The charophytes-rich Barremian-Albian record in Jebel Ksaïra (Central Tunisia)

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Implication for the use of benthic foraminifera as bio-indicators of pollution: The case study of the Northern coast of Sfax (South eastern Tunisia)

peer reviewedThe use of foraminifers as bioindicators of pollution in coastal and paralic environments has undergone a very fast development. Among various criteria, morphological anomalies are sometimes considered as pollution indicators. This paper presents a synthesis of the studies correlating foraminiferal assemblages and environmental concerns. Sediment cores retrieved along the northern coast of Sfax (Tunisia) are used to monitor the response of benthic foraminifera to modern pollution and environmental stress. Sediment samples were separated immediately after collection for benthic foraminifera analysis. Binocular microscope and the Scanning Electron Microscope (SEM) were carried out to identify the most significant, normal or deformed, specimens. All observations confirmed that foraminifera may be used as indicators of pollution after deconvoluting from natural impacts. The most sensitive foraminifera identified in the study area are Ammonia tepida, Ammonia beccarii, Elphidium crispum, Peneroplis pertususles Miliolidae, Peneroplis pertusus et Rosalina sp and Peneroplis planatus. The morphological study of benthic foraminifera from surface sediments attests for the pollution of the actual coast. This pollution is recorded in the benthic foraminifera tests mainly as shell deformations, chambers or streaks or abnormal colors

Holocene evolution of the coastal system of Sfax (SE Tunisia)

This study aims to identify the depositional environments along the Tunisian coastal system and to follow their evolution over the Holocene. The material consists in three marine sediment cores retrieved at 3 meter depth from the Northern coastal system of Sfax («Société d'Étude et d'Aménagement des Côtes Nord de la Ville de Sfax", site TAPARURA). The identification of the different depositional paleoenvironments was mainly based on field campaigns and laboratory mineralogical and sedimentological analyses of sediments. The vertical succession analysis of depositional facies allows to identify 2 main environments. First a fluviatile depositional environment (coastal plain) is characterized by fluviatile channels facies and inundation plains at the bottom of the cores. Second, at the top of the cores, we observed a marine sandy sedimentation with numerous bioclasts of gasteropods, lamellibranches and algae. This facies evolution is consistent with a relative sea level rise, responsible for the flooding of the fluviatile system at the level of the coastal plain. The main factor controlling the facies evolution and the sediment thickness variation is the local sea-floor morphology. The Holocene seabed is mainly inherited from the last glacial maximum morphology. Resulting from an important fluviatile digging that occurred, the relative sea-level fluctuations, the hydro-isostatic rebound and the climate

Reconstructing the Holocene depositional environments along the northern coast of Sfax (Tunisia): mineralogical and sedimentological approaches

This study aims to reconstruct the Holocene to modern depositional environments and the evolution over the main controls of the sedimentation along the northern coast of Sfax (Tunisia) using three sediment cores retrieved at 30 meters water depth by SEACNVS (Société d'Étude et d'Aménagement des Côtes Nord de la Ville de Sfax). The identification of different types of depositional environments was mainly based on field work,mineralogical and sedimentological analyses of core sediments. Mineralogical analysis by X-ray diffraction have been done on bulk powder and on oriented aggregate of the clay < 2 microns fraction,particle size distribution,magnetic susceptibility was measured on opened cores with a Bartington MS2Epoint sensor and Loss-On-Ignition (LOI) was measured after 24h at 105°C (water content, density), after 4h at 550°C (organic matter content) and after 2h at 950°C (inorganic carbonate).The mineralogical composition is made by clay minerals, quartz, calcite, gypsum and K-feldspar.The mineralogy of <2μm clay fraction show a mixture of kaolinite,illite, smectite and palygorskite. As harp change in the magnetic susceptibility profiles records the transition from a marine to a continental depositional environment. The marine domain is characterized by lower magnetic susceptibility values and coarser sedimentary grain than the continental domain. The vertical succession of depositional facies is made by two contrasted environments: a fluvial depositional environment (coastal plain) marked by channels and inundation plains at the in the lower section of all cores; a littoral marine environment characterized by fossil sand depositions in the upper section. The sand is rich in gastropods, lamellibranches, algæ and benthic fauna (Ammonia tepida, Ammonia beccarii, Elphidium crispum, Peneroplis pertususles Miliolidae, Peneroplis pertusus , Rosalina sp and Peneroplis planatus). This facies evolution indicates a relative sea-level rise which flooded the fluvial system at the coastal plain during the late Holocene. Results allowed the reconstruction of the Holocene shoreline variations along the northern coast of Sfax and complete the established records of sea-level fluctuations in southeast Tunisia during the last 10 000 years

