Comment on `Tectono‐sedimentary evolution of lower to middle Miocene halfgraben basins related to an extensional detachment fault (western Crete,Greece)' by M. Seidel,E. Seidel and B. Stöckhert     

Douwe J. J. Van Hinsbergen  Willem‐Jan Zachariasse  Anne R. Fortuin 《地学学报》2008,20(5):414-416

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Fluid-escape features as a precursor of a large sublacustrine sediment slide in Lake Le Bourget, NW Alps, France     

E. Chapron  P. Van Rensbergen  M. De Batist  C. Beck  J. P. Henriet 《地学学报》2004,16(5):305-311

The north‐western corner of Lake Le Bourget is situated along an active fault zone and accommodated a large sediment supply from the Rhone River until the end of the Late Glacial period. On the delta slope, the Holocene sheet drape that covers the largest buried mass wasting deposit (the HDU) shows undulations, small fractures and discontinuities that are attributed to downslope creep. Evidence for episodes of vigorous fluid expulsion is found in association with these discontinuities. All these features are rooted at the top of the HDU and occur along two specific isobaths. These observations indicate a close link between fractures and focused fluid flow. We suggest that focused fluid flow triggered by earthquakes facilitates the formation of small‐scale faults that accommodate part of the downslope movement and eventually link up to form a head‐scarp of a large slide (c. 10⁷ m³).  相似文献   

Multi-wavelength observations of an X-class flare without a coronal mass ejection.     

L.M. Green  S.A. Matthews  L. van Driel-Gesztelyi  L.K. Harra  J.L. Culhane 《Solar physics》2002,205(2):325-339

Developments in our knowledge of coronal mass ejections (CMEs) have shown that many of these transients occur in association with solar flares. On the occasions when there is a common occurrence of the eruption and the flare, it is most likely that the flare is of high intensity and/or long-duration (Burkepile, Hundhausen, and Webb, 1994; Munro et al., 1979; Webb and Hundhausen, 1987). A model for the relationship between the long-duration event and eruption has been developed (Carmichael, 1964; Sturrock, 1966; Hirayama, 1974; Kopp and Pneuman, 1976), but not so for the high-intensity flares and eruptions. This work investigates the magnetic topology changes that occur for a X1.2 GOES classification flare which has no associated CME. It is found that the flare is likely to result from the interaction between two pre-existing loops low in the corona, producing a confined flare. Slightly higher in the corona, a loop is observed which exhibits an outward motion as a result of the reconfiguration during reconnection. The objective of this work is to gain insight on the magnetic topology of the event which is critical in order to determine whether a high-intensity flare is likely to be related to a CME or not.  相似文献   

Predicting Nocturnal Wind and Temperature Profiles Based on External Forcing Parameters   总被引：1，自引：1，他引：0  

J. M. M. Donda  B. J. H. Van de Wiel  F. C. Bosveld  F. Beyrich  G. J. F. van Heijst  H. J. H. Clercx 《Boundary-Layer Meteorology》2013,146(1):103-117

We introduce a simple, physically consistent method to predict nocturnal wind and temperature profiles from external forcing parameters such as the geostrophic wind. As an indicator of the radiative ??forcing?? the net longwave radiative cooling is used as a proxy. Surface fluxes are expressed in terms of these parameters by coupling an Ekman model to a rudimentary surface energy balance. Additionally the model assumes validity of Monin-Obukhov similarity in order to predict near-surface wind and temperature profiles up to a height equal to the Obukhov length. The predictions are validated against an independent dataset that covers 11-years of observations at Cabauw, The Netherlands. It is shown that the characteristic profiles in response to external forcings are well-captured by the conceptual model. For this period the observational climatology is in close agreement with ECMWF re-analysis data. As such, the conceptual model provides an alternative tool to giving a first-order estimate of the nocturnal wind and temperature profile near the surface in cases when advanced numerical or observational infrastructure is not available.  相似文献   

The formation of IIE iron meteorites investigated by the chondrule‐bearing Mont Dieu meteorite          下载免费PDF全文

N. Van Roosbroek  V. Debaille  L. Pittarello  S. Goderis  M. Humayun  L. Hecht  F. Jourdan  M. J. Spicuzza  F. Vanhaecke  Ph. Claeys 《Meteoritics & planetary science》2015,50(7):1173-1196

