Late Glacial-Holocene sequence of Lake Saint-Point (Jura Mountains, France): Detrital inputs as records of climate change and anthropic impact     

Aurlie Leroux  Vincent Bichet  Anne-Vronique Walter-Simonnet  Michel Magny  Thierry Adatte  milie Gauthier  Herv Richard  Agns Baltzer 《Comptes Rendus Geoscience》2008,340(12):883-892

A sediment sequence (SP05, 12.5 m long) was taken from the deep zone of Lake Saint-Point (850 m a.s.l.). Sedimentological analyses highlight two main contrasted periods of sedimentation: the Last Glacial Maximum (LGM)/Late Glacial characterized by high silicates and quartz contents the Holocene dominated by the carbonated fraction. At the beginning of the Holocene (11 400 years cal. BP), silicates fraction flux abruptly decreased. The shift between the Late Glacial and the Holocene periods may be explained by forest development in the catchment. From 10 200 to 6800 years cal. BP, silicates and detrital carbonate fractions remained stable before they progressively increased steady till 5000 years cal. BP. Both increases cannot be totally attributed to an anthropic impact since pollen data indicate continuous anthropic activities only dated back from 3000 years cal. BP. They thus resulted from a dominant climatic control. From 5000 years cal. BP, silicates content still increased while detrital carbonates input became steady due to a change in pedogenetic processes affecting the catchment. During the last millennium, silicates and detrital carbonate decreased, probably due to pastureland development.  相似文献   

The stability of dipolar gyres on a beta-plane     

Steven Herbette  Antoine Hochet  Thierry Huck  Alain Colin de Verdière  Jérémy Collin  Frank Shillington 《地球物理与天体物理流体动力学》2014,108(5):479-502

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Impacts of post‐glacial rebound on landslide spatial distribution at a regional scale in northern Iceland (Skagafjörður)          下载免费PDF全文

Etienne Cossart  Denis Mercier  Armelle Decaulne  Thierry Feuillet  Helgi Páll Jónsson  Þorsteinn Sæmundsson 《地球表面变化过程与地形》2014,39(3):336-350

In de‐glaciated areas, para‐glaciation (i.e. the conditioning of landscapes by prior glaciation) has often been considered a major predisposing factor in landslide occurrence; its consequences have been particularly well identified at a fine scale (especially on bedrock jointing). Hitherto, the relative impacts of para‐glaciation on hillslope dynamics at a regional scale had nevertheless not been quantified statistically. We examine Skagafjörður area (northern Iceland) where landslides are widespread (at least 108 were mapped in an area of c. 3000 km²). We compare the role of para‐glaciation (debuttressing, influence of post‐glacial rebound) with that of classic factors (topography, lithology, etc.) in landslide occurrence and location, using a spatial analysis based on a chi‐square test. On the one hand, the results highlight that landslides are over‐represented in areas where post‐glacial rebound was at its maximum, with a stronger concentration of landslides in the northern part of the fjord. On the other hand, the distribution of landslides did not show any clear relationship with the pattern of glacial debuttressing. Tschuprow coefficient highlights that the influence of post‐glacial rebound on landslide location is higher than the combined influence of slope gradient, curvature or geological structure. This result is supported by our initial evidence for the timing of landslides in the area: most landslides occurred during the first half of the Holocene, and a period of hillslope instability was initiated when the post‐glacial uplift was at its maximum. Finally, the mechanisms that link post‐glacial rebound and landsliding as well as the geomorphic impacts of landslides, are discussed. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Stable isotopes reveal food web modifications along the upstream–downstream gradient of a temperate stream     

Nicolas Hette-Tronquart  Jérôme Belliard  Evelyne Tales  Thierry Oberdorff 《Aquatic Sciences - Research Across Boundaries》2016,78(2):255-265

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Measuring the ecological integrity of an industrial district in the Amazon estuary, Brazil     

Viana AP  Frédou FL  Frédou T 《Marine pollution bulletin》2012,64(3):489-499

The aim of the present study is to provide information on the ecological integrity of an industrial district located in the estuary of Pará River (Amazon estuary), by applying a selection of fish based multimetric indices of ecosystem integrity: Abundance Biomass Comparation (ABC); Biological Health Index; Estuarine Fish Community, Transitional Fish Classification and Estuarine Biotic Integrity Indexes. To evaluate the impacts of the industrial area and cargo terminal, three areas were considered: Zone 1, (maximum impact), Zone 2 (median risk) and Zone 3 (reference area). All the biological indices used were considered to be excellent indicators of the ecological integrity of the different sectors of the study area and were especially effective for the demonstration of the critical alterations of the fish community of Zone 1 and Zone 2. The simultaneous use of different indices family, with different assumptions, did strengthen the results enhancing the confidence in the diagnostic.  相似文献   

Twenty years of Belgian North Sea aerial surveillance: a quantitative analysis of results confirms effectiveness of international oil pollution legislation     

Lagring R  Degraer S  de Montpellier G  Jacques T  Van Roy W  Schallier R 《Marine pollution bulletin》2012,64(3):644-652

Over the years many policy measures have been taken to prevent illegal oil discharges from ships, like the MARPOL 73/78 Convention (1983) and the Bonn Agreement (1969/1983). However, the number of discharges remained high, leading to chronic oiling of seabirds and sensitive coastlines, therefore further measures were taken. The aim of this study is to quantify the effectiveness of two key legislative regulations: the IMO-designation of the North Sea as MARPOL Special Area which took effect in 1999, and the adoption of the EU Directive on Port Reception Facilities in 2000. Under study is the heavily navigated Belgian Surveillance Area, monitored since 1991, characterised by shallow waters with ecologically important sandbanks. The aerial surveillance data from 1991 to 2010 show a stepwise decrease in ship-source oil pollution. Three time periods can be distinguished with two turning points coinciding with the actual implementation of these key legislative measures, confirming their effectiveness.  相似文献   

