Energetic Charged Particles Above Thunderclouds     

Martin Füllekrug  Declan Diver  Jean-Louis Pinçon  Alan D. R. Phelps  Anne Bourdon  Christiane Helling  Elisabeth Blanc  Farideh Honary  R. Giles Harrison  Jean-André Sauvaud  Jean-Baptiste Renard  Mark Lester  Michael Rycroft  Mike Kosch  Richard B. Horne  Serge Soula  Stéphane Gaffet 《Surveys in Geophysics》2013,34(1):1-41

The French government has committed to launch the satellite TARANIS to study transient coupling processes between the Earth’s atmosphere and near-Earth space. The prime objective of TARANIS is to detect energetic charged particles and hard radiation emanating from thunderclouds. The British Nobel prize winner C.T.R. Wilson predicted lightning discharges from the top of thunderclouds into space almost a century ago. However, new experiments have only recently confirmed energetic discharge processes which transfer energy from the top of thunderclouds into the upper atmosphere and near-Earth space; they are now denoted as transient luminous events, terrestrial gamma-ray flashes and relativistic electron beams. This meeting report builds on the current state of scientific knowledge on the physics of plasmas in the laboratory and naturally occurring plasmas in the Earth’s atmosphere to propose areas of future research. The report specifically reflects presentations delivered by the members of a novel Franco-British collaboration during a meeting at the French Embassy in London held in November 2011. The scientific subjects of the report tackle ionization processes leading to electrical discharge processes, observations of transient luminous events, electromagnetic emissions, energetic charged particles and their impact on the Earth’s atmosphere. The importance of future research in this area for science and society, and towards spacecraft protection, is emphasized.  相似文献   

Early Permian extensional shearing of an Ordovician granite: The Saint-Eutrope “C/S-like” orthogneiss (Montagne Noire,French Massif Central)     

Pavel Pitra  Marc Poujol  Jean Van Den Driessche  Jean-Charles Poilvet  Jean-Louis Paquette 《Comptes Rendus Geoscience》2012,344(8):377-384

Dating the magmatic events in the Montagne Noire gneiss dome is a key point to arbitrate between the different interpretations of the Late Carboniferous–Early Permian tectonics in this southern part of the Variscan belt. The Saint-Eutrope orthogneiss crops out along the northern flank of the dome. We show that the protolith of this orthogneiss is an Ordovician granite dated at 455 ± 2 Ma (LA-ICP-MS U-Pb dating on zircon). This age is identical to that previously obtained on the augen orthogneiss of the southern flank, strongly suggesting that both orthogneiss occurrences have the same Ordovician protolith. The Saint-Eutrope orthogneiss experienced intense shearing along the Espinouse extensional detachment at ca. 295 Ma (LA-ICP-MS U-Pb-Th on monazite), an age close to that determined previously on mica by the ³⁹Ar-⁴⁰Ar method and contemporaneous with the emplacement age of the syntectonic Montalet granite farther to the west. This normal sense shearing reworked previous fabrics related to Variscan thrusting that can be still observed in the augen orthogneiss of the southern flank, and is responsible for the spectacular “C/S-like” pattern of the Saint-Eutrope orthogneiss. This work also shows that care is needed when dealing with C/S-type structures, since they can develop not only in syntectonic intrusions, but also in orthogneisses affected by an intense secondary deformation, at decreasing temperature.  相似文献   

The last glacial-interglacial transition and dinoflagellate cysts in the western Mediterranean Sea     

Imene Rouis-Zargouni  Jean-Louis Turon  Laurent Londeix  Néjib Kallel  Latifa Essallami 《Comptes Rendus Geoscience》2012,344(2):99-109

Using the analysis of dinoflagellate cysts in three deep-sea sediments cores situated in the Sicilian-Tunisian Strait, in the Gulf of Lions and in the Alboran Sea, we reconstruct the paleoenvironmental changes that took place during the last glacial-interglacial transition in the western Mediterranean Sea. The development of the warm microflora Impagidinium aculeatum and especially Spiniferites mirabilis appears to be an important proxy for recognizing warm periods as the Bölling/Alleröd and the Early Holocene. Bitectatodinium tepikiense, Spiniferites elongatus and Nematosphaeropsis labyrinthus mark the end of the Heinrich event 1 and the Younger Dryas. This cold microfloral association confirms the drastic climate changes in the western Mediterranean Sea synchronous to the dry and cold climate which occurred in the South European margin. The dinocyst N. labyrinthus shows high percentages in all studied regions during the Younger Dryas. Its distribution reveals a significant increase from the South to the North of this basin during this cold brief event. Thus, we note that this species can be considered as a new eco-stratigraphical tracer of the Younger Dryas in the western Mediterranean Sea.  相似文献   

