Failles normales Paléocène à Lutétien en zone sud-pyrénéenne (Aragon,Espagne) et flexuration de la plaque ibérique     

Yves Hervouët  Nicolas Espurt  Damien Dhont 《Comptes Rendus Geoscience》2005,337(3):385-392

Close to the South Pyrenean thrust front, synsedimentary normal faults develop in the ‘Garumnian’ continental deposits (Maastrichtian to Palaeocene) and in the carbonate platform during the Lutetian. During the Lutetian, this deformation is accompanied by a change in the sedimentation characterized by the deposit of two series of laminated limestones associated to monogenetic breccias. These normal faults would have formed at the bending of the Iberian plate subducting under Europe. They may also be considered as the starting point for the megaturbidites that deposited further north in the Eocene turbiditic basin. To cite this article: Y. Hervouët et al., C. R. Geoscience 337 (2005).  相似文献   

La branche orientale de l'arc de Chypre. Morphostructure d'une frontière de plaques d'après les résultats de la campagne BLAC (2003)     

Jean Benkhelil  Mazhar Bayerly  Stéphane Branchoux  Thierry Courp  Eliane Gonthier  Christian Hübscher  Agnès Maillard  Elias Tahchi 《Comptes Rendus Geoscience》2005,337(12):1075-1083

The eastern bend of the Cyprus Arc, at the transition between the submerged Mediterranean subduction and the onshore fault zones that underline the Eurasian, African and Arabic plates boundaries is a submarine feature undergoing a complex tectonic deformation. The BLAC marine geophysical survey helps to better assess the type of the deformation that affects the Messinian to Quaternary sediments along this plate boundary. The deformation, focussed between two tectonic corridors, displays compressive and transpressive features in the central part, becoming thrusting when moving westward in connection with the Cyprus accretionnary wedge. The northeastern end of this submarine range connects with the Latakia Ridge, which is, together with its continental extension, under a tensional tectonic regime. To cite this article: J. Benkhelil et al., C. R. Geoscience 337 (2005).  相似文献   

Sm–Nd isotopic compositions as a proxy for magmatic processes during the Neoproterozoic of the southern Brazilian shield     

Maria do Carmo P. Gastal  Jean Michel Lafon  Lo Afraneo Hartmann  Edinei Koester 《Journal of South American Earth Sciences》2005,18(3-4):255-276

Combined analyses of Nd isotopes from a wide range of Neoarchaean–Cretaceous igneous rocks provides a proxy to study magmatic processes and the evolution of the lithosphere. The main igneous associations include the Neoproterozoic granitoids from the southern Brazilian shield, which were formed during two tectonothermal events of the Brasiliano cycle: the São Gabriel accretionary orogeny (900–700 Ma) and the Dom Feliciano collisional orogeny (660–550 Ma). Rocks related to the formation of the São Gabriel arc (900–700 Ma) mainly have a depleted juvenile signature. For the Neoproterozoic collisional event, the petrogenetic discussion focuses on two old crustal segments and three types of mantle components. However, no depleted juvenile material was involved in the formation of the Dom Feliciano collisional belt (800–550 Ma), which implies an ensialic environment for the Dom Feliciano orogeny. In the western Neoproterozoic foreland, records of a Neoarchaean lower crust predominate, whereas a Paleoproterozoic crust does in the eastern Dom Feliciano belt. The western foreland includes two amalgamated geotectonic domains, the São Gabriel arc and Taquarembó block. In the collisional belt, the old crust was intensely reworked during the São Gabriel event. In addition to the Neoproterozoic subduction-processed subcontinental lithosphere (São Gariel arc), we recognize two old enriched mantle components, which also are identified in the Paleoproterozoic intraplate tholeiites from Uruguay and the Cretaceous potassic suites from eastern Paraguay. One end member displays the prominent influence of Trans-Amazonian (2.3–2.0 Ga) or older subduction events, whereas the other can be interpreted as a reenrichment of the first during the latest Trans-Amazonian collisional or younger events. This reenriched mantle is documented in late Neoproterozoic suites from the western foreland (605–550 Ma) and younger suites from the eastern collisional belt (600–580 Ma). The other enriched mantle component with an old subduction signature, however, appears only in older rocks of the collisional belt (800–600 Ma). The participation of the subduction-related Brasiliano mantle as an end member of binary mixing occurred in some early Neoproterozoic suites (605–580 Ma) from the western foreland, but the contribution of the Neoarchaean lower crust increased near the late igneous event (575–550 Ma).  相似文献   

Nouvelle interprétation tectonique de la montagne Sainte-Victoire (Provence,France)     

Jean Ricour  Ion Argyriadis  Raymond Monteau 《Comptes Rendus Geoscience》2005,337(14):1277-1283

