Estuarine conservation and restoration: the Somme and the Seine case studies (English Channel, France)     

Ducrotoy JP  Dauvin JC 《Marine pollution bulletin》2008,57(1-5):208-218

Megatidal estuaries such as the Seine and the Somme (North-Western France) are rather well delimited and human impacts on them are well understood. Since the middle of the 19th Century, there has been a slow but irreversible degradation of the state of these English Channel estuaries. However, current conservation and restoration strategies tend to freeze habitats in a particular state, their status being defined, most often, through a patrimonial or utilitarian approach. Connectedness between biotopes (sensu habitat+community) has a tendency to be neglected, especially with regard to main ecological gradients, i.e., salinity. In this paper, evaluation methodologies are proposed with the intention of assessing changes to ecosystem functions, under anthropogenic disturbance, controlled or otherwise. The Seine (a heavily industrialised ecosystem) is compared to the Somme (considered here for its pseudo-natural features) in order to discriminate between oceanic processes (siltation and plugging of estuaries) and anthropogenic influences. Preservation and restoration of habitats rely on a robust scientific methodology. The multi-scale approach adopted in the projects presented here relies on sensitive socio-ecological assessment procedures, tools for evaluating ecological quality, and well-built monitoring programmes based upon pertinent indicators. Such managerial tools were used to refine strategies and make them compatible with the sustainable co-development of resources in a European context. This paper demonstrates how scientists were able to acquire and apply knowledge in the field of rehabilitation and restoration. Jointly with managers and policy-makers, they have brought scientific information and socio-economics together in order to answer questions about the restoration of sites or habitats and to anticipate future propositions in the spirit of Integrated Coastal Zone Management (ICZM).  相似文献   

TRANSPORTATION AND TERRITORIAL DEVELOPMENT IN THE SINGAPORE EXTENDED METROPOLITAN REGION   总被引：3，自引：0，他引：3  

Jean-Paul Rodrigue 《Singapore journal of tropical geography》1994,15(1):56-74

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Organic nitrogen chemistry during low-grade metamorphism   总被引：1，自引：0，他引：1  

Jean-Paul Boudou  Arndt Schimmelmann  Maria Mastalerz  Léon Gengembre 《Geochimica et cosmochimica acta》2008,72(4):1199-1221

Most of the organic nitrogen (N_org) on Earth is disseminated in crustal sediments and rocks in the form of fossil nitrogen-containing organic matter. The chemical speciation of fossil N_org within the overall molecular structure of organic matter changes with time and heating during burial. Progressive thermal evolution of organic matter involves phases of enhanced elimination of N_org and ultimately produces graphite containing only traces of nitrogen. Long-term chemical and thermal instability makes the chemical speciation of N_org a valuable tracer to constrain the history of sub-surface metamorphism and to shed light on the subsurface biogeochemical nitrogen cycle and its participating organic and inorganic nitrogen pools. This study documents the evolutionary path of N_org speciation, transformation and elimination before and during metamorphism and advocates the use of X-ray photoelectron spectroscopy (XPS) to monitor changes in N_org speciation as a diagnostic tool for organic metamorphism. Our multidisciplinary evidence from XPS, stable isotopes, traditional quantitative coal analyses, and other analytical approaches shows that at the metamorphic onset N_org is dominantly present as pyrrolic and pyridinic nitrogen. The relative abundance of nitrogen substituting for carbon in condensed, partially aromatic systems (where N is covalently bonded to three C atoms) increases exponentially with increasing metamorphic grade, at the expense of pyridinic and pyrrolic nitrogen. At the same time, much N_org is eliminated without significant nitrogen isotope fractionation. The apparent absence of Rayleigh-type nitrogen isotopic fractionation suggests that direct thermal loss of nitrogen from an organic matrix does not serve as a major pathway for N_org elimination. Instead, we propose that hot H, O-containing fluids or some of their components gradually penetrate into the carbonaceous matrix and eliminate N_org along a progressing reaction front, without causing nitrogen isotope fractionation in the residual N_org in the unreacted core of the carbonaceous matrix. Before the reaction front can reach the core, an increasing part of core N_org chemically stabilizes in the form of nitrogen atoms substituting for carbon in condensed, partially aromatic systems forming graphite-like structural domains with delocalized π-electron systems (nitrogen atoms substituting for “graphitic” carbon in natural metamorphic organic matter). Thus, this nitrogen species with a conservative isotopic composition is the dominant form of residual nitrogen at higher metamorphic grade.  相似文献   

