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101.
There are many examples of “local” discourses aiming to delegitimize environmental issues, demands, actions and governance by arguing that they pursue international goals, defined by international actors that do not meet local needs and frequently oppose them. We focus on the narrative held by large ranchers in the Eastern Amazon, which disqualifies the so-called top-down creation of protected areas that jeopardizes the “local development” these actors have, following the narrative, encouraged and sustained for years. Through the combination of an ontological and constructivist approach of scales, our contribution challenges this scalar construction questioning the “locality” of the large ranchers and showing that their role as “local developers” is actually rooted in regional/national/international scales. We then study the most important effect of the anti-environmental grand scalar narrative: its influence on regional and national decision makers. Well-conceived and publicized scalar scenarios are efficient in this context as in many others. 相似文献
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Cenomanian paralic deposits of Charentes (southwestern France) have yielded abundant vertebrate microremains, including rather diversified continental taxa (e.g., frogs, turtles, crocodilians, dinosaurs, pterosaurs, lizards, and mammals). In this short report, the succession of faunal assemblages observed is briefly described in relation to palaeoenvironmental change resulting from the Cenomanian-early Turonian transgressive episode. Continental forms occur commonly in estuarine and shallow marine rocks of the lower part of the Cenomanian stage, but seem to be lacking in younger strata deposited in more open marine settings. Among an unexpected biodiversity, several non-marine groups (e.g., ziphodont crocodilians, carcharodontosaurid and troodontid dinosaurs, marsupial-like mammals) are recorded for the first time in the lower Upper Cretaceous of Europe, thus providing new palaeobiogeographical indications for this poorly documented part of the world. 相似文献
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Accurate and High-Precision Measurement of Lithium Isotopes in Two Reference Materials by MC-ICP-MS 总被引：5，自引：1，他引：5
Romain Millot Catherine Guerrot Nathalie Vigier 《Geostandards and Geoanalytical Research》2004,28(1):153-159
We report here a newly developed method for measurement of Li isotopes by use of multi-collector ICP-MS (Neptune) allowing rapid and high precision determination of Li isotope ratios at low levels of lithium (15–20 ng). The lithium reference sample solution IRMM-016 was analysed over a period of ten months with an external reproducibility of 0.24% (2s, n = 52). Chemical separation of Li from matrix was performed on the seawater sample IRMM BCR-403, for which a mean δ7 Li value of + 31.0 ± 0.1 % (2s/√n, n = 31) was obtained. This mean value is in good agreement with those previously published for other seawater samples. BCR-403 seawater being readily available, we propose that this seawater sample be used as a reference sample for Li isotope measurements. 相似文献
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Briançonnais units are squeezed between two Mesozoic eclogitic belts (Piemont-Ligurian ocean and Valaisan ocean) along the ECORS-CROP seismic line in the Italian-French Western Alps (France, Italy). The metamorphic evolution of this area plays a key role for understanding the evolution of the Western Alps and is discussed on the basis of detailed petrographic investigations carried out on weathered sediments issued from the erosion of the Hercynian belt, especially on lower Permian to Mesozoic sediments. In the Zone Houillère, as well in the Permo-Triassic cover of the Briançonnais basement, the index metamorphic mineral assemblage is mainly composed of white micas with varying chemical composition, chloritoid and garnet. This same assemblage occurs within different lithologies (metaarkose, metapelite, metasandstone). Consequently, equilibrium phase diagrams were computed for different whole rock compositions using DOMINO software. The results of the P-T investigations clearly show that each unit underwent a different sequence of metamorphic reactions. An increase in metamorphic grade from greenschist facies conditions in the Northwest (Zone Houillère) to the transition between blueschist and eclogite facies conditions in the Southeast (Internal Briançonnais) is observed. A major discontinuity in metamorphic grade is located at the contact between Zone Houillère and Ruitor unit, as documented by a pressure gap of ~ 7 kbar. In general, the observed metamorphic field gradient is inverted and is interpreted to represent different depths of burial during subduction, which correlates with the paleogeographic position of the different units. 相似文献
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Interaction of an antecedent fluvial system with early normal fault growth: Implications for syn‐rift stratigraphy,western Corinth rift (Greece) 
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下载免费PDF全文 Continental ‘overfilled’ conditions during rift initiation are conventionally explained as due to low creation of accommodation compared with sediment supply. Alternatively, sediment supply can be relatively high from the onset of rifting due to an antecedent drainage system. The alluvial Lower Group of the western Plio–Pleistocene Corinth rift is used to investigate the interaction of fluvial sedimentation with early rifting. This rift was obliquely superimposed on the Hellenide mountain belt from which it inherited a significant palaeorelief. Detailed sedimentary logging and mapping of the well‐exposed syn‐rift succession document the facies distributions, palaeocurrents and stratigraphic architecture. Magnetostratigraphy and biostratigraphy are used to date and correlate the alluvial succession across and between fault blocks. From 3·2 to 1·8 Ma, a transverse low sinuosity braided river system flowed north/north‐east to east across east–west‐striking active fault blocks (4 to 7 km in width). Deposits evolved downstream from coarse alluvial conglomerates to fine‐grained lacustrine deposits over 15 to 30 km. The length scale of facies belts is much greater than, and thus not directly controlled by, the width of the fault blocks. At its termination, the distributive river system built small, stacked deltas into a shallow lake margin. The presence of a major antecedent drainage system is supported by: (i) a single major sediment entry point; (ii) persistence of a main channel belt axis; (iii) downstream fining at the scale of the rift basin. The zones of maximum subsidence on individual faults are aligned with the persistent fluvial axis, suggesting that sediment supply influenced normal fault growth. Instead of low accommodation rate during the early rift phase, this study proposes that facies progradation can be controlled by continuous and high sediment supply from antecedent rivers. 相似文献
