New U-Pb zircon and Ar/Ar muscovite age constraints on the emplacement of the Lizio syn-tectonic granite (Armorican Massif, France)     

Romain Tartèse  Marc Poujol  Gilles Ruffet  Philippe Boulvais  Philippe Yamato  Jan Košler 《Comptes Rendus Geoscience》2011,343(7):443-453

LA-ICP-MS U-Pb analyses performed on zircon grains from the Lizio granite yielded an emplacement age of 316 ± 6 Ma. Typical S-C structures show that the Lizio granite was emplaced contemporaneously with dextral shearing along the northern branch of the South Armorican Shear Zone and that it was therefore active at that time. ⁴⁰Ar/³⁹Ar analyses performed on muscovite grains yielded plateau dates ranging between 311.5 and 308.2 Ma. Muscovite chemistry is typical of primary magmatic muscovite, which precludes a late fluids-induced resetting of the K-Ar isotopic system. ⁴⁰Ar/³⁹Ar dates thus likely correspond to the cooling ages below the argon closure temperature. Considering the uncertainties on the measured ages, we can propose that either the Lizio granite cooled down quickly in less than a million of years or that it remained in a hot environment for several millions of years after its emplacement. This latter scenario could have been sustained by shear heating during dextral shearing along the northern branch of the South Armorican Shear Zone.  相似文献   

Contribution of hydrodynamic conditions during shallow water stages to the sediment balance on a tidal flat: Mont-Saint-Michel Bay, Normandy, France   总被引：1，自引：0，他引：1  

R. Desguée  N. Robin  L. Gluard  E.J. Anthony 《Estuarine, Coastal and Shelf Science》2011,94(4):343-354

Field measurements were conducted in Mont-Saint-Michel Bay, a megatidal embayment (spring tidal range of 15 m), in order to monitor, over the course of a tidal cycle, sediment transport variability due to waves and tides on the upper part of a tidal flat characterised by shallow water depths. Sensors used to measure currents, water depth and turbidity were installed just above the bed (0.04 m). Two experiments were conducted under contrasting hydrodynamic conditions. The results highlight wave activity over the tidal flat even though observed wind waves were largely dissipated due to the very shallow water depths. Very high suspended sediment concentrations (up to 6 kg/m³) were recorded in the presence of wave activity at the beginning of the local flood, when significant sediment transport occurred, up to 7 times as much as under conditions of no wave activity. This influence may be attributed to the direct action of waves on bed sediments, to wave-induced liquefaction, and to the erosive action of waves on tidal channel banks. The sediment composition, comprising a clay fraction of 2-5%, may also enhance sediment transport by reducing critical shear stress through the sand lubrication effect. The results also show that antecedent meteorological conditions play an important role in suspended sediment transport on the tidal flat. Total sediment flux directions show a net transport towards the inner part of the bay that contributes to deposition over the adjacent salt marshes, and this tendency also prevails during strong wave conditions. Such sediment transport is characterised by significant variability over the course of the tidal cycle. During fair and moderate weather conditions, 83% and 71% of the total flux was observed, respectively, over only 11% and 28% of the duration of the local tidal cycle and with water depths between 0.04 and 0.3 m. These results suggest that in order to improve our understanding of sediment budgets in this type of coastal environment, it is essential to record data just at the beginning and at the end of tidal submergence close to the bed.  相似文献   

Planning the sea: The French experience. Contribution to marine spatial planning perspectives     

Brice Trouillet  Thierry Guineberteau  Mathilde de Cacqueray  Julien Rochette 《Marine Policy》2011

As marine spatial planning is developing, prompted by the European Union through common principles prescribed in a road map, it is important to disseminate and analyse what has been put forward as the French experience in this field. Hence, the experience of the schémas de mise en valeur de la mer immediately proves to be original in its framework and deeply rooted in French specificities. However, a further analysis of this procedure implemented over several decades highlights the perspectives that would be worth integrating into French and European considerations. This paper thus provides information referring to the SMVM experience, presents an analysis of its results, and attempts to draw lessons from it with regard to recent developments in French marine policy.  相似文献   

Early and Middle Pleistocene vegetation history of the Médoc region,southwest France     

