Un réseau fluviatile d'âge Burdigalien terminal dans le Sud-Est de la France : remplissage,extension, âge,implications     

David Besson  Olivier Parize  Jean-Loup Rubino  Jean-Pierre Aguilar  Marie-Pierre Aubry  Bernard Beaudoin  William A. Berggren  Georges Clauzon  Philippe Crumeyrolle  Yann Dexcoté  Nicolas Fiet  Silvia Iaccarino  Gonzalo Jiménez-Moreno  Cécile Laporte-Galaa  Jacques Michaux  Katharina von Salis  Jean-Pierre Suc  Jean-Yves Reynaud  Roland Wernli 《Comptes Rendus Geoscience》2005,337(12):1045-1054

An integrated study combining facies analysis, multiple group biostratigraphy, identification of depositional sequences and mapping has been conducted on the Miocene Molasse Basin of the external Alps (southeastern France). The filling of the basin is described as resulting from a succession of fluvial incisions subsequently filled during marine transgressions. The major incision is dated as Latest Burdigalian and the major transgression as Langhian. This revised interpretation of the Miocene physiographic evolution of the Molasse Basin implies a re-examination of previous stratigraphic correlations within the basin. To cite this article: D. Besson et al., C. R. Geoscience 337 (2005).  相似文献   

Glacier Distribution in the Alps: Statistical Modelling of Altitude and Aspect     

Ian S. Evans 《Geografiska Annaler: Series A, Physical Geography》2006,88(2):115-133

Mass balance of glaciers in mountain areas varies not only with altitude and regional position but also with aspect, gradient, glacier size, glacier type and detailed topographic position. These factors are combined here in models of how glacier altitude varies, tested with data for the Alps edited from the World Glacier Inventory. An overall northward tendency in glacier numbers (toward 005 ± 4°) and lower altitudes (013 ± 5°) is maintained across a range of glacier sizes, types, altitudes and the major divisions of the Alps. Variation with aspect of glacier altitude (and, by implication, of glacier balance) in the Alps is essentially unimodal, and north‐facing glaciers average 220 m lower in middle altitude than south‐facing: 148 m in the Western Alps, 232 m in the West‐central, 252 m in the East‐central, and 268 m in the Eastern Alps. For smaller subdivisions, confidence intervals on estimates are broader and many differences lack statistical significance. Contrasts are greater in the higher massifs, with greater relief, and lower in cloudy, windward areas. There are small windrelated tendencies east of north along the northern and western fringes, but trends across space are weak: position is thus treated by subdivision into districts and groups. Mid‐altitude averages 2891 m overall and varies from 2552 to 3127 m for 27 glacier districts, and from 2124 to 3209 m for 103 glacier groups. Glacier mid‐altitude varies also with glacier form, nourishment, height range and area, which account for over two‐thirds of variance in combined models.  相似文献   

Sur l’origine karstique et l’age plio-quaternaire des accumulations bréchiques dites ?brèches marines et paléocènes? d’Amélie-les-Bains (Pyrénées-Orientales, France)     

Joseph Canerot  Bernard Laumonier  Thierry Baudin 《Eclogae Geologicae Helvetiae》2006,99(1):49-64

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Carbonate weathering rates in the Jura Mountains, France-The influence of vegetation     

Senlin LU Longyi SHAO Minghong WU Zheng JIAO JONES T. P. 《中国地球化学学报》2006,25(B08):2-2

In order to better understand what controls carbonate weathering rates, we report results from the Jura Mountains （East France）, an area exclusively composed of carbonate rocks. This region presents an altitude gradient increasing from 250 m to 1300 m. Over the basin, this gradient generates climatic contrasts of 5℃ and a runoff three times higher in altitude. This place offers a good opportunity for understanding the controlling factors of carbonate weathering. Contrary to thermodynamic calculations that predict the highest concentrations at low temperature, we observe that carbonate dissolution is two times higher at low elevation than in the mountains. This observation can only be explained by a variation in soil pCO2. In order to better constrain the observed variation in cation contents （principally Ca and Mg） of rivers, we used the ASPECTS ecological model （Rasse et al., 2001）. Based on both hourly climatic data, vegetation type and soil type, ASPECTS may reconstruct pCO2 in soil.  相似文献   

