Levantine basin and Cyprus arc : structural and sedimentary process along sub-marine plate boundaries

La convergence des plaques eurasienne et africaine s est réalisée, depuis le Crétacé, par une succession de subductions et de zones de pré-collision qui témoignent d un processus de fermeture de la Méditerranée. L arc de Chypre est le segment le plus oriental de ce système de convergence méditerranéen qui se complique par le mouvement vers l Ouest de la microplaque anatolienne. Ce mouvement génère en Méditerranée Orientale et particulièrement le long de l Arc de Chypre, un régime tectonique complexe. Au cours d une campagne de géophysique marine réalisée en 2003 (campagne BLAC, N/O Le Suroît), près de 20000 km2 ont été cartographiés aboutissant à une couverture quasi-complète du segment oriental de l arc de Chypre depuis les monts Hecataeus jusqu aux abords de la marge syrienne. Les données suivantes ont été acquises de façon simultanée et continue : bathymétrie multifaisceaux et imagerie acoustique grâce au sondeur multifaisceaux Simrad EM300, sismique réflexion 6-traces, sondeur de sédiments (CHIRP), gravimétrie et magnétisme. Ce travail fournit une analyse structurale et morphologique du segment le plus oriental de l arc de Chypre ainsi qu un examen détaillé des instabilités gravitaires sur la marge syrienne et les différentes activités halo/argilocinèse au sein des bassins avoisinants de l arc de Chypre.The convergence of Eurasian and African plates started since the Cretaceous by a succession of subduction and pre-collision zones that witness a closure process of the Mediterranean. The Cyprus Arc is the easternmost segment of this Mediterranean convergence system which got complicated with the westward extrusion of the Anatolian microplate. This movement generates in the Eastern Mediterranean and in particularly along the Cyprus Arc a complex tectonic regime. During the research cruise BLAC in 2003 onboard the R/V Le Suroît, 20.000 sq Km of seafloor has been mapped including the easternmost segment of Cyprus Arc and going from Hecataeus Seamount till the Syrian margins. The following data have been acquired continuously and in a simultaneous way: Multibeam bathymetry and backscatter imagery with the multibeam echousounder EM300, 6-traces seismic reflection, subbottom sediment echousounder (CHIRP), gravity and magnetic data. This manuscript gives structural and morphological analysis of the easternmost segment of the Cyprus Arc as well as a detailed study of gravity induced instabilities on the Syrian margin and the different mud and salt activities in the adjacent basins of the Cyprus Arc.PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

Étude biocénotique et qualité des eaux de quatre cours d'eau côtiers libanais Nahr Ibrahim, Nahr el Kalb, Nahr Antélias et Nahr Beyrouth (biologie et écologie de Capoeta damascina Günther 1868 (poisson, cyprinidae))

Quatre cours d'eau libanais ont fait l'objet d'une étude écologique basée sur des observations, des recherches et des mesures physico-chimiques et biologiques afin d'évaluer la qualité des eaux de ces hydrosystèmes continentaux. Les barrages sur Nahr Ibrahim n'ont pas d'effet notoire sur la qualité des eaux. Nahr el Kalb possède un régime d'écoulement temporaire dans son cours moyen. Les communautés zoologiques sont plus pauvres que celles du Nahr Ibrahim. Nahr Antélias est pollué sur tout son cours, les rejets d'eaux usées aggravant cette pollution. Le genre Physa caractérise ce cours d'eau. Dans le Nahr Beyrouth les indices biotiques possèdent des valeurs assez grandes. Le cours inférieur est un égout en basses eaux, avec des espèces faunistiques et floristiques caractéristiques des eaux polluées. Capoeta damascina, est un poisson phytophage, qui se nourri de diatomées (Navicula et Synedra) et de l'algue Rhizoclonium. L'étude du cycle sexuel de C. damascina montre l'apparition d'un dimorphisme sexuel, et un sex-ratio supérieur à 1.The ecology of 4 rivers in Lebanon, Nahr Ibrahim, Nar el Kalb, Nahr Antelias and Nahr Beirut has been studied based on systematic observations and on the study of physico-chemical and biological parameters in order to evaluate their ecological status and characterize any anthropological impacts. Dams on Nahr Ibrahim have no measurable effect on the ecosystem. Nahr el Kalb possesses a temporary flow in its middle section. The zoological communities appear to be poorer than that of Nahr Ibrahim. Nahr Antelias is polluted throughout mainly as a result of discharges from the village of Antelias. The river is characterized by the presence of the mollusca Physa. In Nahr Beirut, the biotic indices are high. The lower section of the river, transforms into a sewer in periods of low water flow as evidenced by fauna and flora characteristic of such waters. Capoeta damascina in these waters is a phytophagous fish and diatoms ( Navicula & Synedra) with the algae Rhizoclonium are its major dietary source. The fish shows sexual dimorphism with the sex ratio higher than 1.PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