A 435 kg piece of the Mont Dieu iron meteorite (MD) contains cm‐sized silicate inclusions. Based on the concentration of Ni, Ga, Ge, and Ir (8.59 ± 0.32 wt%, 25.4 ± 0.9 ppm, 61 ± 2 ppm, 7.1 ± 0.4 ppm, respectively) in the metal host, this piece can be classified as a IIE nonmagmatic iron. The silicate inclusions possess a chondritic mineralogy and relict chondrules occur throughout the inclusions. Major element analysis, oxygen isotopic analysis (Δ¹⁷O = 0.71 ± 0.02‰), and mean Fa and Fs molar contents (Fa_{15.7 ± 0.4} and Fs_{14.4 ± 0.5}) indicate that MD originated as an H chondrite. Because of strong similarities with Netschaëvo IIE, MD can be classified in the most primitive subgroup of the IIE sequence. ⁴⁰Ar/³⁹Ar ages of 4536 ± 59 Ma and 4494 ± 95 Ma obtained on pyroxene and plagioclase inclusions show that MD belongs to the old (~4.5 Ga) group of IIE iron meteorites and that it has not been perturbed by any subsequent heating event following its formation. The primitive character of MD sheds light on the nature of its formation process, its thermal history, and the evolution of its parent body.  相似文献   

A search for shocked quartz grains in the Allerød‐Younger Dryas boundary layer          下载免费PDF全文

Annelies Van Hoesel  Wim Z. Hoek  Gillian M. Pennock  Knut Kaiser  Oliver Plümper  Michal Jankowski  Maartje F. Hamers  Norbert Schlaak  Mathias Küster  Alexander V. Andronikov  Martyn R. Drury 《Meteoritics & planetary science》2015,50(3):483-498

The Younger Dryas impact hypothesis suggests that multiple airbursts or extraterrestrial impacts occurring at the end of the Allerød interstadial resulted in the Younger Dryas cold period. So far, no reproducible, diagnostic evidence has, however, been reported. Quartz grains containing planar deformation features (known as shocked quartz grains), are considered a reliable indicator for the occurrence of an extraterrestrial impact when found in a geological setting. Although alleged shocked quartz grains have been reported at a possible Allerød‐Younger Dryas boundary layer in Venezuela, the identification of shocked quartz in this layer is ambiguous. To test whether shocked quartz is indeed present in the proposed impact layer, we investigated the quartz fraction of multiple Allerød‐Younger Dryas boundary layers from Europe and North America, where proposed impact markers have been reported. Grains were analyzed using a combination of light and electron microscopy techniques. All samples contained a variable amount of quartz grains with (sub)planar microstructures, often tectonic deformation lamellae. A total of one quartz grain containing planar deformation features was found in our samples. This shocked quartz grain comes from the Usselo palaeosol at Geldrop Aalsterhut, the Netherlands. Scanning electron microscopy cathodoluminescence imaging and transmission electron microscopy imaging, however, show that the planar deformation features in this grain are healed and thus likely to be older than the Allerød‐Younger Dryas boundary. We suggest that this grain was possibly eroded from an older crater or distal ejecta layer and later redeposited in the European sandbelt. The single shocked quartz grain at this moment thus cannot be used to support the Younger Dryas impact hypothesis.  相似文献   

Systematic documentation of landslide events in Limbe area (Mt Cameroon Volcano,SW Cameroon): geometry,controlling, and triggering factors     

V. B. Che  M. Kervyn  G. G. J. Ernst  P. Trefois  S. Ayonghe  P. Jacobs  E. Van Ranst  C. E. Suh 《Natural Hazards》2011,59(1):47-74

