Chemostratigraphic correlation of Barremian and lower Aptian ammonite zones and magnetic reversals     

Lukas Wissler  Helmut Weissert  Jean-Pierre Masse  Luc Bulot 《International Journal of Earth Sciences》2002,91(2):272-279

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Compartmentalization of physical and chemical properties in hard-rock aquifers deduced from chemical and groundwater age analyses     

Virginie Ayraud  Luc Aquilina  Thierry Labasque  Hélène Pauwels  Jérôme Molenat  Anne-Catherine Pierson-Wickmann  Véronique Durand  Olivier Bour  Corinne Tarits  Pierre Le Corre  Elise Fourre  Philippe Merot  Philippe Davy 《Applied Geochemistry》2008

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Diffusion of iodide and iodate through Opalinus Clay: Monitoring of the redox state using an anion chromatographic technique   总被引：1，自引：0，他引：1  

Martin A. Glaus  Werner Müller  Luc R. Van Loon 《Applied Geochemistry》2008,23(12):3612-3619

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Seasonal Variations in Drag Coefficient over a Sastrugi-Covered Snowfield in Coastal East Antarctica     

Charles Amory  Hubert Gallée  Florence Naaim-Bouvet  Vincent Favier  Etienne Vignon  Ghislain Picard  Alexandre Trouvilliez  Luc Piard  Christophe Genthon  Hervé Bellot 《Boundary-Layer Meteorology》2017,164(1):107-133

The surface of windy Antarctic snowfields is subject to drifting snow, which leads to the formation of sastrugi. In turn, sastrugi contribute to the drag exerted by the snow surface on the atmosphere and hence influence drifting snow. Although the surface drag over rough sastrugi fields has been estimated for individual locations in Antarctica, its variation over time and with respect to drifting snow has received little attention. Using year-round data from a meteorological mast, seasonal variations in the neutral drag coefficient at a height of 10 m \((C_{{ DN}10})\) in coastal Adelie Land are presented and discussed in light of the formation and behaviour of sastrugi based on observed aeolian erosion patterns. The measurements revealed high \(C_{{ DN}10} \) values \((\ge \) 2 \(\times \) 10\(^{-3})\) and limited drifting snow (35% of the time) in summer (December–February) versus lower \(C_{{ DN}10} \) values \((\approx \) 1.5 \(\times \) \(10^{-3})\) associated with more frequent drifting snow (70% of the time) in winter (March–November). Without the seasonal distinction, there was no clear dependence of \(C_{{ DN}10} \) on friction velocity or wind direction, but observations revealed a general increase in \(C_{{ DN}10} \) with rising air temperature. The main hypothesis defended here is that higher temperatures increase snow cohesion and the development of sastrugi just after snow deposition while inhibiting the sastrugi streamlining process by raising the erosion threshold. This increases the contribution of the sastrugi form drag to the total surface drag in summer when winds are lighter and more variable. The analysis also showed that, in the absence of erosion, single snowfall events can reduce \(C_{{ DN}10} \) to \(1\,\times \,10^{-3}\) due to the burying of pre-existing microrelief under newly deposited snow. The results suggest that polar atmospheric models should account for spatial and temporal variations in snow surface roughness through a dynamic representation of the sastrugi form drag.  相似文献   

Regional modeling of climate change impacts on smallholder agriculture and ecosystems in Central America     

Lee Hannah  Camila I. Donatti  Celia A. Harvey  Eric Alfaro  Daniel Andres Rodriguez  Claudia Bouroncle  Edwin Castellanos  Freddy Diaz  Emily Fung  Hugo G. Hidalgo  Pablo Imbach  Peter Läderach  Jason P. Landrum  Ana Lucía Solano 《Climatic change》2017,141(1):29-45

Climate change will have serious repercussions for agriculture, ecosystems, and farmer livelihoods in Central America. Smallholder farmers are particularly vulnerable due to their reliance on agriculture and ecosystem services for their livelihoods. There is an urgent need to develop national and local adaptation responses to reduce these impacts, yet evidence from historical climate change is fragmentary. Modeling efforts help bridge this gap. Here, we review the past decade of research on agricultural and ecological climate change impact models for Central America. The results of this review provide insights into the expected impacts of climate change and suggest policy actions that can help minimize these impacts. Modeling indicates future climate-driven changes, often declines, in suitability for Central American crops. Declines in suitability for coffee, a central crop in the regional economy, are noteworthy. Ecosystem models suggest that climate-driven changes are likely at low- and high-elevation montane forest transitions. Modeling of vulnerability suggests that smallholders in many parts of the region have one or more vulnerability factors that put them at risk. Initial adaptation policies can be guided by these existing modeling results. At the same time, improved modeling is being developed that will allow policy action specifically targeted to vulnerable groups, crops, and locations. We suggest that more robust modeling of ecological responses to climate change, improved representation of the region in climate models, and simulation of climate influences on crop yields and diseases (especially coffee leaf rust) are key priorities for future research.  相似文献   