Morphodynamique à multi-échelles du trait de côte (prisme sableux) du golfe du Lion depuis le dernier optimum climatique

La problématique du trait de côte revient constamment dans les problèmes environnementaux littoraux. Depuis 6000 ans, le trait de côte s est déplacé. Le golfe du Lion (mer Méditerranée) constitue un laboratoire naturel exceptionnel pour l étude de la migration du trait de côte en milieu microtidal, de par les présences de lagunes en arrière du cordon et de barres subtidales sur l avant-côte. Les lagunes sont des milieux où l enregistrement sédimentaire est bien préservé, permettant de reconstruire l évolution de la lagune et la construction de la barrière littorale. Le premier objectif de ce travail est de caractériser l évolution de la lagune de Thau et du lido de Sète à travers l étude du remplissage sédimentaire. Utilisant les techniques de sismique réflexion et de carottages sédimentaires, trois unités principales ont été décrites. Leur analyse et les datations obtenues ont permis de reconstruire les principales étapes de l édification de la lagune. Les littoraux présentant deux barres sédimentaires ont été largement observés en milieux méso- et macrotidaux. Leur étude en milieu microtidal étant moins fréquente, le système à deux barres festonnées de Leucate-Plage a donc été observé depuis 2000. Le second objectif de ce travail est de proposer un modèle conceptuel d évolution basé sur la morphodynamique de ce système, à partir de suivis géophysiques et hydrodynamiques. Ce modèle, basé sur différentes séquences évolutives observées, a nécessité la création de nouveaux états de plage incluables dans les classifications usuelles. Il met en évidence l importance de la hauteur significative et de l incidence de la houle dans les changements morphologiques des systèmes.Problems in coastal environments are often linked to the position of the shoreline, which has moved for 6000 years. Gulf of Lion (Mediterranean Sea) is an exceptional natural laboratory for morphodynamical studies of the shoreline in microtidal environment, using the existence of coastal lagoons behind the barrier island and subtidal sandbars on the shoreface.Lagoons are environments where the sedimentary infill is well preserved. The sedimentary record can be used for the paleo-reconstruction of the lagoon and of the sandy barrier. The first goal of this work is to characterize the evolution of Thau lagoon and Sète sandy barrier from the sedimentary infill. Using data of seismic reflexion and sedimentary cores, three mains units have been described. The main steps of the lagoon edification have been reconstructed using the analyses and the datation of the sedimentary samples.Coast showing systems with two sandbars have been observed in meso- and macrotidal environments. Their study in microtidal environment is less abundant, that s why the system of Leucate Beach has been studied since 2000. The second goal of this work is to propose a conceptual modeling based on the morphodynamics of the system, from geophysical and hydrodynamical data. This model is based on morphodynamic observed sequences, it is necessary to create two beach states which can be included in the usual classification. It shows the role of the significant wave height and the incidence of the waves in the morphodynamics of the system.PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

La ride sédimentaire pyrénéo-languedocienne (étude multi-échelle d'une accumulation sédimentaire marine profonde dans le Golfe du Lion (méditerranée nord-occidentale))