C. E. O'Brien  R. L. Jones 《第四纪科学杂志》2003,18(6):557-579

Pleistocene deposits, together with their pollen, plant macrofossil, foraminiferal, dinoflagellate and coleopteran remains, from five sites along the Atlantic coast of the Médoc Peninsula are described and discussed. Sediments making up the Négade Formation are shown to have been laid down under either estuarine or lagoonal conditions when closed Quercus–Pinus‐Tsuga canadensis regional woodland existed. Comparison with plant records from The Netherlands indicates that these deposits are most likely attributable to either the Early Pleistocene Bavel Interglacial (marine oxygen isotope stage (MIS) 31), or an interglacial of the Waalian (MIS 37–49) or Tiglian (MIS 63–79). In addition, clays assigned to the Argiles du Gurp sensu stricto, were similarly deposited in either an estuary or lagoon, which subsequently was cut off from the sea. A freshwater lake with vegetation dominated by Azolla filiculoides then developed. This was succeeded by reedswamp and an organic mud (termed Lignite in the corresponding French stratigraphical records) formed. Regional Quercus–Abies woodland was replaced by one with Pinus dominant and Pterocarya a minor component. Comparison with plant records from France and other parts of Europe suggest that the clays and organic mud might be correlated with the Holsteinian (Praclaux) Interglacial (MIS 11c). Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Molluscan successions from the Holocene tufa of St Germain‐le‐Vasson,Normandy (France) and their biogeographical significance     

Nicole Limondin‐Lozouet  Richard C. Preece 《第四纪科学杂志》2004,19(1):55-71

A detailed molluscan succession from a 10 m thick deposit of Holocene tufa at St Germain‐le‐Vasson, Normandy, provides the most complete record from northern France and has shed new light on the historical biogeography of several species of land snail. The succession has been reconstructed from four profiles and a chronology provided by accelerator mass spectrometry radiocarbon dating of charcoal, wood and shell. The onset of tufa formation occurred after 9700±90 yr BP and persisted until 4213±77 yr BP. The tufa appears to have accumulated at a remarkably constant rate (14.4–16.5 cm 100 yr^?1), except for the upper levels, where the rate increases fourfold. The succession has been divided into six local molluscan zones. An early assemblage consisting of ecologically tolerant species and those indicative of marshy grassland is replaced by a sequence of shade‐demanding taxa, reflecting the encroachment of woodland. Shaded conditions persist until the end of the sequence but the most hygrophilous elements decline after 5422±60 yr BP (zone 5), a change also reflected in the tufa lithology by the development of silty grey horizons. Notable species recovered from the tufa include Acicula fusca, Vertigo substriata, V. alpestris, V. moulinsiana (all rare or unknown living in northern France). Hygromia limbata, a twentieth century introduction to Britain, was previously thought to be a relatively recent arrival in northern France, but its record at St Germain shows that it has been present in Normandy since 6500 yr BP. Azeca goodalli, another shade‐demanding species, appeared at St Germain much later, just after 4420±65 yr BP. Several other species present in the tufa, such as Pomatias elegans, no longer live on the site, adding to the evidence for a distributional decline in Normandy and elsewhere. Perhaps the most noteworthy record is that of Leiostyla anglica, between about 8500 yr BP and 5000 yr BP, because this constitutes its only Holocene occurrence from mainland Europe. Following this discovery it seems likely that further Holocene sites with L. anglica may be found along the western seaboard of Europe connecting populations in Iberia with those of the British Isles. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

赫德和中法和约     

廖宗麟  张壮强 《广东海洋大学学报》2002,22(2):82-86

中法战争期间 ,中国海关总税务司赫德积极插手中法谈判 ,在不同的阶段中扮演了不同的角色。在充当法国侵略者的帮凶遭到中国政府和人民的坚决反对后 ,他在照顾中国利益的基础上 ,促成了中法两国签订了和约 ,结束了战争  相似文献   

Income inequality in the UK: Comparisons with five large Western European countries and the USA     

《Applied geography (Sevenoaks, England)》2015

This paper concentrates on the 1% richest households in the UK in a comparison with the other four large Western European countries: Germany, France, Italy and Spain. In the European context the UK is an outlier of extreme inequality. Individual level tax data has shown this previously, but earlier research did not make comparisons at the household level, or in as much detail as it is possible to show now given new survey findings.In the UK the geographical separation of the 1% from mainstream society increased in recent decades as their incomes levels diverged widely from that of the mainstream. There is now acute socioeconomic polarization in the UK as compared to the other large European states because of the current extent of income and wealth inequalities in the UK. Not so long ago members of the best-off 1% within the UK were far more evenly spread across both the space and society of the UK than they are today.The UK is now the European country most similar to the USA in terms of income inequalities. Along with Sweden it was least like the USA in the 1960s. This paper concludes by considering what might happen (if current trends continue) to standards of living in general, social spatial polarization, fear and mistrust. Growing income inequalities increase wealth inequalities. Some info-graphics aimed at showing the contemporary extent of wealth inequalities in the UK and USA are presented in conclusion and for use in teaching  相似文献   

