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51.
Cordrie Louise Gailler Audrey Escartin Javier Feuillet Nathalie Heinrich Philippe 《Natural Hazards》2020,103(2):2103-2129
Natural Hazards - The arc of the Lesser Antilles is associated with a significant tectonic activity due to the subduction of the Atlantic oceanic plate under the Caribbean plate. Earthquakes in... 相似文献
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Alexandra Baeta Rute Pinto Ivan Valiela Pierre Richard Nathalie Niquil João C. Marques 《Marine environmental research》2009,67(3):109-116
Assessments of temporal variation in stable carbon and nitrogen ratios were used to examine seasonal trends of the water column and benthic food webs in the Mondego estuary (Portugal). There was a marked seasonality in weather and water column conditions, including nutrient supply and chlorophyll concentrations. In spite of the pronounced environmental changes, we found little evidence of seasonal variation in δ13C and δ15N of producers and consumers in the Mondego estuary, with a few notable exceptions. Nitrogen isotope ratios in macrophytes (Zostera noltii, Ulva sp., Enteromorpha sp., and Gracilaria sp.), and in two grazers (Idotea chelipes and Lekanesphaera levii) increased during late summer, with the highest δ15N values being measured in July, during a period of elevated temperatures and drought, which may have favored high rates of denitrification and heavier δ15N values. The results suggest that stable-isotope values from macrophytes and selected grazers are useful as tracers of seasonal changes in nitrogen inputs into estuaries, and that those of consumers reflect other factors beyond seasonal variations in N and C sources. 相似文献
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Marc-André Gutscher Stephane Dominguez Graham K. Westbrook Pascal Gente Nathalie Babonneau Thierry Mulder Eliane Gonthier Rafael Bartolome Joaquim Luis Filipe Rosas Pedro Terrinha 《Marine and Petroleum Geology》2009,26(5):647-659
The Gulf of Cadiz lies astride the complex plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. We report on the results of recent bathymetric swathmapping and multi-channel seismic surveys carried out here. The seafloor is marked by contrasting morphological provinces, spanning the SW Iberian and NW Moroccan continental margins, abyssal plains and an elongate, arcuate, accretionary wedge. A wide variety of tectonic and gravitational processes appear to have shaped these structures. Active compressional deformation of the wedge is suggested by folding and thrusting of the frontal sedimentary layers as well as basal duplexing in deeper internal units. There is evidence for simultaneous gravitational spreading occurring upslope. The very shallow mean surface and basal slopes of the accretionary wedge (1° each) indicate a very weak decollement layer, geometrically similar to the Mediterranean Ridge accretionary complex. Locally steep slopes (up to 10°) indicate strongly focused, active deformation and potential gravitational instabilities. The unusual surface morphology of the upper accretionary wedge includes “raft-tectonics” type fissures and abundant sub-circular depressions. Dissolution and/or diapiric processes are proposed to be involved in the formation of these depressions. 相似文献
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Francesca Sangiorgi Lucilla Capotondi Nathalie Combourieu Nebout Luigi Vigliotti Henk Brinkhuis Simona Giunta Andr F. Lotter Caterina Morigi Alessandra Negri Gert‐Jan Reichart 《第四纪科学杂志》2003,18(8):723-732
Holocene cooling events have been reconstructed for the southern Adriatic Sea (central Mediterranean) by means of analyses of organic walled dinoflagellate cysts, planktonic foraminifera, oxygen isotopes, calcareous nanoplankton, alkenones and pollen from a sediment core. Two cooling events have been detected, during which sea‐surface temperatures (SSTs) were ca. 2°C lower. Unravelling the SST signal into dominant seasonal components suggests maximum winter cooling of 2°C at around 6.0 ka, whereas the cooling at ca. 3.0 ka might be the result of a spring temperature cooling of 2–3°C. The events, lasting several hundred years, are apparently synchronous with those in the Aegean Sea, where they have been related to known cooling events from the Greenland ice‐core record. A distinct interruption in Adriatic Sea sapropel S1 is not clearly accompanied by a local drop in winter temperatures, but seems to be forced by ventilation, which probably occurred earlier in the Aegean Sea and was subsequently transmitted to the Adriatic Sea. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
55.
Jean Carignan Nathalie Vigier Romain Millot 《Geostandards and Geoanalytical Research》2007,31(1):7-12
The CRPG (Nancy, France) has prepared secondary reference materials for Li isotope measurements by mixing 7 Li or 6 Li spikes and either L-SVEC or IRMM-016 certified reference materials to produce solutions having a known Li concentration and isotopic composition. The Li7-N and Li6-N solution samples (1.5 mol l−1 HNO3 ) have nominal δ7 Li isotopic compositions of 30.1‰ and -9.7‰ respectively relative to L-SVEC and concentrations of 100 mg l−1 . Repeated measurement of these samples using the QUAD-ICP-MS at the CRPG yielded δ7 Li of 30.4 ± 1.1‰ (n = 13) and -8.9 ± 0.9‰ (n = 9) at the 2s level of confidence. An additional LiCl-N solution was measured and yielded a delta value of 9.5 ± 0.6‰ (n = 3). Identical results were obtained at the BRGM (Orléans, France) from determinations performed with a Neptune MC-ICP-MS (30.2 ± 0.3‰, n = 89 for the Li7-N, -8.0 ± 0.3‰, n = 38 for the Li6-N and 10.1 ± 0.2‰, n = 46 for LiCl-N at the 2s level of confidence). The deviation of measured composition relative to the nominal value for the Li6-N solution might be explained by either contamination during preparation or an error during sample weighing. These secondary reference materials, previously passed through ion exchange resin or directly analysed, may be used for checking the accuracy of Li isotopic measurements over a range of almost 40‰ and will be available to the scientific community upon request to J. Carignan or N. Vigier, CRPG. 相似文献
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Pierre Agrinier Nathalie Jendrzejewski 《Contributions to Mineralogy and Petrology》2000,139(3):265-272
The Beer–Lambert law is traditionally used to determine water and carbon concentrations in glasses from their infrared (IR)
spectra. In practice, this method requires estimation of the thickness and density of the glass as well as the calibration
of the molecular absorptivities of the species concerned. All of these parameters can be sources of practical difficulties
and analytical uncertainty. These weaknesses in the application of the Beer–Lambert law have been overcome by an empirical
analysis of the infrared spectra. Using a set of 292 spectra obtained on 113 natural and experimental tholeiitic glasses (SiO2 48.5–51 wt%; water contents 0–4000 ppm H2O), it can be shown that the thickness–density (ρ d) product of a glass sample can be directly and reliably inferred from
its IR spectrum. This allows the Beer–Lambert law to be rewritten. The new form no longer requires thickness or density estimations
to determine volatile contents. Moreover, if needed, the thickness of the glass slab can also be accurately determined from
the IR spectra. This new method is developed for quantitative determination of water concentrations in MORB glasses but can
also be applied to any minor species (carbon, sulfur, etc.) provided it is active in the IR domain and that a suitable independent
frequency of IR absorption can be identified. Precision is about 60 ppm H2O on O–H− contents. This method, tested on natural and experimental MORB-type glasses, can be applied to any chemical composition provided
a set of reference spectra is available.
Received: 16 September 1999 / Accepted: 18 February 2000 相似文献
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