rocks and surrounded layers. A NW?CSE-trending gravity model that crosses the Triassic evaporitic outcrop at Jebel Guerouaou can be explained by a deep-rooted salt diapir.  相似文献   

Book reviews     

Tietze  Wolf  Moewes  Gabriele  Ibrahim  Fouad 《GeoJournal》1983,7(3):320-320

  相似文献   

Book reviews     

Hans-W. Windhorst  Fouad Ibrahim  A. Wallner 《GeoJournal》1983,7(2):196-196

  相似文献   

Mode de mise en place des corps salifères dans l'Atlas septentrional de Tunisie. Exemple de l'appareil de Bir Afou     

Mohamed Ben Chelbi  Fetheddine Melki  Fouad Zargouni 《Comptes Rendus Geoscience》2006,338(5):349-358

30 km southwest of Tunis, two thin flaky ‘Triassic’ intrusions underline the two flanks of the Atlasic anticline of Bir Afou. These evaporites are interbedded within the Clansayesian shales, and are under and overlain by glauconitic conglomeratic contacts. The ‘Triassic’ flakes, topic of our study, are sourced from the Bir Afou Triassic mass after a rapid pouring out during Late Aptian extensional tectonics. This structure corresponds, for us, to a ‘salt glacier’, similar to that one described at Ben Gasseur by Vila and al. [J.M. Vila, M. Ben Youssef, M. Chikhaoui, M. Ghanmi, Bull. Soc. géol. France 167 (1996) 235–246], which was subsequently folded during Lower Eocene times. Middle and Upper Eocene transgressive formations unconformably deposited on top of the Aptian anticlinal hinge. The major Late Miocene compressive phase is responsible for the present structures and that are superimposed onto the pre-existing ‘salt glacier’. This salifereous system extends the ‘salt glacier’ domain towards the eastern part of the Tunisian Atlas. To cite this article: M. Ben Chelbi et al., C. R. Geoscience 338 (2006).  相似文献   

Electrical properties of opal-CT     

Liberto de Pablo-Galán  Mari´a Lourdes Chávez-Garci´a  Alfonso Huanosta Tera 《Physics and Chemistry of Minerals》1997,24(2):90-101

 The electrical properties of opal-CT are validated at temperatures from 600 to 840 °C and frequencies from 5 Hz to 10 MHz. The opals are hydrothermal, containing less than 11270 ppm total of Al, Fe, Ca, Na, and K, and from 1.17 to 17.63 wt% H₂O interstitial and structural. Opal-CT shows fine crystallites, measuring from 19.4 to 22.7 μm, of an ordered tridymite-M stratification with high-cristobalite, embedded in a non-crystalline matrix. When heated to 600 °C, the non-crystalline phase devitrifies to the same stacked high-cristobalite-tridymite-M crystals. Opals containing less than 2070 ppm of cationic impurities are characterized by one single high-frequency complex impedance arc corresponding to the bulk polarization of the crystalline phase, of capacitances between 25 and 30×10⁻¹² F and resistances from 132 to 890 ohm. Opals having over 6300 ppm of cationic impurities show two superimposed high- and low-frequency complex impedance arcs. The high-frequency arc corresponds to the bulk polarization of the crystalline phase, of capacitance between 8 and 15.7×10⁻¹² F and resistance from 14 to 236 ohm, less than the capacitance of 0.25 to 0.53×10⁻⁹ F and resistance from 26 to 360 ohm of the non-crystalline minor intergranular material represented by the low-frequency impedance arc. The electric module shows one single vertex, ascribed to the bulk polarization of the crystalline phase. The conductivities are from 10⁻⁷ to 10⁻⁴ ohm⁻¹cm⁻¹, in the range of poor ionic conductors, essentially constant below 1.8 kHz, rapidly increasing at higher frequencies, due to ionic and electronic charge carriers. The activation energy changes between 0.905 and 1.003 eV for the conduction mechanism in the crystalline phase and from 0.924 to 1.087 eV in the non-crystaline phase. X-ray diffraction and impedance spectroscopy confirm that opal-CT is a crystalline stacked sequence of tridymite-M and cristobalite-high, in a non-crystalline matrix. Received October 20, 1995/Revised, accepted June 15, 1996  相似文献   

The Maasai Herbalists in Arusha Town, Tanzania     

Fouad Ibrahim  Barbara Ibrahim 《GeoJournal》1998,46(2):141-154

This paper presents the findings of a case-study carried out on the Maasai herbalists of Arusha town, whose social and economic situation, both in their villages of origin and in town is being analysed. Special emphasis is laid on the struggle of women herbalists to upgrade their low economic and social status in their home villages and, at the same time, satisfy their most basic needs in town. In this, they depend on their asset of indigenous ethnomedical knowledge, which they commercialise. They do not consider themselves professional experts among their own people, but they become ones when they are in town. A major aim of this paper is also to illustrate the wealth of indigenous knowledge concerning the biodiversity of people's environment. A survey of the medical plants most frequently sold by the herbalists is presented with the intention of identifying those species which are endangered, although the herbalists themselves do not yet perceive the seriousness of the situation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The conditions of the Southern Sudanese Women Migrants in Abu Siid Shanty Town,Omdurman, Sudan — A Case Study of Cultural Change     

Fouad N. Ibrahim Dr. 《GeoJournal》1990,20(3):249-258

The author analyzes the changing conditions to which S Sudanese women have been subjected after their forced migration the war-ridden South to Khartoum. There, too, they are suffering from hunger, homelessness, lack of a basic needs. Being obliged to house and work illegally these women find themselves considered criminals by both the State and many of the so-called Arabs. Serious identity change is involved in the process of adaptationof these rural people to the hostile urban environment.This paper contains preliminary results of a field study conducted by the author in April 1989 within the framework of the research programme Identity in Africa of the German Research Society under the coordination of Helmut Ruppert and the author. Both, as well as Abdel Hamid Bakhit and Ismail Al Fihail have participated in this research on the migration of the Southerners to Khartoum.  相似文献   

Testing the efficacy of voluntary urban greenhouse gas emissions inventories     

Fouad Khan  Benjamin K. Sovacool 《Climatic change》2016,139(2):141-154

  相似文献   

Pastoralists in transition — a case study from Lengijape,Maasai Steppe     

Barbara  Ibrahim Ibrahim  N. Fouad 《GeoJournal》1995,36(1):27-48

The change of the Maasai from pure pastoralists to agropastoralists has brought about serious problems for them. This paper tries to analyse this process of change and to throw some light on the resultant problems. First, it is being shown how the climate of the Maasai Steppe is too dry for a successful cultivation of maize by them, which has become their main food. Successive crop failures and high labour costs have rendered maize-growing a losing-business for the Maasai. Moreover, the State policy of granting certificates of occupancy in the Maasai land to outsiders allowing them to make large-mechanized farms, has alarmed the Maasai so much that many of them rushed back to their home areas to rescue their land from being grapped by other ethnic groups. Thus, they began to abandon their traditional grazing-movements, which are highly adapted to the ecological conditions of the Maasai Steppe. At the same time, the herds of the Maasai were decimated, because of the spread of animal diseases following the deterioration of the State veterinary service system. Added to this are the losses incurred through distress sales of cattle for buying maize for food, at a time at which the maize prices are increasing at a much higher rate than the prices of livestock. This dilemma of the Maasai and their indigenous coping mechanisms are being illustrated by the case of the people of Mokia at Namalulu, with special consideration of the role of women in solving these problems.  相似文献