Fault interactions in the Sea of Marmara pull-apart (North Anatolian Fault): earthquake clustering and propagating earthquake sequences   总被引：1，自引：0，他引：1  

Nicolas Pondard  Rolando Armijo  Geoffrey C. P. King  Bertrand Meyer  Frédéric Flerit 《Geophysical Journal International》2007,171(3):1185-1197

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The efficiency of kerosene flotation for extraction of chironomid head capsules from lake sediments samples     

Nicolas Rolland  Isabelle Larocque 《Journal of Paleolimnology》2007,37(4):565-572

Kerosene, a grade mineral oil, is commonly used to extract beetles from sediment. Here, the use of kerosene to extract chironomid head capsules was tested on 10 samples from sediment of different lakes, with different organic matter content as measured by loss on ignition, and estimated ages. Our results revealed that this flotation tool is very effective in extracting either full or half chironomid head capsules. The mean extraction efficiency was 89.3 ± 8.0% with an estimated relative abundance error ranging from −1% to 1% for 46 of the 57 identified taxa. Larger chironomids (400–500 μm width), which are often full of sediment particles, have the highest relative abundance error, with a maximum of 4.3% for Corynocera oliveri-type. A canonical correspondence analysis showed that, despite this small bias, samples retrieved with the kerosene flotation do not differ from the whole sample assemblages. These results give us confidence in the use of this flotation technique for chironomid sample preparation.  相似文献   

High-end aerial digital cameras and their impact on the automation and quality of the production workflow     

Nicolas Paparoditis  Jean-Philippe Souchon  Gilles Martinoty  Marc Pierrot-Deseilligny 《ISPRS Journal of Photogrammetry and Remote Sensing》2006,60(6):400

The IGN digital camera project was established in the early 1990s. The first research surveys were carried out in 1996 and the digital camera was first used in production in 2000. In 2004 approximately 10 French departments (accounting for 10% of the territory) were covered with a four-head camera system and since summer 2005 all IGN imagery has been acquired digitally. Nevertheless the camera system is still evolving, with tests on new geometric configurations being continuously undertaken. The progressive integration of the system in IGN production workflows has allowed IGN to keep the system evolving in accordance with production needs. Remaining problems are due to specific camera characteristics such as CCD format, the optical quality of off-the-shelf lenses, and because some production tools are ill-adapted to digital images with a large dynamic range. However, when considering the pros and cons of integrating these images into production lines, the disadvantages are largely balanced by the numerous benefits this technology offers.  相似文献   

Structure and evolution of the eastern Gulf of Aden conjugate margins from seismic reflection data   总被引：2，自引：0，他引：2  

Elia d'Acremont  Sylvie Leroy  Marie-Odile Beslier  Nicolas Bellahsen  Marc Fournier  Cécile Robin  Marcia Maia  Pascal Gente 《Geophysical Journal International》2005,160(3):869-890

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Enhanced trapping of molybdenum by sulfurized marine organic matter of marine origin in Mesozoic limestones and shales   总被引：1，自引：0，他引：1  

Nicolas Tribovillard  Armelle Riboulleau  François Baudin 《Chemical Geology》2004,213(4):385-401