Comparison and relative quality assessment of the GLC2000, GLOBCOVER,MODIS and ECOCLIMAP land cover data sets at the African continental scale     

Armel Thibaut Kaptué Tchuenté  Jean-Louis Roujean  Steven M. De Jong 《International Journal of Applied Earth Observation and Geoinformation》2011

Land cover dynamics at the African continental scale is of great importance for global change studies. Actually, four satellite-derived land cover maps of Africa now available, e.g. ECOCLIMAP, GLC2000, MODIS and GLOBCOVER, are based on images acquired in the 2000s. This study aims at stressing the compliances and the discrepancies between these four land cover classifications systems. Each of them used different mapping initiatives and relies on different mapping standards, which supports the present investigation. In order to do a relative comparison of the four maps, a preamble was to reconcile their thematic legends into more aggregated categories after a projection into the same spatial resolution. Results show that the agreement between the four land cover products is between 56 and 69%. While all these land cover datasets show a reasonable agreement in terms of surface types and spatial distribution patterns, mapping of heterogeneous landscapes in the four products is not very successful. Land cover products based on remote sensing imagery can indeed significantly be improved by using smarter algorithms, better timing of image acquisition, improved class definitions. Either will help to improve the accuracy of future land cover maps at the African continental scale. Data producers may use the areas of spatial agreement for training area selection while users might need to verify the information in the areas of disagreement using additional data sources.  相似文献   

Sorption-desorption kinetics and toxic cell concentration in marine phytoplankton microalgae exposed to Linear Alkylbenzene Sulfonate     

Renaud F  Oberhänsli F  Teyssié JL  Miramand P  Temara A  Warnau M 《Marine pollution bulletin》2011,62(5):942-947

Linear Alkylbenzene Sulfonates (LAS) are ubiquitous surfactants. Traces can be found in coastal environments. Sorption and toxicity of C₁₂-LAS congeners were studied in controlled conditions (2-3500 μg C₁₂LAS/L) in five marine phytoplanktonic species, using standardized methods. IC₅₀ values ranged from 0.5 to 2 mg LAS/L. Sorption of ¹⁴C₁₂-6 LAS isomer was measured at environmentally relevant trace levels (4 μg/L) using liquid scintillation counting. Steady-state sorption on algae was reached within 5 h in the order dinoflagellate > diatoms > green algae. The sorption data, fitted a L-type Freundlich isotherm, indicating saturation. Desorption was rapid but a low LAS fraction was still sorbed after 24 h. Toxic cell concentration was 0.38 ± 0.09 mg/g for the studied species. LAS toxicity results from sorption on biological membranes leading to non-specific disturbance of algal growth. Results indicate that LAS concentrations in coastal environments do not represent a risk for these organisms.  相似文献   

Experimental abiotic alteration of igneous and manufactured glasses     

Martin R. Fisk  Jean-Louis Crovisier  José Honnorez 《Comptes Rendus Geoscience》2013,345(4):176-184

Pits in ocean basalt glass are often attributed to the activity of microorganisms, however, neither the mechanism of formation of pits in glass nor the involvement of microorganisms have been confirmed by experimentation. Experimental abiotic corrosion of basalt glass with 1% hydrofluoric acid (HF), a proxy for more slowly acting organic acids, produces pits that are similar in size, shape, and distribution to pits found in basalt glass collected from the ocean floor and basalt glass incubated with microorganisms. This pit formation by HF etching was demonstrated by comparing secondary electron images taken before and after the acid treatment. The formation of pits by abiotic corrosion of basalt glass is an alternate hypothesis for the origin of these features, and the interpretation of these features as biomarkers may require a resolution of these alternative hypotheses.  相似文献   

Intra-oceanic settings of the western Mexico Late Jurassic-Early Cretaceous arc sequences. Implications for the Pacific-Tethys geodynamic relationships during the Cretaceous     

Marc Tardy  Henriette Lapierre  Jean-Louis Bourdier  Christian Couloni  R. Juventino Martinezr  H. Enrique Ortiz 《Geodinamica Acta》2013,26(3):174-185

Abstract

The Guerrero suspect terrane composed of Late Jurassic-Early Cretaceous sequences, extends from Baja California up to Acapulco and is considered to be coeval with the Late Mesozoic igneous and sedimentary arc sequences of the Greater Antilles, Venezuela and Western Cordillera of Colombia. New geological, petrological and geochemical data from central and southern Mexico, led us to propose a new model for the building of the Alisitos-Teloloapan arc. This arc, partly built on the Pacific oceanic lithosphere and partly on continental fragments, could be related to the subduction of an oceanic basin - the Arperos basin - under the Paleo-Pacific plate. This subduction was dipping southwest.

