Caractérisation des variations lithologiques saisonnières des sédiments de la baie de Seine orientale ; impact des crues de la Seine (France)Characterisation of seasonal lithological variations of the superficial sediment in the eastern part of the Bay of Seine: impact of floods Seine River (France)     

Sébastien Garnaud  Patrick Lesueur  Sandric Lesourd  Nicole Poupinet  Jean-Claude Brun-Cottan 《Comptes Rendus Geoscience》2002,334(5):323-330

This paper presents the first results obtained during cruises since 1995 in the southeastern part of the Bay of Seine. New sedimentological data concerning sediment samples, box cores and water column measurements have been obtained recently in the framework of the Research Programme PNEC (French National Coastal Environment Programme). Fine sediments are deposited on form of temporary veneers of fluid-to-soft mud formed during high floods episodes. In the subtidal area (<10 m water depth), mobility of fine sediments is important and temporary mud deposited during high discharge period composes part of the distal estuarine system of the Seine River. To cite this article: S. Garnaud et al., C. R. Geoscience 334 (2002) 323–330.  相似文献   

Les ensembles fluviatiles néogènes du bassin subandin d'Équateur et implications dynamiquesThe Neogene fluvial systems of the Ecuadorian foreland basin and dynamic inferences     

Frédéric Christophoul  Patrice Baby  Jean-Claude Soula  Michel Rosero  José Burgos 《Comptes Rendus Geoscience》2002,334(14):1029-1037

A sedimentological study of the Neogene continental infill of the Subandean foreland basin of Ecuador led us to define an evolution of the fluvial system from an alluvial plain to an alluvial fan with an increasing slope in the same time as the drainage changed from mostly longitudinal to transverse. Combined with the data presently available on palaeotopography, exhumation, tectonic evolution and geomorphology, these results enable us to infer that, in contrast with the other Subandean foreland basins of Bolivia and Peru, the progradation of the Neogene alluvial fans proceeded by an overall expansion, associated with a relatively small tectonic shortening and not as a result of the development of successive thrust-related depocentres. This also indicates that the surrection of the Cordillera progressed in Ecuador throughout the Neogene. To cite this article: F. Christophoul et al., C. R. Geoscience 334 (2002) 1029–1037.  相似文献   

East Asia plate tectonics since 15 Ma: constraints from the Taiwan region   总被引：4，自引：0，他引：4  

Jean-Claude Sibuet  Shu-Kun Hsu  Xavier Le Pichon  Jean-Pierre Le Formal  Donald Reed  Greg Moore  Char-Shine Liu   《Tectonophysics》2002,344(1-2)

15 Ma ago, a major plate reorganization occurred in East Asia. Seafloor spreading ceased in the South China Sea, Japan Sea, Taiwan Sea, Sulu Sea, and Shikoku and Parece Vela basins. Simultaneously, shear motions also ceased along the Taiwan–Sinzi zone, the Gagua ridge and the Luzon–Ryukyu transform plate boundary. The complex system of thirteen plates suddenly evolved in a simple three-plate system (EU, PH and PA). Beneath the Manila accretionary prism and in the Huatung basin, we have determined magnetic lineation patterns as well as spreading rates deduced from the identification of magnetic lineations. These two patterns are rotated by 15°. They were formed by seafloor spreading before 15 Ma and belonged to the same ocean named the Taiwan Sea. Half-spreading rate in the Taiwan Sea was 2 cm/year from chron 23 to 20 (51 to 43 Ma) and 1 cm/year from chron 20 (43 Ma) to 5b (15 Ma). Five-plate kinematic reconstructions spanning from 15 Ma to Present show implications concerning the geodynamic evolution of East Asia. Amongst them, the 1000-km-long linear Gagua ridge was a major plate boundary which accommodated the northwestward shear motion of the PH Sea plate; the formation of Taiwan was driven by two simple lithospheric motions: (i) the subduction of the PH Sea plate beneath Eurasia with a relative westward motion of the western end (A) of the Ryukyu subduction zone; (ii) the subduction of Eurasia beneath the Philippine Sea plate with a relative southwestward motion of the northern end (B) of the Manila subduction zone. The Luzon arc only formed south of B. The collision of the Luzon arc with Eurasia occurred between A and B. East of A, the Luzon arc probably accreted against the Ryukyu forearc.  相似文献   

