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1.
We have organised afield study of ocean tide loading in the northwestern part of France, where tidal amplitudes are known to be among the highest in the world. GPS and gravimetric techniques have already proved their capability to measure such weak and high-frequency signals. In this study, these classical observations are complemented with less usual techniques, such as tiltmeter and Satellite Laser Ranging (SLR) measurements. We present here the preliminary results for a common period of observations spanning from 12–19 May 2004. Additional measurements from the French Transportable Laser Ranging Station (FTLRS) were available during September and October 2004. Observation residuals are computed as the difference between the observed and the predicted time signals. We obtain small RMS residuals for GPS measurements (2.5/3.1/4.5 mm for the eastward, northward and upward components), for absolute and relative gravimetry (9 nm/s2 and 13 nm/s2) and for tiltmeters (0.05 μrad for EW component). We also fit the amplitude of the main M2 tidal constituent to FTLRS observations and we find a value of 3.731 cm, which is comparable to the theoretical value.  相似文献   
2.
The spinel peridotite from the Anyemaqen suture contains ?5% residual clinopyroxene and is characterized by a high abundance of the magmaphile elements Fe, Al and Ti in the primary mineral phases. Our data demonstrate that this rock represents residual mantle material, which has been affected by less than 10% partial melting prior to its emplacement. Its textural features indicate that the rock has been plastically deformed in a non-coaxial regime under lithospheric physical conditions at a relatively cool thermal regime below solidus temperature. We suggest that the peridotites from the Anyemaqen suture represent mantle material, which was either emplaced during incipient rifting on the Palaeozoic passive margin of Asia, or uplifted at slow spreading ridge setting in Paleo-Tethyan Ocean. Further researches are needed to make a definite choice between these two alternatives. To cite this article: E.A. Konstantinovskaia et al., C. R. Geoscience 335 (2003).  相似文献   
3.
The mean sea surface temperature anomalies (SSTA) of the Mediterranean Sea during the past 150 years (1856–2000) are analysed. The first empirical orthogonal function (EOF) of the covariance matrix of the SSTA explains more than 45% of the variance, suggesting that the temporal variation of the Mediterranean Sea is largely in phase over the whole basin. The mean variability of Mediterranean SSTA from 1856 to 2000 superposes a main irregular oscillation (period of 60–70 years and mean amplitude of 0.4–0.5 °C) and a weak long-term positive trend (equivalent to an increase of +0.1 °C per century). The last warm phase, which is strongest in the western basin, is not warmer than the decade 1935–1945 or the ending part of the 1960s. The mean temporal evolution of the North Hemisphere is close to the variation of the Mediterranean Sea, except that the long-term increase is more intense in the North Hemisphere. To cite this article: V. Moron, C. R. Geoscience 335 (2003).  相似文献   
4.
The Mid-Cretaceous ‘upper siliceous zone’ of the Vigla Limestone is studied in detail along the Paliambela section of northwestern Greece. Within it two radiolarite horizons can be identified, the lower being rich in organic matter and named herein as the ‘Fourcade level’. The preserved organic matter is of planktic/bacterial origin and of low thermal maturity. The nannoflora contained within the lower marly argillites consists of a poorly preserved and oligospecific assemblage characterised by the total absence of Nannoconids. Radiolarian assemblages yielded from the Fourcade level are dominated by the family Archaeodictyomitridae. Integrated calcareous nannofossil and radiolarian biostratigraphic results suggest an Early Aptian age for the Fourcade level, which can be thus considered as the local expression of the globally recognised Early Aptian Oceanic Anoxic Event (OAE 1a). To cite this article: T. Danelian et al., C. R. Geoscience 334 (2002) 1087–1093.  相似文献   
5.
The building-up of the Andean Range is linked to the subduction of the Pacific lithosphere beneath the South American plate. However, the formation of the Central Andes is marked by continental crustal shortening, whereas accretion and underplating of exotic oceanic terranes occurred in the northern Andes. The study of various magmatic and metamorphic rocks exhumed in the Western Cordillera of Ecuador by Miocene transpressive faults enables us to constrain the nature and thermal evolution of the crustal root of this part of Ecuador. These rocks are geochemically similar to oceanic plateau basalts. The thermobarometric peak conditions of a granulite and an amphibolite indicate temperatures of 800–850?°C and pressures less than 6–9 kbar (lack of garnet). The abnormally high geothermal gradient (≈40?°C?km?1) is probably due to the activity of the magmatic arc, which developed on the accreted oceanic terranes after Late Eocene times, and may have provoked the re-mobilisation of deeply underplated oceanic material during the genesis of the Neogene to Recent arc. To cite this article: É. Beaudon et al., C. R. Geoscience 337 (2005).  相似文献   
6.
The Diagorou-Darbani Birimian greenstone belt includes (i) tholeiitic metabasalts with flat to slightly depleted LREE patterns, (ii) amphibolites having high contents in both compatible and incompatible elements with strongly fractionated spidergrams showing large HFSE negative anomalies, and (iii) metabasalts and amphibolites with intermediate features between the two previous groups. The chemical compositions of these rocks are not those of oceanic plateau basalts, but suggest a magmatic evolution from an arc environment to a back-arc oceanic basin. Source of the highly enriched amphibolites could be a depleted mantle metasomatized by slab-derived siliceous melts. To cite this article: A. Soumaila et al., C. R. Geoscience 336 (2004).  相似文献   
7.