Geodynamic evolution of Korea: A view   总被引：2，自引：0，他引：2  

Dominique  Cluzel Jean-Paul  Cadet† 《Island Arc》1992,1(1):64-70

Abstract Evidence for South Korean Palaeozoic geodynamic evolution is restricted to the Ogcheon Belt, which is a complex polycyclic domain forming the boundary between the Precambrian Gyeonggi Block to the northwest and the Ryeongnam Block to the southeast. Two independent sub-zones can be distinguished: the Taebaeksan Zone to the northeast and the Ogcheon Zone sensu stricto. The Taebaeksan Zone and Ryeongnam Block display characteristic features of the North China palaeocontinent. This domain remained relatively stable during the Palaeozoic. In contrast, the Ogcheon Belt s. s. is a highly mobile zone that belongs to the South China palaeocontinent and corresponds to a rift that opened during the Early Palaeozoic. In lowermost Devonian times, the rift basin was closed and the Ogcheon Belt was structured in a pile of nappes. From the lack of suture in the Ogcheon Belt it can be inferred that the Gyeonggi Block belongs to the South China palaeocontinent. Thus, the boundary between the North China and South China blocks should be located to the north of Gyeonggi Block, that is, in the Palaeozoic Imjingang Belt. From the Middle Carboniferous, sedimentation started again on a weakly subsiding paralic platform located in the hinterland of the Late Palaeozoic orogen of southwest Japan. In the Late Carboniferous, increasing subsidence recorded extensional tectonics related to the opening of the Yakuno Oceanic Basin (southwest Japan). In the Middle Permian, the end of marine influences in the platform and emplacement of terrestrial coal measures, may be correlated with the closure of the oceanic area and subsequent ophiolite obduction. In Late Permian to Early Triassic times, the Honshu Block (the eastern palaeomargin of the Yakuno Basin) collided with Sino-Korea. Post-collisional intracontinental tectonics reached the Ogcheon Belt in the Middle Triassic (Songnim tectonism). Ductile dextral shear zones associated with synkinematic granitoids were emplaced in the southwest of the belt. In the Upper Triassic, the late stages of the intracontinental transcurrent tectonics generated narrow intramontane troughs (Daedong Supergroup). The Daedong basins were deformed during two tectonic events, in the Middle (?) and Late Jurassic. The Upper Jurassic to Lower Cretaceous basins (Gyeongsang Supergroup), that are controlled by left-lateral faults, may have resulted from the same tectonic event.  相似文献   

The landscape-unit approach applied to geology, on SPOT images, in temperate climate zones using a test-area in the Cévennes (Massif Central, France)     

Jean-Paul Deroin  Jean Chorowicz  Thierry Deroin  Phillippe Dutarte  Jean-Yves Scanvic  Andr Simonin 《ISPRS Journal of Photogrammetry and Remote Sensing》1990,45(5-6)

Classification image processing is based mainly upon spectral features but this information alone is inadequate for drawing comprehensive maps or reliably distinguishing lithological or structural targets, especially in vegetation-covered areas. It is therefore of interest to explore an approach in which subtle features of the image are matched with field data in a variety of parameters either measured or assessed qualitatively. This approach is necessarily multidisciplinary, the three basic aspects being geomorphological, botanical and geological.The Cévennes massif, in southern France, with its sedimentary margins was selected as a test area, having both varied geology, giving a variety of landscapes, and a range of climatic zones, from Mediterranean to sub-Alpine.The present work is distinguished by its use of the landscape unit, which is rarely considered in geology. Landscapes units are recognized and defined, and the spectral homogeneity of the units is then assessed. They are combined with satellite and other data in order to improve the digital processing for geological purposes.The parameters characterising each landscape unit define the various elements contributing to the landscape, the most important of which are morphology, vegetation and geology, and their interactions. Our results using these parameters show the interest of the management of both the satellite (SPOT in this case) and non-satellite (exogenous) data.  相似文献   

Effects of scattered solar radiation and absorption by SO₂ on the photodissociation processes in the stratosphere of Venus     

Jean-Paul Parisot  Guy Moreels  Jean-Marc Zucconi 《Icarus》1980,44(3):640-650

In the stratosphere of Venus, the available luminous flux which locally produces the photodissociation processes at a given altitude may be divided into three parts: direct incoming downward flux, flux resulting from the reflection on the surface of the clouds, and flux due to molecular scattering. A relatively simple computation method has been used to evaluate the relative importance of these three parts at altitudes between 65 and 100 km. It is shown that the extra contribution of the reflected and scattered fluxes to photodissociation processes cannot be neglected in the uv and visible regions. In the case of SO₂, for instance, which presents an absorption band in the uv, the photodissociation coefficient is increased 30% due to these effects. Calculations of the photodissociation coefficients of CO₂, O₃, H₂S, and SO₂ are presented. As a result of the increase by 60% in the ozone photolysis rate, the calculated O₂ infrared band at 1.27 μm is larger by a factor of nearly 2 than is expected from a calculation without taking albedo or scattering into account.  相似文献   