A classification of rhizogenic (root-formed) calcretes, with examples from the Upper Jurassic-Lower Cretaceous of Spain and Upper Cretaceous of southern France — Discussion     

Pierre Freytet  Jean-Claude Plaziat  Eric P. Verrecchia   《Sedimentary Geology》1997,110(3-4):299-303

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Preliminary results on a high east–west gradient in the macrozoobenthic community structure of the macrotidal Mont Saint-Michel bay     

Sbastien Thorin  Alain Radureau  Eric Feunteun  Jean-Claude Lefeuvre 《Continental Shelf Research》2001,21(18-19)

Environmental conditions in terms of river inputs, salt marsh development, shellfish cultures, hydrodynamics and sediment characteristics are very different from the western and the eastern part of the Mont Saint-Michel bay. A large scale study on the spatial structure of the intertidal macrozoobenthic community was then performed at the bay scale in order to determinate how these various conditions may modify the community composition and species density. In terms of density, the community was globally dominated by suspension/deposit filter-feeding bivalves, as well as amphipods in the eastern high levels of the intertidal zone. Several biocoenotic assemblage of the Macoma balthica community were described and large differences in the species composition and density were observed between the eastern and the western sectors of the bay. Total density for all species and recruitment were much higher in the eastern sector than in the west. We discussed about these east–west variations in terms of hydrodynamics, sedimentation processes and trophic conditions. Indeed, the large salt marsh extension and river inputs, as well as the lack of shellfish cultures in the east, may favour high food availability for benthic invertebrates of the area whereas the low river inputs and salt marsh development, the high sedimentation process and the intensification of mussel and oyster cultures in the west may create less favourable environments.  相似文献   

Os isotope systematics of komatiitic basalts from the Vetreny belt, Baltic Shield: evidence for a chondritic source of the 2.45 Ga plume     

I. Puchtel  G. Brügmann  A. Hofmann  V. Kulikov  V. Kulikova 《Contributions to Mineralogy and Petrology》2001,140(5):588-599

The Vetreny belt in the southeast Baltic Shield is a large volcano-sedimentary basin containing a 4- to 8-km-thick sequence of basaltic to komatiitic lavas, which were erupted ~2.45 Ga ago in a continental rift setting during the interaction of a mantle plume and the Archean continental crust of the Karelian granite-greenstone terrane. Re-Os isotope data for olivine cumulate samples and chromite separates from Victoria's lava lake and Golets flow 3 define isochrons with ages of 2387ᇍ and 2432ᆶ Ma, respectively. These ages are in good agreement with the previously reported, and new, Nd-Pb and U-Pb zircon ages. These data, coupled with the evidence for immobile behavior of the Re and Os, indicate that the Re-Os system remained closed since the lava eruption. The weighted average initial %¹⁸⁷Os values range between -0.43ǂ.10 for Golets flow 3 and -0.07ǂ.13 for the lava lake. A single chromite separate from Golets flow 1 has a %¹⁸⁷Os(T) of -0.06ǂ.15. Nd-Pb isotope and lithophile trace element data for the Vetreny belt komatiitic basalts were used to monitor the effect of crustal contamination on the Os isotope system and to estimate the initial Os isotope composition of the Vetreny plume source to be approximately chondritic with a %¹⁸⁷Os(T) of -0.9. This implies that the mantle source evolved with a long-term nearly chondritic Re/Os ratio. The data provide further evidence that, by the end of the late Archean, the Earth's upper mantle was well homogenized with respect to the highly siderophile elements, added during the accretion of a late veneer, on a time scale of ~1 Ga.  相似文献   

Trace element and isotopic composition of baddeleyite   总被引：3，自引：0，他引：3  

Dr. T. Reischmann  G. E. Brügmann  K. P. Jochum  W. A. Todt 《Mineralogy and Petrology》1995,53(1-3):155-164