Benthic foraminiferal assemblages of late Aptian-early Albian black shale intervals in the Vocontian Basin, SE France   总被引：1，自引：0，他引：1  

J. Erbachen  W. Gerth  G. Schmiedl  Ch. Hemleben 《Cretaceous Research》1998,19(6):805-826

Benthic foraminiferal assemblages were analyzed from three black shale intervals in the upper Aptain to lower Albian of the Vocontian Basin, SE France based on Q-mode principal component analyses. Variations in the distribution patterns of benthic foraminifera around these events suggest differences in the origin of the black shales. Differences between faunas of bioturbated marly and laminated black shale facies have been observed in the Niveau Paquier, Oceanic Anoxic Event (OAE) 1b and Niveau Leenhardt. Here, the faunal composition and plankton/benthos ratios suggest eutrophic conditions during the deposition of organic-rich sediments leading to black shales. No major variations have been observed in black shales of the upper Aptain Niveau Jacob. Benthic assemblages and low plankton/benthos ratios indicate mesotrophic conditions. Third order sea-level changes are believed to control mainly the origin of the investigated black shale levels.  相似文献   

Local erosion rates versus active tectonics: cosmic ray exposure modelling in Provence (south-east France)     

Lionel Siame  Olivier Bellier  Rgis Braucher  Michel Sbrier  Marc Cushing  Didier Bourls  Bruno Hamelin  Emmanuel Baroux  Beatrice de Voogd  Grant Raisbeck  Franoise Yiou 《Earth and Planetary Science Letters》2004,220(3-4):345-364

Over the past decade, in situ-produced cosmogenic nuclides have revolutionised the study of landscape evolution. In particular, numerous studies have demonstrated that, in active tectonic settings, cosmic ray exposure dating of deformed or displaced geomorphic features makes it possible to quantify long-term deformation rates. In western European countries, erosion due to climatically driven processes and human activities is probably the factor that most limits the accuracy of exposure ages and landscape modification rates. In this study, we present the results of a depth-profiling technique applied to alluvial terraces located along the Rhône and the Moyenne Durance rivers. The expected decrease with depth of the measured ¹⁰Be concentrations has been modelled using a χ² inversion method in order to constrain the exposure history of the alluvial sediments. The results suggest that: (1) over the Quaternary, the local surface erosion rates including both regional uplift and climatically driven processes acting on landforms are on the order of 30 m/Myr in southeastern France, and (2) providing a fairly good bracketing of the exposure age, the modelled abandonment age of alluvial terraces affected by the Moyenne Durance Fault allows estimating incision rates, comparing the alluvial terrace elevations with topographic river profiles, and a minimum vertical slip rate value of roughly 0.02 mm/yr for the southern segment of the Moyenne Durance Fault.  相似文献   

Première datation UPb des orthogneiss œillés de la zone axiale de la Montagne noire (Sud du Massif central) : nouveaux témoins du magmatisme ordovicien dans la chaı̂ne Varisque     

Françoise Roger  Jean-Patrick Respaut  Maurice Brunel  Philippe Matte  Jean-Louis Paquette 《Comptes Rendus Geoscience》2004,336(1):19-28

We present new U–Pb results on felsic Augen orthogneisses from the Axial Zone of the Montagne Noire (French Massif Central). The data indicate Ordovician ages, 456±3 and 450±6 Ma for two samples collected at ‘Pont-de-Larn’ and ‘Gorges d'Héric’, respectively. These ages are interpreted as the igneous emplacement age of the granitic protolith. To cite this article: F. Roger et al., C. R. Geoscience 336 (2004).  相似文献   

Salt tectonics,a controlling factor on the development of the Marseilles and Grand-Rhone sedimentary ridges,Gulf of Lions,western Mediterranean Sea     

