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671.
Fung-Chun Li Jacques Angelier Rou-Fei Chen Hui-Ming Hsieh Benoît Deffontaines Ching-Ruey Luo Tso-Tchang Wu Ming-Chao Lin 《Comptes Rendus Geoscience》2005,337(13):1131-1139
We discuss the present-day sediment transport by rivers, and hence the erosion rate in upstream basins, based on the example of Taiwan Rivers where large datasets are available. After data correction, the values of the suspended sediment load in the lower Kaoping River are nearly three times smaller than those from the literature. On the other hand, we add the bed load evaluated from numerical modelling, despite limitations from data and models. Whereas the contribution of the chemical denudation rate in Taiwan is minor, the bed load is significant and must be evaluated. We point out that biases in data collection may favour high values of suspended load data, and that large series of datasets are needed to reduce uncertainties and smooth the time variability effect. To cite this article: F.-C. Li et al., C. R. Geoscience 337 (2005). 相似文献
672.
It has long been recognised that within zones of intense non-coaxial deformation, fold hinges may rotate progressively towards the transport direction ultimately resulting in highly curvilinear sheath folds. However, there is a surprising lack of detailed and systematic field analysis of such “evolving” sheath folds. This case study therefore focuses on the sequential development of cm-scale curvilinear folds in the greenschist-facies El Llimac shear zone, Cap de Creus, Spain. This simple shear-dominated dextral shear zone displays superb three dimensional exposures of sheath folds defined by mylonitic quartz bands within phyllonite. Increasing amounts of fold hinge curvature (δ) are marked by hinge segments rotating into sub-parallelism with the mineral lineation (Lm), whilst the acute angle between the axial-planar hinge girdle and foliation (ω) also displays a sequential reduction. Although Lm bisects the noses of sheath folds, it is also clearly folded and wrapped-around the sheath hinges. Lm typically preserves a larger angle (θ) with the fold hinge on the lower limb (L) compared to the upper (U) limb (θL > θU), suggesting that Lm failed to achieve a steady orientation on the lower limb. Adjacent sheath fold hinges forming fold pairs may display the same sense of hinge arcing to define synthetic curvature, or alternatively opposing directions of antithetic curvature. Such patterns reflect original buckle fold geometries coupled with the direction of shearing. The ratio of long/short fold limbs decreases with increasing hinge curvilinearity, indicating sheath folds developed via stretching of the short limb, rather than migrating or rolling hinge models. This study unequivocally demonstrates that both hinges of fold pairs become curvilinear with sheaths closing in the transport direction recording greater hinge-line curvilinearity compared to adjacent return hinges. This may provide a useful guide to bulk shear sense. 相似文献
673.
Michel Durand-Delga Manuel Esteras Silvia Gardin Hélène Paquet 《Comptes Rendus Geoscience》2005,337(9):849-860
The originality of the Malm–Cretaceous series of the Tariquides (Gibraltar arc), as compared to those of the Rifian–Betic ‘Dorsale’ (Alboran domain), and especially with the Penibetic (Iberia) domain, is emphasized. In the Los Pastores Group, near Algeciras, Upper Tithonian nodular limestones directly lie on the Dogger and are followed by Aptychus-bearing limestones (Late Berriasian to Barremian). In the Musa Group, Rif, radiolarites are followed by siliceous limestones (Kimmeridgian–Tithonian), then by karst and massflow breccias connected to a Berriasian tectonics, by Aptychus-bearing marly limestones, then by karst filled by Turonian limestones, and finally by Maastrichtian–Palaeocene polychrome pelites, whose micropalaeontological and mineral compositions (clay minerals, FeMn nodules) refer to a deep-sea, probably infra-CCD, sedimentation. To cite this article: M. Durand-Delga et al., C. R. Geoscience 337 (2005). 相似文献
674.
Settling velocity of diluted suspended aggregates is examined under steady-state conditions. It is shown that if the local settling velocity of the suspended mass of sediments at the bottom is gamma distributed, then, the vertical variation of the local mean settling velocity is proportional to a power of the local concentration C, where r is the gamma distribution parameter. That is a consequence of the suspended-sediment sorting produced by the vertical dynamics. The parameter r characterizes the range of settling velocity values for all the aggregates simultaneously in suspension. To cite this article: M. Sánchez et al., C. R. Geoscience 337 (2005). 相似文献
675.