At the beginning of the magmatic activity of the oceanic segment of this arc, depleted tholeiitic basalts were emitted in a submarine environnement below the CCD. While subduction was going on, the arc magmas evolved from LREE depleted tholeiites to slightly LREE enriched tholeiites and then, to calc-alkaline basalts and andesites enriched in LREE and HFSE. Concurrently, the arc sedimentary environment changed from deep oceanic to neritic with the deposition of Aptian-Albian reefal limestones, at the end of the arc building. In the continent-based segment, the arc magmas are exclusively differentiated calc-alkaline suites depleted in HREE and Y, formed of predominantly siliceous lavas and pyroclastic rocks, emitted in a sub-aerial or shallow marine environment.

Thus, taking into account this above mentioned model, the Cretaceous volcanic series, accreted to the margins of cratonal America, in Colombia, Venezuela, Greater Antilles and Mexico, could be related to the same west-south-west dipping subduction of oceanic basins, fringing the North and South American continental cratons and connected directly with the inter-American Tethys. While the subduction was proceeding, this magmatic arc drifted towards the North and South American cratons and finally, collided with the continental margins at different periods during the Cretaceous.  相似文献   

Le magmatisme basique calcoalcalin d'âge dévono-dinantien du nord du Massif Central,témoin d'une marge active hercynienne: arguments géochimiques et isotopiques Sr/Nd     

Christian Pin  Jean-Louis Paquette 《Geodinamica Acta》2013,26(1):63-77

Abstract

Samples of volcanic rocks from the main outcrops of Devono-Dinantian series in northern Massif-Central have been studied for Sr and Nd isotopes and immobile incompatible trace elements. In addition, two intrusive bodies of dioritic composition have been dated at 365 ± 3 Ma (Aydat) and 360 ± 1 Ma (Beaumont-Huriel), using the U/Pb zircon method. Together with geochemical data, these ages show that all the studied rocks belong to the same igneous episode. Based on trace element and radiogenic isotopes (⁸⁷Sr/⁸⁶Sr_i from 0,7041 to 0,7057; εNd_i from +1.5 to +5.0), the Late Devonian and Early Carboniferous igneous rocks bear distinct similarities with magmas produced in modern active margin settings. Combined with independent evidence for the occurrence of Devonian oceanic lithosphere in the northern branch of the Variscides, these geochemical affinities suggest that southward subduction of oceanic crust prevailed during the Late Devonian in northern Massif-Central. As a corollary, it appears that true continent-continent collision did not occur before Early Carboniferous times. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.  相似文献   

Coupes équilibrées à travers le massif subalpin de la Chartreuse     

Jean-Louis Mugnier  Réjane Arpin  François Thouvenot 《Geodinamica Acta》2013,26(2):125-137

Résumé

Pour étudier la tectonique des chaînes subalpines du Nord, et proposer un modèle cinématique régional, nous avons utilisé les résultats d’une expérience géophysique réalisée en 1985, et les observations géologiques de surface publiées à ce jour. Ces données ont été analysées de manière à préciser le style tectonique, le positionnement des failles par rapport aux horizons stratigraphiques et le schéma de branchement des failles. La construction simultanée d’une coupe interprétative, d’une coupe restaurée et d’une carte de branchement des failles a permis d’estimer l’amplitude du raccourcissement par la méthode des coupes équilibrées. Au niveau du Nord de la Chartreuse, la valeur minimale du raccourcissement global est de 14 km, 4 km étant associés au système chevauchant du Jura et 10 km à celui du massif des Bornes et des Bauges. Compte tenu des imprécisions existant sur les données utilisées, trois modèles cinématiques, qui correspondent à une plage de raccourcissement comprise entre 14 et 25 km, sont proposés.  相似文献   

Seasonal changes in zooplanktonic alkaline phosphatase activity in Toulon Bay (France): the role of Cypris larvae     

Jean N  Bogé G  Jamet JL  Richard S  Jamet D 《Marine pollution bulletin》2003,46(3):346-352

We studied zooplankton contribution to the total particulate phosphatase activity, the kinetics of this activity, the relation to the different taxonomic groups and the role of particle-bound bacteria. The activity of total particulate material collected from a liter of seawater was more elevated in May, June and August than during the rest of the year. These high activities resulted from a high contribution of the >90 microm fraction which account then for more than 60% of the total particulate activity. Two Michaelian processes with high and low V(max) were disclosed on this fraction. The high V(max) component was responsible for the high summer activities. During these periods, high densities of cirriped Cypris were found which were statistically correlated with this high V(max) component as with its specific activity. Moreover, the contribution of attached bacteria to these high activities was low. In return, this contribution was predominant during the periods of low activity. A simple method was developed to characterise this bacterial activity.  相似文献