Antonio Tadeu dos Reis  Christian Gorini  Alain Mauffret  Wiktor Weibull 《Comptes Rendus Geoscience》2004,336(2):143-150

The Marseilles (also called Marseilles/Planier) and Grand Rhone sedimentary ridges, offshore the Gulf of Lions, western Mediterranean Sea, are generated by sediment spillover funnelled by the Marseilles and Grand-Rhone canyons, respectively. We show that the Marseilles and Grand-Rhone canyon directions are tectonically conditioned by Plio-Quaternary salt-induced sea-floor relief. Overburden extension in the area created an assemblage of listric faults running parallel to the strike of the continental margin. This salt-induced topography resulted in accentuated fault scarps impacting the sea-floor morphology and forcing submarine valleys to deflect to the east. Gravity-induced extension equally influenced the morphological pattern of the valley overbanking deposits. Sediment spillover occurred on both flanks of the canyons, but because active faulting generated space accommodation for overflow deposits, it inhibited the development of typical levee morphology along the canyons' left flanks. To cite this article: A.T. dos Reis, C. R. Geoscience 336 (2004).  相似文献   

Alimentation et origine de la salinité de la source sous-marine de Port-Miou (Marseille–Cassis). Principale émergence d'un réseau karstique hérité du Messinien     

Bernard Blavoux  Éric Gilli  Claude Rousset 《Comptes Rendus Geoscience》2004,336(6):523-533

(Marseille–Cassis–Bouches–du-Rhône). The salinity of the karstic submarine spring of Port-Miou has sometimes been attributed to the leaching of continental evaporites. Our recent chemical and isotopic analyses indicate a simple mixing between fresh karstic water and seawater. In the main gallery, the contamination by seawater, still present up to 2.2 km from the entrance at a depth of 147 m below the sea level, forces us to think about a general geometry that allows mixing of waters, at a great depth, in the karstic system. The measurements of the discharge of the spring indicate an excess of water compared with its supposed watershed, whereas a succinct evaluation of the aquifers of the Lower Provence indicates a deficit of discharge. Consequently, it seems possible that parts of the calcareous areas of the Lower Provence feed the springs of Port-Miou with a total catchment area of 1200 km². This deep and large karstic system was probably installed during the Messinian period, when the important lowering of the level of the Mediterranean Sea provoked an important gradient between Provence and the seashore. To cite this article: B. Blavoux et al., C. R. Geoscience 336 (2004).  相似文献   

Metastable staurolite–cordierite assemblage of the Bossòst dome: Late Variscan decompression and polyphase metamorphism in the Axial Zone of the central Pyrenees     

Jochen E. Mezger  Cees W. Passchier  Jean-Luc Régnier 《Comptes Rendus Geoscience》2004,336(9):827-837

A kilometre-scale shear zone is recognized in the Cambro–Ordovician schist of the Bossòst dome, a Variscan metamorphic and structural dome in the Axial Zone of the central Pyrenees. Non-coaxial deformation is recorded by rotated garnet and staurolite porphyroblasts following regional metamorphism M₁, while coaxial conditions prevailed during later contact metamorphic M₂ growth of andalusite and cordierite. Mineral compositions and bulk rock analyses show that garnet–staurolite–andalusite–cordierite assemblages are significantly enriched in Mg and Mn over the garnet–staurolite assemblage, which lacks sufficient Mg for cordierite to form. The garnet–staurolite assemblage preserves conditions during M₁, estimated by AFM diagrams and P–T pseudosections to be 5.5 kbar and 580 °C, respectively. Pseudosections also indicate that staurolite is not a stable phase in cordierite–andalusite assemblages of M₂, suggesting polyphase metamorphism and decompression along a clockwise P–T path for the staurolite–cordierite–andalusite assemblages. This concurs with proposed extensional tectonics along the regional shear zone. To cite this article: J.E. Mezger et al., C. R. Geoscience 336 (2004).  相似文献