Metals anomalies in foraminiferal shells as indicators for industrial pollution: a case study from the Mediterranean coast of Tunisia

In recent years we have been witnessing a considerable growth of industrial facilities along coastal areas. Some of these have major economical and national importance yet their operation can introduce a wide range of chemicals that might contaminate the coastal area and impact local ecosystems and our health. Among some of these harmful chemicals are metals that are introduced to the coastal environment by some of these facilities. Here we present a novel approach for monitoring low-level industrial pollution in coastal environments based on anomalies in metal concentration within foraminiferal shells. The comparative study between the faunal content and the heavy metalsenrichments in each sample displayed positive character indicating the worsening of the environmental conditions.Sediment cores retrieved along the northern coast of Sfax (Southeastern Tunisia) are used to monitor the response of benthic foraminifera to modern pollution and environmental stress.Binocular microscope and the Scanning Electron Microscope (SEM) were carried out to identify the most significant, normal or deformed, specimens. All observations confirmed that foraminifera may be used as indicators of pollution after deconvoluting from natural impacts. The most sensitive foraminifera identified in the study area are Ammonia tepida, Ammonia beccarii, Elphidium crispum, Peneroplis pertususles Miliolidae, Peneroplis pertusus, Rosalina sp and Peneroplis planatus. The morphological study of benthic foraminifera from surface sediments attests for the pollution of the actual coast. This pollution is recorded in the benthic foraminifera tests mainly as shell deformations, chambers or streaks

Sedimentology and carbonatogenesis of the Upper Campanian limestones in Jebel Berda (south central Tunisia)

peer reviewedThe Berda Formation corresponds to an inner-shelf stratigraphic equivalent of the Campanian-Maastrichtian outer-shelf Abiod Formation of Tunisia. The present work aims to carry out a sedimentological study of the lower unit (Upper Campanian) of Berda Formation limestones in order to interpret the limestone depositional environment and the origin of the associated micrite particles. This work is based on the study of a geological section surveyed in the Jebel Berda, typic locality, completed by microscopic observation of thin sections that allowed us identifying different carbonate facies and interpreting their depositional environments. The micrite particles have been examined with the SEM. The mineralogical and geochemical proportions and the magnetic susceptibility of the Berda Formation limestone, have been evaluated using respectively XRD, Atomic Absorption Techniques and KLY-3 Kappabridge susceptometer. The studied succession of Berda Formation includes fve carbonate facies that developed within different depositional environments (1) calcisphere-rich bioclastic mudstone-wackesto e within a circalittoral environment, (2) echinoderm-rich bioclastic wackestone-packstone within a shallow-marine environment (3) bioclastic rudstone within an open-marine environment, (4) peloidrich bioclastic grainstone within high energy littoral shallow-water marine environment and (5) bioclastic dolomicrite-dolomicrosparite within a continental to marine transition environment. The studied limestones are composed of two kinds of micrite particles, (1) irregularly shaped particles resulting from fossils and micro-fossils desintegration and (2) regularly shaped polyhedral particles resulting from inorganic chemical precipitation. The carbonate facies are arranged into shallowing-up parasequences. The sedimentary facies variation and carbonate accumulation are controlled by eustatic sea-level fluctuation. In this way the biodetrital micrite occurred mainly during the transgressive intervals whereas the inorganic chemical micrite is related to the regressive intervals

Stratigraphie des formations Hameima et Fahdene de la région de Tadjérouine, Tunisie du Nord