There have been many studies devoted to trace metals and their value in assessing the paleoredox conditions of ancient marine deposition. Among them, molybdenum (Mo) is frequently cited as an effective proxy for sediments and sedimentary rocks. Recently, Helz et al. (Helz, G.R., Miller, C.V., Charnock, J.M., Mosselmans, J.L.W., Pattrick, R.A.D., Garner, C.D., Vaughan, D.J., 1996. Mechanisms of molybdenum removal from the sea and its concentration in black shales: EXAFS evidences. Geochim. Cosmochim. Acta, 60, 3631-3642) and Adelson et al. (Adelson, J. M., Helz, G. R., Miller, C. V., 2001. Reconstructing the rise of recent coastal anoxia; molybdenum in Chesapeake Bay sediments. Geochim. Cosmochim. Acta, 65, 237-252.) suggested that Mo does not behave conservatively in the water column when H₂S reaches a threshold concentration. Above this concentration, a “switch” operates, and Mo is scavenged by forming bonds with metal-rich (notably iron) particles, sulfur-rich organic molecules and pyrite. In this paper, Mo-trapping by sulfur-rich organic matter (OM) in ancient marine deposits is emphasized. The following Mesozoic geological formations were selected for study because of their relatively high concentration of sulfurized OM: the Akkuyu Formation (Turkey), the Calcaires d'Orbagnoux (France) and Kimmeridge Clay (UK) and its timeequivalent in Boulonnais (France), the Kashpir oil shales (Russia), and the La Luna Formation (Venezuela). The sulfur-rich OM is identified by either measured organic-S abundance or kerogen microscope observation. Our results show that Mo is systematically more enriched relative to the other redox-sensitive/sulfide-forming elements studied (U, V, Ni, Cu, Zn, Cr), and Mo enrichment is positively correlated with the amount of sulfurized OM but not with pyrite abundance. These results illuminate the role played by sulfurized OM in geologic-scale Mo capture and retention, but they also underline the role played by reactive iron. Significant OM sulfurization is only possible when reactive iron is limited. Nevertheless, pyrite formation, though limited, could act as an initial Mo trap, prior to Mo uptake by OM that is sulfurized after the pyritization step. In future paleoenvironmental reconstructions, attention must be paid to this enhanced Mo enrichment in the presence of sulfurized organic matter. In such cases, the use of Mo could lead to overestimation of the reducing conditions of the depositional environment.  相似文献   

From rifting to spreading in the eastern Gulf of Aden: a geophysical survey of a young oceanic basin from margin to margin   总被引：1，自引：0，他引：1  

Sylvie Leroy  Pascal Gente  Marc Fournier  Elia d'Acremont  Philippe Patriat  Marie-Odile Beslier  Nicolas Bellahsen  Marcia Maia  Angelina Blais  Julie Perrot  Ali Al-Kathiri  Serge Merkouriev  Jean-Marc Fleury  Pierre-Yves Ruellan  Claude Lepvrier  Philippe Huchon 《地学学报》2004,16(4):185-192

A geophysical survey in the eastern Gulf of Aden, between the Alula–Fartak (52°E) and the Socotra (55°E) transform faults, was carried out during the Encens–Sheba cruise. The conjugate margins of the Gulf are steep, narrow and asymmetric. Asymmetry of the rifting process is highlighted by the conjugate margins (horst and graben in the north and deep basin in the south). Two transfer fault zones separate the margins into three segments, whereas the present‐day Sheba Ridge is divided into two segments by a transform discontinuity. Therefore segmentation of the Sheba Ridge and that of the conjugate margins did coincide during the early stages of oceanic spreading. Extensive magma production is evidenced in the central part of the western segment. Anomaly 5d was identified in the northern and southern parts of the oceanic basin, thus confirming that seafloor spreading in this part of Gulf of Aden started at least 17.6 Ma ago.  相似文献   

Nouvelles données sur la genèse des bauxites à mur karstique du sud-est de la France     

J. Nicolas 《Mineralium Deposita》1968,3(1):18-33

Résumé En de nombreux secteurs du Sud-Est de la France, des brèches séparant la bauxite de son mur, des fossiles et des figures de sédimentation ont été découverts, au sein même de la bauxite: ces éléments prouvent que le minerai ne s'est pas formé au lieu même où on le trouve aujourd'hui. C'est un sédiment qui s'est déposé en milieu aqueux, sous forme de bauxite déjà constituée, après avoir subi un transport, en milieu aqueux également. Une étude pétrographique détaillée montre que ce transport s'est effectué par étapes au cours desquelles la bauxite a continué à subir le phenomène de latéritisation. Les bauxites sont le vestige d'anciens profils de latérite-bauxitique, ferrugineux et alumineux, cuirassés, qui ont été démantelés. La répartition verticale des différents niveaux de bauxite montre qu'ils peuvent, souvent, constituer des profils inversés de latérites primaires dont on peut interpréter le dépôt à la faveur de la théorie de la bio-rhéxistasie de H. Erhart. Les bauxites ont été piégées par des sédiments de nature lithologique et d'âges divers, qui constituent leurs toits et auxquels elles passent progressivement, ce qui confirme leur caractère sédimentaire.