Limbe town and surrounding areas, on the SE foot slopes of the active Mt Cameroon Volcano, have experienced numerous small-scale shallow landslides within the last 20 years. These resulted in the loss of ~30 lives and significant damage to farmland and properties. Landslides and their scars are identified in the field, and their geometry systematically measured to construct a landslide inventory map for the study area. Specific landslides are investigated in detail to identify site-specific controlling and triggering factors. This is to constrain key input parameters and their variability for subsequent susceptibility and risk modeling, for immediate local and regional applications in land-use planning. It will also enable a rapid exploration of remediation strategies that are currently lacking in the SW and NW regions of Cameroon. Typical slides within the study area are small-scale, shallow, translational earth, and debris slides though some rotational earth slides were also documented. The depletion zones have mean widths of 22 m ± 16.7 m and lengths of 25 ± 23 standard deviation. Estimated aerial extents of landslide scars and volume of generated debris range from 10¹ to 10⁴ m² and 2 to 5 × 10⁴ m³, respectively. A key finding is that most slope instabilities within the study area are associated with and appear to be exacerbated by man-made factors such as excavation, anarchical construction, and deforestation of steep slopes. High intensity rainfall notably during localized storms is the principal triggering factor identified so far. The findings from this case study have relevance to understanding some key aspects of locally devastating slope instabilities that commonly occur on intensely weathered steep terrains across subtropical Africa and in the subtropics worldwide and affecting an ever denser and most vulnerable population.  相似文献   

The first ML scale for North of Vietnam     

Le Minh Nguyen  Ting-Li Lin  Yih-Min Wu  Bor-Shouh Huang  Chien-Hsin Chang  Win-Gee Huang  Tu Son Le  Van Toan Dinh 《Journal of Asian Earth Sciences》2011,40(1):279-286

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The Montalet granite, Montagne Noire, France: An Early Permian syn-extensional pluton as evidenced by new U-Th-Pb data on zircon and monazite     

Jean-Charles Poilvet  Marc Poujol  Pavel Pitra  Jean Van Den Driessche  Jean-Louis Paquette 《Comptes Rendus Geoscience》2011,343(7):454-461

Dating the magmatism in the Montagne Noire gneiss dome in the southern French Massif Central is a key point for understanding the Late Palaeozoic evolution of this part of the Variscan belt, which is characterised by compressive tectonics during the Carboniferous and extensional tectonics during Stephanian-Permian times. The Montalet granite crops out in the north-western part of the dome and was first considered as an early syntectonic intrusion related to compressive deformation. More recently, it has been dated at 327 Ma and considered as contemporaneous with the diapiric ascent of the Montagne Noire gneiss dome before the Stephanian-Permian extension. We show that in fact, this pluton was emplaced 294 ± 1 Ma ago and is therefore contemporaneous with the Stephanian-Permian extension. This age is consistent with the interpretation of the Montagne Noire Massif as an extensional gneiss dome.  相似文献   

Pliocene to Recent shallow-water contourite deposits on the shelf and shelf edge off south-western Mallorca, Spain   总被引：2，自引：2，他引：0  

Thomas Philippe Vandorpe  David Van Rooij  Dorrik A. V. Stow  Jean-Pierre Henriet 《Geo-Marine Letters》2011,31(5-6):391-403

This paper presents evidence for the presence of shallow-water contourite drifts on the south-western shelf and shelf edge off Mallorca in water depths between 150 and 275?m. These are called the Mallorca contourite depositional system (CDS). The elongate-mounded shallow-water CDS in this area is ascribed to an offshoot of the Balearic Current, which flows north to south through the Mallorca Channel as part of the overall thermohaline circulation in the Mediterranean Sea. Drift geometry suggests that the north?Csouth current is deflected into an east?Cwest flow pattern by interaction with a marked seafloor bathymetry, associated with major fault displacement. Four seismic units separated by three prominent discontinuities can be identified. The three internal discontinuities are correlated to large-scale basin-wide events: the lower Pliocene revolution (4.2?Ma), the upper Pliocene revolution (2.4?Ma) and the mid-Pleistocene revolution (0.9?Ma). The Plio-Quaternary succession has been deposited on top of a Miocene reef, which serves as an acoustic basement and is affected by a large fault, offsetting the basement on average by 150?m. Marked erosional features throughout and further incision of the Sant Jordi Channel along the basement fault in the Pleistocene deposits indicate stronger currents in this period. The Pleistocene deposits also show a pronounced cyclicity, which is tentatively ascribed to climatic variations and the effects of eustatic sea-level fluctuation over the south-western Mallorca shelf at that time.  相似文献