Non-marine selachians from the basal Cretaceous of Charente,SW France     

《Cretaceous Research》2013

A gypsum quarry at Cherves-de-Cognac in south-western France exposes a large section of Berriasian (basal Cretaceous) sediments deposited in a lagoonal environment. The sediments have yielded rich vertebrate faunas, but only two species of selachians are present; the lonchidiid hybodont Parvodus celsucuspus sp. nov. and the batoid Belemnobatis variabilis. The composition of the fauna, including only a single, seemingly endemic, hybodont species from a time when hybodont faunas are relatively well investigated in Europe, indicate that small hybodonts were not able to migrate longer distances. The recorded batoid species also occurs in southern England, demonstrating that these batoids were primarily marine fishes that regularly explored areas with reduced salinity.  相似文献   

Caractérisation de l'effluent de vidange d'un étang de pisciculture extensive     

Dominique Vallod  Benoit Sarrazin 《水文科学杂志》2013,58(3):394-402

Résumé Afin d'évaluer l'impact potentiel de la vidange, les flux de nutriments et de matières sont quantifiés lors du remplissage et de la vidange d'un étang construit en dérivation, à l'aval d'une chaîne d'étangs. La cinétique de vidange a été établie à l'aide d'un modèle numérique de terrain restituant la surface topographique de l'étang. Les matières en suspension et les principaux nutriments ont été régulièrement quantifiés. La qualité hydrobiologique du cours d'eau récepteur a été contrôlée pendant et après la vidange. L'étang a exporté 8.5 tonnes de matières en suspension et des quantités de nutriments relativement élevées. Nos résultats confirment l'existence de deux phases critiques, ne concernant cependant qu'un très faible volume d'effluent. Compte tenu des capacités élevées de sédimentation des matières en suspension, la courte durée d'exposition associée à un linéaire de fossés suffisant pourrait limiter l'impact de ces matières rejetées.

Citation Vallod, D. & Sarrazin, B. (2010) Caractérisation de l'effluent de vidange d'un étang de pisciculture extensive. Hydrol. Sci. J. 55(3), 394–402.  相似文献   

Quantifying 21st-century France climate change and related uncertainties   总被引：1，自引：0，他引：1  

Laurent Terray  Julien Boé 《Comptes Rendus Geoscience》2013,345(3):136-149

We tackle here the question of past and future climate change at sub-regional or country scale with the example of France. We assess France climate evolution during the 20th and 21st century as simulated by an exhaustive range of global climate simulations. We first show that the large observed warming of the last 30 years can be simulated only if anthropogenic forcings are taken into account. We also suggest that human influence could have made a substantial contribution to the observed 20th century multi-decadal temperature fluctuations. We then show that France averaged annual mean temperature at the end of the 21st century is projected to be on the order of 4.5 K warmer than in the early 20th century under the radiative concentration pathways 8.5 (RCP8.5) scenario. Summer changes are greater than their winter counterpart (6 K versus 3.7 K). Near-future (2020–2049) changes are on the order of 2.1 K (with 2.6 K in summer and 1.8 K in winter). Model projections also suggest a substantial summer precipitation decrease (−0.6 mm/day), in particular over southern France, and a moderate winter increase, (0.3 mm/day), mostly over the northernmost part of France. Uncertainties about the amplitude of these precipitation changes remain large. We then quantify the various sources of uncertainty and study how their ranking varies with time. We also propose a physically-based metric approach to reduce model uncertainty and illustrate it with the case of summer temperature changes. Finally, timing and amplitude of France climate change in case of a global average 2-K warming are investigated. Aggressive mitigation pathways (such as RCP2.6) are absolutely required to avoid crossing or barely exceeding the 2-K global threshold. However, France climate change requiring adaptation measures is still to be expected even if we achieve to remain below the 2-K global target.  相似文献