International audienceIn the Tadjerouine area (NW of Central Tunisia) the incipient Albian transgression is materialised by alternating marls, limestones and sandstones (Hameima Fm) that overly massive platform carbonates (Serdj Fm). The ongoing transgression then gives way to a thick series of marls and shales with subordinate carbonate beds (Fahdene Fm). A detailed study of the Hameima Fm, previously ascribed to the Late Aptian, shows that it can be subdivided into three members, all of earliest Albian age (Leymeriella tardefurcata Zone), and its top is slightly diachronous. A similar study of the lower Shales of the Fahdene Fm demonstrates that they belong to the Leymeriella tardefurcata Zone and to the lower part of the Douvilleiceras mammillatum superzone. The overlying Allam limestones, formerly considered Middle Albian in age, are mainly of late Early Albian age (upper part of Douvilleiceras mammillatum Superzone and Lyelliceras pseudolyelli Zone), although an extension into the lower Middle Albian cannot be ruled out. The Allam limestones are abruptly overlain by a diachronous series of Late Albian shales (Middle Shales of Fahdene Fm), thus evidencing a stratigraphic hiatus of most of the Middle Albian and part of the early Late Albian. Our new data will lead to revise the range of some Aptian/Albian orbitolinids and Albian planktic foraminifera.Dans la région de Tadjérouine (NW de la Tunisie centrale), le début de la transgression albienne est marquée par une alternance de marnes, calcaires et grès (Fm Hameima) qui surmonte des calcaires massifs de plateforme (Fm Serdj). La suite de la transgression donne lieu au dépôt d'une épaisse série de marnes et argiles avec quelques bancs calcaires (Fm Fahdene). L'étude détaillée de la Fm Hameima, jusqu'ici attribuée à l'Aptien supérieur, montre qu'elle peut être divisée en trois membres, tous d'âge Albien basal (zone à Leymeriella tardefurcata), et son sommet est légèrement diachrone. L'étude similaire des Argiles inférieures de la Fm Fahdene montre qu'elles appartiennent à la même zone à Leymeriella tardefurcata et à la partie inférieure de la Superzone à Douvilleiceras mammillatum. Au-dessus, les Calcaires Allam, auparavant considérés d'âge Albien moyen, datent principalement de la fin de l'Albien inférieur (partie supérieur de la superzone à Douvilleiceras mammillatum et zone à Lyelliceras pseudolyelli), même si le sommet pourrait atteindre l'Albien moyen. Les Calcaires Allam sont surmontés par une série diachrone d'argiles de l'Albien supérieur (Argiles moyennes de la Fm Fahdene), montrant ainsi un hiatus stratigraphique incluant la plus grande partie de l'Albien moyen et la base de l'Albien supérieur. Ces nouvelles données pourraient amener à réviser la distribution stratigraphique de certaines espèces d'orbitolinidés de l'Aptien-Albien et de foraminifères de l'Albien

Stratigraphie des formations Hameima et Fahdene de la région de Tadjérouine, Tunisie du Nord

