Apports de la gravimétrie dans la caractérisation des structures éffondrées dans la région de Nebeur (Nord Ouest de la Tunisie)     

Imen Hamdi Nasr  Abdelhamid Ben Salem  Mohamed Hedi Inoubli  Jamel Dhifi  R. Alouani  abdelhak Chaqui  Vincent Perthuisot 《Swiss Journal of Geoscience》2008,101(1):17-27

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Evolution of a mixed siliciclastic‐carbonate deep‐marine system on an unstable margin: The Cretaceous of the Eastern Greater Caucasus,Azerbaijan     

Zoë A. Cumberpatch  Euan L. Soutter  Ian A. Kane  Max Casson  Stephen J. Vincent 《Basin Research》2021,33(1):612-647

Mixed siliciclastic‐carbonate deep‐marine systems (mixed systems) are less documented in the geological record than pure siliciclastic systems. The similarities and differences between these systems are, therefore, poorly understood. A well‐exposed Late Cretaceous mixed system on the northern side of the Eastern Greater Caucasus, Azerbaijan, provides an opportunity to study the interaction between contemporaneous siliciclastic and carbonate deep‐marine deposition. Facies analysis reveals a Cenomanian–early Turonian siliciclastic submarine channel complex that abruptly transitions into a Mid Turonian–Maastrichtian mixed lobe‐dominated succession. The channels are entrenched in lows on the palaeo‐seafloor but are absent 10 km towards the west where an Early Cretaceous submarine landslide complex acted as a topographic barrier to deposition. By the Campanian, this topography was largely healed allowing extensive deposition of the mixed lobe‐dominated succession. Evidence for irregular bathymetry is recorded by opposing palaeoflow indicators and frequent submarine landslides. The overall sequence is interpreted to represent the abrupt transition from Cenomanian–early Turonian siliciclastic progradation to c. Mid Turonian retrogradation, followed by a gradual return to progradation in the Santonian–Maastrichtian. The siliciclastic systems periodically punctuate a more widely extensive calcareous system from the Mid Turonian onwards, resulting in a mixed deep‐marine system. Mixed lobes differ from their siliciclastic counterparts in that they contain both siliciclastic and calcareous depositional elements making determining distal and proximal environments challenging using conventional terminology and complicate palaeogeographic interpretations. Modulation and remobilisation also occur between the two contemporaneous systems making stacking patterns difficult to decipher. The results provide insight into the behaviour of multiple contemporaneous deep‐marine fans, an aspect that is challenging to decipher in non‐mixed systems. The study area is comparable in terms of facies, architectures and the presence of widespread instability to offshore The Gambia, NW Africa, and could form a suitable analogue for mixed deep‐marine systems observed elsewhere.  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   

Crustal Structure of the Tengchong Intra-plate Volcanic Area     

Rongyi Qian  Vincent C. H. Tong 《Surveys in Geophysics》2015,36(5):683-691

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A note on 10Be‐derived mean erosion rates in catchments with heterogeneous lithology: examples from the western Central Andes          下载免费PDF全文

Sebastien Carretier  Vincent Regard  Riccardo Vassallo  Joseph Martinod  Frederic Christophoul  Eric Gayer  Laurence Audin  Christelle Lagane 《地球表面变化过程与地形》2015,40(13):1719-1729

Millennial catchment–mean erosion rates derived from terrestrial cosmogenic nuclides are generally based on the assumption that the lithologies of the parent rock each contain the same proportion of quartz. This is not always true for large catchments, in particular at the edge of mountainous plateaus where quartz‐rich basement rocks may adjoin sedimentary or volcano‐sedimentary rocks with low quartz content. The western Central Andes is an example of this type of situation. Different quartz contents may be taken into account by weighting the TCN production rates in the catchment. We recall the underlying theory and show that weighting the TCN production rate may also lead to bias in the case of a spatial correlation between erosion rate and lithology. We illustrate the difference between weighted and unweighted erosion rates for seven catchments (16 samples) in southern Peru and northern Chile and show variations up to a factor of 2 between both approaches. In this dataset, calculated erosion rates considering only granitoid outcrops are better correlated with catchment mean slopes than those obtained without taking into account the geological heterogeneity of the drained watershed. This dataset analysis demonstrates that weighting erosion rates by relative proportions of quartz is necessary to evaluate the uncertainties for calculated catchment–mean erosion rates and may reveal the correlation with geomorphic parameters. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Assessment of the decadal morphodynamic evolution of a mixed energy inlet using ocean color remote sensing     

Sylvain Capo  Bertrand Lubac  Vincent Marieu  Arthur Robinet  Driss Bru  Philippe Bonneton 《Ocean Dynamics》2014,64(10):1517-1530