Cold seep communities in the deep eastern Mediterranean Sea: composition, symbiosis and spatial distribution on mud volcanoes   总被引：2，自引：0，他引：2  

Karine Olu-Le Roy  Myriam Sibuet  Aline Fiala-Mdioni  Serge Gofas  Carmen Salas  Andr Mariotti  Jean-Paul Foucher  John Woodside 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1915-1936

Two mud volcano fields were explored during the French–Dutch MEDINAUT cruise (1998) with the submersible NAUTILE, one south of Crete along the Mediteranean Ridge at about 2000 m depth (Olimpi mud field) and the other south of Turkey between 1700 and 2000 m depth (Anaximander mud field) where high methane concentrations were measured. Chemosynthetic communities were observed and sampled on six mud volcanoes and along a fault scarp. The communities were dominated by bivalves of particularly small size, belonging to families commonly found at seeps (Mytilidae, Vesicomyidae, Thyasiridae) and to Lucinidae mostly encountered in littoral sulfide-rich sediments and at the shallowest seeps. Siboglinid polychaetes including a large vestimentiferan Lamellibrachia sp. were also associated. At least four bivalve species and one siboglinid are associated with symbiotic chemoautotrophic bacteria, as evidenced by Transmission Electronic Microscopy and isotopic ratio measurements. Among the bivalves, a mytilid harbors both methanotrophic and sulfide-oxidizing bacteria. Video spatial analysis of the community distribution on three volcanoes shows that dense bivalve shell accumulations (mainly lucinids) spread over large areas, from 10% to 38% of the explored areas (2500–15000 m²) on the different volcanoes. Lamellibrachia sp. had different spatial distribution and variable density in the two mud volcano fields, apparently related with higher methane fluxes in the Anaximander volcanoes and maybe with the instability due to brines in the Olimpi area. The abundance and richness of the observed chemosynthetic fauna and the size of some of the species contrast with the poverty of the deep eastern Mediterranean. The presence of a specialized fauna, with some mollusk genera and species shared with other reduced environments of the Mediterranean, but not dominated by the large bivalves usually found at seeps, is discussed.  相似文献   

Changes in seabed morphology, mud temperature and free gas venting at the Håkon Mosby mud volcano, offshore northern Norway, over the time period 2003–2006     

Jean-Paul Foucher  Stéphanie Dupré  Carla Scalabrin  Tomas Feseker  François Harmegnies  Hervé Nouzé 《Geo-Marine Letters》2010,30(3-4):157-167

The Håkon Mosby mud volcano is a 1.5-km-diameter geological structure located on the Southwest Barents Sea slope at a water depth of 1,270 m. High-definition seabed mapping of the mud volcano has been carried out in 2003 and 2006. A comparative analysis of the bathymetry and backscatter maps produced from the two surveys shows subtle morphological changes over the entire crater of the mud volcano, interpreted to be the consequence of mud eruption events. Mud temperature measurements point to a persistently warm mud at shallow depth in the crater. This is explained by upward fluid advection, rather than conductive cooling of mud flows. The small-scale spatial variability in the temperature distribution may be related to mud outflows or changes in the fluid flow regime. Furthermore, the locations of free gas venting observed in 2006 were found to differ from those of 2003. Our observations of overall similar topographic profiles across the mud volcano in 2003 and 2006 suggest that eruption events would have been modest. Nevertheless, the data bring evidence of significant change in activity even over short time intervals of only 3 years. This may be a characteristic shared by other submarine mud volcanoes, notably those considered to be in a quiescent stage.  相似文献   

Nonlinear modal analysis of penetrative convection     

Jean-Paul Zahn  Juri Toomre  Jean Latour 《地球物理与天体物理流体动力学》2013,107(1-2):159-193

Abstract

The modal expansion procedure has been used to analyze penetrative convection that arises when a thin unstable layer is embedded between two stable regions. The Boussinesq approximation is applied in which the effect of compressibility and stratification are neglected. Various calculations have been made, with one and two modes, for Rayleigh numbers ranging from the critical value to more than 10⁵ times critical. The effect of decreasing the Prandtl number has also been investigated.

It is found that in the nonlinear regime, the convective motions penetrate substantially into the stable regions. The flux of kinetic energy plays a crucial role in such penetration, and its existence puts some requirements on the motions: in the single-mode case, they need to be three-dimensional. The extent of penetration amounts to about half of the thickness of the unstable layer on each side of it when the degree of instability and that of stability are comparable in the two domains; it increases as the stability of the outer region is lowered. The penetration depth appears to be independent of all other parameters defining the problem.  相似文献   

Preface: Symposium on Stegosauria proceedings     

Jean-Paul Billon-Bruyat  Daniel Marty 《Swiss Journal of Geoscience》2010,103(2):139-141

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