Enigmatic Microorganisms and Life in Extreme Environments     

Warwick F. Vincent 《Journal of Paleolimnology》2002,27(2):285-286

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Digital Surface Modelling by Airborne Laser Scanning and Digital Photogrammetry for Glacier Monitoring   总被引：2，自引：0，他引：2  

Emmanuel P. Baltsavias  Etienne Favey  reas Bauder  Hermann Bosch  & Maria Pateraki 《The Photogrammetric Record》2001,17(98):243-273

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The Sis palaeovalley: a record of proximal fluvial sedimentation and drainage basin development in response to Pyrenean mountain building   总被引：2，自引：0，他引：2  

Stephen J. Vincent 《Sedimentology》2001,48(6):1235-1276

The Sis conglomerate body represents the Middle Eocene to Oligocene transfer‐zone trunk palaeovalley fill of the Sis fluvial system, a drainage system established within the Pyrenees during Late Palaeocene times. The spatial stability of the fluvial transfer zone (active for at least 38 My), and hence the longevity of its aggradational palaeovalley component (>19·5 My), was controlled by its location between long‐lived pre‐existing structures. Coarse‐grained fluvial facies dominate the palaeovalley fill, with alluvial fan facies shed from its defining marginal structures. The detailed sedimentology of very proximal fluvial facies deposited within the dominantly erosional realm of an active mountain belt has rarely been documented before because of their poor preservation potential. The Sis conglomerate body contains a robust internal stratigraphy with stratigraphic units defined by distinct bounding surfaces, across which there are pronounced changes in facies and provenance. These mark the reorganization of the headward portions of the Sis fluvial system during the evolution of the Pyrenean Axial Zone antiformal stack. Major changes in discharge resulted, demonstrating the highly variable nature of even mountain belt‐scale fluvial systems when viewed on timescales of several to tens of millions of years. Provenance details indicate that initial unroofing of Hercynian granitoids, situated within the Pyrenean Axial Zone, occurred around 54·5 Ma (early Ypresian) immediately before the first significant exhumation event within the drainage basin of the Sis fluvial system. This is earlier than previously constrained by apatite fission track studies. Rock uplift accelerated in the Lutetian and Bartonian with the initial aggradation of the palaeovalley fill (the Cajigar and Cornudella Formations and Sis One and Two Members). This became marked in the Priabonian (Sis Three and Four Members), with significant activity on local structures including the Morreres backthrust. An increase in basement‐derived clasts and a headwater decapitation event also indicate pronounced Axial Zone antiformal stack development at this time. Axial Zone development intensified further in the Oligocene with the deposition of the Collegats Formation and the switch in the main depositional loci of the system from the Tremp‐Graus thrust‐sheet‐top basin to the Ebro Basin to the south.  相似文献   

The 1928–1929 eruption of Kammourta volcano — evidence of tectono-magmatic activity in the Manda-Inakir rift and comparison with the Asal Rift,Afar depression,Republic of Djibuti     

J Audin  P J Vellutini  C Coulon  P Piguet  J Vincent 《Bulletin of Volcanology》1990,52(7):551-561

There are two rifts zones in the Republic of Djibuti: the active Asal rift (birthplace of the Ardoukôba basaltic volcano in 1978) and the poorly known Manda-Inakir rift described here. The most recent volcanic event in the Manda-Inakir rift was the formation of the Kammourta basaltic cone, probably in 1928, accompanied by strong seismic activity. This historic eruption and related tectonic features show that the Manda-Inakir rift, like Asal, is presently active. The Kammourta basalt, of transitional alkaline type, belongs to the Manda-Inakir differentiated series, which ranges from basalt to rhyolite. In contrast, volcanic rocks of the Asal rift are entirely transitional tholeiitic basalt. The differences in magmatic affinity and tectonics between these two rift zones reflect the more advanced evolution of rifting in the Asal zone than in Manda-Inakir.  相似文献   

Jason-1 Geophysical Performance Evaluation     

P. Vincent  S. D. Desai  J. Dorandeu  M. Ablain  B. Soussi  P. S. Callahan  B. J. Haines 《Marine Geodesy》2003,26(3):167-186

The Jason-1 satellite was launched on 7 December 2001 with the primary objective of continuing the high accuracy time series of altimeter measurements that began with the TOPEX/Poseidon mission in 1992. To achieve this goal, it is necessary to validate the performance of the Jason-1 measurement system, and to verify that its error budget is at least at the same level as that of the TOPEX/Poseidon mission. The article reviews the main components of the Jason-1 altimetric error budget from instrument characterization to the geophysical use of the data. Using the Interim Geophysical Data Records (16DR) that were distributed to the Jason-1 Science Working Team during the verification phase of the mission, it is shown that the Jason-1 mission is performing well enough to continue studies of the large-scale features of the ocean, and especially to continue time series of mean sea-level variations with an accuracy comparable to TOPEX/Poseidon.  相似文献   

The Jason-1 Mission   总被引：1，自引：2，他引：1  

Yves M  nard  Lee-Lueng Fu  P. Escudier  F. Parisot  J. Perbos  P. Vincent  S. Desai  B. Haines  G. Kunstmann 《Marine Geodesy》2003,26(3):131-146