Use of a Sodar to Improve the Forecast of Fogs and Low Clouds on Airports     

Alain Dabas  Samuel Remy  Thierry Bergot 《Pure and Applied Geophysics》2012,169(5-6):769-781

A sodar was deployed at Roissy–Charles de Gaulle airport near Paris, France, in 2008 with the aim of improving the forecast of low visibility conditions there. During the winter of 2008–2009, an experiment was conducted that showed that the sodar can effectively detect and locate the top of fog layers which is signaled by a strong peak of acoustic reflectivity. The peak is generated by turbulence activity in the inversion layer that contrasts sharply with the low reflectivity recorded in the fog layer below. A specific version of the 1D-forecast model deployed at Roissy for low visibility conditions (COBEL-ISBA) was developed in which fogs’ thicknesses are initialized by the sodar measurements rather than the information derived from the down-welling IR fluxes observed on the site. It was tested on data archived during the winters of 2008–2009 and 2009–2010 and compared to the version of the model presently operational. The results show a significant improvement—dissipation times of fogs are better predicted.  相似文献   

Contour current imprints and contourite drifts in the Bahamian archipelago     

Thierry Mulder  Emmanuelle Ducassou  Vincent Hanquiez  Mlanie Principaud  Kelly Fauquembergue  Elsa Tournadour  Ludivine Chabaud  John Reijmer  Audrey Recouvreur  Herv Gillet  Jean Borgomano  Anais Schmitt  Paul Moal 《Sedimentology》2019,66(4):1192-1221

New data collected along the slopes of Little and Great Bahama Bank and the abyssal plain of the Bahama Escarpment provides new insights about contour current‐related erosive structures and associated deposits. The Bahamian slope shows abundant evidence of bottom current activity such as furrows, comet‐like structures, sediment waves and drifts. At a seismic scale, large erosion surfaces and main periods of drift growth resulted from current acceleration related to plate tectonic processes and progressive opening and closure of gateways and long‐term palaeoclimate evolution. At present‐day, erosion features and contourite drifts are either related to relatively shallow currents (<1000 m water depth) or to deep currents (>2500 m water depth). It appears that the carbonate nature of the drifts does not impact the drift morphology at the resolution addressed in the present study. Classical drift morphologies defined in siliciclastic environments are found, such as mounded, plastered and separated drifts. In core, contourite sequences show a bi‐gradational trend that resembles classical contourite sequences in siliciclastic deposits showing a direct relationship with a change in current velocity at the sea floor. However, in a carbonate system the peak in grain size is associated with increased winnowing rather than increased sediment supply as in siliciclastic environments. In addition, the carbonate contourite sequence is usually thinner than in siliciclastics because of lower sediment supply rates. Little Bahama Bank and Great Bahama Bank contourites contain open‐ocean input and slope‐derived debris from glacial episodes. Inner platform, platform edge and open ocean pelagic input characterize the classical periplatform ooze during interglacials. In all studied examples, the drift composition depends on the sea floor topography surrounding the drift location and the type of sediment supply. Carbonate particles are derived from either the slope or the platform in slope and toe of slope drifts, very deep contourites have distant siliciclastic sources of sediment supply. The recent discovery of the importance of a large downslope gravitary system along Bahamian slopes suggests frequent interactions between downslope and along‐slope (contour currents) processes. The interlayering of mass flow deposits and contourites at a seismic scale or the presence of surface structures associated with both contour currents and mass flow processes shows that both processes act at the same location. Finally, contour currents have an important impact on the repartition of deep‐water coral mounds. Currents can actively interact with mounds as a nutrient and oxygen supplier or have a passive interaction, with mounds solely being obstacles orienting erosion and deposition.  相似文献   

Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution     

Bernard Barnier  Gurvan Madec  Thierry Penduff  Jean-Marc Molines  Anne-Marie Treguier  Julien Le Sommer  Aike Beckmann  Arne Biastoch  Claus Böning  Joachim Dengg  Corine Derval  Edmée Durand  Sergei Gulev  Elizabeth Remy  Claude Talandier  Sébastien Theetten  Mathew Maltrud  Julie McClean  Beverly De Cuevas 《Ocean Dynamics》2009,59(3):537-537

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Morphodynamique d'une dune sous-marine du détroit du pas de CalaisMorphodynamics of an undersea sandwave of the Dover Straits     

Déborah Idier  Axel Ehrhold  Thierry Garlan 《Comptes Rendus Geoscience》2002,334(15):1079-1085

This paper investigates the dynamics of sandwaves in relationship with tidal currents and weather conditions. The studied sandwaves are located in the Dover Straits and are covered by megaripples. These megaripples have migration speeds of $\text{1 }\text{m}\text{h}{}^{\mathrm{?1}}$ and slopes of 34°, suggesting the potential for avalanches to occur along the flanks of the sandwave. Tidal cycles without reversing currents were observed during stormy weather. Wind-induced currents lead to a unidirectional migration of megaripples and sandwaves. Well-defined areas without megaripples were observed and correlated with an increase in sandwave height. We propose interpretations for understanding sandwave saturation and migration. To cite this article: D. Idier et al., C. R. Geoscience 334 (2002) 1079–1085.  相似文献