On the ages of flood basalt events   总被引：2，自引：0，他引：2  
We review available data constraining the extent, volume, age and duration of all major Phanerozoic continental flood basalts (CFB or traps) and oceanic plateaus (OP), together forming the group of large igneous provinces (LIP), going from the smallest Columbia flood basalts at ～16 Ma to the as yet ill-known remnants of a possible trap at ～360 Ma in eastern Siberia. The 16 traps (CFB and OP) reviewed form a rather unimodal distribution with an initial modal volume of the order of 2.5 Mkm3. Most provinces agree with a rather simple first order model in which volcanism may have lasted of the order of 10 Ma, often resulting in continental break-up, but where most of the volume was erupted in about 1 Ma or sometimes less. This makes CFBs/OPs (LIPs) major geodynamic events, with fluxes exceeding the total output of present day hot spots and even possibly exceeding over short times the entire crustal production of mid-ocean ridges. The proposed correlation between trap ages and the ages of several geological events, including mass extinctions and oceanic anoxia, is found to have improved steadily as more data have become available, to the point that the list of trap ages may coincide with many major divisions in the geological time scale. The four largest mass extinctions in the last 260 Ma coincide to the best resolution available with four traps, making a causal connection between the two through some form of catastrophic climatic perturbations the most likely hypothesis. The time sequence of LIPs appears to have been random and there is no robust evidence for long time trends in the corresponding crustal production rate over the last 260 Ma.  相似文献   
8.
Résumé

L’étude des Schistes lustrés du transect alpin de la Vanoise a permi de préciser les modalités et la chronologie des événements tectoniques précoces enregistrés dans les Alpes occidentales et ainsi de souligner (|ue l’évolution alpine crétacé-tertiaire ne peut s’interpréter comme un simple continuum de déformations compressives. Doivent être distinguées trois étapes majeures : (1 ) un stade précoce crétacé « moyen » à supérieur responsable de l’enfouissement profond d’unités de la marge nord-léthysicnne et de la fermeture du domaine océanique téthysien alpin. Cet événement se matérialise notamment par des enregistrements tectono-sédimentaires (flyschs à blocs d’ophiolilcs) pendant lu fermeture et aboutit à l’enfouissement d’unités océaniques durant le Sénonien dans des conditions de haute pression. Cet événement se corrèle avec la rotation intra-erétaeé supérieur de l’lbérie ; (2 ) un stade maas-trichtien-paléocène durant lequel aucune évidence de déformations compressives n’est connu, mais durant lequel, en revanche, on enregistre des manifestations de magmutisme de type intraplaque caractérisant une tectonique extensive et/ou décrochante. C’est durant cette période que l’on assiste à la suhsidence du bassin des flyschs à Ilelminthoïdes et que, conjointement, l’on enregistre les vitesses de surreetion les plus fortes des roches HP-UT métamorphisées durant le Crétacé supérieur; (3) un stade éocène à actuel, responsable de l’édification et de la déformation de l’édifice actuel se corré-lant avec la forte convergence Europe-Afrique qui s’enregistre depuis l’Eocène (collision tertiaire).  相似文献   
9.
The evolution of the atmospheric CO2 content is partly a response to the lack of balance between oceanic sedimentation and continental weathering, because the oceanic C reservoir tends to balance net inputs or losses from slow processes by rapid exchanges with the atmospheric reservoir. This response strongly depends on both amplitudes and time scales of the related processes. At Milankovitch or lower time scales, global models generally do neglect organic matter fossilisation, but such an assumption is only valid for oligotrophic systems. In eutrophic or mesotrophic systems, organic matter is not negligible and should be considered relatively to the carbonate sedimentation in order to know whether the impact of the sedimentation was a source or a sink for atmospheric CO2. To cite this article: P. Bertrand, C. R. Geoscience 334 (2002) 521–528.  相似文献   
10.
A Late Hauterivian interval (127.5 Ma), called the ‘Faraoni Event’, which is characterised by the deposition of deep-marine black shales in the Mediterranean Tethys, is demonstrably of sufficient geological brevity to be qualified as an anoxic event. This event lies within the Pseudothurmannia catulloi ammonite subzone, coincides with the extinction of the calcareous nannofossil species Lithraphidites bollii, and records an increase in a globular planktonic foraminifer. High quantities of marine organic matter were preserved in pelagic successions from northern and central Italy, Switzerland, southeastern France, southern Spain and probably elsewhere in the Mediterranean Tethys and Atlantic Ocean. Carbon-isotope stratigraphy from Tethyan and Atlantic sections shows a minor positive excursion in the uppermost part of the Hauterivian and Lowermost Barremian, suggesting accelerated extraction of organic carbon from the ocean reservoir just after the ‘Faraoni Event’. The duration of this short event is less than 100 ka according to cyclostratigraphy and coincides with a third-order sea-level rise. It is likely that similar forcing mechanisms responsible for global OAEs operated during this short time interval. To cite this article: F. Baudin, C. R. Geoscience 337 (2005).  相似文献   
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