On December 7, 2001, the Jason-1 satellite was successfully launched by a Boeing Delta II rocket from the Vandenberg site in California, USA. Its main mission was to maintain the high accuracy altimeter measurements, provided since 1992 by TOPEX/Poseidon (T/P), ensuring continuity in observing and monitoring the ocean for intraseasonal to interannual changes, mean sea level, tides, and so forth. Despite four times less mass and power, the Jason-1 system has been designed to have the same performances as T/P, measuring sea surface topography at the centimeter level. This new Centre National d'Etudes Spatiales/National Aeronautics and Space Administration (CNES/NASA) mission also provides near real-time data for sea state and ocean forecast. The first 10 months of the Jason mission were dedicated to the verification of the system performance and cross-calibration with T/P measurements. A complete CALVAL plan was conducted by the Science and Project Teams of the mission based on in situ and regional experiments, global statistical approaches, and multisatellite comparisons, taking advantage of the T/P-Jason overlap during the first months of the mission. CALVAL and first science results showed that the Jason-1 performances were compliant with prelaunch specifications. This was a needed preamble before starting the routine phase of the mission in July 2003 with generation and distribution of validated geophysical data records to the whole user community.  相似文献   

Correcting wind‐induced bias in solid precipitation measurements in case of limited and uncertain data     

Vincent Fortin  Charles Therrien  François Anctil 《水文研究》2008,22(17):3393-3402

Automatic precipitation gauges tend to underestimate solid precipitation in the presence of wind. Loss as a function of wind speed is typically evaluated by comparing the gauge with a more accurate measurement made using a double‐fence intercomparison reference gauge (DFIR). For small precipitation events, small errors in the observations can induce large errors in the ‘catch’ ratio, i.e. the ratio of the automatic gauge measurement to the DFIR observation. For this reason, precipitation events of less than 3 mm are typically discarded before performing the regression analysis. This can mean discarding more than 90% of the observations. This paper shows how the method of weighted least squares can be used to perform a regression analysis that can take into account the whole sample to provide a more accurate estimation of the relationship between the catch ratio and the wind speed. This methodology is then used to obtain an adjustment curve for a shielded Geonor T‐200B precipitation gauge in Northern Québec. Copyright © 2008 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada.  相似文献   

Particle size and mineralogical composition of inorganic colloids in waters draining the adit of an abandoned mine,Goesdorf, Luxembourg     

Montserrat Filella  Vincent Chanudet  Simon Philippo  François Quentel 《Applied Geochemistry》2009

Particle size distributions and the mineralogy of inorganic colloids in waters draining the adit of an abandoned mine (Goesdorf, Luxembourg) were quantified by single particle counting based on light scattering (100 nm–2 μm) combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction. This water system was chosen as a surrogate for groundwaters. The dependence of the colloid number concentration on colloid diameters can be described by a power-law distribution in all cases. Power-law slopes ranged from −3.30 to −4.44, depending on water ionic strength and flow conditions. The same main mineral types were found in the different samples: 2:1 phyllosilicates (illite and mica), chlorite, feldspars (albite and orthoclase), calcite and quartz; with a variable number of Fe oxide particles. The colloid mineralogical composition closely resembles the composition of the parent rock. Spatial variations in the structure and composition of the rock in contact with the waters, i.e. fissured rock versus shear joints, are reflected in the colloid composition. The properties of the study colloids, as well as the processes influencing them, can be considered as representative of the colloids present in groundwaters.  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   

Formation of magnesium‐smectite during lacustrine carbonates early diagenesis: Study case of the volcanic crater lake Dziani Dzaha (Mayotte – Indian Ocean)     

Vincent P. Milesi  Didier Jzquel  Mathieu Debure  Pierre Cadeau  Franois Guyot  Grard Sarazin  Francis Claret  Emmanuelle Vennin  Carine Chaduteau  Aurlien Virgone  Eric C. Gaucher  Magali Ader 《Sedimentology》2019,66(3):983-1001

The volcanic crater lake of Dziani Dzaha in Mayotte is studied to constrain the geochemical settings and the diagenetic processes at the origin of Mg‐phyllosilicates associated with carbonate rocks. The Dziani Dzaha is characterized by intense primary productivity, volcanic gases bubbling in three locations and a volcanic catchment of phonolitic/alkaline composition. The lake water has an alkalinity of ca 0·2 mol l^?1 and pH values of ca 9·3. Cores of the lake sediments reaching up to one metre in length were collected and studied by means of carbon–hydrogen–nitrogen elemental analyzer, X‐ray fluorescence spectrometry and X‐ray powder diffraction. In surface sediments, the content of total organic carbon reaches up to 20 weight %. The mineral content consists of aragonite and hydromagnesite with minor amounts of alkaline feldspar and clinopyroxene from the volcanic catchment. Below 30 cm depth, X‐ray diffraction analyses of the <2 μm clay fraction indicate the presence of a saponite‐like mineral, a Mg‐rich smectite. The saponite‐like mineral accumulates at depth to reach up to ca 30 weight %, concurrent with a decrease of the contents of hydromagnesite and organic matter. Thermodynamic considerations and mineral assemblages suggest that the evolution of the sediment composition resulted from early diagenetic reactions. The formation of the saponite‐like mineral instead of Al‐free Mg‐silicates resulted from high aluminum availability, which is favoured in restricted lacustrine environments hosted in alkaline volcanic terrains commonly emplaced during early stages of continental rifting. Supersaturation of the lake water relative to saponite is especially due to high pH values, themselves derived from high primary productivity. This suggests that a genetic link may exist between saponite and the development of organic‐rich carbonate rocks, which may be fuelled by the input of CO₂‐rich volcanic gases. This provides novel insights into the composition and formation of saponite‐rich deposits under a specific geodynamic context such as the Cretaceous South Atlantic carbonate reservoirs.  相似文献