A consistent time series of synoptic and high-frequency bathymetric observations is fundamental to improving our understanding and predictive capabilities regarding the morphological behavior of large coastal inlets. Based on satellite observations, an original approach is proposed to characterize the long-term morphological evolution of the Arcachon lagoon inlet and to describe sediment bypassing and breaching mechanisms. The almost 26-year-long remotely sensed data archive used in this study is built from 78 suitable SPOT images (1986–2012) collected in the framework of the KALIDEOS-Littoral program. Bathymetric information is derived from satellite data using a physics-based model. A validation exercise performed on a large bathymetric survey data set (N?=?43,949) demonstrates that the inversion model performs excellently in estimating the depth of mildly to moderately turbid shallow waters. The performance of the model suggests that the minimum requirements are fulfilled to apply the SPOT-derived bathymetry to morphodynamic applications. We demonstrate that high-spatial-resolution multispectral sensors are well adapted to analyzing the morphological evolution of small- (i.e., sand dunes), medium- (i.e., sandbanks and channels), and large- (i.e., the entire inlet-lagoon system) scale sedimentary structures present in coastal inlets. For the first time, the long-term evolution of a flood and ebb-tidal delta is characterized by observations at a seasonal timescale. Finally, migration rates of sedimentary entities are quantified, and fundamental mechanisms driving the sediment transport cross the inlet are confirmed.  相似文献   

Soil-structure interaction on shallow rigid circular foundation: plane SH waves from far-field earthquakes     

Vincent W. Lee  Hao Luo 《地震工程与工程振动(英文版)》2014,13(1):29-45

A closed-form wave function analytic solution of two-dimensional scattering and diffraction of incident plane SH-waves by a fl exible wall on a rigid shallow circular foundation embedded in an elastic half-space is presented. This research generalizes the previous solution by Trifunac in 1972, which tackled only the semi-circular foundation, to arbitrary shallow circular-arc foundation cases, and is thus comparatively more realistic. Ground surface displacement spectra at higher frequencies are also obtained. As an analytical series solution, the accuracy and error analysis of the numerical results are also discussed. It was observed from the results that the rise-to-span ratio of the foundation profi le, frequency of incident waves, and mass ratios of different media(foundation-structure-soil) are the three primary factors that may affect the surface ground motion amplitudes near the structure.  相似文献   

Tephrochronology of the Mont-Dore volcanic Massif (Massif Central,France): new 40Ar/39Ar constraints on the Late Pliocene and Early Pleistocene activity     

Sébastien Nomade  Jean-François Pastre  Pierre Nehlig  Hervé Guillou  Vincent Scao  Stéphane Scaillet 《Bulletin of Volcanology》2014,76(3):1-17

The Mont-Dore Massif (500 km²), the youngest stratovolcano of the French Massif Central, consists of two volcanic edifices: the Guéry and the Sancy. To improve our knowledge of the oldest explosive stages of the Mont-Dore Massif, we studied ⁴⁰Ar/³⁹Ar-dated (through single-grain laser and step-heating experiments) 11 pyroclastic units from the Guéry stratovolcano. We demonstrate that the explosive history of the Guéry can be divided into four cycles of explosive eruption activity between 3.09 and 1.46 Ma (G.I to G.IV). We have also ascertained that deposits associated with the 3.1–3.0-Ma rhyolitic activity, which includes the 5-km³ “Grande Nappe” ignimbrite, are not recorded in the central part of the Mont-Dore Massif. All the pyroclastites found in the left bank of the Dordogne River belong to a later explosive phase (2.86–2.58 Ma, G.II) and were channelled down into valleys or topographic lows where they are currently nested. This later activity also gave rise to most of the volcanic products in the Perrier Plateau (30 km east of the Mont-Dore Massif); three quarters of the volcano-sedimentary sequence (up to 100 m thick) was emplaced within less than 20 ky, associated with several flank collapses in the northeastern part of the Guéry. The age of the “Fournet flora” (2.69?±?0.01 Ma) found within an ash bed belonging to G.II suggests that temperate forests already existed in the French Massif Central before the Pliocene/Pleistocene boundary. The Guéry’s third explosive eruption activity cycle (G.III) lasted between 2.36 and 1.91 Ma. It encompassed the Guéry Lake and Morangie pumice and ash deposits, as well as seven other important events recorded as centimetric ash beds some 60 to 100 km southeast of the Massif in the Velay region. We propose a general tephrochronology for the Mont-Dore stratovolcano covering the last 3.1 My. This chronology is based on 44 ⁴⁰Ar/³⁹Ar-dated events belonging to eight explosive eruption cycles each lasting between 100 and 200 ky. The occurrence of only one pumice deposit in the 800-ky period between 1.9 and 1.1 Ma suggests that volcanic explosive activity was strongly reduced or quiescent.  相似文献   

Diffraction of anti-plane SH waves by a semi-circular cylindrical hill with an inside concentric semi-circular tunnel   总被引：8，自引：3，他引：5  

Vincent W.Lee  罗昊  梁建文 《地震工程与工程振动(英文版)》2004,3(2):249-262

A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semicylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the cylindrical wave functions expansion method. The solution is reduced to solving a set of infinite linear algebraic equations. Fourier expansion theorem with the form of complex exponential function and cosine function is used. Numerical solutions are obtained by truncation of the infinite equations. The accuracy of the presented numerical results is carefully verified.  相似文献   

On the transition from strombolian to fountaining activity: a thermal energy-based driver     

Maxime Bombrun  Letizia Spampinato  Andrew Harris  Vincent Barra  Tommaso Caltabiano 《Bulletin of Volcanology》2016,78(2):15

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