International audienceIn the Tadjerouine area (NW of Central Tunisia) the incipient Albian transgression is materialised by alternating marls, limestones and sandstones (Hameima Fm) that overly massive platform carbonates (Serdj Fm). The ongoing transgression then gives way to a thick series of marls and shales with subordinate carbonate beds (Fahdene Fm). A detailed study of the Hameima Fm, previously ascribed to the Late Aptian, shows that it can be subdivided into three members, all of earliest Albian age (Leymeriella tardefurcata Zone), and its top is slightly diachronous. A similar study of the lower Shales of the Fahdene Fm demonstrates that they belong to the Leymeriella tardefurcata Zone and to the lower part of the Douvilleiceras mammillatum superzone. The overlying Allam limestones, formerly considered Middle Albian in age, are mainly of late Early Albian age (upper part of Douvilleiceras mammillatum Superzone and Lyelliceras pseudolyelli Zone), although an extension into the lower Middle Albian cannot be ruled out. The Allam limestones are abruptly overlain by a diachronous series of Late Albian shales (Middle Shales of Fahdene Fm), thus evidencing a stratigraphic hiatus of most of the Middle Albian and part of the early Late Albian. Our new data will lead to revise the range of some Aptian/Albian orbitolinids and Albian planktic foraminifera.Dans la région de Tadjérouine (NW de la Tunisie centrale), le début de la transgression albienne est marquée par une alternance de marnes, calcaires et grès (Fm Hameima) qui surmonte des calcaires massifs de plateforme (Fm Serdj). La suite de la transgression donne lieu au dépôt d'une épaisse série de marnes et argiles avec quelques bancs calcaires (Fm Fahdene). L'étude détaillée de la Fm Hameima, jusqu'ici attribuée à l'Aptien supérieur, montre qu'elle peut être divisée en trois membres, tous d'âge Albien basal (zone à Leymeriella tardefurcata), et son sommet est légèrement diachrone. L'étude similaire des Argiles inférieures de la Fm Fahdene montre qu'elles appartiennent à la même zone à Leymeriella tardefurcata et à la partie inférieure de la Superzone à Douvilleiceras mammillatum. Au-dessus, les Calcaires Allam, auparavant considérés d'âge Albien moyen, datent principalement de la fin de l'Albien inférieur (partie supérieur de la superzone à Douvilleiceras mammillatum et zone à Lyelliceras pseudolyelli), même si le sommet pourrait atteindre l'Albien moyen. Les Calcaires Allam sont surmontés par une série diachrone d'argiles de l'Albien supérieur (Argiles moyennes de la Fm Fahdene), montrant ainsi un hiatus stratigraphique incluant la plus grande partie de l'Albien moyen et la base de l'Albien supérieur. Ces nouvelles données pourraient amener à réviser la distribution stratigraphique de certaines espèces d'orbitolinidés de l'Aptien-Albien et de foraminifères de l'Albien

Sedimentary and microfaunal evolution in the Quaternary deposits in El Akarit river mouth (Gulf of Gabes, Tunisia): Paleo-environments and extreme events

International audienceThe quantitative study of ostracod and benthic foraminifera assemblages coupled with sedimentary facies, of the AK1 core (6 m-long) retrieved from the El Akarit prodelta (Gulf of Gabes, SE Tunisia) at an elevation of 0 m, enabled us to better understand the dynamics of depositional environments and to identify different stages of the Akarit river mouth evolution. Two major steps were identified: the first (>40,000 yr BP) possibly coincides with the Marine Isotope Stage 5e, onlapping continental Pleistocene deposits. It allowed the settlement of an open lagoon rich in marine microfauna that has become progressively more confined. The second one, late Holocene in age (last 3000 yr BP) is the succession of three extreme events episodes, characterized by very high-energy hydrodynamics and possibly linked to the occurrence of major storms and/or floods

Biostratigraphie et sédimentologie des séquences du Crétacé supérieur du Jebel Mrhila - Tunisie centrale

The Upper Cretaceous series of Jebel Mrhila correspond to five major sedimentary sequences. The stratigraphie revision of these sequences, based on ammonites, echinoïds, planktonic and benthonic foraminifera and ostracods has led to attribute them to Vraconian, Cenomanian, Early to Middle Turonian, Middle to Upper Turo-nian and Late Santonian to Campanian respectively. These deeping-shallowing sequences have been deposited on medium to outer shelf under the influence of tectonic and eustatic factors.L'analyse séquentielle des séries argilo-carbonatées du Crétacé supérieur du Jebel Mrhila a conduit à définir cinq séquences sédi-mentaires majeures. La révision stratigraphique de ces dernières, basée sur les ammonites, échinides, foraminifères planctoniques et benthiques et ostracodes, a permis de les attribuer respectivement au Vraconien, au Cénomanien, au Turonien inférieur à moyen, au Turonien moyen-supérieur et au Santonien terminal-Campanien. Ces séquences, bathycroissantes puis bathydécroissantes ont été déposées dans des milieux marins de type plate-forme moyenne à externe, sous l'influence de facteurs tectoniques et eustatiques.Touir Jamel, Ben Haj Ali N., Donze Pierre, Maamouri A. L., Memmi Lucia, M'Rabet Ali, Razgallah-Gargouri Saloua, Zaghbib-Turki Dalila. Biostratigraphie et sédimentologie des séquences du Crétacé supérieur du Jebel Mrhila - Tunisie centrale. In: Géologie Méditerranéenne. Tome 16, numéro 1, 1989. pp. 55-66