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Gelare Moradi Bart Vermeulen Colin D. Rennie Romain Cardot Stuart N. Lane 《地球表面变化过程与地形》2019,44(14):2903-2921
Secondary circulation in river confluences results in a spatial and temporal variation of fluid motion and a relatively high level of morphodynamic change. Acoustic Doppler current profiler (aDcp) vessel-mounted flow measurements are now commonly used to quantify such circulation in shallow water fluvial environments. It is well established that such quantification using vessel-mounted aDcps requires repeated survey of the same cross-section. However, less attention has been given to how to process these data. Most aDcp data processing techniques make the assumption of homogeneity between the measured radial components of velocity. As acoustic beams diverge with distance from the aDcp probe, the volume of the flow that must be assumed to be homogeneous between the beams increases. In the presence of secondary circulation cells, and where there are strong rates of shear in the flow, the homogeneity assumption may not apply, especially deeper in the water column and close to the bed. To reduce dependence on this assumption, we apply a newly-established method to aDcp data obtained for two medium-sized (~60–80 m wide) gravel-bed river confluences and compare the results with those from more conventional data processing approaches. The comparison confirms that in the presence of strong shear our method produces different results to more conventional approaches. In the absence of a third set of fully independent data, we cannot demonstrate conclusively which method is best, but our method involves less averaging and so in the presence of strong shear is likely to be more reliable. We conclude that it is wise to apply both our method and more conventional methods to identify where data analysis might be impacted upon by strong shear and where inferences of secondary circulation may need to be made more cautiously. © 2019 John Wiley & Sons, Ltd. 相似文献
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Belmadani Ali Dalphinet Alice Chauvin Fabrice Pilon Romain Palany Philippe 《Climate Dynamics》2021,56(11):3687-3708
Tropical cyclones are a major hazard for numerous countries surrounding the tropical-to-subtropical North Atlantic sub-basin including the Caribbean Sea and Gulf of Mexico. Their intense winds, which can exceed 300 km h−1, can cause serious damage, particularly along coastlines where the combined action of waves, currents and low atmospheric pressure leads to storm surge and coastal flooding. This work presents future projections of North Atlantic tropical cyclone-related wave climate. A new configuration of the ARPEGE-Climat global atmospheric model on a stretched grid reaching ~ 14 km resolution to the north-east of the eastern Caribbean is able to reproduce the distribution of tropical cyclone winds, including Category 5 hurricanes. Historical (1984–2013, 5 members) and future (2051–2080, 5 members) simulations with the IPCC RCP8.5 scenario are used to drive the MFWAM (Météo-France Wave Action Model) spectral wave model over the Atlantic basin during the hurricane season. An intermediate 50-km resolution grid is used to propagate mid-latitude swells into a higher 10-km resolution grid over the tropical cyclone main development region. Wave model performance is evaluated over the historical period with the ERA5 reanalysis and satellite altimetry data. Future projections exhibit a modest but widespread reduction in seasonal mean wave heights in response to weakening subtropical anticyclone, yet marked increases in tropical cyclone-related wind sea and extreme wave heights within a large region extending from the African coasts to the North American continent.
相似文献109.
Estelle Leroux Daniel Aslanian Marina Rabineau Romain Pellen Maryline Moulin 《地学学报》2018,30(3):207-214
A review of geological and geophysical observations points towards a worldwide kinematic change at around 6 Ma. The synchronicity of many manifestations (tectonics, magmatism, kinematics, ecological events, among others) at ~6 Ma, similar to those recognized from time to time on the geological time‐scale, argues for a global geodynamic event that has led to many regional consequences on Earth's surface. In particular, we propose that this global event was the main trigger for the three fold increase in sediment deposits in the world ocean over the last ~5 Ma, but also for the onset of the Messinian Salinity Crisis in the Mediterranean area, one of the most severe ecological crises in the Earth's history. We suggest this Messinian revolution to be the last occurrence of cyclic successions of global events. 相似文献
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Talc + olivine in metaperidotites result from the serpentinite breakdown due to increasing temperature in the Bergell contact aureole. Jack‐straw olivine textures are present in close proximity to the serpentine breakdown reaction. As the intrusion is approached, the number of olivine crystals increases while the size of the crystals decreases; this feature documents increased overstepping with increased heating rates. Talc veinlets are observed in the outer parts of the talc–olivine zone and are interpreted to be pathways of fluid produced during devolatilization of serpentine. None of the talc–olivine oxygen isotope pairs analysed are in isotopic equilibrium with respect to the peak contact temperature. This implies that escaping fluids cannot be in equilibrium with both phases. Hence, the fluid produced by serpentine reaction does not directly reflect the protolith composition, and attention must be given to the reaction mechanism before interpreting fluid isotope composition. 相似文献