The explanation normally given for the tectonics of Sainte-Victoire Mountain, a dozen kilometres east of Aix-en-Provence, to the north of the limestone Provence, is incorrect. To the east, the morphology of the Sainte-Victoire is subdued, whereas to the west, before the mountain breaks savagely, the morphology is that of a young mountain as appears in Alpine landscapes. This unusual aspect in the region and the large subvertical faults with vertically striated surfaces that mark the massif to the south and to the west, induce the idea of strong vertical uplifts and caste doubt on the tectonic interpretation given in 1962 by Corroy et al. According to those authors, the Sainte-Victoire is a unit of Jurassic and Cretaceous formations overthrusting 1800 m to the south conglomerates of the Late Cretaceous or Palaeocene. New observations about the conglomerate transgression over the Jurassic and Cretaceous beds, and about the faults around and on the massif do not give evidence of an overthrusting but, on the contrary, induce the idea of a uplift, perhaps still active, in the form of a ‘piano key’ inclined to the northeast. To cite this article: J. Ricour et al., C. R. Geoscience 337 (2005).  相似文献   

Describing the Geometry of 3D Fracture Systems by Correcting for Linear Sampling Bias   总被引：1，自引：0，他引：1  

Olivier Fouché  Jean Diebolt 《Mathematical Geology》2004,36(1):33-63

Analyzing the geometric bias inherent to linear sampling of natural fracture systems is a prerequisite to any attempt of structural modeling. In this paper, the basic parameters of 1D-sampled fracture sets, i.e. orientation, density, and size, are interpreted in terms of geometric probabilities. Weighting factors are derived which allow the 3D restitution of a moderately variable fracture network from a single borehole. The proposed method is applied to well core data from a granitic rock mass, and the efficiency of the proposed corrections is illustrated through random disc simulations tested by virtual scanlines analogous to the real borehole. This approach aims to reduce the prospecting effort in exploration, and to criticize assumption of structural homogeneity by rigorously comparing fracture populations collected from nonparallel boreholes. Then a parametric study of fracture size is performed and a range of mean size leading to fully connected networks is identified.  相似文献   

Normal-mode theory of a rotating earth model using a Lagrangian perturbation of a spherical model of reference     

Yves Rogister  Michael G. Rochester 《Geophysical Journal International》2004,159(3):874-908

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Seismic singularities at upper-mantle phase transitions: a site percolation model     

Felix J. Herrmann  Yves Bernabé 《Geophysical Journal International》2004,159(3):949-960

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Estimation of PM20 emissions by wind erosion: main sources of uncertainties     

Stephane C. Alfaro  Jean Louis Rajot  William Nickling   《Geomorphology》2004,59(1-4):63

The physics of the two processes (saltation and sandblasting) leading to fine mineral dust emissions by wind erosion in arid or semi-arid areas has been detailed and modeled. The combination of these two models has led to a physically explicit Dust Production Model (DPM). In this work, sensitivity tests are performed with the DPM to determine the nature of the main soil parameters that control dust emissions by sandblasting. It is found that the soil roughness length and the dry size distribution of the soil aggregates constituting the loose wind erodible fraction of the topsoil have the greatest influence on the soil potential for mineral dust production. Contrary to what is often assumed, soil texture is not a relevant parameter.In the light of these new findings, results of vertical flux measurements performed over a wide variety of sources in Niger and the US south west (14 soils) have been reanalyzed. Results show (1) that for the tested soils the DPM, and hence sandblasting, explain all dust emissions, and (2) that 13 of the 14 soils that had been selected a priori for their high potential for dust emissions contained a fine soil-aggregate component. This is consistent with the sensitivity tests indicating that the presence of such a component could enhance dust emissions by one order of magnitude. Finally, it can be concluded that most of the apparent scatter in the experimental results was in large part due to an inappropriate choice of soil parameters to interpret them.  相似文献   

Modelling the spatial distribution of present-day deformation in Nepal: how cylindrical is the Main Himalayan Thrust in Nepal?   总被引：1，自引：0，他引：1  

Antoine Berger  François Jouanne  Riad Hassani  Jean Louis Mugnier 《Geophysical Journal International》2004,156(1):94-114

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An enhanced method for source parameter imaging of magnetic data collected for mineral exploration     

Richard S. Smith  Ahmed Salem  Jean Lemieux 《Geophysical Prospecting》2005,53(5):655-665

We have developed a method for imaging magnetic data collected for mineral exploration to yield the following structural information: depth, model type (structural index) and susceptibility. The active nature of mineral exploration data requires we derive the structural information from a robust quantity: we propose that the first‐ or second‐order analytic‐signal amplitude is suitably stable. The procedure is to normalize the analytic‐signal amplitude by the peak value and then use non‐linear inversion to estimate the depth and the structural index for each anomaly. In our field example, different results are obtained depending on whether we inverted for the first‐ or second‐order analytic‐signal amplitude. This is probably because the two‐dimensional contact, thin sheet or horizontal cylinder models we have assumed are not appropriate. In cases such as these, when our model assumptions are not correct, the results should not be interpreted quantitatively, but they might be useful for giving a qualitative indication of how the structure might vary. With a priori information, it is possible to assume a model type (i.e. set the structural index) and generate estimates of the depth and susceptibility. These data can then be gridded and imaged. If a contact is assumed, the susceptibility contrast is estimated; for the dike model, the susceptibility‐thickness is estimated; for the horizontal cylinder, the susceptibility‐area is estimated. To emphasize that the results are dependent on our assumed model, we advocate prefixing any derived quantity by the term ‘apparent’.  相似文献