Summary Baddeleyite from Palabora Igneous Complex, South Africa, is among the purest natural ZrO₂ phases. This has been demonstrated by using various methods, i.e. microprobe, neutron activation, spark source and thermal ion mass spectrometry. HfO₂ with 1.87% is the only other major component. The concentrations of other HFSE are also relatively high, compared to most other elements, that reach only a few ppm.The REE display a U-shaped pattern that is interpreted to be superimposed by a strongly LREE enriched source component. The high⁸⁷Sr/⁸⁶Sr initial of 0.713085 and the negative Nd_t of –10.7 prove that this component was LILE enriched for a long time prior to the formation of the Palabora Igneous Complex. These data indicate that the baddeleyite crystallized from a magma which was derived from an enriched mantle reservoir, similar to that involved in the formation of group II kimberlites.

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Spurenelemente und Isotopenzusammensetzung von Baddeleyit

Zusammenfassung Baddeleyit vom Palabora Igneous Complex, Südafrika, gehört zu den reinsten natürlichen Vorkommen von ZrO₂. Dies wurde durch Analysen mit verschiedenen Methoden wie Mikrosonde, Neutronenaktivierung, Funken- und Thermionenmassenspektrometrie bestätigt. HfO₂ ist mit 1.87 die einzige andere Hauptkomponente, auch die Konzentrationen der anderen HFSE sind relativ hoch im Vergleich zu den anderen Elementen, die nur wenige ppm erreichen.Die REE bilden ein U-förmiges Muster, das als Ausdruck einer stark LREE angereicherten Komponente im Ausgangsgestein gedeutet wird. Das hohe⁸⁷Sr/⁸⁶Sr-Initialverhältnis von 0.713085 und das negative Nd_t von -10.7 belegen, daß diese Komponente über einen langen Zeitraum vor der Bildung des Palabora Igneous Complex angereichert gewesen war. Diese Daten deuten an, da der Baddeleyit aus einem Magma kristallisierte, das aus einem angereicherten Mantelreservoir stammte, ähnlich dem, das bei der Bildung der Gruppe 11 Kimberlite beteiligt war.

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Climatic fluctuation in the Czech Lands during the last millennium     

Rudolf Brázdil 《GeoJournal》1994,32(3):199-205

On the basis of documentary evidence, proxy-data and instrumental observations, the climatic fluctuation during the last millennium in the Czech Lands is analysed. According to narrative sources, the warmest period falls between the 1260s–1380s, documents for Lamb's (1984) Medieval Warm Epoch in 1150–1300 are missing. The prevalence of extremely cold and also rainy periods, as an expression of the Little Ice Age, is most conspicuous in the 15th century, in the 1590s and, with three interruptions, between the 1730s–1850s. Since the latter half of the 19th century a rising temperature trend has manifested itself. A regional climatic scenario for the model of global warming is discussed in relation to the observed trends in the Czech Lands.  相似文献   

Measuring the chemical composition of cosmic rays at ∼ 1013–1015 eV by utilizing the solar and geomagnetic fields     

J. Heintze  P. Lennert  S. Polenz  B. Schmidt  J. Spitzer  W. Brückner  W. Hofmann  B. Povh 《Experimental Astronomy》1989,1(1):21-34

According to a proposal of Lloyd-Evans (1985), the average charge of particles in the cosmic radiation near 10¹⁴eV can be determined by observing the effect of the solar magnetic field on the Sun's shadow in the angular distribution of energetic primary cosmic ray particles. This suggestion is shown to be realizable with a new type of EAS-array proposed for the purpose of high energy -ray astronomy. The same measurement provides information on the integrated strength of the solar magnetic field. As the array will be sensitive and provide good angular resolution down to a few times 10¹²eV, more detailed results on the primary composition near 10¹³eV can be obtained by investigating the shape of the shadow of the Moon as affected by the geomagnetic field.  相似文献   

Editorial to announce online submission for Climate Dynamics     

Jean-Claude Duplessy  Elisa Manzini  Edwin K. Schneider 《Climate Dynamics》2007,28(1):1

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