Sous l'effet des facteurs tectoniques et eustatiques, les sédiments marins, situés sur les plateaux continentaux, transitent vers la pente et les plaines abyssales où ils alimentent des édifices plus ou moins vastes. Dans le Golfe du Lion, la Ride Sédimentaire Pyrénéo-Languedocienne, située au pied de la pente catalano-languedocienne, est une levée sédimentaire hypertrophiée d'age quaternaire. Elle forme la levée sud de la vallée du Cap Creus et la levée ouest de la vallée de Sète et se caractérise par la présence de dunes principalement d'origine hydrosédimentaire (sediment waves). Les études sismiques, morphologiques et sédimentologiques menées sur cet édifice constituent une étude multi-échelle permettant d'appréhender son origine, et les facteurs responsables de son édification durant le Plioquaternaire (tectonique salifère, écoulements gravitaires, déformation plastique), ces observations donnant un nouvel éclairage sur les processus régionaux de sédimentation marine profonde.PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

Morphodynamique à l'échelle régionale d'une avant-côte microtidale à barres sédimentaires (le cas du Languedoc-Roussillon à l'aide la technologie LiDAR)

PERPIGNAN-BU Sciences (661362101) / SudocSudocFranceF

Monitoring Water Quality in the Coastal Area of Tripoli (Lebanon) Using High-Resolution Satellite Data

Water quality in the coastal area of Tripoli (Lebanon) was assessed using Landsat 7 ETM+ data, to provide a first baseline for coastal resources management. The data were geometrically rectified to a standard geographical grid and brightness values were converted to reflectance through radiometric correction. Sea-truth data, collected in the field within 6 hours before/after the time of the satellite overpass, were used to derive empirical algorithms for chlorophyll-a concentration, Secchi disk depth and turbidity. Then, maps of the distribution of the selected water quality parameters were generated for the entire area of interest, and compared with analogous results obtained from SeaWiFS data. The maps indicate that the Tripoli coastal area is exposed to moderate eutrophic conditions, along most of its shoreline (in particular along the northern stretch), in correspondence with fluvial and wastewater runoff sources. The Landsat 7 ETM+ data proved useful for the intended application, and will be used to start a national database on water quality in the Lebanese coastal environment.JRC.H.3-Global environement monitorin

La branche orientale de l'arc de Chypre. Morphostructure d'une frontière de plaques d'après les résultats de la campagne BLAC (2003)

International audienceThe eastern bend of the Cyprus Arc, at the transition between the submerged Mediterranean subduction and the onshore fault zones that underline the Eurasian, African and Arabic plates boundaries is a submarine feature undergoing a complex tectonic deformation. The BLAC marine geophysical survey helps to better assess the type of the deformation that affects the Messinian to Quaternary sediments along this plate boundary. The deformation, focussed between two tectonic corridors, displays compressive and transpressive features in the central part, becoming thrusting when moving westward in connection with the Cyprus accretionnary wedge. The northeastern end of this submarine range connects with the Latakia Ridge, which is, together with its continental extension, under a tensional tectonic regime. To cite this article: J. Benkhelil et al., C. R. Geoscience 337 (2005)

Clasts from mud volcanoes from the eastern Mediterranean

In the eastern Mediterranean, numerous argilo-kinetic manifestations, commonly named 'mud volcanoes', have been identified and studied in some detail during the last twenty years using several techniques. The Medinaut survey (December 1998) has provided new insights into this phenomenon through twenty deep dives performed with the submersible Nautile within two areas particularly active in terms of mud expulsions: the central Mediterranean ridge south of Crete, and the Anaximander mountains area, south of Turkey. The morphology, petrography, microstructure and biostratigraphy of different clasts sampled in the two areas helped to better understand the mud volcano formation and subsequent evolution. Paleoenvironmental conditions, ranging from deep marine deposition in distal deep-sea-fan environment during the Miocene (Mediterranean ridge) to continental margin conditions (Anaximander mountains), have been evaluated for the composition and age of the various rock types. Macroscopic and microscopic structural observations have revealed a close control of clast shapes by sets of early microfractures (calcite veins, joints) created before the clast expulsion to the seabed surface. Surface features, such as erosion marks, alteration aureoles or calcitic coatings, have also been described on most samples. Finally, erosion traces, alteration aureoles and calcitic coating observed for the first time are interpreted as the result of a complex cold seep context related to mud expulsion and associated fluid venting. © 2001 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS

L’environnement géologique de la Caune de l’Arago, site préhistorique de l’homme de Tautavel

Il est fait souvent allusion à l’attractivité quel la Caune de l’Arago a pu exercer sur les premiers hommes préhistoriques du Pléistocène qui sont venus y trouver refuge. Cette grotte est spacieuse, située sur le flanc méridional de la colline de l’Arague, elle se trouvait ainsi protégée des vents du nord pendant les périodes venteuses les plus agressives et pouvait bénéficier d’un maximum d’ensoleillement. Perchée à mi-hauteur d’une forte pente calcaire, elle constituait aussi un observatoir..

Palynofacies analysis of sediments from the Cote d\u27Ivoire-Ghana Transform Margin: Preliminary correlation with some regional events in the Equatorial Atlantic

Analyses of the palynofacies and sporomorph thermal alteration indices (TAI) of sediments from Ocean Drilling Program (ODP) Sites 959 to 962 in the Cote d\u27Ivoire-Ghana Transform Margin, West Africa were undertaken to (1) determine the source and depositional conditions of the organic matter in the sediments, (2) refine a paleobathymetric curve derived from other data for Site 959, which drilled the most continuous sedimentary sequence from Pleistocene to Albian and (3) interpret the paleothermal history of the area. Twelve types of dispersed organic matter were identified: amorphous organic matter (AOM), marine palynomorphs, algae, resins, black debris, yellow-brown fragments, black-brown fragments, cuticles, plant tissue, wood, sporomorphs and fungi. The relative abundances of these organic matter components at each site were analyzed using cluster analysis, resulting in the identification of seven palynofacies assemblages at Site 959, five each at sites 960 and 961, and four at Site 962. Amorphous organic matter (which is chiefly marine derived), black debris and wood have played the most significant role in defining palynofacies assemblages. The palynofacies assemblages show some correlation with lithologic units, sediment sources and depositional environments. Previous palynofacies studies in passive margins have demonstrated that changes in the ratio of AOM to terrestrial organic matter are related primarily to proximal-distal positions of depositional environments relative to the shoreline. However, this assumption does not always hold true for a transform margin where tectonic factors play an important role in the organic matter distribution, at least in the early stages of evolution. Lithofacies, CCD paleodepths for the North Atlantic, trace fossil association, benthic foraminifera and palynofacies data were the criteria used for reconstructing a paleobathymetric curve for Site 959. A cyclicity in the organic matter distribution of the Upper Miocene to Lower Pliocene pelagic sediments could be related to fluctuations in productivity of biosiliceous and calcareous organisms, and sedimentation rates. A drastic increase in the amount of AOM and a decrease in black debris and wood in the carbonate and elastic rocks (Lithologic Unit IV) overlying the tectonized Albian sediments (Lithologic Unit V) at Sites 959 and 960 coincide with the presence of an unconformity. Qualitative color analysis of palynomorphs was undertaken for all sites, although the main focus was on Site 959 where detailed organic geochemical data were available. At Site 959, TAI values indicate an immature stage of organic maturation (\u3c21 down to the black claystones of Lithologic Unit III at about 918.47 mbsf. Below this, samples show an increase with depth to a moderately mature stage (\u3e2 except for the claystone samples between 1012.52 and 1036.5 mbsf, and one limestone sample at 1043.4 mbsf), reaching peak levels of 2.58 to 3.0 in the tectonized Albian sediments below the unconformity. These TAI values show a positive correlation with the T(max) values derived from Rock-Eval pyrolysis data. The highest values recorded in the basal tectonized units at all the sites (Sites 960 962 have mean values between 2.25 and 3.13) may be related to high heat flow during the intracontinental to syntransform basin stage in the region