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In numerous areas of the South East of France breccias separating bauxite from its wall, fossiles and sedimentation textures have been discovered right in the bauxite, which prove that the ore has not been formed in the site where found now. It is a sediment which was deposited in aqueous flow. A detailed petrographic study demonstrates that this transportation has been made in different stages, the bauxite continuing to undergo the process of lateritization. The bauxites are the remnants of former profiles of ferruginous and aluminous laterites-bauxites which have been crustified and destroyed. These profiles are former laterite profiles which have been inverted. Their formation may be interpreted through the bio-rhexistasie theory of H. Erhart. The bauxites have been buried by sediments of different ages and composition which form their roofs and into which they pass progressively. This confirms their sedimentary nature.

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The two stage collision of Taiwan: An active orogen     

E. Barrier 《Tectonophysics》1985,115(1-2)

The active Taiwan orogen is the product of a two stage collision, that included first the collision of the Hengchun ridge, an accretionary wedge, with the Chinese continental margin, and second the collision of the Luzon trough and volcanic arc, from the Philippine Sea plate, with the Central Range of Taiwan. During the first stage, the strength of the continental margin induced a decrease of the convergence rate that controlled the final Central Range orientation and induced the second stage of the collision. Taking into account the kinematics of the plate interaction, a reconstruction of the Taiwan collision during the last 4 Ma is proposed.  相似文献   

Structures in podiform chromite from the Maqsad district (Sumail ophiolite,Oman)     

G. Ceuleneer  A. Nicolas 《Mineralium Deposita》1985,20(3):177-184

About 15 chromite bodies have been recognized in the Maqsad area of the Oman ophiolite. The occurrence in this area of three chromite bodies within the cumulate sequence must be integrated into the classification of Cassard et al. (1981) which presently explains only those pods lying in the uppermost mantle sequence (plastically deformed harzburgites and dunites). The occurrence of chromite bodies within the cumulates and the abundance of chromite in the Maqsad area are related to the exceptional magmatic activity and the unusual plastic-flow pattern particular to this area. It was probably a feeding zone along the oceanic spreading center sitting on top of a mantle diapir.  相似文献   

Kinematic interpretation of folds in alpine-type peridotites     

A. Nicolas  F. Boudier 《Tectonophysics》1975,25(3-4)

From a general understanding of the flow mechanisms in alpine-type peridotites, it is possible to describe without ambiguity the general flow regime and its directions in a massif. This result provides the means for an investigation of the origin of the folding in pyroxenitic layers independent of any preconceived theory on folding.The folds are usually isoclinal and of the flexural-flow type as demonstrated by petrofabric studies in hinges. Their axes are always parallel or subparallel to a mineral lineation which in turn is parallel or close to the orientation of the fabric elements defining the flow line. Their axial plane, which usually coincides with the foliation, is parallel to or close to the flow plane. This conclusion, also supported by paragenetic observations, shows that the folds were formed or transposed during the plastic flow responsible for the development of structures (foliation and lineation), textures and preferred mineral orientations. In the case of the Lanzo Massif and a few other Iherzolite massifs, the flow occurred during the intrusion from the mantle. The mapping in Lanzo yields evidence of a large-scale U-shaped fold with a remarkable pattern of mesoscopic folds attached to it: the tight isoclinal folds are restricted to the limbs of the largescale structure, and the open folds locally refolding former isoclinal ones to the hinge area where the angle between the folded pyroxenitic layering and the axial-plane foliation is large. Stereograms of the field structures in this hinge area clearly illustrate the geometric relations mentioned above.This folding, characterized by its axis and axial plane respectively close to the flow line and flow plane, can be explained either by rotation towards the flow line of non-cylindrical-fold axes or by direct formation in a non-plane flow when the flow line is initially contained in the layering or close to it. In this respect, the folding may bring information on the minor flow component, complementary to that given on the major flow component by considering the textures and fabrics. Finally this folding is shown to be ubiquitous in plastically deformed peridotites. It is proposed that these conclusions be extended to other domains submitted to intense non-plane flow.  相似文献