The granite plutons of Vattamalai (VT), Gangaikondan (GK) and Pathanapuram (PT) intruding granulite facies rocks in southern India were emplaced during the Late Neoproterozoic tectonothermal event. Feldspar thermometry of mesoperthites from the granites yield temperatures of 800–1000?°C indicating high- to ultrahigh-temperature conditions, comparable to similar estimates derived from some of the host granulite facies rocks in the region. This study reports results from a detailed investigation of fluid inclusions in the three granite plutons. Carbonic inclusions characterize the major fluid species in all the cases and their unique abundance in some of these plutons indicates up to 1 wt.% CO2. In most of the cases, the inclusions show a near-pure CO2 composition as deduced from melting temperatures which cluster close to C, and as confirmed by laser Raman spectroscopy. The VT granite preserves the highest density CO2 fluids among all the three plutons with a density up to 0.912 g?cm?3 (molar volume of 48.25 cm3?mol?1). A combination of CO2 isochores, feldspar thermometry data and dehydration melting curves, and liquidus for water-undersaturated granitic systems clearly bring out a genetic link between these granites and granulitic lower crust. The ultimate origin of the CO2-rich fluids is linked to sub-lithospheric mantle sources through tectonic processes associated with the assembly of the Gondwana supercontinent. To cite this article: M. Santosh et al., C. R. Geoscience 337 (2005). 相似文献
676.
Ahmad Pouya 《Comptes Rendus Geoscience》2005,337(6):581-588
In an earlier paper, it has been shown that for a heterogeneous block of finite size, under linear boundary pressure conditions, a symmetric and positive definite tensor, denoted here by , exists, which relates the mean flux to the mean gradient of pressure in the block. In this paper, the conditions of constant boundary flux are first defined. Then it is shown that, under these conditions also, a symmetric and positive definite tensor, denoted , exists, which relates the mean flux to the mean pressure gradient. It is then shown that and respectively give the equivalent permeability in the direction of mean gradient and of mean flux. The directional permeability values given by are shown to be smaller than . To cite this article: A. Pouya, C. R. Geoscience 337 (2005). 相似文献
677.
Cédric Ménétrier Marcel Élie Luis Martinez Antoine Le Solleuz Jean-Robert Disnar Cécile Robin François Guillocheau Christophe Rigollet 《Comptes Rendus Geoscience》2005,337(15):1323-1330
The thermal history of the central part of the Paris basin is reconstructed using C31 hopane isomerisation ratios and organic matter transformation ratios measured on Lower Toarcian and Callovo-Oxfordian samples. Maximum burial palaeotemperatures range between 90 and 115?°C for the Toarcian shales, and between 75 and 95?°C for the Callovo-Oxfordian samples, from the East to the centre of the basin, respectively. The amount of Late Cretaceous erosion was evaluated to be between ca. 400 to 600 m in the eastern part of the studied area and 100 to 300 m in the centre of the basin. To cite this article: C. Ménétrier et al., C. R. Geoscience 337 (2005). 相似文献
678.
The onset of exhumation of the Canigou massif, related to the reactivation of the Têt Fault during the Gulf of Lion opening, is dated at 26–27 Ma, using apatite fission track method and lasts until the Aquitanian, at a rate of . The subsequent evolution is necessarily followed by a slower rate of exhumation to account for total exhumation. At the hanging-wall of this fault, the granite of Mont-Louis records an older exhumation history, where the crossing of the 110 °C isotherm at 40±4 Ma is related to the Pyrenean thrusting. To cite this article: O. Maurel et al., C. R. Geoscience 334 (2002) 941–948. 相似文献
679.
This paper reports on an observation of the appulse of (146) Lucina with AGK3 + 17° 1309 made on April 18, 1982, at the Meudon Observatory in France. During this observation a secondary event occurred and was recorded. A Nocticon camera mounted on the 1-m telescope and video equipment was used. This equipment is well adapted to these observations primarily because astrometric and photometric reductions are possible. Furthermore no diaphragm is necessary in contrast to classical photometry, and this reduces the possibility of generating artifacts. The Meudon observation is described. Observational data from other sites have been collected, and have confirmed that the short extinction observed at Meudon was not due to the asteroid itself. A possible interpretation is the existence of a faint satellite in the neighborhood of (146) Lucina. The observation leads to a diameter of at least 5.7 km and a projected distance of 1600 km from the primary. 相似文献
680.
Gabriel Godin 《Estuarine, Coastal and Shelf Science》1984,19(4):451-461
A comparison is made between a set of current measurements in a section across the Strait of Juan de Fuca and those recorded further upstream at Race Rocks at a single depth. No outstanding common qualitative features are noted. Cross spectra reveal a low correlation for the subtidal current and suggest an intensification of the diurnal modulation of the flow at Race Rocks. The high correlation in the tidal bands allows to calculate this portion of the tidal current at Race Rocks which is coherent with the one sensed across the section. 相似文献