Quantitative spectroscopy of Wolf–Rayet stars in HD 97950 and R136a — the cores of giant H ii regions     

P. A. Crowther  & Luc Dessart 《Monthly notices of the Royal Astronomical Society》1998,296(3):622-642

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Is a management framework based on spawning-stock biomass indicators sustainable? A viability approach     

De Lara  Michel; Doyen  Luc; Guilbaud  Therese; Rochet  Marie-Joelle 《ICES Journal of Marine Science》2007,64(4):761-767

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High-yielding aquifers in crystalline basement: insights about the role of fault zones,exemplified by Armorican Massif,France     

Clément Roques  Olivier Bour  Luc Aquilina  Benoît Dewandel 《Hydrogeology Journal》2016,24(8):2157-2170

While groundwater constitutes a crucial resource in many crystalline-rock regions worldwide, well-yield conditions are highly variable and barely understood. Nevertheless, it is well known that fault zones may have the capacity to ensure sustainable yield in crystalline media, but there are only a few and disparate examples in the literature that describe high-yield conditions related to fault zones in crystalline rock basements. By investigating structural and hydraulic properties of remarkable yielding sites identified in the Armorican Massif, western France, this study discusses the main factors that may explain such exceptional hydrogeological properties. Twenty-three sites, identified through analysis of databases available for the region, are investigated. Results show that: (1) the highly transmissive fractures are related to fault zones which ensure the main water inflow in the pumped wells; (2) the probability of intersecting such transmissive fault zones does not vary significantly with depth, at least within the range investigated in this study (0–200 m); and (3) high yield is mainly controlled by the structural features of the fault zones, in particular the fault dip and the presence of a connected storage reservoir. Conceptual models that summarize the hydrological properties of high-yield groundwater resources related to fault zones in crystalline basement are shown and discussed.  相似文献   

Tectonic and structural evolution of Gough volcano: A volcanological model     

Luc Chevallier 《Journal of Volcanology and Geothermal Research》1987,33(4)

Morphostructural, stratigraphic and tectonic data indicate that the evolution of Gough volcano is similar to other oceanic intraplate volcanoes, is older than 1 Ma, and is related to a transform fault. At least six evolutionary stages can be distinguished within two major magmatostructural periods dominated by basaltic and trachytic magmas, respectively.The basaltic shield volcano is characterized by a curved, elongated shape in plan and a rift zone with a high density of dykes, combined with a radial intrusive system. The latter is interpreted as being fed by a magma chamber some 4 km below the surface. The activity of the volcano became more centralized at the end of the basaltic period and its slopes became steeper. This corresponds to the development of a shallower and narrower central conduit in the edifice. The basaltic period was terminated by formation of a shield caldera related to the 4 km deep magma chamber. The term “shield caldera” is used for a collapse structure that is postmagmatic, large in comparison with the diameter of the volcano, and delimited by normal faults that do not show a closed circular pattern but rather a series of arcs. In contrast, summit calderas are defined as smaller, circular-shaped, centrally situated, synmagmatic features, related to a central shallow column. During the basaltic period, landslides were generated on the flanks of the edifice as a result of slope stability factors which are not easy to determine at present, and dynamic factors among which the intrusion of magma along a curved zone certainly played a major role.The trachytic period is characterized by comparatively rare pyroclastic deposits and a large volume of thick flows extruded from domes. These extrusions, as well as plugs, formed from vertical cylindrical columns of magma rising from shallow individual magma pockets fed by the main reservoir.  相似文献   

Premetamorphic lateritisation in Proterozoic metabasites of Rogaland,SW Norway   总被引：1，自引：0，他引：1  

Luc C. G. M. Bol  Cornelis Maijer  J. Ben H. Jansen 《Contributions to Mineralogy and Petrology》1989,103(3):306-316

Heterogeneous layers of granulite facies metamorphic basites of the Proterozoic supracrustal Faurefjell Formation in Rogaland, S.W. Norway, display an extreme chemical variation. Within a single layer the bulk chemical composition gradually changes from approximately basaltic in basic granulites to alumina-iron-rich in granofelses. Component-ratios and composition-volume relations indicate open-system chemical reactions mainly involving the extraction of silica. Apparent enrichment in Fe, Ti, P, Al, Zr, Ni, Co, Zn, Y, Nb, Hf and REE and variations in resulting metamorphic mineral assemblages are related to premetamorphic progressive lateritisation of a basaltic protolith. The weathering generated a continuous chemical suite from SiO₂=48 wt%, Fe₂O₃=10 wt% and Al₂O₃=19 wt% in the basic granulites to 14 wt%, 40 wt% and 25 wt% in the Fe-Al granofelses. Metasomatism during diagenesis and during (very) high-grade metamorphism (1200–900 Ma) further perturbed the concentrations of relatively mobile elements Ca, Mg, K, Rb, Sr, Ba, Na and Li in the laterites without affecting the transition metal ratios. In particular, the REE did not fractionate differentially during the supracrustal and metasomatic alteration.  相似文献